The relationship of the critical stress versus impulse theory of spall fracture to the stress-gradient theory

Abstract

A spall fracture criterion based on critical stress versus stress gra&ent is briefly revaewed and discussed, An extension of a technique us~ by Tuler and Butcher is employed to show that the results of the stress-gradient theory can be interpreted in terms of criteria involving critical stress versus either impulse or pulse duration. The latter criteria are represented by smooth curves that depend on two parameters--the static strength limat for long-duration loads and an impulse limit for short-duration loads. Expressions for these parameters are presented in terms of the two parameters of the stress-gradient theory. Examples are ~resented for submicrosecond loads on 1100 aluminum and copper that show the stress-impulse interpretation differs little from the pure-impulse interpretation of Tuler and Butcher.

Time-dependent fracture criteria for 6061-T6 aluminum under stress-wave loading in uniaxial strain

“…The commonly used criteria are: (1) constant critical tensile stress [5]; (2) stress rate or stress gradient 1-12] and [21] ; (3) empirical algebraic relationships between stress and impulse or time [7], [9], and [10]; and (4) rate process criterion [7]. The functional forms of each of these criteria are summarized in Table 3.…”

“…Recent investigations [7], [9], [10], and [-12] have attempted to describe failure more realistically under wave propagation conditions by postulating criteria which combine more than one parameter, e.g., peak tensile stress versus tensile impulse and/or tensile pulse duration, or peak tensile stress versus stress gradient. The present work uses the spallation data generated by the exploding-foil technique, in conjunction with the data of [4], [5], [13], and [14] to construct a failure criterion for 6061-T6 aluminum.…”