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TWO-WEEK LOAN COpy This is a Librar~ Circulating Cop~ which ma~ be borrowed for two weeks. For a personal retention cop~, call Tech. Info. D iuision, Ext. '51f6 fa 79;~ DISCLAIMER This document was prepared as an account of work sponsored by the United States Government.

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It is known that nominally brittle materials may exhibit plastic deformation in indentation, scratching, and microcutting when the loaded region is sufficiently small. The present investigation is concerned with the erosive cutting of nominally brittle materials by the impact of a stream of solid particles and it is shown that ductile behavior should be observed when the particle size and velocity are within certain limits. Experiments on a number of nominally brittle materials confirm this prediction; the ductile behavior being inferred from both the rippled appearance of the eroded surface and the variation of volume removal with angle of impingement.

An experimental method is presented that enables stress intensity factors due to residual stress to be determined directly, without prior determination of the residual stress. The method is based on the crack compliance method, where a narrow cut is introduced progressively into the considered component, and the resulting strain change is measured by a strain gage. The required mathematical relations to determine stress intensity factors from strain measurements are established by means of some basic relations of linear elastic fracture mechanics. They are derived explicitly for two exemplary geometrical systems, which allowed for analytical treatment. Experimental data obtained in the case of a steel roller are presented and discussed.