Contact Models

Contact Models

接触模型

A contact model describes how elements behave when they come into contact with

each other. Using the Interaction pulldown menu and

+

pick- list, you can build a list

(stack) of contact models. The top element is applied first, then the next one down

and so on. Use the up and down buttons to move the contact model up and down the

list (check the sections below since some models need to be at the start or end of the

list). To remove an item, click the

x

button. Click the preferences button to configure

the selected model.

（接触模型描述了元 素间的接触行为。使用

Interaction

下拉列表和

按钮“

+

”来添加一系列接触模型。

EDEM

优先采用列表中的最前列的接触模型，优先

< br>级依次下移。用户可以使用

up

和

down

按钮来上下移动列表中接触模型的排列。点击

按钮< /p>

“

X

’’

来删除 列表中的模型。

点击

Configure

按钮来设置所选中接触模型的参数配置。

）

Every simulation must have at least one base particle-to-particle and one

particle-to-geometry contact model. EDEM is supplied with several integrated contact

models; you can also add your own custom plug-in contact models. Refer to the user

section of the DEM website and the

EDEM Programming Guide

for details.

（所有仿真

必须至少包含一个基础的 颗粒

-

颗粒和颗粒

-

< br>几何体接触模型。

EDEM

提供了几个可选的

D EM

用户网

站查询）

Hertz-Mindlin (no slip)

（

Hertz- Mindlin

无滑动接触模型）

Hertz-Mindlin (no slip)

is the default contact model.

（

E DEM

中默认的接触模型）

Interaction

相互作

用

Particle to Particle

Particle to Geometry

None

Last

Configurable Parameters

参数的设置

Position

Last

Record Relative Wear (On / Off)

The Relative Wear model is a way of identifying regions of

high impact (normal) and abrasive (tangential) wear on

the equipment within a simulation. It is calculated based

on the relative velocity and associated forces between the

bulk material and the equipment. This model provides the

user with additional data to indicate regions in which wear

is taking place. Whilst it provides quantitative values for

comparison between two or more design iterations, it does

not determine an explicit material removal rate.

相对磨损的记录 （开

/

关）

相对磨损是一种识别仿真中设备的高冲击

（法向）

和磨损

（切

向）

区域的方法。

这种方法是基于疏散物料与设备的相关力

和相对速度计算的。

这个接触模型提供用户额外的数据来表

征相对磨损发生的区域。

与此同时，

这种计算方法提供了两

次及两次以上的仿真设计数值 的对比，

但是并不能精确的计

Interaction

相互作

用

Configurable Parameters

参数的设置

Position

算材料的损失率。

Note: The Relative Wear model does not take into account the size of each element

so a large variation in mesh sizing might produce unexpected or confusing results.

注意：

相对磨损模型不计每个单元的尺寸大小，因此网格尺寸如果变化 很大可能会产生

不可知和不可控的结果。

Hertz-Mindlin (no slip) with RVD Rolling Friction

Hertz-Mindlin (no slip)

with RVD Rolling Friction calculates contact forces in the same

way as the Hertz-Mindlin (no slip) model, but offers an alternative implementation of

rolling frictions at contacts. Since this model includes Hertz-Mindlin, remove the

default no-slip contact model from the list.

Hertz-Mindlin(

无滑动

)

滚动摩擦模型

该接触模型计算接触力的方式与赫兹

-

梅德 灵无滑动模型一样

,

但是在接触中它另外运用

< br>了滚动摩擦力。既然该模型包括赫兹

-

梅德灵模型，在接 触列表中就需要移除默认

的

Hertz-Mindlin(

无滑动

)

接触模型。

Interaction

Particle to Particle

Particle to Geometry

Configurable Parameters

None

Position

Last

Last

Record Relative Wear (On / Off), see Hertz-Mindlin

Hertz-Mindlin with Archard Wear

艾查德（

Archard

）磨 损

-

赫兹

-

梅 德灵接触模型

Hertz-Mindlin with Archard Wear

model provides the user with an explicit

measurement of material removed from exposed equipment faces due to

sliding/abrasive wear during a bulk materials handling process. It is based on the

determination of a

calibration constant

that can be defined through the appropriate

material testing.

该接触模型可以提供用户精确的测量在

散装物料搬运与输送过程中产生的设备材料损

耗。该模型的计算是基于材料物理实验的校准常数的测定。

Interaction

Particle to Geometry

Configurable Parameters

Position

Last

Assign a Wear Constant value for each geometry section.

