Shear Stress Hardening Curves of AISI 4130 Steel at Ultra-high Strain Rates with Taylor Impact Tests

Abstract

This paper is concerned with shear properties of AISI 4130 steel at various strain rates from the quasi-static state to ultra-high strain rates using a Taylor impact testing machine. Shear properties of metallic materials are known to be sensitive to the strain rate especially at high strain rates. In order to investigate hardening behavior under shear loading, in-plane shear tests are carried out at a wide range of strain rates from 10–3 s–1 to 103 s–1 with an INSTRON 5583 and a High Speed Material Testing Machine with a novel procedure to obtain hardening curves from shear tests. To induce shear deformation at ultra-high strain rates, a novel shear specimen applicable to Taylor impact tests is designed and then shear tests are conducted with a Taylor impact testing machine. Hardening curves are extrapolated by a dynamic hardening model and then calibrated by an experimental–numerical hybrid method with an inverse optimization scheme so that finite element analysis results match to shear tests results at ultra-high strain rates with the Taylor impact test. Shear fracture strains at ultra-high strain rates are also calibrated in the same manner. Calibrated flow stresses are higher than the extrapolated ones before calibration and calibrated shear fracture strains decrease more rapidly than the extrapolated ones before calibration at the ultra-high strain rate region.