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Mass sensing by nanomechanical resonators can be routinely performed for analytes of mass ranging from kDa to tens of MDa. Measurement of the heavier analytes (up to hundreds of GDa) that are relevant to viruses, and many biological and chemical complexes, still remains one of the main challenges to be solved. Some studies propose the heavy analyte identification by accounting for its mass, stiffness and binding effects. However, the necessity of using the sophisticated computational tools complicates their widespread use in the nanomechanical mass spectrometry. Here, we report on the heavy analyte mass spectrometry (~GDa) using the multimode nanomechanical resonators, which is directly applicable to analytes of arbitrary mass, stiffness and dimensions. This identification, based on the simultaneous measurement of the multiple by analyte induced resonant frequency shifts, only requires the analyte to resonator mass ratio between 0.001 and 0.02. We show that the analyte stiffness and binding effects must be considered for the lower mass ratios ( 0.02) the inaccuracies in determined mass are independent of both the analyte stiffness and binding effects, and increase with the mass of analyte. Validity of present results have been demonstrated by comparing predictions with the recent experimental measurements performed on the micro-/nanomechanical resonator-based mass spectrometers. Our findings, together with the provided software, which enables an easily accessible determination of the effects of analyte properties on the frequency response, present a novel paradigm in a design of the nanomechanical resonators for mass sensing in GDa range.

Due to their small sizes, compactness, low cost, high sensitivity, high resolution and extraordinary physical properties, nanoresonators have attracted a widespread attention from the scientific community. It is required that the nanoresonators can operate at desired but adjustable resonant frequencies. In this work, we present a novel active frequency tuning method utilizing a large change of the Young’s modulus (more than 50 %) and generated interlayer stress (up a few hundred of MPa) during a phase transformation of NiTi thin film deposited on an elastic substrate. We show that this tuning mechanism can allow one to achieve the extraordinary high fundamental resonant frequency tunability (~30 %). The impact of NiTi film thickness and dimensions on the first three consecutive resonant frequencies of the cantilever nanobeam is examined. In addition, developed theoretical model can be used as a simple guide for further design of novel tunable cantilever nanoresonators with thin films that cover only partially the entire cantilever length.

This article presents a mathematical model for the meshing of involute spur gears in mixed lubrication. The model is formulated by integrating a gear meshing model with a thermal tribofilm mixed lubrication model. The resulting model can produce a number of important meshing variables from which the gear meshing performance and the tooth surface damage may be assessed. The model is used to analyze the performance of a high-load and high-speed gear system under various degrees of mixed lubrication. The results show a stronger desire to use low-module and high-pressure-angle gears than that suggested in earlier studies under good lubrication conditions. The results also show the high importance of enhanced heat transfer design of the system to prevent or reduce the possibility of the gear system migrating into temperature-induced unfavorable lubrication conditions. Although the model is developed for spur gears and results are obtained around a nominal system, the relations of the gear meshing tribo...

A triboelectric generator (TEG) is a simple coupling combined with triboelectrification and electrostatic induction, which can convert mechanical energy into electrical energy and have the potential for self-powered device application. In this study, TEGs are fabricated consisting of a conductive textile (CT) layer (a fabric woven with polyester and stainless steel) and a polydimethylsiloxane (PDMS) layer. The CT friction layer is also used as a conductive electrode and designed with various surface morphologies, including unpatterned, dots, and lines with 1 and 2 cm spacings. Experimental results show that the TEG with an unpatterned CT layer produces an output voltage of 54.6 V and an output current of 5.46 µA. The patterned surfaces increase the effective contact area and friction effect between the CT and PDMS layers and hence enhance the output voltage and current to 94.4 V and 9.44 µA. Compared to the unpatterned CT layer, the pattern use of 1 cm spaced lines, 2 cm spaced lines, and dots improves the output voltage and current by 1.73, 1.68, and 1.24 times, respectively. Moreover, the TEG with 1 cm spaced lines generates a high output power density of 181.9 mW/m2.

