Skip to main content

Predictive Engineering LS-DYNA DEM and SPH Simulation Project Work

Large Rock hitting bed of gravel (DEM) within apron feeder (FEA) used in open-pit mining

Analysis

LS-DYNA

Objective

This case study presents several examples where we have used the discrete element method (DEM) and smooth particle hydrodynamics (SPH) to apply sand and rock, mineral, organic (bird strike) and fluid loading to complex nonlinear dynamic finite element models.

DEM and SPH are both visualized as small discrete spheres but that is about all they have in common since DEM is often used for modeling discrete particles such as rocks or pea pods while SPH is used for modeling continua such as fluids and solids. Where we have found DEM and SPH useful is as a method to apply dynamic loads to structures. For DEM simulations, the ability to simulate granular media from sand and rocks or to friable compressed mineral cake or to food products, has allowed us to create FEA simulations that are far more accurate than what can be achieved by any combination of time varying force, acceleration or pressure loading arrangement. With SPH and its ability to simulate the mechanical response of highly deformable media (e.g., hail or frozen birds) during impact or fluids sloshing within a tank with good accuracy and low numerical cost provides a ready means for performing bird strike analyses or hail impact analyses or fluid sloshing analyses.

This case study is provided as a standalone document but is best accompanied by the video we have posted on YouTube which provides an overview of the DEM and SPH process and some examples of how we have used it at Predictive Engineering.

 

Keywords: Femap, LS-DYNA, discrete element method (DEM), smooth particle hydrodynamics (SPH), finite element analysis, drop-test, bird strike analysis, hail impact analysis, DEM analysis of rock and sand, DEM calibration to experimental tests, finite element analysis, nonlinear analysis, FSI Analysis, DEM to FEA, ASCE 4-98, sloshing analysis of ASME Section VIII, Division 2 pressure vessel, off-shore platform mounted pressure vessels.

The video provides a graphical overview of the DEM and SPH process that has been used at Predictive Engineering with examples of project work with direct examples of:

  • Using DEM as an integral part of a simulation to predict the cushioning effect of sand and rocks (DEM particles) when a very large rock (rigid body) is dropped onto an apron feeder (FEA) that is commonly used in an open pit mining operation;
  • DEM impact simulation of dropped mineral cake onto conveyor;
  • Mineral flow prediction on conveyor with knife gate with prediction of maximum forces onto the knife gate and if the gate would get buried by conveyed material;
  • Virtual DEM angle-of-repose calibration to experimental test;
  • SPH simulation of bird strike on composite radome;
  • SPH fluid sloshing in ASME Section VIII, Division 2 pressure vessel.

 

LS-DYNA used in a combined structural / DEM model
LS-DYNA was used in a combined structural / DEM model for the simulation of a large rock-drop on an apron feeder (AF) commonly used within the mining industry. Results show that if the AF is keep filled with material, the impact of large rocks is almost completely mitigated.
LS-DYNA was used in a combined structural / DEM model for the simulation of a large rock-drop on an apron feeder (AF) commonly used within the mining industry.  Results show that if the AF is keep filled with material, the impact of large rocks is almost completely mitigated.
Femap FEA model of the apron feeder system
The Femap FEA model of the apron feeder system was constructed using a carefully mapped mesh of quad plate elements with beam elements for the chain and roller system. The DEM particles were automatically created within LS-PrePost.
The Femap FEA model of the apron feeder system was constructed using a carefully mapped mesh of quad plate elements with beam elements for the chain and roller system.  The DEM particles were automatically created within LS-PrePost.
DEM particles
DEM particles were used to simulate the processed mineral cake onto conveyer belt feeder with a knife gate at the far end. The model was built in Femap and then exported to LSPP for the addition of the DEM elements.
DEM particles were used to simulate the processed mineral cake onto conveyer belt feeder with a knife gate at the far end.  The model was built in Femap and then exported to LSPP for the addition of the DEM elements.
DEM particle impact loading on conveyor
DEM particle impact loading on conveyor
DEM angle of repose and surface friction test
DEM angle of repose and surface friction test (angle to induce flow) simulations
DEM angle of repose and surface friction test (angle to induce flow) simulations
Femap model of composite radome structure
Femap model of composite radome structure translated out to LSTC’s LS-PrePost Interface with SPH bird added to the simulation
Femap model of composite radome structure translated out to LSTC’s LS-PrePost Interface with SPH bird added to the simulation
The SPH bird disintegrates upon impact with the radome
The SPH bird disintegrates upon impact with the radome
Sloshing analysis
The sloshing analysis was performed to meet ship-board specifications per S930-AS-CAL-10007 with the work tied to ASCE 4-98. The pressure vessel was built in Femap and then prepared for SPH sloshing analysis using LSTC LS-PrePost.
The sloshing analysis was performed to meet ship-board specifications per S930-AS-CAL-10007 with the work tied to ASCE 4-98.  The pressure vessel was built in Femap and then prepared for SPH sloshing analysis using LSTC LS-PrePost.
Shell mesh of the pressure vessel
The shell mesh of the pressure vessel was used to generate the SPH particles within the pressure vessel. The EOS was for standard water. Sloshing was done by accelerating the vessel from the base of its skirt.
The shell mesh of the pressure vessel was used to generate the SPH particles within the pressure vessel.  The EOS was for standard water.  Sloshing was done by accelerating the vessel from the base of its skirt.
Hand-calculations using ASCE 4-98
Hand-calculations using ASCE 4-98 is the industry standard for sloshing analysis but the SPH method provides a full-field color simulation of the event with stress and base skirt reaction forces.
Hand-calculations using ASCE 4-98 is the industry standard for sloshing analysis but the SPH method provides a full-field color simulation of the event with stress and base skirt reaction forces.