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The technique of swing bowling is used in the sport of cricket to gain an advantage over the batter, and improve a team's chance of winning a match. The current best practice for swing bowling is based on anecdotal evidence, with little consensus on the optimal strategies. Bowling technique, the condition of the ball and atmospheric conditions are all considered important for swing, yet there is little quantification of these factors even in elite cricket. Previous experimental studies have not provided a description of swing that aligns with measurements of on-field swing made using ball-tracking technology. This research looks to provide clarity on the physical mechanisms behind swing bowling for new and used cricket balls. Appropriate boundary conditions are measured in field tests, and applied to experiments so that results represent on-field swing. Wind tunnel tests are performed which measure the changes in the aerodynamic force coefficient, CF. The relevant findings are related back to cricket through tools for use in the professional game. For new cricket balls, it is shown that conventional swing has a magnitude of 0.3 < C_F < 0.4, caused by the separation asymmetry between a laminar boundary layer and a reattached boundary layer. High Reynolds Number flow over 190,000, turbulence intensity above 0.6% and geometric features are all shown to inhibit conventional swing through non seam side boundary layer reattachment. This behaviour corresponds to low magnitude reverse swing, with a force coefficient of CF = −0.1. Rotational averaging is used to model rotating cricket balls, and produces a continuum of average force coefficients between these two values. Surface roughness is shown to change the boundary layer state on used cricket balls, and is quantified using equivalent sand-grain roughness, ks, and roughness Reynolds Number, Rek. Conventional swing is maximised by creating a smooth surface on both sides of the ball, maintaining a force coefficient in the range 0.3

This thesis investigates the effects of surface roughness and wall suction on the convective stability of boundary-layer flow over three body types. It compares the impact of these effects with other factors in delaying the onset of laminar-turbulent transition. Three distinct flow types over three geometric surfaces are considered: a still fluid over a rotating broad rough cone in a fixed frame of reference; an enforced axial flow over a rotating rough disk in a rotating frame of reference; and flow of a fluid with temperature-dependent viscosity over a permeable heated plate under the influence of parietal suction and injection. For each model, effects of both anisotropic and isotropic surface roughness on distinct instability properties of the boundary-layer flow over a rotating body are examined. This approach requires modification of the no-slip boundary condition to allow partial slip. Similarly, wall suction or injection is applied to the flow by simple modification of the no-penetration condition and existing boundary conditions on the flat plate. The Navier-Stokes equations are used to obtain the steady mean flow system, and linear stability equations are then formulated to obtain neutral stability curves. Stability analysis results are validated using linear growth rates and energy analysis. Results from these studies indicate that streamwise-aligned radial grooves have a strong destabilising effect on type II (viscous) instabilities, whereas concentric grooves and isotropic surface roughness stabilise the boundary-layer flow for type I (inviscid or crossflow) instabilities. A pronounced destabilising effect is also associated with increasing injection or increasingly temperature-dependent viscosity over a heated plate. In contrast, increasing either wall suction or temperature dependence results in significantly greater flow stability. Practical applications and extensions of these findings are considered in the context of chemical vapour deposition (CVD) reactors.

We present an experimentally guided study of film layer structure and opto-electronic properties of transition metal oxide (TMO) films. The oxide material system studied comprised the metals silicon (Si), zinc (Zn), and indium (In). The films were deposited via radio frequency magnetron sputtering (RFMS) on room-temperature Corning Eagle XG Glass (CEXG) substrates. Distinct (bi-layer (BL) vs single-layer (SL)) layer structures manifest as a function of angular distribution or pressure distance product (Greek letter 'phi') of sputtered material flux sourcing film growth. The films are amorphous, transparent and semiconducting. Experimental determination of absolute temperature (T) dependence of resistivity (Greek letter 'rho') revealed that at temperatures close to room-temperature, ionized impurity scattering (IIS) is the dominant conduction electron scattering mechanism. Thence, application of the Brooks-Herring (BH) model of IIS permitted analysis of the electronic state of the films. Thereby, the electronic state was revealed to be highly compensated. The design of experiment (DOE) and (associated) response surface analysis (RSA) frameworks were recruited from the very first stage - namely, the stage of film fabrication - of this study. This provisioned a self-referencing set of (nine) films (the 'samples') that are the subject of this study. The two layers of the BL films are / will-be-referred-to-as the sub-plantation layer (SPL) and the thin-film layer (TFL). The SPL is situated mediate substrate and TFL, and constitutes thereby the film-substrate interface. For consistent nomenclature, the term 'TFL' will be used to refer to the sole (film) layer of SL films. The layer structures of the films were established via x-ray reflectometry (XRR). The films were interrogated optically via spectroscopic ellipsometry (SE) (at room-temperature), and electrically via AC Field Hall Effect (ACFHE) measurements (between T = 10.1 K to 300 K). An account of the understanding of the film layers - viz., SPL, and TFL - as has been achieved, is as follows: ~ The sub-plantation layer (SPL) ~ We report the controlled emergence of a bonafide nanoscale layer - the SPL - at (comprising) the film-substrate interface. The determination of presence of a SPL is direct - that is, sans any assumptions, or modeling - via Fourier analysis of XRR results. We present three independent - experimental, empirical, and theoretical - threads of analysis to rationalize emergence of the SPL, as follows: > In terms of deposition process conditions under which a SPL manifests. Our semi-quantitative analysis is in terms of angular distribution or phi of the material flux sourcing film growth. Evidently, this thread of analysis is beholden to the specific physics of the deposition process, namely, RFMS. > Via RSA of SPL physical properties (SPL thickness (dSPL), SPL density (DSPL), and SPL roughness (rSPL)). This analysis reveals the following two process factors to be relevant: RF power (PRF), and process gas pressure (p). While the analysis is on the basis of experimentally observed process factors dependence of the physical properties noted, it is not beholden to the physics of the deposition process (RFMS). > Via dimensional analysis (DA) of the physical properties noted previously, in light of RFMS process. The dimensionless group for PRF (PRF*) thus determined reveals precisely the two previously noted process factors to be relevant. This analysis is ab initio. We highlight implications of our results for the industrially important problem of sputtered-film-on-substrate adhesion. Thereby, our results bear commercial promise, particularly for research and development (R&D) of flexible electronics applications. ~ The thin-film layer (TFL) ~ We quantify the semiconducting nature of the films (TFLs) on basis of optical (via SE) and electrical (via ACFHE) measurements of their room-temperature electronic properties. We interrogate the film (material system) electronic state on basis of the experimentally determined T dependences of conduction electron concentration (n) and conduction electron mobility (Greek letter 'mu'). Presence of a T-range (in the vicinity of and including room-temperature) where IIS is the dominant conduction electron scattering mechanism is established. Application of the BH model of IIS then lead to the (quantitative) determination that the electronic state is (highly) compensated. This determination - consistent with the experimentally observed anomalous oxygen content dependence of - is consistent with trap limited conduction. Thereby, we relate the electronic state to the chemistry and physics of film microstructure and material system. ~ The ready-reckoner ~ Figure 7.1 presents another and visual walk through - a 'ready-reckoner' - of this study. ~ Epilogue ~ This study represents new lines of investigation for the Professor Peter P. Edwards FRS ML Group.

Advanced mathematical models exist for the adhesion and detachment of particles from surfaces, either as single particles or multilayers. In Dry Powder Inhaler (DPI) systems for inhalation, blending of small micronized particles with a larger carrier is critical to ensure blend uniformity and dose consistency (adhesion). Conversely, when the patient comes to use their DPI, the force balance requirement changes and particle detachment drives the performance of the product and therapeutic effect by allowing particles to penetrate into the lungs. Understanding particle adhesion and detachment is critical. Particle size and shape, environmental humidity, surface chemistry and surface roughness all have an impact on the adhesion and ultimate entrainment of particles. In this work, novel microscopic scale surfaces were produced using advanced 3D printing technology (dual photon polymerisation) representative in size to a lactose carrier particle. A bespoke rig was constructed for the controlled aerosolization of particles in an airstream and particle detachment was recorded by air titration experiments. SEM and Raman technology were used to calculate particle detachment at different air flows. The greater the airflow velocity hitting the structure, the more micronized particles were detached from the 3D printed surfaces and entrained. The designed roughness of the 3D printed substrate surface was critical in determining particle detachment or retention in an airstream and this was analysed by atomic force microscopy (AFM). Microstructure roughness smaller than the diameter of the particle of interest was able to promote particle detachment consistent with the Rock'n'Roll particle resuspension theory however too high a surface roughness allowed mechanical interlocking of particles to occur. In these instances, particle detachment was poor and high adhesion zones were formed. Finally, Raman particle mapping technology was used to observe the dispersion of two commercially available micronized APIs across a DPI carrier particle using different powder blending techniques.

Abrasive Flow Machining technology is attracting more and more attentions and expanding into more areas by the industry and research community, particularly in the context of increasing demands for post-processing of complex aerofoil structures and additively manufactured components. This thesis presents an analytical scientific approach for investigating the material removal and surface generation in Abrasive Flow Machining in relation to the affecting factors from the material properties of fluid media, abrasive grains, operation conditions and workpiece material with the aid of multiscale multiphysics modelling and simulation. The multiscale multiphysics approach combined with micro-cutting mechanics is further presented to modelling and analysis of the surface roughness and topography profile generation in the AFM process. The analysis is developed and implemented by using the COMSOL multiphysics computational environment integrated with MATLAB programming as needed. The work described is fundamental but essential as a part of the efforts for developing the simulation-based virtual AFM system. The improved Preston equation is developed in this PhD research, which aims to enhance the scientific understanding of the AFM process and its industrial application. The improved Preston equation can be used to aid the engineers to optimise the process for desired surface roughness and edge tolerance characteristics on complex geometries in an intuitive and scientific manner. The methodology of deriving the equation underpins the fundamental cutting mechanics of abrasive flow machining assuming all abrasive particles within the media are spherical as manufacturers defined. Further to the derivation, four factorial experimental trials and computational fluid dynamics (CFD) simulations are implemented to generate the flow features of media on a coupon to evaluate and validate the equation for its competency and accuracy on prediction of material removals. The modified Preston equation can significantly contribute to the optimisation of the AFM process, which will advantage the integrated machine-process design to predict the virtual surface roughness and material removal rates. In this doctoral research, micro cutting mechanics analysis and Monte Carlo (MC) algorithms are integrated to support the virtual AFM system on the generation of surface texture and topography in the AFM process, through abrasive micro machining with thousands of grains with the complex machining trajectories and advanced analysis in a multiscale multiphysics manner. The method and basic design to determine the viscosity functions are studied and explored using a capillary rheometer and the geometric properties of the solid abrasive particles in the fluidic media. Those particles properties and media viscosity are the bare minimum required for developing multiscale multiphysics simulations on the AFM process. The method is used to evaluate the relative importance of the elastic effects of the polymer filled with particles. AFM trials and industrial case studies on aerofoil structures are conducted to validate the modelling and simulations developed against industrial requirements. There are good agreements between the results of simulations and the trials, further supported by industrial manufacturing data. The effects of process variables and tooling characteristics on material removal and surface roughness generation are investigated by analysing the results of AFM trials and simulations. AFM trials on IBR (Integrally Bladed Rotor) segments are carried out to validate the modelling and simulation mainly focusing on the profile accuracy control of leading/trailing edges of the IBR blades.

