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

Taylor cylinder impact testing is used to validate anisotropic elastoplasti c constitutive modelling by comparing polycrystal-computed yield-surface sh apes (topography) with measured shapes from post-test Taylor specimens and quasi-static compression specimens. Measured yield-surface shapes are extra cted from the experimental posttest geometries using classical r-value defi nitions modified for arbitrary stress state and specimen orientation. Rolle d tantalum (body-centred-cubic metal) plate and clock-rolled zirconium (hex agonal-close-packed metal) plate are both investigated. The results indicat e that an assumption of topography invariance with respect to strain rate i s 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 lowe r-symmetry materials should be included in the constitutive modelling. Disc ussion of the importance of this rate dependence and texture evolution in f ormulating constitutive models appropriate for finite-element model applica tions is provided.