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Dear there,

 I am currently working on the FSI simulation in LS-DYNA using ALE method. I need to simulate the structure in wind tunnel inflow conditions. Currently, I use the ELFORM=11, AET=4 in *SECTION command to define the inflow Part of the air volume. The inflow parameters are defined by the *EOS of the inflow Part of the air. There are mainly two parameters in *EOS related to the inflow energy or pressure conditions, E0 and V0. I don’t know how to relate the constant inflow velocity, such as 6m/s, with the setting in the model. 

Many thanks for your support and help.

Hello everyone,

I am trying to re-do an implicit analysis I read in a paper. The author recommends "force the contacts" on the initial time step. I am using MORTAR contacts, by the way. Would you happen to know what to do to force the contacts?

Thanks a lot for your time!

Regards,

Nicolas

Hello,

I have a Johnson Cook Model which has the function to transfer the visoplastic work to heat. Currently, I only want to see the temper due to the viscosity effect from Johnson Cook model. Also, I want to set initial temperature for my part.  I want to ignore the heat transfer effect and only want to see the current temperature(initial temperature + temperature by viscosity)

1: To initialize the initial temperature, do I only need to use the Initial_temperatue_set keyword by creating a node-set that includes the nodes of the whole part?

2: Would you let me know what i need to change from my database settings for example database_extent_binary? I think I need to give NEIPH as 14. Do I need to add the control solution and thermal solver?

3: How can I check the temperature contour result in LS Prepost?

Thank you so much!

Best,

Teng

Hi,

We have some issues with running the LS-DYNA solver on our new computer (The license works on the old computer that ran the LS-DYNA solver before, but it is not working on our new computer). 

The problem is that the license was successfully imported into our new computer and the server status is 'running', see the following pictures.

However, when I ran the solver, there was an error that said 'License Problem: Local License: / Error Bad License Keys'. Do you know what the problem is and how do I solve the problem?

Thank you,

Jackie

Hello all!

I am currently developing a wrist model. Following other authors modeling techniques I plan to perform a static simulation. I am new with LS Dyna so I would appreciate some suggestions and general guidance on how to do this.

I previously worked with Abaqus (standard which uses an implicit solver) in which I had the option to enforce a static case by using a keyword and then define a "dummy time" for the load to be applied. I guess the time wasn't really important there because it was a static case.

Within LS Dyna, however, I am not entirely sure what I should do. I am aware that LS Dyna uses an explicit solver by default. I noticed that the results change considerably depending on the time I choose to simulate in *CONTROL_TERMINATION and the curve load defined in *DEFINE_CURVE (a ramp curve together with *LOAD_NODE_SET). I am not sure if this is right so I started exploring the implicit solver since I saw that I can use a static option. So my questions are:

• Can I use both explicit and implicit solvers to perform a static simulation or is there a preferred option?
  • What kind of parameters should I choose for an implicit solver?
  • If possible with explicit (what I have done so far), what variables do I need to check so that this simulation represents a static case or at least a quasi-static one? What about the time I need to simulate until the results stop changing?

Thanks, 

Andres

Hello,

I have a 5 layered model with different materials. All layers should be bonded. I read, that when using shell elements, there should be a sufficient gap between shell and solid to consider the shell thickness (but I could not find how close "sufficient" is). In my model, all Shells have a thickness of 1 mm. I also read, that the algorithm searches for connecting nodes 1/2 of the Shell thickness in normal direction appart from the midsurface line. So I left a gap of 0.5 mm to the respective tied surface. I also set SAST and SBST to -1 mm in order to control the thickness (-0.5 mm did not work). But when running the simulation, I get an error as well as in the message file it reads: "Warning 40538 (SOL+538) Slave node is not constrained no segment was found in bucket sort." In the picture you can see on the left side the mesh on top (no overlapping elements) and the LS Dyna view at the bottom and right the solution after calculation -> the nodes are not TIED together

However, when leaving no gap between Shell elements and the corresponding tied surface, there is no warning message and no error occurs:

This is the contact definition for the first case (gap between Shell and Error/Warning messages):

How should the contact be defined correctly? Is case B (no gap) correct or how can I define the shell thickness for case A in order to tie the nodes together?

