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Summary: Photoelasticimetric study

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  • Summary: Photoelasticimetric study


    Thank you for all your replies

    My question was:
    We would want to do a photoelasticimetric study on fresh bone,
    and for that we thought to use a kind of spray to recover ours
    bones. But after asking informations about that at Vishay
    Micromesure, we learnt that it isn’t so easy! The solution
    is to use
    a thermoformable plastic film what is hard to apply on the
    bone. Then my question is: Do you know a easier solution for a
    photoelasticimetric study on fresh bone? And have you ever
    heard speaking about a « spray »?

    Yours replies:
    [...] Pour plus d'informations regardez notre site WEB sur

    COUSSI Olivier
    I have done some work using conventional thermoplastic photoelastic coating
    (PL2 & PL8, Vishay). In that case, large errors must be expected due to the
    reinforcing effect (L.Cristofolini, A.Cappello, A.Toni: "Experimental
    errors in the application of photoelastic coatings on human femurs with
    uncemented hip stems" Strain of August 1994: pp.95-104).

    About the spray: yes, a technique exists, but as far as I know it is only a
    prototype. I know the group of Eddie O'Brien (British Aerospace, Bristol,
    UK) was working on it a couple of years ago.

    Another problem you should consider: I am not sure what sort of bones you
    want to test. If you are planning to test cadaveric specimens, you should
    bear in mind that all the photoelastic materials are hygroscpic (they swell
    in presence of humidity), and this may cause large additional apparent
    strains due to the humidity contained in the specimen.
    For this reason, I decided to use synthetic composite femur models
    (Cristofolini L., Viceconti M., Cappello A., Toni A. 'Mechanical validation
    of whole bone composite femur models', J. Biomechanics, 1996, 29(4),

    Luca Cristofolini
    We are just getting involved in a study using photoelastic methods to measure
    strain in bone. I understand that sprays are available, but they allow only
    a visualization of strain patterns. Because the sprays cannot be applied
    such that a constant thickness results, strain measurements cannot be made.
    Formable, partially polymerized sheets are cast that have a constant
    thickness. These sheets are then formed to the bone and allowed to fully
    cure, after which they are bonded to the bone using a reflective adhesive.
    The process takes about three days to complete. I don't think an easier
    method of obtaining strain readings by photoelastic methods is available.
    The Vishay instructional bulletins provide a detailed step by step process.
    The bone must be extremely clean of soft tissue. There are many references

    Brent Parks
    Sounds very difficult to me. I have never heard of a spray on
    photoelasitc coating. How would you control the thickness of the
    photoelastic layer? If I remember correctly the fringe order is also
    a function of thickness. With the film one also must consider the
    stiffening that the film itself will impart on the structure (bone).
    Sorry to sound so discouraging.

    Christof Hurschler

    Yours sincerely,

    Philippe Boutemy
    (Groupe d'Etude en Biomecanique Osteo-Articulaire de Strasbourg)