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Hey, I'm a 3D model artist, and I'm here because the youtube channel has genuinely motivated me to learn about its physical simulations and etcetera... yeah, you are wondering how a person related to the artist sector of the videogames industry will take part in this, well, I studied systems engineering and have this background about integral and mathematic models to achieve certain results and I discover that LSDyna does this. The thing is that I have this model made on Blender with a lot of polygons because I needed to make tweaks with the sculpting mode, but then I want to use this as a beginning point for Ls-prepost to make a simulation for publicity (adds), I watched that LS-Dyna pre-post can do this and then convert this to an object in Blender so that I can put materials and other stuff, stuff that doesn't have LS-pre post for obvious reasons. I've made a research on drill bits and I've found this , Talks about the drillbit density, youngs module, Poisson distribution, and a lot of stuff that sincerely is quite difficult to process without guidance...Though I watched that this data can be useful to input on the materials keyword manager. Questions> 1. My models made in blender would work as a starting point or do I have it to make them again in hypermesh? 2. Can someone guide me with key points to achieve this process? 3. Do I have to study for one year to achieve this? 4. The simulation will have a rigid material and the other one would be the wall of concrete or is more complex than that? Sorry for the biblical post, I only want some guidance, where do I find information about drillbits or videos that simulate this or books or the steps that I have to make to achieve what I want. The drillbit that I want to simulate is called SDS S4 Cross Point Drillbit Thanks in advance, < span style="color: #666;"> Attachment :  LSPrepostDrillbit.PNG

Dear everyone: I am trying to preload an RC specimen with gravity. In order to achieve that, I employed the mass weight method to apply gravity. The model and corresponding artificial damping curve are shown in Fig.1 and Fig.2. After the structures achieve static equilibrium in the first analysis (Fig 3), I proceed into the full restart analysis stage. The dump01 file of the first analysis is copied into a new fold for restart analysis, as well as the original keyword file with only modification on CONTROL_TERMINATION and STRESS_INITIALIZATION (To check if the gravity is applied properly). However, here the problem comes. After the restart analysis finished, the contact force showed a kind of high-frequency-oscillation, as shown in Fig 4. I also checked axial force in the cross-section of the middle beam, similar problems also exist. Relevant introducing documents about preload or restart only provide brief roadmaps to these techniques, while solutions for this kind of detail problems are still lacking as much as I can recall. So, I hope anyone who used to encounter similar problems could provide solutions for this problem. This is precious for me and any future researchers concerning preload and restart problems. Thanks for your attention.

That error is quite the pain. Try some of the solutions discussed here in the past:

Hi @murali, Sorry for the delay. The links below should give you plenty of detail regarding your question. Let me know if you have any further questions!

@groll And you want the fluid elements to erode when they impact the wall? Why don't you try an SPH simulation? That seems more reasonable for what you are looking to accomplish. Below is an example that seems an a lot like what you are trying to simulation which you can use as a guide for your sim. There's also this example comparing lagrangian and sph

Hello all, I am doing direct optimization with GA algorithm.This is how i had defined the Termination criteria.Note i am using composites with curve matching (MeanSqErr) as my objective. As per my Termination criteria, it should stop when 3 same optimums are generated right ? (0.1*30= 3).but from the picture you can see that it stops after 5 same values. I wanted to know how it terminates.Thanks in advance.

Hey guys, I have some questions regarding meshing overlapped geometries. I have this geometry with two pieces: the yellow piece and the blue piece, both made of 2D surface mesh. They overlap a bit as shown in the picture. My goal is to create continuous solid meshes out of these two pieces. My current approach is: (1) create two solid bodies out of the surface mesh separately, then (2) Boolean Operation merge the two solid bodies into one solid body, then (3) Volume Tetra them. The problem of this approach is that the two merged bodies generate narrow irregular geometry lines at the overlapped part, which leads to really fine mesh at the overlapped region, as shown below, I need evenly sized meshes (length ~0.04) for the model to stay stable. I’ve tried to use Check Elements to save the elements smaller than 0.01, then remesh them using Tetra Remesh, but it did not work. Any suggestions on how to generate solid mesh better in this situation? I’ve attached the model file in this post. Thank you!

Hi @harsha, Unfortunately I am not familiar with these NURBs elements, but I am curious as to why you are trying this method? I just checked in the LS-Dyna manual and found the page for *Element_shell_nurbs_patch. Is that what you are asking about? Here are a few links that may be useful. I may not be able to help much but I can try to answer any specific questions that you may have.

