Effect Of Contact Stress Research Articles

Effect of contact stress and slip amplitude on fretting fatigue behaviour of ultrasonic surface nanocrystallized TC11 titanium alloy

In this paper, combined experimental and numerical methods are applied to investigate the effect of different contact stress and slip amplitude on the fretting fatigue (FF) behaviour of TC11 titanium alloy with gradient nanostructure introduced by ultrasonic surface rolling process (USRP). The properties of gradient nanostructure are characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray residual stress tester, microhardness tester. As evidenced by the FF experimental results, USRP can significantly improve the FF life of TC11 by introducing large compressive residual stress and work hardening layer. The dominant parameters in improving the FF resistance under different loading conditions are investigated. In addition, the simulated results from Abaqus show that contact stress plays a more important role in influencing FF life compared to fretting bridge span, which is attributed to the change in slip amplitude and stress concentration. Fretting fatigue life initially increases and then decreases with contact stress and there is a contact stress threshold that leads to minimum lifetime. This threshold of USRP specimens is greater than that of untreated specimens. The transition of fretting mode along with contact stress is observed and discussed.

Cell Performance Prediction of the Particle Structure of All-Solid-State Batteries By Numerical Simulation and Machine Learning

All-Solid-State Battery (ASSB) is expected to be commercialized for electric vehicle applications. However, the correlation between the electrode structure and the cell performance is unknown, and no design theory has been established. Especially the effect of contact stress on solid-solid interface is important. And the ununiform reaction area cause the exsess current concentration. In our previous study, we developed various simulation model to understand the effect of heterogeneous structure and the effect of volume expansion on dynamic structure change during charging-discharging cycle from the viewpoint of durability. In this study, we developed new simulation model with stress calculation and electrochemical reaction, Moreover, the simulation results were used to create training dataset for machine learning. By using these approaches, we tried to develop new method to predict cell performance from composite electrode structure to cell performance.The stress estimation was performed using the discrete element method (DEM) [1]. The various material parameters are used such as, particle diameter (average and standard deviation), Young's modulus, Poisson's ratio and density. The distribution of the stresses on each particle was calculated from the DEM calculation results and confirmed to be approximately Gaussian.To simulate electrochemical reaction and mass transport in electrode layer, we used multi-network model (MNM)[6]. The schematic image of this model is shown in Fig.1, we used various network grid of active material network, solid electrolyte network and interface network. Basic equations of Li concentration, Li potential and electron potential were calculated in these networks. In this study, with DEM and MNM, we developed new simulation model shown in Fig.2.A convolutional neural network (CNN) [7] was used as the model for machine learning, and various structural parameters, including the DOD, cell potential, and stress on each particle calculated by DEM, were identified to create a dataset. 250 images were used for training, 150 of which were used for training, 50 for validation, and 50 for testing. The coefficient of determination (R²) of the standard deviation of DOD and potential is almost 0.7 in each condition, and the cell performance can be predicted by the machine learning model. The contact area of the electrochemical reaction interface, AM-SE, was calculated from the stress on the contact surface calculated by DEM and Hertzian contact theory [8]. Thus, we can express the relationship between interface mechanical stress on solid-solid and effective reaction, and this effect can be predicted with various structure of composite electrode layer by using machine learning. It was possible to predict the cell performance and effective contact area in the electrode layer of the all-solid-state battery.Acknowledgement:This research was carried out under the project (Grant Number JPMJMI21G4) supported by the JST-Mirai Program, Japan.

A Modeling Framework of Electrochemo-mechanics of Lithium-ion Battery: Part II. Porous Electrodes with Contact Stress Effect

Extended from the electrochemo-mechanical single particle model, an electrochemo-mechanical impedance model for porous electrode in LIB, which consider the effect of the contact stress, is proposed in this work. A modified coefficient which links the mechanical properties of the electrode and particle material is introduced to describe the effect of contact stress. Firstly, we find that the contact stress can weaken the stress-induced semicircle in the low frequency range through analyzing the Faradaic part of the impedance. Secondly, considering the contact stress is determined by the mechanical bonding between electrode layer and the current collector, we introduce a pseudo-elastic boundary condition to analyze the bonding effect. For rigid substrate, namely the in-plane deformation is totally restricted, the effect of the contact stress is strong. For free substrate, namely the in-plane deformation is not restricted, the contact stress is not induced thus its effect on impedance disappears. Lastly, we discuss the interaction effect of stress and the ionic transport in the electrolyte and find that the interaction is strong for silicon-based material, which indicates the stress effect needs to be considered when interpreting the impedance data in this case.

