Method for Calculating Plastic Deformation of High Resolution and Large Contact Area

2021 ◽  
Vol 144 (1) ◽  
Author(s):  
S. Sklenak ◽  
D. Mevissen ◽  
J. Brimmers ◽  
C. Brecher
Keyword(s):  
Plastic Deformation ◽  
High Resolution ◽  
Pressure Distribution ◽  
Rough Surface ◽  
Tribological Properties ◽  
Contact Area ◽  
Three Dimensional ◽  
Rolling Contact ◽  
Contact Algorithm ◽  
Large Contact Area

Abstract In a rolling contact, the tribological properties in terms of friction, wear, and fatigue are significantly influenced by the surface roughness. Due to solid contact of the surfaces in the contact area, the roughness and thus also the tribological properties change during the service life of the contact. The initial load leads to major changes of the tribological properties figured out by Brecher et al. (2019, “Influence of the Metalworking Fluid on the Micropitting Wear of Gears,” Wear, 61(434–435), p. 202996). Prediction of the initial changes in topography in the contact area is necessary for specific optimization of rolling contacts. Especially for dry rolling–sliding contact, the roughness of the surfaces is crucial for the lifetime, which is part of the investigations within the DFG priority program 2074 (357505886). In this work, an elastic-plastic contact algorithm for calculating plastic deformation for dry contact of rough surfaces with large contact area and high resolution is presented. Due to the nonlinearity behavior associated with plastic deformation, the plastic contact algorithm is based on an iterative approach. An optimized meshing strategy is implemented to calculate the elastic pressure distribution on the surface. Corresponding to the two-dimensional pressure distribution, the three-dimensional stress distribution allows the consideration of residual stresses and interactions of the microscopic peaks of the rough surface. Furthermore, the three-dimensional plastic strain distribution allows the application of an analytical approach to represent the plastic deformation of the surface. Finally, the solution of a plastic contact calculation with an exemplary topography measured on a real rough surface is presented.

Method for Calculating Normal Pressure Distribution of High Resolution and Large Contact Area

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
C. Brecher ◽  
D. Renkens ◽  
C. Löpenhaus
Keyword(s):  
High Resolution ◽  
Pressure Distribution ◽  
Surface Topography ◽  
Contact Area ◽  
Normal Pressure ◽  
Rolling Contact ◽  
Sliding Contacts ◽  
Contact Areas ◽  
Irregular Grids ◽  
Disk Rolling

The exact calculation of contact stresses below the surface is the basis for optimizing load capacity of heavily loaded rolling–sliding contacts. The level of stress is significantly influenced by the normal pressure distribution within the contact area, which occurs as a result of the transferred normal force and the contact geometry. In this paper, a new method for high resolution pressure calculation of large contact areas is presented. By this, measured surface topography can be taken into account. The basis of the calculation method is the half-space theory according to Boussinesq/Love. Instead of regular grids, optimized meshing strategies are applied to influence the calculation efforts for large contact areas. Two objectives are pursued with the targeted meshing strategy: on the one hand, the necessary resolution for measured surface structures can be realized; while on the other hand, the total number of elements is reduced by a coarse grid in the surrounding areas. In this way, rolling–sliding contacts with large contact areas become computable with conventional simulation computers. Using the newly developed “method of combined solutions,” the overall result is finally composed by the combination of section of separate solutions, which are calculated by consecutively shifting the finely meshed segment over the entire contact area. The vital advancement in this procedure is the introduction of irregular grids, through which the cross influences are not neglected and fully regarded for every separate calculation. The presented methodology is verified stepwise in comparison to the Hertzian theory. The influence of irregular grids on the calculation quality is examined in particular. Finally, the calculation approach is applied to a real disk-on-disk rolling contact based on measured surface topography.

Plasto-Elastohydrodynamic Lubrication in Point Contacts for Surfaces With Three-Dimensional Sinusoidal Waviness and Real Machined Roughness

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Tao He ◽  
Ning Ren ◽  
Dong Zhu ◽  
Jiaxu Wang
Keyword(s):  
Plastic Deformation ◽  
Rough Surface ◽  
Mechanical Design ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Von Mises Stress ◽  
Asperity Contacts ◽  
Lubrication Characteristics ◽  
Von Mises

Efficiency and durability are among the top concerns in mechanical design to minimize environmental impact and conserve natural resources while fulfilling performance requirements. Today mechanical systems are more compact, lightweight, and transmit more power than ever before, which imposes great challenges to designers. Under the circumstances, some simplified analyses may no longer be satisfactory, and in-depth studies on mixed lubrication characteristics, taking into account the effects of 3D surface roughness and possible plastic deformation, are certainly needed. In this paper, the recently developed plasto-elastohydrodynamic lubrication (PEHL) model is employed, and numerous cases with both sinusoidal waviness and real machined roughness are analyzed. It is observed that plastic deformation may occur due to localized high pressure peaks caused by the rough surface asperity contacts, even though the external load is still considerably below the critical load determined at the onset of plastic deformation in the corresponding smooth surface contact. It is also found, based on a series of cases analyzed, that the roughness height, wavelength, material hardening property, and operating conditions may all have significant influences on the PEHL performance, subsurface von Mises stress field, residual stresses, and plastic strains. Generally, the presence of plastic deformation may significantly reduce some of the pressure spikes and peak values of subsurface stresses and make the load support more evenly distributed among all the rough surface asperities in contact.