Nanofluids are advanced type of fluids that are produced by dispersing nanoparticles within a non-dissolving liquid. In heat transfer applications, these suspensions have shown to be superior to conventional heat transfer fluids in terms of thermal performance because of their enhanced effective thermal properties. The effective thermal conductivity of nanofluid depends on several factors, such as the preparation method employed, particles concentration, colloidal stability, thermal conductivities of both basefluid and solid particles used, ... etc. Furthermore, the suspension effective thermal conductivity can only have a value within the range of the added nanoparticles (highest) and the hosting fluid (lowest) thermal conductivities. Thus, to obtain an optimum effective thermal conductivity for a certain mixture with minimum degradation in the aforementioned property, the nanofluid needs to be homogeneously dispersed while sustaining its short and long-term stability. This is one of the main challenges seen today with such type of advanced fluids. Moreover, the nanofouling effect associated with these suspensions in operational conditions is another important factor that needs to be focused on, as it tends to change the surface wettability behaviour depending on the fluid and deposited surface properties, and hence can increase or decrease the heat transfer performance of the system. To address the previous challenges, the thesis at hand investigates the effect of nanofluid fabrication approach on its stability and pH value, and explores the influence of deposited particles of similar surface materials on the wettability behaviour of the surface. In order to achieve this, a two-step controlled temperature approach was used to fabricate the nanofluids at different set of fixed temperatures using a bath type ultrasonicator. The as- prepared suspensions were then characterised in terms of changes in pH value and stability using a pH meter and the sedimentation photograph capturing method, respectively. In addition, an electron beam physical vapour deposition technique was used to form nanoscaled layers on surfaces of similar materials to the evaporant source, so that a reflection of the nanofouling build-up on surfaces can be obtained, after which the wettability was examined, through a goniometer device, by varying the extracted liquid conditions. The results have shown that increasing the nanoparticles concentration had caused the fluid alkalinity level to increase, while the rise in nanofluid sonication temperature had led to a decrease in its pH value, and vice versa. Furthermore, a general correlation was developed to predict the changes in pH value for similar fabricated suspensions, which illustrated an overall accuracy of ~92% in its prediction capability. The shelving-life evaluation of aluminium - water dispersion has showed that the nanofluids fabricated via the two-step controlled temperature approach at 30ᴼC had better short and long-term stabilities than the ones produced by the conventional method. Moreover, the wettability behaviour of aluminium surfaces was seen to depend on the deposited aluminium film thickness, surface characteristics, and water properties; but in general, the water of pH 7 has demonstrated a tendency to enhance the hydrophilicity of the surface, while water of lower and higher pH values were seen to have the opposite outcome. On the other hand, the wettability behaviour of copper or stainless steel surfaces has shown to greatly depend on the surface topographical structure compared to the attached liquid properties.

Surface metrology has been widely used in manufacturing for many years. There has been a wide range of techniques applied for measuring surface topography. A photometric stereo technique is one of the best ways for the analysis of three-dimensional (3D) surface textural patterns. Many published works are concerned the developed approach for recovering the 3D profiles from surface normal. This research not only presents a methodology used to retrieve the profiles of surface roughness standards but also investigates the uncertainty estimation of textural measurement determined by the photometric stereo method. Various input quantities have been studied such as pixel error from recovered 3D surface textural patterns, the power of light source which involved with surface roughness average (Ra) value and the effect of room temperature. The surface roughness standards were utilized as the reference value. In term of increasing accuracy of the reference value, a contact method (stylus instrument) was used to calibrate them. Illumination angles of light source had some influence on the measurement results. A coordinate measuring machine (CMM) was used for holding the light source in order to study the effects of tilt and slant angles. The effect of tilt and slant angles were investigated. The results of these experiments successfully indicated that the angle used in photometric stereo method played an important role to the accuracy level of the roughness measurement results. The surface roughness specimen manufactured by a Computer Numerical Control (CNC) was applied to validate the capability of the photometric stereo system.

As fibre-reinforced cementitious composites (FRCC) are multi-scale materials, their structural performance depends on the micro-scale properties of the fibre-matrix bond. However, the development and utilisation of FRCC are restricted due to the limited knowledge of the micro-scale phenomena that influence the bond between the fibres and the cementitious matrix and its response to loading. The focus of this research was the definition of the properties of the fibre surface and the cement paste surrounding it, which affect the formation and performance of the fibre-matrix bond. The examination involved analysing the effect of the surface roughness of steel fibres on the microstructure of the interfacial transition zone (ITZ) and the degradation of the fibre-matrix bond under repeated loading. The micro-scale properties were explored by employing a different approach to applying the existing experimental techniques to the FRCC. The utilisation of scanning electron microscopy (SEM) and phase-contrast micro-computed tomography (µCT) enabled the identification of the changes in the distributions of calcium hydroxide, calcium silicate hydrate, pores and unhydrated cement grains within the ITZ. The application of phase-contrast µCT allowed access to the three-dimensional microstructure of the cement paste around the fibre. The importance of the surface roughness of steel fibres for the packing of cementitious grains was examined by estimating the average height and wavelength of surface irregularities using an SEM image analysis and directly measuring the parameters using an atomic force microscope and stylus profilometer. The effect of the fibre surface roughness on its wettability was evaluated through contact angle goniometry. The decrease in the mobility of the water along the fibres that was observed with an increase in fibre surface roughness facilitated the reduction in the porosity near these fibres, which was confirmed using SEM. The resulting mechanical response of the bond between the cement paste and fibres with different types of surface roughness was examined under direct tension cycles with gradually increasing amplitudes. The outcomes of the fibre pull-out tests indicated that the detected micro-scale changes in the properties of the fibres and the cement paste surrounding them influenced the maximum capacity of the fibre-matrix bond and its deterioration. The development of the residual slip was identified from the beginning of loading with the three stages of evolution: deceleration, steady stage and acceleration. This study points out that the properties of the fibre surface and the cement paste surrounding it clearly affect the performance of the fibre-matrix bond by introducing novel insights about the fibre-matrix interaction that advance the development and modelling of FRCC. [ABSTRACT FROM AUTHOR]

Probe microscopy techniques (Atomic Force Microscopy and Kelvin Force Microscopy) have been shown to be instrumental in the analysis of samples; such as resists and nanostructured materials. Through these techniques detailed surface information has been derived, including information such as surface roughness and surface charge distribution. Poly(Methylmethacrylate) (PMMA), remains at the forefront of resists utilised in e-beam lithography in the electronics industry. Surface morphology (specifically roughness) analysis remains a key parameter of investigation, particularly in the examination of polymeric films. This research aimed to investigate PMMA based electron beam resists as well as a novel (SML) resist material in terms of suitability for electron-beam lithography. Various concentrations (5, 7, 8, 9 and 11% w/v) of both PMMA and the novel resist material were spin-coated onto silica substrates. Samples were baked at 180oC for 3 minutes and examined under ultra-high vacuum using Omicron AFM/SPM to derive RMS values in order to assess roughness in addition to thickness measurements taken. SML resists were then utilised in the development of a new digital etch onto InGaAs/InAlAs wafer. The novel, SML resist material was found to offer smoother resist surface even at higher concentrations of polymer, a difference which was observed to be statistically significant (p<0.01). The SML resist was also notably thicker than the comparable PMMA resist (p>0.05) indicating that lower concentrations of the novel resist would be required to achieve the required resist thickness. Digital etching rates were found to be in agreement with previously documented findings. SML was concluded to be a superior resist in terms of thickness and smoothness, with AFM being further established as an essential characterization technique.

This thesis investigates the cooling behaviour of polymers during the microinjection moulding process. The work included bespoke experimental mould design and manufacturing, material characterisation, infra-red temperature measurements, cooling analysis and cooling prediction using commercial simulation software. To measure surface temperature of the polymers, compounding of polypropylene and polystyrene with carbon black masterbatch was performed to make materials opaque for the IR camera. The effects of addition of carbon black masterbatch were analysed using differential scanning calorimetry and Fourier transform infrared spectroscopy. Sapphire windows formed part of the mould wall and allowed thermal measurements using an IR camera. They were laser machined on their inside surfaces to generate a range of finishes and structures. Their topographies were analysed using laser confocal microscope. The surface energy of sapphire windows was measured and compared to typical mould steel, employing a contact angle measurement technique and calculated using Owens-Wendt theory. A heating chamber was designed and manufactured to study spreading of polymer melts on sapphire and steel substrates. A design of experiments approach was taken to investigate the influence of surface finish and the main processing parameters on polymer cooling during microinjection moulding. Cooling curves were obtained over an area of 1.92 by 1.92 mm of the sapphire window. These experiments were conducted on the Battenfeld Microsystem 50 microinjection moulding machine. A simulation study of polymer cooling during the microinjection moulding process was performed using Moldflow software. Particular interest was paid to the effect of the values of the interfacial heat transfer coefficient (HTC) on the simulated cooling predictions. Predicted temperature curves were compared to experimentally obtained temperature distributions, to obtain HTC values valid for the material and processing parameters.

Carbon fibre-reinforced plastics (CFRP) are widely used in aerospace, automobile and other structural applications due to their superior mechanical and physical properties. CFRP outperform conventional metals in high strength-to-weight ratio. Usually, CFRP parts are manufactured near to net-shape;however,machining is unavoidable when it comes to assembly. Drilling the holes are essential to facilitate riveting and bolting of the components. However, conventional drilling (CD) induces different types of damages such as cracking, fibre pull-out, sprintling and delamination due to the abrasive nature, inhomogeneity and anisotropy of CFRP. A novel technique, ultrasonically-assisted drilling (UAD) is hybrid machining technique in which highfrequency (typically above 20 kHz) vibration are superimposed on a standard twist drill bit in axial direction using ultrasonic transducer. UAD has shown several advantages such as thrust force reduction, improving surface quality and lower bur-formation in drilling of conventional metals. UAD has also effectively been used for drilling brittle materials.

