SPH model
ANIKET KUMAR
l...@schwer.net
Not enough information has been provided to offer an opinion.
Perhaps an image of the deformed model and description of where and what boundary conditions are applied would help.
--len
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James Kennedy
Dear Aniket,
Perhaps of some help:
Lagrangian, Eulerian and Smooth Particle Hydrodynamics (SPH) formulations were applied to the simulation of a rigid fragment impacting a concrete panel. The concrete was modeled using a two surface plasticity model, where the shear failure surface and pressure-volume strain (compaction) surface are independent; this is sometimes referred to as a ‘flat cap’ mode which is given as *MAT_016 in LS-DYNA:
Schwer, L.E., "Preliminary Assessment of Non-Lagrangian Methods for Penetration Simulation", 8th International LS-DYNA Users Conference, Dearborn, Michigan, May, 2004.
http://www.dynalook.com/international-conf-2004/08-1.pdf
In this paper, SPH simulations for the local damage of the concrete plate due to high velocity impacts were performed to study the effects of impact velocity and the strength of the concrete plate. To represent the nonlinear behavior of concrete, *MAT_PSEUDO_ TENSOR (*MAT_016) was used as a constitutive model in LS-DYNA; strain rate effects of concrete were also taken into account:
Sakakibara, T., Tsuda, T., and Ohtagaki, R., "SPH Formulations of High Velocity impact on Concrete Plate", 7th European LS-DYNA Use's Conference, Salzburg, Austria, May, 2009.
https://www.dynalook.com/european-conf-2009/M-I-03.pdf
Erosion criteria are typically only used with Lagrange solid elements. They cannot be used with Eulerian techniques as there is no concept of cell (element) removal in the Eulerian framework. Similarly, erosion criteria are not typically associated with particle methods, such as SPH and Element Free Galerkin (EFG). These particle methods were specifically designed to handle large deformation without the problems of mesh distortion that plague Lagrangian solid elements, and hence there is no need to erode particles. However, in this work consideration will be given to including erosion (stresses set to zero) in the SPH model comparisons:
Schwer, L.E., "An Aluminum Plate Perforation: A Comparative Case Study Using Lagrange with Erosion, Multi-Material ALE, and Smooth Particle Hydrodynamics", 7th European LS-DYNA User's Conference, Salzburg, Austria, May, 2009.
http://www.dynamore.de/en/downloads/papers/09-conference/papers/J-I-01.pdf
In both the simulations and experiments it was shown that the geometry and material of the projectile has strong influence on the penetration depth, spalling shape and energy levels. The simulations were made in LS-DYNA using a meshfree solver (SPH). The concrete was modeled with the *MAT_159 (Continuous Surface Cap Model) concrete model and the projectiles were modeled by a rigid model and a Johnson-Cook with damage material model:
Sedlak, M., "Comparative Study of Fragment Geometries", Master’s Thesis, Solid Mechanics, KTH Engineering Sciences, Stockholm, Sweden, 2012.
http://www.diva-portal.org/smash/get/diva2:561774/FULLTEXT01.pdf
The paper considered the failure study of concrete structures loaded by the pressure wave due to detonation of an explosive material. In the paper two numerical methods were used and their efficiency and accuracy were compared. They were the Smoothed Particle Hydrodynamics (SPH) and the Finite Element Method (FEM). The *LOAD_BLAST option (CONWEP) was used to apply pressure loads due to explosion. *MAT_159 (data included) was used to represent the concrete structures (concrete B30):
Jankowiak, T., and Lodygowski, T., "Smoothed Particle Hydrodynamics versus Finite Element for Blast Impact", Bulletin of the Polish Academy of Sciences: Technical Sciences, Vol. 61, No, 1, pp. 111-121, March, 2013.
http://yadda.icm.edu.pl/yadda/element/bwmeta1.element.baztech-article-BPG8-0098-0016/c/Jankowiak.pdf
In this manuscript, four solution strategies for air blast loading of structures were presented. The techniques were: Load Blast Enhanced (LBE), Multi-Material Arbitrary Lagrange Eulerian (MMALE), Particle Blast (PB), and Smooth Particle Hydrodynamics (SPH). The first is an engineering model requiring minimal input and with minimal CPU requirements. The latter three are so called ‘first principal’ models requiring fairly extensive user input, e.g. equations of state for the explosive and air. The computing resources required by these techniques were substantial:
Schwer, L., Teng, H., and Souli, M., "LS-DYNA Air Blast Techniques: Comparisons with Experiments for Close-In Charges", 10th European LS-DYNA Users Conference, Wurzburg, Germany, May, 2015.
A model of a cylinder with a diameter and height of 400 mm was constructed in LS-DYNA using SPH particles to investigate the unconfined, quasi-static behavior of three concrete material models (i.e., *MAT_016, *MAT_072R3, and *MAT_159) in axial compression. Models were also prepared using Lagrangian solid elements and analyzed in axial compression to generate benchmark stress-strain data. Mesh refinement studies were conducted for the SPH cylinder to investigate the effects of particle spacing on predictions of elastic modulus and peak average axial stress. Analysis of the Lagrangian model showed post-peak softening for *MAT_072R3 and *MAT_159 and non-softening (i.e., perfectly plastic) behavior for *MAT_016. The SPH cylinder reasonably recovered the elastic modulus and peak average axial stress of the Lagrangian cylinder for all three material models, but the post-peak behavior predicted using the Lagrangian cylinder was not recovered using the SPH cylinder for *MAT_072R3 and *MAT_016:
Terranova, B., Whittaker, A., and Schwer, L., "Benchmarking Concrete Material Models using the SPH Formulation in LS-DYNA", 15th International LS-DYNA Users Conference, Dearborn, Michigan, June, 2018.
Sincerely,
James M. Kennedy
KBS2 Inc.
March 5, 2024
From: ls-d...@googlegroups.com [mailto:ls-d...@googlegroups.com]
On Behalf Of ANIKET KUMAR
Sent: Tuesday, March 05, 2024 5:45 AM
To: LS-DYNA2 <ls-d...@googlegroups.com>
Subject: [LS-DYNA2] SPH model
Hello, I am using the SPH method to simulate a quarter model of RC slab. According to journal paper the top and bottom portion of slab are damaged due to blast loading. But in my model, only show the crater damage on top of the slab and the bottom portion of the slab is unaffected.. Why ??
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