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    Calculating Modulus of Rupture

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    Please help with the following problem. See the attached wood block diagrams.

    If a break load of 250 lbs. is applied to the first wood specimen, how do I determine the Moment of Inertia and calculate the Modulus of Rupture?

    The only difference between the specimens per the attached diagram is that a 1/4" x 1/4" key-way is cut into the center of the 2nd specimen.

    This is a simply supported beam analysis....but how do I calculate what I need and determine the difference in break load between the two??

    © BrainMass Inc. brainmass.com October 9, 2019, 8:12 pm ad1c9bdddf


    Solution Preview

    We take MOR = 3250 psi for the wood

    Let F be the force acting in the middle of the wood block.
    Let L = 6" be half the length of the block.
    As the point of application of the force is in the middle, each support applies F/2 to its end of the block.
    As the arm of each support relative to the middle is L/2, we find the bending momentum to be

    M = (F/2)*(L/2) = FL/4 (1)

    Now, refer to the useful explanations for "Pure Bending" at link ...

    Solution Summary

    The solution computes modulus of rupture. Step by step calculations are given.