The research presented is part of a larger study, dedicated to investigating flow boiling in small to microchannels. The test facility, originally designed by Huo (2005) and since used by Chen (2006) and Mahmoud (2011), has been used to investigate flow boiling of R134a across a range of channel diameters and both seamless cold drawn and welded channels. These previous studies concluded that one of the reasons for discrepancies in reported data is the result of surface characteristics. The objective of this current study is to further investigate the effect of channel characteristics and changing the refrigerant to R245fa. Surface characteristics are investigated with stainless steel, copper and brass channels, all seamless cold drawn and 1.1 mm internal diameter. Experiments using R245fa were initially conducted in the same stainless steel channel used with R134a by Mahmoud (2011). This allowed for the surface characteristics to be negated and the comparison to be based purely on the changes in the thermophysical properties between R134a and R245fa. Experiments were conducted at inlet pressures of 1.85 and 2.45 bar, mass fluxes of 100 – 400 kg/m2s, heat fluxes from 1 – 60 kW/m2 and vapour qualities from 0 – 0.95. The test section surfaces were evaluated based on scanning electron microscopy (SEM) and confocal laser microscopy (CFLSM). SEM allowed for a visual inspection of the channel surface, with clear differences in the surface stricter evident. The surfaces were then compared based on two CFLSM profilers. The values of the surface parameters differed between the two profilers but the same trend was seen, brass being the roughest surface and copper the smoothest. Changes in the surface parameter values were found to be a function of the scan area, scan resolution and cut-off value. A borosilicate glass tube, at the test section exit, allowed for flow visualisation. Mahmoud (2011) reported bubbly, slug, churn and annular flow for R134a, with no effect of hysteresis. Churn and annular flow were present for R245fa with an increasing heat flux. This was a result of a higher surface tension for R245fa which facilitates annular flow. Hysteresis was evident for R245fa, with bubbly, slug, churn and annular flow seen with a decreasing heat flux. The hysteresis effect is a result of nucleation sites activating during the increase in heat flux and remaining activated as the heat flux is decreased. The activation of nucleation sites depends on the size, which was constant due to the same channel being used, and the wall superheat. The wall superheat is lower for R245fa which does not allow for the nucleation sites to be initially activated with an increasing heat flux. The same effect of hysteresis was evident for copper and brass. Differences in the exit vapour quality and heat flux at which flow patterns occurred were seen between the three materials. The heat transfer coefficient varied in both magnitude and trend between R134a and R245fa. Mahmoud (2011) reported an almost constant heat transfer coefficient with vapour quality at a higher magnitude than seen for R245fa. R245fa showed an increasing trend with vapour quality. Peaks in the heat transfer coefficient were seen to be a result of surface flaw, evident when plotting as a function of the axial location. The test section was reversed in orientation, moving the location of the peak from near the entry of the test section to near the exit. A similar heat transfer coefficient peak was seen at the same axial location, near the exit of the test section, confirming that the peak was a result of a surface flaw and a result of the flow developing. The heat transfer coefficient changed in magnitude and trend for copper and brass. The magnitude of the recorded heat transfer coefficient did not follow the same trend as the surface parameters. The heat transfer correlations in literature did not predict the increase in the heat transfer with vapour quality, performing poorly compared with R134a. The best correlation for the prediction of both refrigerants was that of Mahmoud and Karayiannis I (2012). The pressure drop for R245fa was over 300 % higher than that of R134a, with a steeper increase with heat flux. This is attributed to a higher liquid viscosity and lower vapour density for R245fa. The pressure drop was highest for the roughest channel, brass, but lowest for stainless steel which had the intermediate roughness. The smoothest channel, copper, showed the largest difference in the effect of inlet pressure on the measured pressure drop and the roughest surface, brass, the smallest difference. The effect of surface characteristics on pressure drop is greater than the effect of changes in the fluid properties with inlet pressure. Pressure drop correlations performed poorly for R245fa in comparison with R134a, with the majority under predicting the pressure drop. Only one pressure drop correlation included a function of the surface parameters, Del Col et al. (2013), but this correlation under predicted the effect of the surface parameters on pressure drop. There was no one correlation which gave satisfactory results for all three materials.

Synthetic Aperture Radar (SAR) has been identified as a good candidate to provide high-resolution soil moisture information over extended areas. SAR data could be used as observations within a global Data Assimilation (DA) approach to benefit applications such as hydrology and agriculture. Prior to developing an operational DA system, one must tackle the following challenges of soil moisture estimation with SAR: (1) the dependency of the measured radar signal on both soil moisture and soil surface roughness which leads to an ill-conditioned inverse problem, and (2) the difficulty in characterizing spatially/temporally surface roughness of natural soils and its scattering contribution. The objectives of this project are (1) to develop a roughness measurement method to improve the spatial/temporal characterization of soil surface roughness, and (2) to investigate to what extent the inverse problem can be solved by combining multipolarization, multi-incidence, and/or multi-frequency radar measurements. The first objective is achieved with a measurement method based on Structure from Motion (SfM). It is tailored to monitor natural surface roughness changes which have often been assumed negligible although without evidence. The measurement method is flexible, a.ordable, straightforward and generates Digital Elevation Models (DEMs) for a SAR-pixel-size plot with mm accuracy. A new processing method based on band-filtering of the DEM and its 2D Power Spectral Density (PSD) is proposed to compute the classical roughness parameters. Time series of DEMs show that non-negligible changes in surface roughness can happen within two months at scales relevant for microwave scattering. The second objective is achieved using maximum likelihood fitting of the Oh backscattering model to (1) full-polarimetric Radarsat-2 data and (2) simulated multi-polarization / multi-incidence / multi-frequency radar data. Model fitting with the Radarsat-2 images leads to poor soil moisture retrieval which is related to inaccuracy of the Oh model. Model fitting with the simulated data quantifies the amount of multilooking for di.erent combinations of measurements needed to mitigate the critical e.ect of speckle on soil moisture uncertainty. Results also suggest that dual-polarization measurements at L- and C-bands are a promising combination to achieve the observation requirements of soil moisture. In conclusion, the SfM method along with the recommended processing techniques are good candidates to improve the characterization of surface roughness. A combination of multi-polarization and multi-frequency radar measurements appears to be a robust basis for a future Data Assimilation system for global soil moisture monitoring.

Resin composites have been in the dental field for over forty years. They are now thought to be the most commonly used restorative material due to their aesthetic and mechanical properties. Although resin composites have high success rates as restorations, they do not offer all properties of an ideal restorative material. The aims of this research were to characterise the effects of variation in resin composite formulation on handling, mechanical; and physical properties. In particular the influence of the size and distribution of the inorganic components was investigated through the study of experimental formulations. Packing stress and viscosity were assessed with pentrometer principle at two different temperatures (23 and 37 ºC). It was found that filler size was strongly correlated with both packing stress and viscosity. Additionally, temperature has a dominant effect on packing stress and viscosity. Micro computed tomography [μCT] was used to investigate percentage of voids [% voids] in 3D dimensions. It was found that smaller filler size incorporated less % voids. In contrast filler size and disruption had a little effect on fracture toughness of resin composites. 3D surface topography was used to investigate the surface roughness before and after tooth brush abrasion. It was found filler size had a significant influence in both gloss retention and surface roughness (smaller filler size exhibited higher surface gloss). Finally, the effect of different storage media (distilled water, Coca Cola and red wine) on colour stability and gloss were investigated. It was found that dietary habits effect discolouration of resin composite restorations with the acidic drinks caused more staining.

Flows over hydraulically smooth walls are predominant in turbulence studies whereas real surfaces in engineering applications are often rough. This is important because turbulent flows close to the two types of surface can exhibit large differences. Unfortunately, neither experimental studies nor theoretical studies based on conventional computational fluid dynamics (CFD) can give sufficiently accurate, detailed information about unsteady turbulent flow behaviour close to solid surfaces, even for smooth wall cases. In this thesis, therefore, use is made of a state of the art computational method “Direct Numerical Simulation (DNS)” to investigate the unsteady flows. An “in-house” DNS computer code is developed for the study reported in this thesis. Spatial discretization in the code is achieved using a second order, finite difference method. The semi-implicit (Runge-Kutta & Crank-Nicholson) time advancement is incorporated into the fractional-step method. A Fast Fourier Transform solver is used for solving the Poisson equation. An efficient immersed Boundary Method (IBM) is used for treating the roughness. The code is parallelized using a Message Passing Interface (MPI) and it is adopted for use on a distributed-memory computer cluster at University of Aberdeen as well as for use at the UK’s national high-performance computing service, HECToR. As one of the first DNS of accelerating/decelerating flows over smooth and rough walls, the study has produced detailed new information on turbulence behaviours which can be used for turbulence model development and validations. The detailed data have enabled better understanding of the flow physics to be developed. The results revealed strong non-equilibrium and anisotropic behaviours of turbulence dynamics in such flows. The preliminary results on the rough wall flow show the response of turbulence in the core and wall regions, and the relationship between the axial and the other components are significantly different from those in smooth wall flows.

Light detection and ranging (LiDAR) is a well-established technology that provides precise three-dimensional (3D) spatial information. However, conventional monochromatic LiDAR is weak at observing material information, which is crucial for comprehensive 3D digitization and environmental perception. The most established solution for the joint acquisition of spatial and material information is fusing spectral data from an RGB/hyperspectral camera and point cloud data from a monochromatic LiDAR. This sensor fusion approach encounters inherent challenges, such as co-registration problems between point cloud data and camera images and the high sensitivity to ambient light variation due to cameras being passive sensors. To address these problems, multispectral LiDAR was proposed a decade ago by extending the spectral dimension of conventional monochromatic LiDAR to provide simultaneously 3D spatial and spectral information through fully active sensing without the need to co-register spatial and spectral data. Nonetheless, material information is not solely encoded in the optical intensity of the backscattered light from a target surface but also in other optical modalities, such as phase, polarization, and frequency shifts. This thesis introduces the concept of multimodal multispectral (MM) LiDAR, which extends the modal dimension of multispectral LiDAR and thus allows for enhanced material probing capabilities. A comb-based MM LiDAR prototype was developed in this work, including three optical modalities (i.e., reflectance, penetration depth, and polarization) and 33 spectral channels from 580 nm to 900 nm with 10 nm resolution. Built upon a mode-locked femtosecond supercontinuum laser source and taking advantage of the intermode-beating approach in distance measurement, the comb-based MM LiDAR achieves sub-mm distance precision for most spectral channels at a ranging distance of 0.5 m with 1 ms integration time. This performance provides the basis for observing the wavelength-dependent penetration depth of light in target materials. This extended modal dimension demonstrates better material classification performance on material specimens relevant to construction, e.g., stone, wood, plastic, and concrete. Further contributions of this thesis include proposing a specialized feature selection method and decision-making pipeline to determine the optimal feature configuration of the MM LiDAR developed and used within this thesis, considering the classification task among multiple material categories and the data structure of MM features. Moreover, this thesis introduces polarization-resolved reflectance spectra extracted from the MM feature space and leverages them to augment the classification of material composition and enable the observation of additional target characteristics, such as surface roughness. Overall, the findings of this work contribute to advancing LiDAR technology beyond 3D and towards holistic environmental perception.

