TAGGED: dynain, offset, prestress, shell-elements
-
-
July 30, 2025 at 3:36 pm
Jérôme RENAULT
SubscriberHello,
Further to my question regarding access to the AWG group pages, I'm getting the input files presenting a possible workflow for obtaining the initial stress state of a rotating engine part (described in § 5.1.1 and § 5.1.2 of the document LS‐DYNA® Aerospace Working Group "Modeling Guidelines Document" version 24.1).
I'm doing the same thing with my model, but I'm unable to obtain a steady state for my rotating part at the end of the second step. The main difference is that my model includes *ELEMENT_SHELL_OFFSET elements. So, I simply modified my input file by replacing the *ELEMENT_SHELL_OFFSET elements with *ELEMENT_SHELL elements, and the behavior seems much better, except for the triangular elements, which still don't reach the steady state.
Two questions at this point:
- Is it possible to use a prestress analysis following the workflow presented in the AWG document with offset shell elements and enabling additional options ? I need to use shell offset element as I will work with composite parts modelled with ACP.
- How do I handle the problem with triangular elements? (My part is a cone, which will be difficult to mesh with only quad elements, but not impossible, I admit.)
Best regards,
Jérôme
-
August 4, 2025 at 9:07 am
Jérôme RENAULT
SubscriberTo add some information to the topic ...
I try the second procedure which involves the dynamic relaxation. I get the same issue with offseted elements. Nevertheless, once applied on non offseted elements, the results is acceptable with the triangle shaped elements (no stress concentration and/or discontinuities around) compared with the first procedure.
By the way, the two questions of the first messages are still open.
Best regards,
Jérôme
-
August 5, 2025 at 5:36 am
igandiko
Ansys EmployeeHello, is it possible to share your files, perhaps through a support case? Have you tried running the latest version of the solver? Please check if adding drilling stiffness stabilization using DRCPSID in *control_shell helps (https://lsdyna.ansys.com/wp-content/uploads/2025/02/drilling-rotation-constraint-for-shell-elements-in-implicit-and-explicit-analyses.pdf).
Note that NLOC affects the stiffness of built-up section (overlayed elements). “[NLOC] Affects stiffness of a “built up” section. For example, two shells overlayed using the same nodal connectivity and NLOC=0 will have stiffness equal to the straight sum of the 2 shell stiffnesses. If they’re offset using NLOC=1 and NLOC=-1 respectively, the bending stiffness is increased in accordance with a net section thickness of thick1 + thick2.”
If dynamic relaxation with non-offset triangular elements provide reasonable results, please check the difference in results at t=0 with DR phase vs. implicit pre-stress analysis. Since the pre-stress analysis is implicit, I would follow the implicit guildelines and also turn on implicit accuracy flag. Note that you can also run implicit dynamic relaxation in the 2nd procedure for comparison.
-
August 5, 2025 at 1:42 pm
Jérôme RENAULT
SubscriberHello Igandiko,
I've tried your various suggestions (except a test with the last version, as I can only run 202R2 on my server) ... without success.
It's possible to share my files; please let me know how to proceed (maybe with customer support space page ?)
Best regards,
Jérôme
-
August 6, 2025 at 5:25 am
igandiko
Ansys EmployeeIf you're able to create a support case on Ansys customer support space, that would be ideal. Please let me know if you can.
If you cannot create a support case, then please email the files to support@ansys.com (along with this forum link) and request them to forward the query to LS-DYNA team. Thanks!
-
August 6, 2025 at 8:44 am
Jérôme RENAULT
SubscriberHello Igandiko,
No problem, I open the case 00437219
Best regards,
Jérôme
-
-
-
August 6, 2025 at 3:00 pm
Jérôme RENAULT
SubscriberAt the same time, I'm trying to find a solution on my own. Regarding point 2 and the triangular elements, activating the OSU option in *CONTROL_ACCURACY is a good solution. The triangular elements no longer evolve during the rotation phase until an external load is applied, of course.
Best regards,
Jérôme
-
- You must be logged in to reply to this topic.
-
3792
-
1388
-
1188
-
1095
-
1015
© 2025 Copyright ANSYS, Inc. All rights reserved.