This paper presents an elastic/plastic model that neglects strain hardening during loading, but accounts for the Bauschinger effect. These mathematical features of the model represent reasonably well the actual behavior of several materials such as high strength steels. Previous attempts to describe the behavior of this kind of materials have been restricted to a class of boundary value problems in which the state of stress in the plastic region is completely controlled by the yield stress in tension or torsion. In particular, the yield stress is supposed to be constant during loading and the forward plastic strain reduces the yield stress to be used to describe reversed yielding. The new model generalizes this approach on plane stress problems assuming that the material obeys the von Mises yield criterion during loading. Then, the model is adopted to describe reversed yielding in thin hollow discs subject to external pressure.

Determining film pressure by solving the Reynolds equation is more effective than conducting bearing experiments or computational fluid dynamics simulations. The Reynolds equation can be solved easily in a numerical model; however, the accuracy of each model is dominated by the orifice discharge coefficient. This study compared two orifice flow models in inherent orifice restrictors and investigated the influences of geometry and flow parameters on the discharge coefficient. The results indicate that both orifice flow models can be used in inherent orifice restrictors, and the discharge coefficient of orifice-type restrictors is sensitive to the orifice diameter and film thickness.

A semi-analytic method for elastic/plastic shrink-fit analysis and design is developed. In contrast to many available semi-analytic methods, it is assumed that the outer disc obeys the von Mises yield criterion and its associated flow rule. The inner component of the assembly is purely elastic. The complete solution consists of three principal steps. First, the elastic/plastic solution in the outer disc is outlined. The only output of this solution required for the next step is the circumferential strain at the inner radius. It is shown that this strain can be found without having the strain distribution in the plastic region of the disc. This significantly simplifies the design of shrink fits. Moreover, only two parameters related to the outer disc (Poisson’s ratio and the dimensionless inner radius) are involved in numerical part of the elastic/plastic solution in the outer disc. Second, the found circumferential strain at the inner radius is used in conjunction with an analytic solution in the inner component of the assembly to match the two solutions. Any conventional design criterion can be adopted at this stage to determine optimal conditions. The complete solution involves several independent parameters. However, this does not cause any difficulty for design since these parameters are involved in analytic expressions. The final step is only necessary if the distribution of strains in the plastic region of the outer disc should be found.

Metallic annular discs with their outer boundary fully constrained are studied with newly derived semi-analytical solutions for the effects of thickness variations under thermal loading and unloading. The plane stress and axisymmetric assumptions were adopted, and the thickness of the disk depends on the radius hyperbolically with an exponent n. Furthermore, it is assumed that the stress state is two dimensional and temperature is uniform in the domain. The solutions include the elastic, elastic-plastic and plasticcollapse behavior, depending on the values of temperature. The von Mises type yield criterion is adopted in this work. The material properties, Young\'s modulus, yield stress and thermal expansion coefficient, are assumed temperature dependent, while the Poisson\'s ratio is assumed to be temperature independent. It is found that for any n values, if the normalized hole radius a greater than 0.6, the normalized temperature difference between the elastically reversible temperature and plastic collapse temperature is a monotonically decreasing function of inner radius. For small holes, the n values have strong effects on the normalized temperature difference. Furthermore, it is shown that thickness variations may have stronger effects on the strain distributions when temperature-dependent material properties are considered.

A semi-analytic solution for the elastic/plastic distribution stress and strain in a thin annular disc subject to pressure over its inner radius is presented. It is assumed that a pressure-dependent yield criterion and its associated flow rule are valid in the plastic zone. Thus, the material is plastically compressible, which is a distinguished feature of the solution. Also, in contrast to most studies on elastic/plastic deformation of thin plates and discs under plane stress conditions, the flow theory of plasticity is adopted in conjunction with a smooth yield surface. Numerical methods are only necessary to evaluate ordinary integrals and to solve simple transcendental equations. It is shown that the stress path is not proportional and, therefore, the application of deformation theories of plasticity widely used to calculate the distribution of stresses and strains in thin plates and discs is not justified.

Topical fluoride treatment prevents dental caries. However, the resulting calcium-fluoride-like deposits are soft and have poor wear resistance; therefore, frequent treatment is required. Lasers quickly heat surfaces and can be made portable and suitable for oral remedies. We examined the morphology, nanohardness, elastic modulus, nanowear, and fluoride uptake of fluoride-treated enamel followed by CO2 laser irradiation for 5 and 10 sec, respectively. We found that laser treatments significantly increased the mechanical properties of the calcium-fluoride-like deposits. The wear resistance of the calcium-fluoride-like deposits improved about 34% after laser irradiation for 5 sec and about 40% following irradiation for 10 sec. We also found that laser treatments increased fluoride uptake by at least 23%. Overall, laser treatment significantly improved fluoride incorporation into dental tissue and the wear resistance of the protective calcium-fluoride layer.