As the semiconductor industry grapples with escalating scaling challenges associated with the floating gate MOSFET, alternative memory technologies like Resistive Random Access Memory (ReRAM) are gaining prominence in the scientific community. Boasting a straightforward device structure, ease of fabrication, and compatibility with CMOS (Complementary Metal-oxide Semiconductor) Back-end of Line (BEOL), ReRAM stands as a leading candi- date for the next generation of non-volatile memory (NVM). ReRAM devices feature nanoionics-based filamentary switching, outperforming flash memory in terms of power consumption, scalability, retention, ON/OFF ratio, and endurance. Furthermore, integrating ReRAMs within the CMOS BEOL/low-k Cu interconnect system not only reduces latency between the connectivity constraints of logic and memory modules but also minimizes the chip footprint. However, investigations have revealed a significant concern surrounding ReRAMs—specifically, their electro-thermal reliability. This research provides evidence highlighting the critical influence of material properties, deposition effects, and thermal transport on the device's performance and reliability. Various material systems have undergone in this work scrutiny to comprehend the impact of intrinsic material properties such as thermal conductivity, specific heat capacity, thermal diffusivity, and deposition effects like surface roughness on the electroforming voltages of ReRAM devices. The reference device structure considered in this work is Cu/TaOx/Pt, which has been compared with alternative configurations involving metals like Ru and Co as potential substitutes for Pt. Additionally, a new vehicle has been introduced to quantify cell degradation resulting from thermal cross-talk in crossbar Resistive Random Access Memory (ReRAM) arrays. Furthermore, a novel methodology has been presented to predict cell degradation due to remote heating, taking into account the cell's location, the material properties of the device, and geometry of its electrodes. The experimental results presented in this study showcase filament rupture caused by remote heating, along with spontaneous filament restoration ensuing from the subsequent cooling of the ReRAM cell.

Radar cross section (RCS) of electrically large targets can be challenging and expensive to measure. The use of scale models to predict the RCS of such large targets saves time and reduces facility requirements. This study investigates Ka-band (27 to 29 GHz) RCS prediction from scale model measurements at 500 to 750 GHz. Firstly, the coherent quasi-monostatic turntable RCS measurement system is demonstrated. Secondly, three aluminum 18:1 scale dihedrals with surface roughness up to 218 icroinches are measured to investigate how the roughness affects the Ka-band prediction. The measurements are compared to a parametric scattering model for the specular response, and indicate that the models’ surface roughness have negligent effect on the RCS prediction.

Previous research investigated several influence factors on soil-material interface behaviour through interface direct shear tests. However, conventional shear tests typically use a metal shear box to obtain the stress-strain relationship, which does not allow for the corresponding particle image to be captured by a camera. In this research, Particle Image Velocimetry (PIV) technology was applied to analyse particle behaviour and contributed to a fundamental understanding of soil-material interface behaviour. Several modifications were made to the shear apparatus to enable the use of PIV technology, which then allowed for its application in engineering and fundamental design optimization. The fundamental research conducted in this study involved parametric studies to investigate several factors that can influence interface behaviour, including surface roughness, surface hardness, particle breakage, relative density and confinement condition. Additionally, a portable surface profile gauge and the Mohs scale were utilized to characterise the surface properties. Test results reveal that surface roughness and surface hardness have significant effects on soil-material interaction, particularly in terms of peak shearing strength. To capture particle behaviour in sequential frames, such as breakage, interlocking, movement, and rotation, several modifications were implemented to the shear apparatus, including the use of a symmetric loading system, custom-built transparent shear box, camera and illumination system. The application of a high-resolution Digital Single-Lens Reflex (DSLR) camera also enhanced the quality of the captured images. The research outcomes validated the four-stage model proposed in previous research and demonstrated that the development of shearing strength corresponds to particle interlocking. In comparison to the stress-strain relationship of the soil-material interface, it was observed that a rough surface resulted in increased particle interlocking, more significant movement, and a thicker shearing zone. And a hard surface led to larger residual shearing strength and a thicker shearing zone. This study aimed to explore the interface behaviour of drilled piles by investigating the lubrication effect on soil-pile interface characteristics through interface shear tests. Two types of disturbed soil samples were collected from the same sand stratum and used for fundamental research. One type of sample was collected during the wet processing of drilled pile construction, where the soil was mixed with bentonite slurry. The other soil sample was collected during the site investigation and mixed with bentonite powder, then prepared using the S2 method in the laboratory. The testing results revealed that the interface characteristics can be altered by increasing the bentonite content. [...]

Laser powder bed fusion (L-PBF) process represents a form of metal additive manufacturing (AM) where micron-level powdered material is selectively melted and fused layer by layer to create intricate three-dimensional parts. This process involves rapid melting and solidification, leading to intense thermocapillary convection within the molten pool. The melt pool is a crucial element of the L-PBF process and refers to the localized region where the powder particles are melted and solidified to form each layer of the printed part. The shape and dimensions of the melt pool directly influence the accuracy and surface finish of the printed part. Precise control of the melt pool geometry is essential for achieving the desired dimensions and avoiding defects in the final part. Optimizing process parameters and achieving high-quality printed parts require a deep understanding of the dynamics governing the melt pool. In this regard, both experimental and simulation methods were employed to study the melt pool geometry and its variations, considering various parameter combinations and different length scales. The printed parts were also examined for defects like porosity and to analyze their surface characteristics. The study started with an initial implementation of a simplified three-dimensional model of a powder bed using ANSYS Fluent. The simulation setup was based on a custom user defined function that integrated a volumetric heat source, temperature-dependent material properties, and volume of fluid method for identifying the free surface. The simulation setup was then employed to investigate the impact of varying powder size distributions on the formation of a melt pool. The results show that the size and distribution of particles in the powder mixture play a crucial role in shaping the evolution and geometry of the molten pool. Smaller particles encourage a consistent and uninterrupted flow within the molten pool. However, the presence of voids promotes fluid convection in the downward direction, leading to a temporary increase in the depth of the molten pool. This finding highlights the importance of understanding the role of particle size and distribution in shaping the characteristics of the melt pool during the L-PBF process. The evolution of the melt pool in the L-PBF process is closely related to pore formation in the final printed parts. Porosity refers to the presence of voids or empty spaces within the printed parts during the AM processes. Several factors related to melt pool dynamics, such as insufficient energy input, balling phenomenon, insufficient overlapping, gas entrapment, and overheating can contribute to pore formation. When the energy density is high, there is a possibility of forming keyhole pores. This occurs when excessive energy input from the laser causes deep penetration of the molten material into the powder bed, resulting in an elongated shape cavity resembling a keyhole shape. Multiple tensile coupons were printed with various parameters to understand pore morphology before and after fracture. A non-destructive technique of micro-CT scan method was utilized to analyze the porosity. The findings indicate that the energy density and build orientation significantly influence the porosity of the as-built printed samples, while the impact of the location change is observed to be minimal. After undergoing tensile testing, the samples exhibit a notable increase of more than nine percent in both pore volume and porosity percentage compared to their initial as-built counterparts. These results emphasize the importance of carefully controlling energy input and optimizing build orientation to mitigate porosity and enhance the quality of L-PBF printed parts. During the L-PBF process, a laser with a spot size ranging in the hundreds of microns interacts with metal powder to form tracks. The laser follows predefined scan paths in each layer, and the behavior of the melt pool during each scan is heavily influenced by the laser power and scan speed. The melting process can occur in three modes: incomplete melting, conduction mode melting, and keyhole mode melting, depending on the combination of these two parameters. Only conduction and keyhole mode melting result in the formation of continuous and complete tracks. The length of the scan determines whether the scanned track reaches a quasi-steady state or not. Regardless of the laser power and scan speed values used, a transient region exists at the start and end of long scan vectors. The melt pool geometry in this transient region displays distinct characteristics compared to the quasi-steady region in the middle. The physics of the melt pool dynamics in these transient states remain largely unexplored. Understanding the characteristics of the melt pool in the transient region is essential to ensure the quality of smaller-dimensional parts in the L-PBF process. Improving our knowledge in this area can lead to better control over the printing process and enhanced quality of the final printed components. The research involved conducting experiments on one-dimensional line scans, referred to as single tracks, using an extensive design of experiment (DOE) approach for process parameters and multiple replicates with several builds. The surface data from these as-built tracks were collected using a non-contact optical profilometer, the WYKO NT1100. The analysis of the single tracks revealed that the track width and surface height varied along the scan line. Particularly, the track width at both the start and end of the track demonstrated distinct characteristics with significant fluctuations. The region in the middle, referred to as quasi-steady region, showed uniform width with relatively low variation. The transient and quasi-steady regions were quantified based on the track width variations along the scan line. Additionally, the length of the transient region was not constant for all the parameters but varied with power and scan speed settings. The analysis results show that the transient length at the start ranged from 300 microns to 1400 microns, for the power and scan speed values used in the experiment. Following the analysis of results from the single track experiment, the research progressed to fabricating two-dimensional raster-area scans. The findings of the single track experiment were integrated into the experimental setup of the raster scans to refine the DOE. The two-dimensional prints incorporated extra process parameters like hatch spacing and the number of scan lines. The results show that the parameters that resulted in larger transient regions for raster scans also resulted in higher surface roughness. The shorter scan lengths which only consisted of transient zones resulted in higher surface roughness and the increasing scan length reduced the average roughness. In addition to examining the surface characteristics of the transient region, another set of experiments was conducted to analyze the surface roughness of raster scans in the quasi-steady regions. This experiment involved assessing the impact of process parameters, including laser power, scanning speed, and hatch spacing, on the surface characteristics of single-layer raster scan areas through the design of experiment and multiple replicates. The result revealed that raster scan areas with lower laser power, higher scanning speed, and higher hatch spacing have higher surface roughness. Moreover, among the three main parameters, laser power played the most significant role in determining the surface roughness value.

