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Experimental investigation for the theory of environment assisted cracking on local environmental conditions

局部环境条件下环境辅助破裂理论的实验研究

基本信息

批准号：
09305008
负责人：
SHOJI Tetsuo
金额：
$ 24.19万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

A theoretical formulation of crack growth rate based on the film rupture/slip dissolution mechanism was proposed by the head of investigators of this project. However, it is difficult to evaluate crack growth rate quantitatively because of diversities of mechanical, metallurgical, environmental and their interaction parameters. Measurements of local conditions around crack tip were required for the parameters included in the theoretical formulation, aiming which quantitative information of the local environmental condition was the most important. Accordingly, this project was started from 1997 and main achievements can be summarized as follows.(1) Although the sampled volume could be reduced from 50μL to 2μL by the improvement of the micro-sampling system, it was still needed to reduce the sampled volume. A novel sampling method was developed in this study and optimization was performed. Maximum resolution could be improved to about 5ppb of ClィイD1-ィエD1 and SOィイD32-(/)4ィエD3. The experim … More ents mentioned above was performed on the specimens made of both low alloy and stainless steels in high temperature, high pressure water environments.(2) Local physical properties of surface film formed due to the local active environment were measured by atomic force microscope and magnetic force microscope, and it turned out that electrical and magnetic properties of films could be changed in different environment. In-situ contact electric resistance (CER) measurements were performed in high temperature, high pressure water as an in-situ local measurement of local physical properties of surface film. Results showed that CER of the film depends on corrosion potential, temperature and materials.(3) Results showed that the parameter "m" for dissolution characteristics of new bare surface was very important, which depends strongly on crack tip solution chemistry. The effect of crack tip strain rate on parameter "m" was taken into account in the theoretical formulation. Unknown parameters were obtained by inverse analysis. The results of theoretical analysis were in good agreement with experimental results. Less

该项目的研究负责人提出了基于薄膜破裂/滑移溶解机制的裂纹扩展速率的理论公式。然而，由于机械、冶金、环境及其相互作用参数的多样性，定量评估裂纹扩展速率是很困难的。理论公式中包含的参数需要对裂纹尖端周围的局部条件进行测量，其中局部环境条件的定量信息是最重要的。据此，该项目从1997年开始，主要成果概括如下：(1)虽然通过微量进样系统的改进，进样量可以从50μL减少到2μL，但仍需要减少进样量。本研究开发了一种新颖的采样方法并进行了优化。 ClィイD1-ィエD1和SOィイD32-(/)4ィエD3的最大分辨率可提高至约5ppb。上述实验是在高温、高压水环境中对低合金和不锈钢制成的试件进行的。(2)利用原子力显微镜和磁力显微镜测量了由于局部活性环境而形成的表面薄膜的局部物理性质，发现薄膜的电学和磁学性质在不同的环境下会发生变化。原位接触电阻（CER）测量是在高温高压水中进行的，作为表面膜局部物理性质的原位局部测量。结果表明，薄膜的CER取决于腐蚀电位、温度和材料。(3)结果表明，新裸露表面溶解特性的参数“m”非常重要，它很大程度上取决于裂纹尖端溶液的化学性质。理论公式中考虑了裂纹尖端应变率对参数“m”的影响。通过反演分析得到未知参数。理论分析结果与实验结果吻合较好。较少的