Dear Sir/ Ma'am,
The simulation I have run here is simple uniaxial tension test with Symmetric boundary contions in X,Y and Z on ABAQUS Explicit. This was done as a Test for a VUMAT code (Hyperelastic material with near incompressibility) that I had developed. The simulation starts with a loading phase, where the Stretch in X-direction is increased from 1 to 6, and a subsequent unloading phase coming back to the undeformed state. The analysis type is a Coupled Displacement + Temperature, with the C3D8RT (Reduced Integration) element type. The VUMAT code has been validated for a uniaxial tension 1-element simulation, but shows unrealisitic deformations during the unloading phase, when I use multiple elements (I have attached the pictures below).
What could be the causes for a change in solution after mesh refinement? Any help or inputs would be helpful, I look forward to your replies.
You need to merge the two elements to form one element in building your model
what you're seeing is the classical hourglassing...compare ALLAE w ALLWK or ALLIE
Dear Abhimanyu and Khlaed,
Thank you for your quick replies.
Regarding the hourglassing, I tried the same simulation of 9 elements with fully integrated elements as well, only to see the same issue. Given that this hourglassing mode is only something which results from Reduced integration, It could have some other root cause. Would you have any other ideas?
One element simulations, or simulations where the Z-symmetric BC is applied directly to all elements do not show this issue. The solution of merging elements might work for some simple simulations, but given that I need to use finer meshes for other test cases, it would be better for me to achieve the same results irrespective of the mesh size.
Looking forward to your replies.
Vinayak Ramesh
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