Shear Stresses Below Asperities in Hertzian Contact as Measured by Photoelasticity

1973 ◽  
Vol 95 (3) ◽  
pp. 277-283 ◽  
Author(s):  
R. L. Leibensperger ◽  
T. M. Brittain
Keyword(s):  
Surface Roughness ◽  
Three Dimensional ◽  
Contact Fatigue ◽  
Hertzian Contact ◽  
Contact Theory ◽  
Shear Stresses ◽  
Asperity Contact ◽  
Surface Shear ◽  
Stress Theory ◽  
Effect Of Surface

The effect of surface roughness on shear stresses below the surface of an unlubricated Hertzian contact is analyzed using a three dimensional stress freezing photoelastic technique. The shear stresses in the micro-Hertzian contact in each asperity are shown to combine and form, at a greater depth below the surface, shear stresses generally associated with contact stress theory. These macro-Hertzian stresses are compared with the micro-Hertzian stresses in the asperities. The results are also correlated with an existing asperity contact theory and are discussed in relation to the contact fatigue phenomenon.

scholarly journals Analytical Elastostatic Contact Mechanics of Highly-Loaded Contacts of Varying Conformity

Lubricants ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 89 ◽  
Author(s):  
Patricia M. Johns-Rahnejat ◽  
Nader Dolatabadi ◽  
Homer Rahnejat
Keyword(s):  
Contact Mechanics ◽  
Contact Fatigue ◽  
Elastic Half Space ◽  
Hertzian Contact ◽  
Shear Stresses ◽  
Surface Shear ◽  
Replacement Arthroplasty ◽  
Load Carrying ◽  
Determining Factors ◽  
Highly Loaded

In applications requiring high load carrying capacity, conforming contacting pairs with a relatively large contact footprint are used. These include circular arc, Novikov, and Wildhaber gears found, for example, in helicopter rotors. Closely conforming contacts also occur in many natural endo-articular joints, such as hips, or their replacement arthroplasty. The main determining factors in contact fatigue are the sub-surface shear stresses. For highly loaded contacts, classical Hertzian contact mechanics is used for many gears, bearings, and joints. However, the theory is essentially for concentrated counterforming contacts, where the problem is reduced to a rigid ellipsoidal solid penetrating an equivalent semi-infinite elastic half-space. Applicability is limited though, and the theory is often used inappropriately for contacts of varying degrees of conformity. This paper presents a generic contact mechanics approach for the determination of sub-surface stresses, which is applicable to both highly conforming as well as concentrated counterforming contacts. It is shown that sub-surface shear stresses alter in magnitude and disposition according to contact conformity, and lead to the different modes of fatigue failure noted in practice.

Material Response to Rolling Contact Loading

1985 ◽  
Vol 107 (3) ◽  
pp. 359-364 ◽  
Author(s):  
A. P. Voskamp
Keyword(s):  
Rolling Contact Fatigue ◽  
Three Dimensional ◽  
Contact Fatigue ◽  
Load Cycle ◽  
Rolling Contact ◽  
Hertzian Contact ◽  
Microplastic Deformation ◽  
Contact Loading ◽  
Material Response ◽  
Deep Groove

The material response to rolling contact loading has been analyzed using quantitative X-ray diffraction methods. This has led to the discovery of preferred crystalline orientation in very narrow subsurface regions of endurance-tested 6309 deep groove ball bearing inner rings. The high hydrostatic pressure field, derived from the load-induced three-dimensional stress field in each Hertzian contact load cycle, allows substantial microplastic deformation to be accommodated in the subsurface layers. This microplastic deformation is accompanied by transformation of retained austenite, decay of martensite and the development of texture and residual stresses, one of which is a subsurface tensile stress in a direction normal to the surface. Both the preferred orientation and the tensile residual stress allow for crack propagation parallel to the rolling contact surface. Based on these findings, an outline of a qualitative model for rolling contact fatigue is presented.

