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designing a vibration absorber...  
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Posted by: misty2 ^{®} 05/07/2004, 12:39:08 Author Profile Mail author Edit 

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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(x1x2) m2x2" = k2(x2  x1)  c2(x2x1) 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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