Effects of contact stress on patellarfemoral joint and quadriceps force in fixed and mobile-bearing medial unicompartmental knee arthroplasty

BackgroundUnicompartmental knee arthroplasty (UKA) is an effective treatment for end-stage, symptomatic unicompartmental osteoarthritis of the knee joint. However, patellofemoral joint degeneration is a contraindication to medial UKA. Therefore, the objective of this study was to evaluate the biomechanical effect of medial UKA using fixed-bearing (FB) and mobile-bearing (MB) design prostheses on the patellofemoral joint.MethodsA three-dimensional finite-element model of a normal knee joint was developed using medical image data. We performed statistical analysis for each model. The differences in contact stress on the patellofemoral joint and the quadriceps force between the FB and MB designs were evaluated under a deep-knee-bend condition.ResultsAt an early flexion angle, the results of contact stress showed no significant difference between the FB and MB medial UKA models compared with the intact model. However, at high flexion angles, we observed a significant increase in contact stress with the FB models compared with the intact model. On the contrary, in the case of the MB models, we found no statistically significant increment compared with the intact model. A larger quadriceps force was needed to produce an identical flexion angle for both the FB and MB UKA designs than for the intact model. At high flexion angles, a significant increase quadriceps force whit the FB model compared with the intact model.ConclusionsOur results indicate that with medial UKA, the contact stress increased and greater quadriceps force was applied to the patellofemoral joint. However, performing UKA on a patellofemoral joint with osteoarthritis should not be difficult, unless anterior knee pain is present, because the increase in contact stress is negligible.

Effect of contact stress on fretting fatigue behaviour of 35CrMoA steel under multiaxial nonproportional paths

AbstractFretting fatigue often occurs in contact couples subjected to both bulk oscillatory loads and normal loads, which accelerates the initiation and propagation of fatigue cracks. This study explores the multiaxial fretting fatigue behaviour of 35CrMoA steel with different contact stresses under diamond and square loading paths by experimental methods. From experimental results, the fracture mechanisms with the increase of contact stress have been summarized by combining the analysis of macrorupture and microrupture surface. The strain response behaviour, characteristics of fretting region and crack propagation direction are also analysed and concluded considering the influence of loading path and contact stress in this paper, which have been rarely mentioned in the previous literature. In addition, debris composition of stick and slip regions is investigated as well.

Effect of contact stress on the tribology behaviors of PTFE/316L seal pairs under various abrasive-contained conditions

This study focuses on the tribological characteristics of polytetrafluoroethylene rubbing against 316L stainless steel in the presence of various Al2O3 abrasive particles. The ranges of the contact stresses and abrasive sizes were 2.50–5.01 MPa and 2.0–230 µm, respectively. The evolution of the coefficient of friction, abrasive invasion behavior and damage characteristics on worn surfaces, and the transformation of damage mechanisms under different contact stresses are summarized. Results demonstrate that contact stress exerts a considerable effect on abrasive invasion behavior, the coefficient of friction trends become complicated at low contact stress. With decreasing particle sizes under a contact stress of 2.50 MPa, the wear failure changes from two-body wear to three-body wear, or two wear behaviors exist simultaneously. As contact stress increases, the wear mechanism is gradually simplified. The particle size threshold that causes the change of the wear mechanism is also gradually reduced. The wear rate of polytetrafluoroethylene has no linear relationship with abrasive size, whereas wear increases with contact stress. Under 2.50 MPa conditions, the particles easily invade the tribo-interface in the friction process, thus increasing the wear rate of the metallic counterpart. In addition, with increases contact stress, the polytetrafluoroethylene material transfers to the counterface, and local adhesion occurs. When the contact stress is increased to 5.01 MPa, polytetrafluoroethylene even shows an obvious creep.

