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Found 15 results

1. ## Explanation for very large maximum constraint violation % in the first iteration

Greetings, I am performing a free-size optimization (iteration summary given below) and trying to understand the explanation behind maximum constraint violation %. So far the following is clear: If constraint violation > 1% : status is V (violated) If constraint violation < 1% : status is A (Active) Large constraint violation % could mean that the constraint is too tight and that the problem itself is ill-defined. the difference between regular and soft convergence is understood as well Problem definition: The thickness of an insert is defined to be the DV. Two stress constraints are defined. The objective is a stress minmax formulation. Question: I am unable to figure out whether the large constraint violation % implies a critical issue. If yes, how does one rectify the problem? Insert_FEM_y.out
2. ## lgdisp Nonlinear large displacement direct transient analysis problem

Hello, I work on a suspension construction. I have done done a static analysis due to vehicle mass (I managed to do both linear and lgdisp nonlinear). However, I also need to perform a dynamic analyis due to riding over an obstacle and I have encountered few problems with the simulations: 1) As an excitation I use a displacement of a triangular shape (picture below). It works fine for the direct transient (linear), however, when performing nonlinear direct transient (with and without LGDISP on) the excitation is not as I intend it to be (second picture). The plots show the displacement in the Y direction in nodes where the displacement is applied in the model. The actual input load data is a triangle as in the first picture. Therefore, I do not understand why when performing nonlinear transient the displacement starts to increase before it is larger than 0 in the input data. There should not be any loading applied before 0.100 s and when changing to nonlinear analysis somehow there is a loading. Also the system does not go back to the zero position. 2) the second problem is that when i use nonlinear direct transient the simulations calculates without any problem but when turning on the LGDISP option I encounter convergence problems: *** ERROR # 4966 *** Minimum time increment reached, analysis aborted. I tried changing the minimum time increment but it does not help. I use TSTEPNL and NLADAPT setup. What options should I change so that the convergence problems does not happen? Thank you very much in advance for any help.
3. ## Solution converges before max iterations are reached

Hello. I am working on the NL buckling of a composite panel (geometric NL implicit) and I successfully setup the model and ran the analysis within radioss after automatic conversion from the optistruct input. The problem is that although I specify I need 50 increments (NINC) with PW convergence criteria, the solution ALWAYS converges at 25 increments and of course the total buckling is not captured. Below is my NLPARM card from the .fem file. I am not specifying anything else in the NLPARM card or in any other cards. Can you please help? NLPARM 6 50 0.0 6 50 PW + 0.01 0.01 20 + 1.0 Thank you
4. ## When should the temperature_flow stagger be used?

We typically suggest to use temperature_flow if the properties are strongly dependent on temperature. Treating flow and temperature as one large matrix can aid convergence in these cases. The degree to which it aids convergence will be extremely problem dependent, so it is difficult to make a blanket statement. If the free convection is dominant, temp-flow would have more effect than if the forced convection is dominant. If the flow equations don't depend on temperature, solving them separately will be faster.
5. ## Topology Convergence problem

Rahul, thanks for the answer. I have increased the no of iterations to 150. Now it converged, but the result is still very bad. The displacement is -1.5e4 in the convergence graph. I dont know whats wrong... Could you please check my model? I attached it in my first post. Thanks for your help, wan
6. ## Optimisation gets close to converging but then diverges

Hi Everyone, I'm running an optimisation with multiple load cases. The solution gets really close to converging (in the .OUT file) the first and second convergence criterion are met and just as its about to converge the solution diverges. It runs for the maximum number of iterations (80) before it stops. Is there any way to change how long the optimisation will for so that a solution is reached before the maximum number of iterations are reached? Or does it more than likely suggest my load cases are incorrect, or theres something wrong with my model? etc.
7. ## Acusolve doesn't stop after reaching convergence

Hello, I am quite new to Acusolve and I need to clear my doubts about convergence and residual ratio. My simulation has maximum time steps set to 300 and convergence tolerance set to 0.001. I am monitoring residuals in AcuProbe (see attachment). Correct me if I am wrong - shouldn't the simulation have already stopped at about 60 Time Step? Does it have other stop criteria? Thanks for any help.
8. ## Integrator Error in Motion Solve

