Thank you Ameen Topa, this tutorial will be useful for engineers, can you make the same video for a composite sandwich structure which includes face sheet(carbon fiber, fiberglass) and honeycomb(Nomex, aluminum) ? Kind regards
Please share my tutorials if you find them useful. With more shares and views, I will be more motivated to do more and more videos! :D I got lots of requests in my list. I will add yours to the list. Sure one day it will come.
Good afternoon, Ameen. Thank you very much for the tutorial video, thanks to them I have become much better at modeling. I have two questions for you: 1) Could you make a video in which you showed how to use the basic tools of LS-DYNA (for example, editing geometry, building a grid on a 3D model, measuring distances between points, planes, and more). 2) Please advise which material model can be used to model a polymer material (sealant, mastic), for example, such as is used for vibration isolation of the car body or for sealing the seams of the cooling system of the car. I am very grateful and grateful to you in advance. You're doing a wonderful job!!
Good evening. You are welcome. 1) For the basic tools, unfortunately, I don't have a specific tutorial for that. However, I have covered most of the editing tools in my tutorial playlist: LSDYNA BASIC TUTORIALS. 2) This is a hyper elastic material. You can use material models such as MAT MOONEY RIVILIN. Unfortunately, I don't make any requests anymore due to my limited time. However, I do take paid consultation and training jobs, if you are willing to pay.
@@vladimirlubimov2318 It depends on the complexity of the project. Please email us the details of the project. You can find our contacts in the site below: sites.google.com/view/topacademyofficial/about-topacademy
Thank you vey much. I am enjoying so much your videos. I am in situation that I have to apply load on the specific area using rigid body impactor. My plate is refined mesh and the impactor is course mesh. I choose the impactor because I can simply change the mesh of my plate and I don't have to select the node set where i apply the load manually. So, I have tried to apply force on the plate using rectangular box so that I can have the force on specific area on the plate (rectangular area). My assumption is to make the impactor to be rigid and apply force on the impactor (10KN divided by number of nodes of the impactor). I expected the rigid body to transfer the load to the plate. It works; however, I don't get the same result when I apply the forces directly on the plate on the same area by manually selecting nodes using node sets. What I feel is that the impactor doesn't transfer all the load to the plate. Can you give a tip what contacts I have to use when the impactor touches the plate they go along together and transfer the whole load?
It depends on the load whether it is dynamic or static. If it is static load, then all should be transferred. If the load is dynamic, then there might be some load loss due to the intertia of the impactor. Automatic surface to surface should be fine. If there is separation between the impactor and plate after the initial impact then it means the load rate is too fast and/or the material properties are very soft.
@@AmeenTopa Thank you so much for your prompt reply as always. The load is static.I can show you my result in both cases if you give me your e-mail address. How do you define the load rate correctly? Is there any good practice to define the value for static and dynamic analysis? Thank you so much!
@@mulukenmeaza4844 Sorry, TH-cam has automatically removed your comment. When you right your email address, don't put @, instead you can write youremailadress_at_hotmail_dot_com
Great work man. I appreciate your effort in providing knowledge to us. Similar work I have done, but I am not getting, what is "Tensile Stress Cut-off"?
@@vaibhavnmete I have never done similar simulation before. I am planning to do Blast with ALE method though. You can refer to this paper: www.dynamore.de/de/download/papers/2012-internationale-ls-dyna-users-conference/documents/blast-impact06-a.pdf
You are welcome, I tell you the truth that composite is not my expertise and field of study. I am still learning it and I am not comfortable putting a tutorial on something that I am not master in it. Yeah, I am planning to do so once I get deeper understanding in composite materials.
Great tutorial, thank you! I have been trying to simulate compression of different densities of EPS blocks that are impacted by a steel bar (50J kinetic energy). I'm particularly interested in ensuring model stability at the point where the foam bottoms out. I've used your 2014 paper as reference for the basic model setup, and stress strain data from compression experiments on my material, but cannot achieve realistic behaviour. I've tried adding *CONTACT_INTERIOR and changing the contacts from *AUTOMATIC_SURFACE_TO_SURFACE to NODES_TO_SURFACE. I have not yet tried adding *MAT_ADD_EROSION as I've set ERODE = 1 in *CONTROL_TIMESTEP. I still get negative volumes and weird deformations at high strain (>95%). I've tried HEX elements (ELFORM 1) and TET elements (ELFORM 10 and 13). Any suggestions on what to look at?
I see that you've tried many things. Have you tried extending the stress strain curve exponentially after the last point from the experiment? "Cannot achieve realistic behaviour", what is the realistic behaviour and what is the behaviour that you are getting?
@AmeenTopa thanks for the quick reply. Yes, I've extrapolated the stress-strain curve to 99% strain. Two things: 1. The EPS folds around the wedge shape bar impactor, like a very soft material, where in the high speed video of the experiment it seems more like an indentation. I have a load cell to measure the reaction force, but haven't been able to compare the simulation vs experiment as the simulation terminates prior to bottoming out. 2. Elements at the bottom centre if the block start stretching and the element width stretches about 150%. If I increase the Tensile Stress Cutoff, issue 2. Is improved, but 1. Worsens. My expectation is that the material would "pancake" at the centre part of the steel wedge impactor with minimal elastic recovery, leaving an "imprint" of the impactor in the EPS block.
You may try MAT ADD EROSION as in my paper. Also, it could be that the used stress strain data in the input is at a lower strain rate compared to that of the impact test.
Thank you for this helpful video package. Can you please explain why we defined node set on the core but segment set on the upper and lower plates prior to connecting them? Why not segment set on both or node set on both? I would appreciate if you explain. Thank you in advance.
Thank you for your informative and detailed videos, this one was also very useful to me. I am modelling aircraft seats to be integrated into a fuselage to analyse a drop test with dummies. Some papers I found suggest using MAT57 card for seat foam. Which approach do you think is best suited to my case? Mat57 or Mat63 like the one in the video? Also, what is the main role of the contact_interior? Is it also important to set it in my case?
MAT063 or MAT63 is for crushable foam, where recovery is very little. If there is significant recovery in the foam, it is better to use MAT057. Most car model files use MAT057 for the seat cushions. As for the contact interior, it is needed as a measure to prevent negative volume error, which occurs when you have severe deformation. Hope that helps! Do subscribe to my channel! 😀
If you are using implicit static analysis, then yes you are right. However, if you are using explicit solver or implicit dynamic analysis, then no need to fix in the y direction. The friction and the interia will keep the specimen from moving in y direction.
