The dependence of the dynamic material toughness on the velocity and on some loading parameters

Abstract

A recently proposed finite difference code, the SMF2D code, is used to simulate fast crack propagation in double cantilever beams (DCB) and single edge notch (SEN) specimens. The crack length-time history, whether measured experimentally, as in the DCB case, or conjectured, as in the SEN case, serves as input data. Several trial functions were used to simulate the initial acceleration phase since this phase has little available experimental data. Their effect on the overall results are found to be negligible except in the deceleration stage of crack propagation. Results for the cases investigated indicate that the dynamic material toughness is not a single valued function of crack velocity only, but that it also depends on some loading parameters and the specimen geometry.* On leave from the Technion-Israel Inst. of Technology. ** Kanninen [15] has called these "application phase" and "generation phase 'z calculations for convenience. *** Kid yn is to be distinguished from Kvv (the dynamic material toughness). The first entity is a measure of the instantaneous near tip stress field; the second is a material property correlated with the rate of energy absorbed during crack propagation (G~n). It is shown later that for crack velocities encountered in practice, the value of KI d~ and Klv are close. * In plane stress, C, must be defined appropriately. Yet the overall conclusion about the K dy°-K~ D interchangeability remains unaffected for speeds as high as 0.5 C,.

High speed double torsion tests on tough polymers. I: Linear elastic steady state and dynamic analysis

“…FD methods demand a time step size restriction to ensure numerical stability [27]. Generation mode calculations have also been made using moving grid techniques [28,29]. Numerical integration along the characteristics has also been employed to determine the evolving deformation in the DCB test piece [30].…”