Analysis Of Mechanical Properties Of Closed-cell Aluminum Foam Based On Porous Structure Parameters

The pore structure parameters of the aluminum foam are the most important parameters linked with the mechanical properties.Quantifying the relationship between the pore structure parameters and the mechanical properties of aluminum foam is of great significance for designing the structure of aluminum foam to expand its application range.However,the existing scaling-law equations based on relative density have limits in predicting the mechanical properties of aluminum foam.Therefore,this research studied the pore structure parameters of the aluminum foam by using imaging methods,and simulated a large number of mechanical performance data of real structural models by finite element simulation.A multi-parameter fitting method for calculating the mechanical properties of closed-cell aluminum foam(elastic modulus and plateau stress)was proposed.The new predictive equations for the mechanical properties of aluminum foam associate with pore structure parameters were calculated in this study with higher accuracy.The main research contents are as follows:1.Five closed-cell aluminum foam samples with porosity range from 77% to 91% were prepared by the melt foaming method.The CT images obtained by X-ray tomography were used to characterize the pore structure and reconstruct three-dimensional model of the samples by imaging methods.Image processing software like Image J,Avizo and skeletonization algorithm,were used to calculated the morphological parameters of the aluminum foam pore structure such as porosity,solid material thickness,pore size,sphericity,anisotropy,as well as the topological parameters,node number distribution and mean value of node included angle.The relationship between these parameters was discussed.Establishing the mathematical relationship between the pore structure parameters and the mechanical properties were also studied in this paper.2.A comprehensive modelling methodology of the mechanical behavior of cellular materials based on XRCT images was proposed and validated.The effect of mesh density and sample size on the accuracy of the results were considered.In this study,the incremental plastic theory of isotropic hardening materials was used to endow the model with mechanical properties.The stress-strain curve of aluminum foam calculated by finite element simulation were compared with the experiments results,and it founds that the elastic modulus value obtained by the simulation is higher than the experiment.However,the difference of the plateau stress values are relatively small.3.The multiple linear regression method was used to fit the mathematical equations between the pore structure parameters and the elastic modulus as well as the plateau stress of aluminum foam.The parameters were screened through the collinearity diagnosis in order to get non-standardized coefficients of each parameter in the multiple linear regression.Subsequently,a multi-parameter fitting elastic modulus and plateau stress prediction equation of closed-cell aluminum foam were obtained.The determination coefficients of the two prediction formulas are both greater than 0.86.Compared with the scaling-law formula that predicts mechanical properties only by porosity,the formula fitted in this paper has higher accuracy.