This paper aims to manufacture aluminum alloy metals with gradient micro-structures using hot extrusion process. The extrusion die is designed to have a straight channel part combined with a conical part. Materials pushed through this specially-designed die generate a non-uniform velocity distribution at cross sections inside the die and result in different strain and strain rate distributions. Accordingly, a gradient microstructure product can be obtained. At first, temperature, effective strain, and effective strain rate distributions at the die exit are discussed for different inclination angles in the conical die using the finite element analysis. Then, hot extrusion experiments are conducted to obtain aluminum alloy products with gradient micro-structures. The effects of the inclination angle on the grain size distribution at cross sections of the products are also discussed.

In this paper, a Dual-Axis Long-Traveling Nano-Positioning Stage (DALTNPS) is presented. In order to extend the traveling and increase the accuracy, the two sorts of stages, a traditional ball-screw stage and a three-degrees-of-freedom (3-DOF) piezo-stage, were composed. The traditional ball-screw stage which is composed of two guide-ways and a ball-screw at each axis is a long-travel stage, and the 3-DOF piezo-stage, which is composed of three piezoelectric actuators and four translation–rotation mechanisms, is a high precision stage. In addition, a 3-DOF measuring system and a PID controller are composed of a 3-DOF closed-loop controller and applied to implement the DALTNPS. The measuring system which is composed of two laser interferometers and two plane mirrors is a 3-DOF optical measuring system. Thus, the position at the x and y axes and the rotation around the z axis can be obtained and they are the responses of DALTNPS. Finally, the experiment results evidence that the DALTNPS is characterized by long-travel, high linear accuracy, high rotation accuracy, high contouring accuracy and high motion speed.

In this paper, a new optical 3‐dimensional vibrometer is presented. This system is composed of two orthogonally set up corner cubes (CC), a collimated laser source, two quadrant detectors (QD) and three beam‐splitters (BS). The corner cubes are designed to be fixed to the vibrating object and reflect the laser source onto the quadrant detectors. Due to the optical characteristics of the corner cubes, the measuring results of the QD can be magnified twice and it is not affected by micrometer‐angle. So, the three‐dimensional vibration amplitude can be obtained. The resolution is about 50 nm. This system is characterized by three‐dimensional measurement, high resolution, low cost, simple set up and wide bandwidth.

This paper describes the successful development of a middle-range six-degrees-of-freedom stage, using the features of a flexible structure. The system includes two parts: a middle-range positioning X— Y stage and a four-degrees-of-freedom stage. The flexible structure of the four-degrees-of-freedom stage is built from two kinds of flexible bodies: circular hinges and a new two-degrees-of-freedom flexible body. The four-degrees-of-freedom stage was designed to compensate movement errors including linear displacement, pitch, and roll errors. The linear displacement reaches 20 mm along the X-axis, 20 mm along the Y-axis, and 5 μm along the Z-axis. The rotation angle around the X-axis (θ x), Y-axis (θ y), and Z-axis (θ z) were all 10 arcsec. A novel six-degrees-of-freedom measuring system was also designed. Precision feedback control is demonstrated in a series of experiments performed using the proposed measurement system.

Tooth enamel is a hybrid organic-inorganic bionanocomposite comprised predominantly of enamel rods. Understanding the effects of anti-caries treatment on the biomechanical properties of these rods is essential in developing effective caries prevention strategies. Calcium fluoride-like deposits play an important role in caries prevention and their nanotribological properties have a direct effect upon their long-term effectiveness. Accordingly, this study utilizes a variety of techniques, namely nanoindentation, nanoscratch tests, nanowear tests and atomic force microscopy (AFM), to characterize the mechanical and tribological properties of single enamel rods before and after topical fluoride application. The results show that the CaF(2)-like deposits formed on the enamel surface following fluoride application increase the coefficient of friction of the enamel rods, but decrease their critical load and nanohardness. As a result, the nanowear depth of the treated enamel surface is around six times higher than that of the native enamel surface under an applied load of 300 microN. Following the removal of the surface deposits, however, the modulus of elasticity and wear depth of the underlying enamel surface are found to be similar to those of the original enamel surface. However, a notable increase in the surface roughness is observed.