Record Relative Wear (On / Off), see Hertz-Mindlin

Hertz-Mindlin with Heat Conduction

Hertz-Mindlin with Heat Conduction

calculates the heat flux between particles in

contact. The model calculates a heat flux based on the particle temperatures and their

overlap. This model must be used with Update Temperature particle body force to

complete the calculation. The Update Temperature particle body force allows the

inclusion of an external heat source and is where each particle temperature is

calculated based on the heat flux calculated in the contact model and a given external

heat flux.

Make sure the Update Temperature particle body force model is added to the particle

body force model. Since this model includes Hertz-Mindlin, remove the default no-slip

contact model from the list.

Interaction

Particle to Particle

Configurable Parameters

Set the thermal conductivity for each type of particle.

Note the unit depends on the temperature unit; for example, the

unit will be W/mK when the temperature unit is kelvin

.

Position

Last

Hertz-Mindlin with Bonding

（

Hertz- Mindlin

粘结模型）

Hertz-Mindlin with Bonding

bonds particles together. Since this model includes

Hertz-Mindlin, you should remove the default no-slip contact model from the list.

To use, enable the bonding model for both particle-particle and particle-geometry

interactions. Although particles cannot be bonded to geometry elements, the bonded

model ensures that the particles contact the geometry based on the particle’s physical

radius and not the contact radius.

Interaction

Particle to

Particle

(also enable

for Particle to

Geometry)

Configurable Parameters

Select an active bond then set the Bond Formation Time and

the following parameters:

?

Normal Stiffness

: the tensile/compressive stiffness along the

bond’s principal axis

（法向刚度）

?

Shear Stiffness

: Shear stiffness in the orthogonal plane to the

bond’s

principal axis

（切向刚度）

?

Critical Normal Stress

: the maximum normal stress the bond

can withstand before it fails

（法向临界应力）

?

Critical Shear Stress

: The maximum tangential stress the

bond can withstand before it fails

（切向临界应力）

?

Bonded Disk Radius

: The radius of the cylindrical bond

between the particles

（粘结圆面半径）

Set the bond stress and stiffness values to represent the

material that is been modeled. A high stiffness value will

produce high bond forces and stresses.

A lower than normal

timestep may be required to accurately capture these high

forces.

When the Bond Formation Time is reached, all defined particles

Position

Last

Interaction

Configurable Parameters

in contact will be bonded together.

Before this time, particles

interact based on the Hertz-Mindlin contact model.

The bond formation time can be updated to restart the bonding

process. Existing bonds won't be affected, but any unbonded

particles in contact will be bonded whenever the updated bond

formation time is reached.

Note that a bond between two particles will cease to exist

whenever one or both of the bonded particles leaves the

simulation domain.

If periodic boundaries are applied when

the particle leaves the domain, then the particle will exist on the

opposite side of the domain; in this case the two particles will

remain bonded across the periodic boundary.

Position

Particle to Geometry

Record Relative Wear (On / Off), see Hertz-Mindlin

Last

Hertz-Mindlin with JKR Cohesion

（

Hertz- MindlinJKR

粘结模型）

Hertz-Mindlin with JKR

(Johnson-Kendall-Roberts)

Cohesion

is a contact model that

allows users to represent the cohesive nature of fine and moist materials. Originally

implemented to allow the simulation of Van der Waals forces which influence the flow

behavior or fine, dry powders. This model may also be used to recreate the influence

that a moisture content has on the bulk flow of larger-scale materials such as iron ore

or wet grains. Remove the Hertz-Mindlin (no slip) contact model from the list when

using this model.

该接触模型允许使用内聚特性好和潮湿的材料。

最初该模型运用在仿真范德瓦尔斯力影< /p>

响流动行为或花岗石与干燥粉末。

这个模型还可用于重建水分含量 对铁矿石等大规模材

料的整体流或湿颗粒的影响。

Interaction

Particle to Particle,

Particle to Geometry

Configurable Parameters

Click

+

to add cohesion to particle-particle or particle-geometry

interactions. Set the surface energy for each interaction.

Surface energy is a property of the materials ability to retain

moisture/charge on its surface.

The amount of surface energy

influences the adhesion of the material. The SI units of surface

energy are J/m?

.

Particle to Geometry

Position

Last

Record Relative Wear (On / Off), see Hertz-Mindlin

Last

Use

1.

Select the required category from the Interaction pulldown in the Physics

section of the Creator.

2.

Click the

+

drop-down list then select

Hertz-Mindlin with JKR Cohesion

.