Dear Shova, This is an advanced topic and my videos here are for beginners. Unfortunately, I cannot fulfill your request due to my time constraints. With that being said, I give classes on specific topics such as composites. If you are interested, you can contact my team at the following: sites.google.com/view/topacademyofficial/about-topacademy All the best.
Is the s-s graph of the data for LCID a compression test, a tensile test, or a bending test? What graph does it insert? Also, can I put the EPS foam, the shock absorbing foam you provided on TH-cam, into the LCID?
Good afternoon, Ameen! In dynamic implicit analysis, compression of a foam cube works perfectly and according to the results, the graph of the deformation rate in time looks perfect and converges with the calculated one for the entire test interval (compression). But with explicit modeling of the same process, the graph of the dependence of the strain rate on time looks quite strange and after a certain deformation begins to "jump" very much, which affects, respectively, the results of stress determination (since several curves are laid for different speeds). I tried to change the contact and do it without contact, applying speed to the upper nodes of the cube, the effect is the same. Obviously there is some kind of error in the calculation. I use tetra elements. Can you tell me in which direction you can move to eliminate such fluctuations in the deformation rate?
Hello, Ameen! I'm sorry to bother you.. Can you tell me approximately in which direction to work to fix the problem described in the previous letter? Perhaps it is necessary to configure any parameters of explicit analysis? Or the properties of the elements? Thank you in advance for the answer.
You need to buy the licence from LSTC or ANSYS company. You can search on the ANSYS website for your local distributor. Alternatively, you can download the free version of the solver. It comes with an interface called LS-RUN. I have a tutorial on that, search for it on my channel.
Thank you for the great video. I have a couple of questions. Where did the values of minpres = -3.5E-5, and max. strain value of 0.15 come from This value does not match any of the foam properties noted in your paper. Are they coming from your paper's Fig. 2 and Table 1? So, in general, what is meant by "pressure" value in the erosion card? Is it the same as the stress value (if so, which stress)? Moreover, you put a negative sign in front ofo the value; however, the sentence in the manual, which is very confusing, says: "P>Pmin where P is the pressure (positive in compression), and Pmin is the pressure at failure" I would really appreciate your response. Again thank you for making such amazingly detailed and instructive videos.
The values that I used in this example are only for demonstration purposes. You should refer to the papers if you want to validate your simulation. Pressure here means hydrostatic pressure, which is the average of SigX, SigY, and SigZ. If we say stress, then it includes normal stress and shear stress. But the hydrostatic pressure considers only the normal stresses. Negative pressure means compressive condition while positive pressure means tensile condition.
@@AmeenTopa I thank you for your relatively fast response; really appreciated it. FYI, I found the following information that explains the variables in more detail, FY and for others that may be as confused as I was!: mxpres: the maximum hydrostatic pressure should be taken as a positive value, representing pressure. The option is used for controlling the compression failure. mnpres: contrary to mxpres, it is used for controlling tensile failure, generally taking negative value. mxeps: the extreme value of principal strain is used for controlling compression failure, generally taking positive value. mneps: contrary to mxeps, it should be taken as a negative value. This option is used for controlling tensile failure.
For those who don't have workbench, and want to use LS-DYNA. And as far as I know, LS-DYNA gives you more control of the material modelling and properties. More options on how to describe the material behavior.
Hello Sir, I want to do crash analysis of helmet in LS DYNA, so it has basically three parts, visor, outer shell, impact absorbing material and then comforting foam, which are made of ABS foam, polystyrene, polyurethane. I have to impact the helmet at different velocities ranging from 5 to 10 m/s on an anvil, and then Charphy izod test and then to calculate the Head Injury Criterion, can you please guide me how to do it, it will be very helpful.
First, you can watch all my tutorials to get a hand on the software. From there, I think you can learn more by yourself. I see my tutorials as the ABC for LS-DYNA. Once you learn the alphabets and you can read, you won't need the teacher to tell you how to read every single word in the dictionary.
You are talking about negative volume error at 17:00. You extended the curve. How did you extend it by using experimental results or mathematical formula something like that ?
Dear Topa, using the specified contact types (also the one at the end of the video), my impactor (punch) is going THROUGH the foam. Why this might happen? Thanks!
Can you explain the contact stiffness coefficient to me? It is known as penetration amount = contact area * contact stiffness coefficient. Also, I understand that increasing the contact stiffness coefficient improves the contact time. Can you tell me what the exact meaning is?
@@김창호기계공학과 you can refer to the link below for more theoretical information about the contacts: www.dynasupport.com/tutorial/contact-modeling-in-ls-dyna/contact-stiffness-calculation
@@AmeenTopa Thank you and i want to ask you one more . If I were to draw an F-D curve during a drop test on a flat plate, would it be correct to place F as contact force and displacement at the node on the hitting surface?
@@김창호기계공학과 You are welcome. With regard to your question: the force is correct. The displacement should be the point where you put the sensor in the experiment. I hope this helps.
I performed sensitivity analysis on the unloading parameters HU and Shape Factor using only one model that compresses a single element. However, in the case of Shape Factor, it was confirmed that the unloading behavior changes well as the value is changed (Shape Factor is performed from 1 to 30), but Hu Factor is set to (1e-3, 1e-2, 1e-1, 1). We confirmed that all numbers were the same after making the change. In the case of the original HU factor, does the Hu curve not change significantly when changed?
Hi. In my analysis i dropped crushable foam on fixed rigid block. I have defined nodes to surface contact. still its not detecting contact and foam block is passing through rigid base. What might be the reason?
Check the material properties. There might be a typo. Read this blog post for more about this: www.d3view.com/best-practices-for-modeling-recoverable-low-density-foams-by-example/
Hello Ameen, I was trying to recreate foam-missile impact test based on your paper on crushable foam. My model is running fine till 20ms later on hourglass energy kicking in and my depth of penetration of missile is exceeding after 40 ms. It would be of great help to me if you share .k file for settings reference. Thanks in advance.
Yes, I will explain. This value is the tensile stress limit. Meaning, if you do a tensile test on the polystyrene, the stress strain will drop after it reaches this cutoff value. However, take note that the elements that reach this limit will not be deleted. The value is taken from literature. Check out my papers on Polystyrene for more reading.