At present, the accuracy of precision manufacture is most affected by straightness errors, so the measurement and compensation of these errors are very important. In the current paper, three measurement systems for straightness are presented; they are characterized by simple set-up, online measuring, low cost, and sub-micrometre accuracy achieving 0.2 μm. Experimental results show that these three measurement systems can be applied to implement a compensation system which comprises one among them, an Elmo controller, and a dSPACE controller, and accomplish static compensation and dynamic compensation in the dual linear-axis stage. The accuracies of the static and dynamic compensation achieve ± 1 μm and ± 2.5 μm, respectively.

In this study, a simple and high-resolution four-degrees-of-freedom (4-DOF) motion error measuring system based on DVD pickup has been proposed. It can simultaneously measure the horizontal straightness error and three angular errors of a single-axis linear moving platform. The horizontal straightness error is measured based on the focus technique of DVD pickup and the inverse algorithm is used to solve pitch, yaw, and roll angular errors through the kinematic analysis. The grating is mounted on the moving axis of a single-axis linear moving platform and reflects incident laser beam into several diffractive rays. Photodiode IC (PDIC) of DVD pickup is set up for detecting the focus error signal (FES) of zero-order diffraction ray from grating and quadrant detectors are set up for detecting the position of ±1st-order diffraction rays from grating. The 4-DOF motion error measuring system detected the three angular errors with a related accuracy of about ±1 arc sec for a measuring range of ±100 arc sec, and detected horizontal straightness with a related accuracy of about ±2 μm for a measuring range of ±150 μm.

In this paper a method is developed for straightness measurement of a linear guide by using a straightness self-compensating stage with an optical straightness measuring system, an eddy current sensor, and a cross-roller type compensation stage. Both the compensation stage and the optical straightness system were set up on a scanning stage to measure the straightness error of the scanning stage. The measured straightness error was fed back to the control system to compensate directly in real time. Thus, straightness of a linear guide without the added straightness error of the scanning stage could be measured. The Hewlett Packard laser straightness calibration system was used to verify the real-time compensated results. Straightness error of the scanning stage was compensated from the worst straightness error of 20 μm/150 mm to 0.9 μm/150 mm. The eddy current sensor measured straightness of the linear guide and the measured result matched the result obtained by the coordinate measuring machine.

In this paper, it presents a useful dual-axial five-degrees-of-freedom measuring system with five degrees of freedom (DoFs) for the simultaneous measurement of five-DoF motion errors of a nano-stage. The system integrates a miniature fibre-coupled laser interferometer with specially designed optical paths and quadrant detectors, capable of measuring five-DoF motion errors. It presents a new precision five-DoF measuring system which has been developed and implemented for the simultaneous measurement of five-DoF motion errors (two linear positions, as well as pitch, roll, and yaw) of a nano-stage. In this paper, the five-DoF laser interferometer was produced by designing the optical path from the one-DoF laser interferometer. The system employs two three-DoF interferometers to detect two position errors and three angular errors of the nano-stage. The experimental set-ups and measuring procedure and a systematic calculated method for the error verification are presented as well. The resolution of measuring the angular errors component is about 0.06″.

To minimize the size of a stage with more DOF motion, this paper concentrates on the design, manufacturing process and control of a 5DOF thin coplanar nanometer-scale stage with high accuracy and multiple DOF motion. This paper uses the features of a flexible structure to develop a 200 mm × 200 mm × 35 mm thin coplanar nanometer-scale stage with 5DOF that allows the increase or decrease of axis action in accordance with various needs. The flexible structure of the thin coplanar nanometer-scale stage includes a cylindrical flexible body and an arc flexible body. The thin coplanar nanometer-scale stage allows for three-translational and two-rotational motions and is provided with eight piezoelectric actuators—one on the X -axis, another on the Y -axis, and the others on the Z -axis. The displacement characteristics of the output member of the stage were measured with the built-in capacitive sensors. It also used an analysis and identification controller design method for piezoelectric actuated systems. From the results, it can be seen that the performance of this controller is good and 10 nm controlling error of the step input can be obtained. The controlling error of the rotational angle is about 0.004 arcsec.

