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In-situ observation rig using a scanning laser microscope and its application to the COD measurement of fatigue crack (Unifying the measure of severity controlling the crack growth rate in small and large cracks)

使用扫描激光显微镜的原位观察装置及其在疲劳裂纹COD测量中的应用（统一控制小裂纹和大裂纹中裂纹扩展速率的严重程度的测量）

基本信息

批准号：
07555627
负责人：
ODA Yasuji
金额：
$ 5.76万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

项目摘要

For engineering assessments of the integrity for component with a surface crack, it is useful to know the measure of severity controlling consistently the crack growth rate in the case of wide range of crack lengths and various loading conditions.In this research, fatigue crack growth tests were carried out and crack opening desplacement ranges (DELTACOD's) along a crack were measured in the neighborhood of the crack tip. The DELTACOD distributions under the same crack growth rate are almost the same, independent of crack length, applied stress level and manner of loading. Therefore, the DELTACOD distribution near a crack tip can be considered as a measure of severity controlling the crack growth rate.On the other hand, a elastic-plastic finite element approach shows that the maximum plastic strain at a crack tip is considered as a measure of severity. The same maximum plastic strain at a crack tip guarantees the same strain and crack opening distribution. Therefore the crack opening distribution is also a measure of severity.In-situ observation rig using a scanning laser microscope is useful for investigating crack opening behavior. Realtime high magnification image (up to*3500) could be obtained during fatigue tests in air.

对于具有表面裂纹的构件的完整性工程评价，在裂纹长度范围较大、载荷条件变化较大的情况下，确定能够一致控制裂纹扩展速率的严重程度度量是有意义的。在本研究中，进行了疲劳裂纹扩展试验，并测量了裂纹尖端附近沿裂纹的裂纹张开位移范围（DELTACOD）。相同裂纹扩展速率下的DELTACOD分布基本相同，与裂纹长度、外加应力水平和加载方式无关。因此，裂纹尖端附近的DELTACOD分布可以被认为是控制裂纹扩展速率的严重程度的度量。另一方面，弹塑性有限元方法表明，裂纹尖端的最大塑性应变被认为是严重程度的量度。裂纹尖端相同的最大塑性应变保证了相同的应变和裂纹张开分布。因此裂缝张开分布也是一种严重程度的度量。采用扫描激光显微镜的现场观测台是研究裂纹张开行为的有效工具。在空气中进行疲劳试验时，可获得实时高倍图像（高达3500倍）。