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Electric discharge machining (EDM) routehas capability of machining hard materials. Even intricate shapes can be machined by this process. Traditional machining routes develop machining issues like tool wear and pitiable surface finish. It can be overcome by the EDM process. The objective of this work is to prepare AA6351-10wt%Al2O3-5wt%Gr composites through stir casting process. The manufactured composites were machined via EDM route and their machining characteristics material removal rate (MRR) and surface roughness (SR) were studied via Taguchi process. The results display that for MRR current is the major influencing parameter and for SR voltage is the foremostpersuading parameter.

The tool and die applications are preferred the unconventional machining processes as they are popular in machining the difficult to cut type complex contour/ profile. The complex profile machined on hard material. Some special materials like Stainless Steel 12X18H10T withstand its inherent properties even it exposes at higher temperature. This investigation aims to expand its application by investigating its machinability in Electro Chemical machining process for surface finish. The process parameters like gap between work material and tool, discharge current, concentration of electrolyte and applied voltage at three levels. The Taguchi approach is used for optimizing the process parameters and confirmation runs also conducted for developing the mathematical modelling. For optimizing number of experiment the Taguchi L9 is utilized for this investigation.

Titanium alloy is difficult to machining in the conventional machining process. Hybrid production technology for abrasive water jet machining (AWJM) allows the machining of all engineering applications. This paper explores the optimization of the process variables of Titanium alloy AWJM (Ti- 6Al- 2Sn- 4Zr- 2Mo). The AWJM process parameters such as water jet strength, traverse speed, and standoff distance were studied against the material removal rate, surface roughness, kerf angle. The contribution of this parameter to responses has been calculated by variance analysis. For material removal rate, surface roughness, kerf angle, regression models were obtained.

Nowadays, the additive manufacturing process had significant attention due to its great advantages that are being used for developing products and producing prototypes. This technology overcomes the various drawbacks of existing techniques and it becomes the most efficient approach. In the industrial sector, this technology is most important for individual designing products and extended with different functions. The performance of additively manufactured parts, on the other hand, is largely influenced by their surface integrity and dimensional accuracy. The surface integrity is an important issue because the additively manufactured products are affected by staircase effects resulting from layer-by-layer manufacturing. The rapid prototyping contains multiple methods such as VAT Photopolymerization and Poor surface quality is caused by the staircase effect in all additive manufacturing processes so therefore, the various post-processing efforts and controlling different process parameters of additive manufacturing are necessary on the produced component for improving surface quality and reducing surface roughness. To focus on improving the finish of an additively manufactured part's surface, there are numerous methods presented. This research described the various existing approaches of surface finishing with various efficacies such as reduction of surface roughness value, mechanical strength, and dimensional accuracy. Current post-processing methods for improving the surface characteristics of additively manufactured parts are discussed, with a classification based on the processes' mechanisms.

In this study, Mg–6.0Zn–3.0Sn–0.5Mn (ZTM630) magnesium alloy was pre-activated by colloidal Ti, oxalic acid, and phosphoric acid, and a phosphate conversion coating (PCC) was prepared on the alloy surface. The morphology and corrosion resistance of the prepared PCCs were investigated. Surface morphology studies showed that the phosphate crystals that formed the coating were the smallest for the sample pre-activated by phosphoric acid. The coating on the colloidal Ti and the phosphoric acid samples had the largest and the smallest thickness and surface roughness, respectively. The reason for the discrepancy was analyzed by comparing the surface morphologies of alloy samples immediately after the pre-activation treatment and various phosphating treatments. X-ray diffraction analysis revealed that all three PCCs contained the same compounds. The corrosion resistance time from the copper sulfate drop test and the electrochemical data from the potentiodynamic polarization curves showed that the coating pre-activated by phosphoric acid had the best corrosion resistance. Finally, the 1500 h neutral salt spray corrosion test confirmed that the phosphating treated magnesium alloy, which was pre-activated by phosphoric acid, exhibited excellent corrosion resistance and behavior.

Ti6Al4V is widely applied in the integral cascades of aero engines. As an effective machining method, electrochemical trepanning (ECTr) has unique advantages in processing surface parts made of hard-to-cut materials. In ECTr, the state of the flow field has a significant effect on processing stability and machining quality. To improve the uniformity of the flow field when ECTr is applied to Ti6Al4V, two different flow modes are designed, namely full-profile electrolyte supply (FPES) and edges electrolyte supply (EES). Different from the traditional forward flow mode, the flow directions of the electrolyte in the proposed modes are controlled by inlet channels. Simulations show that the flow field under EES is more uniform than that under FPES. To further enhance the uniformity of the flow field, the structure of EES is optimized by modifying the insulating sleeve. In the optimized configuration, the longitudinal distance between the center of the inlet hole and the center of the blade is 6.0 mm, the lateral distance between the centers of the inlet holes on both sides is 16.5 mm, the length to which the electrolyte enters the machining area is 1.5 mm, and the height of the insulating sleeve is 13.5 mm. A series of ECTr experiments are performed under the two flow modes. Compared with EES, the blade machined by FPES is less accurate and has poorer surface quality, with a surface roughness (Ra) of 3.346 μm. Under the optimized EES, the machining quality is effectively enhanced, with the surface quality improved from Ra = 2.621 μm to Ra = 1.815 μm, thus confirming the efficacy of the proposed methods.

Objectives Magnesium alloys are the potential candidate for metallic implants due to their excellent mechanical characteristics, biodegradable nature, and properties similar to human bone. However, a high degradation rate is primary obstacle in implementing these alloys as biodegradable orthopedic implants. Powder-mixed electric discharge machining (PMEDM) is an emerging method of surface modification of metallic alloys that can be implemented to improve the corrosion resistance of Mg alloys. Therefore, PMEDM using zirconium (Zr) and manganese (Mn) powder particles has been proposed to modify the surface characteristics of Mg-4Zn alloy. Materials and Methods In the present work, Zr and Mn powders have been used in varying concentrations during PMEDM of Mg-4Zn alloy. Experiments were conducted as per mixed design L18 orthogonal array (OA). Taguchi and Grey Relational Analysis (GRA) have been used to optimize the process parameters. Analysis of response characteristics, namely material removal rate (MRR), surface roughness (SR), and thickness of the alloyed layer (TAL), has been carried out at different values of input variables (like powder additives (Pa), powder concentration (Cp), peak current (Ip), pulse on time (Ton) and duty cycle (DC)). The corrosion analysis was carried out by immersing the specimen (machined at an optimized setting) in simulated body fluid (SBF). Results It is observed from the analysis that Cp, Ip, and Ton play a pivotal role in evaluating response characteristics. The favorable setting suggested by the gray approach is Pa: Zr; Cp: 2 g/l; Ip: 4A; Ton: 50 μs; DC: 80%, while responses at this setting are confirmed by confirmation experiments with MRR: 32.14 mm3/min; SR: 5.578 μm and TAL: 8.28 μm. The immersion test signifies that the corrosion rate (CR) of PMEDMed sample (3.20 mm/year) is 40.74% lesser than the corrosion rate of polished sample (5.40 mm/year). Conclusion Zr powder shows better performance in terms of higher MRR, lower SR and higher TAL as compared to Mn powder during the PMEDM process. The corroded surface of polished sample exhibited larger size micro pits and cracks than the machined sample, which concluded that surface modification of MZ-4Zn alloy via PMEDM is a powerful tool to enhance its corrosion resistance.