Chemical mechanical polishing (CMP) has become a primary technique for planarization of semiconductor wafers in sub-micro device fabrication. A physical CMP model combines the effects of grain flow hydrodynamic lubrication, pad roughness, and asperity contact between wafer and pad. In this study, an improved CMP model, considering both the grain flow with roughness effects and the micro-contact mechanism, is proposed. The model applies the average lubrication equation with partial hydrodynamic lubrication theory and considers the elastic—plastic micro-contact theory. The applied load acting on the wafer is balanced by the slurry pressure in the non-contact area, and the surface asperity contact force in the contact area. The effects of the CMP parameters including applied load, rotation speed, particle size, and pad roughness are studied and discussed. The simulation results compare well with experimental data in the literature and contribute to further understanding in wafer—pad contact mechanism.

This paper proposes a method that combines molecular dynamics with finite element deformation model (MDFM) to calculate the stress and strain of a single crystal nickel material that occur during the nano-scale cutting by concial tool. The flow stress–strain curve used in the MDFM model was obtained by nano-scale tension simulation using molecular dynamics method in this paper. Since the Young's modulus of the nano-scale single crystal nickel material is different from macroscopic scale. Therefore, the Young's modulus of the single crystal nickel material used in the MDFM model was obtained through a nano-indentation test under very low indentation loading. The MDFM only requires the elastic–plastic constitutive equation. The position and displacement components of atom in any temporary situation during nano-scale cutting could be found by using the 3D MD simulation. The atom is regarded as a node and the lattice is regarded as an element. The shape function concept of FEM is applied to calculate the strain of element from atom displacement. After simulation, it can be found that the accumulation behavior of cutting chip done by nano-cutting is quite similar to macroscopic cutting. This paper also finds that residual stress and residual strain will remain on the machined surface of single crystal nickel after cutting.

This paper presents the design, fabrication and testing of a PZT bimorph actuated atomizer. The atomizer with the size of 43 mm × 37 mm × 7 mm is composed of a PZT bimorph actuator, which is sandwiched by top and bottom flow channel plates and cover shields. The micronozzle plate is attached onto the top cover shield. UV laser machining and micro electrical discharge machining (μEDM) are applied to fabricate the micronozzles with different geometry. The experimental results indicate that we can justify the frequency response of flow rate by acoustic pressure analysis. The peak flow rates occur at higher order resonances, and the operating pressure is less than 0.1 MPa, which is much lower than that of existing atomizers. Also, the influence of flow rate by changing the distance between the PZT bimorph and the nozzle plate, as well as the flat plate on the bottom cover shield are discussed. The maximum flow rate of 8 ml/min is obtained by using the μEDM-made micronozzle plate, when the atomizer is driven with square pulses at 7 kHz with 50% duty cycle and 27 V peak-to-peak.

This study investigates the effects of asperity interactions on the mean surface separation and real contact area of rough surfaces containing elliptical asperities with Gaussian and non-Gaussian height distributions. The elastic-plastic contact behavior of surfaces with elliptical asperities with both single-mode and bimodal height distributions are studied. The results indicate that the effects of asperity interactions become more pronounced as the effective radius ratio of the asperities increases. The findings also reveal that the real contact load, the real contact area, and the surface contact mode observed for elliptical asperities are significantly different from those noted for spherical asperities. Furthermore, it is found that the form of the non-Gaussian height distribution has a significant effect on the contact mode of rough surfaces. Specifically, the contact mode of surfaces with a negatively skewed height distribution is found to be more elastic than that of surfaces with a Gaussian height distribution.

This paper presents an experimental investigation of the influence of scuffing conditions on two-roller test rig. The prediction of Scuffing load capability model for the gear oils containing molybdenum dithiocarbomate (MoDTC) was developed based on the response surface methodology. A good agreement between the predicted and actual scuffing resistance was observed within ±5% significance level.

