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类型 基础研究 预答辩日期 2018-03-20
开始(开题)日期 2016-05-12 论文结束日期 2018-01-15
地点 机械楼327 论文选题来源 973、863项目     论文字数 7.2 (万字)
题目 基于多因素修正的结构件疲劳寿命预测与可靠性评估方法研究及应用
主题词 多因素修正,疲劳寿命,裂纹扩展,可靠性,贝叶斯理论
摘要 工程机械作为现代工业中的重要设备之一,由于其工作强度大、使用频率高,微小的故障可能带来巨大的危害。另一方面,工程机械结构件的可靠性直接关系到使用企业的经济效益。若不考虑其健康状态,而直接根据使用年限采取一刀切地停用措施将会造成巨大的资源浪费。同时,机械构件的损伤起源于材料缺陷、局部应力集中等多因素,经历着从微观萌生到宏观扩展,从空洞成型到长大,从未知到可观的物理演化规律,其影响因素既跨越时间与空间,也包括已知与未知,这些多尺度因素的复合作用会多层次影响评估结果的准确性。因此,结构件的疲劳寿命预测与可靠性评估需要考虑的情况复杂,然而又是现代工程实际中不得不面对的现实问题。 本论文针对目前在结构件疲劳寿命预测与可靠性评估中所存在的一些难题,结合多因素修正疲劳现象学理论对裂纹萌生阶段疲劳寿命预测方法及裂纹扩展机理模型进行研究。并在此基础上,运用贝叶斯理论将理论结果与试验数据进行信息融合,以期为结构件可靠性的准确评估提供一些新的方法和思路。论文主要工作如下: (1)以疲劳寿命的影响因素为研究核心,并在此基础上通过将量化后的修正因子与疲劳现象学模型相结合来提出了一种基于多因素修正的疲劳寿命预测模型,实现了结构因素、应力比及质量加工方式等要素与疲劳寿命预测结果之间的定量表达,进一步完善了裂纹萌生阶段疲劳寿命预测的相关方法;同时,通过实例研究对基于多因素修正的疲劳寿命预测算法的可行性和分析准确性进行了验证,并分析了修正因子对疲劳寿命的敏感度及其变化趋势;分析结果表明实例预测值与试验结果吻合; (2)通过提取载荷历程与影响裂纹扩展矢量特征间的参数来对裂纹扩展信息进行修正,提出了一种考虑结构因素、应力比、质量加工及载荷间相互作用等要素的裂纹扩展预测模型,解决了恒值载荷与随机载荷这两种载荷历程下的裂纹扩展精确预测;结合实例,对裂纹扩展信息进行了求解,并应用声发射设备进行了监测试验研究,结果表明预测出的数据精度是符合要求的;运用建立的预测模型对修正因素与裂纹扩展长度间的影响趋势关系进行了分析研究,结果表明裂纹扩展长度与加载方式因子及表面质量因子成反比例关系; (3)从微观缺陷衍生的角度出发,通过将损伤扩展理论与残余应力重分布计算方法相结合,提出了一种伴随裂纹或损伤扩展的残余应力重分布动力学模型,并在此基础上通过引入相应的裂纹扩展增量判据来提出了一种考虑残余应力重分布的裂纹扩展规律研究方法;实例分析结果表明,残余拉应力的释放使得裂纹扩展速率下降,不考虑残余应力重分布的结果将过高估计构件的裂纹扩展速率,其预测结果偏于保守; (4)针对结构件可靠性预测过程中数据广泛存在的指数型分布和威布尔型分布,通过贝叶斯理论方法将理论预测模型与试验数据进行结合,建立了基于贝叶斯理论的可靠性评估方法,实现了结构件裂纹扩展过程中的可靠性评估,进一步完善了贝叶斯理论背景下先验信息与试验数据间的信息融合策略;通过采用MCMC算法对后验信息的计算问题进行了解决,确定了结构件的可靠度数值;评估结果表明后验参数的分布较为集中,且置信度区间可达到90%,评估精度是可以保证的; (5)针对同种结构件不同初始损伤状态下的可靠性评估问题,通过将可靠性序化模型策略与贝叶斯理论方法相结合,提出了一种基于贝叶斯理论非齐次泊松过程的不同裂纹初始状态下结构件可靠性评估模型;通过数据间递进因子的合理使用,实现了试验数据与过程参数间的有效融合;通过实例分析对结合现场试验信息下不同裂纹初始状态的构件可靠性进行了评估,结果表明其平均预测精度为92%。
英文题目 Study of the approach and its application for structural fatigue life prediction and reliability assessment based on multi-factor correction
英文主题词 Multi-factor correction; Fatigue life; Crack propagation; Reliability; Bayesian theory;
英文摘要 Engineering machinery is one of the most important equipment in modern industry, and its small fault may bring great harm to the society, due to the large working strength and frequency. On the other hand, the enterprise economic benefit is directly related to the safety and stability operation of the engineering machinery. It will cause a great waste of resources, if all the equipment are deactivated according to a fixed number of years, without considering the health status of engineering equipment. At the same time, the structural damage originates from the material defect, the local stress concentration and other factors. The structural damage process experiencing from microscopic initiation to expansion, forming from the hole to the empty, and experiencing from unknown to considerable physical evolution. The influence factors of the structural damage across the time and space, and also including known and unknown. The composite effect of these multiple level factors will affect the accuracy of prediction results. Therefore, the fatigue life prediction and reliability assessment for the engineering machinery structure need to be considered as a complex problem, which is also need to be solved in the modern engineering practice. In this paper, aiming to solve the problem existed in the current fatigue life prediction and reliability assessment for structure, the prediction approach for fatigue life in the crack initiation phase and the prediction approach for crack propagation are studied based on the theory of multiple factors correction for fatigue phenomenology. And the Bayesian theory is used to fuse the prediction result with the test data, in order to provide a new approach for the accurate assessment of structural reliability. The main work of this paper can be shown as follows: (1)The influence factors of fatigue life are selected as the core of research, and based on which a new prediction approach for fatigue life is proposed by combine the quantitative correction factors with the fatigue phenomenological model. And the quantitative expression between structure factor, stress ratio, processing approach and the fatigue life is achieved, which further provide a relevant approach for the prediction of structural crack initiation life. At the same time, the feasibility and the accuracy of proposed approach are verified by the case study. And the sensitivity of correction factors to the fatigue life and its change tendency are analyzed. It can be found from the results that the proposed prediction approach is feasible for the prediction of structural fatigue life, and the prediction result is consistent with the test result. (2)An prediction approach for crack propagation is proposed by correction with the extracting parameters from loading process and the vector feature of crack propagation, which also considerate the structural factors, stress ratio, the quality of processing and the interaction of loading. The proposed approach can be used for the prediction of crack propagation under constant load and random load. The crack propagation of case studies are predicted, and the acoustic emission equipment is applied for the monitoring experiment research. It can be clearly found from the results that the prediction accuracy of proposed model based on multiple factors correction can be guaranteed. Also the relationship between the correction factors and the crack length is analyzed by the proposed approach. It can be shown from the results that the crack propagation length is inversely proportional to the loading factor and the surface quality factor. (3)A dynamic model of residual stress redistribution with cracks or damage extending is proposed by combine the damage theory with the calculation method of residual stress redistribution, from the perspective of micro defects derived. And an analysis approach for crack propagation with consideration of the residual stress is proposed, by using the increment selection criterion. It can be clearly found from the results that the release of residual tensile stress will decline the crack propagation rate. The neglecting of the change in residual stress distribution will overestimate the crack propagation rate, and to achieve a more conservative result. (4) In view of the exponential distribution and Weibull distribution widely exists in the data of structural reliability assessment, the assessment approach for reliability is established by using the Bayesian theory to combine the theoretical prediction model with the test data. The proposed approach implements the component reliability in the process of crack propagation, and further effectively improves the information fusion strategy between the priori information and the test data. The posterior information is solved by using the MCMC algorithm, and the structural reliability value is calculated. It can be clearly found from the results that the distribution of posterior parameter is concentrated, and the confidence is 90%. So the evaluation accuracy of proposed approach can be guaranteed. (5) Aiming to solve the reliability assessment for same structure under different initial damage status, a kind of reliability evaluation model under different initial state is proposed by combine the strategy of reliability ordering model with the Bayesian theory. The effective integration between the process parameter and test data is achieved by using the progressive factors between different data. The structural reliability under different crack initial states are accessed by the test information of case studies. It can be clearly found from the results that the average prediction accuracy is 92%.
学术讨论
主办单位时间地点报告人报告主题
东南大学机械故障诊断实验室 2014.09 机械楼439 朱林 基于多因素修正的疲劳寿命预测算法
东南大学机械故障诊断实验室 2014.10 机械楼439 赵君爱 基于多尺度的全局及局部特征提取的目标识别算法的研究
东南大学机械故障诊断实验室 2014.12 机械楼439 赵转哲 混合蛙跳算法的收敛性证明
东南大学机械故障诊断实验室 2015.01 机械楼439 朱林 裂纹扩展预测方法研究及其试验验证
东南大学机械故障诊断实验室 2015.04 机械楼439 赵转哲 连续型混合蛙跳算法改进及其应用
东南大学机械故障诊断实验室 2015.06 机械楼439 赵君爱 基于改进数据场和模糊C均值聚类的微小目标分割算法的研究
东南大学机械故障诊断实验室 2015.10 机械楼439 朱林 考虑残余应力重分布的裂纹扩展机理研究
东南大学机械故障诊断实验室 2016.03 机械楼439 张菀 一种自适应Morlet小波滤波方法及其在滚动轴承早期故障诊断中的应用
东南大学机械故障诊断实验室 2016.06 机械楼439 朱林 基于贝叶斯理论的结构件可靠性评估方法
     
