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Good Afternoon,I am currently working in LS-PrePost and I am trying to create a pulsatile, sinusoidal inlet velocity for a 2D geometry simulation. The inlet velocity expression is 0.0266*0.00786*sin(2*3.14*0.3*TIME). For the inlet velocity, I have inserted via the keyword *DEFINE_CURVE_FUNCTION as shown in the image, however I am receiving an error.What are the steps to correcly apply this pulsatile sinusoidal function to the inlet?

Hello. I am simulating the bending process of a thin plate.I would like to measure stain and stress in a coordinate system along the material axis.Furthermore, my goal is to visualize them with "Fringe Component" and to output the values to a file.Please give me your ideas.Thanks.Chihiro Komatsu

Hi, I am modeling a 3D object that is part of a hollow sphere which radius is 7.8 mm and its thickness is 0.536mm. From the side view, it makes a circular arc equal to 120 degrees. It is made of a linear elastic material with E = 0.3 Mpa. At the top vertex, a chain of steel spheres sits on this object, and their displacement is limited to the Y axis. The bottom corner face of the object is fixed and a constant pressure of 2400pa is applied on the interior surface of the object.At first, I did a Static Structural analysis to find deformations related to gravity and the constant pressure, and then I wanted to do an explicit analysis for an impact through the chain using Ls Dyna for about 1 millisecond. Even though everything is the same for the Ls Dyna analysis, the curved object starts oscillating. I have used dynamic relaxation for Standard Earth Gravity and also option "Both" for Dynamic Relaxation Behavior of applying the pressure. So the oscillation amplitude is not too large according to the scale of the whole model. However, It is enlarging over time, and even this small oscillation will significantly affect my final results since I need high accuracy. Two attachments show the oscillation. The image below contains a graph showing deformation of the top vertex of the curved object. Why at the beginning of the Ls Dyna analysis, its deformation suddenly reduces from 0.0573mm (which is the result of the Static Structural analysis) to 0.055024mm and then gradually goes up again?To solve the oscillation issue, is it a good idea to use an Ls Dyna Restart analysis for the impact after the Ls Dyna analysis and reduce the first Ls Dyna analysis end time from 1 ms to 0.2 ms to have the minimum oscillation amplitude before the impact (This approach significantly increases the ansys file size and I don't know why!?)? If not, what should I do to completely dampen this oscillation?Also, I should mention that since I need to measure Nodal Contact Force through this analysis, my only option is to do a 3D analysis in Ls Dyna.

Is it possible for LS-DYNA version R14 itself to have some bugs? I run old files in newer version as I doubted this. For example, when MAT Erosion is used with Titles, and run in LS solver all the input values shift down one row and the material failure didn't occur. (I have to make the simulation without title)Another example is that SOLID SPG with IDAM 1 and FS 0.002 works in R11, but the same keyword file fails to show failure in R14.One more example is In tension failure analysis, element deletion didn't happen as it is supposed to. In the figure, the element at the tip has to be deleted first. (It works fine with older version.)

Can you please let me know if there is a way to export unit vectors along the eigen directions or scaled vectors representing the total principal stresses?  I also would like to know if there is a way to output eigen vectors of plastic strain rate.  We are using Mat-18, Johnson-Cook. The real goal is to create streamlines of these eigen vectors. We used to obtain them from ABAQUS/CAE and had to then sort neighboring vectors to make this meaningful.  However, looking at the vectors in LS-PREPOST they seem to already be sorted, at least in the region of most interest to use.  Is there a way in LS-PREPOST to directly create streamlines of these vector fields?  I ask because I am not familiar with the fluids post-processing and believe this should be easily doable. Or should we look into LS-Taurus (is it even available, or work?) or some other software? Thanks,Vis 

How can I define Failure such as Volumetric strain in SPH models. I am using LS duna

Hi everyone,I'm currently working on implementing an user defined EOS (Equation of State) using a lookup table similar to SESAME EOS in Autodyn. I've managed to modify the user-defined EOS in the mdeos_user_1.f90 file, but I'm unsure about how to include a table in the EOS. If anyone has any advice or suggestions, I would greatly appreciate your assistance.Thanks in advance!