The curing characteristics of photopolymer resin determine the relationship between the vat polymerization (VP) process parameters and the layer thickness, geometric accuracy, and surface quality of the 3D printed specimen. Dispersing filler material into the photopolymer resin changes its curing characteristics because the filler scatters and absorbs light, which modifies the curing reaction. However, the ability to cure photopolymer resin with high filler volume fraction is important to 3D print material specimens for specific engineering applications, e.g. structural polymer composite materials, electrical and thermal conductive materials, and ceramic materials for biological and high-temperature environments. We methodically measure the curing characteristics of diacrylate/epoxy photopolymer resin with dispersed glass microspheres. The experiments show that the curing depth, degree-of-cure, and surface roughness depend on both the light exposure dose and the filler fraction. We determine that the degree-of-cure increases with increasing filler fraction for constant exposure dose, and approaches 90% with increasing exposure dose, independent of the filler fraction. The geometric accuracy of the 3D printed specimens decreases with increasing exposure dose and with increasing filler volume fraction due to so-called profile broadening. Finally, we show that the average surface roughness of the 3D printed specimens decreases with increasing exposure dose and filler fraction. This work has implications for VP of photopolymer resins with high filler fraction.

As the existing steel infrastructure inevitably continues to age and deteriorate, engineers are increasingly looking for innovative and effective methods for repairing and maintaining existing structures. Structural steel components can degrade due to the surrounding environmental conditions, and are susceptible to corrosion damage when exposed to aggressive environments and deicing salts. The conventional methods for repairing steel structures can be labor-intensive and time-consuming, and add considerable weight to the existing structure. One alternative is utilizing carbon fiber reinforced polymers (CFRP). Many studies have documented the ability of CFRPs to enhance the strength of existing structures. Furthermore, CFRP offers the benefits of being non-corrosive and having a high strength-to-weight ratio. Most studies on steel strengthening have focused on the bond behavior of CFRP to steels having a smooth surface condition, which are not representative of deteriorated structures in greater need of retrofitting. Further research has examined the durability of CFRP-steel bonds relative to environmental conditions that do not reflect the service life conditions for typical applications. In this work, a comprehensive study is conducted on the effects of the surface condition and environmental exposure on the bond between CFRP and steel. The influence of corrosion and simulated corrosion pitting is evaluated to determine whether structures with non-uniform surfaces are adequate for CFRP retrofits. In addition, the durability of CFRP-steel bonded systems is investigated through laboratory hygrothermal aging and in-situ environmental conditioning to multiple environments in Virginia. The research can be useful in the development of guidelines that will assist engineers determine if a CFRP retrofit solution is applicable in a given environmental setting and appropriate for the level of deterioration of the structure.

The as-printed surfaces of parts produced through laser powder bed fusion are significantly rougher than surfaces produced through traditional manufacturing processes. This increased roughness can have a significant impact on mechanical properties, with perhaps the most notable detriment in the fatigue life of the part. Therefore, the as-printed surface roughness in additively manufactured materials must be studied more extensively to determine its impact on fatigue performance. This work investigates the surface roughness of additively manufactured specimens through the investigation of processing parameters and their effects on surface roughness in metal additive manufacturing. Furthermore, the relationships between as-printed surface roughness and fatigue behavior in AM materials are studied using both axial fatigue testing and vibration bending fatigue testing of nickel superalloy 718. Following the results of these initial tests, this work also examines the relationships between sharp corners and fatigue life in as-printed additively manufactured alloy 718. Results suggest that both rougher surfaces and sharp corner geometries cause decreases in fatigue life, thus providing guidelines for the design of additively manufactured components under fatigue loading conditions.

A human’s interaction with the outside world begins with the human skin and therefore, contact mechanics of human skin is an important area of research. The applications are all-encompassing, from medical technology in the form of drug delivery mechanisms and prosthetics to the digital world in the form of touchscreens or even personal care. The variations in morphological and physiological features in combination with the properties of counter surfaces make human skin contact a complex problem. There are several aspects of this complex tribological system that need to be addressed. These include characterizing the surface topography of human skin, enhancing the predictability of contact parameters, and understanding the mechanics at the interface of such interactions.In this study, as the first specific aim, a method is developed to characterize the directionality of skin tension lines using statistical methods of characterizing rough surfaces. The method is able to capture the increasing anisotropy of human skin with aging. The method can be applied to the surface coordinates of the skin and the pixel intensity data from skin images.The second specific aim is to predict the coefficient of friction considering the changes in the skin's morphological and physiological features. To achieve this, a fractal-based finite element model in combination with an interfacial condition-enhanced empirical method is used. Results show that the proposed approach can replicate several experimental findings from the literature.Human skin in general is a soft material. Therefore, the recent understanding of contact mechanics of soft materials is applicable to skin. The third specific aim is to understand the contact mechanics at the interface of skin interactions. To this end, we use finite element models to first extend the current single asperity studies to three-dimensional soft materials. Specifically, we investigate the role of surface roughness and material properties in area reduction and coefficient of friction. This is further extended to human skin using image-based models. Area reductions in sliding over human skin depend on the interplay of morphological and structural changes due to age, humidity, etc. In the end, a detailed finite element study is also performed to characterize the role of counter surface material and roughness properties in human skin friction. Results show that the role of counter surface roughness in these interactions is a function of the interplay of its mechanical properties and normal load.Overall, this research explores several components in the tribological domain of human skin. The effort introduces an innovative and simple method to ascertain the directionality of skin tension lines. The fractal-finite element approach provides a simple tool to predict the coefficient of friction that can be used as a plug-in for macroscopic models. A detailed computational study is performed to understand the interplay of mechanisms at the interface of human skin. The study provides several key insights into the role of features of skin and counter surfaces in these interactions. The findings of this research are useful in setting product design guidelines to increase human comfort and enhance quality of life.

Zirconia has been established as a promising material for dental implants. Various surface treatment methods have been utilized to promote better osseointegration and improve the success rate of dental implants. However, a better understanding of the influences of topographic characteristics on cell attachment, proliferation, and differentiation is needed. Different surface topographic zirconia specimens, As sintered, Mild rough, Moderate rough, and Rough zirconia groups were fabricated with sandblasting method in various distances and stages. The surface texture, microstructure, and wettability were inspected with the optical profiler, SEM, and contact angle measurement respectfully. Human primary osteoblast cells were cultured on the four groups of zirconia with different surface modifications in 24 well plates and on plates without test material as control. Crystal violet and triton X-100 solution were used to evaluate cell attachment efficiency at 9 hours and proliferation rate at 7, 14, and 21 days after seeding. ALP activity was measured with fluorometric assay. The expression of osteocalcin was measured with an ELISA kit. Alizarin red staining was conducted to evaluate the mineralization. The cell morphologies were inspected under SEM after cell fixation and critical point drying process. The data were analyzed with one-way ANOVA for experiment on each time interval and two-way ANOVA for all time points. Tukey post hoc test was used for pairwise comparison. P value < 0.05 was considered statistically significant. Topographic parameters and contact angle measured in As sintered, Mild rough, Moderate rough, and Rough surface groups were as follow: Sa = 0.23, 0.50, 2.13, 5 µm, Sal = 49.88, 21.20, 30.42, 49.87 µm, Sdq = 64.64, 248.60, 511, 734.66 µm/mm, Sk = 0.7, 1.54, 4.19,16 µm, Spk = 0.31, 0.64, 1.47, 5.13 µm, Svk = 0.35, 0.71, 5.96, 6.18 µm respectively, and contact angle = 64.6°, 55.2°, 43.5°, 38.6° respectively. The result showed that Rough zirconia group induced the highest cell attachment efficiency at 9 hours (p

This work focuses on the development of a novel method for joining and residue-free separation of polymer surfaces that support polymer recycling and enables the bond-ing of incompatible polymers. The technology presented employs polymer surface modification to generate functional groups that enable reversible joining through intermolecular interactions between two rigid, macroscopic polymer surfaces. The research consists of four segments, each emphasizing distinct elements of the join-ing process. The first section, which deals with the contact mechanics and adhesion of macro-scopic surfaces, deepened the understanding of the interactions between polymer surfaces by analyzing topographically defined polystyrene surfaces produced via hot pressing. Using atomic force microscopy and a specially developed measuring clamp, surface adhesion was investigated in relation to topography and oxygen plasma treatment and compared with established adhesion models (Johnson-Kendell-Roberts and Pastweka-Robbins adhesion criterion). It was determined that these models inadequately represent complex polymer surface interactions and are only conditionally suitable for predicting polymer adhesion. Thus, model modifications are required, to which the presented techniques could contribute. In the second section, the potential of low-pressure plasma treatment for modifying polystyrene and polyamide 12 surfaces was examined. By introducing functional groups into the polymer surface, the surfaces could be firmly bonded together by pressing without the use of adhesives. However, with water as a trigger, the bonds could be dissolved again within seconds. This separation mechanism suggests that the joining forces could be mainly based on hydrogen bonds. After dissolving the bond in water, the surfaces could be reconnected by renewed plasma treatment. The third section investigated the role of acrylic acid and copper(II) ions on the adhe-sion and separation of bonded polystyrene surfaces. Oxygen plasma modified and acrylic acid grafted (wet chemical process) surfaces were treated with copper(II) ions to analyze the effects of surface treatment, ions, and joining temperature on adhesive force and separation. Acrylic acid grafted samples exhibited enhanced adhesion due to an increased number of functional groups compared to surfaces treated with oxy-gen plasma only. Acrylic acid grafting also allowed for more significant copper(II) ions loading, which increased adhesion. The bond strength could be controlled by varying the joining temperatures and the copper(II) ion loading. The separation time of the joint could also be altered by controlling these parameters from seconds to insol-ubility in water. Nevertheless, all joints could be separated with EDTA and ultrasound. In the fourth section, the feasibility of transferring acrylic acid grafting to an easily scalable inline process was explored. Atmospheric plasma was used to apply acrylic acid directly to the surface, eliminating the need for a wet chemical process. The adhesion of the applied acrylic acid layer was found to be dependent on the underly-ing polymer, which was particularly noticeable when the polymers were separated in water. Joints, where polyamide 12 was involved, exhibited higher water separation resistance. In addition, the effect of different metal ions on adhesion and joint sepa-ration between treated surfaces was investigated. No significant adhesion enhance-ment between surfaces was achieved in the conducted experiments. However, in-creased resistance to separation with water was found in all cases, with copper show-ing the most significant effect. In this work, an innovative joining technology that enables the joining and separation of polymer surfaces for improved recycling without adhesives was presented. The technology integrates the joining capability into the polymer surface and has demon-strated its potential for industrial applications. Critical factors for successful joining encompass surface roughness, surface modification, the presence of ions on the surface, and joining temperature. When appropriately combined, these parameters enable strong, reversible joining between polymers, allowing easy separation by water or EDTA solutions. This research explores a new direction with considerable implica-tions for the polymer and adhesive industry, supporting polymer recycling and foster-ing sustainability. To further advance the technology developed in this study, future research should focus on broadening the range of polymers and separation methods, improving the hot pressing process, refining adhesion models, investigating alternative ligands and grafting techniques, optimizing adhesion strength and separation capabilities using metal ions and nanoparticles, improving the atmospheric plasma grafting process, and demonstrating technology transferability into applications.