@@AmeenTopa Wow, That was an incredibly quick reply. I appreciate it. Yes, I am currently reading your research. I am modelling a helmet with EPS foam in LS-Dyna. The foam that I am using is quite stiffer than what you have here. The density of the foam is 31.2 kg/m3 and E value is around 12 MPA. I guess I will have to read your paper completely in order to get a gist of how to calculate corresponding tensile cut off for my stress strain data. Unfortunately the stress strain data I have is from a research paper and not something I obtained. Also, I used the trend line polynomial of 6th order feature in excel to expand my data set to 100% strain. Do you think this expansion of data creates further implications with the accuracy of model ? Oh btw thanks for the meshing video on the helmet pad. The challenge that I face right now is to mesh a lattice structure for impact. I am trying to hex mesh it but given the complexity of the geometry I am not entirely sure how to. I am using Hypermesh to mesh it.
@@yashsurana6663 I am doing research on helmet padding too. Regarding the tensile cutoff, some articles provide that value. Extending the stress strain curve is necessary to prevent negative volume. Most reference give the curve only up to 80% compression. If the experimental curve is given until 100%, then we wouldn't need to extrapolate the curve and modify it. However, compressing 100% is not practical experimentally. I also have a published paper about lattice structure, the geometry was made using solidworks then imported and meshed with LS-Prepost. I have made a tutorial on how to simplify the solid mesh of the lattice to beam elements. If it is possible, we can have a research collaboration so I can assist you further.
Oh that's fantastic! Are you trying to prepare a fea model for helmet impact or testing out new materials for the helmet pads? I am basically creating a reliable helmet fea model and looking at hic (head injury criteria) scores for validation. End goal would be to try different pad structures with different materials. We can definitely talk, if you have any availability this weekend or next week after Tuesday. Where shall we connect? Thanks!
If material A (shell element) and material B (solid element) are connected but do not share nodes, is it common to use contact tied shell to solid? I assume they are connected by welding.
Hello, how did you define the DAMP value? The aircraft arrestor page you referred to defined it as 1e-4 whereas in your paper and video it is 0.5. Thanks!
@@Akash015 You can check here in my article: www.hindawi.com/journals/mse/2014/292647/ Also, here: U. E. Ozturk and G. Anlas, “Finite element analysis of expanded polystyrene foam under multiple compressive loading and unloading,” Materials and Design, vol. 32, no. 2, pp. 773-780, 2011.
Good afternoon, Ameen! Please tell me how to fix the problem of overlapping elements in LS-DYNA (when one element of a part penetrates into an element of another part). For example, there is a metal pin in the plate of their foam and some elements of the pin penetrate into the elements of the foam channel. Are there any options on how to fix this automatically without resorting to deleting elements and manually editing the grid. These elements are few, a few pieces. Thanks!
It depends on the application.ore specifically, the size of the model. 5km/h for an airplane is not the same as 5km/h for a toy car. I hope you get the idea.
If you have an impact simulation, or there are instabilities in the contact, then there will be noise in the force. And if your DT in DATABASE RCFORC is not small enough, then you won't be able to capture this noise. For quasi static analysis, there should be no or minimum noise in the contact forces.
Good afternoon, Ameen! Let me ask you about this lesson. In the material model, you load the stress curve (MPa or GPa, not very important) - deformation (% or fractions). Is that true? The description of the material indicates that you need to specify the yield stress versus volumetric strain curve.. Is this the same as stress-strain? If not, then how to calculate yield stress and volumetric strain, since we have a standard experimental force-displacement graph. Thank you in advance!
@@vladimirlubimov2318 Yes. For Crushable foam materials, the elastic region is very insignificant. Thus, we can assume that the whole stress strain curve (from experiment) as the yield stress. As for the volumetric strain, because the Poisson's ratio is very little for open-cell foams, we can approximate the 1D strain (from experiment) as the volumetric strain...the lateral deformation (thus, lateral strain) are negligible.
@@R.-RitaR to reduce the size of the elements, you can use the element tools to split the elements. To increase the size of the elements, you need to rebuild the model.
That's a good question. With the material used (MAT063), the unloading and loading paths are identical. For a different unloading pattern, a different material model can be used..
@@AmeenTopa umm ,, i must plot unload curve for the destification zone on foam core , so i think that i should use fu chang foam mat card which apply the unload curve but i am not good at ls dyna so i want help,, can you help me ?
@@김창호기계공학과 it's difficult to guide you here in the comments section. Please email the details to my team at feadynamicconsultants@outlook.com or contact me directly on Facebook or LinkedIn.
Hi Ameen, big fan of your work. I have some questions that hopefully you can help me. I am modeling a rc beam that will be subjected to a blast load. Then I will apply and maintain a load on the entire top surface of the beam. I am trying out prescribed motion set and load node set to apply the loading. However, I have not been successful in maintaining the load on the beam. Is my method of loading wrong?
@@AmeenTopa Is there a reason why prescribed motion set and load node set is not suitable for loading a beam? Also, I don't think I am able to use rigid setting as I am MMALE solver for my project
@@トフ戦士 actually I don't quite understand why did you mean when you said "cannot maintain the load". I request elaboration. Anyway, it is always better to create the model as close as possible to the actual physical problem. In the real test, when apply the force from a machine and this machine as a punch and support which can be of various shapes and sizes. If we use load node set or prescribed motion set on the beam itself, then we cannot consider the effect of the tools shape.
Brother, can you give me tips for reducing running time ? Here i got estimated clock time to complete is 30 hours (my processor is Ryzen 7) I use 10 seconds of termination time with 1 second interval output time. The model is just simple, it is a reinforced concrete beam with one point load with one 1 boundary set (fixed point) The thing is i just want to know the shape of the model after being loaded and it's just that, at this point, I don't really care much about reaction forces, stresses, displacements, etc, yet. I'm affraid that program is doing too many calculations that i don't want it yet.
The load is quasi static or dynamic? If the termination time is 10 seconds, then I believe the load is very small and it is a quasi static problem. For this, it is better to use implicit solver. Check my axial tube crush video and cylinder compression video to see how to use implicit.
Hello sir. I am doing Crushable Foam Solid with MAT005 and MAT063. I have an error [negative solid element]. Can you help me to fix this problem? Thank you
According to my knowledge: Nodes to surface can be used to link SPH with Solid Elements and to link Solid Elements with Solid Elements (as in this video). Surface to Surface to surface cannot be used with SPH cos SPH has no surfaces.
I already have a tutorial on three point bending. Check that one. Making four point bending is not that different. There point bending of sandwich structure with EPS core.
brother ameen, i've met a problem on helmet crush sim, the helmet have three layers which is shell, foam and plastic inner generally the inner and foam will penetrate each other, so i moved the foam and shell to only use the plastic inner, it will still penetrate itself, i've tried single surface contact to deal with its self contact, it wont work, and i dont now what to do
Make sure the properties of the foam is correct. Check my article about crushable foam. Check this blog post: www.d3view.com/contact-interior-for-foams-honeycombs-and-rubbers/
@@AmeenTopa sry ameen, i may not clarify my problem. currently i've removed the foam and shell, so there's only anvil, head model and plastic pad left, but the pad still penetrate itself.
