Abstract
A method was developed for creating single well-defined surface asperities using an imprint technique. The proposed method enables:•Creation of well-defined micrometre high asperities•Creation of asperities which survived more than 35 million EHL contact cycles•Damage tracing thanks to the possibility to control the damage initiation sites.The technique is based on rolling a hard disc with indents against a soft disc for creating single surface asperities. The contact pressure causes plastic deformation forcing material into the indents to create the asperities. The height of the asperities can be controlled by adjusting the applied force. After initial reshaping during the run-in process, the asperities were strong enough to survive more than 35 million elastohydrodynamic lubrication cycles, which should be of great interest for the researchers who investigate rolling contact fatigue experimentally. The method could also aid the research on the run-in process by enabling tracing the development of specific surface defects. Since the method can produce high and strong asperities it might also prove useful for investigations how asperities deform under sever contact conditions.
Highlights
Method introductionA method was developed to enable experimental investigations of single asperities in elastohydrodynamic lubrication, EHL, contacts
Highlights A new imprint method for creating micrometre high asperities Well defined asperities were created separated from the manufacturing roughness The created asperities survived more than 35 million EHL contact cycles Damage tracing was possible since the asperity position was controlled and known The method enables new kinds of fatigue experiments for EHL and RCF contacts
It can be used for EHL experiments of the lubricant flow around single well defined asperities, the shape changes of surface defects during run-in, the asperity attenuation theories [5] and investigations of the separation of the real and complementary effects caused by point asperities [6]
Summary
A method was developed to enable experimental investigations of single asperities in elastohydrodynamic lubrication, EHL, contacts. Experimental methods in the literature for adjusting the surface properties for EHL investigations have included indents, different kind of line groves and ridges and small sputtered chromium asperities. Some examples of investigations of indents in EHL contacts are Ville and Nelias [13], Coulin et al [14] and Lorösch [15] These experiments show that indents reduces the fatigue lives of the surfaces by creating pressure peaks. The method is believed to be of great interest for those investigating rolling contact fatigues because it allows for the numerical simulations of asperities to be compared to experiments. This can be of help in the areas of wear, EHL and RCF
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