# Vincent377

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1. ## Bolt Connection out of: RBE3 + CROD

Hello, thank you for your reply. I know the RBE2 element is the usual way to define a bolt, but induces unwanted stresses in my model In my model the bolt hole is deforming through thermal loads (like an oval if you amplify 100x). Through simulating the bolt with a RBE2 spider (even with CTE assigned), stresses are induced which are not valid in my opinion, because in reality the diameter of the bolt is smaller than the one of the hole - so in reality the hole can deform a little bit. So the RBE2 spider does not allow the hole to deform. Thats why I want to use the RBE3 spider, then the center node is the dependent one (problem: center node has DOF 4/5/6). Now I am wondering, what element do I use for the connection between the two RBE3 spiders. As I understood I cant use an RBE2 element, which would be the most conservative, because then one center node is 2 times dependent and one is dependent and independet at the same time). So I was thinking about the CROD element, which seems to be similar to a real bolt.. What do you think? Thank you EDIT: Additionally I need to say: the material is ceramic, so the stiffness is higher than the one of the bolt. A RBE2 with indefinit stiffness as bolt is a problem. EDIT2: As the CROD element can not be loaded perpendicular but axial it is useless for a bolt. Instead I did it like this: RBE3 spider, RBE2 element, CBUSH element (with super high stiffness), RBE2 element, RBE3 spider. At least it can be loaded perpendicular now, but i am not sure about the stress validation..
2. ## Bolt Connection out of: RBE3 + CROD

Hello, what do you think of the idea to simulate a bolt connection of two holes with a specific stiffness made out of a RBE3 spider + CROD element + RBE3 spider? The lenght of the CROD element represents the tolerance between the hole and the bolt. Is the solution representative?
3. ## Assign Coefficient of thermal expansion (CTE) / temperature to RBE2 Element

Thank you. What is the difference between both?
4. ## Assign Coefficient of thermal expansion (CTE) / temperature to RBE2 Element

Hello Rahul, i am using the latest version of optiscruct. Anyway, I solved the problem by repeating every step properly and the RBE2 element is expanding now. It seems like works exactly like I described. (assign alpha by card edit -> assign initial temp -> assign increased temp -> solve). Another question: As I need to card edit every rbe2 spider, is there the possibility to card edit all the elements at once? When I selected mutiple spiders and try to edit it, I get the message: "No valid entities were selected" Thank you for your help.
5. ## Slide Contact between edge and solid face / Autocontact

Thank you Ivan, you helped me a lot.
6. ## Assign Coefficient of thermal expansion (CTE) / temperature to RBE2 Element

Hello, I am using Optistruct for my thermoelastic simulation. I am investigating the thermal expansion of some components connected with RBE2 elements. I am trying to assign CTEs to RBE2 elements. I have read that this is possbile by doing a card edit (screenshot). After that I have chosen the nodes of the RBE2 elements (2 rigid spiders and a RBE2 connection for a bolt) and assigned the Temperature increase (BCs -> create -> Temperature). I have included in the load step the initial temperatures for all nodes with subcase TEMP and the increased temperatures with subcase TEMP_LOAD. Unfortunately the RBE2 element is not expanding. Surrounding solids and shells are normally expanding. I guess that the CTE is assigned, but somehow the RBE2 element does not know, that its temperature increased... Does somebody have experience with that. Thank you for your help. Vincent
7. ## Slide Contact between edge and solid face / Autocontact

I have a new problem now: I have a lot of components for which I need to define several contacts. So I am trying to use the autocontact function. Unfortunately not every contact is detected. How is the AutoContact working so I can optimize the parts that AutoContact is working properly? I am using Shell thickness as Contact Tolerance type and the shell thickness is defined properly. Most of the problems occure when tetra solids and midsurface meshes should be connected (See attached picture). Thank you for your help. Vincent
8. ## Slide Contact between edge and solid face / Autocontact

Hi Ivan, thank you very much. Very helpful!
9. ## Slide Contact between edge and solid face / Autocontact

Hi Ivan, thank you for your help. It is working now. But I do not really understand the difference between the master and the slave. Why is it not working when I am using the edge as master?
10. ## Slide Contact between edge and solid face / Autocontact

Hi, am trying to create a perpendiculat contact between an edge of a 2D Midsurface mesh and one face of an solid. I am proceeding the same way, like it would be a contact between to parallel faces, but somehow its not working. Thank you for your help and have a good day!
11. ## thermal expansion w/ bolt connection -> stress

Hello, I am having a problem solving following problem: I have an ceramic component (3D mesh) bolted (1D -> connector -> bolt) with an aluminium shell (2D midsurface mesh). I give both a temperature increase of 100K. I created a FREEZE contact between them. I want to calculate the stresses due to different thermal expansion. As both parts are bolted and fixed and both are trying to expand there should be stress. Optistruct is calculating stresses of 596 MPa. Thats not possible as it is way to much. Aluminium stretches irreversible at 20 MPa. Is it the wrong way to solve the problem? I am new into Hyperworks. Thank you a lot for your help!
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