桥式起重机结构裂纹扩展路径模拟方法研究

Simulated model for tracing the crack propagation path of the welding structures in the overhead-operating crane

桥式起重机焊接结构普遍存在"初始裂纹"和"应力集中",裂纹的扩展和转移以及断裂规律对结构的安全可靠性评价至关重要。以断裂力学和损伤累积为基础,在有限元划分网格中"最薄弱"单元出现裂纹类缺陷,"最薄弱"单元退出工作,载荷重新分布。在重复变化载荷持续作用下,裂纹逐渐扩展,由于相邻单元的连续性,内力传递至"次薄弱"单元,使其成为下一个"最薄弱"单元。依此类推,最终结构材料达到许用应力值,裂纹达到临界值,从而形成裂纹扩展的路径。对ANSYS软件的"单元生死技术"功能进行扩展,采用Visual C++6.0集成开发环境MFC,集成了Pro/E二次开发语言Pro/Toolkit和ANSYS二次开发语言APDL,开发了桥式起重机桥架结构人机交互参数化建模及有限元分析可视化软件。通过软件模拟计算得到桥式起重机焊接箱形主梁的裂纹扩展路径,有限元分析结果与桥式起重机的实际情况相吻合。

The present paper is concerned about our research work of developing a simulated model for tracing the crack propagation path of the welding structure in the overhead-operating crane. As we know, ＂initial crack＂ and ＂stress concentration ＂ are very common in such cranes, which makes it of extreme importance to study such crack phenomena. In similar way, continuous and repeated heavy workload tends to accelerate the transfer of the internal stress to the ＂secondary weak＂ element if the continuity of the weakening of the adjacent elements or cause plastic deformation of the adjacent sections. When the crack goes on expanding by the repeated variable loads, the structure would finally come to the admissible stress value and los of its regular working performance. If the situation remains unchanged, the initial working function would lose and then leads to the eventual crack down. To solve such serious problems, we have integrated a seeondary development language Pro / Toolkit in the Pro/E software and secondary development language APDL in the ANSYS software by using the ＂element birth and death＂ technique of ANSYS software and development environment MFC of Visual C ＋ ＋ 6.0, so as to develop a model of crane bridge structure interaction parameters and a visualization software for finite element analysis. Based on the secondary development of ANSYS analysis system, we can import the Pro / E parameters of the model direetly with the method. Through complex command stream embedded Visual C ＋ ＋ integrated development environment MFC, the crane users can easily analyze the bridge structure through the finite element to improve the efficiency. After the analysis and calculation, it would be possible to determine the crack failure elements under load. Referring to the element life and death technology, it would be possible to assign the stress of structure to other similar elements. Furthermore, the software developed by us can work out the crack propagation path of welding structure of the crane, and the results of finite element analysis prove to be consistent with the actual simulation.