The surfaces of soil grains are not perfectly smooth, especially examined at small scale. In geotechnical engineering, surface roughness has been found to be able to influence the inter-particle friction angle at micro scale and small-strain stiffness at macro scale. However, the quantity and quality of the studies on surface roughness of natural soils are still limited. In this study, the evolution of surface roughness of natural sand grains with increasing normal load was investigated by a single-particle compression apparatus. Thirty Leighton Buzzard sand (LBS) grains coarser than 2·36 mm were tested, and the surface roughness was measured before and after compression by an optical interferometer. The deformations of the asperities and of the bulk of the sand grains in the vicinity of the contact were mapped. Three stages were identified as the normal load increased: (a) plastic deformation of the asperities; (b) asperities and bulk plastic deformation; and (c) bulk only plastic deformation. At very small normal load, only the asperities were found to deform plastically, and the surface roughness of the sand grains decreases due to the flattening of the asperities. Within this regime, the load–displacement relationship of LBS grains under compression could be simulated by the modified Hertz model, which takes surface roughness into consideration. With increasing normal load, the bulk of the sand grains began to yield near the contact. The geometry of the surfaces of LBS grains in contact with the loading platen is the main factor that influences the plastic deformation of the bulk. Differently from the plastic deformation of the asperities, the plastic deformation of the bulk could both smoothen and roughen the surfaces. When plastic deformation of the bulk occurred, both Hertz and modified Hertz theory could not predict the load and displacement relationship of sand grains. Through analysing the cumulative distributions of surface roughness of 30 LBS grains at different normal loads by the Weibull function, the surface roughness was found to decrease dramatically with increasing normal load at first and then tended to be constant.

Additive manufacturing (AM) is an advanced manufacturing process that provides the opportunity to build geometrically complex and highly individualized lightweight structures. Despite its many advantages, additively manufactured components suffer from poor surface quality. To locally improve the surface quality and homogenize the microstructure, friction stir processing (FSP) technique was applied on Al-Si12 components produced by selective laser melting (SLM) using two different working media. The effect of FSP on the microstructural evolution, mechanical properties, and corrosion resistance of SLM samples was investigated. Microstructural investigation showed a considerable grain refinement in the friction stirred area, which is due to the severe plastic deformation and dynamic recrystallization of the material in the stir zone. Micro-hardness measurements revealed that the micro-hardness values of samples treated using FSP are much lower compared to SLM components in the as-built condition. This reduction of hardness values in samples treated with FSP can be explained by the dissolution of the very fine Si-phase network, being characteristic for SLM samples, during FSP. Surface topography also demonstrated that the FSP results in the reduction of surface roughness and increases the homogeneity of the SLM microstructure. Decreased surface roughness and grain size refinement in combination with the dissolved Si-phase network of the FSP treated material result in considerable changes in corrosion behavior. This work addresses the corrosion properties of surface treated additive manufactured Al-Si12 by establishing adequate microstructure-property relationships. The corrosion behavior of SLM-manufactured Al-Si12 alloys is shown to be improved by FSP-modification of the surfaces.

Assembly interfaces, the joint surfaces between the vertical tail and rear fuselage of a large aircraft, are thin-wall components. Their machining quality are seriously restricted by the machining vibration. To address this problem, an in-process adaptive milling method is proposed for the large-scale assembly interface driven by real-time machining vibration data. Within this context, the milling operation is first divided into several process steps, and the machining vibration data in each process step is separated into some data segments. Second, based on the real-time machining vibration data in each data segment, a finite-element-unit-force approach and an optimized space–time domain method are adopted to estimate the time-varying in-operation frequency response functions of the assembly interface. These FRFs are in turn employed to calculate stability lobe diagrams. Thus, the three-dimensional stability lobe diagram considering material removal is acquired via interpolation of all stability lobe diagrams. Third, to restrain milling chatter and resonance, the cutting parameters for next process step, e.g., spindle speed and axial cutting depth, are optimized by genetic algorithm. Finally, the proposed method is validated by a milling test of the assembly interface on a vertical tail, and the experimental results demonstrate that the proposed method can improve the machining quality and efficiency of the assembly interface, i.e., the surface roughness reduced from 3.2 μm to 1.6 μm and the machining efficiency improved by 33%.

Aeolian sandy lands are widespread and desertification is recognized as one of the main environmental issues in the Yarlung Zangbo River valley, southern Tibetan plateau. The surface microtopographic variations induced by the near soil surface characteristics of plant communities are important compositions of land surface roughness, which likely influence wind erosion. This study was conducted to quantify the effects of typical vegetation restoration on land surface roughness on the aeolian sandy lands, and to identify the main influencing factors of land surface roughness in the Yarlung Zangbo River valley. Two bare sandy lands (as controls) and eight vegetated sandy lands with different restoration communities and ages were selected, and land surface roughness (LSR), as represented by surface microtopographic variations in this study, was measured by photogrammetric surveys. The results showed that LSR significantly increased by 7.9–16.8 times after vegetation restoration on the aeolian sandy lands, and varied among different restoration communities and ages. The mostly restored communities of Sophora moorcroftiana and Populus L. had greater LSR as compared to Artemisia wellbyi and Hedysarum scoparium. With succession from 6 to over 30 years, LSR gradually increased in the Sophora moorcroftiana restored sandy lands, but decreased in the Populus L. restored sandy lands. The variations of LSR were mainly attributed to the differences in near soil surface characteristics of vegetation (plant stem diameter and coverage, and plant residue density) and biological soil crusts (coverage and thickness). Mixed plantation of Populus L. and Sophora moorcroftiana was considered as the best restoration communities because of their effectiveness in increasing land surface roughness on the aeolian sandy lands in the Yarlung Zangbo River valley. The results would facilitate the understanding of the benefits of vegetation restoration in controlling wind erosion on the aeolian sandy lands.

A series of large scale direct shear experiments is used to investigate the effect of the geomembrane (GMB) surface roughness, geotextile (GTX) properties, and GTX ageing, on the GMB-GTX interface shear behaviour. Interfaces involving smooth, coextruded textured, and structured surface GMBs underlying four different nonwoven needle-punched staple fibres (GTXs) with mass per unit areas between 200 and 2400 g/m2, and a geocomposite drain (GCD) are examined at normal stresses between 250 and 1000 kPa. The results showed that the interlocking between the GMB and GTX increased with increasing the GMB asperity height and/or decreasing the mass per unit area of the GTX. For the interfaces that involved GTXs preaged prior to the shear box experiments for up to 2 years at 85 °C, it was found that the 2400 g/m2 heat bonded two-layered GTX exhibited internal shear failure at low shear displacements. However, all the highly aged single layered GTXs showed an increase in the peak interface friction angles with the increase in their ageing. For these single layered GTX, the results suggest that assessing the interface friction angles using unaged GTXs for the stability analysis is conservative as long as the GTX remains intact in the field.

