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Homework Help: Comparing theory predictions with practical results of mass/spring/damper system

  1. Nov 16, 2011 #1
    1. The problem statement, all variables and given/known data

    Compare theoretical predictions for frequency response of a mass spring damper system with analytical test data.

    1.) Carry out free response tests and use data to calculate damping ratio, damped and natural frequencies and damping coefficient and spring stiffness.

    2.) model the system and derive equation of motion, put into standard form and use solution to show which equation to use for magnification factor.

    3.) plot theoretical frequency response graphs

    4.) carry out forced response tests and use data to calculate magnification factor, frequency ratio and phase lag.

    5.) plot the forced tests on the same graph as theoretical.

    6.) compare the two

    2. Relevant equations

    lots....

    3. The attempt at a solution

    I have completed all of the above. My query is that when plotting the two sets of data on my graphs i find that the magnification factor values for the test data are a LOT lower than the theory. I was expecting a bit lower because the theory doesn't account for friction etc but not this much lower.

    So my question i guess is: When comparing practical with theory is it usual for the two to differ greatly or just marginally?
     
  2. jcsd
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