Effect of Loading Velocity on the Distribution of Residual Strength after Proof Testing of Ceramics.

Abstract

It has been commonly accepted that effective proof testing demands rapid loading-unloading to prevent strength degradation, and that the truncated strength depends upon the rate of unloading. The interpretation of the characteristics in the proof test of ceramic materials seems to be derived from the work by Fuller et al who analyzed the problem by adopting the fracture criterion 「K1gK1C ; K1 ; the stress intensity, K1C ; the critical fracture toughness」. In the present work, an analytical method is newly presented to characterize proof testing of a large population of ceramic samples. By analyzing the loading & unloading rate effect on the residual strength after proof testing, the accepted interpretation in proof testing has been rechecked ; it has become clear that the rapid unloading as well as rapid loading does not bring any improvement in residual strength distributions after proof test, but the average strength of survived samples rather decreases by the rapid loading and unloading. The obtained results are diametrically opposite to the ones which have been accepted as the common sense in proof testings.