Model for Cyclic Fatigue of Quasi-Plastic Ceramics in Contact with Spheres

Published

September 1, 2000

Author(s)

K -. Lee, Yeon-Gil G. Jung, I M. Peterson, Brian R. Lawn, D H. Kim, S K. Lee

Abstract

A model of contact damage accumulation from cyclic loading with spheres and ensuing strength degradation in relatively tough, heterogeneous ceramics is developed. The damage takes the form of a quasiplastic zone beneath the contact, consisting of an array of closed frictional shear faults with attendant wing microcracks at their ends. Contact fatigue takes place by attrition of the frictional resistance at the sliding fault interfaces, in accordance with an empirical degradation law, allowing the microcracks to extend. At large numbers of cycles or loads the microcracks coalesce, ultimately into radial cracks. Fracture mechanics relations for the strength degradation as a function of number of cycles and contact load are derived. Indentation-strength data from two well-studied coarse-grain quasiplastic ceramics, a micaceous glass-ceramic and a silicon nitride, are used to evaluate the model. Comparative tests in static and cyclic contact loading confirm a dominant mechanical component in the fatigue. At the same time, the presence of water is shown to enhance the fatigue. The model accounts for the broader trends in the strength degradation data, and paves the way for consideration of key variables in microstructural design for optimum fatigue resistance.

Citation

Journal of the American Ceramic Society

Volume

83

Issue

No. 9

Pub Type

Journals

Keywords

contact damage, cyclic fatigue, quasiplastic materials, radial cracks, shear faults, strength degradation

Citation

Lee, K. , Jung, Y. , Peterson, I. , Lawn, B. , Kim, D. and Lee, S. (2000), Model for Cyclic Fatigue of Quasi-Plastic Ceramics in Contact with Spheres, Journal of the American Ceramic Society (Accessed December 15, 2024)