Fully resolved numerical simulations of a micron-sized spherical particle residing on a surface with large-scale roughness are performed by using the Lattice–Boltzmann method. The aim is to investigate the influence of surface roughness on the detachment of fine drug particles from larger carrier particles for transporting fine drug particles in a DPI (dry powder inhaler). Often the carrier surface is modified by mechanical treatments for modifying the surface roughness in order to reduce the adhesion force of drug particles. Therefore, drug particle removal from the carrier surface is equivalent to the detachment of a sphere from a rough plane surface. Here a sphere with a diameter of 5 μm at a particle Reynolds number of 1.0, 3.5 and 10 are considered. The surface roughness is described as regularly spaced semi-cylindrical asperities (with the axes oriented normal to the flow direction) on a smooth surface. The influence of asperity distance and size ratio (i.e. the radius of the semi-cylinder to the particle radius, Rc/Rd) on particle adhesion and detachment are studied. The asperity distance is varied in the range 1.2

Compared with a copper wire electrode, molybdenum wire with a poor conductor is usually used as the electrode in high speed wire-cut electrical discharge machining (HSWEDM), so the resistance of an ultra-fine wire cannot be ignored. To study the differences of discharge characteristics between the ultra-fine wire and the conventional diameter wire, the continuous discharge waveform of two kinds of wire electrodes was compared. It was found that there was a multi-channel discharge phenomenon in the discharge waveform cutting by ultra-fine wire. Through the establishment of a discharge equivalent circuit model and the simulation analysis of the electrostatic field, it was found that the reason why ultra-fine wire is easy to form multi-channel discharge phenomenon is that the potential difference between the wire and the workpiece increased linearly along the axis of the wire. Besides, etching products like metal particles will distort the electric field between the electrodes. Both of them make it easy to form a multi-channel discharge in machining. The results show that the distributions of the equivalent resistance and the peak current are affected by the multi-channel discharge position. Multi-channel discharge can disperse energy and increase effective discharge frequency. Compared with the 0 mm spacing, at a spacing of 100 mm, the machining efficiency increases by 8.7%, the surface roughness decreases by 37.7%, and the average recast layer thickness decreases by 46.6% under the condition of ultra-fine wire-EDM.

Ultrasonic vibration-assisted grinding (UVAG) is an effective and promising method for machining of hard-to-cut materials. This article proposed an ultrasonic vibration plate device enabling the longitudinal full-wave and transverse half-wave (L2T1) vibration mode for UVAG. The characteristics of two-dimensional coupled vibration in different directions were analyzed on the basis of apparent elastic method and finite element method. Furthermore, a correction factor was applied to correct the frequency error caused by the apparent elastic method. Finally, the comparative experiments between the conventional creep-feed grinding and UVAG of Inconel 718 nickel-based superalloy were carried out. The results indicate that the apparent elastic method with the correction factor is accurate for the design of plate device under the L2T1 vibration mode. Compared with the conventional creep-feed grinding, the UVAG causes the reduction of grinding force and the improvement of machined surface quality of Inconel 718 nickel-based superalloy. Furthermore, under the current experimental conditions, the optimal ultrasonic vibration amplitude is determined as 6 μm, with which the minimum surface roughness is achieved.

The influence of surface roughness on the interfacial dynamic recrystallization kinetics and mechanical properties of Ti-6Al-3Nb-2Zr-1Mo hot-compression bonding joints was systematically investigated. It is found that for the bonding interface of rough surfaces, elongated fine grains are formed at the bonding interface due to shear deformation of the interfacial area. As the surface roughness increases, the proportion of elongated grains drastically decreases as they further reorient to form equiaxed grains along the bonding interface of rougher surfaces resulting from severe incompatible deformation of the interface area. Meanwhile, high-density geometrically necessary dislocations accumulate around the interfacial recrystallization area to accommodate the incompatible strain and lattice rotation. A rotational dynamic recrystallization mechanism is thereby proposed to rationalize the formation of fine interfacial recrystallization grains during bonding of rough surfaces. In contrast to that of rough surfaces, bonding interface of polished surfaces exists in the form of straight interface grain boundaries without fine grains under the same deformation conditions. While with the increase of deformation strain, small grain nuclei form along the bonding interface, which is associated with discontinuous dynamic recrystallization assisted by strain-induced boundary migration of interface grain boundaries. Moreover, the bonding joints of rough surfaces show lower elongation compared with that of polished surfaces. This is because the formation of heterogeneous fine grains with low Schmid factor along the bonding interface of rough surfaces, leading to worse compatible deformation capability and thereby poor ductility of bonding joints.

Stainless steels have received wide attention as a substitute material for bipolar plates in high temperature proton exchange membrane fuel cell (HT-PEMFC). In the present work, the CrN, CrAlN and multilayer CrN/CrAlN coatings were deposited on 316L SS to increase the corrosion resistance and decrease the interfacial contact resistance. The deposited coatings exhibited face centered cubic phase structure and it was verified from the X-ray diffraction pattern. X-ray photo electron spectroscopy results showed the formation of both CrN and CrAlN layers on 316L SS. CrN/CrAlN coating is more helpful in water management due to low surface roughness and high contact angle in the HT-PEMFC environment. The corrosion resistance behavior of all the samples were studied in 85% H3PO4 solution at 140 °C purged with H2 (HT-PEMFC anode) and O2 (HT-PEMFC cathode) gases. The results showed that all the coatings considerably improved the performance of 316L SS and superior corrosion resistance was observed for CrN/CrAlN multilayer coating, whose protective efficiency was 98.12% and 96.14% in the two simulated HT-PEMFC environments. The results of electrochemical impedance spectroscopic studies demonstrated higher impedance for CrN/CrAlN coating. Surface morphological studies performed after corrosion studies revealed that protection ability of CrN/CrAlN coating still remained acceptable. A very low interfacial contact resistance value of 6 mΩ cm2 at 140 N/cm2 was observed for CrN/CrAlN coating. Moreover, after corrosion studies, the interfacial contact resistance value of CrN/CrAlN coated 316L was much lower than that of CrN and CrAlN coatings due to the increased oxidation resistance. The maximum power density of about 0.93 W/cm2 at 2 A/cm2 and output voltage of 0.96 V was observed for CrN/CrAlN coating.

The effect of numerous process variables has been explored for surface roughness and material removal rate during the magnetic abrasive finishing process. A hybrid approach was used in which the Taguchi technique is used in conjunction with grey relational analysis to reach the optimum combination of input variables. The L16 orthogonal array design was used to get a different combination of parameters. It was found that spindle speed of 200 rpm, the quantity of magnetic abrasives of 5 mg, mesh number of 270, and machining time 60 min caused minimum surface roughness of 0.066 µm during magnetic abrasive finishing of the brass plate. The percentage contribution of input parameters has been reported. Subsequently, the optimum results were obtained using multi-objective optimization techniques of grey relational analysis, and results were also validated using experimentation.