Three-dimensional dynamic hip contact area and pressure distribution during activities of daily living

2006 ◽  
Vol 39 (11) ◽  
pp. 1996-2004 ◽  
Author(s):  
H. Yoshida ◽  
A. Faust ◽  
J. Wilckens ◽  
M. Kitagawa ◽  
J. Fetto ◽  
...  
Keyword(s):  
Activities Of Daily Living ◽  
Pressure Distribution ◽  
Contact Area ◽  
Daily Living ◽  
Three Dimensional

Rolling Contact With Friction and Non-Hertzian Pressure Distribution

1989 ◽  
Vol 56 (4) ◽  
pp. 814-820 ◽  
Author(s):  
C. Liu ◽  
B. Paul
Keyword(s):  
Pressure Distribution ◽  
Numerical Technique ◽  
Contact Region ◽  
Three Dimensional ◽  
Contact Problems ◽  
Rolling Contact ◽  
Sliding Contact ◽  
Hertzian Contact ◽  
Limiting Case ◽  
Large Spin

A numerical technique has been developed to deal with three-dimensional rolling contact problems with an arbitrary contact region under an arbitrary pressure. Results of this technique are checked against existing solutions for cases of Hertzian contact. A solution for a case of non-Hertzian contact is also presented. This numerical technique works satisfactorily for cases with small spin creepage. For cases of large spin creepage, we utilize a recent work (by the authors) for the limiting case of fully developed sliding contact.

scholarly journals DESIGNING A SHAPED SEAT-PAN CUSHION TO IMPROVE POSTURAL (DIS)COMFORT REDUCING PRESSURE DISTRIBUTION AND INCREASING CONTACT AREA AT THE INTERFACE

2021 ◽  
Vol 1 ◽  
pp. 1113-1122
Author(s):  
Iolanda Fiorillo ◽  
Yu Song ◽  
Peter Vink ◽  
Alessandro Naddeo
Keyword(s):  
Pressure Distribution ◽  
Contact Area ◽  
Geometric Shape ◽  
Average Pressure ◽  
Health Issues ◽  
Two Factors ◽  
Physical Prototype ◽  
Large Contact Area ◽  
Prototype Design ◽  
Straightforward Approach

AbstractRemaining seated for extended periods increases the risk health issues and discomfort perception. Consequently, the seat-pan design is crucial and could be mainly influenced by two factors: pressure distribution and seat contour. For seat pan discomfort, the lower average pressure is accompanied by less discomfort. Moreover, a seat contour with a large contact area is correlated with more comfort. Thus, a shaped cushion had been accurately designed (Virtual Prototype) and realized (Physical Prototype) aiming to translate the pressure distribution due to interaction between seat and buttock in a geometric shape, suitable for the international population (including P5 females and P95 males). With this shape, the pressure should be more uniform and lower, the contact area at interface bigger, and the perceived comfort higher. Both Virtual and Physical Prototype design had been described in this paper through a repeatable and straightforward approach. Also, experiments had been performed to validate the hypothesis through a comparison with a standard flat cushion. Results showed the goal of the design had been reached: the shaped cushion scored less pressure distribution and higher contact area than the flat cushion.

Simulation of Plasto-Elastohydrodynamic Lubrication in a Rolling Contact

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Tao He ◽  
Dong Zhu ◽  
Jiaxu Wang
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Rolling Direction ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Surface Plastic Deformation ◽  
Rolling Contact ◽  
Surface Plastic ◽  
Contact Center ◽  
Elastic Plastic

Surface plastic deformation due to contact (lubricated or dry) widely exists in many mechanical components, as subsurface stress caused by high-pressure concentrated in the contact zone often exceeds the material yielding limit, and the plastic strain accumulates when the load is increased and/or repeatedly applied to the surface in a rolling contact. However, previous plasto-elastohydrodynamic lubrication (PEHL) studies were mainly for the preliminary case of having a rigid ball (or roller) rotating on a stationary elastic–plastic flat with a fixed contact center, for which the numerical simulation is relatively simple. This paper presents an efficient method for simulating PEHL in a rolling contact. The von Mises yield criteria are used for determining the plastic zone, and the total computation domain is discretized into a number of cuboidal elements underneath the contacting surface, each one is considered as a cuboid with uniform plastic strain inside. The residual stress and surface plastic deformation resulted from the plastic strain can be solved as a half-space eigenstrain–eigenstress problem. A combination of three-dimensional (3D) and two-dimensional (2D) discrete convolution and fast Fourier transform (DC-FFT) techniques is used for accelerating the computation. It is observed that if a rigid ball rolls on an elastic–plastic surface, the characteristics of PEHL lubricant film thickness and pressure distribution are different from those of PEHL in the preliminary cases previously investigated. It is also found that with the increase of rolling cycles, the increment of plastic strain accumulation gradually approaches a stable value or drops down to zero, determined by the applied load and the material hardening properties, eventually causing a groove along the rolling direction. Simulation results for different material hardening properties are also compared to reveal the effect of body materials on the PEHL behaviors.

