Beam calculator Free software ?

Discussion in 'Software' started by Erwan, Aug 12, 2016.

  1. Erwan
    Joined: Oct 2005
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    Erwan Senior Member

    Hi everybody,

    I d like to calculate some I-Beam/UD Carbon stifness.

    But I am totally rookie with structural engineering & FEA

    That is why I ask if anybody knows a good freeware which could be useful for my problem.

    Thanks in advance

    EK
     
  2. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I fear that there is not a free software that calculates what you want but if you were to get payment software, if you have no knowledge of how heterogeneous materials are calculated, could not help much.
     
  3. gonzo
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    gonzo Senior Member

  4. John Perry
    Joined: Nov 2003
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    John Perry Senior Member

    The online calculators sugested by Gonzo look good for getting a rough idea of the stiffness/deflection of a carbon fibre beam that has already been appropriately designed by others. For that purpose I would suggest inputting a Youngs modulus of say 90GPa, but only for an approximate preliminary result or perhaps for comparison of alternative sections. A more sophisticated approach is necessary if the results are critical to your design work or to safety.

    A carbon fibre beam is not normally all UD reinforcement. Typically there would be mainly UD where the stress is mainly direct stress and mainly biax where the stress is mainly shear. The simple formulae or the calculators that Gonzo sugests wont help you with working that out and optimising the laminate accordingly, but perhaps that is not what you are trying to do.
     
  5. Erwan
    Joined: Oct 2005
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    Erwan Senior Member

    Thank you very much TANSL, Gonzo, John,

    You are perfectly right TANSL, and before a clear understanding of heterogeneous material, I have to start from scratch, and be able to design the
    "diagram of free body forces " or someting similar.

    For instance, finding the appropriate loading case (among all available on Gonzo's calculators) remains challenging for a rookie.

    I tried to make 2 little drawings of the carbon I beam (attached) in an attempt to describe the loading case.

    The issue is to have a rought guess of the (weight/inertia) of the rear spar.
    Its thickness (as small as possible) is fundemental to define the aerodynamic solution.

    Thanks again and any ideas are welcome

    Cheers

    Erwan
     

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  6. John Perry
    Joined: Nov 2003
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    John Perry Senior Member

    Ok, I see what you are up to. There is quite a lot of interest in 'soft' wing sails these days.

    I would suggest treating that trailing edge spar as a beam pin jointed at the ends and uniformly loaded along the length, at least for the purpose of getting a rough idea of its deflection. Clearly it is not really pin jointed at the ends, it is fixed into structures which are only roughly detailed in your sketches. I suspect those are lightweight structures and not rigid enough that the beam could be considered to be 'built in' at the ends - its probably somewhere between pin jointed and built in, but pin jointed is the 'safer' option in that it will tend to overestimate the deflection.
     
  7. Erwan
    Joined: Oct 2005
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    Erwan Senior Member

    Thank you John,

    You are reading in my mind.

    Before computing the E.I from the equations, it is important to state correctly the problem.
    As you suggest I should use the "pin end" assumption.
    I considered it but to make things simplier to present; I choosed the cantilever option.
    Only the bottom part of the wing sail is represented on my candid sketches.

    But there is the upper part of the rig which will be pluged above.

    So the moment of the upper part of the rear spar(around the horizontal Twist Control Arm)is likely to cancel (more or less) the moment of the bottom part of the rear spar.

    That is why to make it simple I represent the "BUILT IN/ FIXED END instead of pin end
    But I am a bit too rookie to be sure it is correct.

    Another reason, is I expect less deflection with build in end instead of pin end but it is more about whishfull thinking than rational analysis.

    Thanks for your interest in this soft wingsail project.

    Cheers

    Erwan
     
  8. John Perry
    Joined: Nov 2003
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    John Perry Senior Member

    Erwan
    What I think you are saying is correct.

    A pin jointed beam of length 2L uniformly loaded along its length has exactly the same deflection as a cantilever beam of length L having the same uniform load per unit length. So you can analyse that spar as a beam with pin joints at the ends, or equally well consider just half the length as a cantilever beam.

    The later is possible because the slope of the pin jointed beam at the mid point is zero, so each half of that beam behaves like a cantilever beam that is 'built in' (i.e. zero slope) at one end.

    So you can use either method of analysis, depending on which best suits your on-line calculator.
     

  9. Erwan
    Joined: Oct 2005
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    Location: France

    Erwan Senior Member

    Thanks very much John

    All of this knowledge is far from intuitive for me, so I need time to chew it, just like to learn how to use the calculators provided by Gonzo.

    So far I have been using "analogy" , I mean I have a top of a windsurf mast 100% carbon T700 and 2.60 meters long
    I plugged it horizontaly and put a serie of bottle of water with different weight in order to mimick an elliptical aerodynamic load.
    I observed a very little deflection.
    Wind surf masts have provided a good rought idea, but now I think I need more precise and accurate guesses.

    Thanks again

    Cheers

    Erwan
     
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