Study On The Crack Detection Based On Modal Analysis

With development of high—speed and heavy haul railways, rolling contact failure of wheel/rail, such as rails, wheelsets and so on, become more and more serious. Especially, it is important to monitor wheelsets during their service life. This thesis studied the wheelsets damage using testing software of LMS. Test. Lab and large—universal FEM of ANSYS. Wheelsets damage detection is studied by the way of structural vibration analysis.The first chapter of this thesis reviews the literatures on the crack damage research field, and indicates the significance of monitoring the wheelsets. Chapter 2 shows the correctness of research via the ANSYS software. Firstly, use the theory of vibration and modal analysis, and make use of the general finite element software of ANSYS to simulate the crack of thin plate. Secondly, based on the test results of LMS. Test. Lab, it is possible to use the ANSYS software to research wheelsets crack damage.Following, based the general finite element software of ANSYS, the KRD3—915D wheelsets model is established in this thesis. A series of simulations are made to diagnose extent of damage for railway vehicle wheelset close to unloading groove. Modal analysis is studied by the way of destructive and un — destructive wheelsets, and harmonic responses are researched among the frequency of 114~190Hz, 220~240Hz and 336~360Hz. Some results are obtained. The same vibration mode shape of wheelset is similar on the whole. Along with increment of extent of damage, the natural frequency shift from high frequency to low frequency. But some natural frequency doesn' t shift. Large extent of damage results in large change of frequency. It is obvious that amplitude of displacement frequency response function shift between damaged and undamaged wheelset. Parameters of strain are fitted to become monitoring parameters relative to parameters of stress.Finally, from the results of analysis, it is possible that crack detection is inspected by the shift of frequency and change ofvibration mode. The change of modal parameters is researched by fixed point crack. Some results are feasible. In other words, it is indicated that amplitude of strain frequency response function is adopted to diagnose small damage and frequency is adopted to diagnose large damage.