Microscopic Fracture Mechanics Study on Mechanisms of Small Fatigue Crack Propagation by Micro Beam X-ray Stress Evaluation

微观断裂力学研究微束X射线应力评估小疲劳裂纹扩展机制

基本信息

批准号：
13305011
负责人：
TANAKA Keisuke
金额：
$ 32.03万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13305011/
关键词：
Fatigue Crack Composites X-ray stress measurement Fracture mechanics Microbeamn X-rays Fracture mechanisms Micromechanics 微視機構

项目摘要

1. A new system of microbeam stress measurement was developed by using a high intensity X-ray generator and a position sensitive detector. The stress in the area of about 100 μm was measured with a high precision by the new system. The system was also used to measure the in-plane stress in the surface region of thin films with submicrometer thickness.2. With the use of a high intensity X-rays from a synchrotron source, SPring-8, the stresses in the near crack-tip region in steel, ceramics and composites were successfully measured and used to predict the propagation behavior of cracks.3. Using electron back scattering pattern and atomic force microscopy, the crystallographic condition of fatigue crack initiation in fine-grained steels is proposed. In the early stage of fatigue crack propagation, the crack deflection and branching increase the resistance of crack propagation.4. The crack deflection and branching induce the fatigue crack closure level, and the crack propagation rate was a unique function of the effective stress intensity factor range.5. The effects of the grain boundaries and second phase on fatigue crack propagation was modeled by the blocked slip band near the crack tip. The crack closure is further included in the model. The relative role of microstructural barriers and crack closure on the threshold condition of small fatigue cracks were calarified.6. The effect of mixed mode loading on the fatigue crack propagation behavior was studied by using a precracked hollow cylinder under mixed torsional and axial loading. The fatigue crack propagation direction is controlled by the maximum range of tangential stress near the crack tip.

1.开发了一种新的微束应力测量系统，采用高强度X射线发生器和位置敏感探测器，新系统可以高精度测量约100μm区域的应力。还用于测量亚微米厚度薄膜表面区域的面内应力。2．利用同步加速器源SPring-8 发出的高强度X 射线，测量了裂纹尖端附近的应力。钢铁区域， 3．利用电子背散射图和原子力显微镜，提出了细晶钢疲劳裂纹萌生的晶体学条件。裂纹扩展、偏转和分支增加了裂纹扩展的阻力。4．裂纹扩展和扩展导致疲劳裂纹闭合水平，裂纹扩展速率是有效应力强度因子的唯一函数。 5. 晶界和第二相对疲劳裂纹扩展的影响通过裂纹尖端附近的阻塞滑移带进行了建模。模型中进一步包括了微观结构障碍和裂纹闭合的相对作用。 6．利用预裂纹空心圆柱体，研究了扭转和轴向混合载荷下混合模式载荷对疲劳裂纹扩展行为的影响。裂纹尖端附近的切向应力。