FAQ - Page 2 of 12

FAQ

• No matter how I’ve tried, I can’t trim the elements with the IGES line data. Is there any alternative to do trimming?
• Modell Check / Initialisation Run
• Metal forming
• LS-DYNA runs into Segmentation Violation (SIGSEGV) error. What can I do?
• Is it possible to allow separation/gap between elements within one part?
• Is it possible to allow separation/gap between elements within one part?
• Is it possible to coarsen a uniformly refined mesh, as well as an adaptively generated mesh?
• Is it possible to do forming simulation by using both implicit and explicit method in the same run?
• Is the order relevant in which I do triming and coarsening of the mesh?
• Is there a way to prevent distortion?
• Is there a way to reduce the penetration problem?
• Is there any limitation for LSDYNA3D to be applied to Metal-Forming analysis?
• Install a New Network License (Microsoft Windows)
• Install a New Network License (Linux/Unix/Solaris)
• In implicit analysis of springback process, there are both linear and non-linear methods. Can you advise which one is better?
• In implicit forming analysis, I found that the friction force was not properly applied, what could have been the problem?
• In LS-DYNA, there are different material models and I’ve found it difficult to choose the proper material model. Would you please give me some suggestions in selecting the proper material model?
• In my analysis of the sheet metal forming process, I frequently found that the calculation could not continue and it terminated unexpectedly. Is there a way to avoid this?
• In my simulation, some of the corner nodes can be put in the wrong place. Can you advise what the problem is?
• In springback analysis I don’t have enough memory or the analysis takes too much time. What can I do ?
• In springback analysis, I found that my constraint hasn’t been taken into account during the simulation, what was the problem?
• In springback analysis, I just changed the constrained nodes a little bit away from the original node. The convergence then became very different and the predicted result seems not to be reasonable. What can be the problem?
• In springback analysis, we had no problem when gravity effect is not considered. However, after gravity effect is included in the input deck, there were some strange error messages. What might be the cause?
• I have very long run times. What can I do?
• I just have one IGES file for the part, and I don’t want to offset the surface for the punch and die physically. Is it possible to offset the two surfaces internally inside LSDYNA3D? If yes, how do you offset these two surfaces?
• I think spring back prediction by using implicit is not realistic. What is your opinion regarding the convergence issue?
• I tried to use LSPOST to compare the strain state with FLD. When I selected the element and clicked the plot button, nothing was plotted. What was the problem?
• If a converged solution from springback prediction cannot be obtained after trying many different combinations of parameters, what else can I do?
• If I didn’t find wrinkling and strain localization in from my simulation, can I say that my design is good?
• If I use very coarse mesh for the pre-deformation (such as pre-bending, gravity loading etc), and then refine the mesh in the later forming analysis. Will it result in obvious numerical error for the final results?
• If localized necking occurs what can I do to get rid of it?
• If wrinkling occurs, what can I do to get rid of it?
• I’ve found that when I use several CPUs with the SMP code that only one CPU is working and the other CPUs are idle. What is the problem and how can it be corrected?
• How do you trim the blank after a forming analysis?
• How do you trim the blank after a forming analysis?
• How do you use RIGID_BODY_STOPPER?
• How is the FLD obtained in LSPOST? What is the limitation of using this FLD?
• How many levels of adaptive mesh do I need in my calculation?
• How to do hydro forming analysis?
• How to use non-smooth trimming?
• I found that the number of adapted elements was too large when I performed a multi-stage forming analysis using adaptivity. Is there a way to avoid this problem?
• I generated a dynain file after forming analysis. Additionally, I used DYNAFORM to trim the mesh, and did springback prediction. However, I found that the predicted springback is too small to be true. What is the problem?
• I had no problem in running a forming job, however, when I used adaptive method, the contact does work properly even from the beginning without adaptivity. What is the problem?
• I have no experience in springback prediction, and have no idea whether my prediction is reasonable. Do you have any idea how accurate the solution could be from LSDYNA?
• How can nodal accelerations be evaluated in LS-DYNA?
• How can I handle contact between beams and shells?
• How can I evaluate material formability for a new material?
• How can I specify friction coefficient in the contact interface?
• How can you add constraints for a springback analysis?
• How can you evaluate the material formability under complexity deformation condition or multiple steps forming?
• How do I choose the element type for the analysis of sheet metal stamping?
• How do I implement my own FLD in LSPOST?
• How do I specify the draw bead force?
• How do I use define draw bead in stamping analysis?
• How do you perform a multiple step analysis?
• General
• FAQ
• During the forming analysis I found that some elements in the blank became distorted. How can this problem be solved?
• Even if I include the card of *CONTROL_ADAPTIVE in my input deck, the blank is not adapted. How can I fix this problem?
• Do you have tips how to combat instabilities?
• Do I have an easier way to define the velocity curve?
• Do I have to consider the thickness of the blank?
• Do I have to consider the thickness of the rigid bodies?