Using six distinct nature-inspired optimization strategies, the cutting constraints of plasma arc cutting (PAC) procedures for cutting stainless steel (AISI 304) were optimized in this work. Using plasma arc machining settings, response surface approach was utilized to examine the influence of cut quality. The material removal rate, chamfer, heat-affected zone, surface roughness, kerf width, and dross are the most significant output responses chosen for this investigation. The corresponding machining parameters examined in this analysis were the stand-off gap, gas pressure, cutting speed, and cutting current. Here, the evaluation based on the distance from the average solution (EDAS) approach is employed through the calculation of weights between criteria by pairwise comparison. Twenty-seven experiments were performed on AISI 304 stainless steel by RSM based Box-Behnken Design (BBD) in the design of the experiment. Here, the Genetic algorithm, Grey wolf optimization, Jaya optimization, Whale optimization, Particle Swarm optimization, and simulated annealing algorithm approaches as six different optimizations have been utilized to predict the optimal setting of the experiment. A comparative inspection of these nature-inspired algorithms in plasma cutting operations was performed in this study. Finally, the results were validated with a confirmation test.

Data from the Cyclone Global Navigation Satellite System (CYGNSS) mission augmented with a physical surface scattering model were analyzed to develop a semiempirical model, which consists of three main modeling components for soil moisture, vegetation, and surface roughness. CYGNSS data collected from March 2017 to March 2020 were collocated with the soil moisture data from the Soil Moisture Active Passive (SMAP) mission and climatology vegetation water content (VWC) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) data. The matchup data were binned as a function of soil moisture, VWC, and incidence angle. The CYGNSS data were calibrated using a coherent reflection equation to obtain an effective reflectivity. The response of CYGNSS effective reflectivity to soil moisture changes is consistent with the change of the Fresnel reflectivity based on Mironov's soil dielectric constant model used by the SMAP and Soil Moisture Ocean Salinity (SMOS) missions for soil moisture retrieval. The CYGNSS effective reflectivity decreases approximately linearly (in dB) with respect to the NDVI-VWC. The estimated values of vegetation attenuation parameter (b) agree with values published in the literature and are corroborated with the estimated values of b using the SMAP dual-polarized channel algorithm based on land cover types. A CYGNSS surface scattering map has been derived and reveals a mixed contribution of coherent and incoherent scattering effects and the effects of topography. The semiempirical model, leveraging two of the key modeling functions used by microwave radiometry, will pave the way for a synergistic use of reflectometry and radiometry data for multiparameter retrieval and development of consistent soil moisture products.

In past two decades electro chemical machining (ECM) and electric discharge machining (EDM) processes have been widely explored for machining of different grades of steel (including AISI 304). Although there is difference in material removal mechanism of EDM (localized heating and vaporization being thermal process) and ECM (ionic dissolution being electrochemical energy based process), yet the user needs broad data base for comparison and selection of particular process. But hitherto little has been reported on relative comparison of EDM and ECM processed AISI steel surface from surface roughness (Ra), surface hardness (HV) and morphological characteristics view point. This paper reports the comparison of AISI 304 steel machined surface by EDM and ECM. The comparison has been made after process optimization of EDM and ECM separately (using Taguchi approach). The results of study suggest that ECM is better process than EDM from Ra view point (3.10 µm for ECM and 6.41 µm for EDM) and porosity% view point, whereas from HV viewpoint no significant difference was observed.

In the present research work, experimental and finite elemental analysis of powder mixed electric discharge machining of Ti-Nb-Ta-Zr alloy has been presented. The mechanism for the materials removal has been numerically simulated. A mathematical model for the surface roughness has been presented. The effect of process parameters such as peak current, pulse-on, pulse interval, and voltage on the temperature distribution in surface has been investigated. The crater geometry of PM-EDM and EDM formation has been compared. The results showed that PM-EDM produced small micro-size craters as compared with EDM. The PM-EDM produced better surface roughness. The predicted surface roughness for the 0.78 μm in the case of PM-EDM.

This paper presents a nanoscale-inspired continuum model to capture the coupling of adhesion and friction in contact-mechanics problems. The method relies on Green's function molecular dynamics to calculate the elastic body fields and on a phenomenological mixed-mode coupled cohesive-zone model to describe the interplay between normal and tangential tractions, i.e. adhesion and friction. While the presented formulation is applicable to linearly elastic solids with generic surface roughness, the focus of our analysis is on the indentation of an array of circular rigid punches into a flat, deformable solid. Our results show that the coupling between adhesion and friction leads to an increase in the contact size and a decrease in the pull-off load.

Purpose The purpose of this study is to investigate the microstructural evolution of high-strength 2024 Al alloy prepared by the laser powder bed fusion (L-PBF) additive manufacturing (AM) route. The high-strength wrought Al alloy has typically been unsuitable for AM due to its particular solidification characteristics such as hot cracking, porosity and columnar grain growth. Design/methodology/approach In this research work, samples were fabricated using L-PBF under various laser energy densities by varying laser power and scan speed. The microstructural features that developed during the solidification are correlated with operating laser parameters. In addition, finite element modelling (FEM) was performed to understand the experimentally observed results. Findings Microstructure evolution and defect formation have been assessed, quantified and correlated with operating laser parameters. Thermal behaviour of samples was predicted using FEM to support experimental observations. An optimised combination of intermediate laser power and scan speed produced the least defects. Higher energy density increased hot tearing along the columnar grain boundaries, while lower energy density promoted void formation. From the quantitative results, it is evident that with increasing energy density, both the top surface and side wall roughness initially reduced till a minimum and then increased. Hardness and compressive strength were found to decrease with increasing power density due to stress relaxation from hot tearing. Originality/value This research work examined how L-PBF processing conditions influence the microstructure, defects, surface roughness and mechanical properties. The results indicates that complete elimination of solidification cracks can be only achieved by combining process optimisation and possible grain refining strategies.

Electron beam melting (EBM), as an excellent Additive Manufacturing (AM) technology, enables the printing of Ti-6Al-4 V alloy for a wide range of applications such as aerospace and biomechanical industries. It improves functionality and integrity of components and negates complexities in assembly processes. However, due to the poor surface and sub-surface integrity represented by the rough surface finish and low dimensional accuracy, achieving a favorable surface condition is quite challenging. Therefore, post processing becomes essential for these electron beam melted (EBM-ed) Ti-6Al-4 V alloys. Being the most common technique to improve such parts, milling of Ti-6Al-4 V alloy is very challenging and resulting tool wear issues, due to its unique material properties. Thus, this paper presents a comprehensive study on the surface integrity of EBM-ed Ti-6Al-4 V parts processed by precision grinding and electropolishing, aiming to qualitatively and quantitatively clarify the interrelation between process parameters and processed surface quality. The surface and subsurface characteristics such as profile accuracy, surface roughness, microstructure, defective layer and residual stress before and after post processing were compared and evaluated. The results show that by precision grinding, the profile accuracy was improved from over 300 µm PV to 7 µm PV, while surface roughness (Ra) was reduced from 30 µm to about 2 µm. The layer with partially melt particles was removed, but introduced a deformed subsurface layer with more residual stress. Then by applying electropolishing, the residual stress was released and the deformed layer was removed. In addition, Ra was further reduced to 0.65 µm. The research can serve as a reference for the integration of post machining processes with AM.

