The effect of grain size on the delayed yielding of mild steel

Abstract

A description is given of a new hydraulic rapid-loading machine, which is capable of applying a predetermined compressive stress in a time of the order of a few milliseconds and maintaining this stress constant up to and during the subsequent yielding of the specimen. Results of tests on mild steel are presented, giving the variation of yield delay time with applied stress and ferrite grain size. These results are discussed and interpreted in terms of two proposed yield models based on dislocation theory. The effect of grain size on the static yield behaviour is also considered.