Simulation giving incorrect results

[cmosen]

Hey guys,

I've been trying to do a deflection simulation using Creo 2.0 Simulate which gave me really weird results. I simplified it right down and still am having issues however, I think there must be a setting or property somewhere that I don't know about. The model is a 2000 x 225 x 1.5 mm stainless steel plate, with one of the short edges (225 x 1.5) fixed in place using a displacement constraint which is fixed in x, y and z direction. Then I applied a gravity load acting perpendicular to the 2000 x 225 mm surface. My simulation gives me deflections in the range of km's for some reason, and the deformed display with no scaling shows an unrecognisable model.

I would have thought that the plate would simply have a 'drooping' appearance with a much smaller maximum displacement. When I plot the undeformed shape it has the contours in the correct place, i.e. deflection magnitude slowly increasing, the scale is just way off.

I have also tried placing a small point load at the end instead but it had similar results. I used the included stainless steel material at first, and then tried a custom one with the following properties set: Poisson's Ratio - 0.3, Young's Modulus - 200 GPa, Density - 8000 kg/m^3

Does anyone know what my problem could be?

 

[aust1]

If I was you I would approach it a bit differently until you sort out the teething problems. I would use a less slender cantilever beam and a point load at the end, so you can calculate stress and deflection then compare FEA vs Hand. Once you get that working properly, move onto the gravity load.

Maybe your units for acceleration due to gravity are incorrect?

 

[geesamand]

Are you 100% sure you're using the right units for all of the properties and loads? I don't run Simulate very often and when I do I need to be exceedingly careful that all of the units are correct.

David

 

[brep]

Wondering if the original poster (cmosen) has troubleshot this yet? Questions like this should never be left to gather dust on the internet There's a lot that can be learned by everyone.

There are many ways to approach offering help for this, and certainly a close look an units is always worth the effort. Fortunately cmosen is using Creo Simulate 2.0 which is units managed (properties, loads, etc can be input in any unit; output can be shown in any unit), so barring any typos this should not be an issue...

The real problem is that of reality/physics. The aspect ratio of the part is such that it has no chance of withstanding self weight and indeed will buckle. It is always a good idea to run a buckling analysis to check for negative eigenvalues (load factors) and especially if they are in the first mode of bending (as in the case here). Next, if you are using a linear static analysis then think about what the implications are, both from a solution and postprocessing standpoint. Linear static implies that the stiffness of the structure is computed once (with no load), then the final shape is linearly interpolated based on the linear scaling of the load. Do you think this will apply here? Which brings us then to Non Linear... It's interesting how a simple sounding problem might not be so simple (numerically) after all! I'll leave it to readers to think about and try the nonlinear case. With a geometry like this you can create a hex mesh model using Simulate's thin solid meshing, or prismatic solids, or even mapped meshing feature. Then you can use nonlinear static analysis, with snap through, and so on and so forth. Don't forget to request output at more than just the start end end of the simulation! Use intermediate points to get nice time-based animations.