大型起重机臂架结构失稳载荷分析

发布时间：2018-07-16 16:07

【摘要】：大型起重机臂架是一种重载、柔性、细长结构。该结构由于具有起重量大、吊起高度高、工作幅度多样、臂节组合灵活等优点而广泛用于高空吊装行业,是主要的承载部件。臂架结构的长度通常可以达到几十米甚至上百米。在重载情况下,结构会产生大位移,表现出几何非线性的特点,其平衡路径追踪和失稳载荷求解等问题一直以来都是分析的难点。随着现代计算技术的进步和实际需要的日新月异,使这类结构不断朝着更稀疏、更细长的方向持续优化。通常而言,结构越细长就越有可能在破坏前发生失稳。此外,由于起重机臂架起重性能分析需要考虑机构约束、多工况和自重等因素,因此迫切地需要一种高效地计算这类结构失稳载荷的方法。为了高效地求解大型起重机臂架结构的临界载荷,本文在高效建模方法和失稳载荷快速求解方法等方面进行了研究和探讨。现在的大型工业设备或者建筑结构都是很多标准部件组成的。本文提出一个大型结构的整体分析方案,把设计阶段既有的部件有限元模型作为子结构,通过直接给出不同部件在公共边界上节点位移的关系,将部件界面缝合起来用于整体分析,避免了传统方法需要构造的复杂界面单元,大幅提高了建模效率。大型起重机的臂架结构是由一系列标准臂节相继连接而成,具有周期性的特点。因此,应用本文所提的整体分析方案,可以一次性将型号相同的臂节建立成臂节单元,模型数据可以重复用于不同类型、不同长度的臂架结构分析,节省了建模时间。部件界面缝合方法也可以用于其他大型结构的有限元分析,节省了整体结构建模的工作量,拓展了子结构方法的应用。臂架自重对其稳定性分析有很大的影响。为了建立考虑重力影响的臂节单元,本文首先通过引入重力载荷影响系数矩阵,把重力离散到臂节结构的每个节点上。然后,将臂架以臂节为单位划分成多个臂节单元,在每个臂节上建立一个随结构一起运动的局部坐标系,并将交界面节点定义为边界节点。由于臂节内部节点除重力外不再受其他外力的作用,将内部节点的位移表示成局部位移和坐标系位移的组合,从而将重力做功分解成局部位移对应重力做功和坐标系位移对应重力做功两部分。在此基础上,将内部节点的局部位移由边界节点的局部位移表示,提出了考虑重力影响的臂节内部自由度减缩方法。接着,推导了臂节单元边界节点位移和边界节点力之间的关系,得到了由边界节点位移参数描述的臂节单元广义节点力表达式,并解析地给出了节点力平衡方程的切线刚度阵。本文采用共旋坐标法考虑臂架结构的几何非线性效应,并将变幅机构与臂架结构视为整体系统进行稳定性分析,推导了变幅机构施加在臂架上的非线性外力。实际工程中,需要对同一类型起重机进行多工况稳定性分析,传统的求解稳定性的增量法和各种弧长法在求解效率上难以满足要求。考虑到起重机的变化载荷只有吊重这一项,本文通过将平衡方程对载荷求导,把传统的路径跟踪问题转化为微分方程的求解问题。通过求解微分方程并结合失稳判断准则,可以快速得到臂架结构的失稳载荷。应用本文所提方法编写了大型起重机臂架结构稳定性分析软件,分别对实际工程中多种含腰绳起重机臂架结构进行了临界载荷求解。结果表明,本文所提方法能够高效地求解臂架结构的临界载荷,可以作为臂架结构起重性能分析的参考。
[Abstract]:The arm frame of a large crane is a heavy load, flexible, slender structure. This structure is widely used in high altitude hoisting industry because of its large weight, high lifting height, variety of working amplitude, flexible arm joint and so on. It is the main bearing part. The length of the arm structure can usually reach tens or even hundreds of meters. Under heavy load, the structure is loaded. With the development of the modern computing technology and the changing of the actual needs, this kind of structure continues to be thinner and more elongated. In general, the structure is finer. The longer it is, the more likely it is to lose stability before the damage. In addition, because the crane arm erect performance analysis needs to consider the mechanism constraints, multiple conditions and self weight factors, it is urgently needed to efficiently calculate the instability load of this kind of structure. In order to efficiently solve the critical load of the arm frame structure of large crane, this paper is efficient in this paper. The modeling method and the fast calculation method of unstable load are studied and discussed. The present large-scale industrial equipment or building structure is composed of many standard components. In this paper, a comprehensive analysis scheme of a large structure is proposed. The finite element model of the components of the components at the design stage is taken as the substructure and the different parts are given directly. The relationship between the displacement of the node on the common boundary, suturing the component interface to the whole analysis, avoiding the complex interface unit which the traditional method needs to construct, greatly improves the modeling efficiency. The boom structure of the large crane is connected by a series of standard arm joints, and has the periodic characteristics. Therefore, the application of this paper is proposed. As a whole, the same type of arm joint can be set up as the arm joint unit at one time. The model data can be used repeatedly for the analysis of different types and length of the arm structure, and the modeling time can be saved. The interface stitching method can also be used in the finite element analysis of other large structures, thus saving the workload of the whole structure modeling. The application of the substructure method is extended. The weight of the arm has a great influence on the stability analysis of the arm. In order to establish the arm node element with the influence of gravity, this paper first introduces gravity to each node of the arm joint by introducing the influence coefficient matrix of gravity load to each node of the arm joint structure, and then divides the arm frame into a number of arm segments with the arm segment. In each arm, a local coordinate system which moves along with the structure is established and the intersection node is defined as a boundary node. The internal node's displacement is represented by the displacement of the local node and the coordinates of the coordinate system because the internal node of the arm node is no longer affected by the other external forces. On the basis of this, the local displacement of the internal node is represented by the local displacement of the boundary node on this basis. On this basis, the internal displacement of the inner node is represented by the local displacement of the boundary node. The method of reducing the internal freedom of the arm joint with the influence of gravity is proposed. Then, the relationship between the boundary node displacement of the arm node element and the force of the boundary node is deduced, and the relationship between the boundary node displacement and the boundary node force is derived. The generalized nodal force expression of the arm node element is described by the displacement parameters of the boundary node, and the tangent stiffness matrix of the node force balance equation is analytically given. In this paper, the geometric nonlinear effect of the arm frame is considered by the co rotation coordinate method, and the stability analysis of the variable amplitude mechanism and the arm structure is considered as a whole system, and the variable amplitude mechanism is derived. The nonlinear external force applied on the arm frame. In practical engineering, it is necessary to analyze the stability of the same type of crane in multiple working conditions. The traditional incremental method for solving stability and the various arc length methods are difficult to meet the requirements of the solving efficiency. Considering that the load of the crane is only the lifting weight, the equilibrium equation is used to calculate the load. The traditional path tracking problem is transformed into the solving problem of differential equations. By solving the differential equation and combining the instability criterion, the instability load of the arm structure can be quickly obtained. The software for the stability analysis of the boom structure of a large crane is written in this paper. The critical load of the arm structure is solved. The results show that the proposed method can efficiently solve the critical load of the arm structure, and can be used as a reference for the analysis of the lifting performance of the arm frame structure.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TH21

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