Study On Compression Deformation Behaviors And Mechanical Properties Of Aluminium Foams

Aluminium foams, a new structural and functional material developed in recent years, has good energy absorption and impact damping property. Therefore, it is of the vital significance to study compressive deformation behaviors and energy absorption property under static and dynamic load. Now aluminum foams has been intensively studied abroad and successfully applied in many fields. However, the research is not adequate in China. The most is focused on the uniaxial compressive behavior and still remains in testing stage. Many researches, such as the compositive influences and interaction of porosity,material,pore sizes and sample dimensions on compression property, the tensile deformation characteristic and mechanism, composite, fatigue, anisotropy are paid little attention.Based on above-mentioned, the author carried out the researches. The content and results are showed as follows:(1)The compression deformation characteristic of open aluminium foams and the effects of porosity,material,pore sizes and sample dimensions on comprssion property were investigated by orthagonal experiments, which can provide necessary theory for the application of energy absorption. Three types of stress-strain curves are obtained and can be distinguished. The curves of aluminium foams based on pure Al can be divided into three regions: elastic region, yield region, densification region. In contrast, brittle alloy foams show a stress peak if strain go beyond the elastic region and a corresponding drop in stress levels over a large strain range afterwards. The material has the most influence on compression property; next, porosity; pore size has little effect; sample dimension effects is the lowest, but the stress of smaller speciments is higher than the bigger'. (2)The compression deformation characteristic of closed aluminium foams and the effects of porosity and existing defects on comprssion property were investigated.(3)The tensile property of aluminium foams were investigated. Tensile deformation is low and the tensile stress is no more than 10 Mpa. No macro-neck was observed during deformation. Tension failure of specimens with open pores is caused by rapid expansion of cracks, however, the failure of samples with closed pores is caused by stress concentration resulted from the deformation at the carried place. The stress is linear to the strain for open foams made with pure Al. The dates of tensile stress and deformation of brittle AlSi12 foams show much fluctuation. The deformation of Al foams with closed pores are characteristic of plastic deformation. Its typical stress-strain curves could be divided into four regions: linear elastic region, yield region, strain stiffening region and failure region.(4)The stress-strain curves of composite structure of stainless pipe filled with aluminium foams core are similar to the pure Al foams. Its fluctuation has correspondence with the folds. In contrast to the stainless pipe, the compressive deformation pattern of composite changed from asymmetry deformation to symmetry. The average yield stress is higher than the summation of the average stress of pipe and yield stress of aluminium foams.(5)The linear elastic and buckling deformation characterstic and mechanism were theoretically analyzed and simulated using ANSYS.