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An embedded load cell sensor is proposed for the tool life prognosis and thrust force control of a band saw machine. The sensor enables the tool life and surface quality of the machined workpiece to be effectively improved through the use of a single sensing device strategically located in the cutting machine. The feasibility of the proposed sensor is demonstrated experimentally using a double-column horizontal sawing machine with medium carbon steel bars as the workpiece material. An investigation is performed into the effects of the cutting force, feed rate, and machining time on the tool wear and surface roughness of the machined workpiece. It is shown that the thrust force, tool wear and surface roughness of the machined workpiece are strongly correlated and increase over time. Based on the experimental results, a feedback control system is proposed for maintaining a constant thrust force on the band saw during cutting under even the most challenging conditions. Overall, the results confirm that the embedded load cell sensor and force monitoring and control methodology proposed in the present study provide an effective approach for maintaining the optimal cutting conditions in the sawing of medium carbon steel and improving the tool life and machined part quality.

A molecular dynamic (MD) simulation, which is used for estimating mechanical properties of both microscopic and mesoscopic materials during loading/unloading processes. Understanding the deformation mechanisms of material's internal structure, shape and volume is a key step to enhance its strength and rigidity. Novel nanostructures, nanoparticles and nanocomposites, more efficient, selective, and environmental friendly can be developed and suggested. At the moment, few experimental methods can characterize molecular mechanisms due to their time-consuming and cost-intensive. Therefore, MD simulation allows to gain understanding in structure-to-function relationships involved in the low-dimensional materials. Specifically, MD simulation can be performed on the time scale of nanoseconds, and in three dimensions, it is thus sufficient for the study of the mechanical behaviors and deformation mechanisms at a molecular level. This work reviews the progress in MD simulation of the mechanical properties and structure deformations for various tubular nanomaterials including silicon, carbon and III-V compound nanotubes (NTs), respectively. In particular, we have a detailed description and analysis of the impacts of environmental and structural factors on material strength for the present nanostructures. It is hopeful that this review can provide certain reference for the follow-up research.

A detailed understanding of surface decoration and interconnecting technologies is essential in realizing high-performance functional devices incorporating metal nanoparticle/graphene nanohybrids. This study employs classical molecular dynamics (MD) simulations to investigate the formation of amorphous copper (Cu) layers on a graphene surface via the collision, coalescence and nucleation of individual Cu nanoparticles (NPs) at temperatures in the range of 300–1300 K. The results indicate that the coalescence and melting temperatures are both sensitive to the particle size and the presence of the substrate. Moreover, an epitaxial interaction is found between the Cu NPs and the graphene substrate, in which mobile Cu atoms are captured and dragged to the graphene surface to produce self-assembled NP layers via a nucleation process. A series of structural evolutions and phase transitions are revealed during the thermalization process of the NPs. Finally, the results show that the presence of the substrate and associated contact epitaxy phenomenon play a key role in governing the structural morphology and thermal behavior of the Cu NP-based thin film.

Herein, we aim to develop a facile method for the fabrication of mechanical metamaterials from templated polymerization of thermosets including phenolic and epoxy resins using self-assembled block copolymer, polystyrene-polydimethylsiloxane with tripod network (gyroid), and tetrapod network (diamond) structures, as templates. Nanoindentation studies on the nanonetwork thermosets fabricated reveal enhanced energy dissipation from intrinsic brittle thermosets due to the deliberate structuring; the calculated energy dissipation for gyroid phenolic resins is 0.23 nJ whereas the one with diamond structure gives a value of 0.33 nJ. Consistently, the gyroid-structured epoxy gives a high energy dissipation value of 0.57 nJ, and the one with diamond structure could reach 0.78 nJ. These enhanced properties are attributed to the isotropic periodicity of the nanonetwork texture with plastic deformation, and the higher number of struts in the tetrapod diamond network in contrast to tripod gyroid, as confirmed by the finite element analysis.

