桥（门）式起重机箱形梁概率安全评定与疲劳寿命估算

发布时间：2018-05-15 06:08

本文选题：起重机 + 箱形梁　；参考：《西南交通大学》2017年硕士论文

【摘要】：起重机械作为特种设备的主要类别之一,对释放劳动力、实现自动化、提高作业效率发挥着极其巨大作用,已在人类社会生产、生活的众多领域普遍应用。起重机金属结构作为大型焊接结构,在生产、装配与使用过程中,受各种因素地影响,不可避免的会出现缺陷(如裂纹)。这些裂纹的存在给服役起重机的安全使用埋下了较大隐患。在起重机作业过程中,一旦裂纹扩展,使得结构断裂失效,将导致不可预知的事故。故从起重机服役安全的角度,对含有裂纹缺陷的起重机进行安全评估具有重要现实意义。本文针对服役起重机的安全性,以某36t门式起重机箱形梁为研究对象,参照英国标准BS7910《金属结构中缺陷验收评定方法导则》,基于线弹性断裂力学理论、可靠性理论、以及疲劳损伤理论等,采用理论分析与有限元数值模拟等技术手段,对含有裂纹缺陷的箱形梁进行了概率安全评估和疲劳寿命估算的研究。论文的主要内容包括:(1)以BS7910标准为参考,介绍了失效评定图技术以及该标准中的三个评估等级及其特点。还介绍了可靠性分析中的一些常见分布类型,以及可靠性指标求解的相关过程与常用方法。(2)利用有限元分析软件ABAQUS建立了起重机箱形梁的整体有限元模型和裂纹子模型,采用相互作用积分法分别计算了箱形梁下盖板和腹板上,不同尺寸参数下的贯穿斜裂纹以及相应简化等长裂纹尖端的应力强度因子KI。通过将KI值进行比较分析,验证了将起重机箱形梁中的实际裂纹简化成等长裂纹进行断裂分析是合理可行的。(3)基于失效评定图技术和可靠性基本理论,建立了起重机箱形梁结构概率安全评定的方法与流程;并且利用有限元分析结果和Monte Carlo随机抽样方法,对含裂纹缺陷的某36t门式起重机箱形梁结构进行了算例分析。算例分析表明该评定方法是可行的;并由参数敏感性分析得到断裂韧性,屈服强度与一次薄膜应力对箱形梁失效概率影响较大,评定时需优先考虑这些参数。(4)针对起重机箱形梁结构及其受力情况复杂的特点,提出了一种以疲劳试验数据为基础的等效裂纹法来估算疲劳寿命。通过将该方法的计算结果与文献中的试验结果数据进行对比分析,新方法对于常幅载荷作用下的疲劳寿命估算是有效可行的,但在变幅载荷作用下的疲劳寿命估算还需更深入地研究。该估算方法可为起重机的设计制造提供一定的参考。
[Abstract]:As one of the main types of special equipment, hoisting machinery plays an extremely important role in releasing labor force, realizing automation and improving work efficiency. It has been widely used in many fields of human society production and life. Crane metal structure as a large welded structure, in the production, assembly and use of the process, affected by a variety of factors, the inevitable defects (such as cracks). The existence of these cracks buries a great hidden danger for the safe use of the crane in service. In the process of crane operation, once the crack expands, the structure will break and fail, which will lead to unpredictable accidents. Therefore, from the point of view of crane service safety, it is of great practical significance to evaluate the safety of cranes with crack defects. Aiming at the safety of the crane in service, taking the box girder of a 36t portal crane as the research object, referring to the British standard BS7910 "guidelines for the acceptance and Evaluation of defects in Metal structures", based on the theory of linear elastic fracture mechanics and reliability theory, Based on the theory of fatigue damage, the probabilistic safety assessment and fatigue life estimation of box beams with crack defects are studied by means of theoretical analysis and finite element numerical simulation. The main contents of this paper are as follows: (1) taking the BS7910 standard as the reference, the paper introduces the failure assessment chart technology, three evaluation grades and their characteristics in this standard. This paper also introduces some common distribution types in reliability analysis, as well as the related process and common methods of reliability index solving.) by using finite element analysis software ABAQUS, the integral finite element model and crack sub-model of crane box-beam are established. The stress intensity factors (Ki) at the bottom cover plate and web plate of box beam with different parameters are calculated by the interaction integration method. The stress intensity factors (Ki) at the tip of the oblique crack and the corresponding simplification of the tip of the equal-length crack are simplified. By comparing and analyzing the KI value, it is proved that it is reasonable and feasible to simplify the actual crack in the box girder of crane to equal length crack for fracture analysis. The method and flow of probabilistic safety assessment of crane box-girder structure are established, and a case study of a 36t portal crane box girder structure with crack defects is carried out by using the results of finite element analysis and Monte Carlo random sampling method. The example analysis shows that the method is feasible, and the fracture toughness is obtained by parameter sensitivity analysis, and the yield strength and the first film stress have great influence on the failure probability of box beam. These parameters should be considered first. (4) in view of the complexity of crane box-beam structure and its mechanical condition, an equivalent crack method based on fatigue test data is proposed to estimate fatigue life. By comparing the calculated results with the experimental data in literature, the new method is effective and feasible for fatigue life estimation under constant amplitude loading. However, the estimation of fatigue life under variable amplitude loads needs to be further studied. This method can provide a certain reference for the design and manufacture of crane.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH21

【参考文献】