Effects of contact-stress on wear behavior of zirconia-reinforced lithium silicate glass-ceramic

Background: The purpose of the present study was to investigate effects of contact-stress on direct-contact wear behavior of zirconia reinforced lithium silicate glass-ceramic; in vitro off-axis sliding contact chewing simulation. Methods: In this study, 12 mm diameter X 2 mm thickness in size of lithium disilicate, Vita Suprinity; zirconia-reinforced lithium silicate was used. The test specimens were subjected to 100.000 mechanical loading, 3000 thermal cycles, 1.2 Hz wear frequency, 30° angle 0.7 mm lower jaw movement and different size Al2O3 antagonist material in artificial saliva. The average wear volume loss of the test specimens was obtained after wear test procedure using non-contact 3D profilometer. Furthermore, micro-structure analyzes of the wear surfaces of the test specimens were performed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Results: As a result of this study, ceramic material showed better abrasion resistance with increasing contact surface of abrasive material. Conclusion: However, microstructure analysis has shown that micro cracks occur on the wear surfaces both wear test procedures. These micro cracks may have occurred under the wear surface of the ceramic material.

Wear Characteristics on the can Opener of SUS 420J2

Tinplate containers with high strength, good formability and corrosion resistance, has been widely used in food, beverages, grease, chemicals and other applications. In recent years, because of the significantly progress of tinplate container manufacturing technology, many tinplate cans have been opened in easy-open rings. However, a large number of food cans still use can openers as an important tool for opening cans. At present, in addition to the general traditional can opener is a single-edged knife in a lever manner, the other like roller, serrated or electric are driven by a gear wheel to rotate around the can to achieve the purpose of opening the can. Moreover, the wheel materials mainly are made from the stainless steels. To investigate wear characteristics on the can opener of the stainless steel of SUS 420J2, the experiments were conducted by the self-developed friction tester and its measure system in this study. According to the results, the effects of contact stress and sliding speeds on the wear of cutlery of the openers can be clarified.

The effect of contact stress on the sliding wear behaviour of Zn-Ni electrodeposited coatings

Electrodeposited zinc-nickel coatings, developed in the 1980's as a replacement for zinc coatings in the automotive industry, have recently gained interest in the aerospace industry to replace cadmium coatings. Due to different material properties of Zn-Ni and Cd, there is a need to characterize Zn-Ni for tribological applications. Sliding wear tests are performed on a reciprocating pin-on-flat tribometer using a steel counterface on two electrodeposited Zn-Ni coatings with different microstructure and surface topography. Tests were performed under 3, 7.5 and 12N normal loads at a relative humidity of 60% for 2000 cycles. Increasing the normal load increased the steady state friction coefficient and wear for both coatings. The smooth and dense coating was more sensitive to the change in normal load than the rough and porous coating, as the latter experienced less wear due to the columnar structure of the coating. In contrast, the smoother and dense coating, although has less wear at low loads, has more wear at high loads due to debonding of the coating. The coating morphology affected the extent of wear due to different wear and velocity accommodation mechanisms.

A Study of the Tribological Behavior of TiAl-10 wt.%Ag Composite Based on the Contact Stress Evolution

The contact stresses of materials in moving mechanical assemblies are rather important for minimizing friction and decreasing machinery energy dissipation. In this study, the effect of contact stresses on the friction and wear behaviors of TiAl-10 wt.%Ag was studied at 0-240 min using the united methods of experiment research, numerical simulation and theoretical analysis. The results showed that the high contact stresses led to the plastic deformation of TiAl-10 wt.%Ag at 0-50 min. The friction coefficients and wear rates decreased rapidly with the lowering of contact stresses from 1034.28 to 710.52 MPa. At elastic deformation stage (50-240 min), the forming of lubricating film was beneficial to the decrease in friction coefficients and wear rates at 50-150 min, whereas the lower contact stresses caused the increasing of friction coefficients and wear rates. The competition between film lubrication and contact stresses caused the lowering of friction coefficients and wear rates at 50-150 min. At 150-240 min, the lubricating film maintained the equivalent lubricating behaviors, whereas the lowering of contact stresses led to the slight improving of friction coefficients and wear rates. This study was meaningful for optimizing applied loads to realize the excellent contact stress state and tribological behavior of mechanical parts.

DECREASING OF MOVABLE MASSES IN VALVE TIMING USING ROLLER TAPPET

The method for reduction of valve timing movable masses, by the use of composite cams for camshaft, which mate with roller tappet, is presented. It has been carried out an analysis of stresses under the surface of the cam using the methodology and computer programs allowing the synthesis and analysis of the cam mechanism, and to estimate the fatigue life, as well as using the finite element method. Mating roller tappets with a light camshaft, forged from TiAl alloy, can be done if the camshaft has steel caps set under the pressure on the surfaces their cams. The problem, however, is the formation of high stress in the Bielaiev point, when a roller tappet mates with segment cam. Because of the certainty for the cap fixing, it is assumed that the depth for the Bielaiev point should not exceed half the thickness of the cap. The stress analysis shows, that exceeding of the material yield strength is controlled by the interference value between the cam and its cap and by the apex radius of the cam. Effect of contact stress is at least an order of magnitude smaller. The maximum depth of the Bielaiev point does not exceed 0.09 mm, which is about half the thickness of the proposed cap. There is a need not for too small radii between the cam and the apical cap. Optimal selection of proper geometry of the cam will be easier after a proper modification of the program used for the synthesis and analysis of the cam mechanism, such that it is possible to ask any operational surface of the cam profile.

