Shape Of Contact Area Research Articles

Theoretical Analysis of Rolling Force during Cold Rolling with Roll Crossing and Shifting System

A precise prediction of the rolling force is critical to ensure the quality of the final product, especially in the cold rolling of thin strips. Based on this, a new mathematical model is developed to work out the rolling force when considering the roll crossing angle and work roll shifting values at speed ratios of 1.1, 1.2 and 1.3. An iterative method was used to indicate the contact area shape, from which the rolling force was automatically calculated using the Matlab™ code for the cases of work roll cross angles of 0.5° and 1°. Experimental measurements and analysis were carried out to validate the theoretical calculations. The result shows that the theoretical analysis and experimental results are in good agreement, which indicates that the developed theoretical model can predict the rolling force well with a consideration of roll crossing during the cold rolling process.

High flex femoral component with slanted pegs improves fixation strength of total knee arthroplasty

High incidences of early aseptic loosening cases have led to numerous analyses on fixation strength of femoral component (FC). This study consists of two objectives: (1) to analyze the correlation between articulating contact area shape conformities and fixation strength, and (2) to analyze the relationship between slanting box patterns of the FC and fixation strength. Two design analyses were constructed: first, using three different types of contact congruence with radius ratios of 0.50, 0.89 and flat. Second, box patterns of the FC were anteriorly slanted at 2, 4 and 6°. The fixation strength of the FC is significantly improved (38.59%) by slanting the box pattern anteriorly as compared to the non-slanted FC design.

Empirical joint contact mechanics: A comprehensive review.

Empirical joint contact mechanics measurement (EJCM; e.g. contact area or force, surface velocities) enables critical investigations of the relationship between changing joint mechanics and the impact on surface-to-surface interactions. In orthopedic biomechanics, understanding the changes to cartilage contact mechanics following joint pathology or aging is critical due to its suggested role in the increased risk of osteoarthritis (OA), which might be due to changed kinematics and kinetics that alter the contact patterns within a joint. This article reviews and discusses EJCM approaches that have been applied to articulating joints such that readers across different disciplines will be informed of the various measurement and analysis techniques used in this field. The approaches reviewed include classical measurement approaches (radiographic and sectioning, dye staining, casting, surface proximity, and pressure measurement), stereophotogrammetry/motion analysis, computed tomography (CT), magnetic resonance imaging (MRI), and high-speed videoradiography. Perspectives on approaches to advance this field of EJCM are provided, including the value of considering relative velocity in joints, tractional stress, quantification of joint contact area shape, consideration of normalization techniques, net response (superposition) of multiple input variables, and establishing linkages to regional cartilage health status. EJCM measures continue to provide insights to advance our understanding of cartilage health and degeneration and provide avenues to assess the efficacy and guide future directions of developing interventions (e.g. surgical, biological, rehabilitative) to optimize joint's health and function long term.

Comprehensive modeling of forming forces in three directions for incremental sheet forming process based on the contact area

Incremental sheet forming (ISF) is a promising sheet forming process for small batch production of complex 3D workpieces without time consuming set-up operation. However, the understanding of comprehensive effect of the contact area and stress on forming force is still insufficient, which is critical to the feedback control, process optimization and professional machine design, etc. Therefore, the present work aims to provide efficient mechanism-based prediction models for both the contact area, stress and the forming force. First, a universal predicted shape of the contact area between the forming tool and sheet in the ISF process was deduced and modeled based on typical experimental phenomena. In particular, the influence of parameters on the shape of contact area was clarified by defining contact angles β, α and α1. Then, stress components of the material within the contact area were derived after the theoretical analysis by adopting the cylindrical coordinate. In addition, an efficient forming force prediction model for ISF especially in three directions was established and verified, which combined the contact area model and calculated stress components. Finally, it is proved that sheet thickness has the most significant positive effect on forming force in three directions, since the rise of thickness not only increases the size for contact area but also leads to a large growth of equivalent thickness coefficient. Meanwhile, tool diameter has limited effect on forming fore, although it has the largest effect on the size of contact area. This study provides the fundamental understanding of the dynamic interrelation between contact area, stress-strain states and forming forces, which promotes the industrial transformation of ISF.

