Forging process

[OziAbaqus]

As this is my first post in the forum I would like to say hello to you all . After reading some posts and checking your high level in handling Abaqus I have decided to register to get some help, if you dont mind, in a problem that is driving me crazy. First, I would like to make it clear that my English is not very good and that I'm self-taught in Abaqus, so sorry if you find my questions very simple.

I'm performing a forging analysis in which the upper die of the forge moves down a certain displacement (determined as a boundary condition) to deform the quarter of the workpiece (double symmetry) The main problem is that the upper edge of the workpiece exceeds the upper die surface (please, have a look to the attached screenshots to understand what I'm saying). This is note the only problem: despite the great deformation of the part it doesn't totally plastify and the bottom right corner barely displaces along the x-axis direction, as it should be expected.

Just to let you know if you want to correct me:

- I have defined the upper die as an analytical rigid.

- NLGEOM=Off. As far as I know, we just turn this option ON provided that the geometry changes in such way that the angles between the parts (and the force, if there would be one) will be different, but this is not the case. However, maybe I'm wrong and we consider non-linear geometry when there are great deformations too (as in the case of the a forging process). Any comment?

- For the contact conditions I have used a frictionless model (in the case of the screenshots model). Anyway, when considering friction I have planned to use a penalty formulation.

- Sliding formulation: finite sliding.

- Structured mesh. Element type: CPE4R. I have prevented the hourglass by toggling on the 'Enhanced' option. Anyway, as there is no bending, should I consider the hourglass phenomenon?

- I have run the analysis in Abaqus/Standard as the forging can be considered as quasi-static.

I have read something about adaptive meshing. Could this solve the problem?

If you want me to explain something better or need me to attach any file, please let me know.

Thanks

 

[IceBreakerSours]

I am not sure if I fully understand the problem. Do you want to upload your INP?

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[OziAbaqus]

Hello,

Thanks for answering . I have attached the input file as you requested. Tell me, please, what you didn't understand and I'll try to be more precise in my explanation.

I have read the FAQs and it seems I haven't broken any rule. If I have, please let me know.

 

[IceBreakerSours]

Its not attached. Click on link that says "...or upload your file to ENGINEERING.com"

[FAQ-thing is just my signature; don't worry about the rules.]

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[OziAbaqus]

Oh, thanks a lot! I totally forgot to do it! Now it's attached

As I said before, anything you don't understand or doesn't seem clear, please let me know.

 

[IceBreakerSours]

No normal contact property defined.

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[OziAbaqus]

I didn't use it because in the Getting Started With Abaqus: Interactive Edition example in chapter 12 (Page 14) it was not considered, just the tangential behavior was included. However, I have just run the analysis again with a Pressure-Overclosure: Hard-Contact and a Constraint Enforcemente Method: Penalty and the problem persists, the upper edge of the workpiece exceeds the upper die.

 

[OziAbaqus]

Any idea about the source of the problem?

 

[IceBreakerSours]

I have made some slight changes and added contact stabilization. Check the results with/without the nlgeom flag on.

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[OziAbaqus]

After having checked the .inp file the only changes have been the introduction of the non geometrical linearity and the contact stabilization, right? Correct me if there is another one, please, because I haven't seen it in the code.

On the other hand, how can I implement these changes in my Abaqus file? I have tried to substitute your code in my .inp file but it didn't work.

Thanks a lot for your help.

 

[IceBreakerSours]

I also got rid of the "initializing contact" step. I also changed the normal contact property but try and see if getting rid of the normal contact property changes your stress results.

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[OziAbaqus]

At least the upper surface of the workpiece doesn't exceed the die surface anymore, but now there is another problem similar to the preceding one that Ill try to correct. I have had a look at the Theory related to the adaptive meshing in the manuals and is huge. Could you or anybody else give me a link where its use it's explained clear and simple, please? I would like to understand it because its recommended in situations where the deformations are very big.

 

[OziAbaqus]

I really appreciate your help. I have just given you a star.

 

[IceBreakerSours]

Unless you have some background in computational fluid mechanics or something along those lines, theory may be a little hard to follow. Try the Analysis User's manual and run examples from other manuals like examples/verification/benchmarks etc. To be able to use adaptive remeshing from CAE, use the CAE manual; this part is easy.

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