Hello Dear all. I am in need of a quick tip and should be an easy one for the experts in the group. I have attached the image of the mechanism that i am trying to solve. Is a simple inversion of the 4 bar mechanisim- Whit worth Quick Return Mechanism. The DOF are balanced perfectly with combination of the joints . I present the summary of the checker log: Number of (non-ground) Bodies : 7 Number of original Degrees of freedom : 42 Degrees of freedom removed by motions : 1 Degrees of freedom removed by couplers : 0 Degrees of freedom removed by Joints : 41 Degrees of freedom removed by ADV Joints : 0 Total estimated DOF not counting redundant constraints : 0 The Positive Redundant DOF is being removed by the applied velocity of 10 rad/sec. So what is the issue ? 1. I would like to understand the error given by the solver " The Intergrator Failed to proceed after 1.005 Sec " ? Why and how to make it continue. 2. Proper documentation to understand the " Simulation setting "- DSTIFF,VSTIFF, etc....? What are the values ? 2. The tolerance that i need to set for the analysis to continue ? How to decide I am available to have discussion at you best possible time over the forum or I can get in touch with a long call at my mobile. This is an urgent requirement as I have to compare the results with the Hand calcs that our team has done. I hope a reply and assistance at the earliest. Thank you for your time . Please feel to discuss anything regarding Hyperworks ( Except Motion Solve, I am a Noob!). I am an user of altair products for over 5 yrs, is a pleasure to mutually help. Regards Girish +34632975619 QRR.mvw April_13.log
9. ## Change Soft convergence criterion

Hello, when i start an optimization with optistruct the calculation is finished after 1 Iteration. In the Output-file i found following Information: Soft convergence criterion satisfied; the design did not change during the last Iteration. What does this mean? I already did a lot of successful shape-optimizations but in this case i don't really know why the shape didn't change. I changed the default OBJTOL value from the opti control card but the problem still occurs. The most interesting thing is: When i change the inital value in the shape panel to 0.5 I don't have any problems and the optimization finds the best shape. When I start with an inital value of 0.0 then i get the problem with the soft convergence criterion. Thank you Greets, Fatih Uysal
10. ## Results do not Converge

Hello, I'm performing a convergence study on the attached model. The idea is to run multiple simulations for the same model using different mesh sizes, and then determine the appropriate mesh size for this model to guarantee accurate S-parameter results. The simulations were performed using custom meshing for 3.5 mm, 2.5 mm, 1.5 mm, 1.0 mm, 0.5 mm in all of these trials the S-parameter plots were different. Thank you. H_pln1.cfx
11. ## Question on Convergence & Stability

Hi All, I wanted to simulate conjugate heat transfer simulation in AcuSolve which involves Conduction & Mixed convection. I have followed the best practices that are described from meshing to problem setup. Herewith, im attaching my residual plot which seems not converged and stabilized results. It would be helpful if someone help me with this.
12. ## Non-linear Analysis Model will not Converge or Produce results

Hi, I have a model of a breast that should be deformed between two plates. I have tried various variations using the PCONT card, CNTSTB, and EXPERTNL with CNTSTB and I still cannot get the model to produce results. I have tried increasing the NINC card as well to not avail. The top plate will move but it is not interacting with the breast to have it spread across the bottom plate. Any help would be greatly appreciated.
13. ## Convergence

How do I know the convergence of mesh size in my model? Is there a method to know if the mesh has converged?
14. ## Energy convergence

How to interpret the energy results T01 ( Internal , Kinetic & Total Energy) which is observed in Radioss Explicit dynamic analysis ?
15. ## Optistruct Convergence Settings

Hello, I am running a topology optimisation using Optistruct. The results I am getting for a standard min. compliance, constrained volume fraction run without any manufacturing constraints are invalid. The simulation runs but the results do not show any clear structural members but mostly very low density material. However, when I use minimum member size control, extrusion constraints and change the discrete value the results achieved are valid (show structural members). Is there a way to chance the minimum convergence parameters to encourage the solution to find a valid structure for on optimisation without manufacturing constraints. Thank you in advance
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