That's a very general question, what do you mean exactly by hollow structures? Anyway, you can use implicit analysis with macro-scale approach: meaning you do not model the voids inside the material, rather you chose a constitutive material model which can capture the behavior of these types of materials. If you want to model the inside of the material (hollo and voids), then using implicit analysis is still possible, but it would take a very long time to run the model due to small mesh size. This is what has been done in my article about lattice structures: doi.org/10.1016/j.mtcomm.2020.101563
@@AmeenTopa thank you very much for the detailed reply. Here you have used tetra mesh with this full lattice structure. I am also trying to simulate same kind of a structure for quasi static tests. I am ending up with "material model failed iterate" error message. I used MAT_3. Since I have tensile and compression test data for the polymer material, what material model will work as per your experience? or Where else would be the cause of error?
@@AmeenTopa I agree. However you have mentioned in above paper, the numerical model has showed deficiency in densification region. So what can I do to resolve that? what would work for it such as defining interior contact, etc?
Hello again. I modeled this beam. I defined contact between the core and surfaces and meanwhile I merged the duplicate nodes. The run time is 16 hours. Did I make mistake?
@@kasratakbiri3265 LS-DYNA is default on dynamic analysis which is very short in period. Problems that are long than 0.1 - 0.5 seconds are considered long. Thus if that's the case, then you need to use Implicit Solver. However, if your run time is small, like 0.001 seconds or 10 milliseconds, but still it takes too long to solve, then you need to check your model. Check the properties of the material, and the quality of your mesh. Elements should not have poor aspect ratios.
There is no way to make the mesh more coarse, but there is a way to refine the mesh (make the elements smaller) this is done using Element Tools, Edit Elements, Split.
hello, I asked a question about foams in LS-DYNA google group and you sent me two papers of yours. I read them and I have two questions about them. I will be grateful if you can give me your email address so I can ask them.
Thank you Ameen Topa, this tutorial will be useful for engineers, can you make the same video for a composite sandwich structure which includes face sheet(carbon fiber, fiberglass) and honeycomb(Nomex, aluminum) ? Kind regards
Please share my tutorials if you find them useful. With more shares and views, I will be more motivated to do more and more videos! :D
I got lots of requests in my list. I will add yours to the list. Sure one day it will come.
Good afternoon, Ameen. Thank you very much for the tutorial video, thanks to them I have become much better at modeling. I have two questions for you:
1) Could you make a video in which you showed how to use the basic tools of LS-DYNA (for example, editing geometry, building a grid on a 3D model, measuring distances between points, planes, and more).
2) Please advise which material model can be used to model a polymer material (sealant, mastic), for example, such as is used for vibration isolation of the car body or for sealing the seams of the cooling system of the car.
I am very grateful and grateful to you in advance. You're doing a wonderful job!!
Good evening. You are welcome.
1) For the basic tools, unfortunately, I don't have a specific tutorial for that. However, I have covered most of the editing tools in my tutorial playlist: LSDYNA BASIC TUTORIALS.
2) This is a hyper elastic material. You can use material models such as MAT MOONEY RIVILIN.
Unfortunately, I don't make any requests anymore due to my limited time. However, I do take paid consultation and training jobs, if you are willing to pay.
@@AmeenTopa Thanks for the tips. Can you tell me how a paid consultation works? And how much will it cost approximately? Thanks.
@@vladimirlubimov2318 It depends on the complexity of the project. Please email us the details of the project. You can find our contacts in the site below:
sites.google.com/view/topacademyofficial/about-topacademy
Thank you vey much. I am enjoying so much your videos. I am in situation that I have to apply load on the specific area using rigid body impactor. My plate is refined mesh and the impactor is course mesh. I choose the impactor because I can simply change the mesh of my plate and I don't have to select the node set where i apply the load manually. So, I have tried to apply force on the plate using rectangular box so that I can have the force on specific area on the plate (rectangular area). My assumption is to make the impactor to be rigid and apply force on the impactor (10KN divided by number of nodes of the impactor). I expected the rigid body to transfer the load to the plate. It works; however, I don't get the same result when I apply the forces directly on the plate on the same area by manually selecting nodes using node sets. What I feel is that the impactor doesn't transfer all the load to the plate. Can you give a tip what contacts I have to use when the impactor touches the plate they go along together and transfer the whole load?
It depends on the load whether it is dynamic or static. If it is static load, then all should be transferred. If the load is dynamic, then there might be some load loss due to the intertia of the impactor.
Automatic surface to surface should be fine. If there is separation between the impactor and plate after the initial impact then it means the load rate is too fast and/or the material properties are very soft.
@@AmeenTopa Thank you so much for your prompt reply as always.
The load is static.I can show you my result in both cases if you give me your e-mail address.
How do you define the load rate correctly? Is there any good practice to define the value for static and dynamic analysis?
Thank you so much!
You can find my contact from the banner picture of my channel page. Alternatively, you can put your email here and I will follow up in my free time.
@@mulukenmeaza4844 Sorry, TH-cam has automatically removed your comment. When you right your email address, don't put @, instead you can write
youremailadress_at_hotmail_dot_com
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Great work man. I appreciate your effort in providing knowledge to us. Similar work I have done, but I am not getting, what is "Tensile Stress Cut-off"?
You may refer to the theory manual here:
www.lstc.com/dynamat/pdfs/mat_063_theory.pdf
Can you do it blast using SPH model, where SPH can be referred as TNT?
@@vaibhavnmete I have never done similar simulation before. I am planning to do Blast with ALE method though.
You can refer to this paper:
www.dynamore.de/de/download/papers/2012-internationale-ls-dyna-users-conference/documents/blast-impact06-a.pdf
@@AmeenTopa can I get your e-mail id, I have some queries about citing your paper.
Appreciated your great work and sharing your modeling knowledge.
My pleasure! please support my channel grow (more subscribers) so I can post more free tutorials!!!
Thank you for your tutorial. Can you please add a tutorial that cover composite materials and their fiber orientation.
Regards,
You are welcome, I tell you the truth that composite is not my expertise and field of study. I am still learning it and I am not comfortable putting a tutorial on something that I am not master in it.
Yeah, I am planning to do so once I get deeper understanding in composite materials.