The fickle nature of Selective Laser Melting (SLM) makes it exceedingly difficult to anticipate the outcome of a specific print. Physical and mechanical properties of the samples fabricated via SLM largely depend on processing parameters governing the print. Slight alterations to such process parameters are infamously linked with haphazard variations in aforementioned properties. Design engineers or operators must undergo a tedious optimization process to arrive at process parameters that result in desired outcomes. In the efforts to possibly avoid expensive resources and time required for redundant trail and errors, high-fidelity predictive models must be developed for SLM.In this study, robust and reliable supervised learning models based on Gaussian Process Regression (GPR) are established to model and predict physical and mechanical properties of as-built Ti-6Al-4V alloy manufactured via SLM. Properties such as density, surface roughness parameter Ra, and hardness are modeled based on most pertinent SLM input process parameters of laser power, scanning speed, hatch spacing, layer thickness and volumetric energy density. A comprehensive dataset is collected from literature published over last 15 years. Data are trained using ten-fold cross validation technique, and Hyperparameters optimization is performed for all three GPR models. Alongside GPR, Artificial Neural Network (ANN) models are also developed for all three properties, using same cross validation technique and data. As a benchmark tool, a traditional parametric modeling technique of Multiple Linear Regression (MLR) is employed as well. This is followed by Analysis of Variance (ANOVA) for collective dataset, revealing which factors and interactions are statistically significant to the studied physical properties. Use of statistical error metrics like MAE and RSME has been made throughout this multifaceted study.Finally, actual SLM experiments are performed, and developed models are deployed to assess their performance against three physical properties of printed cubic Ti-6Al-4V samples. It was discovered that the built GPR models accurately predicted said properties for the samples, with maximum deviations of predictions being 0.95% for density, 1.47 µm for surface roughness Ra, and 16.88 HV for microhardness. GPR models also outperformed their counterpart NN models both in training and deployed phase by an acute margin, for instance, by 10% and 8% surface roughness Ra of the samples, respectively. For all three properties, MLR models proved to be subpar both the non-parametric techniques and were hence labelled incompatible to model a complex process of SLM. Some novice material characterization also revealed the defects contributing to inferior physical properties, if any. Owing to its exhaustive data collection, rigorous training mechanisms, and deployment against actual experimentations, this study is by far the most comprehensive for SLM-ed Ti-6Al-4V alloy.

The manufacturing industry is going through a complex transformation phase due to the current supply chain interruptions by the pandemic, intricate customer custom designs, and just-in-time methodology adopted by various industries. Manufacturers shift towards Industry 4.0 capable machines with expanded data analysis capabilities to tackle process disruptions. From a machine operator's perspective, the lack of advanced real-time monitoring in machining processesusing sparks such as Electrical discharge machining (EDM) and Electro-chemical discharge machining (ECDM) can lead to delayed response time in case of any mishaps. There is a need for an advanced process monitoring tool to acquire feedback in real-time and control the machining process. Digital twins can be a key in such situations. It can provide the required data across the platforms to ensure proper and timely communication between the machine, operator, and stakeholders. The work presented in this study proposes a novel model for making a digital twin of an Electrical discharge machining process.Accurate prediction of surface roughness generating capabilities of the manufacturing process is a prerequisite to enhancing their uses in areas such as surface texturing. Textured surfaces have numerous applications in various industries such as Automotive, Aerospace, Energy, and Defence. The electrical discharge machining process can be used for surface texturing of conductive materials, particularly hard surfaces. A three-step approach is used in this work to develop a digital twin model to simulate a live surface texture of surfaces created by the EDM process. The prediction is based on the three input process parameters for EDM, namely the spark-on-time, current, and voltage. Finite element method is used in the first step to generate a single crater formed by an individual spark. In the next phase, the single spark FEM data is processed and stored in a form of big data set which is then used in the third phase to plot the real-time status of the machined workpiece using live data acquisition, data analysis, and multiple spark simulations. The experimental data were used to validate the surface textures obtained from the digital twin. The Ra values tested at several spots on the experimental specimen were found to be within the value range projected by the digital twin.Thus this study demonstrates a method to implement a digital twin model of an EDM process. Successful integration of this model into industrial machines can save time and effort for the manufacturer and give economic benefits.

Concrete cracking in structures is a ubiquitous problem which can lead to the deterioration of the structure. Other than affecting the strength aspect of a structure, cracking impacts the serviceability criteria as well. Although cracking phenomenon in any structure is highly inevitable, it has to be minimized in order to maintain a structure’s life effectively. Cracking in reinforced concrete structures is related to the bond strength developed between the bar and the concrete. It also depends on an ability of the bar to resist the stresses due to shrinkage to minimize the crack. Another important aspect is the resistance offered by the reinforcement to minimize the residual crack width after withdrawal of high loads beyond or near the yielding capacity. All these parameters were considered and have been studied as a part of this dissertation through experimental testing. The variables used in the tests are the alternative coated reinforcements like textured epoxy, hot dipped galvanized, and continuously galvanized reinforcements. Variables also included uncoated (black) and conventional epoxy (smooth epoxy) reinforcements which have been used in structure for many decades. Considering all the tests conducted, an overview analysis was done to determine the best performing bar coating for crack control and rebar-concrete bond. The results show that textured epoxy bars were the best performer in 47% of tests. On the other hand, smooth epoxy bars were the worst performer in 47% of tests. Uncoated, hot dipped galvanized, and continuously galvanized bars were typically in-between textured and smooth epoxy bars in their performance. This dissertation also analytically evaluated the bond mechanics associated with the variable bar coatings considered in the experimental program. Two different models of bar force variation at and around a crack location were considered to calculate the length over which forces transfer between the bar and concrete. The calculated lengths were compared to data from an associated peer study. It is inferred from the results that a small portion of a bar is de-bonded adjacent to the cracks and the forces transfer gradually at locations beyond the debonding. This inference applies to all the bar coatings in the data except the continuously galvanized reinforcement. Conclusions for continuously galvanized reinforcement could not be made because of limited and randomness in the data.

The mechanical properties of metal additively manufactured parts are often inferior to those of their traditionally manufactured counterparts. These inferior mechanical properties are mostly attributed to prevalent defects inherent to additive manufacturing processes, thus resulting in reduced performance and durability of the additively manufactured parts. Additive manufacturing processing parameters and post-processing techniques have been studied to determine the optimal conditions for improving the mechanical properties of additively manufactured parts. In this work, the effects of four heat treatment schedules and three build directions were studied on the material microhardness, surface roughness, and surface porosity of selective laser melted 15-5 precipitation hardened stainless steel dog bone test samples. Vickers microhardness test was conducted to obtain hardness values for each test sample. Contact and non-contact type methods were used to determine the surface roughness of every test sample. Microscopic imaging was used to detect and quantify the surface porosity of each test sample. The experimental data was analyzed using an ANOVA test. The heat treatments affected the material hardness of the test samples, raising the Vickers hardness value for all test samples subjected to any heat treatment. The build direction affected the surface porosity of the test samples. Test samples manufactured in the X-build direction experience a greater surface porosity than test samples built in other orientations. The surface roughness was unaffected by either heat treatment or build orientation.

Large area organic electronics are multilayer devices fabricated by solution processing of different organic semiconductor molecules. However, the main challenges for the solution processing techniques are the erosion of the previously deposited layer by the solvents used for the subsequent layer deposition, interfacial mixing, and formation of uneven interfaces and surfaces, all of which significantly reduce the device performance. Herein we demonstrate a photopolymerizable bis-diazirine-based crosslinker molecule capable of converting soluble organic materials into highly cross-linked insoluble networks, alleviating the inter-layer mixing problems. Upon 5-20 min irradiation with long wavelength/low power UV (1.8 mW/cm2) bis-diazirines results in the formation of carbenes that react via carbon-hydrogen bond insertion with polymers or small-molecules yielding cross-linked networks. This photo-generated crosslinking does not require any catalyst, initiator, or short-wavelength UV light and is performed at room temperature, releasing molecular nitrogen as the only byproduct. To study the effectiveness of bis-diazirine-mediated photo-crosslinking in this dissertation we have described the design, synthesis, and characterization of the bis-diazirine crosslinker molecules, studied their photochemical and photophysical properties, fabricated functional OLED devices and finally, evaluation of the OLEDs performance.

The manufacturing sector is among the fastest-growing in today's industrialized world. Manufacturers are concerned about increasing their competitiveness and profitability. Increasing the efficiency and sustainability of manufacturing processes is one way to improve productivity and improve profit margins. Learning about cutting conditions and how they affect machined surfaces and tool life can help improve productivity. Nowadays, the goal is not just to increase productivity but also to make processes more environmentally friendly and cleaner. This research aims to analyze the machinability of difficult-to-cut magnesium alloys through different cooling and lubrication strategies and their impact on the environment. This study conducted controlled machining tests with dry and vegetable oil mist cutting settings to measure surface roughness, tool contact length, chip morphology, and flank wear. The present study provides insight into the cutting performance of coated carbide tools. To improve the machinability of magnesium alloys, the study also investigated tool wear mechanisms, surface roughness, and primary and secondary components of machining, such as effective shear angle, compression ratio, and coefficient of friction. In this study, we found that minimum quantity lubrication (MQL) performed well under various speed ranges for coated tools. Cutting speed and feed rate correlated closely with tool wear, surface roughness, and other output response parameters. MQL-based systems offer great potential to improve the machinability of magnesium alloys, and they should be explored further.

