Effect Of Undercut Research Articles

Notch effect identification and fatigue life prediction of undercut weld

Undercut, as a typical surface imperfection at the weld toe, significantly impacts the weld fatigue life. Neither the ISO5817 standard for imperfection level definition nor the traditional fatigue life prediction methods for welds can accurately identify the undercut effect on weld fatigue life. To solve this problem, a new stress concept and life prediction method are proposed, which can predict the fatigue life of undercut welds in both linear elastic and elastic–plastic conditions. Its prediction accuracy is verified by test data and engineering examples.

Correction to: Effect of undercut on the lower bound stability of vertical rock escarpment using finite element and power cone programming

Correction to: Effect of undercut on the lower bound stability of vertical rock escarpment using finite element and power cone programming

Effects of Mask Material on Lateral Undercut of Silicon Dry Etching.

The silicon etching process is a core component of production in the semiconductor industry. Undercut is a nonideal effect in silicon dry etching. A reduced undercut is desired when preparing structures that demand a good sidewall morphology, while an enlarged undercut is conducive to the fabrication of microstructure tips. Undercut is related to not only the production parameters but also the mask materials. In this study, five mask materials-Cr, Al, ITO, SiNx, and SiO2-are chosen to compare the undercut effect caused by the isotropic etching process and the Bosch process. In the Bosch process, the SiNx mask causes the largest undercut, and the SiO2 mask causes the smallest undercut. In the isotropic process, the results are reversed. The effect of charges in the mask layer is found to produce this result, and the effect of electrons accumulating during the process is found to be negligible. The undercut effect can be enhanced or suppressed by selecting appropriate mask materials, which is helpful in the MEMS process. Finally, using an Al mask, a tapered silicon tip with a top diameter of 119.3 nm is fabricated using the isotropic etching process.

Effect of undercut on the lower bound stability of vertical rock escarpment using finite element and power cone programming

Effect of undercut on the lower bound stability of vertical rock escarpment using finite element and power cone programming

Stress Analysis of Improper Femur Cut in Total Knee Arthroplasty by Finite Element Method

ABSTRACTPrecise bone cut is fundamental in total knee arthroplasty. However, notching of anterior femoral is not uncommon in clinical practice. Reviewing the article, notching and its complication may reach up to 30% and 2.5%, and there is scanty study of notching on the femoral strength. We therefore conduct the finite element analysis to elucidate the effect of notching on femoral mechanical strength. The computerized tomography images were used as the basis to develop the knee model, which was assumed mainly to consist of cortical and cancellous bones. For the implant joint, Zimmer data was considered partly as the basis to develop the model. This study investigated the femoral improper cut effect on the surgery with a static standing condition. The results show that the anterior femoral cut should be undercut 2 mm to overcut 1 mm during the surgery, in order to prevent bone materials from yielding. The exposure of the cancellous bone may cause bone materials to yield when the femur overcut was 2 mm; the cancellous bone may load too much and result in a fracture when the undercut was 3 mm. The effect of undercut, which was rarely discussed, was particularly addressed in our study. Precise femoral cut is crucial for the longevity of total knee arthroplasty.

Influence of undercut and surface crack on the stability of a vertical escarpment

Stability of vertical escarpments has been the subject of discussion for long time. However, available literature provides scarce knowledge about the effect of the formation of undercut and surface cracks on the stability of a vertical escarpment. The present study deals with a systematic analysis of the effect of surface cracks and undercut on slope stability using finite element based lower bound limit analysis. In the present analysis, the nondimensional stability factor (γH/c) is used to inspect the degrading effect of undercut and cracks developed at different offset distances from the edge of the vertical escarpment. Failure patterns are also studied in detail to understand the extent and the type of failure zone which may generate during the state of collapse.

