SPH and FEM coupling for Turning
Niranjan Manur Krishnamurthy
I'm still facing issues with constraining the nodes properly with the FE mesh. The nodes begin to scatter away from the FE mesh after some initial rotations. I have attached an image for reference.
I have used the 'Tied_nodes_to_Surface' contact for tying the nodes and do not find any errors of unconstrained nodes in the output file.
I also would like your suggestions on how to calculate the contact thickness SST and MST as I did not find any way except for the formula in the keyword manual I.
Many thanks in advance for your answers.
Regards,
Niranjan.
l...@schwer.net
1\ It has been recommended to set the Contact parameter SST to half of the initial smoothing length.
2\ In my experience, a minimum of 9 SPH particles, 3x3, need to be in initial contact with each face of a Lagrange solid.
3\ Since you have so many SPH particles already, have you considered making the core SPH particles as well?
4\ You may try other kernel forms.
5\ At some rotational speed, the inherent tensile instability of SPH with cause particles to fly away – not sure what that rotation speed would be.
5\ Have you checked the papers at www.dynalook.com for similar rotating cutting simulations using SPH?
--len
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James Kennedy
Dear Niranjan,
See if these presentations are of some interest,
The *DEFINE_ADAPTIVE_SOLID_TO_SPH/DES keyword provides a simulation technique considering the effect of the debris since the failed solid elements are replaced with the particles. In this presentation, the results obtained using different options in *DEFINE_ADAPTIVE_SOLID_TO_SPH/DES were compared and the possibility to use this capability for real problems on concrete structures (*MAT_072R3) was discussed:
Tokura, S., and Niwa, K., "Evaluation of Debris Modeling Technique on Failure Simulation of Concrete Structures", 11th European LS-DYNA Users Conference, Salzburg, Austria, May, 2017.
http://www.dynalook.com/11th-european-ls-dyna-conference/concrete-penetration/
Recent LS-DYNA enhancements to air blast loadings:
Schwer, L.E., "New Keywords Related to Blast and Penetrations: A Few Simple Applications", 11th German LS-DYNA Forum, Ulm, Germany, October, 2012.
https://www.dynamore.de/de/download/papers/ls-dyna-forum-2012/documents/multiphysics-2-2
Some further information regarding your issues.
This inheriting of history variables would only apply to ICPL=1,IOPT=1 found on the keyword *ADAPTIVE_SOLID_TO_SPH entry. In this case, the failed solid turns to SPH and remains
coupled to remaining solids.
The converted SPH particles will couple only with the solid element that give birth to those particles. In this option, when solid elements are converted into SPH particles, the user can either
define the new material model (such as no failure or stronger failure criteria to ensure no further failure happens) or keep the same material model.
With this treatment the SPH particles are visible from the onset of the simulation. These embedded particles remain inactive and do not participate in contact until the parent
solid element is eroded. Generally, contact with the solid elements is treated using one contact definition, while a second contact definition, typically, *CONTACT_AUTOMATIC_NODES_TO _SURFACE, is used to handle contact with the converted SPH particles. In
the second definition, the slave side is made up of the SPH particles identified with SSTYP=3 in *CONTACT which references IPSPH defined in *DEFINE_ADAPTIVE_SOLID_TO_SPH.
I suggest you overlay time histories of stress for a solid element and the associated SPH particle(s) that take over after the solid fails. Also suggest using a high resolution
output from elout for this purpose using *DATABASE_ELOUT, *DATABASE_HISTORY_SOLID, and *DATABASE_HISTORY_SPH. You will also need to write sphout (*DATABASE_SPHOUT), too, since elout does not have the SPH data.
This will give you the elout and sphout data which shows that the SPH particles indeed take their history variables from the host solid.
Attached (to your personal email) you will find an example wherein the SPH part has been given a different material ID to allow one to make the failure strain much larger than the failure strain of the host solid part.
R10 and later includes *MAT_ADD_EROSION criteria in SPH failure and that necessitates that different part IDs without the failure criterion be used for the adapted solid-to-SPH parts when ICPL=1,IOPT=1.
Sincerely,
James M. Kennedy
KBS2 Inc.
January 29, 2023
From: ls-d...@googlegroups.com [mailto:ls-d...@googlegroups.com]
On Behalf Of Niranjan Manur Krishnamurthy
Sent: Sunday, January 29, 2023 5:21 AM
To: LS-DYNA2 <ls-d...@googlegroups.com>
Subject: [LS-DYNA2] SPH and FEM coupling for Turning
Dear all,
--
James Kennedy
Deart Niranjan,
Perhaps of interest?
Dmitriev, A.1., Lalin, V.1, Novozhilov, Y., and Mikhalyuk, D., “Simulation of Concrete Plate Perforation
by Coupled Finite Element and Smooth Particle Hydrodynamics Methods”, Construction of Unique Buildings
and Structures, Vol. 92, Article No. 9207, 2020.
https://unistroy.spbstu.ru/userfiles/files/2020/7(92)/9207(1).pdf
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