High–rate material modelling and validation using the Taylor cylinder impact test

Taylor cylinder impact testing is used to validate anisotropic elastoplastic constitutive modelling by comparing polycrystal computed yield–surface shapes (topography) with measured shapes from post–test Taylor specimens and quasi–static compression specimens. Measured yield–surface shapes are extracted from the experimental post–test geometries using classical r–value definitions modified for arbitrary stress state and specimen orientation. Rolled tantalum (body–centred–cubic metal) plate and clock–rolled zirconium (hexagonal–close–packed metal) plate are both investigated. The results indicate that an assumption of topography invariance with respect to strain rate is well justified for tantalum. However, a strong sensitivity of topography with respect to strain rate for zirconium was observed, implying that some accounting for a deformation mechanism rate–dependence associated with lower–symmetry materials should be included in the constitutive modelling. Discussion of the importance of this rate dependence and texture evolution in formulating constitutive models appropriate for FEM applications is provided.