Blast simulation
오상헌 | 응용역학 및 재료전공 | 한양대(서울)
Hello!
I am currently modeling an experiment where a blast load is applied to a reinforced concrete column.
For the blast modeling approach, I have adopted a coupled method that combines the Load Blast Enhanced (LBE) technique with the Multi-Material Arbitrary Lagrangian-Eulerian (MM-ALE) method.
To obtain the pressure values observed in the experiment through the simulation, which keywords should be used in LS-DYNA?
Additionally, I have noticed that when adjusting the TSSFAC parameter under the *CONTROL_TIMESTEP keyword, the blast pressure and the displacement of the reinforced concrete column increase. What is the reason for this behavior, and how can an appropriate value of TSSFAC be determined?
Lastly, the simulated blast pressure seems to vary depending on the volume of the air domain. What methods can be used to determine a suitable air domain volume in the MM-ALE region?
Thank you very much for your time and support.
l...@schwer.net
1\ To obtain pressure histories at specific positions use *DATABASE_TRACER.
2\ Unlike the Lagrange solver, the Eulerian solver does not have an analytical stable time step minimum. The rule of thumb, when modeling explosives with the Eulerian solver, is to use a TSSFAC=0.6 as a starting value. The user then needs to determine if this TSSFAC is satisfactory by performing additional simulations with smaller values of TSSFAC. The hope is differences in key simulation metrics will converge, but this is not guaranteed.
3\ The outer boundary of an Eulerian simulation will always act as reflecting surface for blast waves. The user needs to select a boundary sufficiently distant from the region of interest to assure these boundary reflected waves to do interfere with the region of interest.
--len
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James Kennedy
Dear Sang Heon,
Several presentations which may be of interest:
In this brief look at (LOAD_BLAST_ENHANCED) and Multi-Material ALE coupling, the
LS-DYNA required keywords are explained and some of the key parameters are investigated
using a simple example .Based on these simple examples some recommendations for LBE and
MM-ALE coupling are provided.
Schwer, L., “A Brief Introduction to Coupling Load Blast Enhanced with Multi-Material ALE”
The Best of Both World for Air Blast Simulation”, 9th German LS-DYNA Forum, Bamberg,
Germany, October, 2010.
https://www.dynamore.ch/en/downloads/papers/10-forum/papers/J-I-01.pdf
The *CONSTRAINED_LAGRANGE_IN_SOLID keycard is used to couple the air domain
(Master) to the plate (Slave). Since Lagrangian slave side of this mode comprised of solids
which may be eroded (concrete) due to material failure criteria, CTYPE was set to 5. An
appropriate degree of refinement of the ALE mesh is partially dictated by the geometric
characteristics of the Lagrangian parts. A reasonable goal is to have the ALE elements be
nearly the same size as the Lagrangian elements where coupling is to take place.
Tabatabaei, Z.S., and Volz, J.S., "A Comparison Between Three Different Blast Methods
in LS-DYNA: LBE, MM-ALE, Coupling of LBE and MM-ALE", 12th International LSDYNA
Users Conference, Dearborn , Michigan, June, 2012.
https://www.dynalook.com/conferences/12th-international-ls-dyna-conference/blast-impact20-d.pdf
Shuaib, M., and Daoud, O.M.A., “Numerical Analysis of RC Slab under Blast Loads using the
Coupling of LBE and ALE Method in ;S-DYNA”,
The coupling of LOAD_BLAST_ENHANCED (LBE) keyword and multi material arbitrary
Lagrangian Eulerian (MM-ALE) method is a recently developed numerical blast application
method. Compared to other blast application methods, its use was argued to be useful. This paper
aims to evaluate the application of this newly developed numerical blast simulation method for
estimating the deformations occurred in reinforced concrete (RC) slabs due to blast loads. For
evaluation, a previously conducted experiment for RC slab under close-in detonation was modelled
and analysed using LS-DYNA software, and the coupling approach was applied. The KCC concrete
constitutive model was selected for concrete modelling. Pressure-time histories have been compared
with curves obtained using the empirical methods. Then, the calculated values of the deformations
(deflections and damage modes) from the analysis were validated against experimental results. From
the analysis, obtained blast pressure results have shown lower peak reflected pressure values compared
to those from CONWEP application. As for RC deflection, the pattern of deflection tended to follow
that in the actual experiment with considerable variation. Furthermore, damage modes found from
analysis appeared to be overestimated, as high strain fringe values were found extensively in the slab.
It was concluded that further investigations for the applicability of the coupling method for estimating
RC slabs deformations are required.
Sincerely,
James M. Kennedy
KBS2 Inc.
May 20, 2025
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Subject: [LS-DYNA2] Blast simulation
Hello!
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