Contact analysis and performance evaluation of ring type traveling wave ultrasonic motors based on a surface contact model

A surface contact model of ring type traveling wave ultrasonic motors is proposed in this paper in order to describe the circular three-dimensional contact and friction problem between the stator and rotor accurately. Differing from previous contact models of traveling wave ultrasonic motors, the flexibility of the rotor, which results in the irregular shape of contact area and inhomogeneous distribution of contact pressure along radial direction, is taken into account in the proposed model. The normal contact between the stator and rotor is analyzed with finite element method and the tangential force transmission on the contact surface is investigated with analytical method. The contact pressures and the tangential stresses on the contact surface are obtained. Mechanical performances of the motor are also studied based upon the proposed model. Finally, torque-speed curves of a prototype motor are measured and compared with the calculated results of the proposed model, and good agreements are obtained. In addition, the proposed surface contact model is compared with previous line contact models. It is found that the calculated results of the surface contact model are closer to measured results than those of line contact models. The comparison results verify the accuracy of the proposed surface contact model.

Effects of rocking direction on load and forged geometry in cylinder upsetting

In this study, we demonstrate the reduction of forging loads using a rocking motion forging process with four linear actuators. We investigate the effects of the rocking direction on the upsetting load and shape through experiments using aluminum cylinders. The load reduction ratio is not significantly affected by the rocking direction under identical rocking conditions. The oval shape of the transverse cross section that was observed in the case of one-direction rocking changed into a near circular shape when two-direction rocking motion was applied. A positive correlation was confirmed between the load and the contact area reduction ratios, regardless of the rocking direction, even though the shape of contact area was different.

A Novel Axial Modification and Simulation Analysis of Involute Spur Gear

The transmission of spur gear mechanism may generate uneven load distribution because of machining error, assembly error, elastic deformation, and other factors, resulting in serious damage to the bearing capacity and service life of gears. To improve the contact condition of gear pairs and enhance the meshing performance and bearing capacity, this study proposed a novel axial modification method based on a composite modification curve with indefinite parameters and an evaluation method to evaluate modification effects. In addition to the surface equation of modified tooth was derived according to the composite modification curve, and the finite element model was built for gear pair. After conducting simulation analysis for the meshing process, the location and the shape of contact area as well as the other results can be acquired. In addition, the modification parameters can be optimized by performing orthogonal experiments for modified gear pairs; thus, the ideal modification effect is obtained at a specific operating condition. Moreover, comparison analysis was performed, and the results show that the phenomenon of uneven load distribution is dramatically improved when the gear pair was modified with optimized parameters, and the bearing capacity of the gear pair was increased. Finally, using the optimized parameters to trial-produce gears and conducting running-in tests, the effectiveness and the practicability of the method proposed in this study were verified.

Development of a machine vision system for determination of mechanical properties of onions

In this research, a machine vision system was developed to measure the contact area and dimensions of agricultural samples in mechanical properties testing. Two probes were made of aluminum and round glass panes. The Universal Testing Machine was equipped with these probes. One camera was positioned inside the probe to monitor the contact area between probe and samples. Other camera was located outside of probe to measure dimension of samples during the test. Onions were selected as study products and those mechanical properties were measured using this machine vision system. Also, to verify the results of this system, the mechanical properties were calculated using conventional methods. The effects of onion cultivars (red and yellow), loading direction (polar and equatorial) and loading speed (15 and 25mm/min) on the size of contact area, the stress and strain, elasticity modulus and Poisson’s ratio were examined. The results showed that there was no any statistically significant differences between conventional method and our presented method at 99% confidence level. Therefore, a machine vision system can be replaced with conventional method. It was possible to assimilate the shape of contact area to a near perfect circle. The effect of loading direction on Poisson’s ratio and the loading speed on stress and elasticity modulus were significant. Red onions under polar loading with speed 15mm/min had maximum Poisson’s ratio, stress and modulus of elasticity. The stress was obtained as 0.281±0.044MPa. The values of elasticity modulus were obtained as 2.56±1.4 and 2.77±1.8MPa for yellow and red onions, respectively. The Poisson’s ratio along x and y axis were obtained as 0.393±0.05 and 0.375±0.07, respectively. Polar loading samples were easy to deform laterally compared to equatorial loading samples. The contact area, stress and Poisson’s ratio increased with increasing deformation while the modulus of elasticity decreased.

