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Explicit Dynamics - Insertion of the needle. Stresses in the needle

Hi. I am doing a simple needle insertion simulation in Explicit Dynamics software. I have tissue and needle - both linear material (tissue has a failure). The needle has an assigned velocity (I also tried with displacement), the tissue is fixed at the bottom. In the first step I insert the needle, in the second step I pull it out. After pull out, there is still stress in the needle (similar or the same as at the end of the insertion). Why are there the stresses after the needle is pulled out?
The analysis is without mass scaling (I also tried with scaling). I have tested different default settings (Low and high speed, quasi static, drop test), different needle velocities and there are always stresses in the needle at the end of the analysis.

Boundary conditions


Insertion and pull-out. von Mises stress map

Chart of maximum needle von Mises stress

All of a sudden, post processing in not working anymore. After normal termination and opening the file, the file open like this. When I go to Post and click Anim, it doesn't do anything. Any idea what is going on?

Getting zero stresses in autodyn on line body structure

Hi 

I am trying to use MPP Dyna, I wonder if there is any tutorials that can help me.

I am looking forward to hearing from you soon

Best Regards
Hamid

Dear all,

I am currently examine the impact of a ball (steel) with the human hand (I use the hand of the THUMS model). I want to investigate what contact forces and pressures occure when the ball is impacting the human hand. Now I am a little bit confused how to interpret the output of the simulation. The human hand consists of multiple layers: spon bone (solid), cortical bone (shell), tissue (shell), flesh (solid) and skin (shell). All layers have different material properties. I also defined AUTOMATIC_SURFCAE_TO_SURFACE contacts between some of the layers as well as between ball and skin. The goal is to investigate what effect an impact of an object with the back of the human hand has on contact pressure und contact force. 

1. Reading the Ouput RCFORC: do I have to add all forces at a particular time step to get the overall contact force?
2. Reading the Ouput INTFOR: the same as 1 - do I have to add the pressures given by FriComp or is it just the maximum of all contact surfaces? I am also not really sure what pressure output I have to take, segment or nodal? is the pressure over the segment calculated as the average of the elements and the nodals is the peak pressure at the particular node?
3. What is the difference between RCFORC and the "resultant interface force" (nodal or segment) in INTFOR?
4. In order to get the correct results, should I define contact between all layers? Currently contact is defined only between the solids and the shells, but not between two shells

At the beginning, I just examined the ball skin contact, but I quickly realized that this is not sufficient. Here is a picture of the simulation (I refined the mesh):

Thanks in advance

Hello, I am using the latest student version of LS Dyna to try and incorporate curing in a simulation. When I was reading through the manual I saw several key cards that could prove very useful:
MAT_ADD_Chemical_Shrinkage
MAT_Orthotropic_Thermal_Curing
277: MAT_ADHESIVE_CURING_Viscoelastic
Out of the three listed here, only 277 was available in PrePost's keyword library. Are the other 2 not included in the student version? Or do the cards have to be applied manually by writing a card to include in the .k file?

I want to increase the temperature of specific regions of an ideal gas using S-ALE.  This can be achieved using *BOUNDARY_AMBIENT, though as it is a temperature boundary condition rather than a heat flux, it constrains the temperature of a region so does not allow for superposition/interaction with adjacent regions (whose temperature I will increase later in the analysis).

Is it possible to use the thermal solver and the *LOAD_HEAT_GENERATION card to affect the temperature of the S-ALE material?  In my attempts so far, the temperature of the ALE material (Misc/History var. #4) seems to be unaffected by the increase in nodal temperature (Misc/Temperature), suggesting that the load applied to the thermal material is not coupled to the ALE material. 

Hi everyone, 

I am attempting to model a layered GFRP structure with curved surfaces. I chose to use layers of thin shells tied together with the CONTACT_AUTOMATIC_ONE_WAY_SURFACE_TO_SURFACE_TIEBREAK cards.

I generated the geometry for each layer in a CAD package, exported it as STEP files, and then meshed each layer inside LS-PrePost. 

The current problem I am facing is that the due to the curvature of the structure, the shell layer offset is not exact. In this problem, I have set the layer offset at 0.64 mm, but the measured offset is between 0.63996 mm and 0.64005 mm. This fifth significant figure discrepancy is causing the tied contacts to fail prematurely with a number of initial penetration warnings from the LS-DYNA solver. 