An experimental investigation was performed on the coefficients of friction (COFs) and wear properties of pure water and oil-in-water (O/W) working fluids containing carbon nanocapsules (CNCs) with concentrations ranging from 0 to 1.0 wt.%. For the O/W working fluid, the ratio of oil to water was set as 6%. It was shown that for the water working fluid, the COF decreased by around 20% as the CNC content increased from 0 to 1.0 wt.%. In contrast, the wear volume increased by 50% as the CNC addition increased from 0 to 0.5 wt.%, but it fell to a value slightly lower than that achieved using only pure water (i.e., no CNCs) as the CNC content was further increased to 1.0 wt.%. For the O/W emulsion, the addition of 0.8 wt.% CNCs reduced the COF by around 30% compared to that of the emulsion with no CNCs. Overall, the results showed that while the addition of a small quantity (6%) of oil to the water working fluid had a relatively small effect on the wear performance, the addition of an appropriate quantity of CNCs (i.e., 0.8 wt.%) resulted in a significantly lower COF and an improved wear surface.

Carbon nanotube reinforced copper alloy (CNT/Cu) composites with high strength and good wear resistance have been developed using acid treatment, sintering processes and consolidation techniques. The effects of CNT reinforcement and grain size refinement on the mechanical properties and surface deformations of CNT/Cu composite coatings are investigated by means of nanoindentation and block-on-ring wear tests, respectively. High-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses reveal that the CNTs are firmly implanted in the Cu alloy due to the formation of Cu-oxides at the CNT-Cu interface. The effect of CNT addition on the CNT/Cu coating strength is significantly greater than that of grain size reinforcement. Finally, the present results indicate that the addition of CNTs to the Cu matrix reduces the surface deformations of the CNT/Cu composite coatings due to the formation of a carbonaceous solid-lubricant film at the contact interface during sliding.

The local viscoelastic properties of soft polishing pads with different usage durations are measured by a micro-scale mechanical analysis testing platform. The testing reveals stimulus-adaptive local viscoelasticity of soft pads under the activation of asperity contact. This phenomenon suggests asperity-dependent local modulus. Such an increase of local modulus induced by higher asperity provides a further enhancement effect to the planarization of surface asperity. Furthermore, the measurement outcomes suggest that the reaction of local micro-scale viscoelastic properties of the soft pad surface to the workpiece asperity will decay with usage time. The current study provides a detailed understanding of the aging effects for the soft pad and explains the performance decay during soft pad polishing from a local micro-scale interfacial perspective.

Bending characteristics of individual thin-walled carbon nanotubes (CNTs) are investigated through a novel in-situ nanoindentation in transmission electron microscopy. Unlike thick-walled CNTs, the graphitic layers of thin ones buckle into V-shaped kinks rather than Yoshimura ripples. These kinks are found to be entirely reversible without residual plastic deformation following unloading.

Hybrid carbon nanobuffers are developed by exploiting the ultra-hardness and wear-resistant properties of diamond-like carbon (DLC) coatings and the inherent viscoelasticity properties of vertically aligned carbon nanotubes (VACNTs). The viscoelastic properties of carbon nanobuffers incorporating thin-walled and thick-walled CNTs, respectively, are characterized by means of nanoindentation dynamic mechanical analysis tests. It is shown that the thin-walled nanobuffer has a better damping performance than the thick-walled nanobuffer due to its buckling-driven friction and post-buckling behaviors; particularly under large displacements. In addition, it is shown that under large indenter displacements, the VACNT arrays with DLC coatings display the improved stress distributions and enhanced strain energy dissipation performances due to the load transfer on the top of VACNTs. Molecular dynamics (MD) simulations are performed to investigate the roof-layer effect on damping behavior and structural deformation of the coated and uncoated VACNTs under nanoindentation. The results confirm that the VACNT with a DLC coating exhibits the significantly damping characterizations than the non-coated VACNT. Overall, the results presented in this study reveal the potential for tuning the damping performance of CNT-based nanobuffers through a careful control of the CNT size.

Necklace-shaped (NS) reinforced carbon nanotube/copper (CNT/Cu) composites are fabricated using the molecular-level decoration and consolidation techniques. The results show that the CNT/Cu composite with NS structures enhances the mechanical interlocking between the CNT arrays and the surrounding Cu matrix and yields a higher critical load, hardness and elastic modulus than conventional CNT-reinforced composites with a straight-shaped (SS) morphology. The mechanical properties and viscoelastic characterizations of the NS-reinforced CNT/Cu composites are examined via nanoindentation and dynamic mechanical analysis testing. It is shown that the embedded CNTs play a key role in raising the damping properties of the CNT/Cu composites by acting as a “load transfer” mechanism in releasing the excess stress within the Cu matrix.