Hi all, I am trying to model an iced, rectangular, metallic plate being hit from underneath with a cylindrical impactor. The plate is clamped on its short ends and modeled using *MAT_ELASTIC. To simulate cohesive fracture within the ice, I use peridynamics: the nodes of the block of ice are disconnected and the elements use *SECTION_SOLID_PERI and *MAT_ELASTIC_PERI. The block of ice is attached to the plate via a tiebreak contact. While the parameters in *MAT_ELASTIC_PERI are quite straightforward and the relationships to micro-modulus and critical stretch are well-defined, it is not the case with *SECTION_SOLID_PERI and the "Dr" parameter. The issue I am facing is that I am not sure which value to use for Dr, since changing it affects the results significantly. Moreover, I do not understand why, under the hood, LS-DYNA performs a check on the surrounding neighbors of every point to make sure there are at least 12 and at most 136, and then tunes the horizon size accordingly. Does that mean that the used horizon size is not the same as the one calculated using "Dr"?For reference, I am attaching a picture of the model (green part is ice, the other part is the plate, the impactor hits the plate on its center from the back), and two snapshots of two identical simulations at the same time after the impact, the only difference being the "Dr" parameter used. The first one has Dr=1, and the second one, Dr=2. The snapshots represent a top view of only the ice, where the effective plastic strain (ie peridynamics damage) is fringed. As shown, there is some difference to the crack patterns that emerge from the impact just by changing this parameter.I would appreciate any advice regarding how to pick this value or at least minimise its effect on the final results, as well as any improvements that could work in this case. Many thanks in advance!

Hello,I like Prepost but its repeated crashing when building a model is annoying (it becomes unresponsive which requires killing it to be more accurate).It mostly occurs when changing the nodes or elements (deleting, generating though elgen or remesh, replacing nodes, splitting, etc.) but never when changing coordinates (e.g. transforming). This happens with different models that open without warning in prepost (mostly R11 and R9).This has been happening for many years (I have been using prepost regularly but not full time for over 15 years).After the crash, repeating the same operation on a freshly opened file usually works. If not, doing the same operation in a different version works.So I typically save quite often a proj file as backup (quick to update) and restart from there after the crash.But today, my proj file got corrupted somehow as I was working in 4.12 2025/R1. I cannot open it anymore in any version and I just lost two hours of tedious work. This is a new one.I have automatic proj save (every 8 minutes) but I guess it does not keep the versions after the file is saved (why by the way?). Bummer.So, my questions are the following:any possibility to extract contents of a corrupted proj file ?any possibility to keep intermediate .proj files? (the software should check that the file is not corrupted before deleting by the way)any possibility to generate crash dumps that could then be used by developpers for debug (difficult to post a bug for something that does not happen on a freshly opened file)when it becomes unresponsive (e.g. on element delete), what happens internally? If updating the nodes/elements database, any function to check its consistency (to prevent crashing) ? How long to wait to see if it can recover (lets say for a model <50k elements on a modern PC)?any other suggestion on settings/practices? I alternate between Prepost 4.7, 4.8, 4.10, 4.11, 4.12 (each has its own lsppconf) including double precision versions on 4.11/4.12 (seems useful with models with large ids), on two windows 10 machines with 32GB memory or more (one with integrated graphics, one with a Nvidia GPU: no difference by the way)  and the current crashes are on a small model (<30k elements, <50 parts/mat/sections, a few contacts, spotwelds and CNRB options).ThanksPhilippe

Hello Forum,I am running a full SALE calculation, but would like to be able to just somehow get an ASCII output of the pressure history of the contacting element without needing to store large D3PLOTS and probe the element pressure. Is there an easier way to do this for ALE elements? I'm trying to use DATABASE_FSI_SENSOR, but I'm not sure how to set that up correctly... Thanks,Peter

