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Found 133 results

  1. Hi, I've previously had help from one of your colleagues with my model for which they suggested I do a Mesh-->Check--> Elements-->Penetration as I had a problem with my slide contact surfaces. I fixed the majority of these penetrations with the auto manager (not all were fixed) and tried to relaunch the calculation. However, now my model does not manage to converge and I don't fully understand why, even after reading up on all of the input fields in the contact menu. Any help would be greatly appreciated (model is attached)! Thanks in advance. 151207_MD_01_A-42.hm
  2. Hello, I would like to calculate a contact between a sphere and flat solid block, pressed together under certain load. I am interested in the contact stress and precise contact area (I would like to compare the results with the analytical solution of Hertzian contact theory). Is it feasible to get the desired results with a non-linear quasi static analysis in Optistruct or shall I do it with Radioss? Additionally, what is the best way to obtain the final nodes in contact or even to fix them together and perform an additional analysis? Thank you for you help, Matej
  3. Hi, I've been trying to find the force required to create an interference fit between two parts. I'm fully constraining one of them, and placing an SPCD upon the other. The contact between the parts is a sliding one (I've tried different values of friction, but nothing seems to help). I'm using a non-linear implicit analysis. The solver gets quite far down the line, but then crashes at some point because it cannot converge. One of the parts begins to deform (as it is supposed to), but then the solver doesn't get any further. Chamfering the goemetry to avoid sharp edges helped some, but not enough. Any thoughts, or a location where I can share a large .fem file? Thanks, Jai
  4. Hi, I am doing a simple contact simulation in Radioss Bulk Data between 2 2D surfaces meshed with shell elements. The first surface is similar to an S-shaped extruded plate and the second one is just a rectangular surface near the s-shaped. Distance between surfaces is 0.1 compared to 0.5 el. size. Contact surfaces (near the gap) were created with the SURF card and it was ensured that their normals were pointing to each other. I want to do two consecutive subcases. In both of them the top of the S-shaped sheet is fixed. 1) The rectangular plate is constrained with some predefined distance (in my case, SPC with dof1=4 and all other dof=0), so it pushes the S-shape. 2) The plate goes back to zero and the S-shape should go back to the origin (or a bit less if there is plastic deformation). To do this I modified the constrained of the rectangular plate to have 0 for all dof for the SPC constrained. I also turned the CNTLSUB option on and put it to YES. However, it seems like the unloading does not start from the loading case and the plate just stays at zero. I have tried different contacts (initially SLIDE and then STICK and FREEZE) but the result was the same. Attached is also a sample file. Any help would be appreciated. Georgi Shell_Contact.zip
  5. Hello I am using RADIOSS to simulate a crash test which I have previously done. The trajectory of the impactor before impact is complex and requires several linkages and mechanisms to set up. The area of interest is the post-impact behaviour (stress/strain) on the target component, as well as the trajectory of the impactor. When I run the impactor by itself, to see the launch trajectory, I get a reasonable run time of about an hour. When I run the impactor with a simplified initial velocity + the target with all the contact and failure cards defined, I get a reasonable run of about 3 hours. When I run the full model: impactor with the initial trajectory + the target with all the contact and failure cards defined, I get a run around 12 hours to reach the impact, and another 12-24 hours to get results from post impact trajectory. I believe this is partly due the finer mesh required for the target model. I was hoping there is a way I can split the analysis in two, using the results from a the first as an initial condition for the second. Consider the following scenario: Model A: Simple model with only what is required to set off the trajectory of the impactor. The target is not modeled. Run from T=0 to T=T_impact. The run is stopped at the moment where the impact would have occurred. Model B: The target, with finer mesh and contact and fail definition is introduced, and the analysis is "RESTART" picking up from where Model A left off. In other words the target (with finer mesh) only appears just before impact onwards. This should theoretically cut down the majority of the analysis time. Is there a way to set up a RESTART file with introduction of new elements / properties / fail cards, and linking it to a "Stopped" run? I hope the diagrams attached illustrates what I'd like to do. Please let me know if there is a way to do this. Thank you. Best Regards, MN
  6. Hi, I would like to know, how to get the script to get the elements in contact (spotweld/tied) in dyna by giving only a node as input. The command file does not give clear steps except for *findmark elements 1 1 1 etc.. or findfaces for getting the solid weld element faces. I tried it manually but beyond getting the solid elements, I'm not getting the 2D elements which are defined in contact spotweld. What must I do to get them too ??.
