泡沫金属在单、双向载荷作用下的拉伸破坏行为初探

Tensile Failure Behavior of Metal Foams under Uniaxial and Biaxial Loads

摘要:

采用低载拉伸试验机对多孔体的单、双向拉伸进行了系列实验，通过分析该材料的单向拉伸破坏机制，发现开孔泡沫金属材料的宏观断裂特点既不同于最大拉应力准则的横向断裂，也不同于最大剪应力准则的塑性流动破坏，而是表现为介于它们之间的一种复杂断裂形式；拉伸断裂过程中多孔体的延伸率主要由三维网络中的金属丝体发生的塑性偏转所造成。通过其双向承载时断裂形态的观测分析，发现泡沫体十字型样品在双向等速拉伸载荷作用下的应力场分布与双向异速拉伸载荷作用下的类似，且其应力场的最大应力线为靠近样品中央载荷区边缘的四次对称曲边四边形。

Abstract:

In the present work, the low-load uniaxial and biaxial tensile testers were employed to carry out the uniaxial and biaxial tensions systemically for porous metal bodies at different uniaxial and biaxial tensile rates. The uniaxial tensile failure mechanism is analyzed, and the results show that the macroscopical failure behavior of the foam metals with open cells differ from either the transverse rupture by maximum tensile stress criterion, or the plastic flow failure by maximum shearing stress criterion, but behaves a complicated failure mode between these two criterions. In addition, the percentage elongation after fracture results mainly from the plastic deflexion of metallic struts within the three-dimensional reticulated structure, hardly from the plastic deformation of the metallic body under uniaxial tension. From the fracture morphologies under biaxial tension, it is found that the distribution of the stress field in the cruciform specimens of the foamed metal under biaxial equal-speed tension is similar to that under biaxial unequal-speed tension, and the maximum stress line of the stress field presents the four-fold symmetric curved-side tetragon.