焊接结构疲劳寿命预测相关问题研究
发布时间：2019-06-10 09:48
【摘要】：焊接结构在机械工程、车辆船舶、海洋工程、石油化工等领域应用广泛,其中一些重要结构件在工作中承受复杂随机载荷,疲劳破坏是其主要失效形式之一。应用概率统计理论与方法,研究结构疲劳寿命的概率属性,更加客观、真实地预测结构疲劳寿命和可靠性,有重要工程应用价值。本论文以焊接结构疲劳概率寿命预测为背景,主要研究内容如下：(1)针对高铁车体焊接结构件进行实验室条件下的疲劳寿命测试及应力分析。根据车体结构特点,设计了两组(每组两种)疲劳寿命测试对比试样。对每组试验,分别采用相对简单的轴向拉伸加载试样和较复杂的弯曲加载试样及相应的疲劳试验方法,获得两种不同形式的试件在不同加载方式下的疲劳试验数据。同时,应用有限元方法建立对应于两种加载方式的结构试件的静力学模型,计算出各自危险点的应力。通过对比两种结构试件的试验寿命数据、断裂位置以及有限元仿真得出的应力分布情况,探讨了利用简单的拉伸疲劳试验来代替复杂的弯曲疲劳试验的可行性。此外,还分析了平均应力影响及修正问题。(2)分析、比较不同的疲劳试验数据信息提取方法与效果。基于试验数据,利用概率统计分析方法,对忽略截尾数据的寿命数据进行统计分析,拟合出寿命数据的分布类型和P-S-N曲线；应用极大似然法和K-S检验法,对含截尾数据的寿命数据进行参数估计。对两种处理结果的分析、比较表明,针对不同类型的试验数据,应充分考虑截尾数据的影响,选择合理的处理方法,截尾数据通常不应忽略。由此可见,传统疲劳寿命试验数据处理过程中,简单忽略截尾数据(包括寿命溢出数据和非标距段断裂的试样的寿命数据)的做法,会在不同程度上低估试验对象的疲劳性能。(3)以液压支架(大型焊接结构)为背景,利用有限元软件计算液压支架整架在不同工况下的应力分布,同时通过实际结构测试获得相应工况测试点的真实应力值,有限元分析与实测结果相互印证,确定了支架的危险部位；利用液压支架与采场围岩的相互作用机理,详细研究液压支架在井下工程过程中的载荷历程,通过Monte Carlo数值仿真方法,编制出了能反映载荷复杂性与随机性特征的载荷谱,进而应用局部应力应变法和Miner累积损伤理论对液压支架的使用寿命进行预测。(4)对液压支架结构进行可靠性评估。从“宏观”和“微观”两个层面描述复杂随机载荷历程及其概率特性。应用损伤等效机理,将变幅循环载荷等效成具有当量应力幅值的恒幅循环载荷。在此基础上,基于全概率计算原理和统计平均算法建立液压支架零部件(多部位损伤结构,相当于一个串联系统)的疲劳可靠性模型,该模型能客观、真实地反映各损伤部位之间的失效相关性。
[Abstract]:Welded structures are widely used in mechanical engineering, vehicle ships, marine engineering, petrochemical and other fields. Some of the important structural parts bear complex random loads in their work, and fatigue failure is one of the main failure forms. It is of great engineering application value to study the probability attribute of structural fatigue life by using probability statistical theory and method to predict the fatigue life and reliability of structure more objectively and truly. In this paper, based on the fatigue probability life prediction of welded structures, the main research contents are as follows: (1) the fatigue life test and stress analysis of high-speed railway car body welded structures under laboratory conditions are carried out. According to the structural characteristics of the car body, two groups (two kinds of each group) fatigue life test and comparison samples were designed. For each group of tests, the fatigue test data of two different forms of specimens under different loading modes were obtained by using relatively simple axial tensile loading specimens, more complex bending loading specimens and corresponding fatigue test methods. At the same time, the static model of the structural specimen corresponding to the two loading modes is established by using the finite element method, and the stress of each dangerous point is calculated. By comparing the test life data, fracture position and stress distribution of the two kinds of structural specimens, the feasibility of using simple tensile fatigue test instead of complex bending fatigue test is discussed. In addition, the influence of average stress and its correction are analyzed. (2) different methods and effects of fatigue test data extraction are compared. Based on the test data, the life data which ignore the truncated data are statistically analyzed by using the probability statistical analysis method, and the distribution types and P-S-N curves of the life data are fitted. The maximum likelihood method and K 鈮，
本文编号：2496373
[Abstract]:Welded structures are widely used in mechanical engineering, vehicle ships, marine engineering, petrochemical and other fields. Some of the important structural parts bear complex random loads in their work, and fatigue failure is one of the main failure forms. It is of great engineering application value to study the probability attribute of structural fatigue life by using probability statistical theory and method to predict the fatigue life and reliability of structure more objectively and truly. In this paper, based on the fatigue probability life prediction of welded structures, the main research contents are as follows: (1) the fatigue life test and stress analysis of high-speed railway car body welded structures under laboratory conditions are carried out. According to the structural characteristics of the car body, two groups (two kinds of each group) fatigue life test and comparison samples were designed. For each group of tests, the fatigue test data of two different forms of specimens under different loading modes were obtained by using relatively simple axial tensile loading specimens, more complex bending loading specimens and corresponding fatigue test methods. At the same time, the static model of the structural specimen corresponding to the two loading modes is established by using the finite element method, and the stress of each dangerous point is calculated. By comparing the test life data, fracture position and stress distribution of the two kinds of structural specimens, the feasibility of using simple tensile fatigue test instead of complex bending fatigue test is discussed. In addition, the influence of average stress and its correction are analyzed. (2) different methods and effects of fatigue test data extraction are compared. Based on the test data, the life data which ignore the truncated data are statistically analyzed by using the probability statistical analysis method, and the distribution types and P-S-N curves of the life data are fitted. The maximum likelihood method and K 鈮，
本文编号：2496373
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