In Simulation, what is the number at the end of the bar??

nick_barnett981

Hi, 
I have searched for the answer to this, but with no luck. Can someone tell me what the number at the end of the slider in Onshape Simulation is?
I have run a couple of simulations on the same assembly and noticed that this number changes with each result.

Thanks

Matt_Shields

Pretty sure that's the maximum.  To confirm, click the blue 299.7 on your plot.  Chage it to like 2050.  You should then see only one tiny spot of yellow, there the stress is 2059 MPa.

GregBrown

The 2059 MPa is the maximum calculated over the whole model. The 299.7 MPa is the 95th percentile of the data, but, as pointed out above, can easily be changed. We have chosen to set the default legend max at the 95th percentile in order to produce more intuitive, useful contours. If the legend scale is set to the absolute max over the model, then the presence of singularities (should they be there) or otherwise unphysical stress concentrations, will skew all the colors to the yellow end. Remember this is linear stress analysis, so reported stresses will scale linearly up to infinity. In the real world, and certainly on any structure I would choose to sit in, stand on, fly on... anything beyond yield is meaningless.

Corollary, if you see a large difference (as in the case above) between the default legend max and the model max, then you should suspect some singularities are present. Therefore you should go in a be sure you have not overconstrained something, or connected things that you shouldn't have, or have reentrant (sharp) corners in an area of a load path, etc... 

Another approach is to set this legend value at material yield (or a safety-factored yield) stress. It is certainly an area we've talked about making some usability improvements in future.

nick_barnett981

Thanks Both, this answers the question. I thought it might be this, but was confused why it changed so drastically between different simulation with the same parameters. I was expecting a small variation but not such an diverse range. 
Great info about the 95th percentile @GregBrown, I had wondered about how this limit was set. A good one to have up the sleeve. Thanks

Henk_de_Vl

https://forum.onshape.com/discussion/comment/92343#Comment_92343

| Another approach is to set this legend value at material yield (or a safety-factored yield) stress.

In my opinion, it would be more informative if in addition the max. Von Mises stress value is also mentioned. With that you can compare the calculated stresses. Now I check whether the stresses remain below the yield via the Safety factor (von Mises stress / Yield). That must of course be smaller than 1.