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Sheet metal bending - spring back effect
Posted Mar 17, 2017, 12:26 p.m. EDT Materials, Studies & Solvers, Structural Mechanics Version 5.2 2 Replies
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Hi
I am trying to make an elastoplastic 2D simulation of sheet metal bending to observe different spring back in various materials. I want to use V-bending proccess since we have a fixture to do the same experiment in the future to check for validity.
I would like to keep it as simple as possible. I am using some data that I have from tensile experiments for different materials and setting simple stress-strain curves with 3 points to vary the hardening. I also set the load/load removal along with auxiliary sweep for the load stepping so the spring back could be observed after the removal of the load.
I am not sure how I should define the contact between the parts. I tried to use contact pairs but I don't know if it is correct. Unfortunately cannot find much about this specific topic on the internet or in this forum (tried to use 3 point bending that someone used which could be similar but didn't succeed much)
I am trying to make an elastoplastic 2D simulation of sheet metal bending to observe different spring back in various materials. I want to use V-bending proccess since we have a fixture to do the same experiment in the future to check for validity.
I would like to keep it as simple as possible. I am using some data that I have from tensile experiments for different materials and setting simple stress-strain curves with 3 points to vary the hardening. I also set the load/load removal along with auxiliary sweep for the load stepping so the spring back could be observed after the removal of the load.
I am not sure how I should define the contact between the parts. I tried to use contact pairs but I don't know if it is correct. Unfortunately cannot find much about this specific topic on the internet or in this forum (tried to use 3 point bending that someone used which could be similar but didn't succeed much)
2 Replies Last Post Mar 23, 2017, 12:49 p.m. EDT
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Posted:
8 years ago
Dear Dimitrios,
Since you are solving a Stationary/Static problem you need enough boundary conditions to eliminate rigid body modes of all parts and make the model stable. It is also better to start with an elastic material to make sure contact is properly set up and then add back the plasticity. For ways to make a stationary contact problem stable check out COMSOL Application Gallery model #13645 titled “Friction Between Contacting Rings”.
Nagi Elabbasi
Veryst Engineering
Since you are solving a Stationary/Static problem you need enough boundary conditions to eliminate rigid body modes of all parts and make the model stable. It is also better to start with an elastic material to make sure contact is properly set up and then add back the plasticity. For ways to make a stationary contact problem stable check out COMSOL Application Gallery model #13645 titled “Friction Between Contacting Rings”.
Nagi Elabbasi
Veryst Engineering
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Posted:
8 years ago
Thanks for the reply. I checked the example and made few changes in my model.
I am now using symmetry and defined contact pairs (no friction), also used a soft spring for the sheet metal to stabilize the model.
So when I use only elastic analysis it works (althouth I get one warning about relative error being larger that relative tolerance).
When I add plasticity it seems to have problem converging when unloading. When the simulation stops with the error of no convergence I can see all the frames up to my max load correctly but it fails one or two steps after that.
I am using small step size so I am not sure what else I should check.
This is the load stepping: 0 range(0.44,0.05,0.59) range(0.63,0.05,1.08) range(1.1,0.05,1.9) range(1.95,0.05,2.2) Max is at 1.1 and convergence fails at 1.2. I tried also smaller step after the max load but didn't work
Any suggestions- ideas?
I am now using symmetry and defined contact pairs (no friction), also used a soft spring for the sheet metal to stabilize the model.
So when I use only elastic analysis it works (althouth I get one warning about relative error being larger that relative tolerance).
When I add plasticity it seems to have problem converging when unloading. When the simulation stops with the error of no convergence I can see all the frames up to my max load correctly but it fails one or two steps after that.
I am using small step size so I am not sure what else I should check.
This is the load stepping: 0 range(0.44,0.05,0.59) range(0.63,0.05,1.08) range(1.1,0.05,1.9) range(1.95,0.05,2.2) Max is at 1.1 and convergence fails at 1.2. I tried also smaller step after the max load but didn't work
Any suggestions- ideas?