The Effect of Surface Roughness on Contact Fatigue Behavior Using Mesoscopic Approach

2009 ◽  
Vol 36 (3) ◽  
pp. 269-276 ◽  
Author(s):  
Sang Don Lee ◽  
Tae Wan Kim ◽  
Yong Joo Cho
Keyword(s):  
Surface Roughness ◽  
Fatigue Behavior ◽  
Contact Fatigue ◽  
Effect Of Surface

Thermohydrodynamic Analysis of Submerged Oil Journal Bearings Considering Surface Roughness Effects

1997 ◽  
Vol 119 (1) ◽  
pp. 100-106 ◽  
Author(s):  
J. Ramesh ◽  
B. C. Majumdar ◽  
N. S. Rao
Keyword(s):  
Surface Roughness ◽  
Thermal Effects ◽  
Hydrodynamic Pressure ◽  
Height Distribution ◽  
Asperity Contact ◽  
Roughness Effects ◽  
State Behavior ◽  
Total Load ◽  
Contact Loads ◽  
Effect Of Surface

A theoretical study of a submerged oil journal bearing is made considering surface roughness and thermal effects. The total load-supporting ability under such condition is due to the thermohydrodynamic as well as the asperity contact pressure. The effect of surface roughness and viscosity-temperature dependency on hydrodynamic pressure has been found by solving the average Reynolds equation, energy equation and heat conduction equations simultaneously. The cavitation model of Jacobsson-Floberg has been modified to take the surface roughness effects into consideration. A parametric study of steady-state behavior has been carried out. Finally, the isothermal, thermohydrodynamic, and contact loads for a model bearing have been calculated, assuming the surface height distribution as Gaussian.

scholarly journals Investigation of the asperity point load mechanism for thermal elastohydrodynamic conditions

2019 ◽  
Vol 300 ◽  
pp. 06001
Author(s):  
Carl-Magnus Everitt ◽  
Bo Alfredsson
Keyword(s):  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Leading Edge ◽  
Point Load ◽  
Rolling Contact ◽  
Shear Stresses ◽  
Asperity Contact ◽  
Trailing Edge ◽  
Tensile Stresses ◽  
Lubrication Film

The rolling contact fatigue damage called pitting or spalling develops more frequently in surfaces with negative than positive slip. Since normal line loads do not cause any tensile surface stresses this investigation considers the effects of small point shaped asperities. Shear traction causes tensile stresses at the trailing edge of asperities entering the contact at negative slip. At positive slip the tensile stresses appear at the leading edge when the asperities exit the contact. It was found that the trailing edge of the asperity breaks through the lubrication film at contact entry. This causes negative slip to be more detrimental than positive slip. At negative slip the location of large frictional shear stresses and tension stresses from normal asperity contact coincide.

Calculation of Surface Roughness Effects on Air-Riding Seals

2004 ◽  
Vol 126 (1) ◽  
pp. 75-82 ◽  
Author(s):  
C. Guardino ◽  
J. W. Chew ◽  
N. J. Hills
Keyword(s):  
Surface Roughness ◽  
Compressible Flows ◽  
Reynolds Equation ◽  
Incompressible Flows ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Roughness Effects ◽  
Stationary Wall ◽  
Comparative Results ◽  
Effect Of Surface

The effects of surface roughness on air-riding seals are investigated here using the Rayleigh pad as an example. Both incompressible and compressible flows are considered using both CFD analysis and analytical/numerical solutions of the Reynolds equation for various two-dimensional or three-dimensional roughness patterns on the stationary wall. A “unit-based” approach for incompressible flows has also been employed and is shown to be computationally much less expensive than the full-geometry solution. Results are presented showing the effect of surface roughness on the net lift force. The effects of varying the Reynolds number are demonstrated, as well as comparative results for static stiffness.

Effect of Surface Roughness on Performance of Spiral Groove Gas Film Face Seal

2012 ◽  
Vol 184-185 ◽  
pp. 180-183 ◽  
Author(s):  
Gang Ma ◽  
Wei Zhao ◽  
Xin Min Shen
Keyword(s):  
Surface Roughness ◽  
Three Dimensional ◽  
Great Influence ◽  
Face Seal ◽  
Dimensional Model ◽  
Spiral Groove ◽  
Three Dimensional Model ◽  
Three Dimensional Flow ◽  
Gas Face Seal ◽  
Effect Of Surface

The three dimensional model was established for studying performance of spiral groove gas face seal. According to machining features of different surface area, the seal face can be divided into three parts, rotor ring grooved area, rotor ring non-grooved area and static ring area. The effect of roughness on seal performance was analyzed based on calculation of three dimensional flow field. The analysis results show that the surface roughness of rotor ring grooved area has great influence on the seal performance, but the influence is little when roughness on non-grooved rotor ring surface and static ring surface. The influence must be considered when surface roughness of rotor ring grooved area bigger than 0.2μm. Roughness of rotor ring surface can increase the loading force while it also can cause the increase of leakage. It is important to select rational roughness when designing gas face seal.

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