  7. Hi, I am wondering if somebody could help me defining contact between to surfaces so that I can easily update the contact definition in the input file. The problem is stated as follows: I am pressing two beams together and would like to perform FRF modal analysis on the beams. With an optimization routine, I would like to update the contact definition between single nodes and surfaces to be either stuck, slipping, or not in contact, and match an experimentally obtained FRF. In order to solve this problem, I need to define the contact in a way that I can easily update the contact definition between single nodes and surfaces in the input file. In this initial analysis, I define the contacting interfaces to be stuck and am hoping to understand the input (.fem) file, hoping to be able to figure out how tho change the contact definition from stuck to slide within the .fem file. Attached are the .fem file and the .hm file. Could you explain to me the entries in the .fem file in: Line 61 (+ 21603 13616 13929 1) Line 1762 to 1778: How is contact defined here? Is it between the sets of nodes? Can I change that to single nodes? Is grid data the nodal position? Is CHexa Data the element definition? I hope this description is sufficient to help me solve my problem. Thank you, Kevin 170706_FRF_HZBeam_FullyStuck.fem 170706_FRF_HZBeam_FullyStuck.hm
  8. Hi together, i try to visualize the contact forces (normal and tangential) of a type 2 interface in radioss. Is there a engine keyword to visualize the contact force as Animation, so that one can see it in hyperview ? I use Interface type 2 with spotflag 20. This means, that a contact force is calculated in order to compare the result to the rupture criterium. I would like to visualize this contact force. Thanks in advance! Greetings, Sebastian
  9. Hi all I was watching a video on youtube , where the contact creation brings the user to choose among the Contact Type 7 or Type 11, but what I see in lower versions is just CONTACT, GROUND, CONVECTION ,...etc I would like to know how to choose the Contact type in versions 13 and lower
  10. Hello, I am doing a study inflating an airbag with a particular shape and there are a lot of contacts between surfaces, that I modeled with interface type 7. I have some troubles because there are some nodes that pass through master surfaces (even if the interface is activated) but then the contact is applied and the nodes can not pass through, creating high contact forces and reducing the time step. I wanted to use the control card DT/INT/DEL to delete the interface in those nodes, I fixed Tscale to 0.9 and Tmin to 1.0 e-4. When I run radioss, time step reduces up to 5e-5, some nodes are deleted but not those that passed through surfaces and have high contact forces. Any idea about how can I deactivate interfaces in nodes where the contact force is higher than a fixed value? Thank you
  11. Hello, I am trying to build a rigid mbd model with rigid bodies engaging in 2D rigid-to-rigid contact. I have defined curves where the contacts will occur, using the Add Curve functionality. Attached images 1.png, 2.png and 3.png from my curve panel, showing the settings I am using for all three contact curves. As you can see, in the Z direction, they all have the same value as 0. So they are indeed coplanar as they all line on the XY plane. I proceed to define a 2D rigid-to-ridig contact. Attached image, contact.png, shows my settings for one of the contacts I use. I have also made sure to correctly define the contact sides; so there are no problems there either. Finally, attached image, error.png, shows two of the error messages I'm getting. All my error messages are the same so I am only showing those two. It is telling me my curve graphics are not coplanar. However, what it seems is that they actually are indeed coplanar. I would be grateful for any help to fix this problem. Best regards
  12. Hello, I have been having issues with a model containing contacts and friction. The model is relatively straight forward, a multiple mast model with wearpads and contacts between pad faces and adjacent mast sections. When the contact is set to property type slide N2S, the analysis demands around 47GB for In-Core Solution. However when the type is set to static friction coeff = 0.15, the in-core demand becomes 80GB. The model on my pc then typically fails because MUMPS demands significantly more RAM. I've tried adjusting the search distance and using a PCONT card to define friction with little impact on MUMPS demand. Any suggestions? I currently have one PARAM card... PARAM,EXPERTNL,CNTSTB
  13. I have components in the assembly and i want to find the IDs of surfaces which are really close or almost touching other component. Is there any way to find out those details?