Using classical molecular dynamics (MD) simulations, this study investigates the heat treatment induced coalescence of single-wall carbon nanohorns (SWCNHs) with different conical angles. It is found that the formation of a metastable Venturi-like structure from two individual nanohorns is the result of thermal motions around potential basins and successive Stone–Wales (S–W) transformations following initial graphene–graphene junctions. The coalescence and melting behaviors of the metastable nanohorn junctions are studied. The simulation results reveal that the coalescence temperature and the melting temperature are both dependent on the conical angle of the nanostructure. Specifically, it is found that the coalescence temperature and the melting temperature are lower in the nanohorn junctions with sharp nanohorns. Finally, the influence of the conical angle on the mechanical response of the metastable nanohorn junctions under tensile deformation is examined. The results show that the metastable synthesis with a sharper conical angle has a greater yielding strength than those with a blunt conical angle.

Vertically-aligned multi-walled carbon nanotube (MWCNT) arrays with various diameters and surface morphologies are fabricated to mimic gecko foot-hairs. The peeling behavior and interfacial adhesion characteristics of the MWCNT arrays are examined by means of depth-sensing nanoindentation technique. The results show that the adhesive force increases with an increasing surface roughness. However, the adhesive force significantly reduces with an increasing cap size due to a reduction in the number of contact sites between the MWCNT array and the indenter. Furthermore, the pull-off force of the MWCNT arrays is also found to increase with an increasing preload due to the corresponding deformation-induced increase in the contact area. Finally, it is shown that the contact angle of a water droplet on the MWCNT surface reduces with an increasing surface roughness. Thus, it is inferred that the enhanced adhesion of the MWCNT arrays with a greater surface roughness is due in part to an increased humidity and wettability of the MWCNT surface.

The mechanical and tribological properties of nanocrystalline nickel films affected by the grain size and preferred orientation are studied. Nickel films were produced by the supercritical electroplating process. The preferred orientations and the grain sizes of nickel films were determined by substrates (brass or phosphonic copper), reaction time and chamber pressure. The (111), (111)+(200) and (200) preferred orientation of nickel films were made. The XRD, SEM, AFM, and TEM tests were applied to confirm the preferred orientation and the grain size of a nickel film. The nanoindentation, nano-scratch and nano-wear test were used to obtain the informations regarding the hardness, friction coefficient and wear depth, respectively. The mechanical and tribological properties of nickel films are improved by reducing the grain size. Nevertheless, under smaller grain size conditions (i.e.

Carbon nanotube reinforced copper matrix (CNT/Cu) composites with high strength and good damping have been developed using acid treatment, sintering processes and consolidation techniques. Strengthening of the composites as a result of nanotube buckling has been demonstrated by experimental nanoindentation tests and molecular dynamics (MD) simulations. The experimental results show that the buckling behavior of additional CNTs in the CNT/Cu composites varies with the slenderness ratio of CNTs. Specifically, this study shows that the significant buckling behavior of CNTs in the CNT/Cu composites where the shorter CNTs (with a smaller slenderness ratio) give rise to a global buckling and the slender CNTs (with a larger slenderness ratio) induce local buckling. The MD simulation results reveal that the buckling behavior of the CNTs plays a key role in increasing the mechanical strength of CNT/Cu composites by acting as a “buffer” in releasing excess strain in the Cu matrix.

A series of experimental nanoindentation, nanowear and nanoscratch tests was conducted to investigate the relationship between the nanotribological characteristics of diamond-like carbon (DLC) and feed gas composition used for the deposition. The DLC films were deposited on silicon substrates in radio-frequency plasma enhanced chemical vapor deposition system with a mixture of hydrogen and methane gases. Raman spectroscopy results show that the integrated intensity ratios (I D /I G ) of each profile correlate with sp 2 /sp 3 ratios. The result also indicates that the hydrogen content in the source gas has a significant influence upon the sp 2 /sp 3 ratio and hydrogen-to-carbon ratio in DLC films. It is demonstrated that the sp 2 /sp 3 ratio decreases with increasing hydrogen content in the DLC film. Our result also reveals that a significant relationship between the hydrogen content and the nanotribological characterizations of the DLC films, namely lower hydrogen-to-carbon ratio leads to higher hardness, elastic modulus, friction coefficient, and lower wear depth. The surface reinforcement can be attributed to the fact that variation of surface energy arises from the different carbon hybridized states (sp 2 /sp 3 ratio), which improve the surface properties via the hydrogen content in the source gas and associated nanotribological characteristics.

