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 finite-element model applications is provided.