After a bit of guidance please

UGMENTALCASEUGMENTALCASE
Morning all,

I have a frame work which is sitting central about two stations. The ends are bolted to two turnover units. I'm just trying to figure out how much the box section frame will sag under it's own weight. Might seem simple to you guys, but I'm very much a beginner. Any help would be great. I've fixed it on the mounting holes both sides, and applied a gravity? The two outer brackets I've used a bonded contact to the central piece, as this will be bolted here as well. I'm only after a rough idea of what's going to happen to it.

Any help would be greatly appreciated.

Thanks

Comments

  • VictorVictor
    Looks alright the way it is. Two things I'd check just in case:

    1) Displacement is getting a bit large compared to the thickness of the members so it's a good idea to do a nonlinear analysis. The two supports might end up loaded in tension (towards each other) as the frame sags and that can have a significant effect on the results. Linear analysis can't pick up this effect. However, if the support won't actually support a tensile load (eg a shaft with a little axial play) then that's different and you'll have to adjust the constraints accordingly.

    2) Mesh convergence study. Since it's going to get quite big with refinement, you might model just one quadrant and use symmetry constraints to keep the node count low.
  • UGMENTALCASEUGMENTALCASE
    Excellent! Thanks for coming back to me, and thanks for the pointers, I'll keep that in mind. Especially the pulling towards each other. The stations would then come into play.

    Thanks again
  • UGMENTALCASEUGMENTALCASE
    Good Evening, I've been looking over this and I'm not totally convinced to be honest, I must be doing something wrong. I've broken it right down now, and I'm just applying gravity to one piece of the box section, and the bend is massive!

    I've fixed the attached file at one end, and applied the gravity, and it sags 23mm! However, if I applied a force to mimic the gravity what would that be? I may be over thinking things, but I'm struggling to see it bending that much, the bar weighs around 10Kgs.

    Sorry for sounding a bit dim, it's been a long day!
  • VictorVictor
    I just noticed the Young's modulus seems to be too small - 275 MPa, not GPa.

    If that's not it, could you attach the liml file for the single bar?
  • UGMENTALCASEUGMENTALCASE
    Oh no, dont tell me its that simple!!!!! So for Gpa you can just type in 275, but I would need the additional zero's for Mpa?

    Victor, thank you again! I think I need to go to sleep! Thanks again :-)
  • DaveStuppleDaveStupple
    Ug, There is a dropdown menu at the right of the modulus entry field, use this to choose your units. If you already have a number entered, Mecway will convert, so be careful! What I mean is, if you change from MPa to GPa, Mecway will change your 275 to 0.275, so having chosen GPa you then need to change 0.275 back to 275.
  • UGMENTALCASEUGMENTALCASE
    Got it! So Gpa is almost like a parent. So you type 275, then change to Mpa you get the zero's, change to Pa and get more zeros!

    Silly mistake to make by me there, thanks for the help!
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