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Strange bolt deformation in bolt pretension analysis

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Old   May 18, 2018, 05:45
Default Strange bolt deformation in bolt pretension analysis
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Dear All.
I am facing strange deformation of a bolt with pretension in ANSYS Workbench 16 Static Structural module.
There are two similar simulation with small changes but results are absolutely different. See picture1.
In both situations there is 'bonded' contact between bolts and base (bases are invisible in picture1)
I cannot figure out why deformation of the bolts on the right side is unrealistic while stress is pretty the same for both cases.
Could You possibly tell me where the problem is?
Have a nice day.
Sheaker
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Old   May 19, 2018, 08:39
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More information is needed to fully understand what is going on in the model.

1) What are the changes you made?
2) Check force reaction and elongation for the bolts (after pretension load step and after external load). Is it same in both analyses?
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Old   May 19, 2018, 09:27
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Hello. Thank You for Your reply.
I am sorry I have not been precise enough. The case is not to make them both look the same but to remove step in deformation. I have understood why there is such a step in deformation:



1. There were no pretension force on the left image (force 0 N and lock) that's why there is no step in deformation.
2. There were pretension force on the right image (force 2500N and lock) that's why there is a step in deformation of a bolt. I think that is how ANSYS apply pretension (It cuts bolt in some point and adds forces to create pretension; see image1).


It would be great if I could get rid of it somehow to see real bolt deformation.



Have a nice day,
Sheaker
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Old   May 20, 2018, 09:16
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You could try using user-defined results (subtract ls1 deformation from ls2 deformation).
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Old   May 20, 2018, 10:00
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Hello. Thank You for Your reply.
I'm going to try this within hours but as I understand I will lose deformation changes caused by pretension forces?
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