STATIC AND CYCLIC FRETTING FATIGUE BEHAVIOR OF SILICON-NITRIDE

A cyclic fretting fatigue test machine was constructed. The piezo-elec tric bimorphs were used as actuators for cyclic loading and fretting m otion at the resonance frequency of the system. Fretting fatigue tests under static and cyclic loading conditions were carried out using HIP -sintered silicon nitride. From the experimental results, it was found that fretting fatigue strengths under the two test conditions were id entical and hence the effect of cyclic loading on fretting fatigue str ength of silicon nitride was almost negligible. A fretting crack initi ated in a very early stage of the fatigue life at the position of the maximum frictional stress in the contact area. Fretting fatigue life p rediction based on fracture mechanics was also carried out. The predic ted lives were in good agreement with the experimental results.