受弯梁中开裂纹的位置识别与分析

利用有限元计算判定受弯梁中开裂纹的位置 ,从中得出 :同正常梁相比 ,裂纹梁的固有频率与振型的变化不但与裂纹深度而且与裂纹位置有关 ,因而 ,通过裂纹梁低阶固有频率及振型的变化情况可以判定裂纹的位置。对于裂纹较浅的情况 ,直接利用振型与固有频率的变化很难判定裂纹的位置 ,必须借用一些特征参数来提高识别的敏感性 ,这样 ,裂纹梁中早期裂纹的识别也是可行的

On Identification of Open-Cracks in Bending Beam

Unknown cracks in mechanical systems will lead to catastrophic results. The vibration characteristics of a cracked beam are investigated in this paper. The differences of natural frequencies and modes between normal and cracked beam are obtained by using FEM method. The results show that both location and depth of the cracks will affect the natural frequencies and the modes. So, the change of the natural frequencies and the modes can be used to detect locations of the cracks. The sharp change in the first order mode can indicate the location of the deep crack. However, because noise exists, it is difficult to detect the cracks when the crack is shallow. The proper characteristic parameter is imperative to improve the results. The change of the stiffness matrix can be obtained from several low order natural frequencies and modes of the normal and cracked beam. This method is also useful for multi crack shaft when the cracks can be separated by element dividing in FEM.