Effect of Undercut on the Characterization of the Mechanical Properties of Silicon Nanocantilevers with Dynamic and Static Test

The elastic mechanical properties of silicon nanocantilevers are of prime importance in biotechnology and nanoelectromechanical system (NEMS) applications. In order to make these applications reliable, the exact evaluation of the effect of the undercut on the mechanical properties of silicon nanocantilevers is essential and critical. In this paper, a numerical-experimental method for determining the effect of the undercut on resonant frequencies and Young’s modulus of silicon nanocantilevers is proposed by combining finite element (FE) analysis and dynamic frequency response tests by using laser Doppler vibrometer (LDV) as well as static force-displacement curve test by using an atomic force microscope (AFM). Silicon nanocantilevers test structures are fabricated from silicon-on-insulator (SOI) wafers by using the standard complementary metal-oxide-semiconductor (CMOS) lithography process and anisotropic wet-etch release process based on the critical point drying, which inevitably generating the undercut of the nanocantilever clamping. Combining with three-dimensional FE numerical simulations incorporating the geometric undercut, the dynamic resonance tests demonstrate that the undercut obviously reduces resonant frequencies of nanocantilevers due to the fact that the undercut effectively increases the nanocantilever length by a correct value ΔL. According to a least-square fit expression including ΔL, we extract Young’s modulus from the measured resonance frequency versus the effective length dependency and find that Young’s modulus of a silicon nanocantilever with 200-nm thickness is close to that of bulk silicon. However, when we do not consider the undercut ΔL, the obtained Young's modulus is decreased 39.3%. Based on the linear force-displacement response of 12μm long and 200nm thick silicon nanocantilever obtained by using AFM, our extracted Young’s modulus of the [110] nanocantilever with and without undercut is 169.1GPa and 133.0GPa, respectively. This error reaches 21.3%. Our work reveals that the effect of the undercut on the characterization of the mechanical properties of nanocantilevers with dynamic and static test must be carefully considered.

Design Development of Lightweight Disc Brake for Regenerative Braking – Finite Element Analysis

The automotive industry has for many years identified weight reduction as a way of improving product competitiveness and thus the ability to make profits. One area that has been examined for weight reduction is vehicle with regenerative braking system (RBS). The greatest advantages of electric vehicles (EVs), and hybrid electric vehicles (HEVs) is their ability to recover significant amounts of braking energy using a RBS. Regenerative braking is an effective method to extend brake disc life, minimise disc rotor weight, minimise brake pad wear and to extend the working range of an EV or HEV. Regenerative braking would extend the working range of an EV or HEV provided that any extra energy consumption e.g. from increased vehicle mass and system losses did not outweigh the saving from energy recuperation, also reduce duty levels on the brakes themselves, giving advantages including extended brake rotor and friction material life, but more importantly reduced brake mass, minimise brake pad wear. The objective of this research is to define thermal performance on lightweight disc brake models. Thermal performance was a key factor which was studied using the 3D model in Finite Element Analysis simulations. Ultimately a design method for lightweight brakes suitable for use on any car-sized hybrid vehicle was used from previous analysis. The design requirement, including reducing the thickness, would affect the temperature distribution and increase stress at the critical area. Based on the relationship obtained between rotor weight, thickness, undercut effect and offset between hat and friction ring, criteria have been established for designing lightweight brake discs in a vehicle with regenerative braking.

An Evaluation of Dimensional Accuracy of One-Step and Two-Step Impression Technique Using Addition Silicone Impression Material: An In Vitro Study

The study is aimed to evaluate the dimensional accuracy, the effect of undercut of two different configurations and the elastic recovery of addition silicone impression material assessed indirectly, by measuring the dimensions on stone models recorded from the impression of the master model, using one-step and two-step impression technique, for addition silicone impression materials. Measurements are taken to evaluate horizontal or linear and vertical dimensional changes, of the abutment V and abutment C from the stainless steel model. Heavy body/light body material is used for making one-step impression technique in a custom tray. Putty/light body is used for taking two-step technique in a stock metal tray. Improved die stone is used for pouring the impression. The different 11 locations on the dies produced by two different techniques are measured microscopically on image analyzer and compared with those of stainless steel model. Anova test was applied to test the differences of mean values of inter and intra abutment measurements, to calculate p value. Unpaired t test was applied to calculate t value. Results showed less deviation of stone models produced by one-step technique from stainless steel model, whereas the deviation of stone models produced by two-step is comparatively more. (p<0.01). This difference of deviation is significantly less in one-step as compared to two-step technique. One-step is sufficiently dimensionally accurate than two-step technique in conjunction with addition silicone impression material. They have the best elastic recovery from the two undercut configurations.

