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Found 5 results

  1. Hi everyone, I am writing here hoping someone can help me with the following problem. I have a plate which is connected to one end of a flexural spring (0.8mm thick) through FREEZE contact (please see picture below). The other spring end is fixed. I have used 2 loadsteps to perform this analysis: The plate has to translate downwards of about 1.4 mm. LGDISP non linear static analysis activated. From the position reached in the previous point, the plate must rotate about the X axis of an angle 0.25° (DOF4).LGDISP non linear static analysis activated. All displacements have been enforced through SPC. Picture of the model: I have used CNTNLSUB in order to make one subcase follow the other. Unfortunately, from other threads in this forum, I seem to have guessed the 1st loadstep loads (SPC enforced displacements in this case) must be enforced in 2nd loadstep as well. This proves to be impractical, since my final goal is to simulate bending+torsion in the flexural spring. In fact, I cannot impose the desired rotation in the 2nd loadstep because the plate has to be forced to translate downwards like it is in the 1st loastep. I am attaching my file in order to get the matter as clear as possible. Thank you in advance for any help you will wish to provide. Best Regards Matteo Spring_Plate.fem
  2. Guest

    Nonlinear continuation

    Hi sir, I am very new to Optistruct and tried doing multistep analysis -like carrying the 1st step result to next consecutive steps, but results does't seem to carry forward the previous step results. solver type used - generic type, and also tried doing in NLstatic. can you suggest some useful tips, Thanks in advance.
  3. Hello, 1. I try to simulate a high detailed model of a screw with OptiStruct. Currently the screw will be pretensioned with the pretension function and in the next LoadStep it will be rotated. Now in the following LoadSteps i want to add enforced displacements on the Contact Surface of the screw head. My main problem is the sequence with the enforced displacements. How can every single Loadstep use the results of the previous Loadstep (Stress, Displacement, Contact...)? For the pretension Loadstep i use the function STATSUB(PRETENS), but i dont know if the displacements will be freezed for the next Loadstep and i use CNTNLSUB to consider the contact. 2. The next poblem is, how can i enable/disable contacts between severally LoadSteps without using MODCHG (Older Version of OptiStruct than 14.210)? Thanks!
  4. Hello Everybody, I've been struggling with NLGEOM analysis with CNTNLSUB since yesterday and I still don't understand a few things. What I want to do is to load a steel plate for 1 s and in the next step to unload it. I load the structure with one Force in Z direction NLOAD in the subcase 310. NLOAD activates TABLED1 where the basic linear function is defined x=0, y=0; x=1, y=1. In the next subcase 311 I use CNTNLSUB = YES, the same SPC and the same NLPARM. The nonly difference is that I do not define any load, since it should be the step, where the structure is being unloaded. Below you can find the plots I got and short descriptions of respective graphs. On the Displacement - Force plot, you can see a discontinuity between the curve belonging to the SUBCASE 310 (loading) and SUBCASE 311 (unloading). What is more, the force increases in the second step despite the lack of any loading force. The force is being increased up to 8000 N, which is a doubled value of the load defined in the first step. On the Time-Displacement plot the curve is continuos. However, the displacement is being increased till the end of the simulation (as expected based on the graph Displacement - Force). The Time-Load graph shows discontinuity again. In the beginning of unloading step, the force seems to be 0 N and than in the next increment gets back immidiately to the value, as if it was being increased, according tothe linear function present in the loading step. I would be grateful for some hints / tipps / explanation, where I make a mistake and if it is possible to create a proper loading - unloading time dependent simulation in two subcases with use of CNTNLSUB. You can find my input-deck in the attachment. nlgeom_4060_H380LAD_0p6mm_1300_CNTNL_test_01.fem
  5. Hello, I have set a Nonlinear quasi static analysis (type NLSTAT) with two consequent load steps (using CNTNLSUB option). In my model two parts are gradually getting in contact (something similar as roller - plane contact), where also friction is taken into account. In the first step a radial force is pushing the roller towards the plane and in the second step additional lateral force is applied. Everything works fine, the results seem meaningful. Now I would like to set a first load step with contact type SLIDE and the second (continuous) load step with friction in contact. Is this possible in Optistruct? Thanks for your help! Best regards, Matej
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