Please shear my tutorials if you find it useful. With more shares and views, I will be more motivated to do more and more videos! :D
Thank you very much Ameen, of course I will share your tutorials with my peers 😉
Keep on the good work man!
thanks man
Great tutorial, thank you! I have been trying to simulate compression of different densities of EPS blocks that are impacted by a steel bar (50J kinetic energy). I'm particularly interested in ensuring model stability at the point where the foam bottoms out. I've used your 2014 paper as reference for the basic model setup, and stress strain data from compression experiments on my material, but cannot achieve realistic behaviour. I've tried adding *CONTACT_INTERIOR and changing the contacts from *AUTOMATIC_SURFACE_TO_SURFACE to NODES_TO_SURFACE. I have not yet tried adding *MAT_ADD_EROSION as I've set ERODE = 1 in *CONTROL_TIMESTEP. I still get negative volumes and weird deformations at high strain (>95%). I've tried HEX elements (ELFORM 1) and TET elements (ELFORM 10 and 13). Any suggestions on what to look at?
I see that you've tried many things. Have you tried extending the stress strain curve exponentially after the last point from the experiment?
"Cannot achieve realistic behaviour", what is the realistic behaviour and what is the behaviour that you are getting?
@AmeenTopa thanks for the quick reply. Yes, I've extrapolated the stress-strain curve to 99% strain.
Two things: 1. The EPS folds around the wedge shape bar impactor, like a very soft material, where in the high speed video of the experiment it seems more like an indentation. I have a load cell to measure the reaction force, but haven't been able to compare the simulation vs experiment as the simulation terminates prior to bottoming out.
2. Elements at the bottom centre if the block start stretching and the element width stretches about 150%.
If I increase the Tensile Stress Cutoff, issue 2. Is improved, but 1. Worsens.
My expectation is that the material would "pancake" at the centre part of the steel wedge impactor with minimal elastic recovery, leaving an "imprint" of the impactor in the EPS block.
You may try MAT ADD EROSION as in my paper. Also, it could be that the used stress strain data in the input is at a lower strain rate compared to that of the impact test.
True, test data is quasi-static and impact velocity is 7.5m/s. Thanks for your help, if I find the problem I'll share it here.
Thank you for this helpful video package.
Can you please explain why we defined node set on the core but segment set on the upper and lower plates prior to connecting them? Why not segment set on both or node set on both? I would appreciate if you explain.
Thank you in advance.
This is because of the contact type: nodes to surface.
Set nodes to surface segment.
very successful and comprehensive work, thank you.
thank you very much. Please share with your friends.
Thanks for the tutorial. Much appreciated your work.
You are welcome!
Thank you for your informative and detailed videos, this one was also very useful to me. I am modelling aircraft seats to be integrated into a fuselage to analyse a drop test with dummies. Some papers I found suggest using MAT57 card for seat foam.
Which approach do you think is best suited to my case? Mat57 or Mat63 like the one in the video?
Also, what is the main role of the contact_interior? Is it also important to set it in my case?
MAT063 or MAT63 is for crushable foam, where recovery is very little. If there is significant recovery in the foam, it is better to use MAT057.
Most car model files use MAT057 for the seat cushions.
As for the contact interior, it is needed as a measure to prevent negative volume error, which occurs when you have severe deformation.
Hope that helps! Do subscribe to my channel! 😀
@@AmeenTopa Thanks for your reply, it clarified my doubts. Your work with video tutorials is really helpful, please keep it up.
Thanks, Ameen. In Tutorial 10, should we fix the Sandwich beam in the Y axes?
I think It can move when we apply the load.
If you are using implicit static analysis, then yes you are right.
However, if you are using explicit solver or implicit dynamic analysis, then no need to fix in the y direction. The friction and the interia will keep the specimen from moving in y direction.
Thank you, sir. Can you please make a tutorial about a bullet impacting a multi-layer composite plate?
Dear Shova,
This is an advanced topic and my videos here are for beginners. Unfortunately, I cannot fulfill your request due to my time constraints.
With that being said, I give classes on specific topics such as composites. If you are interested, you can contact my team at the following:
sites.google.com/view/topacademyofficial/about-topacademy
All the best.
@@AmeenTopa Alright Sir. Thank you.
Is the s-s graph of the data for LCID a compression test, a tensile test, or a bending test? What graph does it insert?
Also, can I put the EPS foam, the shock absorbing foam you provided on TH-cam, into the LCID?
For MAT063, the data is from compression test.
Please refer to my thesis and papers for further details.
Good afternoon, Ameen! In dynamic implicit analysis, compression of a foam cube works perfectly and according to the results, the graph of the deformation rate in time looks perfect and converges with the calculated one for the entire test interval (compression). But with explicit modeling of the same process, the graph of the dependence of the strain rate on time looks quite strange and after a certain deformation begins to "jump" very much, which affects, respectively, the results of stress determination (since several curves are laid for different speeds). I tried to change the contact and do it without contact, applying speed to the upper nodes of the cube, the effect is the same. Obviously there is some kind of error in the calculation. I use tetra elements. Can you tell me in which direction you can move to eliminate such fluctuations in the deformation rate?
Hello, Ameen! I'm sorry to bother you.. Can you tell me approximately in which direction to work to fix the problem described in the previous letter? Perhaps it is necessary to configure any parameters of explicit analysis? Or the properties of the elements? Thank you in advance for the answer.
Hello sir, thank you for this helpful video. How do you get LS DYNA program manager? I just have free access to PrePost. Thanks!!
You need to buy the licence from LSTC or ANSYS company. You can search on the ANSYS website for your local distributor.
Alternatively, you can download the free version of the solver. It comes with an interface called LS-RUN. I have a tutorial on that, search for it on my channel.
Thank you for the great video. I have a couple of questions. Where did the values of minpres = -3.5E-5, and max. strain value of 0.15 come from This value does not match any of the foam properties noted in your paper. Are they coming from your paper's Fig. 2 and Table 1?
So, in general, what is meant by "pressure" value in the erosion card? Is it the same as the stress value (if so, which stress)? Moreover, you put a negative sign in front ofo the value; however, the sentence in the manual, which is very confusing, says: "P>Pmin where P is the pressure (positive in compression), and Pmin is the pressure at failure"
I would really appreciate your response.
Again thank you for making such amazingly detailed and instructive videos.
The values that I used in this example are only for demonstration purposes. You should refer to the papers if you want to validate your simulation.
Pressure here means hydrostatic pressure, which is the average of SigX, SigY, and SigZ. If we say stress, then it includes normal stress and shear stress. But the hydrostatic pressure considers only the normal stresses.