Analysis of resonance frequency and pull-in voltages of curled micro-bimorph cantilevers

A systematic study is presented on the modelling, fabrication and measurements of curled micro-bimorph cantilevers, which are composed of a dielectric beam with a metal electrode layer coated on top. The device, having stress-induced upward curvature in the electrical off-state, functions as a vertical electrostatic actuator for nanometre displacements. A detailed analysis is carried out of the resonance frequency of the cantilever as a function of its length, deflection and thickness of the upper electrode layer, including the effect of undercut. A Galerkin-based static model is used to predict the pull-in voltages which are validated by measurements. A dynamic model is used to investigate the shift in resonance frequency by the electrostatic spring softening effect, which is evaluated against experimental data. The measured shift in resonance frequency is further extrapolated to non-destructively predict the pull-in voltages.

Geometry effect assesment on mechanical performance of forge welded pipe

Shielded Active Gas Forge Welding is a robust and efficient solid state welding method applicable to offshore and oilfield applications. The mechanical or fracture performance of the welded connection may be influenced by the forge weld shape. In this paper the main focus is on the geometry effect of weld shape and defects on forge weld mechanical performance and fracture behavior. The potential impact of variables on the undercut description is parametrically analyzed by finite element calculation. As for the undercut located in the transition region between weld and base material, our studies show that the outer undercut of more than 0.3 mm has a significant impact on mechanical behaviour of welded pipe. When the undercut is located in the fusion plane, its impact on mechanical performance of welded pipe is negligible. Weld caps are beneficial since they contribute to weakening the driving forces for crack propagation. Even if the effect of undercut is considered, the beneficial contribution of weld cap still exists.

Effect of undercut on the resonant behaviour of silicon nitride cantilevers

We present a systematic investigation of the dynamic properties of silicon nitride cantilevers in air. The thermal noise spectra of cantilevers have been measured using a home-made optical deflection setup. Torsional and flexural resonances up to the seventh mode are observed. The dependence of resonance frequencies on the dimensions and mode number is studied in detail. It is found that undercut increases the effective length of the cantilever by a value ΔL, which depends on the undercut distance and the resonance mode shape, but not on the cantilever length. Finite element modelling confirms these experimental findings. A simple model is suggested for the shape of the undercut region, which agrees well with experimental findings. Using this model, the undercut cantilever can be approximated by a stepped beam, where the clamp distance depends on the underetch duration and the mode shape.

Automated design of thin-walled packaging structures

This paper presents an automated method to generate thin-walled packaging structures with reinforcement. This method first obtains a thin-walled design space compose of hexahedral elements, which covers the models to be packaged without undercut effect. After the proper boundary conditions are assigned by designers, topology optimization is applied to identify the optimal placement of reinforcement. This automated method can also be used to generate foam packaging structures. Design examples are presented to demonstrate the efficiency of this method.

Laser direct write patterning technique of indium tin oxide film

The circuit patterns of transparent conductive oxide films (TCO films) have widely formed using the traditional photolithography method. The indium tin oxide (ITO) films of flat panel displays are one of the TCO films and usually ablated using the wet etching, which is widely adopted in the semiconductor processing. However, the chemical wet etching techniques usually appear with more disadvantages in the procedure, including the chemical pollution, the under-cut effect, the swelling and the costly. Therefore, the dry etching would be replaced the photolithography procedures. The laser directing method is one of the dry etching techniques and could form the circuit pattern on the ITO glasses. Moreover, the laser directing techniques could flexibility make the circuit pattern in the TCO film and the substrate would be not eroded by the laser ablation. The investigation is interested in circuit patterning of glass substrate using the laser direct writing techniques to ablate the ITO films by a UV laser materials processing system. The UV laser is a third-harmonic Nd: YAG laser with a 355 nm of wavelength and the power is 1.0 W. In this paper, the ITO films are ablated by the UV laser materials processing system which used the different repetition rate and the feeding speeds of tables. The results of laser pattering of ITO films are measured using the optical microscope (OM) and the scanning electron microscope (SEM), and it indicates the repetition rate of laser would affect the width of line.

