CONNECTION PROBLEM
Kağan GENÇ
Kind wishes,
l...@schwer.net
Hello Kagan –
I am not sure I understand your mesh. Are you just showing the detonation products? The Eulerian mesh should cover the Lagrange mesh and not terminate at the common surface between Eulerian and Lagrange meshes.
--len
From: ls-d...@googlegroups.com <ls-d...@googlegroups.com> On Behalf Of Kagan GENÇ
Sent: Monday, March 7, 2022 11:51 PM
To: LS-DYNA2 <ls-d...@googlegroups.com>
Subject: [LS-DYNA2] CONNECTION PROBLEM
Hi Leonard and Kennedy,
I have been modeling a RC concrete slab subjected to blast loading so that I am using MM-ALE elements to model air and explosive. At first I modeled this by coarse meshes then by finer meshes. In this case, I do not expect the fluid(air) elements go through the slab, espcially, at the boundaries which enabled me to model 1/8 of the setup. For the coarse mesh used test, I have never seen fluid particles that go through the slab. However, for the finer mesh one, I have observed that the fluid particles directly go through the slab even if I use the same values and the same keyword for the connection namely, CONSTRAINED_LAGRANGE_IN_SOLID.
Coarse Mesh Test
Finer Mesh Test
These two images given above belongs to the same time of the explosion. While the model with coarse meshes is able to resist the force, the model with finer meshes is not able resist force and let fluid go through the slab interestingly. The keyword I used for the connection between lagrange and ALE elements is given below.
Any help would be appreciated.
Kind wishes,
GENC OGUZ KAGAN
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James M. Kennedy
Dear Kagan,
---------------------------------------
Please check your coupling input (nquad and mcoup)?
From the following link:
https://ftp.lstc.com/anonymous/outgoing/jday/jim_ALE_for_MGD_18oct2010.pdf
The parameter NQUAD determines the number of coupling points distributed
over each Lagrangian slave segment. If NQUAD=2 (default), then there are
2x2 = 4 coupling points on each Lagrangian slave segment. The coupling
algorithm looks for penetration of any ALE material meeting the conditions
of MASTER, MSTYP, and MCOUP across each of the coupling points. If
penetration at a coupling point is found, coupling forces are applied to count-
eract penetration. The larger the value of NQUAD, the more expensive the
coupling and the more likely the coupling forces will be excessive. If the
Lagrangian slave segments are approximately the same size as or smaller
than the Eulerian/ALE element faces, NQUAD=2 will generally suffice. If
the Lagrangian slave segments are coarser/larger than the ALE element faces,
NQUAD may need to be raised to 3 or higher to provide proper coupling.
The parameter MCOUP defines the AMMG(s) to which the Lagrangian slave
side is coupled. In cases where one AMMG dominates the forces imparted to the
Lagrangian structure and the forces from any other AMMGs can be neglected,
MCOUP should be set to 1. This might be the case where the density of one
AMMG is far greater than the density of the other AMMGs. In cases where the
effects of two or more AMMGs need to be considered in the coupling, MCOUP
can be set to a negative number. In this case, |MCOUP| identifies a set of one or
more AMMGs to be considered in the coupling. That set is defined using the
command *SET_MULTIMATERIAL_GROUP_LIST.
---------------------------------------
Below is a example with a rigid column being impacted by air and water. Taken from
following dynaexample:
https://www.dynaexamples.com/ale/intermediate-example
*ALE_MULTI-MATERIAL_GROUP
$# sid idtype
1 1 Air
2 1 Water
*SET_MULTI-MATERIAL_GROUP_LIST
$# ammsid
101
$# ammgid1
1
*SET_MULTI-MATERIAL_GROUP_LIST
$# ammsid
102
$# ammgid1
2
*CONSTRAINED_LAGRANGE_IN_SOLID_TITLE
1 Column-to-Air
$# slave master sstyp mstyp nquad ctype direc mcoup
4 1 1 1 4 4 2 -102
$# start end pfac fric frcmin norm normtyp damp
0.0 1.0000E20 0.1 0.0 0.5 0 0 0.0
$# k hmin hmax ileak pleak lcidpor nvent iblock
0.0 0.0 0.0 0 0.1 0 0 0
$# boxid ipenchk intforc ialesof lagmul pfacmm thkf
0 0 0 0 0.0 0 0.0
*CONSTRAINED_LAGRANGE_IN_SOLID_TITLE
2 Column-to-Water
$# slave master sstyp mstyp nquad ctype direc mcoup
4 2 1 1 4 4 2 -102
$# start end pfac fric frcmin norm normtyp damp
0.0 1.0000E20 0.1 0.0 0.5 0 0 0.0
$# k hmin hmax ileak pleak lcidpor nvent iblock
0.0 0.0 0.0 0 0.1 0 0 0
$# boxid ipenchk intforc ialesof lagmul pfacmm thkf
0 0 0 0 0.0 0 0.0
Sincerely,
James M. Kennedy
KBS2 Inc.
March 8, 2022
From: ls-d...@googlegroups.com [mailto:ls-d...@googlegroups.com] On Behalf Of Kagan GENÇ
Sent: Tuesday, March 08, 2022 1:51 AM
To: LS-DYNA2 <ls-d...@googlegroups.com>
Subject: [LS-DYNA2] CONNECTION PROBLEM
Hi Leonard and Kennedy,
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