Negative pressure means compressive condition while positive pressure means tensile condition.
@@AmeenTopa I thank you for your relatively fast response; really appreciated it.
FYI, I found the following information that explains the variables in more detail, FY and for others that may be as confused as I was!:
mxpres: the maximum hydrostatic pressure should be taken as a positive value, representing pressure. The option is used for controlling the compression failure. mnpres: contrary to mxpres, it is used for controlling tensile failure, generally taking negative value. mxeps: the extreme value of principal strain is used for controlling compression failure, generally taking positive value. mneps: contrary to mxeps, it should be taken as a negative value. This option is used for controlling tensile failure.
@@zackvizeman5329 You are welcome. Glad that things are clear for you now and thanks for sharing the detailed explanation.
it just easiely to do in workbench. why did you choose this?
For those who don't have workbench, and want to use LS-DYNA.
And as far as I know, LS-DYNA gives you more control of the material modelling and properties. More options on how to describe the material behavior.
Hello Sir, I want to do crash analysis of helmet in LS DYNA, so it has basically three parts, visor, outer shell, impact absorbing material and then comforting foam, which are made of ABS foam, polystyrene, polyurethane. I have to impact the helmet at different velocities ranging from 5 to 10 m/s on an anvil, and then Charphy izod test and then to calculate the Head Injury Criterion, can you please guide me how to do it, it will be very helpful.
First, you can watch all my tutorials to get a hand on the software. From there, I think you can learn more by yourself.
I see my tutorials as the ABC for LS-DYNA. Once you learn the alphabets and you can read, you won't need the teacher to tell you how to read every single word in the dictionary.
You are talking about negative volume error at 17:00. You extended the curve. How did you extend it by using experimental results or mathematical formula something like that ?
Check out this blog post:
www.d3view.com/best-practices-for-modeling-recoverable-low-density-foams-by-example/
How you get the load curve ID for the crushable foam
Dear Topa, using the specified contact types (also the one at the end of the video), my impactor (punch) is going THROUGH the foam. Why this might happen? Thanks!
Please check if you followed the tutorial exactly. Others has followed my tutorial and didn't face this problem.
why didn't you apply the gravity load : Rigid Load
In general, the gravity load can be ignored in the simulations of lab-scaled specimen.
Can you explain the contact stiffness coefficient to me?
It is known as penetration amount = contact area * contact stiffness coefficient.
Also, I understand that increasing the contact stiffness coefficient improves the contact time. Can you tell me what the exact meaning is?
@@김창호기계공학과 you can refer to the link below for more theoretical information about the contacts:
www.dynasupport.com/tutorial/contact-modeling-in-ls-dyna/contact-stiffness-calculation
@@AmeenTopa Thank you and i want to ask you one more . If I were to draw an F-D curve during a drop test on a flat plate, would it be correct to place F as contact force and displacement at the node on the hitting surface?
@@김창호기계공학과 You are welcome.
With regard to your question: the force is correct. The displacement should be the point where you put the sensor in the experiment.
I hope this helps.
Can u share about composite modelling ( materials, directional, layer etc)
Check my video: Concrete Column Wrapped with Composite Laminates
@@AmeenTopa thank u, ı will
Do you have Implicit 3 point bending LS-DYNA
You can check my axial tube crush and compression test tutorial to see the IMPLICIT keywords needed.
@@AmeenTopa Thank You
@@AmeenTopa it show *** Error 60004 (IMP+4)
*********************************************************
* *
* - FATAL ERROR - *
* *
* Nonlinear solver failed to find equilibrium. *
* *
********************************************************* how fix it
@@พีรพัฒน์กิตติศักดิ์ไพรัช If you are doing three point bending, then you need to fix one side of the specimen from sliding along the tools.
I performed sensitivity analysis on the unloading parameters HU and Shape Factor using only one model that compresses a single element. However, in the case of Shape Factor, it was confirmed that the unloading behavior changes well as the value is changed (Shape Factor is performed from 1 to 30), but Hu Factor is set to (1e-3, 1e-2, 1e-1, 1). We confirmed that all numbers were the same after making the change. In the case of the original HU factor, does the Hu curve not change significantly when changed?
It might be the loading and unloading are not done properly. You need to apply LOAD NODE SET or LOAD RIGID BODY on the impactor or punch.
Hi. In my analysis i dropped crushable foam on fixed rigid block. I have defined nodes to surface contact. still its not detecting contact and foam block is passing through rigid base. What might be the reason?
Check the material properties. There might be a typo.
Read this blog post for more about this:
www.d3view.com/best-practices-for-modeling-recoverable-low-density-foams-by-example/
Thanks for the response. Will go through it.
Hello Ameen, I was trying to recreate foam-missile impact test based on your paper on crushable foam. My model is running fine till 20ms later on hourglass energy kicking in and my depth of penetration of missile is exceeding after 40 ms. It would be of great help to me if you share .k file for settings reference. Thanks in advance.
@@chanduiithyd put your email here and I will follow up in my free time.
@@AmeenTopa Its chandrasekharp6@gmail.com Thanks for your response.
Hello Ameen, Can you please expound on why you used that particular tensile cut off value, and how exactly this affects the sim?
Yes, I will explain.
This value is the tensile stress limit. Meaning, if you do a tensile test on the polystyrene, the stress strain will drop after it reaches this cutoff value. However, take note that the elements that reach this limit will not be deleted.
The value is taken from literature. Check out my papers on Polystyrene for more reading.
@@AmeenTopa Wow, That was an incredibly quick reply. I appreciate it. Yes, I am currently reading your research. I am modelling a helmet with EPS foam in LS-Dyna. The foam that I am using is quite stiffer than what you have here. The density of the foam is 31.2 kg/m3 and E value is around 12 MPA. I guess I will have to read your paper completely in order to get a gist of how to calculate corresponding tensile cut off for my stress strain data. Unfortunately the stress strain data I have is from a research paper and not something I obtained. Also, I used the trend line polynomial of 6th order feature in excel to expand my data set to 100% strain. Do you think this expansion of data creates further implications with the accuracy of model ? Oh btw thanks for the meshing video on the helmet pad. The challenge that I face right now is to mesh a lattice structure for impact. I am trying to hex mesh it but given the complexity of the geometry I am not entirely sure how to. I am using Hypermesh to mesh it.
@@yashsurana6663 I am doing research on helmet padding too. Regarding the tensile cutoff, some articles provide that value. Extending the stress strain curve is necessary to prevent negative volume. Most reference give the curve only up to 80% compression. If the experimental curve is given until 100%, then we wouldn't need to extrapolate the curve and modify it. However, compressing 100% is not practical experimentally.
