履带起重机桁架臂结构的薄弱杆件分析

Analysis of weak bars in lattice booms of a crawler crane

为确定履带起重机桁架臂结构的薄弱杆件及杆件失效模式,首次将二分法与有限元软件二次开发技术相结合,给出一种确定薄弱杆件的简单有效的方法,并对桁架臂的薄弱杆件进行分析。首先,建立桁架臂的有限元参数化模型,利用二分法思想,通过不断迭代加载来改变作用在桁架臂上的载荷大小。其次,对桁架臂进行有限元分析,并提取每次加载后所有杆件的计算结果。最后,检查每根杆件的承载状态,直至桁架臂结构中某根杆件达到临界状态,从而确定出臂架结构的薄弱杆件。通过两个算例分析表明:理论分析结果与实际试验结果一致,验证了方法的可行性和有效性;压弯杆件是桁架臂的薄弱杆件,其失效模式为压弯失稳,在校核压杆稳定性时应该考虑杆件端部弯矩的影响。本文为桁架臂薄弱杆件分析和结构局部加强设计提供一定参考。

A simple and effective method combining bisection method and secondary development technology of finite element software is proposed and applied to analyze the weak bars and their failure modes in the lattice boom of a crawler crane. Firstly, a parametric finite element model of crawler crane boom is established, and bisection method based idea is used to adjust the applied loadings on the lattice boom. Secondly, the boom structure is analyzed by finite element method, and the calculated results of all bars are obtained. Finally, the stress state of each bar is checked until one certain member reaches its critical state. Two examples are listed and the results obtained indicate that the numerical results by the proposed method match the experimental results very well, which verify the feasibility and validity of the method. It can be concluded that compressive-bending bars are the weak bars of the boom, and their corresponding failure modes are buckling. Effect of bending moment should also be considered during the compressive bar stability check process. The proposed method may offer a reference for determining the weak bars and structural local strengthen design.