The presence of cracks in the rotor is one of the most dangerous and critical defects for rotating machinery.Defect of fatigue cracks may lead to long out-of-service periods,heavy damages of machines and severe economic consequences.With the method of finite element,vibration behavior of cracked rotors and crack detection was received considerable attention in the academic and engineering field.Various researchers studied the response of a cracked rotor and most of them are focused on the crack detection based on vibration behavior of cracked rotors.But it is often difficult to identify the crack parameters quantitatively.Second generation wavelets (SGW) finite element has good ability in modal analysis for singularity problems like a cracked rotor.Based on the fact that the feature of SGW could be designed depending on applications,a multiresolution finite element method is presented.The new model of SGW beam element is constructed.The first three natural frequencies of the rotor with different crack location and size were solved with SGW beam elements,and the database for crack diagnosis is obtained.The first three metrical natural frequencies are employed as inputs of the database and the intersection of the three frequencies contour lines predicted the normalized crack location and size.With the Bently RK4 rotor test rig,rotors with different crack location and size are tested and diagnosed.The experimental results denote the cracks quantitative identification method has higher identification precision.With SGW finite element method,a novel method is presented that has higher precision and faster computing speed to identify the crack location and size.
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