Hypothesis: It has been verified that a surface of single micro-scale structures with certain roughness could exhibit petal effect. That is, water drops with a contact angle larger than 150° would pin on the petal effect surface. It is conjectured that the water drop could pin on the single micro-scale roughness petal effect surface by totally infiltrating into spaces (or grooves) between micro-pillars. Experiments: An inverted optical microscopy system is synchronically applied in the process of advancing/receding contact angle (ACA/RCA) measurements to directly observe the wetting behavior of water droplets on hydrophobic patterned surfaces with regular arrays of square micro-pillars. Findings: A sequence of wetting behavior evolution, Wenzel → petal → pseudo-lotus → lotus, is observed on the hydrophobic patterned surfaces along with increasing surface roughness. It is interesting to observe a Cassie-Wenzel transition for water drops on a petal substrate during the ACA measurement (embedded needle method), leading to two ACAs, one before (in Cassie state) and one after the transition (in Wenzel state). Thus, the petal substrates have large contact angle hysteresis (CAH) (with both ACA and RCA in Wenzel state) to pin the water drop in Wenzel state. A Cassie-Wenzel transition is consistently observed during the evaporation process of water drops on pseudo-lotus substrates, leading to two RCAs: one in Cassie state and one in Wenzel state. The pseudo-lotus substrates have CAH (with both ACA and RCA in Cassie state) small enough to make water drops easily slide off.

Commercial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) were used to prepare microbeads, with diameter ranging from 50 to 100 µm, by an emulsion-evaporation process. The properties of the beads reveal that the elaboration process enables the formation of spherical particles, that the crystallinity of the former polymer is not altered during the process and that the surface roughness of the particles can be tuned by changing the nature of the lateral chain in the PHA structure, in good correlation with its crystalline behavior. The mechanical properties of the different PHA beads are also found to be intimely linked with the crystalline content of the beads, with modulus varying between 1 to 7 GPa. All these properties are also governing the degradation behavior of these materials, as tested under marine environment. With a rapid degradation, similar to cellulose, and a degradation rate correlated with the crystalline content, these results emphasize the interest in developing PHA materials with tunable functions and degradation properties.

Bamboo (Arundinaria clarkei) short fibers were treated with 6% conc. NaoH solution for five different durations viz. 3 h, 6 h, 9 h, 12 h and 24 h. Effect on physical properties like diameter and density were studied. Fibers were examined using Scanning Electron Microscope (SEM) to study the effect of alkali treatment on its surface characteristics. Single fiber tensile tests were conducted to assess the tensile strength of the fibers. Comparative study of the SEM micrographs indicated removal of outer layer with the surface irregularities becoming more prominent with increasing duration. The fiber surface was scanned using an Atomic Force Microscope (AFM) to quantify the increase in surface roughness with alkali treatment. Tests results showed positive effect on the strength till 6 h beyond which the tensile strength was observed to reduce. Fourier Transform Infrared (FTIR) spectroscopy results indicated reduction in content of holocellulose along with hemicellulose, lignin and cellulose which explains the variation in tensile strength with increasing duration of treatment.

In view of the serious problem of milling heat in milling nickel-based superalloys Inconel 718, this paper investigates the heat transfer performance of internal cooling in end milling Inconel 718, and the superiority of internal cooling milling cutter's heat exchange ability during processing is explored. The flow field characteristics of cutting fluid and milling temperature are studied by Computational Fluid Dynamics (CFD) and Finite Element Method (FEM). Compared with external flood cooling, the principle of internal cooling with excellent heat transfer performance is explained and the influence of coolant pressure on lubrication performance is analyzed. Experiments for end milling of Inconel 718 under different cutting speeds and cooling conditions have been carried out. The results indicate that the simulated and measured temperatures showed an acceptable agreement. The internal cooling has better heat transfer performance compared with flood cooling. With the increase of coolant pressure, the heat exchange efficiency is gradually enhanced. When the coolant pressure rises from 2 bar to 10 bar, the milling temperature at the measured point inside the workpiece reduces by 27.55 °C, the surface roughness reduces by 12.0%, the surface residual compressive stress increases by 68.37 MPa and better surface morphology is obtained. Besides, in the experimental range, with the increase of cutting speed, milling temperature increased, the pile-up effect on the sides of scratching was weakened and better machined surface integrity was found.

To expand the measurement target from that containing simple cylindrical-shaped components to complex-shaped components that have several directional tilted surfaces, we determined an issue in measuring the rough surfaces with laser distance measurement. The issue is that laser speckle causes measurement error, which amount, we found, can be determined by the diameter and irradiation angle of the measurement laser beam. We then developed two error-reduction techniques that are based on the optical properties of a detected waveform and power. We conducted a basic experiment and a feasibility study with actual samples, to evaluate the distance measurement performance of targets with various surface roughness and irradiation angles. The roughness and angle range of the evaluation was determined considering actual measurement needs in parts manufacturing. We confirmed that the measurement error, whose maximum value was nearly 80 μm, decreased to less than 20 μm using our proposed local-maximum-power-based technique.

Monocrystalline diamond possesses covalent bonding making diamond extremely hard and difficult to machine. In this study, a microdiamond stylus typically used in measuring surface roughness is machined to exemplify the proposed ‘microspark erosion-assisted machining with heat-avoidance path’ technique. Based on the high thermal conductivity and weak electrical conductivity of boron-doped monocrystalline diamond, high-frequency pulsed discharge plasma is employed to efficiently perform microspark erosion machining on an extremely hard monocrystalline diamond blank. It was found that the pulse-on time and servo voltage respectively affect erosion plasma length and the erosion gap during diamond machining. Also, the safety distance and safety height of the erosion path dominate heat transfer to filler metal. These factors all affect the firmness of the brazed diamond blank on the substrate. Three mechanisms for removing carbon atoms from the diamond blank surface were observed. They are vaporization, melting, and graphitization of carbon atoms. This graphitized carbon atoms have weak electrical conductivity, which is conducive to inducing the wire-electrode to generate a greater electric field and secondary discharging, facilitating removal of additional carbon atoms. Experimental results indicate that a microdiamond stylus prototype with a tip of 10 μm can be safely formed using a ‘microspark erosion-assisted machining with heat-avoidance path’ technique, creating 93.7% repeatability of the minimum residual stylus diameter. The tangential micro-grinding facilitates the stylus tip to receive grinding from the grinding wheel's maximum tangential speed and create the precision microdiamond stylus with 1 μm in tip-radius. The applied microspark erosion-assisted machining had a diamond material removal rate that was 54% more efficient than conventional grinding of a commercial microdiamond stylus. The formed microdiamond stylus was inspected by Raman spectroscopy and verified by the surface roughness standard gauge to be up to industry standards.

