Fatigue crack path prediction in UDIMET 720 nickel-based alloy single crystals
Fatigue crack path prediction in UDIMET 720 nickel-based alloy single crystals
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DOI：
10.1007/s11661-000-0058-6
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
Philippa Reed;X. D. Wu;Ian Sinclair
中科院分区：
文献类型：
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作者：
Philippa Reed;X. D. Wu;Ian Sinclair
研究了取向、外加应力状态、环境和温度对UDIMET 720单晶试样裂纹扩展和裂纹路径行为的影响。混合模式载荷、平面应力和真空条件促进了I期裂纹的扩展;将试验温度提高到600 °C并不能抑制真空条件下I期裂纹的扩展。当每个滑移系与名义裂纹生长平面相交时，考虑每个滑移系的局部分解剪切应力强度和局部分解法向应力强度，可以预测第一阶段裂纹路径，阐明二次单晶测试取向的重要性（即，名义裂纹扩展方向以及有效拉伸轴）。开口和剪切的组合被发现，以促进第一阶段的裂纹扩展，并已建立的边界条件内，第一阶段的裂纹是促进。高度偏转的阶段I裂纹产生了显着的屏蔽效应，但在适当的混合模式加载，高度定向，共面阶段I裂纹生长可以产生。混合模式加载下的内在阶段I开裂似乎大大加速相比，模式I为主的阶段II裂纹扩展可比的应力强度水平。
The effect of orientation, applied stress state, environment, and temperature on the crack growth and crack-path behavior of single-crystal specimens of UDIMET 720 has been examined. Stage I cracking has been promoted by mixed-mode loading, plane stress, and vacuum conditions; increasing the test temperature to 600 °C does not suppress stage I crack growth in vacuum. Consideration of the local resolved shear-stress intensity and local resolved normal-stress intensity for each slip system as it intersects the nominal crack-growth plane allows the prediction of stage I crack paths, clarifying the importance of secondary single-crystal testing orientation (i.e., nominal crack-growth direction as well as effective tensile axis). Acombinationof both opening and shearing are found to promote stage I crack growth, and boundary conditions have been established within which stage I cracking is promoted. Highly deflected stage I cracking gives rise to significant shielding effects, but under suitable mixed-mode loading, highly oriented, coplanar stage I crack growth can be produced. Intrinsic stage I cracking under mixed-mode loading appears to be greatly accelerated compared with mode I-dominated stage II crack growth for comparable stress-intensity levels.