The effect of cell wall material strain and strain-rate hardening behaviour on the dynamic crush response of an aluminium multi-layered corrugated core

Abstract

The effect of the parameters of the Johnson and Cook material model on the direct impact crushing behaviour of a layered 1050 H14 aluminium corrugated structure was investigated numerically in LS-DYNA at quasi-static (0.0048 m s À1 ) and dynamic (20, 60, 150 and 250 m s À1 ) velocities. Numerical and experimental direct impact tests were performed by lunching a striker bar onto corrugated samples attached to the end of the incident bar of a Split Hopkinson Pressure Bar set-up. The numerical impact-end stress-time and velocity-time curves were further compared with those of rigid-perfectlyplastic-locking (r-p-p-l) model. Numerical and r-p-p-l model impact-end stress analysis revealed a shock mode at 150 and 250 m s À1 , transition mode at 60 m s À1 and quasi-static homogenous mode at 20 m s À1 . The increase of velocity from quasi-static to 20 m s À1 increased the numerical distal-end initial peak-stress, while it almost stayed constant between 20 and 250 m s À1 for all material models. The increased distal-end initial peak-stress of strain rate insensitive models from quasi-static to 20 m s À1 confirmed the effect of micro-inertia. The numerical models further indicated a negligible effect of used material models on the impact-end stress of investigated structure. Finally, the contribution of strain rate to the distal-end initial peak-stress of cellular structures made of low strain rate sensitive Al alloys was shown to be relatively low as compared with that of strain hardening and micro-inertia, but it might be substantial for the structures constructed using relatively high strain rate sensitive alloys.

Impact loading of functionally graded metal syntactic foams

“…Shock enhancement is often used to explain the strength increase of the material at high strain rates [31,32]. The r-p-p-l model predicts merely the shock stresses [12]. To this end, the variation of stress over time is calculated using the following procedure: The impact of a uniform cellular material on a rigid wall with an initial velocity of v o induces two distinct deformation regions: a crushed (densified) region with a stress of σ * (initial crushing stress) and the elastically deformed region as seen in Fig.…”

“…Their numerical study showed that above 100 s − 1 , the effect of strain rate sensitivity of matrix outweighs the effect of micro-inertia. Güden and Canbaz [12] investigated the strain rate hardening of a layered 1050 H14 aluminium corrugated structure both experimentally and numerically through a direct impact test method. It was shown that the initial peak stress of a low strain rate hardening aluminium alloy was mostly influenced by micro-inertia.…”