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Found 32 results

  1. Hi, I ran a modal analysis of my model and somehow the MODAL EFFECTIVE MASS exceeds the total mass in some cases. I assume that this is not how it should be? Can anyone help please?
  2. Hi, How can i extract results from an modal analysis? I want something that looks similiar to this: Right now I can only find the modes in the Output file, but the percentage of mass would be helpful. Thanks in advance.
  3. Good afternoon! I was wondering whether there was some way to terminate a FEM modal port in a load matching the characteristic impedance?
  4. Hello everyone, I'm trying to set up a direct transient analysis of the beam you see in the picture below (simplified geometry): The beam is meshed with tetra elements. On top the beam is constrained in all dof. In the middle of the beam is a hump and the mass of it has an influence on the eigenfrequency of the beam. At the lower end of the beam a periodically enforced displacement in the range of the eigenfrequency (3 kHz < f < 4 kHz) of the beam is applied. With the FE analysis I want to get information about the following questions: What is the stress at the top of the beam? Later I would like to get information about fatigue. What is the eigefrequency of the beam? What is the exact displacement of the hump in the middle of the beam when a certain displacement is applied at the lower end with its eigenfrequency? So far I've tried to adapt the tutorial "OS-T: 1310 Direct Transient Dynamic Analysis of a BracketOS" to my purposes but I have problems with applying the periodically enforced displacement. Can someone tell me what the best way is to realize this problem with optistruct? Thank you in advance Felix Link to the tutorial: https://altairhyperworks.com/hwhelp/Altair/2017/help/os/topics/solvers/direct_transient_dynamic_anlaysis_bracket_r.htm#direct_transient_dynamic_anlaysis_bracket_r
  5. Hello Experts, I am trying to perform a complex eignevalue/ brake squeal problem on Optistruct 11. The error that i am getting is as follows:- *** ERROR # 1461 *** Card "STATSUB(PRELOAD)" is not allowed for this subcase type. I have used Generic as a solver instead of Modal Complex Eigenvalue as it doesn't support Statsub. Can anyone please explain how to resolve this issue. I have been following quite a few tutorials and have followed exactly the steps mentioned but cant get around this error. Thanks
  6. Hello, I am trying to do a linear buckling analysis on a telescopic mast of 12m. The assembly has a blend of 1D, 2D & 3D elements followed by contacts. Anyways i have taken care of all the parameters like element quality, free edges, T connections etc. As usual, I carried out a FREE-FREE Analysis first followed by MODAL & then a STATIC Analysis (Gravity Loading). All the rigid body modes have been eliminated and my modal frequency are as follows 0.676, 0.677, 6.75, 6.78, 19.53, 19.70, 39.55, 39.71, 45.30, 59.39. I don't know why the modal frequency fetched such initial low values and how to interpret the intermediate frequencies occurring in pairs? The Static Analysis results are also satisfactory with a max displacement of 0.235 mm (Mag) and stress of 11.34 MPa.The stress flow pattern is also satisfactory. Now when I simulate a linear buckling analysis I get this error: ERROR 165- Gram-Schmidt reorthogonalization did not converge. This is caused by ill-conditioning of the shifted matrix in Lanczos run. I have gone through a few other posts in this forum which said to remove rigid body modes, but i don't have any rigid body modes as such. And it is quite evident from the static analysis that my model is well connected and contacts are acting. Could you please let me know how to resolve this issue? Thank you.
  7. can anyone explain Mode Super position method briefly ?
  8. Hi , I am having following queries while trying Modal correlation option in Hyper view - NVH. 1. I am facing error while using transformation option in Hyper view - NVH - Modal correlation. Pls find the below image & help how to sort out. 2. How to use tolerance option in Node pairs menu. I could't able to get the values in the below table Regards, Arul
  9. Hi, I'm getting the following error while trying to run a modal analysis in Optistruct. Could anyone help me make sense of this? ANALYSIS RESULTS : ------------------ ITERATION 0 *** ERROR # 825 *** The run will be stopped due to the previously encountered fatal error from the element generation routine in preprocessing: Number of failed elements = 1 Last encountered error code = 15 The previous error is encountered in subroutine prpdrv. This error is issued in subroutine elqcdrv. *** INTERNAL PROGRAMMING ERROR # 8006 *** Data block effmas not in data manager dictionary. * DATAMANAGER ERROR in subroutine "locateit". **** Error 8006 in datamr() during "locate" operation. Data block name "effmas". Current memory allocation 8166 MB, Unused memory 6248 MB, Number of blocks: 280 used, 5 free. Call arguments 0, 0. *** INTERNAL PROGRAMMING ERROR # 8020 *** Failed database modify command: Locating array effmas.' * DATAMANAGER ERROR in subroutine "LOCATE". This error occurs in module "wrtdrv".
