边界载荷反求法分析推耙机的焊接结构疲劳  

Fatigue analysis of weld structure of rake dozer based on reverse determination of structural boundary loads

作　　者：李玉良[1] 夏坤[1] 康正生[2] 林建军[3] 曾微[3] 

机构地区：[1]浙江大学机械工程学院,杭州310027 [2]山推工程机械股份有限公司,济宁272073 [3]中国北方车辆研究所,北京100072

出　　处：《农业工程学报》2016年第4期62-68,共7页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家自然科学基金(51175457;51475416);中央高校基本科研业务费专项资金(2014QNA4003)

摘　　要：针对工程装备焊接结构模型复杂、计算数据庞大导致的疲劳寿命难以预测问题,该文将带有缺陷的局部结构体分离出来单独进行分析,采用有限元和应力解析计算方程获得测试应力(应变)和结构体边界载荷之间的关系,以便反求得到局部结构体的外载荷,进而应用降维多轴疲劳损伤模型开展局部结构体裂纹扩展寿命的研究。以存在多条焊缝的推耙机H形架横梁为对象设置初始裂纹来模拟焊接缺陷,基于测试数据确定横梁的等效边界载荷并进行疲劳寿命计算,预测得到的H形架横梁使用寿命与工程实际寿命误差在5%以内,说明该方法是切实可行的。该研究可为工程结构设计及制造精度控制提供参考。Due to the bad working conditions and the weld defects in the structure which is subject to random multiaxial loadings, the fatigue failure occurs frequently in the rake dozer. When the defects exist in the working structure, if the whole engineering structure is taken as the fatigue analysis object, not only the computation model is complex, but also the data are enormous, which will make it difficult to predict the fatigue life of structure. Therefore, it is necessary to separate the local structure where defects are located from the whole one in order to reduce the complexity of the computation model. In this way, the determination of the boundary loads of the local structure is a key to realize successful analysis of structure fatigue. For irregular and regular structures, the finite element method （FEM） and the stress analytical computation equation are respectively used to establish the relationship between the test stress （strain） and the boundary load, so that the loads can be reversely determined. For the FEM method, the cross section of structure is firstly discretized, the center of the strain gage is regarded as the location of the corresponding FEM node, and all the force components of the boundary loads are applied to the boundary nodes of the cross section, and thus the relationships between the boundary loads and the test stresses or strains can be established through the FEM equations. According to the number of unknown boundary loads, the number of three-element rectangular rosettes can be determined according to the equation. For the structure with regular cross section, the number of rosettes can be determined in the same way based on the analytical equations. Next, the strain or stress data are collected and transformed to obtain the maximum and minimum normal stresses of the test points, and the load case of the structure is determined according to the stress states derived from the maximum and minimum normal stresses. In the paper, the cross section of the beam of the machine H-shap

关 键 词：机械化 有限元法 疲劳试验 边界载荷 推耙机横梁 焊接裂纹 多轴疲劳 

分 类 号：S229.2[农业科学—农业机械化工程]