Strain field measurement around the crack tip in Ni-base superalloy using Digital Image Correlation
Strain field measurement around the crack tip in Ni-base superalloy using Digital Image Correlation
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DOI：
10.1299/transjsme.18-00246
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Yuki Otsuka;M. Sakaguchi;Y. Kurokawa;H. Inoue
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文献类型：
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作者：
Yuki Otsuka;M. Sakaguchi;Y. Kurokawa;H. Inoue
采用数字图像相关（DIC）方法测量了镍基单晶高温合金裂纹尖端周围的应变场。装配DIC系统，分别测量室温、700℃和900℃下的应变场。研究了结晶取向和温度对裂纹尖端应变场的影响。在室温下的一系列测量结果表明，裂纹以剪切方式扩展，裂纹尖端周围的应变场受到沿八面体滑移体系的各向异性塑性变形的强烈影响。基于沿滑移系的剪切应变分量，可视化了晶体取向对应变场的影响，可视化应变场对裂纹扩展路径和扩展速率提供了合理的解释。而在700℃时，裂纹以张开方式扩展，裂纹尖端周围出现对称剪切应变场。温度对应变场和由此产生的裂纹模式的影响可以用滑移系统的活动性来解释。现有DIC系统在900℃时也能测量裂纹的应变场，900℃时裂纹尖端周围的应变大于700℃时的应变。
Digital Image Correlation (DIC) method was applied to measure the strain fields around the crack tip in a Ni-base single crystal superalloy. DIC systems were assembled to appropriately measure the strain fields at room temperature, 700 ˚C and 900 ˚C. Influences of crystallographic orientation and temperature on the crack tip strain fields were investigated. A series of measurement at room temperature revealed that cracks propagated in shearing mode and the strain fields around the crack tip were strongly affected by anisotropic plastic deformation along the octahedral slip system. Based on the shear strain components along the slip systems, effect of the crystal orientation on the strain field was visualized, and the visualized strain field provided a reasonable explanation on the crack propagation path and propagation rate. At 700 ˚C, on the contrary, cracks propagated in opening mode and symmetric shear strain fields were measured around the crack tip. Temperature dependent strain fields and resultant cracking modes were explained by the slip system activity which was also influenced by temperature. The present DIC systems could measure the strain field even at 900 ˚C, and it was found that the strain around the crack tip was higher at 900 ˚C than that at 700 ˚C.