Diapositiva 1 - ESSS

NUMERICAL COUPLING BETWEEN DEM
(DISCRETE ELEMENT METHOD) AND FEA
(FINITE ELEMENTS ANALYSIS).
Daniel Schiochet Nasato - ESSS
Prof. Dr. José Roberto Nunhez – Unicamp
Dr. Nicolas Spogis - ESSS
Fabiano Nunes Diesel - ESSS

Agenda
• Objectives
• DEM Method
• EDEM ANSYS Coupling
• Validation and real case
• Conclusions

Objectives
• Develop an 1-way coupling between
Discrete Element Method (DEM) and
Finite Element Method (FEM).
• Propose a numerical validation to evaluate
the method accuracy.
• Simulate a transfer chute using the
developed method to solve a real problem.

DEM Method
• Governing equations for the translational and rotational
motion of particle i with mass m i and moment of inertia I i :
• v i and ω i are the translational and angular velocities of particle i,
• F c ij and M ij are the contact force and torque acting on particle i by particle j
or walls,
• F nc ik is the noncontact force acting on particle i by particle k or other
sources,
• F f i is the particle–fluid interaction force on particle i,
• F g i is the gravitational force.

DEM Contact Detection
• To detect contacts between particles and structure, EDEM splits the
geometry in triangular surface mesh (StL file format), a 3-dimensional
surface geometry;
• The surface is tessellated or broken down logically into a series of
small triangles (facets);
• Each facet is described by a perpendicular direction and three points
representing the vertices (corners) of the triangle.

EDEM-ANSYS Coupling
• EDEM was used as Discrete Element Method (DEM) tool and ANSYS
was used as Finite Element Method (FEM) tool.

EDEM-ANSYS 1-way coupling
Setup ANSYS Model
Run EDEM Model
Create Named
Surface
Export EDEM
Loads
Interpolate Loads
Python Script
And ANSYS APDL
Solve and Evaluate
ANSYS Results

EDEM-ANSYS coupling methods
Developed
• 1-Way DEM-FEA
– Coupling - Steady State
– Static Structural Analysis
• 1-Way DEM-FEA
– Coupling - Transient
– Transient Structural Analysis
Under development
• 2-Way DEM-FEA
– Coupling - Transient
Force
Displacement

Interpolation Method
• Load is transferred from EDEM to ANSYS using a conservative
interpolation;
• Each element face is divided into n number of IP faces, where n is the
number of nodes on the face;
• IP faces are converted onto a two-dimensional polygon;
• Polygons on the sending side are intersected with the IP polygons on
the receiving side;
• The polygon intersection creates many overlapped areas used to
transfer loads between the two sides.

Interpolation Method
• During interpolation, the total force balance over the surface is
preserved.
• For loss less data transfer between particle and structural code, both
numerical models must be coincident in space

Validation Tests
• It was built a small box with 1x1x1m in EDEM and it was created 2000
particles with 40mm diameter and 2500kg/m 3 density;
• It was performed 3s of simulation to ensure that particles have no
velocity in Y direction;
• Total forces (X, Y and Z) and surface mesh nodes position are
exported from EDEM in a single time step.
• Force on Y direction calculated on EDEM was compared with
analytical results.

Validation Tests
• Test 1 - ANSYS coarse mesh,
EDEM coarse mesh
• Test 2 - ANSYS intermediate mesh,
EDEM coarse mesh
• Test 3 - ANSYS refined mesh,
EDEM coarse mesh
Analytical EDEM force Test 1 - Coarse Test 2 - Intermediate Test 3 - Refined
Force Y (N) 1643,8 1645,8 1575,2 1617,6 1663,5
Error % 0,1 4,3 1,7 1,1

Industrial Application
•Geometry directly imported
from CAD on ACIS (.sat)
format.
•Simulation:
•Conveyor belt
•Transfer chute
•Vibrating screens
•Dynamics:
•Sinusoidal translation
•Sinusoidal rotation
•Moving plane (for belt)

EDEM Results

Screen force distribution
High impact velocities zones
(up to 7 m/s) on screen.
Wear and structural problems.
High forces on chute discharge.

EDEM-ANSYS coupling
The developed scripts and macros automatically interpolates EDEM forces
(normal and tangential) on the structural elements.

Static Structural Analysis
Total Deformation
Equivalent Strain
The Static Analysis performed shows stresses &
Strains under the yield limit OK

Conclusions
• EDEM ANSYS Coupling showed good results;
• For numerical validation error was smaller than 5%;
• EDEM ANSYS Coupling showed great potential to
be used as a commercial tool.
– Interpolation takes a few minutes to be done for big
simulations cases.