Hello,I'm currently facing some difficulties in setting up the Analysis Settings for Explicit Dynamics. In particular, I'm having trouble with the Erosion Controls section, where the default value for Geometric Strain Limit is set to 1.5.However, while browsing through a post on the Ansys Learning Forum, I came across a suggestion stating that this value should be set as the ratio of the material's ultimate tensile strength to the Young's modulus.Upon trying this approach and running simulations with the adjusted value, I observed that the material seems to fail much more readily compared to my usual results.Could someone clarify why the recommended approach suggests using the ratio of ultimate tensile strength to Young's modulus for setting the Geometric Strain Limit value?Furthermore, I intend to apply this to collision analysis with a focus on the target's failure. With two materials involved, the colliding object and the target, which material's calculated Geometric Strain Limit value should be utilized?Thank you in advance for any insights or explanations provided.

Hi,I am a student at the university of tokyo, and our lab have purchased a licence of dyna. We want to realize some speical boundary condition using the user defined solver.Specifically, we want to change the ratio of MPC(Multiple Point Constraint), for example, ux,1 - ratio * ux,2 = 0. Is it possible to modify the codes of compiled solver to realize this?For example, doing some implementation in dyn21.F, subroutine loadsetud, etc..Would you please give us some hints?Best,Chen

Hi All,I am trying to study the temperature (25C to 1000C) and velocity effect (200m/s to 5000m/s) on the impact of 2 solid objects (Steel and Aluminum). I am using the Johnson-Cook model for the materials. Still, I do not see any effect of Velocity and temperature.Kindly let me know the source where I can learn and correct my mistakes. Thank you in advance

Hi all.What is the difference between Element_Solid and Elmenet_Solid(ten nodes format)? I am making a model of glass breaking. What's more suitable?

I want to start learn LS-Dyna for use it in my science research. Could you please give me some advice how to start. I will investigate influance from impulse load on different type of structure. Also I want to use LS-Dyna in Ansys Workbench. I tried simulate blast load on plate used Snippet how discribe here https://forum.ansys.com/forums/topic/shock-wave-ansys-ls-dyna/ and Keyword Manager but all method failer. Program just stopped at 10% and nothing happened. Thanks for your answers

HelloI am trying to model the cuboid-shaped TNT charges in AUTODYN, I want to initially use a fine mesh and then remap and use a coarser mesh. I have noticed that one needs to change the solver type for 3D remap to Euler-FCT. I can't seem to change a solver for a part from Euler-Godunov to Euler-FCT I am getting an error (picture attached), is there a way to change this solver type Euler-FCT or a way to perform simulations of cuboid-shaped charges in AUTODYN.

Hi all.I'm simulating drilling. The first time I made a model as in the test version of LSTC:  Everything worked.Now I made another model, in the form of a drill tip for concrete. And when I set rotation to the upper segment of the drill, the mesh is distorted. Why? I use exactly the same settings when I used a model like the LSTC. In the LSTC model, the drill did not touch the SPG (not lagrange mesh) die, but in the new model I made contact, could this be a problem? But if I turn off rotation and leave only translation, the drill doesn't distort:  But if I turn off rotation and leave only translation, the drill doesn't distort:  In addition, the drill compresses strongly when touched, although it is steel and the LNG die is made of concrete. Previously, this did not happen with the same settings: HELP PLEASE

Hello!I am simulating a drone hitting a pitch link of a helicopter with a velocity of 30 m/s in the middle of the link.Im having a few problems with verifying my results with handwritten calculation. I am considering the pitch link (a solid rod) a beam so that I may use beam theory. The link is fixed in both ends which would make the equation for maximum deformation in the middle:(F*L^3)/(192*E*I)The drone is made out of Expanded polypropylene foam which has spring properties and should reduce the impact force F acting upon the link.Right now I am using the formula for impact force F = (m*deltaV) / impact time but i also wanna know how i should subtract the spring force upon the drone.I am using 0,001 s as impact time and deltaV= 30 m/s.  

