中文摘要：

基于模态理论对振动筛横梁进行了位移和应变模态分析，结果表明横粱损伤前、后同阶模态频率的相对偏差较小，位移模态振型亦无明显突变，而应变模态振型在横梁损伤后产生了突变峰值。据此构建了应变模态变化率作为横梁损伤诊断指标，分析结果表明应变模态变化率随横梁损伤程度的增加而增大，然后用最小二乘法拟合了二者的对应关系。由横梁的损伤程度可确定横梁初始疲劳裂纹尺寸，进而可由Paris公式预测振动筛横梁的疲劳裂纹扩展剩余寿命。应变模态变化率作为损伤诊断指标具有敏感、可靠的优点，可以较好地确定横梁损伤位置和损伤程度。对振动筛横梁的裂纹扩展剩余寿命的预测，可为横梁的预报维修提供参考，以保证振动筛的安全可靠运行。

英文摘要：

The displacement and strain modal analysis of vibrating screen beam is studied, the results show that the modal frequency relative deviation between intact and damaged beam is minor, the displacement mode shapes have no obvious mutation, but the strain mode shapes have mutation peaks for the damaged beam. Thus a damage indicator is defined by using the strain modal variable ratio before and after damage, the strain modal variable ratio increases with the increase of damage degree, the strain modal variable ratio is obtained by the least squares fitting method of the strain modes. The initial fatigue crack size is determined by damage degree of the beam, then the residual life of fatigue crack growth of the beam is predicted by the Paris formula. The analysis results show that the strain modal variable ratio is a sensitive and reliable damage indicator for indicating the damage location and damage degree. The prediction of the crack propagation residual life can provide reference for maintenance forecast of the vibrating screen beam, which can ensure safe and reliable operation of the vibrating screen.