Abstract Quasi static crack growth of Al/Al2O3 functionally graded materials prepared through powder metallurgy up to 30% weight fraction of Al2O3 is studied with crack on stiff (FGM I) and compliant (FGM II) sides using crack gauge in three point bend test. The variation of weight fraction of Al2O3 with distance from 100% aluminum face is measured through image analyzers to identify the composition corresponding to crack tip location. The measurement of crack tip location, load point displacement and load with time are carried out simultaneously. It is observed that crack grows stably when the crack traverses from stiff to compliant side and unstably from Compliant to stiff side. For stable quasi static crack growth (crack on stiff side), variation of the fracture toughness and crack tip opening displacement (CTOD) are evaluated and increase with distance from stiff side. Further, the fracture toughness is also evaluated using Raveendran’s micromechanics prediction techniques and found that the experimental values are closer to Raveendran’s lower bound for greater weight fraction of alumina and closer to Raveendran’s upper bound for lower ceramic weight fraction. From fractography, mixed mode failure with greater deviation of crack path for FGM I is observed as compared to mode-I failure for FGM II.

中文翻译：

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使用裂纹规研究铝/氧化铝功能梯度材料的准静态裂纹扩展

摘要 在三点弯曲试验中使用裂纹规研究了通过粉末冶金制备的 Al/Al2O3 功能梯度材料的准静态裂纹扩展，Al2O3 的重量分数高达 30%，并在刚性 (FGM I) 和柔顺 (FGM II) 侧开裂。通过图像分析仪测量 Al2O3 的重量分数随距 100% 铝面距离的变化，以确定对应于裂纹尖端位置的成分。裂纹尖端位置、载荷点位移和载荷随时间的测量同时进行。观察到，当裂纹从刚性侧向柔顺侧移动，从柔顺侧向刚性侧不稳定时，裂纹扩展稳定。对于稳定的准静态裂纹扩展（刚性侧裂纹），评估断裂韧性和裂纹尖端张开位移 (CTOD) 的变化，并随着与刚性侧的距离增加而增加。此外，还使用 ​​Raveendran 的微观力学预测技术评估了断裂韧性，发现实验值更接近 Raveendran 的下限（氧化铝的重量分数较大）和 Raveendran 的上限（陶瓷重量分数较低）。从断口分析，观察到与 FGM II 的模式 I 故障相比，FGM I 的裂纹路径偏差更大的混合模式故障。还使用 Raveendran 的微观力学预测技术评估了断裂韧性，发现实验值更接近 Raveendran 的下限（对于较大的氧化铝重量分数）和更接近 Raveendran 的上限（对于较低的陶瓷重量分数）。从断口分析，观察到与 FGM II 的模式 I 故障相比，FGM I 的裂纹路径偏差更大的混合模式故障。还使用 Raveendran 的微观力学预测技术评估了断裂韧性，发现实验值更接近 Raveendran 的下限（对于较大的氧化铝重量分数）和更接近 Raveendran 的上限（对于较低的陶瓷重量分数）。从断口分析，观察到与 FGM II 的模式 I 故障相比，FGM I 的裂纹路径偏差更大的混合模式故障。