Every moment of every day, at least hundreds of thousands of tires roll across a surface throughout the world. Tires are indisputably important in our daily life. The tire's primary component is rubber, which consumes energy when it rotates on a substrate due to the viscoelastic material's internal friction: a phenomenon referred to as rolling resistance. The interaction between the tire and the road surface is one of the most intricate and crucial phenomena in an automobile, because it is responsible for creating forces, moments, and deformation in the tire. Additionally, the road's roughness interacts with the tire and contributes significantly to its performance. This dissertation aims to develop a comprehensive physics-based model for predicting the rolling resistance of a viscoelastic material due to dynamic deformations caused by tire rotation using an analytical approach. The model was developed by proposing a Gaussian wave function propagating across a tire circumference's viscoelastic medium. The wave function was selected to describe the displacement field produced by tire-road interaction. Additionally, by adopting a multi-scale modeling technique, the model was upgraded to estimate rolling resistance while taking into account surface roughness at all length scales, from macroscopic to microscopic. Additionally, another mathematical model was developed using the Fourier series approach to evaluate the steady-state stress response and energy dissipation for any harmonic and non-harmonic periodic strain signals. Additionally, the dissertation strove to build a continuum damage mathematical model using a combined testing/modeling methodology to predict the aging of Styrene-Butadiene Rubber (SBR) after continuous exposure to the atmosphere. The obtained model was developed through the implementation of optimization techniques while formulating a mathematical model, which was then combined with a physics-based model to predict rolling resistance while taking into account rubber aging. Calibration of hyperelastic and viscoelastic material models with testing data was performed using an optimization technique that yielded sufficient results. The results of all mathematical models obtained in this dissertation are reported subsequently. The stress response of a viscoelastic material under harmonic and non-harmonic strain input yielded good agreement with the FEA model obtained using ABAQUS. The rolling resistance behavior under various operating conditions, including texture and aging effects, was reported, and the results aligned with the experimental results found in the literature.

One of the most important forest functions in the mountains is the protection capacity, safeguarding many people and their infrastructure against natural hazards. The attention on forest protection capacity complements other topics (e.g. related to post-disturbance dynamics in mountain forests) discussed in all the presented papers. This thesis aims to improve our knowledge on representation of changing forests and vegetated areas in avalanche simulations, and on the post-disturbance forest development after two typical Central European disturbance agents: bark beetle and windthrow. In the beginning of this thesis I compared various remote sensing methods (lidar and photogrammetry) for determining forest parameters (as tree height, crown cover or surface roughness), to the field investigation in total of 107 plots. These parameters were further used in avalanche simulations using the simulation tool RAMMS (Paper 1). The use of lidar or photogrammetry to estimate forest parameters as input for avalanche simulation proved appropriate, as the simulated runout distances did not differ significantly from the observed runout. The correct estimation of forest cover in release areas using photogrammetry was challenging but crucial as it may strongly affect the simulated runout distance of avalanches. The input data for this estimation should be as recent as possible in order to avoid an incorrect estimation of forest cover influencing the avalanche simulation. The precise estimation of forest cover in avalanche release areas is particularly important in the treeline ecotone (where sparse vegetation may be neglected in avalanche simulations) and in disturbed forests (which are expected to increase). Treeline ecotones and disturbed forests with high surface roughness have thus potentially important effects on avalanches. We thus tested several roughness algorithms in order to improve the quantification of terrain roughness in treeline ecotones and disturbed forests (Paper 2). The algorithm vector ruggedness measure was selected based on our analysis as the best performing algorithm in distinguishing between different roughness classes. We also proposed an improvement for roughness in gullies, which are typically overestimated in hazard modelling. To overcome this issue, we proposed to adopt the directional roughness, which may be applied using e.g. the algorithm standard deviation (SD) of residual topography, calculating surface roughness in the direction of flow. Surface roughness maps, based as well on digital surface models (DSMs), may serve as a good basis to improve natural hazard modelling. The two following papers aimed at better understanding the disturbance dynamics in forests impacted by bark beetle infestation (Paper 3) and windthrow (Paper 4). Post-disturbance forest development was studied in the field examining parameters on deadwood and tree regeneration (e.g. number of trees, tree species, tree height, deadwood cover, decay stage of deadwood). As deadwood decays, trees are growing taller and denser. Thirty years after both disturbances, forests showed good recovery. Based on our analysis, the future forest is expected to be more diverse with higher shares of broadleaves and with different age classes thanks to secondary tree regeneration growing on deadwood. Since trees establish only on rather decayed deadwood, this regeneration comes after at least 20 years from disturbance. Furthermore, the protection capacity was monitored over the years. We used the surface coverage of deadwood and trees creating surface roughness as a proxy for the protection capacity. After the bark beetle disturbance, we also assessed the protection capacity using avalanche simulations (modelled with RAMMS) based on remote sensing data. We observed that disturbed forests maintain their protection capacity for some time. In the case of windthrow through high surface roughness created by large amounts of lying deadwood and root plates, and in the case of bark beetle by long-standing dead trees. The protection capacity reaches its minimum after 10-15 years after disturbance with slight delay in the case of bark beetle infestation, as the decay proceeds slower. Remote sensing methods serve for different purposes and are suitable in delivering products like digital models. Such models are valuable in estimating forest parameters, calculating surface roughness or as a basis for avalanche modelling. Surface roughness calculated from DSM may represent some of the underestimated forest areas as young and shrub forests or changing forests and, therefore, improve the estimation of protective capacity of such areas. Analysis of data from repetitive fieldwork after bark beetle and measuring forest parameters at different stages after a windthrow revealed that the minimum in protective capacity is reached at similar time after these two common forest disturbances. It remains to be verified if remote sensing methods as photogrammetry, are able to deliver similar data on tree regeneration and deadwood, which are often being overgrown by other vegetation; and in case of lidar method the possibility of automatic object segmentation and extrapolation over larger areas.

Additive manufacturing continues to have problems with porosity, surface quality, and residual stress. This two-part study focuses on (1) employing a non-detrimental technique to measure the resulting mechanical properties in additive manufacturing, namely residual stress and microhardness, and (2) improving the print quality in metal additive manufacturing by analyzing porosity formation and surface roughness, especially for overhanging structures. This work presents the first known study utilizing hybrid additive manufacturing as a machining-based sensor to measure mechanical properties. Also, this work investigates the effects of print process parameters within Lumex CAM (Matsuura Lumex Avance-25) on porosity formation and surface topography. The results indicated that the variation of the net cutting specific energy correlated with the residual stress in the first millimeter as well as the microhardness across the build. X-ray CT results and laser profilometry revealed that porosity formation and surface topography were controlled by the melt pool dimensions and the print strategy. In addition, one mechanism explaining the alignment of pores across the build was the position of the recoater according to the gas flow during printing. Advisor: Michael P. Sealy

Additive friction stir deposition (AFSD) of AZ31B magnesium alloy was conducted to examine evolution of grain structure, phases, and crystallographic texture. AFSD was carried out using a hollow tool made from tool steel at a constant rotational velocity of 400 rpm on the AZ31B base plate. Bar stock of AZ31B was utilized as a feed material. The linear velocity of the tool was varied in the range of 4.2-6.3 mm/s. The feed rate of the material had to be maintained at a half value compared to the corresponding linear velocity for the successful deposition. The layer thickness and length of the deposits were kept constant at 1 mm and 50 mm respectively. The tool torque and actuator force values were recorded during the process and for calculation of the average input energy for each processing condition. Temperature during the AFSD experiments was monitored using a type k thermocouple located 4 mm beneath the deposition surface at the center of the deposition track. The average input energy values showed a decreasing trend with increasing tool linear velocity. The temperature values during deposition were ∼0.7 times the liquidus of the alloy. The deposited material then was examined by laser microscope and profilometer, X-ray diffraction, scanning electron microscopy, electron back scatter diffraction (EBSC), contact angle measurement and micro hardness tests. The AFSD AZ31B samples showed reduction in areal surface roughness with an increase in the tool linear velocity. The X-ray spectra revealed increase in the intensity of prismatic planes of α-Mg phase with increase in tool linear velocity. AFSD of AZ31B Mg alloy resulted in shifting of the grain size from a broader and courser distribution within the feed material to a tighter distribution. Moreover, EBSD observations confirmed the refinement in grain size distribution as well as the presence of predominantly prismatic texture for the AFSD samples when compared to the feed material. There was a marginal improvement in the hardness for the AFSD samples compared to the feed material. However, there was no significant change in the contact angle measurements in simulated body fluid for the AFSD samples compared to the feed material. The current work demonstrated ability of AFSD technique for the additive fabrication of magnesium-based alloys and provided a methodology for examining various process attributes influencing the processing-structure-property relationship.

Despite considerable progress made over recent decades in scientific understanding of the structure, evolution, and dynamics of supercell thunderstorms and tornadoes, there are still aspects of their evolution, including tornadogenesis and decay, that have yet to be understood. One area in which scientific understanding is particularly incomplete is how land surface heterogeneity or complex topography interacts with and/or affects tornadoes. Past investigations embarked on the endeavor to quantify the relationship between tornado events with land cover or elevation, with inconclusive or conflicting results. The purpose of this study is to identify the genesis and decay points of tornadoes over an eighteen-year timeframe of 2000-2017 within the state of Arkansas and a ten-year timeframe of 2008-2017 within the State of Oklahoma to determine whether elevation and/or surface roughness of the nearby land cover relative to the broader landscape might impact these events. This study was completed utilizing Storm Prediction Center tornado reports, National Land Cover Data, and USGS digital elevation models (DEMs), with ArcGIS Pro and Microsoft Excel as the modes of data visualization and analysis. A combination of buffer analyses, Mann - Whitney U tests and Getis-Ord Gi* hotspot analyses were incorporated to assess the relationship between genesis/dissipation locations and surface roughness and complex terrain. The qualitative and quantitative results herein suggest a local increase in surface roughness heterogeneity favors genesis events, while regions defined by complex terrain may act to dissipate tornado events. Furthermore, hotspot analyses suggest regions with complex terrain and increased roughness values favor tornado activity.

Cellulose is an abundant and naturally occurring biopolymer that has been used by humans for food, shelter, and clothing for about two centuries now. Highly crystalline nanoparticles derived from cellulose, called cellulose nanocrystals (CNCs), show great potential to meet the rising need for sustainable and nontoxic materials for biomedical applications. However, multiple biomedical applications of CNCs, such as those involving their use in tissue engineering scaffolds, require CNC-based structures to be stable in aqueous environments, a property that native CNCs do not possess due to their inherent hydrophilicity. Chemical crosslinking of CNCs addresses this issue by providing aqueous stability to CNC-based structures, by facilitating the formation of covalent linkages between cellulose molecules as well as strong intramolecular H bonding in the network. CNCs can be obtained from multiple sources such as cotton, wood, hemp etc. and properties of CNCs depend on the cellulosic source and process conditions used for extraction. However, how these source-based differences in properties impact the way CNCs crosslink with different crosslinking agents and the resulting properties of crosslinked CNCs is still unknown. This study focuses on evaluating the effect of wood source on the physicochemical properties of crosslinked CNCs. Key biomedical applications for which CNCs are a promising material are discussed and the physicochemical and mechanical properties of crosslinked CNCs that render them attractive for such applications are closely examined. The results via dynamic light scattering (DLS), zeta potential measurement, rheology, Fourier transform infrared spectroscopy (FT-IR), and atomic force microscopy (AFM), provide insight into how the wood source influences the physicochemical properties of crosslinked CNCs. The study also highlights the significance of these differences and the potential for tuning crosslinked CNCs’ material properties for particular applications.