Any advice on how to tackle this problem would be greatly appreciated. Including the possibility of using other contact cards that can do the same job.  

Command issue We send mail to you 

Hello Team,

I would like to apply the shock load of 3 cycles of 25G on the Battery. If any one is having any sample model which you have defined, could you please share here?

I am stucked doing this procedure in LS Dyna. Earlier I have done that in Optistruct. 

Thank you in advance.

Prasad

Hello,

I am pretty new with Ls-Dyna. I have a simulation working in two steps: a tube is plastically compressed, then it is compressed again but in another direction. The displacements of the compressing objects are defined with the function "Curve".

I would like first to simulate only the first compression, verify if it works, then simulate with the 2nd compression. Like this, I can avoid simulating the whole thing just to find out that there is a problem in the very first steps. It is a multiple hours simulation...

Is there an easy way to do that? A step-by-step simulation?

Thank you very much for reading me!

Nicolas

Evaluation road characteristics on accident rates

please can you help me to model laminated glass . i have a big problem for this simulation ''Simulation of laminated glass loaded by air blast waves'' . and thank you all 

Hi,

I have been getting out of range velocities at the nodes, despite the fact that the element velocity are well within range.

How to solve this error?

Thanking you

Pratik Ganorkar (pratik2116303@iitgoa.ac.in)

MTech, Mechanical Engineering

Indian Institute of Technology, Goa

Hi, I developed UMAT, compiled and run the solvers.

but there's no response in solver windows like below

So i tried the default UMAT file without my code and also there happens a problem

What's wrong with this??

Please help me. I appreciate your help

Thanks

I am trying to sum two curves together to get the correct mass flow rate to be used with AIRBAG_WANG_NEFSKE (lcmt). When running the simulation, the curve function works correctly (I am able to see the result from curveout), but there is no mass flow applied to the airbag. Is there a way to be able to use a curve function for lmct?

Thanks,

Kyle

Dear Ansys suppot team

How to apply a moment befor ls dyna analysis. as shown in below fig.

Can someone outline the steps to apply a moment to a deformable body in Workbench LS-DYNA without the use of command snippets? It seems it is not possible; you must make use of some rigid body connected to the deformable body and then use the Rigid Body Tools to apply a moment. Is this limitation correct?

In standalone LS-DYNA is the recommended approach to apply a moment to a deformable body to use *CONSTRAINED_INTERPOLATION as is described in this example?

Hi,

I am trying to automate my post process analysis since a have many different simulations going on. I want to understand what is exactly in d3plot? Or how LSPP treats them?

1. Do d3plot files contain derived output or only tensors? Using lasso-python library in python, I am only able do access stress and strain tensors... meaning I have to calculate Von Mises from the tensors at each elements for each state...
2. Is there a way to flag certain derived output in d3plot which I can access with lasso-python library? It looks like LSPP computes derived outputs from tensors in d3plot (insetad of only retrieving derived outpouts, it computes it)

How to you access the data you can fringe in LSPP via d3plot and wihtout using LSPP at all? Do I really have to calculate all derived outputs myself?

Thank You

Is there a way to get model size info (number of nodes, beams, solids, etc) written into lsrun.out or another human readable file without using LS-PrePost.

I'd like to see this information:

I see that LS-DYNA only writes to lsrun.out every time it writes a d3plot file or flushes I/O buffers.

Is there a way to make it output this information every N cycles instead, regardless if it is performing either of these operations?

I wanted to know if LS-DYNA program manager still exists, and, if so, where can I download it? Or is LS-Run now the primary way to run analyses through LS-DYNA?

Hi everyone, 

I need some help again please :)

I have performed an impact simulation with a bird defined as a water liquid impacting upon a stretched acrylic laminate. When viewing the directional deformation, these large jagged elements appear, how do i troubleshoot this issue?

can the Students version of LS-Dyna be Integratet in the Workbench environment? if yes how?

Hi,

I am trying to simulate crash impact conditions using GHBMC-50 Model, I have included the impact condition as seprate file. when I do included my boundary contion and run the simulation , I am getting an error messege, "the termination due to out-of-range forces and moment number of nodes having out-of-range". Please any advise to overcome this problem will be really appriciated 

I am looking forward to hearning from you soon

Best Regards

Hamid