Electrical properties of shallow p+-n junction using boron-doped Si1−xGex layer deposited by ultrahigh vacuum chemical molecular epitaxy

Strained boron-doped Si1−xGex layers with different Ge mole fractions were selectively deposited by ultrahigh vacuum chemical molecular epitaxy to form shallow p+-n junction suitable for raised source/drain metal–oxide–semiconductor field effect transistor applications. Detailed electrical characterizations were performed. Our results show that the reverse leakage current could be optimized by a rapid thermal annealing at 950 °C for 20 s, and a near perfect forward ideality factor (i.e., &amp;lt;1.01) is obtained for the p+-n Si1−xGex/Si junction. By analyzing the periphery and area leakage current components of p+-n Si1−xGex/Si junctions with various perimeter lengths and areas, the degree of misfit dislocations and undercut effect were studied. The specific contact resistance was found to decrease as Ge mole fraction increases. Junction depth measurements also show that the junction depth decreases monotonically with increasing Ge mole fraction. The reduced B diffusion constant is attributed to the increasing Ge gradient in the transition region.

Profiled cylindrical roller design in consideration of grinding undercut effect

In this paper, the effect of the grinding undercut of the raceways on the longitudinal pressure distribution of the profiled rollers, which are the most popular axial profile employed by the bearing manufacturers, was discussed. Based on the profiled roller geometrical equations and numerical calculation of three-dimensional elastic contact problems of finite length, a new numerical method for calculating the crown drop evaluation considering the effect of grinding undercut was used. The analyses of two structure case, that roller length is greater or less than raceway width, were carried out and compared with each other. The Results show that the width of grinding undercut must be considered in determining the crown drop of rollers.

The effect of undercut and residual stresses on fatigue behaviour of misaligned butt joints

A numerical model is developed to predict the combined effect of a weld toe undercut, residual stresses and misalignment on the fatigue strength and fatigue life of butt welded joints subjected to pulsating tensile loading. Linear Elastic Fracture Mechanics (LEFM), Finite Element Analysis (FEA) and superposition approaches have been used for the modelling. It has been found that the effect of undercut is the most significant geometrical effect affecting the fatigue behaviour of butt welded joints and is governed by the effect of other weld geometry parameters. The reduction of fatigue life and fatigue strength, in comparison to flush-ground welded plate, caused by an introduction of weld toe undercut is twice that due to welded joint without undercut. It means that by elimination of undercut, fatigue strength can be improved up to 50% of the level that can be obtained by flush-ground welded plate. It is also found that a presence of misalignment of 5% of plate thickness and undercut of 2% of plate thickness are fairly representative for the lower boundary of S- N curves of butt joints in a real situation. Fatigue life can be decreased by up to 10 and 100 times compared to perfect stress-relieved conditions of aligned and misaligned joints, respectively, once high tensile residual stresses of yield stress magnitude are present. As a result, the slope of S- N is no longer constant and the effect of misalignment is more significant than that of undercut. However, when the magnitude of tensile residual stress becomes smaller or it changes into compressive stresses the effect of undercut will play a dominant role in comparison with that of misalignment. The effect of misalignment may be beneficial for high cycle fatigue life of the order of greater than 2 × 10 5 cycles, especially when compressive residual stresses are introduced into the weld toe surface by using surface treatment (i.e. shot peening, hammering). In this case, the improvement of fatigue strength of misaligned joints and undercut-free joints can be 50% more effective than that of aligned undercut joints.

溶接継手の疲労強度に及ぼすアンダカットと停留き裂の深さの影響

溶接継手の疲労強度に及ぼすアンダカットと停留き裂の深さの影響