Nanoindentation is a powerful technique for determining the mechanical properties of a material at the nanometer scale. In this study, the changes induced in the mechanical properties of a thin film by the presence of adsorbed multilayers are examined by performing nanoindentation tests with ultra-low indentation depths. The current findings suggest that the results obtained for the mechanical properties of thin films under nanoindentation will be overestimated if the effects of the adsorbed multilayers on reducing elastic recovery between the indenter and the substrate are not taken into consideration.

Characteristics of section structure, surface morphology, topography and tribology of catalyst nanoparticles synthesized with a microwave plasma chemical vapor deposition system on Ni/TaN/Si substrate are achieved by means of scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), ex situ atomic force microscopy (AFM), and nanoscratch techniques. In this study, we propose that the effect of catalyst nanoparticles on the growth of carbon nanotubes (CNTs) can be characterized by its tribological behavior. The results show that the temperature and the plasma treatment resulted in melting and roughening of the substrate surface, and promoted the formation of uniformly separated metal particles at 550 °C. This is due to the catalyst conglomerate forming particles with more uniform size under higher temperature. Our nanoscratch analysis indicates that the coefficient of friction of Ni nanoparticles/TaN/Si system increases from 0.77 to 1.2 while the pretreatment temperature increases from 450 °C to 550 °C. Furthermore, the scratch wear depth under ramping load show that higher pretreatment temperature leads to Ni nanoparticles with higher shear resistance, which enhances the well-aligned CNTs. These findings reveal that the role of pretreatment catalytic nanoparticles on the growth of CNTs can be identified by its nanotribological behavior.

This paper presents the use of molecular dynamics?(MD) simulations to investigate atomic-scale frictional behaviour between a roller and a slab under rolling?sliding conditions. The simulations consider both abrasive wear and non-abrasive wear during the rolling?sliding process. Different rolling?sliding conditions are simulated by implementing various separation distances between the roller and the slab and by changing the angular velocity of the roller. The frictional and normal forces acting at the interface between the roller and the slab, and the temperature of both operating components, are calculated during the rolling?sliding process. The relationships between the roller?slab friction phenomena and the rolling?sliding conditions are investigated. Finally, the rolling?sliding characteristics associated with a hard-on-soft rolling?sliding system are compared with those of a soft-on-soft rolling?sliding system.

This study adopts a classical molecular dynamics (MD) simulation with the realistic Tersoff many-body potential model to investigate the mechanical properties of gallium nitride (GaN) nanotubes. The investigation focuses primarily on the mechanical properties of (n,0) and (n,n) GaN nanotubes since these particular nanotubes represent two extreme cases. The present results indicate that under small strain conditions, mechanical properties such as Young's modulus are insensitive to the wrapping angle. Conversely, the wrapping angle has a significant influence upon these mechanical properties under large strain conditions. It is demonstrated that (9,0) GaN nanotubes are far less resistant to bond rotation. Under large tensile strain conditions, due to the unfavourable bond orientations induced by Stone–Wales (SW) transformation, the bonds in (n,0) GaN tubes quickly degenerate. Moreover, the present results suggest that the tensile strength of a nanotube is strongly sensitive to the temperature and strain rate. Regarding the fatigue test, this study uses a standard theoretical model to derive curves of amplitude stress versus number of cycles for the current nanotubes. The results demonstrate that the fatigue limit of GaN nanotubes increases with increasing temperature.

