Determine if the structure will work or not.

ironxanadu · July 6, 2023, 12:03

Hello All,

I am trying to perform a static structural analysis on a skeleton meant for electrical panel. The aim is apply 8500 Pa of pressure on the top plate of the panel for 5 mins. I have faced the following issues:

The more the refined mesh, the more is the stress value, though the location of occurrence is fairly constant. I have read about the convergence, but what is the mesh element size should I set ?
Unable to decide what is the accurate stress value, should I still proceed with more refined mesh. The minimum thickness of the component within the panel is 2 mm, hence element size is set to 2mm. Is the obtained stress value, accurate. See attached image.
Is the stress a defining factor for the failure of the structure ? While deformation is very low, does that mean that at some locations, the stress experienced is higher, but the product wont fail ?

Any help would be greatly appreciated.

karachun · July 27, 2023, 14:05

1. You faced mesh singularity. Basically you can ignore it if stress occur only at tiny, neglectable portion of model. Here some articles and videos about stress singularities because it is one of basic phenomena in FEA.

https://enterfea.com/stress-singular...st-discussion/
https://www.simscale.com/blog/errors...singularities/
https://www.youtube.com/watch?v=-OHXl-mvR5U
https://www.youtube.com/watch?v=ZP9nh4GOkIc

2. Look previous paragraph.
3. You can go to stress legend setting and set up it so that red color corresponds to portions of structure with stress higher than allowable. Now if large portion of your structure is red, if high stress covers all crossection of those frame elements than you in trouble. But if those red region is small and sits only at stress concentrations than you are fine until load is static.
In general, both stress and deformation used in calculation of structures strength. Columns under compression can also face buckling.

ironxanadu · July 28, 2023, 16:15

@karachun, Thank you so much for resolving my queries

karachun · July 29, 2023, 05:32

Here is another tip - use Beam mesh instead of plate/solid. Model onlu beams, recalculate load from pressure to distributed force.
With beams you do not have singulatities issue and you can your model become simpler and reliable.

ironxanadu · July 29, 2023, 12:40

@karachun, you mean instead of the bonded contacts, I can use beam. if this is the case, what type of contact should I assign between two faces ? No separation or frictional ? Also, if I use frictional contact, the solution will become non-linear.

karachun · July 29, 2023, 12:58

No, I mean linear elements. Here I attach couple of videos so you understant what I want to say. Based on your description I assume that you use Solid elements.

https://www.youtube.com/watch?v=iUAWrFu3TN0
https://www.ansys.com/resource-cente...sys-mechanical

I can not give you more detailed answers - I am not an Ansys Mechanical user.

July 27, 2023, 14:05		#2
karachun Senior Member Join Date: Nov 2015 Posts: 244 Rep Power: 11	1. You faced mesh singularity. Basically you can ignore it if stress occur only at tiny, neglectable portion of model. Here some articles and videos about stress singularities because it is one of basic phenomena in FEA. https://enterfea.com/stress-singular...st-discussion/ https://www.simscale.com/blog/errors...singularities/ https://www.youtube.com/watch?v=-OHXl-mvR5U https://www.youtube.com/watch?v=ZP9nh4GOkIc 2. Look previous paragraph. 3. You can go to stress legend setting and set up it so that red color corresponds to portions of structure with stress higher than allowable. Now if large portion of your structure is red, if high stress covers all crossection of those frame elements than you in trouble. But if those red region is small and sits only at stress concentrations than you are fine until load is static. In general, both stress and deformation used in calculation of structures strength. Columns under compression can also face buckling. ironxanadu likes this.

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July 28, 2023, 16:15		#3
ironxanadu New Member Iron Xanadu Join Date: Jun 2023 Posts: 3 Rep Power: 2	@karachun, Thank you so much for resolving my queries

July 29, 2023, 05:32		#4
karachun Senior Member Join Date: Nov 2015 Posts: 244 Rep Power: 11	Here is another tip - use Beam mesh instead of plate/solid. Model onlu beams, recalculate load from pressure to distributed force. With beams you do not have singulatities issue and you can your model become simpler and reliable.

July 29, 2023, 12:40		#5
ironxanadu New Member Iron Xanadu Join Date: Jun 2023 Posts: 3 Rep Power: 2	@karachun, you mean instead of the bonded contacts, I can use beam. if this is the case, what type of contact should I assign between two faces ? No separation or frictional ? Also, if I use frictional contact, the solution will become non-linear.

July 29, 2023, 12:58		#6
karachun Senior Member Join Date: Nov 2015 Posts: 244 Rep Power: 11	No, I mean linear elements. Here I attach couple of videos so you understant what I want to say. Based on your description I assume that you use Solid elements. https://www.youtube.com/watch?v=iUAWrFu3TN0 https://www.ansys.com/resource-cente...sys-mechanical I can not give you more detailed answers - I am not an Ansys Mechanical user.