  14. Hi, I am having a radioss bus structure file with min. element size of 5 mm used for crash simulation and now I want to use the same file for static and non-linear quasistaic analysis in optistruct If I go to optistruct will all contacts be detected as it is in radioss and is recommended this way or generate separate file for it. As the structure size is large, meshing will take more time and thus wanted to avoid making new file. Thank you
  15. I've been recently working on a Knee joint model . I need to find the contact force vector between two particular components. I have been getting a lot of errors and unable to run the model. All the contact pairs and properly defined and I am able to generate all typical outputs except for contact output. please help me out. The output blocks defined so far are node and element outputs for all 8 components defined. Thanks in advance!
  16. Hello, I would like to do some lattice optimization in Hypermesh. However, I need to know if it is possible to have a different mesh size for the lattice sections compared to the solid sections. The way I understand lattice optimization in Altair is that the element size you mesh with originally will determine the average length of the lattice struts. For example; I tetra mesh my model with a size of 2, the lattice beams have an average length of 2. However, I would like to have a mesh size of 0.5 with lattice elements of length 2 (or vice versa). My game plan is to run a minimize compliance with volume fraction on my model with a penalization of 1.8 (low porosity). Then use the results of the compliance optimization to split my part into sections for a given element density threshold. I should end up with solids for the lattice elements and solids for the non-lattice elements. The lattice solid sections will then be filled with lattice beam elements from another lattice topology optimization. I want to remesh each solid individually for different lattice strut sizes and types. Contact surfaces will then be used to connect the solids together and then run the Lattice optimization. The end goal is to use mesh refinement on the non lattice sections to check the validity of my model as well as experiment with different lattice sizes. Any advice is greatly appreciated. -Eric
  17. Dear All, Please help me out with mentioned errors.
  18. Hello every body here, this forum is really helpful, just keep the good work ! I know that in general contact problem is non linear BUT i would like to know if it is possible to perform "linear analysis" with optistruct when the contact interface type is set to freeze or tie ? Thanks a lot. Best regards, GAYE
  19. Hi there, Is it possible to define an initial contact between to surfaces in HyperCrash, while running RADIOSS, so that there isn't neither a gap nor an initial penetration? Thanks
  20. Hello, everyone! I am a beginner for Hyperwork and using Optistruct to solve some problems. I have a question to define the contact between rule and cylinder just like in the picture. Because of the load in the middle both side of the rule will go up. How could i define this simple support contact in Optistruct? Thank you very much!
  21. Hi everyone, I'm trying to model a cylindrical section being held between a grip that tightens around it. When I look at each jaw however, I have a contact pressure concentration in one area and I can't seem to find out why. I'm using Optistruct V13 and I use the auto-contact tool to create the contacts between each component. I have checked for penetration between these components and there is none (there is between two other pieces but I do not look at these). I have quite a fine mesh as I'm looking at this specific area (mesh size 0.5mm). Does anyone know what I could do to get rid of this point? Could it be that these nodes are slightly irregular and 'sticking out' slightly from the component? Thank you for any help you may be able to give me!
  22. hello, everyone ! can anyone share the related Gallery model file ? (optistruct 14.0 new feature)
  23. Sir, I have a component which is an assembly of 3 different parts. It's a torsional vibration damper consisting of inner mounting part and outer rim both composed of metal which bounded by a rubber part in between them. I want to perform a linear static analysis of the assembly with loads applied on the inner part and constraints applied on outer rim. I have meshed each part with perfect alignment with the adjacent part mesh at the contacting surfaces (so that the each node at the contacting surfaces will be commonly shared by the adjacent parts). The parts are meshed with solid mapping of 2nd order quad elements. Also I have checked that there are no free edges in between the parts contacting region. Being different parts (material), I have applied separate property collector to each one of them. What else should I need do to avoid an unconstrained linear static analysis simulation? I mean how do I convey the software (solver) that the inner and outer parts are bound mutually through the rubber?
  24. Hello, I want to simulate the following mechanism I need the orange pin to slide trhough the green slot when the green slot moves due to other machanism movement. This is the configuration of contact that I used: Nodes on the all arround the slot are the slave and all of the pin elements (membrane of a 3D) is the master. And the results are these: what do you suggest i can do? What is wrong with my contact card, or what other approach do you suggest? thank you for your itme.
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