Learning Forum

[Kirtan Sahu]

Hello everyone,
An "element distortion error" is appeared in solver output when I am trying to solve large deformation problem of hydraulic cylinder (Nonlinear buckling) by introducing geometry and material nonlinearity in the static structure analysis. I have taken two different material in the analysis, one is polyamide for guide ring and other is steel (Structural) for rod and cylinder. The Isotropic material hardening properties are taken for the analysis.

When the rod is coming in contact with guide rings and gland of cylinder, the element becomes distorted every time.

I am unable to obtain the convergence.

Can anyone please help me to get the solution?

Thanking you in advance

[Akshay Maniyar]

Hi Kirtan,

Please check the below video on the element distortion issue and try the methods mentioned in the video.

How to Handle Element Distortion Errors in Hyperelastic Materials — Lesson 3 - ANSYS Innovation Courses

Thanks,

Akshay Maniyar

[Kirtan Sahu]

 Thank you Mr. Maniyar for your kind response. 

I have already watched this Innovation courses and implemented the all possibilty they have mentioned. I doubt that the material properties I am taking for Guide rings (Seals) i.e. a polyamide materail (Polymer). Which has 2.5 Gpa of modulus of elasticty and poissions ratio of 0.39 with yield strength of 60 Mpa and Bilinear istropic hardening is taken with 0 tangent modulus (Elastic perfect plastic behaviour).

Can I use the guide ring as hyperelastic material to use the Mooney-Rivilin or Neo-Hookean paramters? (Is it correct to use polyamide as a hyperelastic material because its yeild strength and compressive strength is too high in comparision to hyperelastic material)

I have also tried to get best meshing quality, eventhough i am not getting the converged solution.

Please suggest me If i am missing anything else. 

[Akshay Maniyar]

Hi Kirtan,

Do you have test data for the material which you are using? 

Try using linear elements with a direct solver and make sure that your contact and target side are correctly selected.

(672) Designating the Contact and Target Sides Properly — Lesson 1 - YouTube 

Thanks,

Akshay Maniyar

[Kirtan Sahu]

No, I dont have any experimental tested data, I have taken the nonlinear properties of structural steel (Structural steel NL) from the engineering data with one change of yield stress from 250 Mpa to 360 Mpa.

I watched the video and implemeted it carefully, but still I am getting the same problem. 

Here is one more problem arising i.e. penetration between two bodies, but i removed that problem by selecting the frictional conatct with contact treatment "Adjust to touch" option. (Does contact status also create element distortion? because I think there may be some mistake I am doing)

[Akshay Maniyar]

Hi Kirtan,

You will need more details to correctly model the material which you are using.  Also, can you share the screenshot of the contact settings you are using? High penetration or continuous change in contact status(chattering) can create issues.

Thanks,

Akshay Maniyar

[Kirtan Sahu]

Ok, thank you. I will try to define proper material properties.

Yes, I always recieve a warning of aprupt contact changes. 

"Contact element 569863 (real ID 15) status changes abruptly from no-contact -> contact (with target element 540864)." 

"Contact element 684247 (real ID 34) status changes abruptly from contact (with target element 685459) -> no-contact."