Thank you for your support and best wishes

I am trying to model uniaxial compression test of cylindrical specimen using SPG method in LS-Dyna R13.1 in Workbench. I use MAT_024 to define yield stress and MAT_ADD_GISSMO with very small strain to failure (LCSDG) to model "brittle" fracture. IN SECTION_SOLID_SPG I set IDAM = "Programm Controlled" and Self-Contact Indicator (ISC) equal to YES (1). So I hoped that destroyed particles will interact with each other even after specimen crushed.

But when the specimen was crushed the two halves started to move towards each other and I see the penetration of the material (see figures). Therefore the particles don't interact with each other.

Could someone explain why is that so and how can I fix this?

Maybe I have to define glocal contact in the whole model?

I have a small question (may be stupid😂). I am modeling material MAT_024 with a yield stress equal to 5.5 MPa. I want to simulate material brittle fracture using the SPG method and I tried two methods for the definition of material failure criterion:

1. First method is to define IDAM=1 and very small plastic failure strain (say e_f = 0.0001). In that case failure occurs but it seems that bonds between particles are not fully broken. A situation occurs where plastic deformations continue to grow even after the bond is broken. At the same time, the material in the failed zone continues to behave as if it were bonded. Why does this happen? As I understood the SPG mechanism should completely break the bond when reaching the fracture criterion (in this case e_f=0.0001) and a crack should form in the material.
2. The second method is to define MAT_ADD_EROSION (in addition to MAT_024) with criteria of maximum equivalent stress (SIGVM = 5.5 MPa). In that case, I use IDAM = "Programm controlled" in ANSYS Workbench (as I understand it is IDAM=0). The result is a very brittle fracture with no material further deformation and particles are clearly disconnected from each other after failure. Maybe it is appropriate but I can not understand why there is such a big difference with the First method if the SPG bond break mechanism remains the same?
3. Also, I cannot display the fracture zone in LS-PrePost in the Second method since equivalent stress decreases after a fracture. In the First method I used plastic strain bounds (e_p > 0.0001) to change the color of particles with failed bonds. But in 2nd case I can not visualize the zone of destruction, since equivalent stress can't be the criteria for coloring because of decreasing the value after fracture. What can I do in that case? 

Thank you in advance!

Hello! I am trying to use GISSMO model with Smooth Particle Galerkin method in Ansys Workbench 2023R1 and want to clarify some points:

1. Am I correctly understand that the GISSMO model has to be used with a separate plasticity model? In this case the plasticity onset is defined by yield criterion (for example Mises criterion) from the plasticity model (for example MAT_024) and the failure (element or bond deletion) is defined by the curve inside the GISSMO model, right?
2. The GISSMO model uses two different curves -  equivalent plastic strain to localization (e_loc, ECRIT) and equivalent plastic strain to failure (e_f, LCSDG). I am not a good English speaker, so which parameter is bigger e_f or e_loc? As I understand e_f > e_loc, right?
3. What is the "driving quantity" for damage? It is noted in "DTYP" parameter description in Keyword manual? Am I correctly understand that I can use not the plastic strain but any history variable, even from UMAT, to calculate damage (in this case Equivalent plastic e_p in the Damage equation will be replaced with the History variable?)
4. According to Keyword Manual, the LCSDG parameter (e_f curve) can not be equal 0, which means that It has to be defined anyway. Also, the damage is accumulated depending on the ratio of plastic strain to failure strain defined by LCSDG. But in ANSYS workbench I don't see this parameter in the MAT_ADD_GISSMO material model. I can only define ECRIT or DCRIT which are not the criteria for material failure (as I understand). How do LS-Dyna calculate Damage in that case if no e_f (LCSDG) is defined?
5. Do I really need all these parameters or I can just use DTYP=0 and define critical damage inside SECTION_SOLID_SPG card as FS? In that case material failure will occur? I am asking because in Keyword Manual DTYP=0 denoted as "no failure" option. 

Thank you in advance!

How can one fringe the radiative flux coming from a *BOUNDARY_RADIATION_SET?

How can one fringe the radiative flux coming from a *BOUNDARY_RADIATION_SET?

Is there a way to change *ELEMENT_SOLID to *ELEMENT_TSHELL using LS-PrePost? I'd like to pick all elements in a part and make the change.

