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bone breakage and X-section

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  • bone breakage and X-section

    I am wrestling with a problem that I hope someone out there can help me with.

    I am investigating the breakage of tail spikes in the dinosaur Stegosaurus. Interestingly, about 10% of the sample (n=52) show breakage with subsequent remodeling of the broken surface. How much force is required to break the bone? Almost without exception, the papers that discuss bone strength, bone bending etc., deal with a know force applied either in cantilever or 3 point bending. Unfortunately, I have too many unknowns for me to use any of these formulas. Also, most models dismiss the cross-sectional area of the bone as unimportant to bone strength, but that cannot be true for the spikes. Here is what I know:

    1. the spike was held in cantilever relative to the tail (tail now thought to be horizontal, spike horizontal to tail)
    2. for simplicity, the spike may be considered as a cone.
    3. using an undamaged spike as a model, length is 53 cm with a basal radius of 3.3 cm
    4. specimen 1 broken at 39.5 cm from base, radius 1.7 cm, 11% porosity.
    5. specimen 2 broken at 20.5 cm from base, radius 2.6 cm, 16% porosity.

    Granted that the strength of the bone is dependent on a host of factors that can no longer be determined (ash content, amount of calcium, etc.), therefore certain assumptions about the spike have to be made.

    The amount of force needed to break the spike in specimen 2 must be greater than the force for specimen 1. The question is what is the force in Newtons needed to do this?

    Thanks for any and all help.


    Kenneth Carpenter, Ph.D.
    Curator of Lower Vertebrate Paleontology &
    Chief Preparator
    Dept. of Earth Sciences
    Denver Museum of Natural History
    2001 Colorado Blvd.
    Denver, CO 80205

    Fax: (303)331-6492

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