Reliability Engineering Approach to Fatigue Crack Growth Rate by Constant <DELTA> K Tests

通过恒定 <DELTA> K 测试确定疲劳裂纹扩展率的可靠性工程方法

基本信息

批准号：
60550047
负责人：
ICHIKAWA Masahiro
金额：
$ 1.28万
依托单位：
The University of Electro-Communications
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1986
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60550047/
关键词：
Fatigue Crack Growth Rate Constant <DELTA> K Test Electric Potential Method Statistical Variability 信頼性工学

项目摘要

The purpose of this investigation is to clarify <DELTA> K dependence of variability of the fatigue crack growth rate da/dN by conducting statistical fatigue crack growth tests under the condition of constant <DELTA> K, and to estabilish the probabilistic formulation of da/dN, where <DELTA> K is the stress intensity range. The condition of constant <DELTA> K was attained using the contoured double cantilever beam specimen. The material used was the high strength steel HT60. 4 to 6 specimens were tested at each of six levels of <DELTA> K. In all 31 specimens were tested. da/dN was measured using DC electric potential method. In order to automize measurement and data processing, an automatic crack length measurement system using micro-computer was developed. Various efforts were made to attain high accuracy of measurement. For obtaining an effective method for analysis of the experimental data under constant <DELTA> K, the privious data under the condition of increasing <DELTA> K were reanalysed. The analysis showed that it was appropriate to regard variability of da/dN as composed of the two components : inter-specimen variability and intra-specimen variability. Next, the experimental data under constant <DELTA> K was analysed. First, variability of da/dN was decomposed into inter-specimen variabity and intraspecimen variabity using the method of analysis of variance. It was found that variability of da/dN under constant <DELTA> K was also composed of the above two components. Then, <DELTA> K dependence of these two components was examined. Neither inter-specimen variability nor intra-specimen variabity showed clear dependence on <DELTA> K, and thus, both the components could be regarded as consatnt independent of <DELTA> K. From the above result, it is concluded that an appropriate probabilitistic formulation of da/dN is to randomize C and to treat m as constant, when Paris's law da/dN = C( <DELTA> K)m is applied at each point in materials.

这项研究的目的是阐明<delta> k依赖性疲劳裂纹生长速率DA/DN的可变性，通过在常数<delta> k的条件下进行统计疲劳裂纹增长测试，并估算了DA/DA/的概率表述。 DN，其中<delta> k是应力强度范围。使用轮廓的双悬臂梁样品达到了常数<delta> k的状态。使用的材料是高强度钢HT60。在<delta> K的六个级别中测试了4至6个样本。在所有31个标本中，测试了标本。使用直流电势方法测量DA/DN。为了自动化测量和数据处理，开发了使用微型计算机的自动裂纹长度测量系统。做出了各种努力以获得高度的测量精度。为了获得在恒定<delta> k下分析实验数据的有效方法，重新列入了增加<delta> k的条件下的特权数据。分析表明，将DA/DN的变异性视为由两个组成部分组成的可变性：特异性变异性和特异性内变异性。接下来，分析了常数<delta> K下的实验数据。首先，使用方差分析方法将DA/DN的变异分解为特异性变异性和叠层内变化。已经发现，在常数<delta> k下DA/DN的变异性也由上述两个组成部分组成。然后，检查了这两个组件的<delta> k依赖性。特异性间变异性和特异性变异性都没有显示出对<delta> k的明显依赖性，因此，这两个组件都可以视为cond constnt与<delta> k无关。 da/dn的of是随机c并将m视为恒定时，当巴黎定律da/dn = c（<delta> k）m时，在材料中的每个点都应用。