金属泡沫断裂韧性的试验研究

金属泡沫在其实际应用中,断裂性能和断裂韧性对于承载的多孔金属泡沫有着重要的意义。基于美国试验材料学会相关标准,采用三点弯曲试样测定了铝泡沫的I型断裂韧性。研究表明,金属泡沫的断裂为脆性断裂,在裂纹尖端附近,孔壁最薄弱的区域最容易发生变形;随着进一步加载,一些孔壁发生断裂,微裂纹在断裂尖端附近出现。随着载荷的增加,主裂纹在缺口根部形成或由微裂纹合并而成,并开始在多孔结构内传播。裂纹沿着结构最薄弱处传播,并产生次生裂纹和裂纹桥。裂纹总的扩展方式还是I型断裂。根据试验P-V曲线特点,取最大载荷点对应的力与位移求解出铝泡沫的裂纹尖端临界张开位移的平均值为0.051 mm。

Experimental investigation on fracture toughness of metal foam

In practical applications, fracture properties and fracture toughness of porous metal foam for the bearing are very important. In this paper, based on ASTM standards, three-point bending of aluminum foam samples are used to determine I type fracture toughness. It is shown that the fracture of metal foam is brittle fracture. The deformation is localized to thinnest regions of the cell walls surrounding the crack tip. With further loading, the strain to fracture is reached in some cell walls and microcracks appear in the vicinity of the crack tip. With increasing load a main crack is initiated at the notch root or at the pre-crack by a coalescence of microcracks, and starts to propagate through the cell structure. The crack follows the weakest path through the structure and builds thereby secondary and crack bridges. The way of crack extension is I type fracture in all. According to the P-V curve characteristics, taking the force and displacement of maximum load point to calculate critical crack tip opening displacement, the average is 0.051mm.