学术会议
会议名称时间地点本人报告本人报告题目
2016 International Conference on Measuring Technology and Mechatronics 2016.03. 08-2016.03. 11 澳门 Estimation study of stress concentration factor of crack structure based on BP neural network
东南大学机械学院学科动态报告会 2017.10.19 南京 基于多因素修正疲劳现象学理论的结构件可靠性评估方法研究
第十二届全国振动理论及应用学术会议 2017.10. 21-2017.10.23 南宁 基于贝叶斯理论非齐次泊松过程的结构件可靠性评估方法研究
东南大学机械学院学科动态报告会 2015.10.11 南京
     
代表作
论文名称
Estimation study of structure crack propagation under random load based on multiple factors correcti
A new approach for the influence of residual stress on fatigue crack propagation
考虑残余应力重分布情况下的裂纹扩展预测研究
基于多因素修正的结构件疲劳寿命预估方法
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
郭宇 正高 教授 博导 南京航天航空大学
冯月贵 正高 教授级高工 硕导 南京特种设备安全监督检验研究院
汪惠芬 正高 教授 博导 南京理工大学
李舒宏 正高 教授 博导 东南大学
许飞云 正高 教授 博导 东南大学
      
答辩秘书信息
姓名职称工作单位备注
胡建中 副高 副教授 东南大学