• Contact
• Can I arbitrarily pick the nodes to constrain for a springback analysis?
• Can you advise how to improve the speed in the forming analysis? The user may choose either mass scaling or velocity scaling. It is very common to use a combination of the two methods. Extreme care should be taken when using both.
• Can you explain the failure behaviors that occur in sheet metal forming?
• After the trimming process, some of the elements in the blank mesh have become distorted around the trim line. How can this be avoided?
• There are several linear solvers for implicit analysis. Can you tell me which one is the fastest and most accurate?
• There are several non-linear solvers for implicit analysis – which one is better?
• There is no load applied to the blank when I used *LOAD_MASK. What might be the problem?
• Upgrade a Network License (Microsoft Windows)
• Upgrade a Network License (Linux/Unix/Solaris)
• Use the card of *CONSTRAINED_RIGID_BODY_STOPPERSYou can constrain the displacement by specifying a negative value for LCMAX and LCMIN.How is seamless springback analysis done with LSDYNA?
• What are the differences between implicit and explicit?
• What are the differences between smooth and non-smooth trimming?
• What can I do if the direction of the pressure is not reasonable after the mesh had been refined adaptively?
• What can I do if the mesh for the last state was not written to the d3plot after restarting from d3dumpxx?
• What is FLD?
• What is mass scaling?
• What is the difference between a discrete beam and a spring ?
• What is the difference between *CONTACT_AUTOMATIC_ SINGLE_SURFACE and *CONTACT_AUTOMATIC_GENERAL ?
• What is the IGNORE flag good for?
• What is the commonly used contact type in stamping analysis?
• What is the effect of R value (material anisotropic parameter) on FLD?
• What is the effect of R-value on material formability?
• What is the material formability?
• What is the proper punch speed that could be used in stamping simulation?
• What is the proper strategy to switch from implicit and explicit method or from explicit to implicit method?
• What is the use of defining a box for drawbead?
• What is the use of RIGID-BODY_STOPPER?
• What kind of velocity pattern is better for metal forming analysis?
• When I a used drawbead in the forming analysis, it was observed that some of the elements which moved over the bead line were distorted, and there is no obvious reason for this effect. What might be the problem?
• When I attempt to do a springback analysis, I sometimes have difficulty in obtaining a converged solution. What options are available to improve convergence of springback?
• When I did dynamic relaxation analysis in gravity loading process, it took a long time to get a converged solution. Is there a way to make this analysis faster?
• When I did forming simulation, I found that a material failure was predicted earlier then expected, what might be the problem?
• When I do springback analysis, the prediction is not satisfactory. I didn’t find any problem in the input deck. What should I check to improve the solution quality?
• When I run forming simulation, I had such message as “Error: slaves nodes may cross the surface, please check your model, job continues.” I’ve checked my input deck and didn’t find any obvious mistake for the mesh. How can I fix this problem?
• When I tried to trim the mesh after forming, the generated ‘dynain’ file contains the mesh without trimming, what is the problem and how can I fix it?
• When I trim the blank using IGES file, there is a message such as “Entity type xxx form 0 not supported # lines = x”. What does it mean?
• When I trimmed the mesh after forming, I only used one trim curve (in IGES format), but LSDYNA found 10 trimming curves. Accordingly, the result was not acceptable. What was the problem?
• When I use constrain method (SOFT=4 in the FORMING_ONE_WAY_xx card), the calculation terminates immediately, what is the problem?
• When I use FEA, I don’t know how big the mesh size should be. Would you please tell me what is the proper mesh size?
• When I use mesh adaptivity in my stamping simulation I don’t know how to define the proper adaptive frequency. Would you please give me some suggestions?
• When I use the implicit method to do springback analysis I cannot obtain a converged solution no matter what I’ve done. Do I have some other choices to obtain a converged solution for springback prediction?
• When I used coarsening, I found that there is an error message:’ Something is wrong, sub: nextele’. What is the problem, and how can I avoid it?
• When I used implicit method to do springback analysis, the iteration information was not output or displayed in the screen. I think this iteration information is important for me to monitor the convergence status. How can I display this information?
• When I used switch method in my calculation, I used explicit method and then I changed to implicit method. In the later implicit calculation process, it was seen that the contact didn’t work properly. What was the problem, and how can I avoid this?
• When I used the seamless method to do both forming and springback analysis, a converged solution wasn’t obtained. I don’t want to repeat the forming analysis. Is there a way I can repeat the springback analysis from the previous output files?
• When the constraint contact is used, the calculation crashes during the forming analysis. What needs to be done to prevent this?
• When we do springback analysis, we have two choices to do it, i.e. using implicit and explicit method (dynamic relaxation). What is the advantage of using the implicit method in springback analysis?
• Why does the restart of the springback analysis not work?
• Why dynamic relaxation doesn’t seem to work at times?
• Will the mesh coarsening affect the accuracy of springback prediction?