Thermosonic ball bonding is widely used in interconnections to integrated circuits. This work used a thermosonic bonding machine and a shear tester to study the effects of preload, preheat temperature, ultrasonic power, welding time, and wire diameters on shear force. The results reveal that shear force of thermosonic wire bonding can be elucidated from the viewpoint of interfacial microcontact phenomena such as energy intensity, interfacial temperature, and real contact area. As the energy intensity is increased, the shear force increases, reaches a maximum, and then decreases. The energy intensity at which the shear force reaches maximum is called the saturated energy intensity. After saturation (that is, the establishment of maximum atomic bonds), any additional energy input will damage the bonding, decreasing the shear force. The saturated energy phenomenon can be further confirmed by using wires with different diameters. It is also observed that the saturation phenomena, and thereby the optimal shear...

This paper adopts an atomic-scale model based on the nonlinear finite element formulation to analyze the stress and strain induced in a very thin film during the nanoindentation process. The deformation evolution during the nanoindentation process is evaluated using the quasi-static method, thereby greatly reducing the required computation time. The finite element simulation results indicate that the microscopic plastic deformation in the thin film is caused by instability of its crystalline structure, and that the magnitude of the nanohardness varies with the maximum indentation depth and the geometry of the indenter.Copyright © 2004 by ASME

This study investigated the surface topographical changes during running-in. A theoretical model, which is composed of Johnson translatory system and a microscopic wear model, was used to describe the changes of surface roughness during running-in for general surfaces. Running-in tests were conducted for engine bores with different surface height distributions in order to understand surface topographical changes and validate the theory. Experimental results show that the theoretical model provides a good indication of changes of surface topography for surfaces with different types of initial height distributions.

The ball bearing is widely used on many moderate speed rotating systems due to its low starting friction and high load capacity. However, the heat generation caused by high-speed operation has been the limiting factor for increasing the speed limit of many high-speed ball bearing applications. The objective of this study was to predict the heat generation and temperature rise of ball bearings operating at moderate rotating speed. A series of experiments have been conducted to investigate the effects of oil-mist and oil-air lubrication on temperature rise of ceramic and steel ball bearings. From these experimental results, the previous theoretical model for temperature rise of ball bearings was modified for the moderate speed operation conditions. A computer code was developed accordingly to investigate the relationship between preload, ball bearing parameters, heat generation and temperature rise. The effect of temperature on lubricant viscosity was also taken into account. Results from the improved theor...

A closed-form average lubrication equation for thin film grain flow with the effects of surface roughness is derived. This equation is based on Haff’s grain flow theory and also the flow factors proposed by Patir and Cheng. The flow factors, derived by the perturbation approach and coordinate transformation, are expressed in terms of surface characteristics (three characteristics for each surface: roughness orientation, Peklenik number and standard derivation) and particle size. Finally, the flow factors under different surface characteristics and particle size are discussed.

In aerostatic bearing analysis, determining film pressure by solving the Reynolds equation in a numerical model is more effective than conducting bearing experiments or performing computational fluid dynamics (CFD) simulations. However, the discharge coefficient of an orifice-type restrictor is generally a given number that dominates model accuracy. This study investigated the influence of geometry and flow parameters on this discharge coefficient. The results indicate that this discharge coefficient is sensitive to the orifice diameter and film thickness and that the effects of the supply pressure, bearing radius, supply orifice length, supply passage diameter, conicity depth, and conicity angle can be disregarded. This study also built a surrogate model of this discharge coefficient based on the orifice diameter and film thickness by using artificial neural networks (ANNs).

This study uses molecular dynamics simulations to elucidate the spreading behavior of a liquid droplet on a rough solid surface. The Lennard–Jones potential energy model is adopted as the interaction model between the liquid and the solid molecules. The paper considers two types of rough surface: periodic and random. These surfaces are characterized by their roughness height and their spatial variation. For a periodic surface, the roughness height is defined by the amplitude, A, while for a random surface, it is defined in terms of the standard deviation of the roughness height, σ. Regarding the spatial variation of the surface, a periodic surface is characterized by the wavelength, λ, while the random surface is characterized by its autocorrelation length, L . Simulation results indicate that the characteristics of the rough surface can significantly influence spreading behavior, in terms of final equilibrium time, spreading radius, and spreading topography. It is observed that the effects of roughness h...

