Optional Strain-Rate Forms for the Johnson Cook Constitutive Model and the Role of the Parameter Epsilon_0^1

A brief review of the standard Johnson-Cook model is presented. Three optional strain-rate forms are introduced and calibrated to laboratory data for A36 steel. Next a brief description of the LS-DYNA implementation of the new strain-rate forms within the existing viscoplastic formulation of the JohnsonCook model is presented. Finally, all four calibrated strain-rate forms are exercised in single element uniaxial stress test simulations, and the results are compared with the A36 steel effective stress versus effective plastic strain data at three different strain rates. The comparison of the calibrated model response to the quasi-static A36 steel data is used to illustrate the role of the Johnson-Cook & parameter ε 0 .

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