Effect of contact stresses on shape recovery of NiTiCu thin films

Permanent plastic deformation induced by mechanical contacts affects the shape recovery of shape memory alloys. To understand the shape recovery of NiTiCu thin films subjected to local contact stresses, systematic investigations are carried out by inducing varying levels of contact stresses using nanoindentation. The resulting indents are located precisely for imaging using a predetermined array consisting of different sized indents. Morphology and topography of these indents before and after shape recovery are characterized using Scanning Electron Microscope and Atomic Force Microscope quantitatively. Shape recovery is found to be dependent on the contact stresses at the low loads while the recovery ratio remains constant at 0.13 for higher loads. Shape recovery is found to occur mainly in depth direction of the indent, while far field residual stresses play very little role in the recovery.

Lean Manufacturing of Pressure Valve Plate

Manufacturing of Pressure Valve Plate is considered as complex process that demands the knowledge of different areas, such as geometry, tolerances, dimensions, manufacturing procedures and manufacturing processes. Lean manufacturing avoids both setup time and setup cost of in manufacturing. Milling fixtures must be sturdy, with relatively large locating and supporting areas and strong clamp. Work piece deformation is unavoidable due to its elastic/plastic nature, and the external forces impacted by the clamping actuation and machining operations. Deformation has to be limited to an acceptable magnitude in order to achieve the tolerance specifications. Accuracy of components like pressure valve plate is extremely essential. The analysis is carried out on fixture and pressure valve plate assembly. Pressure Valve plate fits on to hydraulic pump which is used to drive the engine load of defence vehicle. To study the fixture analysis and contact stress effect, fixture and valve plate are modelled and assembled for the analysis to be carried out.

An Experimental Study for the Effect of Contact Stress of Blank Holder and Punch Velocity on Crack Ratio of Fine-Blanked Surface

In this study, the parameters (i.e., contact stress at the die-sheet interface and the punch velocity) were measured by the installation of film stress sensors in the fine-blanking die. A regression model was established to investigate the degree of importance of the parameters and their interaction on reducing the crack ratio of fine-blanked surface. Analysis of variance (ANOVA) was then performed to check the adequacy of the regression model. The optimal results of the regression model agreed well with the experimental result. The regression analysis indicated that the contact stress have a major influence, followed by the interaction and the punch velocity. The importance of the interaction means that the ability of contact stress in crack ratio reduction depends on the level of punch velocity. The result could be useful to facilitate an improvement in the quality of the fine-blanked parts by the optimization parameters.

Optimization of New 25A-size Metal Gasket Design Based on Contact Width Considering Forming and Contact Stress Effect

Optimization of New 25A-size Metal Gasket Design Based on Contact Width Considering Forming and Contact Stress Effect

Transmission of vertical stress in a real soil profile. Part I: Site description, evaluation of the Söhne model, and the effect of topsoil tillage

Transmission of stresses in the soil profile is one crucial ingredient of the ‘chain of cause and effect’ leading to either persistent deformation or elastic deformation. This study is the first of a series of three, where effects of contact stress and soil conditions on the stress distribution in the soil profile were evaluated. Measurements of vertical stresses were performed in an undisturbed Stagnic luvisol in three dimensions during one pass of one wheel (in depth, across and along the driving direction). In the present study, we tested the effect of loosening the topsoil by ∼20 cm ploughing on the stress distribution in the soil profile. The reference soil had not been ploughed or otherwise tilled for 18 months. The distribution of vertical stress near the tyre–soil interface was fitted by a model combining a power function and an exponential function for the stresses, respectively, along and across the driving direction (FRIDA model). The tillage-induced reduction in topsoil strength lead to more even stress distribution at the tyre–soil interface but did not significantly affect the measured vertical stresses at 0.3, 0.6 and 0.9 m depth. The vertical stresses at 0.3 m depth were equivalent to the peak stresses measured in the contact area between tyre and soil (approx. 200 kPa) and appeared more scattered when the top 0.2 m had been recently ploughed. Taking the FRIDA-estimated vertical stresses in the tyre–soil interface as input to the analytical Söhne model, vertical stresses in the subsoil were underestimated for both treatments. The precompression stress of the topsoil for this arable soil was much lower than the subsoil even for the treatment not tilled for 18 months. Hence, the vertical heterogeneity of soil for both treatments did not obey the model assumptions of isotropic soil properties. However, the model performed well from 0.3 to 0.9 m depth. Hence, an alternative to the model of Söhne is needed for the calculation of stress transmission in the frequently tilled topsoil of arable soils from the tyre–soil interface.