To obtain the great surface quality of Ti–6Al–4V and achieve high efficiency in the polishing process, the chemistry enhanced shear thickening polishing (C-STP) was proposed, and the polishing performance of different pH slurry was studied. The results show that the material removal rate gradually increases as the pH value decreases from 10 to 1, and the best surface quality is obtained at pH 2. The corrosion current density and potential were measured by potentiodynamic polarization under three typical pH values. It is confirmed that the most massive corrosion rate presents at pH 2, and the passive film is most susceptible to be produced at pH 10. The reaction resistance was measured by electrochemical impedance spectroscopy to clarify the polishing mechanism. Under acidic conditions, the chemical reaction product on the surface can be quickly removed by mechanical action of the abrasive. On the contrary, the passive film formed on the surface under the alkaline condition is difficult to be removed. The corrosion reaction products were determined by X-ray photoelectron, and the chemical reaction under acid-base environment was derived. MRR reached 107.3 nm/min under the selected process parameters, and the surface roughness (Sa) is reduced from 124 nm to 8.6 nm within 15 min.

There are few studies on predicting fully bistatic scattering from the rough surface of Mars, though some bistatic radar observations have been made, such as in the MARS EXPRESS mission. To better understand the interaction of radar signals with a planetary surface in bistatic radar observations, the topographic-scale roughness of Mars, characterized by a two-dimensional power spectrum density (2D-PSD), is examined in view of its global roughness variations and scale dependence on geological units. The analysis shows that the Martian 2D-PSD is strongly dependent on the geological units and that it lies between Gaussian and exponential functions, with a power index equal to 1.9. The bistatic scattering coefficients are calculated by an advanced integral equation model (AIEM) with the 2D-PSD as the input. It shows that the specific surface roughness spectrum and the dielectric inhomogeneity should be taken into account in interpreting the bistatic radar scattering response.

text, 学術雑誌論文 / Journal Article, In order to improve the finishing efficiency of the Magnetic Abrasive Finishing process, we proposed a new MAF process with renewable abrasive particles using compound magnetic finishing fluid circulatory system in this paper. This new finishing process has a circulating system that uses a conveyor belt to renew the mixed abrasive particles. This not only maintains the stability of the finishing but also ensures that the processing does not need to be interrupted. In this study, we investigated the magnetic field distribution, finishing force, and finishing behavior of the processing area. Furthermore, we designed experimental device to finish the sus304 stainless steel plate, to verify the feasibility of this process and understand its characteristics through processing experiments. Moreover, the influence of important process parameters, including magnetic particles, abrasive particles, conveyor belt line speed and working gap, on the surface quality of the workpiece is studied through the experiment. The experimental results indicate that the present process can achieve stable processing of the material surface without interruption, and the surface roughness of the sus304 stainless steel plate has been improved from 273 nm to 23 nm through this process.

Ultrasonic elliptical vibration cutting is a very promising technique for the machining of brittle materials. However, its machining performance is currently limited by the ductile machining model and the machining strategy with a constant feed rate, leading to low machining efficiency. To overcome this defect, this paper presents a novel self-tuned ultrasonic elliptical vibration cutting (SUEVC) technique to achieve high-efficient ductile-regime machining of the micro-optics array on brittle materials. The proposed SUEVC includes a ductile-regime machining model and a tool path generation method. In SUEVC, the feed rate adaptively changes with respect to the local shape variation of the desired surface along the feeding direction to ensure both crack-free surface and high machining efficiency. Finally, two 1 × 3 spherical micro-optics arrays were successfully fabricated on single-crystal MgF2 by SUEVC and the traditional machining strategy respectively. Results demonstrated that the SUEVC could enhance the machining efficiency by 30% relative to the traditional machining strategy, while maintaining similar surface roughness and a crack-free surface.

Particle-wall collisions appear in many different processes of particle technology. During a collision, different micro processes, such as friction, plastic deformation and adhesion can take place in the contact and lead to an energy dissipation. The surrounding fluid between particle and wall can also decrease the impact velocity due to viscous forces. This study focuses on the influence of the surface roughness on particle-wall collisions in ambient air and water. The single particle impact tests were performed with spherical zirconium oxide particles on a polished and an untreated titanium surfaces to investigate the energy dissipation during collision in a wide range of Stokes numbers (20–8900) depending on the surface roughness. A 3D high-speed camera system was used to obtain the particle impact and rebound behavior. The particle and wall roughness were measured with confocal microscopy and scanning probe microscopy, from which an equivalent roughness parameter was derived. The experiments showed that with an increase of the roughness, the coefficient of restitution decreases in air, while increasing during collisions in water. An elastohydrodynamic model of particle collision on the wall covered by a liquid layer was used to predict the coefficient of restitution for the contact in ambient fluids while considering measured roughness parameters.

Here, we report the structural and electronic modification induced in chemical vapor deposited graphene by using swift heavy ions (70 MeV Ni6+).Raman spectroscopy was used to quantify the irradiation-induced modification in vibrational properties. The increase in defect density with fluence causes an increase in the intensity ratio of its characteristic Raman D and G band. The increase in defect density also results in a decrease in crystallite size. The changes in the crystal structure are observed from X-rays diffraction measurement. Swift heavy ion irradiation induced defect, modified the surface roughness and surface potential of graphene thin film as measured from atomic force microscopy and scanning Kelvin probe microscopy respectively. The increase in the work function, surface roughness as well as defect concentration with fluence, indicate the possibility of linear correlation between them. Presence of defects in graphene sheets strongly affects surface electronic and optical properties of the material that can be used to tailor the optoelectronics device performance.

The precision fabrication of ceramic moulds for the mass-production of micro/meso-structural arrays places a tremendous challenge to the manufacturing industry. This work aims to reveal the physics behind the processes so as to address this technological challenge. A new method for texturing the diamond grinding wheel surface with a micro-abrasive waterjet is proposed for highly efficient form-grinding of ceramic moulds into the required micro/meso-structural surfaces. It shows that this technology provides some unique advantages in improving the sharpness and geometrical accuracy of the grinding wheels. The mechanisms about material removal and texture formation in grinding wheel truing are investigated to enable the precise control of micro/meso-structure generation on the grinding wheel. A theoretical model is established to study the effect of grinding wheel surface micro/meso-textures and grain trajectory on the quality of the ground mould surface and reveal the reflection mechanism of the ground marks on the mould surface. Furthermore, an integrated rough-fine grinding strategy is proposed which is shown to significantly increase the grinding efficiency by 15–24 times. It is found that ductile domain grinding of ceramic moulds to achieve the required contour profile of 6.7 μm PV accuracy and a surface roughness Ra of less than 40 nm can be achieved.

