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Abstract. In literature, the hysteresis phenomenon in rolling contacts is studied considering both rolling friction and sliding friction. Removal of sliding friction in experimental tests from a concentrated contact is a serious challenge. The paper proposes a method and presents a device ensuring pure rolling between two identical discs, normally loaded. Using photoelastic material for the two rolling discs, by means of photoelastic method, the hysteresis phenomenon due to rolling friction is qualitatively confirmed.

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The present paper approaches the tribological aspects of the oral cavity, emphasizing stress state in dental biocontacts. Stress state influences the biomechanical fatigue microcrack propagation mechanism, which is finally manifested over a very small area on tooth interface. The cracks can be nucleated on the surface, on the subsurface, or both, depending on the quality of dental materials, restoration accuracy, physiological or pathological conditions, as well as on the initial and interface stresses. The groups of stresses that act upon a nucleate crack on the dental biocontact surface are contact, interface, and initial stresses. While tribological processes in natural biocontacts take place in conventional conditions that are controlled by the biosystem in which they are integrated, things are not the same in biocontacts between a natural and an artificial material, which constitutes the subject of this paper.