Experimental investigation of the quasi-static mixed-mode crack initiation in NiCr/ZrO2functionally graded materials by digital image correlation
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摘要: 采用粉末冶金方法制备出NiCr/ZrO2功能梯度材料FGMs。通过2种断裂试件研究了材料梯度对混合型断裂行为的影响(FGM-A试件,裂纹位于试件的弹性模量较大一侧;FGM-B试件,裂纹位于试件的弹性模量较小一侧)。对2种断裂试件在非对称载荷下进行准静态断裂实验,并利用数字散斑相关方法测得Ⅰ、Ⅱ型应力强度因子。结果表明:FGM-A的裂纹的开裂角小于FGM-B的开裂角;FGM-A的弹性梯度对静态裂纹有保护作用;弹性模量的梯度变化和裂尖局部材料的断裂韧性会影响混合型裂纹的启裂。Abstract: The NiCr/ZrO2 functionally graded materials (FGMs) were fabricated by the powder metallurgy. To study the effect of material gradient on the mixed-mode crack initiation,two types of fracture samples were prepared:FGM-A corresponding to the specimen with the crack situated on the stiffer side and FGM-B corresponding to the specimen with the crack situated on the compliant side. The quasi-static fracture tests were conducted under the unsymmetrical loading conditions,and the full-field digital image correlation (DIC) was used to obtain the stress intensity factors KⅠand KⅡ. The experimental results show that the kinking angle of FGM-A is less than the one of FGM-B;the crack of FGM-A is shielded by the elastic gradient and the mixed-mode crack initiation is influenced by the elastic gradient and the local fracture toughness.
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