Orientation effects of micro-grooves on sliding surfaces

Based on a brief review of the researches related to the patterns of micro-grooves for tribological purpose, experiments were designed and carried out to study the orientation effects of grooves on the friction performance. The experimental data indicated that the grooves perpendicular or parallel to the sliding direction have a strong impact on the friction performance of sliding surfaces, and the merits of perpendicular or parallel orientation may swap under different contact conditions. The results were then discussed from the aspects of hydrodynamic effect, lubricant supply effect and contact stress effect.

The effect of contact stress on cartilage friction, deformation and wear

Following hip hemiarthroplasty, a metal femoral head articulates against natural acetabular cartilage. Cartilage friction and wear may be influenced by variables including loading time, contact stress, contact area, sliding distance, and sliding speed. The aim of this study was to investigate the effect of these variables on cartilage friction, deformation and wear in a simulation using idealized geometry model. Bovine cartilage pins were reciprocated against metal plates to mimic a hemiarthroplasty articulation under static loading. The effective coefficient of friction (micro elf) under contact stresses (0.5 to 16 MPa), contact areas (12 and 64 mm2), stroke lengths (4 and 8 mm), sliding velocities (4 and 8 mm/s), and loading time (1 and 24 hours) were studied. The permanent deformation of cartilage (after 24 hours of recovery) with and without motion was recorded to assess cartilage linear wear. The micro eff was found to remain < 0.35 with contact stresses < or =4 MPa. Severe damage to the cartilage occurred at contact stresses > 8 MPa and significantly increased micro eff after 12 hours of reciprocation. In long-term, contact area had no significant effect on micro eff, and sliding distance and velocity only affected micro eff under low contact stresses. The cartilage linear wear increased with contact stress, sliding distance and velocity.

A surface crack in a graded coating subjected to sliding frictional contact

This article presents an analytical method developed to conduct fracture analysis of functionally graded coatings that are under the effect of contact stresses. The geometric model considered comprises a functionally graded coating, which possesses a surface crack and is perfectly bonded to a homogeneous half-plane. A two-step solution procedure is put forward in which the contact and crack problems are treated separately. First, the graded coating is assumed to be in sliding frictional contact with a rigid flat punch and the contact stresses are computed. These stresses are then used as inputs for the crack problem and the mode I and II stress intensity factors are evaluated. Governing partial differential equations for the contact and crack problems are derived by using the theory of plane elasticity and solved by utilizing Fourier transformation techniques. The derivations lead to a single singular integral equation in the case of the contact problem, and two uncoupled singular integral equations in the case of the crack problem. An expansion–collocation approach is adopted for the numerical solutions of the integral equations. Comparisons of the results generated for the contact and crack problems to those available in the literature demonstrate the high levels of accuracy attained by the proposed solution techniques. Further numerical results are presented so as to illustrate the influences of material nonhomogeneity and coefficient of friction on the contact stresses and the mode I and II stress intensity factors.

Residual stress profiles for mitigating fretting fatigue in gas turbine engine disks

The driving force for fretting fatigue in engine disks is the contact stresses generated by fretting of the blade and the disk surfaces in the attachment region. This paper examines the use of different residual compressive stress profiles to counteract the undesirable effects of contact stresses and to mitigate fretting fatigue. A global finite-element analysis of the disk blade assembly is first performed. The contact pressure and shear traction at the attachment region are extracted from the FEM results and used to compute the contact stress distribution. The contact stresses are then combined with the residual stresses and the bulk stresses. The overall stress distribution is then utilized in a probabilistic crack growth model to predict the risk of disk failure for a military engine under simulated loading conditions. The results are used to identify the minimum residual stress profile for mitigating fretting fatigue in engine disks.