Study On The Mechanics Properties Of Metal Foams And The Damage Behavior Of Its Meso-structure

The metal foam is a kind of light material which takes metal or alloy as the substrate and contains massive meso-holes. The meso-structure of metal foam has the significant influence on its mechanics properties. In this paper, with the aid of the finite element analysis software, we focused on the effects the heterogeneity of meso-structure of metal foam on its macro mechanics behaviors, and studied the evolution laws of the deformation, damages and failure. The main researches include,(1) Analysis the meso-structure of aluminum foam. The meso-structure of aluminum foam is very complicated. Here, we simplified it to a plane structure with multiple meso-holes which's radius obeys the given statistical distribution. The whole structure of aluminum foam is realized by the algorithm which includes the statistical characteristics of diameters and the random positions.(2) Simulate the lateral compression of aluminum foam. Through the analog computation, macroscopic mechanics properties of Al foam material can be obtained, which is compared with the experimental result and show the effectiveness of the numerical method. In the simulation,it's found that under the condition of uniaxial compression, the foam presents the characteristic of localized compressive bands, i.e., in some weak areas, the transverse compressive bands appears firstly with the increment of external load, which are the main contribution to the global compression.. To change the model's meso-structure parameters and the substrate parameters, the simulation results were fitted with the Gibson empirical formula, and the relationship among the mechanical properties of uniaxial compression, the substrate and the porosity of the foam can be obtained.(3) Simulate the biaxial compression of the aluminum foam with varied loadings. The biaxial compression with the same velocity shows the similar stress-strain relations in each direction. But once the compressive velocities are different, the mechanical properties also become different in two directions. When the transverse loading speed becomes bigger, the axial elasticity modulus also becomes bigger, while the platform yeild strain becomes smaller, buy the yield stress changes little. Comparing with the uniaxial compression, the Young's modulus and the yield stress of the biaxial compression increase obviously. The yield behavior of the aluminum foam model is analyzed under the condition of biaxial stresses, and yield-stress function in biaxial loading is fitted;(4) Simulate the the uniaxial tension of the aluminum foam. Its tensile process is as followings: Firstly, the stress concentration appears in some thin walls between holes ,then the bigger plastic deformation will continue to enlarge in some of these walls, and a weak transverse band appears to effort main strain, finally the sole weak band appear to destroy the specimen. The sole failure band limits the deformation, therefore the tension process of metal foams usual shows as brittle failure. The uniaxial tensions of Al foams with different porosity are simulated, and the tensile results are fitted by the Gibson's empirical formula. The relations among the mechanical properties of Al foam in uniaxial tension, the substrate and the porosity can be obtained.