Abstract
Using the finite element method, we investigate the elasto-plastic impact of a rigid sphere on a half-space of auxetic and metal foams. The validity of the Hertz theory for elastic impacts is investigated for both positive and negative Poisson’s ratio. For elastic impacts, the results from Hertz theory are accurate within 20 % with the finite element simulations. The plasticity is modeled using the Deshpande-Fleck metal foam yield criterion. This yield criterion allows for plastic compressibility and can also accommodate materials having a negative Poisson’s ratio. The elasto-plastic simulations reveal that the coefficient of restitution decreases as the impact velocity is increased. The coefficient of restitution is also least for materials having a zero plastic Poisson’s ratio. Our study suggests for maximum energy dissipation the plastic Poisson’s ratio should be close to zero.
Highlights
Auxetic materials exhibit superior properties when compared to conventional materials [1]
The objective of the current work is to perform elasto-plastic impact simulations on auxetic materials to identify the effect of the above-mentioned parameters on coefficient of restitution, plastic dissipation and peak force acting on the foam
As a precursor to the elasto-plastic impact we investigate the elastic impact of a rigid sphere impacting on a half-space
Summary
Auxetic materials exhibit superior properties when compared to conventional materials [1]. Many researchers have investigated the application of auxetic materials for blast and ballistic impact mitigation. These studies are usually performed by modeling the discrete lattice that represents a particular auxetic material [3,4,5]. Hou et al [6] compared the crushing strength of auxetic and regular honeycomb structures. They reported that for the same slenderness ratio, the auxetic honeycombs have a higher crushing strength when compared to regular honeycombs. This enhancement was attributed to the auxetic effect, even when the relative density of the auxetic honeycomb was higher when compared to the regular honeycombs
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