Dear all, I have an important question about this topic. I want to apply the earthquake in z direction to the tank fill of water with the box floating on it like top figure. I add one more picture to show it better here. I need to first gravity initialize the box and after it reached equilibrium, I am going to apply earthquake just in Z direction. It is basically two step. Step one, from 0 to 5 second, I just apply graviry through a inclined curve and then apply earquake at 5 second ( the acceleration that I provided starts after 5 second). My problem is that I need the base of the tank to be fixed in z direction in order to gravity initiation, but for the next step that I want to apply acceleration in z direction, I need that DOF in z direction to be free. If I fix DOF in z direction, my tank doesn't more in z direction when earthquake applies but the first step (gravity initialization) reaches equilibrium and the problem with having the DOF in z direction free, it doesn't converge in the gravity initialization and box starts to rotate. Do you have any solution for me? I did the same thing for Y direction and the results were successful because for applying earthquake in y direction, I don't need to free the DOF in z direction free and I could get reasonable response. Appreciate any suggestions.

Hello,I'm experiencing an issue with the two-phase EOS for water in ANSYS Autodyn, receiving an "invalid initial pressure for two-phase EOS" error. I've checked the initial settings and parameters but can't seem to resolve it. Has anyone faced this before and can offer some advice?Thanks in advance for any help!Best,ZQY

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Hello all,I'm currently testing to figure out how I can analyze the maximum principal strain of 2 solid sets at a time using elout in the Binout option in Ls PrePost. Previously I have always analyzed 1 solid set at a time. For context, I am analyzing 2 separate chambers of the human heart in the TOYOTA THUMS model. I tried setting up a second solid set, but when I open the Binout --> elout --> strain --> solid , I don't see the solid sets separated to pick from, and I just see a big group of elements in the elout branch. Is there any way around this? What have I done wrong to not see the 2 solid sets separately? Thank you in advance, Grant.

Hello! I need help to get some steps to solve a problem during a restart. I'm trying to replicate the example of an earthquake analysis of a dam provided here: https://lsdyna.ansys.com/dams/I organized the example files in separate directories and followed these steps (as described in the example README file):1. Run dam-static.k 2. Run dam-auxiliary.k 3. Copy stat.d3dump01 from the static run (stat.d3full01 for MPP), and aux.gmbin from the dynamic run, into a separate directory for transient analysis. 4. Run dam-transient.kI'm running on a small Linux machine, with ANSYS 2023 R2, and these are the commands I used:cd 01staticlsdyna -dis -np 8 i=dam-static.k jobid=statcd ..cp 00motion/* 02aux/. ## 00motion contains the ground motion filescp 00motion/* 03trans/.cd 02aux/lsdyna -dis -np 8 i=dam-auxiliary.k jobid=auxcd ../03transcp ../01static/stat.d3dump* .cp ../02aux/aux.gmbin .lsdyna -dis -np 8 i=dam-transient.k r=stat.d3dump01 gminp=aux.gmbin jobid=trnThe error I get is as follows: *** Error 10871 (KEY+871) For small deck restart, need to add *CHANGE_CURVE_DEFINITION for curve id 1 in the restart input file E r r o r t e r m i n a t i o nI could not figure out or find information on how to modify the files to include the *CHANGE_CURVE_DEFINITION keyword and what syntax to use. Any steps to help solve the issue are welcome. Thanks. --Roque LopezRescale team. 

Dear everyone,I have been reading some papers that used results of minimum principal stress of concrete to identify compression and tensile regions of the concrete structure. What is the meaning of minimum principal stress result in LS-Prepost and could other stress results be used for this purpose?Best regards,Panha

Dear everyone,I have been working on finding damage results for RC structures. However, I saw all research papers using "effective plastic strain" results in LS-Prepost to represent crack patterns/damage of concrete. What is the meaning of "effective plastic strain" and why is it used to represent crack or damage patterns?Best Regards,Panha