This study adopts the Tersoff–Brenner interaction potential function in a series of molecular dynamic (MD) simulations which investigate the mechanical properties under tensile loading of (10,0) zigzag, (8,3) chiral and (6,6) armchair single-walled carbon nanotubes (SWCNTs) of similar radii. The Young's modulus values of the (10,0), (8,3) and (6,6) nanotubes are determined to be approximately 0.92, 0.95, and 1.03 TPa, respectively. Of these nanotubes, the results reveal that the (6,6) nanotube possesses the best tensile strength and toughness properties under tension. Although it is noted that under small tensions, the mechanical properties such as Young's modulus are essentially insensitive to helicity, under larger plastic deformations, they may be influenced by helicity effects. Finally, the simulations demonstrate that the values of the majority of the considered mechanical properties decrease with increasing temperature and increasing vacancy percentage.

In this study, the radio frequency (RF) magnetron sputtering process is used to generate a PZT ferroelectric thin film on a silicon substrate. The surface characteristics of this lead zirconate titanate film Pb(ZrxTi1-x)O3 is then investigated by means of an atomic force microscopy (AFM) method. The relationship between the temperature of the rapid thermal annealing (RTA) process and the characteristics of the resulting microstructure is also examined. Various aspects of the surface are investigated, including its roughness, its microstructure and its fractal characteristics. The results demonstrate that higher annealing temperatures reduce surface roughness and promote increased grain size due to the phase transformations which are induced within the microstructure. The fractal analysis reveals that the fractal dimension, Ds, increases for larger AFM scan images, and that the value of Ds falls within the range 2.10-2.50 depending upon the scanned length/area and is calculated by the structure function. Finally, it is determined that the phase transformations which occur at higher annealing temperatures result in higher fractal dimensions.

An experimental investigation is performed into the tribological properties of mineral oil lubricants containing carbon nanocapsules (CNCs) additives with various concentrations (wt.%). Friction characteristics and wear behaviors at contact interfaces are examined by the block-on-ring tests, high-resolution transmission electron microscopy (HRTEM), and mapping (MAP) analysis. The results suggest that the addition of CNCs to the mineral oil yields an effective reduction in the friction coefficient at the contact interface. Molecular dynamics (MD) simulations clarify the lubrication mechanism of CNCs at the sliding system, indicating the tribological properties are essentially sensitive to the structural evolutions of CNCs.

This study employs classical molecular dynamics (MD) simulations to investigate the formation of single-walled carbon nanotube (SWCNT) T junctions via the melting and coalescence of two individual nanotubes. The simulations focus primarily on the synthesized multiterminals of (5, 5)-(9, 0)-(5, 5) and (5, 5)-(5, 5)-(5, 5) T junctions since these particular T junctions represent two extreme cases. The numerical results indicate that most of the cap-to-wall coalescence pathways identified for the nanotubes consist exclusively of Stone-Wales bond rotations. The thermal stability and melting behavior of the two T junctions are studied. It is found that for thermal treatment at high temperature, the (5, 5)-(9, 0)-(5, 5) T junction is more thermally stable than its (5, 5)-(5, 5)-(5, 5) counterpart since its structural dislocations and topological defects accelerate the onset of melting. The effects of the nanotube diameter and chirality on the mechanical responses of the T junctions under tensile and bending loads are also studied. The bending tests reveal an unexpected nanoplasticity mechanism in the T junction subjected to large bending deformation. This nanoplasticity effect causes the bonding geometry to transform from a graphitic $(s{p}^{2})$ structure to a localized diamondlike $(s{p}^{3})$ structure.

This paper adopts the Tersoff-Brenner many-body potential function to perform molecular dynamics simulations of the tensile and fatigue behaviors of hypothetical silicon-based tubular nanostructures at various temperatures, strain rates, and vacancy percentages. The tensile test results indicate that with a predicted Young's modulus of approximately $60\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, silicon nanotubes $(\mathrm{SiNTs})$ are significantly less stiff than conventional carbon nanotubes. It is observed that the presence of hydrogen has a significant influence on the tensile strength of $\mathrm{SiNTs}$. Additionally, the present results indicate that the tensile strength clearly decreases with increasing temperature and with decreasing strain rate. Moreover, it is shown that the majority of the mechanical properties considered in the present study decrease with an increasing vacancy percentage. Regarding the fatigue tests, this study uses a standard theoretical model to derive curves of amplitude stress versus number of cycles for the current nanotubes. The results demonstrate that the fatigue limit of $\mathrm{SiNTs}$ increases with a decreasing vacancy percentage and with increasing temperature.

