Determination of materials parameters under dynamic loading: Part II: Optimization

In the combined experimental/numerical/optimization approach adopted in this work, the constants of material models are identified by optimizing the difference between the numerical and experimental profiles of specimen after deformation without using experimental stress–strain curve. Three materials including two low carbon steels and an aluminum alloy are used in this investigation. The constants of Johnson–Cook (J–C) model are identified from tension, compression and using optimization technique with different number of variables. The quasi-static related constants of the model are also determined from compressive quasi-static tests. The constants obtained in different ways nearly coincide and verify the approach adopted in this investigation. The constants of Zerilli–Armstrong (Z–A) and power law plasticity (P-L) models are also identified. The results indicate that J–C and Z–A models can accurately describe the behaviour of two of the materials used in this work but the power law model proves not to be an appropriate model for the two forgoing materials. This is thought to be due to the reason that the model cannot incorporate thermal effects in a thermo/mechanical stress analysis adopted in the present work. On the other hand, the power law model is found to be capable of describing the flow stress of materials which show temperature hardening/softening behaviour in tensile tests using least square method. The reason is that the model’s constants could be defined in terms of temperature.