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Separation of the bodies in contact after Force based loading in ABAQUS

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abqsuser

Mechanical
Mar 22, 2014
3
Hey,

I am simulating pressing of a viscoelastic material against flat molds. In the actual process, first the material is pressed by the molds which moves at a constant velocity until a particular load value of x kN(Step-1). Then the material is is pressed at different constant force levels(Step-2). After the force based loading, again displacement is applied on the molds to separate and release the workpeice(Step-3).
I have implemented this using UAMP subroutine and till step -2 is completed successfully with out any errors. After the force based loading is complete, when I am applying rigid body displacements to the lower mold only for separation, error message "Displacement increment for contact is too big" appears in the simulation.

I have taken care of the unit systems and ensured that displacements are applied properly. I observe in beginning of STEP-3 the molds are like sticking to workpeice, high level of stresses are developed on the contact surface of the molds and it is unable to get separated. "Allow separation after contact" option is ticked on. I am using general contact options and all default options has been used in the simulation.
Note that displacements are applied on the REFERENCE POINT and the FORCE are applied on the nodes.

Can anyone suggest any idea/solution for this to handle this situation ? I am curious to know after a force based loading step, applying displacement based loading is not possible for rigid body displacement?

I will be thankful for any kind of help/suggestions

 
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Dear All,

Thanks for your response. I could sort out the issue.

The issues was defining the contact surfaces. I used the general contact option and I had linked the contact surface as well other adjacent surfaces of molds with the workpeice. I corrected it to only the surfaces coming in contact

Also Second change that I made is till the STEP -2 UAMP is used. In step 3, since the velocity details are known, I used the default velocity BCs on the Reference point in STEP-3.

After implementing these corrections it got sorted and now the simulation runs smooth as expected.

Thanks all for the response.
 
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