Contact proble: a ring pushed by a pin, how to solve?

[Wu Tiesheng]

Hi all, I’d like to solve a problem: a ring pushed by a pulled pin of same sized in the center. How to construct the model and solving?

[NextFEM Admin]

Dear Wu,
NextFEM Designer is design-oriented, we do not support contact problems. Anyway, your model description is not so clear as to make me able to suggest you a convenient alternative.
regards

[Wu Tiesheng]

Thank you for your reply. My model is in attachments. In the model, a pin will be pulled toward a steel ring. but I don’t know how to treat contacting yet, so the pin is left free now in the model, and forces are applied at inner side of the ring for a simplification. The problem will be treated as plane streessed, but the resulted stresses are too small.
I am a newer of your excellent software yet, It must be something wrong with my model, but I don’t know how. May the elements selection wrong? How to distinct between plane stress and plane strain proble by your software?
PS: the Attachments exceeding 512 Kb, so download please.
http://pan.baidu.com/s/1nvvyBhv

[NextFEM Admin]

Dear Wu, thanks for your reply. Unfortunately I cannot access your attachments, please uploade them again, I raised the size limit.

To distinguish between plane stress and plain strain use the command in Edit/Changem element type… on the the selected elements.

[Wu Tiesheng]

Thank you. The model is in the attachment. The area stress S22 seems too small or I misunderstanding the symbol?

Attachments:

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[NextFEM Admin]

Now I can see your model. S22 stresses are depicted always in local coordinate system, the one of each element.

[Wu Tiesheng]

The force applied is 240 ton in Y direction, the total area is 300X210mm at fixed end, so the stress in the Y direction at that position will be about 38Mpa. I know the S22 is measured in local coordinate system, but how is the local coodinate system for a triangular element, say element Number 1096 in my model, and how to get the stress in a element in global coordinate Y?
Thank you for your help.
PS: area stress=element stress?

[Wu Tiesheng]

The resulted area stress is only -1.69e-1 to 9.36e-2

[NextFEM Admin]

Actually you have 2 nodal loads of 1200kN each on nodes 75 and 76. The resulting stress in the bounded edge is exactly 38MPa (you can check the reactions). The program does not include for now the showing of global stresses/forces.
Area stress displays local stresses only. You can display the local axes of each element by pressing the “Local axes” button.
I will perform further checks on your model, I’ll let you know.

[Wu Tiesheng]

Here is another example. Might the S11 small by a half?

Attachments:

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[NextFEM Admin]

We are doing cross checks with some shell models and I would include yours. I think you should wait for the next version for such things to be fixed.

[NextFEM Admin]

Dear Wu,
with the patch released today we solved the value of s11 (now sxx in the program) shell forces. Please find the patch on:

– for 32bit version: http://www.nextfem.it/patches/Patch-02-2017-32.zip

-for 64bit version: http://www.nextfem.it/patches/Patch-02-2017-64.zip

[Wu Tiesheng]

This patch is fantastic! Thank you very much.

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