起重机桁架臂疲劳裂纹形成寿命影响因素分析

INFLUENCING FACTOR ANALYSIS OF FATIGUE CRACK INITIATION LIFE ON CRANE LATTICE BOOM

起重机桁架臂结构复杂、载荷多样,由于焊接质量或应力集中的影响,臂架部分危险区域处于弹塑性变形阶段,采用应变参数进行分析是比较合理的。以起重机桁架臂疲劳裂纹形成阶段为研究区间,应用局部应力应变法,结合修正Neuber法,建立起重机疲劳裂纹形成寿命算法模型,并对影响疲劳裂纹形成寿命的三个主要因素进行了分析对比,并进行了起重机K型节点疲劳寿命试验。当材料一定的情况下,应力集中系数对疲劳裂纹的形成寿命影响最大,其次是平均应力。针对影响因素大小,提出了桁架臂空间结构优化建议和工艺处理改善措施。

The crane lattice boom is complex and the load is diversity, part of the structure may suffer plastic deformation because of the high stress concentration or poor weld quality under exceptional poor load conditions. So using strain analysis parameter is reasonable compared to stress parameter. The paper was focused on the fatigue crack initiation stage of crane lattice boom. The method of local stress strain was used combined with the correction Neuber method. A crane fatigue crack initiation life evaluation algorithm model was built. According to the model, three main factors which will influence the initiation life calculation were analyzed and compared. Fatigue tests were also carried out with K nodes of crane lattice boom. When the material was determined under certain circumstances, the stress concentration factor had the most impact result on the life. The mean stress on the material had the less impact but it cannot be ignored. According to the Factors, optimization suggestions to lattice boom spatial structure and work process improvement measures were proposed.