含缺陷起重机箱形梁结构的弹塑性断裂参数模拟及安全评定

发布时间：2018-01-29 02:15

本文关键词： 起重机箱梁结构弹塑性安全评定 J积分扩展有限元法　出处：《西南交通大学》2016年硕士论文　论文类型：学位论文

【摘要】：起重机作为物料的搬运和装卸的机械产品,其需求量日益增加。但其为人类带来物质财富的同时,也带来了潜在的风险,因结构断裂而造成的安全事故就是其风险之一。服役起重机数量不断增加,特别是老龄及超龄服役的起重机数量逐渐增大,潜在的安全风险也在增加,安全生产形势愈发严峻,迫使人们关注起重机服役期间的性能状态,特别是安全状态,起重机安全评定变得越来越紧迫和重要。本文以起重机箱梁结构为研究对象,从起重机箱形梁结构的弹塑性断裂控制参数的计算和裂纹扩展等方面展开研究,探讨适合于起重机结构的弹塑性断裂控制关键参数J积分的计算方法,以及基于弹塑性断裂的裂纹稳态扩展的条件,初步建立适用于桥(门)式起重机结构安全评定的弹塑性断裂评定流程和以及关键控制参数的有限元模拟方法。论文的主要内容包括：(1)起重机箱形梁结构的破坏特征与工程处理方法。归纳总结服役箱形梁结构的裂纹缺陷种类和扩展机理等规律；并结合桥(门)式起重机金属结构的工作背景,总结出焊接箱形梁结构的性能特点、存在的问题及其缺陷尺寸参数的工程表征规则。(2)对36t起重机箱形梁结构进行静力学分析,计算其所受到的外加载荷,并通过有限元软件对整机做静力学仿真,得出整机的强度和刚度及应力分布情况；给出二维平板J积分的数值计算方法,并举实例说明；在箱形梁结构静力学分析的基础上,加入裂纹,采用有限元软件ABAQUS对其仿真模拟,计算裂纹尖端的J积分值；推导按J控制裂纹扩展的失效曲线FAC；基于屈服原理运用软件直接求解箱梁上穿透裂纹的极限载荷,并得到穿透裂纹板的载荷比Sr的计算式；在已知仿真模拟得到裂纹尖端J积分值以及失效评定图和Sr的计算式的基础上,对含裂纹结构进行安全评定。(3)结合断裂准则,利用扩展有限元法XFEM对裂纹扩展进行模拟；给出用ABAQUS软件对含裂纹的箱形梁结构进行扩展有限元分析的具体流程,得到含裂纹结构的断裂参数以及裂纹单元的扩展方向及状态。
[Abstract]:Crane as a mechanical product of material handling and loading and unloading, its demand is increasing day by day, but it brings material wealth to human beings, but also brings potential risks. The number of service cranes is increasing, especially the number of aged and overage cranes is gradually increasing, and the potential safety risks are also increasing. The situation of safety production is becoming more and more serious, forcing people to pay attention to the performance state of crane during service, especially the safety state. Crane safety assessment becomes more and more urgent and important. This paper takes the crane box girder structure as the research object, from the crane box girder structure elastic-plastic fracture control parameters calculation and crack growth. This paper discusses the calculation method of J-integral, the key parameter of elastic-plastic fracture control for crane structure, and the condition of crack steady state growth based on elastic-plastic fracture. An elastic-plastic fracture assessment process and a finite element simulation method for key control parameters of bridge (gantry) crane structure safety assessment are established. The main contents of this paper are as follows: 1). The failure characteristics and engineering treatment methods of box girder structure of crane are summarized and the types of crack defects and propagation mechanism of box beam structure in service are summarized. Combined with the working background of the metal structure of the bridge (portal) crane, the performance characteristics of the welded box beam structure are summarized. The existing problems and the engineering characterization rules of the defect size parameters are used to analyze the box-beam structure of 36t crane and calculate its external load. The strength, stiffness and stress distribution of the whole machine are obtained by the static simulation of the whole machine with finite element software. The numerical calculation method of 2-D plate J-integral is given, and an example is given to illustrate it. On the basis of static analysis of box beam structure, the crack is added, and the J-integral value of crack tip is calculated by using finite element software ABAQUS to simulate it. The failure curve FACwhich is controlled by J is derived. Based on the yield principle, the limit load of penetrating crack on box girder is directly solved by software, and the formula of load ratio Sr of the plate with penetrating crack is obtained. On the basis of known simulation results of crack tip J integral, failure assessment diagram and Sr formula, the crack containing structure is evaluated by safety assessment. 3) combined with fracture criterion. The propagation finite element method (XFEM) is used to simulate the crack growth. The concrete flow of finite element analysis of cracked box-beam structures is given by using ABAQUS software. The fracture parameters of cracked structures and the propagation direction and state of crack elements are obtained.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TH21

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