Ball-bearings are widely used on many high-speed rotating systems. However, heat generation and dynamic loading caused by high-speed operation have been the limiting factors for increasing the speed limit of many high-speed ball-bearing applications. Therefore, providing proper lubrication and preload to reduce heat generation effectively is a major task for high-speed ball-bearings. Recently, oil-air lubrication has been used on high-speed ball-bearings because of precise oil quantity control and high cooling efficiency. However, the fluctuation in oil supply resulting from the periodic oil feeding is unfavourable. In this study, equipment for measuring the fluctuation in the oil supply was established. The operation parameters affecting the stability of the oil supply for an oil-air lubrication system were experimentally studied. A test rig for high-speed ball-bearings was also developed. Tests were conducted to study the effects of the preload, oil quantity, air flowrate and rotating speed on the bearing temperature rise. The operating conditions that provide a stable oil supply and low bearing temperature rise were established.

Wire bonding is a popular joining technique in microelectronic interconnect. In this study, the effects of applied load, surface roughness, welding power and welding time on bonding strength were investigated using an ultrasonic bonding machine and a pull tester. In order to relate bonding strength to contact phenomena, the asperity model was used to compute real contact area and flash temperature between the wire and the pad. The experimental results show that a decrease in load or ultrasonic power produces a larger weldable range in which the combination of operation parameters allow the wire and pad to be welded. Regardless of roughness and applied loads, the bond strength increases to a maximum with increases in the welding time, and then decreases to fracture between wire and pad. The theoretical results and experimental observations indicate that bond strength curves can be divided into three periods. The contact temperature plays an important role in bonding strength in the initial period, and surface roughness is the dominant factor in the final period. The maximum bonding strength point occurs in the initial period for different loads and surface roughness values. Our results show that bond strength of ultrasonic wire bonding can be explained based on the input energy per real contact area.

In this paper, a dual-beam laser interferometer measurement system for precision machine tools was presented. The straightness measurement module and the angular measurement module were combined to form this measurement system such that the operations of precision machine tools, the positioning, vertical straightness, horizontal straightness, pitch and yaw, can be obtained. The resolution of the positioning, straightness and angle has achieved 0.1 nm, 1 nm and 0.1 arcsec, respectively. The performance of this measurement system has been proved by experiments.

This paper aims to manufacture magnesium alloy metals with gradient micro-structures using hot extrusion process. The extrusion die was designed to have a straight channel part combined with a conical part. Materials pushed through this specially-designed die generate a non-uniform velocity distribution at cross sections inside the die and result in different strain and strain rate distributions. Accordingly, a gradient microstructure product can be obtained. Using the finite element analysis, the forming temperature, effective strain, and effective strain rate distributions at the die exit were firstly discussed for various inclination angles in the conical die. Then, hot extrusion experiments with a two stage die were conducted to obtain magnesium alloy products with gradient micro-structures. The effects of the inclination angle on the grain size distribution at cross sections of the products were also discussed. Using a die of an inclination angle of 15°, gradient micro-structures of the grain size decreasing gradually from 17 μm at the center to 4 μm at the edge of product were achieved.

Quite a general elastic/plastic material model including evolution equations for internal variables is adopted to predict the distribution of material properties and springback in plane strain bending under tension at large strains. A transformation equation to connect Lagrangian and Eulerian coordinates is used to reduce the original boundary value problem to a system of hyperbolic equations. This system is then solved by the method of characteristics combined with a finite difference scheme. In a particular case of elastic/plastic hardening materials (in this case the only internal variable is the equivalent plastic strain) an analytic solution is available in the literature. Using this solution it is demonstrated that the accuracy of the numerical method is very high.

The AFM combined nanoindentation was performed to observe the ultrastructure of enamel rod from various section plans and positions while probing their mechanical and tribological properties of the area. The nanohardness and the elastic modulus of the head region of the enamel rods are significantly higher than that of the tail region and the axial-sectional plane. Both nanohardness and elastic modulus gradually decrease from enamel surface toward dentino-enamel junction. Such a variation correlates well with the decreasing trend of calcium composition from our element analysis. The friction coefficient and nanowear of the enamel showed an inversed trend to the hardness with respect to their relative topological position in the long axis of enamel rod toward DEJ. The relationship between the nanowear depth and the distance from the outer enamel surface to DEJ presented exponential function. The results presented clarify the basic nanomechanical and nanotribological properties of human enamel rods and provide a useful reference for the future development of dental restorative materials.

