The Experimental Investigation On Dynamic Properties Of The Metallic Porous Materials

The metallic porous materials possess many superiority properties. Particularly, the materials can suffer large region deformation under constant lower stress level. Because of these properties the materials can satisfy the requirement of some engineering fields, such as packing, impact/blast mitigation system. They have been widely used in automotive, aerospace, railway transport, building, package and so on. It is very difficulty to determine the dynamic properties of materials in high strain rates with test methods. The research mainly focuses on the quasi-static properties of metallic porous materials and investigation results of dynamic properties are very limited.According to analyze investigation results of dynamic properties of metallic porous materials, it is found that the accurate of experimental methods are important because of the special internal structures of the materials. In order to identify the initial dynamic collapse strength and plateau stress and to investigate the effect of strain rate and the effect of velocity by tests, existing test methods are compared, the shortage of SHPB test technique is analyzed and betterment methods are given in this paper. A directimpact device- also is designed based on the current SHPB. The transfer function h(t) is given using the deconvolution in inverse analysis with computer simulation. The direct impact device is dynamically calibrated. The data processing system is performed and an efficient method to investigate the dynamic behavior of metallic cellular materials is afforded.The original Taylor model is extended in order to provide a theoretical basis for testing ductile porous materials in this paper. The main difference between solids and porous materials is that porous materials are compressible and their density changes with the compressive strain. Calculations have been made for porous materials with a relative density that is a linear function of compression strain e, i.e., ρ /ρ0=1+ae. The method can be used to determine the dynamic yield stress.The dynamic compression experiments of the bronze alloy porous materials and iron alloy porous materials were carried out with the SHPB technique. It is found that the dynamic behavior of these two metallic porous materials is very sensitive to strain rate and speed effects that the materials' yield stress is increased with the increase of the strain rates. There is an elastic phase in the initial compression stage. The two materials' plateau stress is evidenced when the strain is low. However, the yield plateau is unclear while the strain rate is increasing. Company with the enhancement of the strain, the stress enhanced gradually and it is very difficult todistinguish the boundary between plateau region and densified region. Moreover, the stress of the porous mental with lower porosity is higher than that with higher porosity on the condition of the similar strain rates and same strain. While the deformation of the porous mental with lower porosity are smaller than that with higher porosity under the same impact force.