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Cantilever Experiment

  1. Jul 29, 2009 #1
    I have been browsing the web for experiments on the determination of Elastic Modulli of a beam. So far the experiments that I have been reading can be categorized into two types (i may be wrong on the details):

    1) Generate a matter wave in the beam (eg. Seismic excitation), adjust the frequency until resonance occur and use the frequency of the fundamental mode to deduce the elastic moduli.

    2) Deflect the beam using load of varying mass, determine the deflection (eg. using a laser sensor), draw graph and obtain the value of elastic moduli from the gradient of the graph.

    Most of the experiments I read adopt the first method. Is there any advantage for using the first method compare to the 2nd one? Is it more accurate and less prone to experimental error?

    I have also read anothers experiment proposed by our senior. They set the beam to vibration by deflecting it using hand, and obtain the frequency using a laser sensor. (the laser is placed on top of the beam. Whenever the beam pass below the laser, the laser will be block. Hence the frequency of the vibrating beam can be determined.)

    I was stunned by the simplicity of the experiment, and suspect that this experiement may be prone to error. Since, if the Young's modulus can be determined that easily, why do we bother doing complicated steps like adjusting the frequency, detect resonance, etc.?

    Thanks in advanced.
  2. jcsd
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