In this study, GdBa2Cu3O7−ẟ (GdBCO) sol with ultraviolet (UV) sensitivity was prepared using Gd(OAC)3, Ba(OAC)2, and Cu(OAC)2 as the starting materials, methanol as the solvent, and 2,2′-bipyridine as the chemical modifier. Furthermore, chelation mechanism of the chemical modifier and metal ions in the sol was analyzed by infrared and UV absorption spectroscopy. Cu2+ in the sol was found to chelate with the chemical modifier to form a photosensitive chelate, rendering UV sensitivity to the sol. Next, the photosensitive chelate was decomposed by exposing it to UV light, and the decomposition product was barely soluble in organic solvents. By exploiting the self-sensitivity of GdBCO, fine patterns of its films were obtained (without photoresist throughout) with micron scale resolution. XRD and superconductivity performance tests revealed that compared to the GdBCO film without fine patterns, fine-patterned GdBCO fabricated herein does not exhibit significant degradation in terms of its crystal structure and superconductivity. This result indicates that fine-pattern technology developed for chemical film formation is simple in terms of process and equipment, and it does not affect the performance of the GdBCO film. Therefore, “chemically modified self-photosensitive” photolithography can be applied for the preparation of the GdBCO-based inorganic microstructure, which exhibits specific significance for the research and application of high-temperature superconductor electronic devices. In addition, during heat treatment, the technology of first introducing carbon dioxide and then water vapor also was adopted in this paper, which reduced the surface roughness of the GdBCO film.

Diamond wire saw cutting technology has been widely used in the slicing of sapphire crystal. The ultra-high hardness of sapphire makes the sawing characteristics of diamond saw wire constantly change. At present, there is a lack of in-depth understanding about the influence of sawing characteristics on the quality of sapphire as-sawn wafer, which leads to the unreasonable matching between the process parameters and the sawing characteristics of the saw wire, and reduces the as-sawn wafer quality and the saw wire life. In this paper, the slicing sapphire crystal experiment was carried out with constant process parameters and the variation of saw wire bow angle, nominal diameter and saw kerf loss, surface morphology and surface roughness of the as-sawn wafer during the whole life cycle of the saw wire from initial cutting to breakage was studied. The evolution mechanism of wear and sawing characteristics in the whole life cycle of saw wire was explored, and a reasonable processing scheme which can match the sawing characteristics was put forward. The research results show that in the whole life cycle of the saw wire, the abrasives emerge from the plating layer in turn, then the cutting edge are blunted, and finally the abrasives are greatly flattened and a small amount of falling off. Saw wire has experienced initial wear, stable wear and sever wear, and the proportion of three stages in the whole life cycle is about 0.3: 0.6: 0.1. Compared with the initial stage of wear and the late stage of rapid wear, the saw wire has higher sawing characteristics and better as-sawn wafer quality in the middle stable wear period. The sawing characteristics of new saw wire is relatively weak at the beginning of cutting, so the feed speed of workpiece should be increased gradually from low to high; When most of the abrasives finish sharpening edge, a relatively stable and high feed speed can be adopted; When the abrasives are obviously flattened or fall off, the feed speed should be decreased to accommodate the significantly reduced. cutting performance of diamond saw wire.

In this research, a one-way abrasive flow machining (AFM) was sketched and built, and the impact of temperature on surface roughness ( R a ) values and material removal rate ( M R R ) before and after each test have been investigated considering the SiC. Al2O3, and B2O3 particles as abrasive particles. The abrasive particles were dispersed at 35 wt.% in the prepared media. The findings revealed that the media containing Al2O3 abrasive particles had higher surface roughness compared to the SiC and B2O3 particles. The maximum variation of surface roughness for SiC, Al2O3, and B2O3 particles was observed at − 196 °C, which was 2.991, 2.588, and 1.684, respectively. In addition, the material removal rate values decreased for all the prepared samples as the temperature was reduced. At lower temperatures, lower material removal rate values were recorded since the viscosity of the abrasive paste increased.

The influence of different precipitate-dislocation interactions, namely dislocation shearing and bypassing mechanisms, on PLC bands and the resultant surface roughness in AlMgScZr alloy was investigated. Three-dimensional surface roughness was quantitatively measured by confocal microscopy. We find that the introduction of shearable precipitates increases the stress amplitude, decreases the PLC bands number and surface roughness. However, the stress amplitude decreases, the PLC bands number and surface roughness increase with shearable precipitates turning to nonshearable precipitates. By analyzing the precipitation strengthening mechanisms quantitatively, the influence of precipitates on PLC bands and the resultant surface roughness was explored. Furthermore, our study demonstrates that the shearable precipitates can decrease the surface roughness by decreasing the number of PLC bands, which is instructive for designing structural materials with desirable mechanical property and surface quality.

Aluminium nitride high-temperature co-fired ceramic (AlN HTCC) substrate is a preferred electronic packaging material. It displays a low thermal expansion coefficient, low dielectric constant, low dielectric loss, and high thermal conductivity at a high frequency. It can also prefabricate the circuit inside. Considering the need to increase the specific surface area of AlN HTCC substrates and thereby enhance the heat dissipation performance, a rapid fabrication method involving chemically assisted laser ablation is proposed to machine microstructures on AlN HTCC substrates. The influence of power, atmosphere, and other factors on the ablation quality of AlN HTCC substrates was explored on this basis. The main component of the ablation products was Al in an Ar atmosphere. However, the modification layers in N2 and O2 atmospheres were composed of multiple components including Al, AlN, and Al2O3. The accuracy of the top and bottom widths of the microgrooves in the Ar atmosphere was higher than those for the N2 and O2 atmospheres. However, the variation of atmosphere had a negligible effect on the ablation depth. When the laser-energy density was 100 J/mm2 and the scanning distance was 10 μm, the ablation depth increased linearly from 150 μm to 350 μm as the laser power increased from 8 W to 20 W. The deviation in laser-energy density was established to predict the surface roughness and optimise the laser parameters. It was observed that the surface roughness increased with an increase in the deviation in laser-energy density. The surface roughness could be reduced by two–three times from that obtained by laser ablation with optimisation.

In this paper, a novel approach was proposed to achieve the joining of AlN and Cu by nanosecond laser pre-irradiation of AlN. The effects of the speed of laser scanning on the morphology, chemical compositions, and properties of the surface of AlN ceramic and the mechanism of laser-assisted joining of AlN and Cu were investigated. With the increase of the speed of laser scanning, the surface roughness of AlN decreased. After nanosecond laser irradiation, element Al was detected on the surface of AlN. When nanosecond laser irradiation was applied, the hydrophilicity and the surface energy of the ceramic surface were improved. The modified AlN was successfully joined to Cu at the temperature of 620 °C with a speed of laser scanning of 500 or 1000 mm/s. The results of TEM confirmed the presence of Al4Cu9, indicating the metallurgical combination of Cu and AlN. Also, the method presented in this paper was supposed to be of great reference significance for the joining of ceramics and metals.

