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EDEM Contact Models
A Contact Model describes how elements behave when they come into contact with each other.
Base Contact Models
Base Contact models define the physical collision between particle materials or particles and geometries.
Hertz-Mindlin (no slip) Model
The Hertz-Mindlin (no slip) contact model is the default model used in EDEM due to its accurate and efficient force calculation.

Welcome
What's New
New features and enhancements available in EDEM.
Release Notes
This document contains information about the EDEM release, such as key features and enhancements, bug fixes, and known issues.
About EDEM
EDEM is a high-performance simulation software for bulk and granular materials.
Get Started with EDEM
The EDEM user interface comprises three icons for each simulation component - Creator, Simulator, and Analyst.
EDEM Creator
EDEM Creator is the pre-processor for creating an EDEM simulation model, including setting up equipment and defining the generation of bulk materials.
EDEM Simulator
EDEM Simulator is a powerful solver used for fast and efficient simulations.
EDEM Analyst
EDEM Analyst is the post-processor used to analyze and visualize the results of your simulation.
EDEM Contact Models
A Contact Model describes how elements behave when they come into contact with each other.
- Base Contact Models
  Base Contact models define the physical collision between particle materials or particles and geometries.
  - Hertz-Mindlin (no slip) Model
    The Hertz-Mindlin (no slip) contact model is the default model used in EDEM due to its accurate and efficient force calculation.
  - Hertz-Mindlin with JKR Model
    The Hertz-Mindlin with JKR contact model works within the contact zone and allows you to model strongly adhesive systems, such as dry powders or wet materials.
  - Hertz-Mindlin with JKR V2 Model
    The Hertz-Mindlin with JKR V2 model captures the behavior of multiple materials and uses a more accurate implementation of the JKR theory.
  - Hysteretic Spring Model
    The Hysteretic Spring contact model allows plastic deformation behaviors to be included in the contact mechanics equations, resulting in particles behaving in an elastic manner up to a predefined stress.
  - Linear Spring Model
    The damped Linear Spring contact model is based on the work by Cundall and Strack (Cundall and Strack 1979).
  - Edinburgh Elasto-Plastic Adhesion Model (EEPA)
    The Edinburgh Elasto-Plastic Adhesion Model (EEPA) contact model captures the history dependence and the key characteristic behavior of cohesive solids.
  - Hertz-Mindlin Nassauer-Kuna model
    The Hertz-Mindlin Nassauer-Kuna model is a modification of the Hertz-Mindlin model.
  - Volume Spring Model
    The Volume Spring contact model is an experimental model in which the normal force is proportional to the overlap volume of the two particles and does not involve the penetration depth.
- Rolling Friction Contact Models
  Rolling Friction is the resistive force that slows down the motion of a rolling object.
- Spinning Friction Contact Model
  The Spinning Friction contact model is used to account for the friction that would occur if a particle face is rotating against another particle or Geometry.
- Additional Contact Models
  You can also add Additional contact models to a simulation.
- Particle Body Force Contact Models
  You can define a particle body force to act on particles when a specified condition is met, when particles are in certain positions, or are traveling at a specified velocity.
- Plug-in Contact Models
  You can add Plug-in contact models to a simulation.
- Field Data Manager
  Field Data Manager allows you to import and manage field data for use in a Custom model (typically, a Particle Body Force).
- Contact Model and GPU Device Compatibility
  The Multi-Sphere solver can run on two different engines such as CPU and CUDA.
EDEM Cal Utility
EDEM Cal is a utility which works with EDEM and is designed to assist in performing calibration.
GPU CUDA Guide
The EDEM CUDA GPU module uses the latest General Purpose Computing on Graphical Processing Units (GPU) technology.
Programming Guide
The EDEM Programming Guide describes the EDEM API.
Coupling Interface Programming Guide
The Coupling Interface Programming Guide provides an overview of how to use the EDEM Coupling Interface to couple with a generic CFD code and/or Multi Body dynamics codes.
EDEMpy
EDEMpy is a Python library for accessing EDEM data from .h5 files (the underlying EDEM file format). EDEMpy does not require prior knowledge of advanced programming.
EDEM Solver Capabilities
EDEM contains four solver engines.
Appendix
This section provides additional information about how to estimate simulation time, supported EDEM File types, attribute definitions, and so on.
EDEM Terminology
Definitions of terms used in EDEM.
References and Bibliography
This section cites the contributions made by various authors and sources that have been used as reference material for EDEM, and the specifics of how they have been applied can be found in the individual contact model sections.

Hertz-Mindlin (no slip) Model

The Hertz-Mindlin (no slip) contact model is the default model used in EDEM due to its accurate and efficient force calculation.

In this model, the normal force component is based on the Hertzian contact theory (Hertz 1882). The Tangential Force model is based on the work of Mindlin-Deresiewicz (Mindlin 1949) (Mindlin and Deresiewicz 1953). Both normal and tangential forces have damping components, where the damping coefficient is related to the Coefficient of Restitution as described in (Tsuji, Tanaka and Ishida 1992). The tangential friction force follows the Coulomb law of Friction model, such as (Cundall and Strack 1979). The Rolling friction is implemented as the contact independent directional constant torque model, such as (Sakaguchi, Ozaki and Igarashi 1993).

In particular, the normal force, F_n, is a function of normal overlap δ_n defined as:

F_{n} = \frac{4}{3} E^{*} \sqrt{R^{*}} δ_{n}^{_{\frac{3}{2}}}

The equivalent Young’s Modulus E^* and the equivalent radius R^* are defined as:

\frac{1}{E^{*}} = \frac{(1 - v_{i}^{2})}{E_{i}} + \frac{(1 - v_{j}^{2})}{E_{j}}

\frac{1}{R} = \frac{1}{R_{i}} + \frac{1}{R_{j}}

With Eⁱ, vⁱ, Rⁱ, and E^j, v^j, R^j, being the Young’s Modulus, Poisson's ratio, and radius of each sphere in contact. Additionally, there is a damping force, F_n^d, defined as:

m^{*} = {(\frac{1}{m_{j}} + \frac{1}{m_{i}})}^{^{_{^{^{- 1}}}}}

Where m^* is the equivalent mass, v_n^rel is the normal component of the relative velocity, and β and S_n (the normal stiffness) defined as:

β = \frac{- \ln e}{\sqrt{\ln^{2} e + π^{2}}}

S_{n} = 2 E^{*} \sqrt{R^{*} δ_{n}}

With the Coefficient of Restitution e, the tangential force, F_t, depends on the tangential overlap δ_t and the tangential stiffness S_t.

F_{t} = - S_{t} δ_{t}

with

S_{t} = 8 G^{*} \sqrt{(R^{*} δ_{n})}

Here, G^* is the equivalent Shear modulus. Additionally, tangential damping is defined as:

F_{t}^{d} = - 2 \sqrt{\frac{5}{6}} β \sqrt{S_{t} m^{*}} v_{t}^{\begin{array}{l} \to \\ r e l \end{array}}

Where v_t^rel is the relative tangential velocity. The tangential force is limited by the Coulomb friction μ_sF_n, where μ_s is the Coefficient of Static Friction.