Implementation and application of a new plasticity model in LS-DYNA including Lode angle dependency

It is consensual in the literature that plasticity can be a complex phenomenon to model, where the microstructure of a given material dramatically affects its behaviour at the macroscale. For instance, it has been found that, at the macroscale, many metallic alloys are dependent of the so-called Lode angle. However, in the current industrial scenario, the von Mises plasticity model (*MAT_24 in LS-DYNA), which is independent of the Lode angle, is still largely used in the crash simulation. Among several reasons, the von Mises model is fairly simple, only requiring the calibration of a hardening curve from a simple tensile test. In the present work, we have concentrated efforts in enhancing von Mises plasticity without loosing the benefits of its simplicity. Therefore, we have modified it in such manner that the effects of the Lode angle can be easily captured. In particular, special attention has been made concerning the easiness of calibration of the new material model. In sharp contrast to most Lode angle-dependent plasticity models available in the literature (which often demand time-consuming reverse engineering techniques for their calibration), the new model requires only a single additional parameter in comparison to the calibration of the von Mises model, where this additional parameter can be directly measured from an ordinary shear test. It is worthwhile noting that shear tests are usually carried out when characterising a given material in terms of failure (e.g. by employing the GISSMO failure model through the *MAT_ADD_EROSION keyword in LS-DYNA). As a matter of fact, the new proposed material model can be quickly calibrated by using data that is often already available, highly facilitating its direct use by end-users for industrial applications. In this contribution, we intend to highlight and clarify the need for a plasticity model with Lode angle dependency for more precise and reliable predictions in the crash simulation. The new material model will be then briefly presented, where special attention will be given in showing how it can be calibrated and employed in practical applications. Finally, it will be shown the improvement gained with the new model by simulating some experiments with LS-DYNA.