We present a novel meso-scale model for computing anisotropic and asymmetric friction for contacts in rigid body simulations that is based on surface facet orientations. The main idea behind our approach is to compute a direction dependent friction coefficient that is determined by an object's roughness. Specifically, where the friction is dependent on asperity interlocking, but at a scale where surface roughness is also a visual characteristic of the surface. A GPU rendering pipeline is employed to rasterize surfaces using a shallow depth orthographic projection at each contact point in order to sample facet normal information from both surfaces, which we then combine to produce direction dependent friction coefficients that can be directly used in typical LCP contact solvers, such as the projected Gauss-Seidel method. We demonstrate our approach with a variety of rough textures, where the roughness is both visible in the rendering and in the motion produced by the physical simulation.

This work, examines the Surface Roughness (SR) of composite consisting Aluminium alloy (AA6061), Magnesium and Rock dust during turning process. To study the performance, three different test specimens with different constituents of Al 6061-T6, AZ31 and Rock dust were prepared by stir casting method. Turning experiments were carried out using MTAB Siemens – CNC lathe. The input parameters for machining are speed, depth of cut & feed and output response is surface roughness For each test specimen, there are 15 turning operations were performed using Box-Ben hen Design approach. To analyze the process parameters for SR, the models of ANOVA and Decision Tree (DT) algorithms were performed. Both algorithms are confirmed that, speed is the most significant factor for SR. The addition of AZ 31 with 1% and rock dust of 2% in AA6061 produced better surface finish. Regression models of linear regression, multilayer perception and support vector regression from data science were formulated to find the relationship between variables. Among these models multi layer perception produced minimum root mean square error.

In this study, the effect of roughness of cyclone wall on the rate of erosion and cyclone performance was studied using the CFD technique with the aid of the Ansys-Fluent 19.2 software. The Reynolds stress transport model was used to simulate the airflow turbulence in the rotating flows in the cyclone. The validated computational model was used, and the variations of axial velocity, tangential velocity, collection efficiency, cyclone pressure drop, and rate of erosion for different wall roughness were evaluated. For simulating surface erosion, the Oka model was used. The result of this study revealed that the wall roughness significantly affected airflow behavior in the cyclone and the resulting cyclone performance. In addition, when the wall roughness increased, the wear rate decreased. It was also found that the solid loading and inlet gas velocity significantly affect the erosion rate and even more than that of particle size.

Direct-ink-writing type additive manufacturing with water-based inks such as hydrogels or polymer solutions is broadly utilized for bioprinting applications. However, the resolution of this implementation is limited due to the rapid ink drying experienced at small size scales leading to nozzle clogging and low fidelity prints. To address this issue, a humidity-controlled direct-ink-writing (HCDIW) approach is presented, where the microenvironment around the printing nozzle is controlled through introduction of aerosolized water. Using this approach, the nozzle microenvironment can be varied between undersaturated yet high relative humidity (ambient to 100% RH) to oversaturated conditions where condensing droplets are deposited on the already printed ink filaments. The influence of the aerosolized water and the resultant micro-environment on the printing process was studied using water dissolved sodium carboxymethyl cellulose (NaCMC) ink, specifically focusing on nozzle clogging, printed filament geometry, surface quality and layer by layer stacking. These studies showed that the ink drying induced nozzle clogging issues can be mitigated through increased relative humidity at the nozzle exit and is virtually eliminated for ~100 μm nozzles in oversaturated conditions. The decelerated ink drying under the effect of aerosolized water leads to reduced solute advection and skin formation. This in turn improves surface roughness while reducing adverse effects such as coffee-ring and void formation during additive manufacturing of micro-scale structures. Furthermore, layer-to-layer fusion and associated side-surface quality were improved specifically in undersaturated conditions. Reduction of deposited ink filament concentration in oversaturated conditions leads to excessive spreading of the deposited inks leading to geometric distortions. These results indicate that the humidity control approach can significantly improve the resolution of the direct-ink-writing approaches, enabling processing of water-based inks at micro-scales.

This work is devoted to investigate the structural and electrical properties of the Ce, Gd-doped YBCO superconductors bulk ceramics. YBa2-xRExCu3O7−δ (x = 0, 0.01, 0.05, 0.1) (RE = Gd, Ce) samples were prepared by means of conventional solid-state reaction. X-ray diffraction analysis was carried out to identify the present phases in the as-prepared samples followed by the determination of their lattice parameters. Fourier Transform Infrared Spectroscopy (FTIR) was used to identify the functional groups. Furthermore, the morphology and the surface roughness of the studied samples were characterized using Scanning Electronic Microscopy (SEM) and Atomic Force Microscopy (AFM). Vickers Micro-hardness of the as-prepared samples was examined. Besides, the electrical resistivity measurements were achieved to determine the critical transition temperature TC and the critical current density JC. The effect of Ce and Gd additions is clearly noticed in the obtained results, where all the prepared samples are superconductors with the presence of Y123 as a major polycrystalline phase. From the XRD patterns, the intensities of the Y123 corresponding peaks decrease with further increasing the Ce and Gd contents. In addition, the variation of the cell parameters was significant after additions of both Ce and Gd, which affect the grain size and the oxygen content of the YBa2-xRExCu3O7−δ system. An improvement of the structure and surface roughness is observed on SEM and AFM images. Likewise, Vickers micro-hardness has increased after the Ce and Gd additions. Although, the critical transition temperature TC was not further increased upon Ce or Gd additions compared to the undoped YBCO samples. Nevertheless, an exception has been recorded with an increase of TC for YBa2-xRExCu3O7−δ with (RE = Gd, x=0.01) to reach 88 K. In contrary, an improvement of the deduced critical current density JC was achieved for all Ce-doped YBCO samples unlike those of Gd-doped samples.

Capillary tube models frequently rely on friction factor correlations, which are functions of the Reynolds number, and the tube's relative surface roughness. However, this study shows that explicitly correlating the friction factor with the relative surface roughness is unnecessary, at least when the latter is lower than 0.0025. To test this a correlation was fitted directly onto friction factor measurements obtained in an adiabatic flow of R600a, through nine capillary tubes from three manufacturers. The friction factor was correlated exclusively as a function of the Reynolds number, meaning that the impacts of the relative surface roughnesses on the friction factor were averaged, and included only implicitly. This correlation, and an existing correlation, which allows the specification of the relative surface roughness, were then implemented in a capillary tube model. The accuracy of the capillary tube model, using either the developed or existing correlation was then evaluated by comparing the results to experimental data. No significant decrease in the accuracy of the model was observed when the relative surface roughnesses, ranging from 0.0012 to 0.0025, were not individually specified for each capillary tube. To further verify this, the procedure was repeated on a larger database of friction factor and mass flow rate measurements, which also consisted of data from independent studies. Similar conclusions were drawn, as the average accuracy of the model differed only by 1 to 3% among different studies, and not always in favor of the correlation where the relative surface roughnesses could be specified.