INFLUENCE OF PLATE THICKNESS AND EDGE CONDITION ON VIBRATION AND ACOUSTIC RESPONSES

摘要

In a vibration created noise problem, the overall damping can change the vibration and acoustic responses.Since the plate’s clamped condition can change the damping easily, accurate predictions of vibration andacoustic responses in FEM/BEM are very diff%xlt. It is about the same difficulty to predict the mode frequencyaccurately for a cover with clamped-clamped B.C. since the ideal clamped edge condition doesn’t exist in a realcover. In a real cover’s vibration, only partialedges around the bolts are clamped. The edges between two boltsremain free (slipping). Assigning the corrected edge condition to a cover in a FEM model is a challenging joband relies heavily on the user’s experimental experience. Increasing the number of bolts (i.e. less space betweenbolts) or increasing the clamping torque will reduce the damping and thus increase the radiated noise.Increasing the plate thickness or adding a gasket will not increase damping. In a low frequency range, increasingthe plate thickness in a whole-body vibration engine may not optimize noise reduction. However, a certainamount of noise reduction is zeal&d as the mode frequencies are raised to cross the plate critical frequency.