Elastic/Plastic Indentation Damage in Ceramics: The Median/Radial Crack System

Journal of the American Ceramic Society - Tập 63 Số 9-10 - Trang 574-581 - 1980
Brian R. Lawn1,2,3, A.G. Evans2,3, D. B. Marshall4,3,5
1At the time this work was done, B. R. Lawn was on study leave from the University of New South Wales.
2Department of Materials Science and Mineral Engineering, University of California, Berkeley, California 94720
3Member, the American Ceramic Society.
4Department of Applied Physics, School of Physics, University of New South Wales, New South Wales 2033, Australia
5Now with the Department of Materials Science and Engineering, University of California, Berkeley, California 94720.

Tóm tắt

A theory for describing the evolution of the median/radial crack system in the far field of sharp‐indenter contacts is developed. Analysis is based on a model in which the complex elastic/plastic field beneath the indenter is resolved into elastic and residual components. The elastic component, being reversible, assumes a secondary role in the fracture process: although it does enhance downward (median) extension during the loading half‐cycle, it suppresses surface (radial) extension to the extent that significant growth continues during unloading. The residual component accordingly provides the primary driving force for the crack configuration in the final stages of evolution, where the crack tends to near‐half‐penny geometry. On the hypothesis that the origin of the irreversible field lies in the accommodation of an expanding plastic hardness impression by the surrounding elastic matrix, the ensuing fracture mechanics relations for equilibrium crack growth are found to involve the ratio hardness‐to‐modulus as well as toughness. Observations of crack evolution in soda‐lime glass provide a suitable calibration of indentation coefficients in these relations. The calibrated equations are then demonstrated to be capable of predicting the widely variable median and radial growth characteristics observed in other ceramic materials. The theory is shown to have a vital bearing on important practical areas of ceramics evaluation, including toughness and strength.

Từ khóa


Tài liệu tham khảo

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Thông tin xuất bản

Journal of the American Ceramic Society

Tập 63 Số 9-10

574-581

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