I also have a published paper about lattice structure, the geometry was made using solidworks then imported and meshed with LS-Prepost. I have made a tutorial on how to simplify the solid mesh of the lattice to beam elements.
If it is possible, we can have a research collaboration so I can assist you further.
Oh that's fantastic! Are you trying to prepare a fea model for helmet impact or testing out new materials for the helmet pads? I am basically creating a reliable helmet fea model and looking at hic (head injury criteria) scores for validation. End goal would be to try different pad structures with different materials. We can definitely talk, if you have any availability this weekend or next week after Tuesday. Where shall we connect? Thanks!
@@yashsurana6663 I may not be available for calls. But you can text me anytime on Facebook messenger, I am online there almost 24/7
If material A (shell element) and material B (solid element) are connected but do not share nodes, is it common to use contact tied shell to solid? I assume they are connected by welding.
I know that if I want something that is stuck together like a sandwich and won't fall off, I have to use tied solid to shell.
@@김창호기계공학과 Yes, you can use CONTACT TIED SURFACE TO SURFACE OFFSET.
@@AmeenTopa and i use it and others are surface to surface thank you
Hello, how did you define the DAMP value? The aircraft arrestor page you referred to defined it as 1e-4 whereas in your paper and video it is 0.5.
Thanks!
DAMP value depends on the velocity of the problem. So there is no fixed value that fits all cases.
@@AmeenTopa thanks for your kind response. Which value of range you suggest to explore for a low velocity car crashing problem?
@@Akash015 You can check here in my article:
www.hindawi.com/journals/mse/2014/292647/
Also, here:
U. E. Ozturk and G. Anlas, “Finite element analysis of expanded polystyrene foam under multiple compressive loading and unloading,” Materials and Design, vol. 32, no. 2, pp. 773-780, 2011.
@@AmeenTopa Thanks brother!
Good afternoon, Ameen! Please tell me how to fix the problem of overlapping elements in LS-DYNA (when one element of a part penetrates into an element of another part). For example, there is a metal pin in the plate of their foam and some elements of the pin penetrate into the elements of the foam channel. Are there any options on how to fix this automatically without resorting to deleting elements and manually editing the grid. These elements are few, a few pieces. Thanks!
Keyword Manager, Model Check, Contact
@@AmeenTopa thank you very much!!
Sir, 5 km/h would be consider low velocity to use hourglass 6?
It depends on the application.ore specifically, the size of the model. 5km/h for an airplane is not the same as 5km/h for a toy car. I hope you get the idea.
I have one question. How can we prescribe a load of 1Kilo N from the punch.
You can try *LOAD RIGID BODY
Hi sir , how to get noisy or shaky graph, does it depends ASCII OPTION AND D3Plot
If you have an impact simulation, or there are instabilities in the contact, then there will be noise in the force.
And if your DT in DATABASE RCFORC is not small enough, then you won't be able to capture this noise.
For quasi static analysis, there should be no or minimum noise in the contact forces.
@@AmeenTopa so DT should be very small , thanks sir
how to visualize the ply details (direction and thickness) of a 8 layered composite plate modelled using shell elements in LS Dyna
As far as I know, there is no way to visualise individual ply details. You only can display the overall thickness of the composite plate.
Good afternoon, Ameen! Let me ask you about this lesson. In the material model, you load the stress curve (MPa or GPa, not very important) - deformation (% or fractions). Is that true? The description of the material indicates that you need to specify the yield stress versus volumetric strain curve.. Is this the same as stress-strain? If not, then how to calculate yield stress and volumetric strain, since we have a standard experimental force-displacement graph. Thank you in advance!
Good afternoon. In my research article, we use nominal stress (= Force/ Cross Section Area) and nominal strain (= Displacement/Height).
@@AmeenTopa thanks. Yes, that is right. So, it is possible to use curve stress-strain for 63 materials, as your article?
Yes, the load curve is a stress-strain curve.
@@vladimirlubimov2318 Yes. For Crushable foam materials, the elastic region is very insignificant. Thus, we can assume that the whole stress strain curve (from experiment) as the yield stress.
As for the volumetric strain, because the Poisson's ratio is very little for open-cell foams, we can approximate the 1D strain (from experiment) as the volumetric strain...the lateral deformation (thus, lateral strain) are negligible.
@@AmeenTopa thank you very much!!
Hello! Сould you tell me, please, how can I quickly reduce the mesh? Or is it necessary to completely rebuild the model?
@@R.-RitaR to reduce the size of the elements, you can use the element tools to split the elements.
To increase the size of the elements, you need to rebuild the model.
@@AmeenTopa Happened)
Thank you very much!
the crushable foam give unload curve?
That's a good question. With the material used (MAT063), the unloading and loading paths are identical. For a different unloading pattern, a different material model can be used..
@@AmeenTopa umm ,, i must plot unload curve for the destification zone on foam core , so i think that i should use fu chang foam mat card which apply the unload curve but i am not good at ls dyna so i want help,, can you help me ?
@@김창호기계공학과 it's difficult to guide you here in the comments section. Please email the details to my team at feadynamicconsultants@outlook.com or contact me directly on Facebook or LinkedIn.
hey,.., i want to ask to you how can i get unload curve for mat 57 , ? i just get force - time curve which show only loading
@@김창호기계공학과 use rcforc to plot the force, and the impactor should be load driven, not displacement driven.
At 13:49 you have video splicing and such a coincidence that after pressing the accept button my program crashed, I had to start over(
Too bad. Make sure to always save regularly.
Hi Ameen, big fan of your work. I have some questions that hopefully you can help me. I am modeling a rc beam that will be subjected to a blast load. Then I will apply and maintain a load on the entire top surface of the beam. I am trying out prescribed motion set and load node set to apply the loading. However, I have not been successful in maintaining the load on the beam. Is my method of loading wrong?
Try use prescribed motion rigid and use a plate to apply the load.
@@AmeenTopa Is there a reason why prescribed motion set and load node set is not suitable for loading a beam? Also, I don't think I am able to use rigid setting as I am MMALE solver for my project
@@トフ戦士 actually I don't quite understand why did you mean when you said "cannot maintain the load". I request elaboration.
Anyway, it is always better to create the model as close as possible to the actual physical problem. In the real test, when apply the force from a machine and this machine as a punch and support which can be of various shapes and sizes. If we use load node set or prescribed motion set on the beam itself, then we cannot consider the effect of the tools shape.
