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# Multi-plate deflection analysis??

## Multi-plate deflection analysis??

(OP)
How can I model (3) flat plates which are bolted together in their four corners and has a load in the middle.

I need to examine their stresses & displacements relative to each other.

### RE: Multi-plate deflection analysis??

You can calculate the total moment of inertia and solve for an equivalent high (thickness) of the plate and then model it in Pro-M.

(bh^3)/12 = SUM [(bh^3)/12]
Total = sum of all of the plates

Since the base is the same, it can be deleted and then solve for “h” in total and this will be the equivalent height (thickness) of all of the plates combined.

Good luck

Go Mechanical Engineering
Tobalcane

### RE: Multi-plate deflection analysis??

(OP)
That would work if I wanted to analize all 3 plates as an "equvilant unit".  However, the point of interest is how do the individual plates move and stress relative to one another.  That is the analysis task at hand.

Any suggestions?

### RE: Multi-plate deflection analysis??

Model the plate with the equivalent thickness and then apply the load that you want.  The deflection that Pro-M solves for will be the same for all the plates in question.  Now, model one of the plates in question after constraining where it is usually fastened, constrain the bottom side (in the load direction) so that the plate can only deflect what Pro-M solved for.  Apply load that will get the desired defection.  Once done, you can find the stresses due to the deflection.  Do this for each plate if there are different thicknesses.  To correlate, you can use Roark’s Formulas to do the hand calculations.

I’m not sure if you can model all three plates.  If you put them together, Pro-M will “fuse” them and make it one plate which is not a realistic model.  And, if apart the plates will not react to each other.  You can use contact, but I don’t think that it can take in consideration of the shear that happens between the plates.  I do believe that contact is only for direct perpendicular load.  I could be wrong about the contact, I don’t use it that often, but if you just need some upfront data, the previous suggestion will get you there.

Hope this helps

Go Mechanical Engineering
Tobalcane

### RE: Multi-plate deflection analysis??

Use Quarter Symmetry. Create the three plates with a small gap between them and use contact regions. The bolt can be simulated in many ways - beams, solid with contact regions, etc.
Are you using Pro/E, or Mechanica Independant, and what version?

### RE: Multi-plate deflection analysis??

How did you make out?  Did the contact reqion work?

Go Mechanical Engineering
Tobalcane

### RE: Multi-plate deflection analysis??

TThis can be done. I have used MECHANICA to do a stress analysis of a damper valve springs disks. RocketRonnie has it right; use the smallest repeatable portion (cyclical symmetry) and solid elements. Contact regions for all adjacent surfaces will be necessary. Use traditional techniques (like use of thermal expansion) for the bolt pre-load. Good luck!

Best regards,

Matthew Ian Loew

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

### RE: Multi-plate deflection analysis??

(OP)
Sorry it took so long to get back to you all.  I appreciate the advice, it all helped in different ways.

Thanks again.

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