Study On The Dynamic Properties And Yield Behaviors Of Porous Metals

Porous metals are widely used in many industrial fields，such as aerospace，aircraft，automotive，railway and so on，because of their lightweight，highspecific stiffness and strength，ability of absorbing energy and electromagneticshielding properties. Due to the complex conditions under which porous metalsservice，it is important to industrial design and practical application that themechanical properties of the porous metals，especially the dynamic propertiesand yield behaviors in complex stress state，need to be studied further. In thispaper，experiment investigation and theoretical analysis were combined to carryout this research for the dynamic properties of porous bronze alloy and porousiron alloy and the yield behaviors of aluminum alloy foams.An experimentally investigation on the mechanical behavior of porousbronze alloy and porous iron alloy at high strain rates (102s-1~103s-1) usingSHPB apparatus was carried out in this study to explore the effects of relativedensity and strain rate. Furthermore，a multi-parameter constitutive model，which is able to fully describe the behavior of these porous metals wasdeveloped，and the relationship between the value of parameters and the relativedensities of materials was analyzed. Uniaxial tests and triaxial compression tests were performed on closed-cellaluminum alloy with three relative densities to explore their failure and yieldbehaviors under different loading conditions. Due to the different failuremechanism under uniaxial compressive and tensile loadings，the aluminum alloyfoams show the dissymmetry of uniaxial yield stress. Based on the results ofuniaxial and triaxial experiments，the experimental yield surface of aluminumalloy foams with three relative densities was obtained，and the relative densitiesof materials had insignificant influence on the shape of experimental yieldsurface.Five results had been obtained as follows：(1) Porous bronze alloy andporous iron alloy showed an approximate bi-linear stress-strain behavior withstrain hardening-like effect，and there was no significant bound between stressplateau stage and densification stage.(2) The strength of porous bronze alloyand porous iron alloy increased with increasing relative densities of materialsand decrease with the decrease of strain rate.(3) A multi-parameter constitutivemodel，which was able to fully describe the behavior of porous bronze，wasdeveloped. The prediction of model and our experimental results were comparedand the comparison showed that there was a good agreement between theprediction of model and experimental results.(4) The experimental yieldsurfaces of aluminum alloy foams with three relative densities were comparedwith the Gibson，Deshpande-Fleck and Miller yield criterions. The Miller yieldcriterion showed good agreement with experimental yield surface because it contained the plastic compressibility of materials and dissymmetry of uniaxialyield stress.(5) The relative densities of aluminum alloy foams which was in therange of10%to20%，had insignificant influence on the shape of experimentalyield surface of materials.