A one-dimensional analysis for lubrication between the piston ring and cylinder wall has been developed. A fully flooded inlet condition and axisymmetric geometry are considered. The piston ring is treated as a reciprocating, dynamically-loaded bearing with combined sliding and squeeze motion. A system of two nonlinear differential equations is used to model the lubrication including the Reynolds cavitation boundary condition. A numerical procedure is then developed to obtain the cyclic variations of film thickness, frictional force, power loss, and oil flow across the ring. Results are presented for a typical automotive engine. The effects of ring profile, ring tension, and engine speed are examined. It is shown that this analysis can be used to study the influence of ring design parameters in order to improve the design of the ring pack in reciprocating engines.

Most studies of piston-ring lubrication assume fully flooded lubrication in the cylinder-bore and piston-ring conjunction. However, the lubricant supply is not always adequate for fully flooded lubrication. This study incorporates the effects of lubricant starvation into the one-dimensional piston-ring analysis developed earlier and applies it to a complete ring pack. A system of three nonlinear equations is derived to solve the starved lubrication problem. A postulate for lubricant transport in a complete ring pack is also proposed. A computer code is developed to apply the starved lubrication model to a complete ring pack. The findings reveal that lubricant starvation has an important effect on the minimum film thickness of a ring pack, especially at mid-stroke for compression rings. The role of oil-control rings and the evaluation of ring performance as a complete ring pack are also discussed.

A new system for measuring the errors of three-axis machines is presented in this paper. It is composed of a planar encoder system and a magnetic telescoping ball bar. The individual signals of three-axis displacement can be simultaneous obtained. The errors of the three-axis machines, geometric error, kinematic error, wobble error and volumetric error, can be effectively measured. The system is characterized by short set up time, low capital requirement, high measuring speed and high accuracy.

In this paper, it was successfully developed a nano- measuring machine stage. It was used the features of a flexible structure to develop the nano-measuring machine stage. This stage includes two parts: one is a long range positioning X-Y stage and the other one is a four degrees-of-freedomicro-range stage. The flexible structure of the four degrees-of-freedom micro-range stage was included two kinds of an arc flexible body and a new two degrees-of- freedom flexible body. The micro-range stage was designed to compensate the moving errors such as vertical straightness error, pitch error and roll errors and its all moving range is 20 mm times 20 mm times 11 mum. Precision feedback is provided by the six degrees-of-freedom measuring system with integrating the three plane mirror interferometers and a two degrees-of-freedom angular sensor.

This work considers the anode at the indium-tin oxide (ITO)/poly[2-methoxy-5-(2'-ethylhexyloxy)-l,4-phenylene vinylene] (MEH-PPV) interface in polymer light-emitting diodes (PLEDs). The surface morphology of ITO is studied by scanning probe microscopy (SPM). The mechanical properties of ITO and MEH-PPV are measured by nanoindentation. The results indicate that the surface roughness, defined as the root-mean-square of the surface height on the surface of the ITO substrate, influences the injection of hole-carriers. The injected current is dominated by the tunneling of hole-carriers at the low bias. Increasing the effect contact area at the ITO/MEH-PPV interface lowers the barrier to the injection of holes through the ITO anode to the MEH-PPV light-emitting layer.

Existing plane stress solutions for thin plates and disks have shown several qualitative features which are difficult to handle with the use of commercial numerical codes (non-existence of solutions, singular solutions, rapid growth of the plastic zone with a loading parameter). In order to understand the effect of temperature and pressure-dependency of the yield criterion on some of such features as well as on the distribution of residual stresses and strains, a semi-analytic solution for a thin hollow disk fixed to a rigid container and subject to thermal loading and subsequent unloading is derived. The material model is elastic-perfectly/plastic. The Drucker-Prager pressure-dependent yield criterion and the equation of incompressibity for plastic strains are adopted. The distribution of residual stresses and strains is illustrated for a wide range of the parameter which controls pressure-dependency of the yield criterion.