Unloading Process in Elastic-Plastic Contact of a Rough Surface With a Flat

2008 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Finite Element ◽  
Rough Surface ◽  
Contact Force ◽  
Contact Area ◽  
Three Dimensional ◽  
Integral Form ◽  
Real Contact Area ◽  
Elastic Plastic ◽  
Real Contact ◽  
Approximate Equations

Three dimensional elastic-plastic contact of a nominally flat rough surface and a flat is considered. The asperity level Finite Element based constitutive equations relating contact force and real contact area to the interference is used. The statistical summation of asperity interaction during unloading phase is derived in integral form. Approximate equations are found that describe in closed form contact load as a function of mean plane separation during unloading. The approximate equations provide accuracy to within 6 percent for the unload phase of the contact force.

Wheel–rail impact and the dynamic forces at discrete supports of rails in the presence of singular rail surface defects

2011 ◽  
Vol 226 (2) ◽  
pp. 124-139 ◽  
Author(s):  
X Zhao ◽  
Z Li ◽  
J Liu
Keyword(s):  
Surface Defects ◽  
Three Dimensional ◽  
Element Model ◽  
Rolling Contact ◽  
Dynamic Responses ◽  
Railway Track ◽  
Vertical Force ◽  
Detailed Model ◽  
Contact Algorithm ◽  
Dynamic Forces

A validated three-dimensional (3D) transient finite element model is used to evaluate the wheel–rail impact at singular rail surface defects and the resulted high-frequency dynamic forces at the discrete supports of the rail. A typical ballasted railway track is modeled, in which the supports of the rail are composed of the fastenings, the sleepers, and the ballast. The primary suspension of the vehicle is considered. To include all the important eigen characteristics of the vehicle–track system, the wheel set, the rail, and the sleepers are all meshed using 3D solid elements. The transient wheel–rail rolling contact is solved using a surface-to-surface contact algorithm in the time domain. By simulating the steady-state rolling of a wheel set on a smooth rail, the vertical force distribution at the discrete supports is first compared with Zimmermann solution. Afterward, rail surface defects are applied to calculate the resulted dynamic forces at thewheel–rail interface and at the discrete supports of the rail under different rolling speeds. The obtained dynamic responses confirm the necessity of using such a detailed model for the investigations.

scholarly journals Modelling a Coupled Thermoelectromechanical Behaviour of Contact Elements via Fractal Surfaces

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
G. Mazzucco ◽  
F. Moro ◽  
M. Guarnieri
Keyword(s):  
Contact Area ◽  
Electrical Contact ◽  
Micromechanical Model ◽  
Computational Cost ◽  
Three Dimensional ◽  
Local Stress ◽  
Theory Approach ◽  
Contact Algorithm ◽  
Effective Contact ◽  
Contact Surfaces

A three-dimensional coupled thermoelectromechanical model for electrical connectors is here proposed to evaluate local stress and temperature distributions around the contact area of electric connectors under different applied loads. A micromechanical numerical model has been developed by merging together the contact theory approach, which makes use of the so-called roughness parameters obtained from experimental measurements on real contact surfaces, with the topology description of the rough surface via the theory of fractal geometry. Particularly, the variation of asperities has been evaluated via the Weierstrass-Mandelbrot function. In this way the micromechanical model allowed for an upgraded contact algorithm in terms of effective contact area and thermal and electrical contact conductivities. Such an algorithm is subsequently implemented to construct a global model for performing transient thermoelectromechanical analyses without the need of simulating roughness asperities of contact surfaces, so reducing the computational cost. A comparison between numerical and analytical results shows that the adopted procedure is suitable to simulate the transient thermoelectromechanical response of electric connectors.

Rolling and Sliding Contact Stress Parameters in Elastohydrodynamic Lubrication

1967 ◽  
Vol 34 (2) ◽  
pp. 471-477 ◽  
Author(s):  
R. A. Schoeppel ◽  
R. M. Evan-Iwanowski
Keyword(s):  
Pressure Distribution ◽  
Contact Stress ◽  
Contact Area ◽  
Elastohydrodynamic Lubrication ◽  
Considerable Change ◽  
Rolling Contact ◽  
Shear Stresses ◽  
High Speeds ◽  
Pressure Peak ◽  
Distribution Studies

The fatigue life at high operating speeds of machine components, such as bearings, gears, and cams, depends upon the shape and magnitude of the elastohydrodynamic pressure distribution. Studies show that two bodies in rolling contact at high speeds indicate a significant departure from the usual Hertzian pressure distribution present at low rolling speeds. The contact stress distribution for an elastohydrodynamic pressure distribution in an infinitely large plate is determined in this paper. The pressure peak on the outlet side of the contact area and the long pressure sweep on the inlet side of the contact area create a pressure distribution which is asymmetrical. The pressure peak has a significant effect on the normal and shear stresses. Superimposing contact stresses due to sliding indicates a considerable change in the stresses resulting from sliding direction.

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