Nanomechanics and real-time buckling deformation of an individual multi-walled carbon nanotube (MWCNT) were investigated through in situ nanoindentation within a transmission electron microscope (TEM). These in situ observations reveal a significant shell-to-Euler phase transformation in the buckling response of the nanotube. Objective evidences that the MWCNT possesses time-dependent characteristic were first suggested by combining in situ TEM nanoindentation performed strain rate influences on an individual MWCNT with classical molecular dynamics simulations. Structural evolutions and buckling instabilities for thin-wall and thick-wall CNTs are theoretically studied, indicating the role of the tube thickness and interwall van der Waals interactions in governing buckling behavior.

Indentation at very low load rate showed region of constant volume with releasing load in crystalline (c-)Si, indicating a direct observation of liquidlike amorphous phase which is incompressible under pressure. Signature of amorphization is also confirmed from load dependent indentation study where increased amount of amorphized phase is made responsible for the increasing elastic recovery of the sample with increasing load. Ex situ Raman study confirmed the presence of amorphous phase at the center of indentation. The molecular dynamic simulation has been employed to demonstrate that the effect of indentation velocities has a direct influence on c-Si during nanoindentation processes.

This study employs an atomic-scale model to investigate mechanical contact behaviors of a single asperity, particularly those which take place beyond the elastic limit threshold. The results obtained from the current model are found to be in good agreement with the predictions yielded by continuum theory as the contact behavior of the asperity transits from fully elastic to elastoplastic contact interface. Furthermore, the result shows that adhesion within the single asperity has the negligible influence during the loading stage; however, the adhesion force leads to the sizable clusters of copper atoms on the rigid plate during the unloading stage.

This study employs a series of experimental nanoindentation tests and molecular dynamics simulations to investigate buckling instabilities of carbon nanotube probes. It is found that the buckling mechanism varies as a function of probe lengths and initial inclination angles. The experimental results show that longer nanotubes buckle in local-buckling mode, whereas shorter nanotubes undergo global buckling. This study also suggests that the inclination angle also plays a key role in determining buckling behaviors of nanotube probes.

In this study, the nucleation mechanism of carbon nanocones is investigated using molecular dynamics (MD) simulations and structural analyses and is compared with that of carbon nanotubes. It is shown that the structural stability of carbon nanocones is sensitive to the cone apex angle. Specifically, an increase in the conical angle results in a moderate improvement in the structural stability of the nanocone as a result of a lower strain energy in the capped mantle. The simulation results also show that the melting temperature of the nanocone increases with increasing conical angle. Furthermore, it is observed that a metastable tube-like structure is formed in carbon nanocones with a lower conical angle at temperatures ranging from 2400 to 3600 K. Finally, the numerical simulations reveal that the mechanical properties of carbon nanocones under nanoindentation are strongly dependent on the conical angle. For carbon nanocones with a large conical angle, the high deformation-promoted reactivity and reversible mechanical response have been performed due to highly symmetrical networks.

This paper utilizes molecular-dynamics simulations to investigate the mechanical characteristics of a suspended (10, 10) single-walled carbon nanotube (SWCNT) during atomic force microscopy (AFM) nanoindentation at different temperatures. Spontaneous topological transition of the Stone-Wales (SW) defects is clearly observed in the indentation process. The present results indicate that under AFM-bending deformation, the mechanical properties of the SWCNT, e.g., the bending strength, are dependent on the wrapping angle. In addition, it is also found that the radial dependence of the reduced formation energy of the SW defects is reasonably insensitive only for the small tubes. However, for tube diameters greater than 2.4 nm [corresponding to the (18, 18) CNT], the SW defects tend to be more radius sensitive. The results indicate that the bending strength decreases significantly with increasing temperature. This study also investigates the variation in the mechanical properties of the nanotube with the density of C60 encapsulated within the nanotube at various temperatures. It is found that, at lower temperatures, the bending strength of the C60-filled nanotube increases with C60 density. However, the reverse tendency is observed at higher temperatures. Finally, the "sharpest tip" phenomena between the probe and the tube wall and the elastic recovery of the nanotube during the retraction process are also investigated.