Brother, can you give me tips for reducing running time ? Here i got estimated clock time to complete is 30 hours (my processor is Ryzen 7)
I use 10 seconds of termination time with 1 second interval output time. The model is just simple, it is a reinforced concrete beam with one point load with one 1 boundary set (fixed point)
The thing is i just want to know the shape of the model after being loaded and it's just that, at this point, I don't really care much about reaction forces, stresses, displacements, etc, yet.
I'm affraid that program is doing too many calculations that i don't want it yet.
The load is quasi static or dynamic?
If the termination time is 10 seconds, then I believe the load is very small and it is a quasi static problem. For this, it is better to use implicit solver.
Check my axial tube crush video and cylinder compression video to see how to use implicit.
What software do you use please?
LS-DYNA
Sir..Please mention the website for material card
Kindly check the description of the video.
Hello sir. I am doing Crushable Foam Solid with MAT005 and MAT063. I have an error [negative solid element]. Can you help me to fix this problem? Thank you
Check out my article in the video description.
Dear Ameen, I have one question related to contact. Are there any different between tie nodes to surface and tie surface to surface?
According to my knowledge:
Nodes to surface can be used to link SPH with Solid Elements and to link Solid Elements with Solid Elements (as in this video).
Surface to Surface to surface cannot be used with SPH cos SPH has no surfaces.
hello ameen, can you upload video of four point bending solid FE
structure ?
I already have a tutorial on three point bending. Check that one. Making four point bending is not that different.
There point bending of sandwich structure with EPS core.
brother ameen, i've met a problem on helmet crush sim, the helmet have three layers which is shell, foam and plastic inner generally the inner and foam will penetrate each other, so i moved the foam and shell to only use the plastic inner, it will still penetrate itself, i've tried single surface contact to deal with its self contact, it wont work, and i dont now what to do
Make sure the properties of the foam is correct.
Check my article about crushable foam.
Check this blog post: www.d3view.com/contact-interior-for-foams-honeycombs-and-rubbers/
@@AmeenTopa sry ameen, i may not clarify my problem. currently i've removed the foam and shell, so there's only anvil, head model and plastic pad left, but the pad still penetrate itself.
Okay. It is a self contact problem. You can use AUTOMATIC SINGLE SURFACE, with the plastic as slave. No need for master.
@@AmeenTopa i've tried, but it still not worked
load curve 1 has a vertical slope. I am getting this error
It is clear. Edit LCID 1. It shouldn't have two points which exist on the same X point. For example, it is not allowed to have (0,0) and (0,1)
Can we plot force vs deflection curves using Ls-Dyna?
Yes.
I have two videos on Tensile Test, and one video on Postprocessing with LS-PREPOST, watch them and you will find out how.
@@AmeenTopa thankyou, will do it.
Hi Ameen, Is it possible to simulate quasi static compression of a polymeric hollow structures using implicit analysis?
That's a very general question, what do you mean exactly by hollow structures?
Anyway, you can use implicit analysis with macro-scale approach: meaning you do not model the voids inside the material, rather you chose a constitutive material model which can capture the behavior of these types of materials.
If you want to model the inside of the material (hollo and voids), then using implicit analysis is still possible, but it would take a very long time to run the model due to small mesh size. This is what has been done in my article about lattice structures: doi.org/10.1016/j.mtcomm.2020.101563
@@AmeenTopa thank you very much for the detailed reply. Here you have used tetra mesh with this full lattice structure. I am also trying to simulate same kind of a structure for quasi static tests. I am ending up with "material model failed iterate" error message. I used MAT_3. Since I have tensile and compression test data for the polymer material, what material model will work as per your experience? or Where else would be the cause of error?
@@madhusharukshan7195 I used MAT024. It's difficult to tell what to improve in your model since I don't know what implicit keywords did you used.
@@AmeenTopa I agree. However you have mentioned in above paper, the numerical model has showed deficiency in densification region. So what can I do to resolve that? what would work for it such as defining interior contact, etc?
@@madhusharukshan7195
In general, to improve the model:
1- You can use hexahedral elements instead of tetrahedral.
2- Define single surface contact.
Hello again. I modeled this beam. I defined contact between the core and surfaces and meanwhile I merged the duplicate nodes. The run time is 16 hours. Did I make mistake?
You either define the contact or merge the duplicate nodes. You should not do both.
@@AmeenTopa right. Now that I duplicated the nodes. Is there any way to pull back. Undo it or sth?
@@kasratakbiri3265 You may use Transform, Translate, Copy Element to create new elements. Then delete the old elements.
You also can use Detach tool.
@@AmeenTopa good idea. Thanks brother
Hi, how can I solve the "vertical slope in curves" error in LS-DYNA
Vertical slope means that you have two points or more which are above each other in your curve. You remove this error by delete the points.
@@AmeenTopa Thank you, brother. I did this simulation but it took too long to run. how can I reduce the time that takes for the software to run?
@@kasratakbiri3265 LS-DYNA is default on dynamic analysis which is very short in period. Problems that are long than 0.1 - 0.5 seconds are considered long. Thus if that's the case, then you need to use Implicit Solver.
However, if your run time is small, like 0.001 seconds or 10 milliseconds, but still it takes too long to solve, then you need to check your model. Check the properties of the material, and the quality of your mesh. Elements should not have poor aspect ratios.
Hi I have determined the geometry and now I want to reduce the number of segments or make coarser mesh to reduce the run time. How can I do that?
If you have already created the mesh, then there is no way to make the mesh more coarse. You need to re do the mesh from the start.
@@AmeenTopa oh I'm in big trouble I suppose
There is no way to make the mesh more coarse, but there is a way to refine the mesh (make the elements smaller) this is done using Element Tools, Edit Elements, Split.
@@AmeenTopa I'll give it a try thanks
Where did you get the curve data for foam??
I did experimental work. Check out my paper which is listed in the video description.
@@AmeenTopa what happen if we do not define curve for our material
MAT63 CRUSHABLE FOAM requires a stress strain curve, if not it won't work.
@@AmeenTopa thank you
Welcome. Please share my videos so that more people can get the knowledge! :D
Link to download LS-DYNA:
getintopc.com/softwares/simulators/ls-dyna-free-download/
I think kids were sleeping, Ameen. 🙂 Be quiet
Good night kids. XD
hello, I asked a question about foams in LS-DYNA google group and you sent me two papers of yours. I read them and I have two questions about them. I will be grateful if you can give me your email address
so I can ask them.
You can find me email address in the Google group cos I replied to you there. 🙂
Hi Amir, I replied to you with my email I address. I hope you got that.
@@AmeenTopa yes I got that, thank you.