Influence of Contact Surface Type on the Mechanical Damages of Apples Under Impact Loads

This paper presents an analysis of mechanical damage carried out on ‘Golden Delicious’ apple variety, which was subjected to impact loads during free drop against various rigid plates. For this purpose, an analysis of the contact pressure based on determined contours and surface pressure distributions at the contact point between the fruit dropped from various heights against fixed hard plates was performed. The impact test was conducted by means of Tekscan® system supported by computer verifying analysis. To obtain impact loads as well as their courses, the surface pressures and the bruise volumes were determined. Furthermore, use of ultra-thin pressure sensors allowed for determination of the characteristic shape of contact area and the impact of fruit onto rigid plate. The results showed that the impact of fruit against rigid surface (concrete, wood) generates high values of maximum surface pressure and the bruise volume, observed at dropping from 10 mm. A decrease in hardness of the test material (polyethylene foam) with decreasing maximum surface pressure approximately twice was noticed. The polyethylene foam is one of the best materials which protect fruit from mechanical damage, confirmed by the relation of bruise surface to contact surface, which did not exceed 35% during the impact at 150 mm. The results of proposed studies can contribute to developing of harvest, handling, and transport processes, aiming at reduction in losses among fruit growers and production costs, i.e., by improvement of transport method.

Tire–Pavement Contact Stress with 3D Finite-Element Model—Part 1: Semi-Steel Radial Tires on Light Vehicles

Abstract Vehicles pass their loads through tires onto pavements. Traditionally, the vertical contact pressure is assumed to uniformly distribute in a rectangle or circular area, whereas the shear contact pressure is ignored in pavement design. Experiments have demonstrated that the interaction between the tire and the pavement surface is very complicated. The contact area is not a regular shape and the distribution of contact pressure is not uniform. However, experimental approaches to measure contact pressure are usually time and energy consuming, whereas the results are subject to errors introduced by measurement sensors. On the other hand, numerical simulation can describe the interaction between tire and pavement surface under all circumstances, such as various driving conditions, different tread types, and so on. In this paper, a three-dimensional finite-element model for tires was developed. The model was validated by the static test data. Then the interactions of different tires with pavement were analyzed, including the vertical and shear contact-pressure distributions on tires and on pavement surfaces. The influences of pavement friction and load level on the contact-pressure distributions of tires and pavement were investigated as well. It was found that vertical and shear contact pressures on tires and pavement were quite different when the type of tire or the friction changed. The contact-pressure distribution was found not uniform and the shape of contact area changed as the load level varied. The complicated interactions between different tires and pavement indicate that sophisticated tire models are necessary to obtain more accurate pavement responses.

The Contact of Elastic Regular Wavy Surfaces Revisited

We revisit the classic problem of an elastic solid with a two-dimensional wavy surface squeezed against an elastic flat half-space from infinitesimal to full contact. Through extensive numerical calculations and analytic derivations, we discover previously overlooked transition regimes. These are seen in particular in the evolution with applied load of the contact area and perimeter, the mean pressure and the probability density of contact pressure. These transitions are correlated with the contact area shape, which is affected by long range elastic interactions. Our analysis has implications for general random rough surfaces, as similar local transitions occur continuously at detached areas or coalescing contact zones. We show that the probability density of null contact pressures is non-zero at full contact. This might suggest revisiting the conditions necessary for applying Persson's model at partial contacts and guide the comparisons with numerical simulations. We also address the evaluation of the contact perimeter for discrete geometries and the applicability of Westergaard's solution for three-dimensional geometries.