  10. Hi, I am trying to change the animation mode in hyperview to "Set Modal Animation Mode" using tcl command.will be great if some can help me out. Thanks in advance Regards, Emil
  11. Hi, I'm trying to run a fatigue analysis using acceleration as load, but I don't know how to set the FATLOAD card with an acceleration load. My objective is to simulate a shacker test and verify the life and damage that the part will get when vibrates in 1G acceleration. Modal and frequency response analysis are ok, my only problem is with the fatigue analysis. If anyone knows how to proceed, please let me know. Thanks!
  12. Hello, I'm having troubles setting up a topography optimization using plies. The model is a heatshield with 3 different layers(thickness) and Im using PCOMPP card as property to them. I believe that the optimization settings are correct, because I had already used the same settings in a previous single layer model and it went ok. But when I try using stacked layers something goes wrong. Im getting the following error: *** ERROR # 79 *** DTPG data does not create any DVGRID data. There are no free referenced GRIDs. There may be no elements associated with the PSHELL data. LOAD or BOTH may be specified and all grids may be loaded. BC, SPC, or BOTH may be specified and all grids may be SPCed. Any thoughts?? If there is some paper relating modal+plies+optimization that can be provided I'll appreciate. Thanks in advance.
  13. For Modal and Stiffness(torsional and bending) of ladder frame chassis, is there any significant difference in results when I use stick contact between frame and cross-members or when I use shell/rigid weld elements to connect cross-members and long members?
  14. Hi all, I'm working on a frequency optimization problem, where I want to minimize certain modes, maximize certain modes, and maintain a single mode within a certain range. Specifically: - reduce all modes under 10,000 Hz as much as possible - maintain a single longitudinal mode between 10,000-11,000 Hz (the 'working' mode) - maximize all modes above 11,000 Hz as much as possible Basically, the goal is to create high separation between the working mode and surrounding modes. There's a few key challenges here: 1) It's difficult to know how many modes exist under 10,000 Hz as the optimization runs. For example, ignoring rigid body modes, let's say there are 6 modes to begin. If I target the 6th mode to be reduced, it is sometimes eliminated entirely as the structure changes, which results in an error because the mode no longer exists, and the analysis stops. If I target the 5th mode instead, the 6th mode may not be as effectively reduced. Is there a way to perform a modal analysis in which the search decreases in frequency (i.e. it begins at 10,000 Hz and finds the first mode under)? This would solve this issue at least, as I could always target the first mode. Or are there other options? 2) Another problem is that it's difficult to maintain the working mode within the constraints. As soon as it goes below or above the range, the analysis again stops as there is no mode in the specified range. 3) A third problem is identifying the mode in 10-11 kHz as a longitudinal mode. Although it may begin as a longitudinal mode, that can quickly change to bending or torsional as the optimization runs. In the past, I've performed a harmonic analysis to excite this mode, and then try to maximize the displacement. This tends to point the optimization towards a longitudinal mode, since it resonates with the harmonic input force and creates larger displacements. However, I'm looking for a simpler method, if there is one. Does anyone have any ideas on how to formulate this problem for OptiStruct/HyperStudy? Much appreciated! albatrossor
  15. Hello, I am using Optistruct to numerically calculate some FRFs. I have test data to validate my numerical results. Measured test data is an FRF data in the form of Inertance (acceleration/force). I see that there is a big gap in frequency components' amplitudes between the measured data and numerically calculated data, though calculated and measured natural frequencies align very well. I have followed the modal frequency response tutorial and nowhere in the tutorial is it shown that we're specifically selecting the type of FRF we're wanting (e.g. inertance or mobility or receptance). GLOBAL_OUTPUT_REQUEST is used with DISPLACEMENT enabled and that makes me think that, what I am calculating in Optistruct is Receptance and not Inertance. I tried to request ACCELERATION instead of DISPLACEMENT, but ACCELERATION doesn't let me select the output node set which I used for DISPLACEMENT. How can I make sure in Optistruct that the numerical data I'm getting is inertance and not mobility (velocity/force) or receptance (displacement/force)? Best regards
  16. To evaluate the response of a structure submitted to a periodic sine wave force in the time domain, can I define the OptiStruct loadstep as "transient direct"? Does "transient direct" and "transient modal" differ in computational cost only?
