Contact surface wear can be simulated by defining a wear model
(TB,WEAR) as a material assigned to contact elements. Two options are
available: the Archard wear model and a user-defined wear model (the
USERWEAR subroutine). These two options are discussed below. For
additional information, see Contact Surface Wear in the
Contact Technology Guide.
The Archard wear model defines the rate of wear as a function of contact pressure, sliding velocity, and material hardness. If a wear direction is not specified, the default direction of wear is opposite to the contact normal.
The Archard model is defined by the TB,WEAR command with
TBOPT = ARCD. The material constants required by the model
are specified as data items C1 through C4 on the TBDATA command. You
can also specify the wear direction (C6 to C8) if desired.
| Constant | Meaning |
|---|---|
| C1 | Wear coefficient, K |
| C2 | Material hardness, H |
| C3 | Pressure exponent, m |
| C4 | Velocity exponent, n |
| C5 | Optional flag to control how the wear increment is calculated (see below) |
| C6 | Direction cosine nx (with respect to the global X axis) for the wear direction |
| C7 | Direction cosine ny (with respect to the global Y axis) for the wear direction |
| C8 | Direction cosine nz (with respect to the global Z axis) for the wear direction |
The fifth constant, C5, can be used to specify additional controls:
Set C5 to 1 to base the wear calculation on nodal stresses. The nodal stresses of the solid element underlying the contact element are used to calculate traction along the contact normal direction. The traction value is used instead of contact pressure to calculate the amount of wear.
Set C5 to 10 or 11 to average the wear increment over the contact area of the contact pair. Use C5 = 10 to base the wear calculation on contact pressure; use C5 = 11 to base the wear calculation on nodal stress.
Set C5 to -99 to calculate wear for postprocessing purposes only. The Archard model is used to calculate the wear, but the contact nodes are not moved; thus wear is just a postprocessing variable and does not affect the solution.
Use the TBFIELD command to define the constants as a function of temperature and/or time. A sample input with constants as a function of time is shown below:
TB,WEAR,1,,,ARCD ! Activate Archard wear model TBFIELD,TIME,0 ! Define the first value of time TBDATA,1,K,H,m,n ! Define wear material constants for the first value of time TBFIELD,TIME,1 ! Define the second value of time TBDATA,1,K,H,m,n ! Define wear material constants for the second value of time
Alternatively, you can use the TBTEMP command to define the constants as a function of temperature alone. A sample input is shown below:
TB,WEAR,1,,,ARCD ! Activate Archard wear model TBTEMP,100 ! Define the first value of temperature TBDATA,1,K,H,m,n ! Define wear material constants for the first value of temperature TBTEMP,200 ! Define the second value of temperature TBDATA,1,K,H,m,n ! Define wear material constants for the second value of temperature
As an alternative to the Archard wear model, you can define your own wear model via
the user-programmable subroutine, USERWEAR. This subroutine
allows you to define the increment of wear for a substep. The default wear direction is
opposite to the contact normal. However, you can redefine it inside of
USERWEAR.
The user-defined wear model is activated by the TB,WEAR command
with TBOPT = USER. A sample command input is shown
below:
TB,WEAR,1,,4,USER ! Activate user defined wear model that requires 4 (NPTS = 4) constants TBDATA,1,C1,C2,C3,C4 ! Define the wear model constants
To speed up the wear simulation, use TB,WEAR with
TBOPT = AUTS or TBOPT = CBCS to
automatically scale the wear increment calculated by the specified Archard wear model or
user-defined wear model (TB,WEAR with
TBOPT = ARCD or USER).
Below is a sample command input for automatic scaling:
TB,WEAR,MATID,,,AUTS ! Activate automatic scaling of wear increment TBDATA,STLOC,C1,C2 ! Define wear scaling factor and max. scaling factor
Below is sample command input for cycle by cycle scaling:
TB,WEAR,MATID,,,CBCS ! Activate cycle by cycle scaling of wear increment TBDATA,STLOC,C1,C2 ! Define wear scaling factor and max. scaling factor
Use TBDATA to define the constants listed below. If not specified, the default values are used.
| Constant | Meaning | Default |
|---|---|---|
| C1 | Factor of safety for wear scaling (< 1) | 0.1 |
| C2 | Maximum wear scale factor | 1x105 |