@pranav I'm not familiar with doing pushover analysis in LS-Dyna, but I did find these two papers/guides that should be helpful: I'd be happy to help with modeling questions along the way though!

@ Negative Volume, @geardyn.1 Hey, Thanks for the reply, i shall consider your suggestions and try my simulation's.

Some old threads on the topic

Are you using dynamic relaxation? This thread from a few years ago mentions it could be causing the simulation to run beyond 100%, causing your problem? If no that, maybe it has to do with coupling parameters in *Constrained_Beam_in_Solid? Maybe your beam lengths are too small vs the amount of coupling points you are trying to set? Here's a paper from LS-Dyna describing the development of *Constrained_Beam_in_Solid if you haven't seen, might be of use.

First off, different types of elements require different element formulations (ELFORM): hexahedral elements (ELFORM=-2 to 3), tetrahedral elements (ELFORM=4, 10, 13, 16, 17), and pentahedral elements (ELFORM=15, 115). Ideally, you'd like all of your 3D elements to be hexahedral as the are the most stable and accurate, but a lot of times you can have really complex geometries where tetrahedrals are required. Example: meshing a table top will be relatively easy to do with hexahedral elements, but meshing an organic shape like a human heart will be much more difficult to do with hexas so you will need to use tetrahedral elements. The main drawback to using tetrahedral elements is volumetric locking which yields a much stiffer response. You can read more into this here: With regards to element formulations, it's generally best practice to use ELFORM=1 for hexahedral elements, ELFORM=13 for tetrahedral elements, and ELFORM=15 for pentahedral elements (although these are mainly used for transition elements between hexas and tetras). A *Hourglass card (HG) will be necessary for an ELFORM=1 hexahedral element which can drastically change the response characteristics of that material. This can be frustrating if you spend time validating a material model, only to have the response completely dependent on hourglass formulations. Generally, use HG=1,2,3 or HG=6 for soft materials under high rates, HG=4,5 for more structural components or if you are having stability issues with HG=1,2,3. The qm value for the hourglass will matter as well and usually this is between 0.1 and 0.5. Further details on what hourglasses to use can be found below: ELFORM 2, -2, and -1 are all selectively reduced fully integrated hexahedral elements and are much more computationally expensive (and stiff most of the time) than ELFORM 1. -2 and -1 were recent improvements to 2 and have shown some promise. If you are having issues with finding a suitable combination of ELFORM 1 and Hourglass, then you can try any of these and see if it responds any better. For tetrahedral elements, ELFORM 13 alleviates some of the volumetric locking concerns and has faster runtime than ELFORM 10. A really helpful look into all of this can be found below. Let me know if you have any specific questions regarding any of this!

First off, make sure your unit system is consistent. This is a bit of a hard concept to grasp as there are not settings to just define the unit system. You need to pick a unit system and then apply your boundary conditions using that system. Here's an example of a bunch of unit systems which are defined along the rows: It's really important to check this because you can really mess up your results and they won't make sense. Regarding your first question though, yes, you should always use a time-displacement curve when simulating a controlled compression so that you can give a final compression value and then calculate how much time is required to get the desired deformation rate. Your curves look correct and yes your termination time is 280000ms. Your d3plot frequency is only the frame-rate of the animation so you don't need too many. Maybe say that you want 100 frames: 280000ms/100=2800ms which would be your d3plot frequency. LS-Dyna has two forms of analysis: explicit and implicit. Explicit is the standard form and is meant for crash analysis and simulation under 1-2 seconds (1000-2000ms), where as implicit is meant for much longer simulations like your case. That's what the problem in the picture is meaning when it says Implicit is required for this problem. There are some specific control cards that you will need to run implicit, which will depend on the simulation. Is there a contact that you defined between the plate and the tube? Or are you prescribing motion to the top of the tube? Contacts within implicit are much more unstable so there are some precautions to take if you have any. I would start with this link below and you can ask questions as you go. General rule is to start with the minimum required cards and get more complicated if it isn't working for you. Good luck!

Honestly, I’m not sure a resource like that for best practices is available. There could be a Dyna PowerPoint highlights potential use cases for the different connection types though. It would be great to compile something like this though as most of the time it’s just acquired knowledge. Here’s two resources to give the basic overview for beams vs discrete beams. Not so much applications though.