  17. bmech


    Is there any tutorials or reference exercise in order to learn MFLUID in optistruct for modal analysis? Regards
  18. Dear I have an assembly that I have decided to divide into 5 subassembly (A,B,C,D,E) Using Craig-Bampton method, each of this assembly has been condensed (h3ddmig but I have tried with .pch also) using only the visualization of plot elements (plotel3 and 4) In the master model, the residual nodes (aset) of each assembly are connected each other using beam and rod with different dof (in order to simulate a mechanism) and a rigid with the master node grounded and I asked for a certain number of modes (normal modes). NO ERROR in the output file but neither results (h3d) but a serie of OSxxxx_er.rs~ This is the what i have in the output: Lanczos solver warnings for eigenvalue subcase 1. - At some point in the process, an inconsistent inertial count was found. This implies that some of the calculated frequencies may be inaccurate, especially the duplicated frequencies. To avoid this, specify both bounds and keep the bound away from the currently calculated frequencies. *** warning *** the rayleigh quotient x'kx / x'mx for the 1-th eigenvector does not match the computed eigenvalue lambda ( 1): -9.86447590101136D-06 x' k x : 5.21843506993811D-05 x' m x : 1.00000000000000D+00 discrepancy : 6.20488266003924D-05 *** warning *** the rayleigh quotient x'kx / x'mx for the 2-th eigenvector does not match the computed eigenvalue lambda ( 2): 4.00771124962063D-05 x' k x : 7.34242225598191D-05 x' m x : 1.00000000000000D+00 discrepancy : 3.33471100636129D-05 *** warning *** the rayleigh quotient x'kx / x'mx for the 3-th eigenvector does not match the computed eigenvalue lambda ( 3): 5.23449252423092D-05 x' k x : 1.36220146252925D-04 x' m x : 1.00000000000000D+00 discrepancy : 8.38752210106160D-05 eigenvalues and eigenvector residuals ------------------------------------- eigenvalues norm of estimated (radian/sec)**2 residual accuracy --------------- -------- --------- -9.86447590101136D-06 2.4225D-06 2.4225D-06 4.00771124962063D-05 1.2132D-06 1.2132D-06 5.23449252423092D-05 3.9402D-07 3.9402D-07 *** Warning for eigenvalue subcase 1 Number of modes requested = 3 (0 = all) Number of modes found = 3 warning status index = 10 maximum relative discrepancy = 0.83875E-04 (Scratch disk space usage for starting iteration = 1 MB) Any suggestion? Regards
  19. Hi! I tried to make a modal analisys of a model composed by many components and different materials. The result shows only one component moving and the others no, it seems that each component is not in contact with the others. What's the error that i made? Grazie
  20. Dear all, I am trying to output modal strain energy for a component. Despite having followed the manual carefully, I am still unable to see modal strain energy results in the h3d file when I view it on Hyperview. Though I can't share my model files due to privacy, below images show the settings I use for the load step. I also show the mode set settings, as I intend to output modal strain energy only for the first mode. What I basically do is I define a load step of the type freq. resp (modal) with a method (struct) that is EIGRL (the first 15 modes, excluding rigid body modes). No spc. Analysis type set to MODES. For OUTPUT, I select only MODALSE. Please see below images for details on the settings I am using. I have also tried adding an OUTPUT control card with settings H3D, ALL, BYITER. Unfortunately, I was still unable to print modal strain energy results in the result file. I would appreciate any information on how I can print modal strain energy values in the result file. Best regards, Deniz Bilgili Note: I am using Hyperworks 17
  21. Hi, Is it possible to do Modal analysis for rotor with shaft ( using 3D elements) using following example in optistruct?. or it is applicable for only 1D elements problem?? I have tried . But it is not working for 3D problems OS-1372: Rotor Dynamics of a Hollow Cylindrical Rotor
  22. Hello everyone, I want to do a prestress modal analysis? However, I don't know how to set up the case. Is there any example? Thank you Best Wishes Roy
  23. Is it possible to do operational Modal Analysis in optistruct?
  24. Is it possible to define the contact ( surface to surface , single surface contact) between components in vibration analysis ( Modal , FRF) in optistruct?
  25. Hello Everyone! I am doing a response spectrum analysis an like to retrieve a eigenvalues and vectors from normal modes analysis which has already done. I hav saved the eigen value using EIGVNAME = modes and EIGVSAVE = 100. The file is has saved as modes.100.eigv. While doing RSPEC, I retreived the eigv using EIGVRETRIEVE = 100 and same EIGVNAME. But Solving throws an error as, *** ERROR # 372 *** Number of MPC constraints in file modes.100.eigv 474 does not match current value 0. Can Someone figure it out . Thanks in Advance -RathinaVel
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