Original paper(Vol.46 No.2 pp.113)
Load maximum condition and Hart's instability criterion in uniaxial impact tensile testing
Nojima Taketoshi; Kobayashi Hidetoshi
Abstract:The maximum load condition and Hart's instability criterion for the growth of area imperfection have been analytically studied in uniaxial tensile tests under various impact loadings. Three kind of typical loading pulses (a conventional constant incident pulse, diminishing incident (deceleration) pulse and ramp loading (acceleration) pulse) were selected for the study.
It has been clarified by the analysis that a strain amount, where load reaches a maximum value, becomes larger with an increase in acceleration rate of the loading pulse, and therefore the maximum strength becomes higher with increasing acceleration rate. Hart's criterion is reformulated so as to be directly applied to investigate an instability point on stress strain curves obtained by the tests. The correlation between the maximum load point and Hart's instability point have been clarified under impact loading conditions.
Key Words:impact strength, plastic instability, ductility, material testing, tensile properties