Industrial energy consumption accounts for 35% of all energy consumed in the United States andenergy consumed by machine tools in manufacturing processes contributes a significant portion to the inefficiencies in manufacturing energy consumption. However, there are only few energy efficiency models for machine tools which also include product quality. Therefore, this research investigates the hypothesis that physics-based models of machine tools and processes lead to more energy-efficient machine tool design. Furthermore, the research will focus on abrasive machining, primarily using grinding machines and will highlight the quality aspects of finished workpieces. The research then addresses the following research tasks. 1) to analyze the energy efficiency of grinding machine tool components. This assessment included applying the axiomatic design methodology to identify those machine tool components, and then creating physics-based models of those components. Use of these models will allow designers to easily calculate energy consumption of a machine tool feed system. 2) To model grinding machine motors for energy consumption in the manufacturing and use phases. This work included performing a literature review of the life cycle inventory models of electric motors, and creating an embodied energy model using the review. This also included performing a study of the energy consumption of a grinding spindle, to identify start-up times for minimum energy consumption and minimum peak power. The two tasks highlighted can be used by machine designers to first determine the embodied energy of their design for energy tradeoff analyses, and second to reduce energy and peak power during the use phase. 3) To investigate the correlation between machine tool energy consumption and workpiece quality. This work included performing a study on energy consumption and resulting surface roughness of grinding steel using cold air for coolant. It was identified that a correlation does exist, that higher energy consumption is correlated with lower surface roughness.

This thesis investigates the effect of different factors on Carbon Fiber Reinforced Polymers (CFRP) milling, like feedrate, tool material, and cutting speed. CFRP offers excellent material properties, which led to the increase of the material in today's manufacturing industry. CFRP offers up to 2.25 times steel's modulus of elasticity at about a fifth of the weight and excellent thermal properties, which allow the use of this material in applications with high heat like automobiles. Many industries have implemented the use of CFRP in their applications, like airplanes and automobiles, which lead to a decrease in weight and increase in strength. A literature review was conducted to determine the research gap, which resulted in 132 articles, of which 72 were relevant. The literature review results showed no specific machine settings were recommended, and neither was the type of material to use. Almost all reviewed articles used different tool materials and machine settings, with little work done in comparing various tools and settings regarding surface roughness and dimensional accuracy. A CNC mill was used to make slots in a CFRP workpiece using different combinations of the factors listed above. An initial experiment was conducted to determine the optimal toolpath, using Autodesk Fusion 360, that achieves the highest accuracy and lowest surface roughness. The slots were then analyzed using a profiler and a digital caliper to determine which toolpath to use for the experiment. After determining the toolpath, the factor level determination was conducted. Four different tool coatings were tested at three different levels of feedrate and depths of cut on a Tormach PCNC 1100. Multiple bits were used to reduce the effect of tool wear. Data was then collected on the slots' accuracy and surface roughness using a digital caliper and the Dektak XT Stylus profilometer, respectively. The data obtained were then analyzed in JMP to determine the optimal settings to mill CFRP. The analysis showed feedrate, tool coating, depth of cut, and their interaction effects have a significant effect on dimensional accuracy and surface roughness.

The relationship between varying contour settings and part geometry provides insight into the attainable surface roughness and dimensional accuracy of parts fabricated in 17-4 stainless steel via selective laser melting (SLM). Varying the contour settings of laser power (W), scan speed (mm/s), and beam offset (mm) for unsupported inclined bars. The utilization of a coordinate measuring machine (CMM) and surface profilometer quantified the dimensional accuracy and average surface roughness (Ra) for upface, downface, and topface surfaces. Adjusting the laser power and scan speed had minimal affect to surface roughness compared to part geometry. Part dimensionality was affected by the incline angle, laser power, and scan speed. Lower energy densities (J/mm) resulted in over-sized parts, while higher energy densities resulted in undersized dimensions. A clear relationship between varying contour settings and part geometry with the dimensionality and surface roughness of 17-4 fabricated benchmark parts was found.

This thesis examines the influence of ice accretion on the bridge stay cables on the vortex shedding frequency and the lift and drag coefficient of the cables. Vibration of the stay cables due to wind is observed in many cable-stayed bridges. This vibration of stay cable may lead to fatigue in the cables and damage to the cable attachments. Therefore, it is important to understand the vortex shedding and aerodynamic behavior of iced stay cables. The present work explores the two-dimensional approach to study the aerodynamic coefficients and vibration frequency of the cable with ice accretion where the iced cable is simplified as a two-dimensional cross-section with ice profile and roughness applied on the iced area of cable while the remaining part of the cable is smooth. In the current study, the k-ω SST turbulent model in ANSYS-Fluent is used to solve the transient 2D Navier-Stokes equation. PISO is selected as a solution algorithm for pressure-velocity coupling equation. The first part of this thesis deals with the study of vortex shedding and lift and drag coefficients of cable sections with seven different ice accretion profiles. Due to icing, the vortex shedding frequency of the cable decreases by up to 15%. The drag coefficient of the iced cable section increases by up to 61% from smooth cable. The lift coefficient of iced cable increases by up to 58%. When ice accretion is not symmetrical about y=0, the lift coefficient oscillates in the direction of the side of the cable where ice accretion present. In the second part of this thesis, the influence of the thickness of ice accretion is studied; it is found that both the value of the drag coefficient and the range of the lift coefficient decreases with an increase in ice accreted thickness with the drag coefficient decreases by up to 20% and lift coefficient decreases by up to 58%. However, the ice accretion thickness causes little change in the vibration frequency. The final part deals with the application of different values of roughness height in the simulation. An increase in roughness height caused the drag coefficient to decrease by as much as 3%, the lift coefficient and vortex shedding frequency remain constant. Overall, it is observed that the maximum ranges for the percent change in the value of the drag coefficient, lift coefficient, and vibration frequency were -21% to 61%, -58 % to 58%, and -15% respectively: these changes are different for different icing profile, thickness of ice accumulation, and icing roughness heights.

Unconventional energy such as coal seam gas has the potential to be a supplemental resource for global energy demand and is primarily stored in low-permeability coal seams by adsorption. Many countries have invested significant research efforts in this unconventional energy source. However, problems still exist in the production of coal seam gas such as the rapid decline of production rate, low recovery ratio, etc.. The basic mechanism of gas transport in coal has an important influence on the productivity and longevity of the coal seam gas wells. To our best knowledge, the permeability for gas flow in coal is mainly controlled by the heterogeneous microstructures of the coal matrix and cleat systems. To study the behaviour of methane transport from the matrix to cleats in coal, many factors are involved, such as gas adsorption/desorption, Klinkenberg slippage, heterogeneous porous structure, surface roughness, etc. However, up to date, no existing experimental and numerical method is available for direct investigation of multiscale and multiphysics processes of coal seam gas transport in the heterogeneous structures of coal. In this Thesis a numerical solver is developed that solves the multi-scale and Multiphysics reaction-advection-diffusion problem of gas flow through narrow and rough cleats. The approach considers a fractal rough surface of the cleats, gas slippage in narrow cleats, complex cleat topology, ad/desorption reactions on pore surfaces and diffusion through the coal matrix. The simulator developed in this Thesis is implemented via the immersed boundary-lattice Boltzmann method for modelling coal seam gas transport in complex structures. The numerical implementation has been benchmarked by the comparison with published data and/or analytical solutions and achieved good agreements. The presented method has shown to be an efficient numerical solver for such multiphysics problems coupling fluid dynamics, diffusion and chemical reactions and can also be applied to unconventional shale gas and enhanced geothermal systems in which similar challenges exist that have not yet been resolved.

This study was conducted to evaluate the effect of surface finish on spur gear power losses under jet lubrication. Four different surface finish combinations were tested: (i) hard ground surface pair, (ii) chemically polished surface pair, (iii) super honed surface pair and (iv) hard ground against chemically polished surface pair. The test was conducted at 432 different operating condition combinations of speed, torque, lubricant type and inlet temperature. An FZG back-to-back set up was used to conduct the test. Surface roughness inspections were carried out at regular intervals to monitor any changes in surface roughness characteristics. The measured power losses were resolved into spin (load independent) and mechanical (load dependent) power losses. The relation between both losses and various operating conditions were explored. As expected, spin power loss did not vary with variation in surface finish. Mechanical power loss increased with increase in speed and torque. Various surface roughness and operating parameters such as BAC curves and lambda ratio were calculated for each surface finish combination to study their correlation to power losses measured. For smoother surfaces, an increase in temperature decreased power loss as the viscosity of the lubricant decreased and hence rolling friction losses dominating the mechanical power loss decreased. However, for rougher surfaces sliding friction losses seemed to be dominant due to high amounts of asperity contact. Thus, more cases of higher power loss at high temperatures were observed for rougher surfaces.

The purpose of this study was to better define how quality in terms of surface quality, dimensional accuracy, consistency/repeatability, and total build time vary based upon 3D printers in different cost levels. One FDM printer was chosen at cost levels of entry level, intermediate level, and commercial level. A test block with various raised and recessed geometrical shapes was printed on each printer to analyze average surface roughness, dimensional accuracy, consistency/repeatability and total print time. When comparing the results, the most significant advantage with increased printer cost was the decrease in total print time. The commercial level printer, the Fortus 450, had a decrease in total build time to less than a fifth of the intermediate level printer, the 3D Platform printer. The 3D Platform decreased build time by nearly half as compared to the entry level printer, the MakerBotz 18s. Dimensional accuracy did not vary significantly between the printers, but the Fortus 450 did show the best consistency and repeatability. As far as surface roughness, the least rough measurements were taken on the test block side in the direction of increased layer height, while the measurements taken on the test block bottom/top in the direction parallel to the printer build plate, were roughest. When comparing surface roughness by printer there was not significant difference, but the Fortus 450 visually showed more consistent surface quality with minimal or no gap in the filament beads and also showed very consistent surface roughness measurements in three directions. Based upon the results when choosing a 3D printer as the cost increases, the driving factors appear to be total print time and consistency in accuracy and surface quality but in general, the best printer to choose is based upon how cost, surface quality, dimensional accuracy, consistency/repeatability, and total print time are ranked based upon the project.