The Effect of Strain History on Crack Initiation Under Dynamic Loading
Paper describes an experimental investigation of crack initiation at high loading rates. Three metals were tested. The material was subjected to various types of preloading, namely, uni-axial as well as bi-axial tension beyond the yield point and cyclic loading (fatigue). The specimen was made in the form of a thin-walled tube, loaded with interior pressure in a split Hopkinson bar of special design. Crack initiation data were evaluated, using linear and non-linear fracture mechanics (KC dyn and JC dyn). Results indicate that JC dyn may be used in an initiation criterion. JC dyn is reduced by pre-loading and it is smaller than the corresponding JC static for the materials tested.
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