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Gibson-Ashby单元模型成功地用于高孔隙率的开孔泡沫金属材料的弹性模量和屈服应力的预测,但基于该模型的破坏强度(应变)公式尚未建立,而在拉伸等条件下,泡沫金属的细观结构破坏对材料性质产生重大影响.本文重点研究在拉伸条件下Gibson-Ashby单元的破坏模式,通过综合考虑单元内水平梁的弯曲和立柱拉伸综合效应,建立起更一般性的泡沫金属材料单元的弹性模量、屈服应力(应变)公式.并且应用塑性铰长度的概念,成功地推导出单元的破坏应变.进而用单元结构几何参数的概率分布来表征泡沫金属的细观非均匀性,从而分别推导出了开孔泡沫金属单元材料参数的概率分布函数,并以此建立了涵盖支持中、高孔隙率泡沫金属的拉伸本构关系.通过对单元弹性模量、屈服应变与破坏应变的概率分布分析,指出它们的概率分布均存在近似的但不相互独立的等效Weibull分布,这说明在研究材料常数的细观统计特性时,有必要考虑材料的细观变形和破坏特性.
The Gibson-Ashby unit model has been successfully used to predict the elastic modulus and yield stress of open-cell foamed metal materials with high porosity. However, the formula of failure strength (strain) based on this model has not been established yet. However, The destruction of the microstructure of the foam metal has a significant effect on the material properties.In this paper, the failure modes of Gibson-Ashby cells under tensile conditions are studied in detail, and by combining the bending of the horizontal beams and the combined effects of column stretching, The formula of the elastic modulus and yield stress (strain) of the foam metal material, and successfully deduced the failure strain of the unit by the concept of the plastic hinge length. Then the probability distribution of the geometric parameters of the unit structure is used to characterize the fineness of the foam metal View of the nonhomogeneity, the probability distribution function of the parameters of the open-cell metal foam cells is deduced respectively, and the tensile constitutive relation of the metal foam supported by the medium- and high-porosity foams is built up.Through the calculation of the unit elastic modulus, Yield strain and failure strain probability distribution analysis, pointed out that their probability distributions are similar but not independent Weibull equivalent , Indicating when the statistical properties of microscopic study material constants, it is necessary to consider the material properties of mesoscopic deformation and damage.