桥式起重机箱形主梁结构疲劳寿命研究

发布时间：2018-09-06 19:54

【摘要】：桥式起重机作为现代工业生产与起重运输业中必不可少的特种设备之一,目前已广泛应用于在铁路交通、钢铁化工、港口码头以及物流周转等部门和场所。然而,桥式起重机却是大型机械设备中隐藏危险因素最多、发生伤亡事故几率最大的特种设备,国内外每年不断频发的起重设备事故,造成了极其严重的人身伤害及财产损失。根据大量统计资料显示,这些事故中,最常见、最严重的是以疲劳裂纹为特征的桥式起重机焊接箱形主梁结构的疲劳破坏。桥式起重机的箱形主梁结构是其主要的承载构件,桥式起重机的工作特点决定了此类结构的主要破坏形式为随机载荷作用下主梁的疲劳断裂,而主梁的断裂就意味着整个桥式起重机寿命的终结。因此,进行在役桥式起重机箱形主梁结构的疲劳裂纹扩展规律的研究和箱形主梁剩余疲劳寿命的预测,可以预防其疲劳断裂破坏事故的发生,并对于桥式起重机的设计、制造、使用及维修具有重要的指导意义。本课题运用现代疲劳累积损伤理论,分析桥式起重机箱形主梁疲劳破坏的特征及其影响因素;采用ANSYS有限元分析软件对桥式起重机箱形主梁结构进行静力学分析,确定其危险部位并对其进行疲劳分析与剩余寿命估算。另外,本课题还结合断裂力学理论对已产生疲劳裂纹的箱形主梁结构进行剩余疲劳寿命预测,这对于提高桥式起重机工作的可靠性,延长其使用寿命,进而提高起重机在工程实际中的生产效率具有重要意义。首先,本文建立了该桥式起重机箱形主梁结构的有限元模型,选择起重机的五种典型工况,在近似于实际工作条件的疲劳载荷分布状态下对无缺陷的箱形主梁结构进行有限元模拟分析,得到了箱形主梁结构在每种工况下的应力、位移变形以及安全系数分布图,确定了箱形主梁结构应力值与位移变形量的最大位置和安全系数最低的部位。其次,采用ANSYS有限元分析软件中的寿命分析模块对含有初始裂纹的桥式起重机主梁结构的设计寿命进行估算,并通过模拟结果分析,得出含有初始裂纹的箱形主梁结构在近似实际工况下的安全系数分布图以及疲劳寿命云图,直观地反映出了箱形主梁结构各部位的疲劳寿命分布状态。最后,本课题采用线弹性断裂力学的方法,估算了该桥式起重机端梁危险部位的疲劳扩展寿命和箱形主梁结构的剩余寿命,并绘制出了箱形主梁结构端部腹板处疲劳裂纹长度与该起重机循环次数的关系曲线图。再把有限元模拟的分析结果与实测结果相比对,发现两者是基本吻合的,证明了该种箱形主梁结构疲劳寿命估算方法的可行性。
[Abstract]:Bridge crane, as one of the necessary special equipments in modern industrial production and lifting transportation, has been widely used in railway transportation, iron and steel chemical industry, port and wharf, logistics and other departments and places. However, bridge crane is the special equipment with the most hidden risk factors and the greatest chance of casualties in large mechanical equipment. The frequent crane accidents at home and abroad cause extremely serious personal injury and property losses. According to a large number of statistical data, the most common and serious of these accidents is the fatigue failure of welded box girder structure of bridge crane, which is characterized by fatigue cracks. The box girder structure of bridge crane is its main bearing member. The main failure form of bridge crane is fatigue fracture of main beam under random load. The rupture of the main beam means the end of the life of the bridge crane. Therefore, the study of fatigue crack propagation law and the prediction of residual fatigue life of box girder of bridge crane in service can prevent the occurrence of fatigue fracture failure accident, and for the design and manufacture of bridge crane, the fatigue crack propagation law of the box girder structure and the prediction of the residual fatigue life of the box main girder can be prevented. Use and maintenance have important guiding significance. Based on the modern fatigue cumulative damage theory, this paper analyzes the fatigue failure characteristics and influencing factors of box girder of bridge crane, and uses ANSYS finite element analysis software to analyze the structure of box girder of bridge crane. The dangerous site is determined and fatigue analysis and residual life estimation are carried out. In addition, combined with the theory of fracture mechanics, the residual fatigue life of box girder structure with fatigue cracks is predicted, which can improve the reliability of bridge crane and prolong its service life. It is of great significance to improve the production efficiency of crane in engineering practice. Firstly, the finite element model of the box girder structure of the bridge crane is established, and five typical working conditions of the crane are selected. In the condition of fatigue load distribution similar to the actual working conditions, the finite element simulation analysis of the box girder structure without defects is carried out, and the stress, displacement deformation and safety factor distribution of the box girder structure under each working condition are obtained. The maximum position of stress value and displacement and deformation of box girder structure and the position with lowest safety factor are determined. Secondly, the life analysis module of ANSYS finite element analysis software is used to estimate the design life of the bridge crane girder structure with initial cracks, and the simulation results are analyzed. The distribution of safety factor and fatigue life of box girder structure with initial cracks are obtained under the approximate actual working conditions. The distribution of fatigue life in various parts of box girder structure is directly reflected. Finally, using the method of linear elastic fracture mechanics, the fatigue propagation life of the end beam of the bridge crane and the residual life of the box girder structure are estimated. The relationship between the fatigue crack length at the end web of the box girder structure and the cycle times of the crane is plotted. By comparing the results of finite element simulation with the measured results, it is found that the two are in good agreement with each other, which proves the feasibility of the fatigue life estimation method of the box girder structure.
【学位授予单位】：太原科技大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH215

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