Quantitative Evaluation of Multiple Cracking Damage by Means of Direct Current Potential Difference Method with Multiple-Type Probe

多型探头直流电位差法定量评价多重裂纹损伤

• 批准号: 12650086
• 负责人: TADA Naoya
• 金额: $ 2.62万
• 依托单位: OKAYAMA UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650086/
• 关键词: Multiple-type probe; DC potential difference method; Multiple cracks; Fatigue

The objective of the present research is to establish a method of quantitative evaluation of crack distribution from two-dimensional distribution of potential difference which can be measured by means of multiple-type probe. The multiple-type probe is composed of a lot of probes which are aligned in two rectangular directions. Although a conventional method, where only a pair of probes are used for measuring potential difference, has been applied to multiple cracking damage, it was impossible to determine whether relatively small number of large cracks exist or relatively large number of small cracks exist. In this study, electric field analysis and experiment were carried out and the following results were obtained.1. The distribution of potential difference between two adjacent probes in multiple-type probe was calculated for known distribution of cracks and the relationship between the distribution of potential difference and that of cracks was formulated.2. Using the formula, a method of quantitative evaluation of areal density (i. e. , the number of cracks in unit area) and mean length of cracks from mean and standard deviation of potential difference was proposed. The validity of the method was assured by numerical experiment.3. A new evaluation method of the distribution of microscopic strain on the surface of specimen was proposed. In this method, micro-grid at intervals of about 10μm was described in advance on the surface of specimen using roughness tester, and a change in the shape of each grid was measured to evaluate the strain. This method was applied to small fatigued plate specimens of pure copper. Strain showed a relatively large scatter in microscopic scale and this seemed to be caused by microstructural inhomogeneity such as the difference in crystallographic orientations among neighboring grains. It was thought that the non-uniform strain of grains brought about crack initiation on the surface of specimen.

本研究的目的是建立一种由多型探针测量的二维电位差分布定量评价裂纹分布的方法。多型探头由多个探头沿两个矩形方向排列组成。尽管仅使用一对探针测量电位差的传统方法已被应用于多裂纹损伤，但不可能确定是否存在相对少量的大裂纹或相对大量的小裂纹。本研究通过电场分析和实验研究，得到了以下结果.在已知裂纹分布的情况下，计算了多型探头中相邻两探头间的电位差分布，并建立了电位差分布与裂纹分布之间的关系.利用该公式，提出了一种定量评价面密度的方法。e.提出了由电位差的平均值和标准差计算单位面积裂纹数和裂纹平均长度的方法。通过数值试验验证了该方法的有效性.提出了一种新的评价试样表面微观应变分布的方法。在该方法中，使用粗糙度测试仪在样品表面上预先描述间隔约为10μm的微网格，并测量每个网格的形状变化以评估应变。该方法适用于纯铜小平板疲劳试件。应变表现出相对较大的分散在微观尺度上，这似乎是由微观结构的不均匀性，如相邻晶粒之间的晶体取向的差异。分析认为，晶粒的不均匀应变是试样表面裂纹萌生的主要原因。

项目成果

Naoya Tada: "Evaluation of Size, Shape and Location of a Semi-Elliptical Surface Crack by Direct Current Electrical Potential Method with Multiple-Type Probe"Proceedings of the 39th Symposium on Strength of Materials at High Temperatures. 160-164 (2001)

Naoya Tada：“使用多型探头的直流电势法评估半椭圆表面裂纹的尺寸、形状和位置”第39届高温材料强度研讨会论文集。

多田直哉: "多数分布き裂型高温疲労損傷の直流電位差法による非破壊定量評価"日本材料学会第38回高温強度シンポジウム前刷集. 63-66 (2000)

Naoya Tada：“利用直流电位法对多分布裂纹型高温疲劳损伤进行无损定量评估”，日本材料学会第38届高温强度研讨会预印本集63-66（2000）。

Naoya Tada: "Non-Destructive Evaluation of Distribution of Cracks by Means of DC-EPM with Multiple-Type Probe"Proceedings of the 2000 Annual Meeting of JSME/MMD. No. 00-19. 317-318 (2000)

Naoya Tada：“采用多型探头 DC-EPM 对裂纹分布进行无损评估”JSME/MMD 2000 年年会论文集。

多田直哉: "多端子型直流電位差法によるき裂分布の非破壊評価"日本機械学会材料力学部門講演会講演論文集. No.00-19. 317-318 (2000)

Naoya Tada：“使用多端子直流电位法对裂纹分布进行无损评估”，日本机械工程学会材料力学分部论文集，第 317-318 号（2000 年）。

多田直哉: "微小平板試験片を用いた純銅の繰り返し引張り"日本機械学会中国四国支部 第40期総会・講演会講演論文集. No.025-1. 47-48 (2002)

Naoya Tada：“使用微板测试件的纯铜的重复拉伸”日本机械工程师学会中国-四国分会第40届会议记录和演讲No.025-48（2002年）。