J0410305 繰返し球圧子押込み荷重下のセラミック被覆超合金における薄膜の強度特性評価([J041-03]工業材料の変形特性・強度およびそのモデル化 クリープ・変態・被膜強度・締結,機械材料・材料加工部門)

The purpose of this study is to clarify the possibility of the sphere indentation test to evaluate properties of crack initiation and wear progress in ceramic thin films deposited on cemented carbide. Three kinds of ceramic thin films were deposited onto cemented carbide WC-Co substrates. Cyclic sphere indentation tests were carried out by using spherical indenter to investigate the aspects of crack initiation, wear progress in ceramic film and to obtain the influence of the applied maximum load P_<max> and load ratio L_s on the cyclic number of crack initiation N_i and wear value in thin films. The main conclusions are the following. (1) The loading cycle of ring crack initiation N_i increase with increasing L_s. (2) The wear value of S=S/(d_1-d_2) linearly increase accordance with P_<max> and loading cycles N, where S is obtained by measuring the cross-sectional shape of contact area and d_1, d_2 are diameter of wear region in the contact area. (3) The values of S^^-/(P_<max>×N) is almost constant independent of L_s, P_<max> and N.

Simulation of pavement response to tire pressure and shape of contact area

This paper examines the effect of tire footprint and contact stress distribution under various combinations of tire pressures and tire loads on the pavement response through 3-D finite element stat...

Validation of an analytical model for grinding temperatures in surface grinding by cup wheel with numerical and experimental results

The thermal models of the grinding process are an important tool for predicting temperature to minimize workpiece thermal damage while improving process efficiency. According to different shapes of contact area, the analytical thermal model of arc moving heat source for rectangular workpiece is deduced and an established numerical model is chosen for comparison in this paper. An experiment with three thermocouples is carried out to validate the max grinding temperature and the character of temperature distribution predicted by the analytical and numerical model in this article. Various experiments were conducted to provide a broad range of process parameters. The comparison results show that: the values of max grinding temperature predicted by analytical and numerical model have well agreement with the measurement results in experiments and the relative errors are within 20%; the max grinding temperature values measured at the location of cut-in and cut-out are larger than the value in the middle of workpiece. The max grinding temperature and character of temperature distribution predicted by analytical and numerical model is validated by the experimental results.

Evaluation of Endurance Characterizations of Ceramic Thin Films Deposited on the Cemented Carbide Substrate by Cyclic Sphere Indentation Testing

The purpose of this study is to investigate aspects of ceramic thin film deposited on cemented carbide under cyclic sphere indentation loading and to clarify the possibility of the sphere indentation test to evaluate endurance characterizations of ceramic thin films. Three kinds of ceramic thin films were deposited onto cemented carbide WC-Co substrates. Cyclic sphere indentation tests were carried out by using spherical indenters of varying diameter 2R to investigate the aspects of crack initiation, wear progress, and delamination in ceramic film and to obtain the influence of the applied maximum load Pmax on the cyclic number of crack initiation Ni in thin films. The main conclusions are the following. (1) Ring crack initiate at the lower load than that of a ring crack initiation load obtained by static sphere indentation test. (2) After ring crack initiate, wear of film progresses inside the contact area, and delamination in thin film occur. (3) Quantitative evaluation of wear is possible by measuring the cross-sectional shape of contact area. (3)The Pmax - Ni relationships specifically depend on the diameter of spherical indenter 2R. (4) The effect of 2R on the relationship between tensile stress of film σr,i and Ni is smaller than that of the Pmax - Ni relationship.