Within LS-PrePost, whenever I animate results, the fringe results do not update continuously while the animation is running. Stopping the animation at any time step and reselecting the desired fringe result will display it, but restarting the animation again erases the fringe plot and the animation resumes without any fringe data presented.

Is there a setting within LSPP to display fringe results during animations?

Is this supported? If so, is it limited to a simple, smart, and/or full restarts?

I have 4 layers of TSHELLS. They are bonded using *TIED_SURFACE_TO_SURFACE_OFFSET.

Duing deformation the layers are coming apart. I am not using a tiebreak contact so I expected them to stay bonded for all time.

I also have *ERODING_SINGLE_SURFACE defined on these layers since I want elements to be deleted. Are these two contact defintions conflicting? If so, how can I tie the layers and also have them erode?

I'm using LS-Dyna in Workbench. I want to find the area-weighted average maximum principal logarithmic strain but I can't see the option for any form of strain in the results tab of workbench.

Hello,everybody,

Default CSCM parameters did not account for kinematic hardening, according to its User Manual. That is to say, NH=1 and CH=0. Recently, I read the FHWA-HRT-05-063 Evaluation of LS-DYNA Concrete Material Model 159, and it says that by taking kinematic hardening into consideration, pre-peak nonlinearity of concrete stress-strain can be achieved, as shown in the fig.1 below. But the Evaluation did not provide specific procedure for determining the two parameters NH and CH, it only says that 0.7Keyword file of the single element simulation

Thanks for your attention.

Hello i'm a master student developing user material. 

i'm wondering that how can i define user- derfined viscosity in mat_sph_viscous subroutine in package.. 

1) Is it possible to link my umat41v with subroutine f3dm9sph_userdefin? 

    I want to define the material that is solid when elastic and fluid when after yielding 

2) In subroutine f3dm9sph_userdefin, is the xmu is the variable to define?? 

     i can't understand that there's no example in the package... 

I really appreciate your help...

please help me

Does anyone know of any methods to decrease model run time when using an ALE mesh? I am modelling a fluid-structure interaction problem and am facing very high run times for a relatively simple model. The model consists of a rigid wave maker, water composed of ALE NULL material, air composed of ALE VACUUM material, and a steel column modeled with shell elements and a PLASTIC_KINEMATIC material.

If I have the column set as a rigid material, the total model run time is 10 minutes, however as soon as I change it to a plastic_kinematic material the run time increases to 13.5 hours using just 800 shell elements to model the column.

Hello. Please guide me. Considering that to model Triple pendulum isolator with mat 197, we have to consider 3 beam elements with dimension 0. Is there an explanation for isolator modeling in the software? Or do you have an example that I can use?

In Explicit Dynamics, when determining the force components through the import option (Figure 1), which kind of forces can be imported as an XML file and applied to the geometry? (I mean variable with time or variable with coordinates). Is it possible to convert an Excel file containing force values in different coordinates (Figure 2) to XML and import it?

Since the SPG option was added to the Section object in the Workbench version of LS-Dyna is it possible somehow to display particles using the ANSYS interface?

I know about the LS-PrePost, but I want to implement whole my simulation using ANSYS Workbench. I made a simulation of a uniaxial stress test using SPG (Section -> SPG) but when I try to look at the results I see only finite elements (basic mesh).

Also, I want to know where the bonds between particles were broken (failure of the material). How can I do this?

Hello,

I'm modeling a tension specimen under displacement control by applying prescribed displacement to the node set, while from the output data, the motion of the node set is not moving as I prescribed. I'm using solid element -1. I wonder if anyone faced this kind of problem before? 

Thanks,

Min-Chun

Regarding the user defined material, in the manual *Module can be used now to include the USDMAT is the standard LS-Dyna runs.

• Is this use of *MODULE also compatible with MPP solver?
• Are there any examples and tutorials for this?

Thanks!

Hello forum,

I have seen and read many examples of ALE, but they all are FSI problems... I have two metals impacting at high velocities and want both materials to be ALE since both are deforming heavily i.e., I don't think Lagrange In Solid constraint is appropriate here. 

Can anyone help me setup an ALE simulation that accomplishes this?

Thanks,

Peter Yip