G2500-2 Actuator Bolts Vibration Testing And Analysis

Any mechanical system can vibrate under certain conditions. If the frequency of exciting force caused by external drive or self-unbalance is near the nature frequency of the system, a phenomenon named resonance vibration will occur. In this state, the stress and strain are magnified greatly, and the strength of the system sharply decreases.In practical application, the M10 180 bolts, which are installed in the head cover of the torque divider of TS5560 special automobile, sometimes fracture all of a sudden. According to the tests of acceleration, stress and strain, and the exciting test, it is resonance vibration that leads to the compound-bending fatigue fracture of the bolts. The exciting force caused by drive system, transmitted through the torque divider, produces a 1000-1500Hz cyclical excitation at the junction of the bolts and head cover, which causes the first order bending resonance vibration of the bolts. Because of the deficient damp, the bending stress at the junction is magnified greatly, and the fatigue life decrease sharply.Based on mechanical vibration theory, with the torque divider's structure unchanged, there exist two kinds of approach to reduce the resonance: one is keeping the bending vibration frequency away from the excitation frequency, the other is increasing the modal damp. Accordingly, a series improvement measures, such as replacing bolts with double-screw bolts, filling the gap between the double screw bolts and the torque divider with fluid sealant, etc., are proposed. These measures prove effective through a 7000Km running test.In the first part of this thesis, the fracture problem of the bolts installed in in the head cover of the torque divider of TS5560 special automobile is introduced, and the domestic and abroad research work on vibration measurement and experimental modal analysis is presented.In the second part, the single-degree-of-freedom forced vibration theory and DFT algorithm are introduced briefly. The technology of vibration measurement and experimental modal analysis is discussed in details, on which the fault diagnosis of bolts' fracture problem is based.In the third part, taking advantages of the tests of acceleration, stress and strain, the exciting test, and modal analysis method, it is found out that resonance vibration leads to the compound-bending fatigue fracture of the bolts. Accordingly, a series improvement measures are proposed. These measures prove effective through a7000Km running test.In the last part, some conclusions and prospect are given. The main achievements of the thesis are summed up and some directions of future research on improving the dynamic performance of special automobile are put forward.