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  1. Hello, I was wondering what effect the N1a, N2a, N1b, and N2b properties have on the solution of a 1-dimensional case. For instance, if I specify the stress recovery points and also specify the location of the neutral axis relative to the centroid, does it have an effect on the recovered stress of the CBEAM element? I am running a curved beam where the neutral axis of the element is not on center, but the neutral axis property shift doesn't seem to make any difference when it comes to recovered stress. Any help would be appreciated. Thanks. SOLVED: Always check your element orientation. D'oh.
  2. Hello Everyone, does anyone know if there are any 1D elements that formulate stress based on the Winkler-Bach curved beam theory? CBEND in Nastran wasn't sufficient so I'm reaching out. Thanks.
  3. Since he gave you element try Tool -> Find -> Elem (by ID) -> 715 That should give you an element with (it sounds like) one end connected to the independent node and the other to the dependent node. At that point you can use Tool -> Delete -> Load and select the SPC at the dependent side of the element and hopefully that takes care of it.
  4. Can anyone tell me how to 'radially' offset a 1D element. I'm attempting to do an analysis where the neutral axis and centroid of the beam are not coincident. Thanks.
  5. Hello Everyone, I was looking for support with my FEA model. I don't have any pictures at the moment but hopefully I can explain what's going on and get some models/pictures later. Problem Statement: A curved beam with section centroid at a 6 in radius from a centerline spans 180 degrees and is fixed at one end while an 8000 in-lb moment is applied at the other. What are the stresses on the inside and the outside of the beam? Compare rectangular, circular, and trapezoidal sections with constant cross sectional area. Approach: I imported the arc from a simple iges definition file. I then line mesh with PBEAM elements. Cross sections have been defined correctly in the beamsection collector. Steel material has been generated. Properties for the sections have been created. This property is assigned to the mesh. Loads are put in their separate SPC and MOMENT load collectors. These collectors are passed to the SPC and LOAD parameters of the load step. Optistruct runs and produces the h3d file. Results: For some reason the stress at recovery points C and E for all elements are equal. This doesn't seem right to me. I would like to think that not only would the stress vary from recovery point C to E, but it would also vary (and increase) as the constraint is approached. However, the displacement of the elements and magnitude of said displacement DOES look correct. Can anyone provide insight as to why the SAMAX and SAMIN are equal for all the elements in this mesh? Thanks. EDIT: I've uploaded the result. The BCs are fully fixed on one end and 8000 (in-lbf) applied to the other end. Element is CBEAM with round section of radius 0.97. I'm using units system inch-slug-second. Can anyone help me out here? I'd upload the model file as well but apparently I'm not permitted to upload it.
  6. BUMP. Got the contact analysis to work with a non-realistic interference of 1mm which led to large compliance warnings. That was fine, but now I'm trying to do a real test case. I have some housing geometry and a small insert fit together. I'm receiving two errors and no results. I have an interference of 0.1mm and a mesh size of 0.001 in. Can anyone guide me in these errors? I can also supply the model if needed. Not sure what I need to do to fix this. *** WARNING # 2616 Slave and Master for CONTACT interface 1 point to the same set or surface. This self-contact may result in poor quality of contact elements, redundant contact conditions, and patchy pressure distribution, especially on curved contact surfaces. Also, pre-penetration condition will be ignored for this CONTACT interface (to avoid self-compressing the bodies due to false pre-penetrations). *** WARNING # 2625 CONTACT interface 1 includes areas that have self-contact condition and apparently pre-penetrations. To avoid detecting false pre-penetrations (which may appear across thin solids with self-contact on both sides) declare SRCHDIS smaller than minimum thickness of respective solids. Or, if it is known that there are no true pre-penetrations in self-contact areas, use CONTPRM,SFPRPEN,NO. *** ERROR # 941 *** NON-CONVERGENT NONLINEAR ITERATIONS FOR SUBCASE 1
  7. Let me get this straight. After reading the book about contact, I think I might know how to do this a little better, but I need to know if this is the correct approach. Real Problem Definition: I have two components. One is cooled and the other is heated before they are slipped together and brought to room temperature. At room temperature they expand and interfere resulting in contact pressure between the two components. Simulation Approach: Model the inner component at it's cooled state and make sure to define it's temperature at the cooled state and impose heating to room temperature. Define contacts on the interfering meshed surface of the inner component. Model the outer component at it's heated temperature, define it's temperature as hot and impose cooling. Place contacts on the inner surface of the outer component so that penetration cannot occur between the mating surfaces of the two parts. (Make sure to constrain at least one node on each part and attempt to minimize constraint influence on contact pressures at the mating surfaces.) Can anyone confirm that this simulation approach is correct? Update: I'm going to try just meshing and creating contacts that have interference between the two parts. Not sure if Optistruct will do this or if I'll have to use RADIOSS but I'll report back.
  8. Good Afternoon all. I'm looking for some guidance. I would like to run a simulation in which I can determine the contact pressure and the stress between two 3-dimensional parts. I'm not familiar with contact mechanic simulation and I am not interested in transient forces. I would like to know stresses and deflections of both parts, post-assembly. I presume I can do this with the Optistruct implicit solver but I'm not sure how to setup the contact card. Can someone walk me through the pre-processing part of doing a press-fit analysis with Optistruct? I can provide geometry and boundary conditions, but I'm lost when it comes to contact and Optistruct capabilities. Thanks.
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