移动载荷作用下简支梁的动态响应及裂纹损伤识别研究

Dynamic response and crack detection of simply supported beam under moving loads

基于小波多分辨率分析的方法,根据移动载荷作用下简支梁动态响应特性,利用梁上一点振动信号对裂纹梁进行损伤识别。移动载荷经过梁上裂纹处时,必然导致梁响应时间历程曲线的奇异性,这种奇异性不能直接被观察到,但是可以通过小波多分辨率分析进行识别。利用有限元Ansys软件的瞬态分析方法进行裂纹梁移动载荷作用下的损伤识别数值模拟,通过梁上某一点挠度、速度和加速度的振动信号,利用小波多分辨率分析有效地识别出单个及多个裂纹,同时扩展到多个同向和相向移动载荷作用下裂纹梁的损伤识别。最后,通过不同小波函数的分析结果比较,寻找更加有效的小波函数。以上的损伤识别方法均在较低的移动载荷速度作用下有效,随着速度的增加,裂纹梁损伤识别的有效性越差。

The potential of the crack detection method based on multi-resolution analysis of wavelet was revealed in the light of the response at a single point on a beam-like structure subjected to concentrated moving loads.When moving along the structure,the moving loads cause small distortions in the dynamic response of the beam-like structure at the crack locations.In general,these small distortions are difficult to be detected visually.An ANSYS model of a cracked beam was established.The transient analysis of moving load was carried out by shifting the point of the concentrated force.The response at the mid-span of beam-like structure was calculated and processed with multi-resolution wavelet transformation.The crack on the beam-like structure was then found in accordance with the position of peak value in multi-resolution wavelet analysis of the signals of deflection,velocity and acceleration of the moving load.Furthermore,based on the principle of superposition,the solution obtained for a single moving load was expanded to the case of a series of identical,equi-distant moving loads and opposite direction moving loads,and the key parameter dominating the dynamic response of the beam-like structure was identified.The effects of several cracks and the selection of best wavelet functions were discussed in detail.The proposed method is applicable for low velocity-movements while for high velocity-movements it is not recommended.