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Re: designing a vibration absorber...
Re: designing a vibration absorber... -- misty2	Post Reply	Top of thread	Forum

Posted by: jbel ® 05/22/2004, 07:55:34 Author Profile Mail author Edit

First, I believe you have formulated an incorrect matrix. I am assuming the following conditions: k1 = spring from ground to machine k2 = spring from machine to absorber c1 = dashpot from ground to machine c2 = dashpot from machine to absorber My equations of motion: m1x1" = -k1x1 -k2(x1 - x2) - c1x1 -c2(x1-x2) m2x2" = -k2(x2 - x1) - c2(x2-x1) These are the same as your equations!!!!!!! Try this matrix form: [m1 0] [x1"]+    [c1+c2  -c2][x1’]+    [k1+k2 -k2][x1] =[Fosinwt] [0 m2] [x2"]      [-c2        c2][x2’]       [-k2      k2] [x2]    [ 0         ]  Review your equations and redo your matricies and you should get the same answer, I think you just transposed something when writing the stiffness matrix. As far as calculating k2: Do just as you said. set (omega) = (omega)(nat. abs.)  noting that  (omega)(nat. abs.) = sqrt(k2/m2) Then: (omega)^2 = (k2/m2) Now, choose m2 to be some value, and if you know (omega) you then know k2!!!!!! This allows you to choose your absorbing mass and then calculate the corresponding spring stiffness.

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