EXPERIMENTAL CHARACTERIZATION OF QUASI-STATIC AND SHOCK-WAVE BEHAVIOROF POROUS ALUMINUM

Experiments of quasi static hydrostatic and uniaxial strain compressio n, and of shock wave propagation performed on 9% and 17% porous alumin um are presented, analyzed, and compared. Quasi static experiments sho w the influence of coupling between void collapse and plasticity induc ed in the matrix on the material macroscopic behavior. The amount of p ore compaction appears to be enhanced by the deviatoric stress compone nt present in the uniaxial strain tests and not in the hydrostatic one s. The originality of the plate impact setup and its associated metrol ogy [velocity interferometer system for any reflector (VISAR) interfer ometry and polyvinylidene fluoride (PVDF) piezoelectric gages] exhibit s also the influence of these local physical mechanisms on shock wave propagation in porous aluminum. More, the variations observed between the rise times of shocks seem to point out a preponderance of the dyna mic effects (inertia or strain rate) over the material behavior. We ob serve indeed that the higher the stress in the material, the shorter t he shock rise time. This point is confirmed by comparing quasi static and dynamic responses of porous aluminum. Comparison of these experime ntal results to numerical simulations should be interesting to prove o r not this hypothesis. (C) 1998 American Institute of Physics. [S0021- 8979(98)00809-3].