THE INFLUENCE OF LOADING RATE ON CRACK BRIDGING PROCESSES IN Al2O3
نویسندگان
چکیده
ÐCommercially available alumina of 94% nominal purity was used to examine the in ̄uence of loading rate on toughening mechanisms. For ®ne-grained alumina, the crack resistance, KR, was found to be independent of crack length and loading rate. Coarse-grained alumina exhibited strongly rising R-curves where the initial fracture toughness, K0, was found to be independent of the loading rate. The net toughening, DKSS, in coarse-grained alumina was found to decrease with increasing loading rate. Loading rate eects were independent of testing environment. A rate dependent coecient of friction was incorporated into a crack bridging model to describe the eect of loading rate on toughness in this system. Predictions based on the bridging models, using the measured coecients of friction for this material system, are in good agreement with the observed phenomenon. # 1998 Acta Metallurgica Inc.
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