An interrupted tensile testing at high strain rates for pure copper bars

Abstract

A high-speed tensile facility ͑HSTF͒ invented by us was applied to interrupting the tests for pure copper specimen bars controlled locally at different levels of elongation. It was realized to isolate and identify the different stages of the dynamic fracture process of the pure copper specimen bar under impact tension. The results of scanning electron microscopical ͑SEM͒ investigation of the recovered pure copper specimens show that the void evolution near the surface of the minimum cross-section of the necking area is more severe than that at the middle of the necking area, which may be connected with the findings discussed by Alves and Jones ͓J. Mech. Phys. Solids 47, 643 ͑1999͔͒. The constitutive models in a certain range of strain determined from the tensile split Hopkinson bar optimized by us were employed and adjusted in numerically simulating the large deformation of the pure copper specimen in the interrupted tensile tests on HSTF. The dependence of the instability strain of thermoviscoplastic materials in simple tension on material parameters delineated by Batra and Wei ͓Int. J. Impact Eng. 34, 448 ͑2007͔͒ was inspected in predicting the diffuse necking of the specimen bar. The axisymmetric necking rod model with a central void under static tension presented by Ragab ͓Eng. Fract. Mech. 71, 1515 ͑2004͔͒ was extended to predicting the local necking and fracture of the specimen bar under impact tension.

Influencia de la geometría del proyectil en ensayos dinámicos de tracción

“…El modelo numérico permitió comprobar el cumplimiento de las hipótesis de la teoría de las ondas unidimensionales referente al comportamiento de las barras [20] [21], como lo es el hecho que la deformación en el interior de las barras es la misma que en la superficie [22].…”

Numerical analysis of the influence of the damping rings’ dimensions on interrupted dynamic tension experiment results

“…In the beginning of 90 s, a method to interrupt Hopkinson experiments was developed by Nemat-Nasser et al, 23 which was based on the absorption of the reflected waves for controlling the deformation level of the specimen. Dongfang et al 24 developed a high-speed tensile facility to interrupt the fracture tests for pure copper specimen at different levels of elongation. Essa et al 25 developed a convenient approach to interrupt a SHTB test, which is described below.…”

Influence of Damping Ring Material on Dynamic Tensile Tests

“…In the beginning of 90s, a method to interrupt Hopkinson experiments was developed by Nemat-Nasser et al [25], which was based on the absorption of the reflected waves for controlling the deformation level of the specimen. Ma et al [26] developed a high-speed tensile facility to interrupt the fracture tests for pure copper specimen at different levels of elongation. El-Saeid Essa et al [27] developed a convenient approach to interrupt a SHTB test, which is described below.…”