起重机箱型梁疲劳裂纹与寿命预估

Fatigue cracks and life estimation for crane box girders

起重机疲劳裂纹是起重机破坏的主要形式之一,根据断裂力学与损伤力学,给出了单一裂纹的线弹性与弹塑性的应力强度因子和恒幅载荷与无级变幅载荷下的疲劳裂纹扩展公式,推导出了在无级变幅载荷下多裂纹的应力强度因子公式.运用起重机数据记录仪测得的数据,结合峰值计数法,得出起重机箱形梁的应力谱.结合实例对1台在役起重机箱型梁疲劳裂纹进行分析,实例表明,推导出的疲劳裂纹公式能够正确快捷地求出箱型梁的疲劳寿命;对特种设备检验以及减少起重机疲劳事故的发生具有重要的工程价值.

In general,crane fatigue cracking plays a critical role in crane damages.According to fracture and damage mechanics,a stress intensity factor is derived from single-crack linear elastic and elastic-plastic conditions,whereas a fatigue propagation formula is attained from constant-and stepless variable-amplitude loading constraints.Meanwhile,the stress intensity factor formula is deduced for multi-cracking under stepless variable-amplitude situation.Next,the stress spectra for crane box girders are obtained using data recorder and peak counting method.Finally,a fatigue cracking analysis on box girders is used as an example for currently-used crane.Accordingly,it is indicted that the proposed fatigue crack formula can accurately and efficiently solve the girder fatigue life.Therein,this approach signifies upon special-purpose equipment testing and crane fatigue accident reduction.