Study on Contact Characteristics of Free Rolling Radial Tire

To study the rolling properties of a radial tire, an accurate 3D 195/60R14 tire model is established. The modal includes the geometric nonlinearity due to large deformation, material nonlinearity, the anisotropy of rubber-cord composites, the nonlinear boundary conditions from tire-rim contact and tire-pavement contact. The model can be used to simulate the changes of a rolling tire and calculate the tire deformation for various operating conditions. The profile of the inflated tire is studied experimentally and numerically. The simulation result is in good agreement with the test result. Some contact problems, such as the tire deformation, the shape of contact area, the contact pressure distribution, are discussed in detail.

Influence of Camber Angle on Rolling Radial Tire under Braking State

To study the rolling properties of a radial tire, an accurate 3D 195/60R14 tire model is established. The modal includes the geometric nonlinearity due to large deformation, material nonlinearity, the anisotropy of rubber-cord composites, the nonlinear boundary conditions from tire-rim contact and tire-pavement contact. The model can be used to simulate the changes of a rolling tire and calculate the tire deformation for various operating conditions. The profile of inflated tire is studied experimentally and numerically. The simulation result is in good agreement with the test result. Some contact problems, such as the tire deformation, the shape of contact area, the contact pressure distribution, are discussed in detail.

Shear Stress Analysis of EHL Oil Films Based on Thermal EHL Theory - In the Case of Elliptical Contact Condition -

Under the elliptical contact conditions with an ellipticity parameter of Ke=1.4, a non-Newtonian thermal EHL analysis was carried out. The lubricating oil was assumed to behave as a Maxwell fluid. Lubricating oil is the automotive traction oil with the viscosity grade of ISO VG32. Input parameters are maximum Hertzian pressure PH=1.5 GPa, entrainment velocity ue=10 m/s, slide-roll ratio Σ=0%∼4.0% and inlet oil temperature t0=413 K. The shear stress distribution under elliptical contact conditions showed a similar tendency to that obtained in point contact conditions, and it was found that the traction coefficients at maximum Hertzian pressure of PH=1.5 GPa are scarcely affected by the shape of contact area. Furthermore, although both the pressure distributions and the temperature distributions hardly changed up to the slide-roll ratio of Σ=1.0%, the considerable variation in the shear stress distributions was recognized.

Super-single tire loadings and their impacts on pavement design

Pavement design and analysis are generally performed based on the load equivalent factor (LEF) obtained from conventional dual tires and assume that the contact stress is equal to the tire inflation pressure. However, heavier tire loadings, such as super-single tires, produce much higher contact stresses than the inflation pressure. This results in larger deformations of subgrades, requiring advanced modeling of subgrades, such as elastic–plastic analysis. Super-single tires also have a different contact area shape from that of conventional tires. To assess the increased contact stresses by super-single tires, realistic contact stress distribution and contact area ratio for super-single tires should be used in the analysis. Three-dimensional finite element analyses of typical flexible pavements were done to evaluate the effects of the increased contact stresses of tire loadings on the subgrades, including load equivalency factors, overlay effect, and subgrade improvement as the behavior of subgrades becomes more important due to the increased contact stresses. Analysis results indicate that the increased contact stresses should be taken into account in the pavement structure design, as well as design of overlay or subgrade improvement. Based on the numerical results, simple design examples are suggested.

FEA and Testing Studies on Static Camber Performance of the Radial Tire

A three-dimensional non-linear FEA model of radial tire was established. The rebar model was employed to simulate complex multilayer cord-rubber composites and directly define the cord directions varying with their positions. Meanwhile, the geometric non-linearity due to large deformation, material non-linearity, and the non-linear boundary conditions from tire—pavement static camber contact were considered. The static camber performance of the radial tire was studied. Relationships among load and the tire deflection, the tire deformation, contact stress distribution, contact friction force distribution, side force, and deflection were discussed. A set of special testing equipment was designed to realize quasi-static loading with continuous loading and unloading. Then the static camber performance of the radial tire was tested. The contact pressure distribution and the shape of contact area in different camber states of the tire were measured by pre-scale films. The simulation result was in good agreement with the test result.