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dear @negativevolume I created a new topic at:

@negativevolume @mohammad_basri Hi! Tell me pls, was the problem solved? Suppose I have something like it.

@djsburra hi. Here is a new active link. It has been quite a while since I've used/updated this. I'm not 100% sure that it will work without any tweaking to the strings for the filenames/file paths. Hopefully it can at least serve as a guide.

@harsha Ah I see, very cool. I'd be interested to read about this study if you choose to publish! But yes, the world of LS-Dyna video tutorials is very slim as it is for traditional forms of analysis so I'm not sure much is out there. Those links may be useful for you along the way though. The link below is where I would normally point people to examples to work through but I do not see any on this modeling technique. Are you experienced in "traditional" forms of LS-Dyna simulation? Knowing your experience level will help me help you. Are you a graduate student? It looks like LSTC offers a class for this $175 for students. Maybe your PI could cover that if it is vital toward your research. Then you could come here and educate all of us!

Hi @jhaley, When dealing with impactors like rigid walls, you need to think about what you are trying to model. It's easy to model something hitting a rigid wall because all you have to do is constrain the wall in space. Any resulting forces will be a result from the object hitting the wall. However, when you are applying a velocity to a rigid wall, you need to make sure that the wall is representing what you want it to represent. If it's a vehicle with a mass of 1300 kg then you need to to define inertial properties to represent that. Example: You have two cases, a 10 mm thick wall and a fully modeled vehicle. Both are modeled with a rigid material but the wall has a much higher density so that both weigh 1300 kg. The wall is going to behave differently during an initial velocity impact than the fully modeled rigid vehicle. Something that you can do is measure the inertial properties of the rigid vehicle and then apply these to the wall so that it behaves "similarly" to the vehicle. You can measure this by going into the Element side tab -> Measure -> Inertia -> Active elements only (only have the object to measure active) -> All. You can apply inertial properties to a part by changing from a standard *Part to *Part_Inertia. Long story short: Apply an initial velocity to the parts of the simulation that you are analyzing and not the rigid wall if you aren't restricted by a certain testing setup. But if you have too, make sure you have the correct inertial properties for the rigid wall. Regarding the issue with your elements during the contact: A rigid wall impacting very soft materials is going to be prone to instability, especially at high severity impacts. You can adjust your contacts to counteract this with some additional parameters like Soft=2 coupled with Depth=5 or Soft=1 which is meant for a contact between hard and soft surfaces. I've attached a picture of how to access these other options and a link to more info. You should also mess around with different types of entities used for the contact (segment sets vs parts) especially if you have solid parts which may perform better with segment sets in a contact. You can also vary the master and slave stiffness values (SFS, SFM) as well as the viscous damping coefficient (VDC) which can help with values around 20 to 40 usually. You should also add your soft parts to *Contact_Interior which is necessary for minimizing instability of soft components. Just make a *Set_Part of all of the parts that are soft (yes it can be just 1 part) and then reference this part set in the *Contact_Interior card. You can only have 1 *Contact Interior so don't try to make more than 1 of them, but you can add as many parts as you want to the part set referenced by it. (Just FYI) And finally your hourglass formulation of the soft part can play a large role in the stability of that part. Here's a helpful resource that explains it all better than I can in a few paragraphs. Feel free to ask any specific questions, I hope this helped! < span style="color: #666;"> Attachment : soft_contact.PNG

also here is a good discussion on the same topic. you can use model checking tool in ls prepost to check if there is any error.

Hi, usually its a problem with contact or material model used. I have found some info online. This may help.

@negativevolume Thanks for the link. The thing of the offset does not work well in this case, have a look here:

Hi @zanoofar, I'll link to an LS-Dyna ticket request below. It's basically just an official answer from LSTC. This may or may not be helpful, so let me know!

@themountain Yeah what you can do if you want to combine the overlapping ends is to basically create a bridge between the two ends and delete the parts inside that are overlapping. This may help show you how to do ruled meshing.

@erick With the exception of the force transducer, I believe this was all covered here: The force transducer is used to isolate the contact force between a specific region of a contact. So if you have a simple simulation then you probably don't need to worry about using it. To implement it, you would just use the same detailed as the current contact in the model but isolate whatever entities you want force from. If you have a part to part contact then make the force transducer part to part. If it is a segment set to seg set contact then make the force transducer segment set. Here is a good example of what I am talking about with the force transducer.

@adityasreekumar So what are you trying to study with the simulation? The boat or the water or both? So is this a study of fluid dynamics, mechanics, or fluid-structure interaction (FSI)? Given your problem, I think you may be better off running a CFD simulation which is commonly used for hydrodynamics. Here are some examples to start if you choose to pursue this: You can also do FSI using the same method, though it's more complicated: You did mention wanting to simulation both water and air though. Are you restricted to using SPH?

Hi @ghillo, thanks for the great question! This is a fairly complex question and may require some time to solve fully. So you want to get strain response in the local coordinate system of the elements. One thing that will be critical is the *Material of the part in particular. Just the *MAT title will be enough. Only certain materials have the ability to do what you are looking for. Could you also tell me if the elements of this part are defined as *Element_solid or *Element_solid_ortho? The latter option allows you to sort of hard-code in a local coordinate system to each element. So first, make sure you have *Database_extent_binary and CMPFLG=1. This flags the orthotropic materials to output in their local coordinate system: Next, you will want to define AOPT in the *Material card which is the material axes. This will define a local axis for each element defined with that material. There are multiple methods to do this, some resources I have listed below: This can get very complicated so let me know where you have questions. I can continue to help look into this for you.

Hi @tttthhhxx, Have you checked the existing topics here related to addressing that same issue? Looks like the usual suspects to cause this are: not running Dyna with double precision running on a Windows machine SMP vs MPP Possible contacts Here are some previous topics: