A milling machine which weights 120KN is vibrating within the frequency of 20 Hz to 40 Hz due to an unbalanced mass.
(a) The laboratory has an accelerometer with a natural frequency of Wn = 100 rad/s. Determine if the accelerometer is suitable for measuring the acceleration of the milling machine vibration if the measurment error is to be less than 5%.
(b) The shop floor wants to isolate the vibration from the milling machine to yhe ground. The required transmissibility ratio TR is 0.3 at 30 Hz using an isolator that has a stiffness of K=50000000 N/m. Find the damping ratio of the isolator.
2006-11-08 03:03:23 · 1 answers · asked by Jeff Ang 1 in Science & Mathematics ➔ Engineering
For (a), with a nat. freq. of 100 rad/s or about 16 Hz, the measurement error is bound to be greater than 5% at the upper range of the excitation, 40 Hz.
For (b), the necessary equations are found in the reference. First solve for the natural frequency of the mass-stiffness w0 using eq. 5. Then iterate eq. 7 to find the maximum Q needed for a TR = 0.3 at w = 30 Hz. Finally use eqs. 6 to get the needed damping ratio zeta.
2006-11-12 01:03:27 · answer #1 · answered by kirchwey 7 · 0⤊ 0⤋