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ptc-3801071-Visitor
1-Visitor
January 6, 2006
Question

Use of springs in ProMechanica

  • January 6, 2006
  • 4 replies
  • 1175 views
Dear ProM's,

This is probably a bit basic, but I feel compelled to ask the question. In
the practical use of mechanica, I am having a bit of a problem
understanding what practical uses there are for springs in analysis. Can
someone give me a practical example? Maybe a short description of the
intended use for springs?

Any help would be greatly appreciated...

Greg Saiter....

    4 replies

    P
    ptc-6916241-Visitor
    1-Visitor
    January 6, 2006
    Greg,

    I am sure there are many uses, but I always use the to take out rigid
    body motion. It is better than a rigid restraint, which may cause
    unrealistic stress.


    John
    D
    doug.bittner1-Visitor
    1-Visitor
    January 6, 2006

    Hi Greg,

    We design multiple axis positioning systems (think X-Y stages). I use
    springs to model the linear bearings. The ProM-springs are a bit flaky
    in torsion, but with careful set-up, a quad set can model a linear
    bearing's pitch, yaw, and roll stiffnesses, as well as the lateral Ky &
    Kz.

    Good luck, and happy modeling.
    -Doug


    Doug Bittner
    Staff Mechanical Engineer
    Danaher Motion - Dover


    R
    randyspeed1-Visitor
    1-Visitor
    January 6, 2006
    Greg,

    By far, springs in FEA have been mostly used to model fasteners. However,
    there are other novel uses, such as those you have already heard of from
    other users.

    Springs are very efficient (run time) and represent the most basic property
    of the finite element method, stiffness. They do a very nice job of solving
    the force and displacement components of a model. You will not have stress
    output available for springs.

    The caveat with springs is that since there is no area at the point of load
    transfer, stresses are unreliable at the mating parts in the vicinity of the
    spring attach points. If you are solving for stresses in your analysis, you
    may consider excluding elements in those vicinities from convergence (MPA
    convergence algorithm, of course). The run will complete much faster.


    Randy Speed
    President and CEO
    Speed Consulting, LLC
    (972) 938-0490 ph (972) 937-2319 fax
    www.speedconsulting.com
    R
    rdubr1-Visitor
    1-Visitor
    January 24, 2006
    Randy,

    Can you exclude elements in integrated mode - or only independent Mechanica?
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