Loaded-contact friction between two rotating surfaces

**Library:**Simscape / Driveline / Brakes & Detents / Rotational

The Loaded-Contact Rotational Friction block simulates friction between two rotating surfaces loaded with a normal force.

The block is implemented as a structural component based on the Fundamental Friction Clutch block. From the locked state, the two surfaces unlock if the transmitted torque exceeds the static friction, as defined by the static coefficient of friction and current normal force. For details on how the locking and unlocking are modeled, see the Fundamental Friction Clutch block reference page.

Torque is transmitted for normal forces larger than the **Threshold
force** parameter.

The block simulates friction between two rotating surfaces loaded with a normal force. When the two rotating surfaces are not locked, the transmitted torque is determined with the following equations:

$$\tau =N\xb7\mu \xb7{r}_{\text{eff}}\xb7\text{sign}(\omega )\text{}+{\tau}_{\text{visc}},$$

$${r}_{\text{eff}}=\frac{2}{3}\cdot \frac{{r}_{o}^{3}-{r}_{i}^{3}}{{r}_{o}^{2}-{r}_{i}^{2}},$$

$${\tau}_{visc}={\mu}_{\text{visc}}\xb7\text{}\omega ,$$

where:

*τ*is the transmitted torque.*N*is the normal force.*μ*is the friction coefficient.*r*is the effective radius._{eff}*r*is the surface outside radius._{o}*r*is the surface inside radius._{i}*ω*is the relative angular velocity.*τ*is the viscous drag torque._{visc}*μ*is the viscous drag torque coefficient._{visc}

You can model the effects of rotational velocity change by selecting a
velocity-dependent model. To choose a velocity-dependent model, in
the **Friction** settings, set the
**Friction model** parameter to
```
Velocity-dependent kinetic friction
coefficient
```

. For information about a friction
model that depends on both velocity and temperature, see Thermal, Velocity-Dependent Model.

For the velocity-dependent model these related parameters become
visible in the **Friction** settings:

**Relative velocity vector****Kinetic friction coefficient vector****Friction coefficient interpolation method****Friction coefficient extrapolation method**

You can model the effects of heat flow and temperature change by
selecting a temperature-dependent model. To choose a
temperature-dependent model, in the **Friction**
settings, set the **Friction model** parameter to
```
Temperature-dependent friction
coefficients
```

. For information about a friction
model that depends on both velocity and temperature, see Thermal, Velocity-Dependent Model.

For the temperature-dependent model, thermal port
**H** and these settings are visible:

In the

**Friction**settings:**Temperature vector****Static friction coefficient vector****Kinetic friction coefficient vector****Friction coefficient interpolation method****Friction coefficient extrapolation method**

In the

**Thermal Port**settings:**Thermal mass****Initial Temperature**

You can model the effects of rotational velocity change and heat flow
by selecting a velocity-dependent and temperature-dependent model.
To choose a model that depends on both velocity and temperature, in
the **Friction** settings, set the
**Friction model** parameter to
```
Temperature and velocity-dependent friction
coefficients
```

.

For the velocity-dependent and temperature-dependent model, thermal
port **H** and these related settings and
parameters become visible:

In the

**Friction**settings:**Relative velocity vector****Temperature vector****Static friction coefficient vector****Kinetic friction coefficient matrix****Friction coefficient interpolation method****Friction coefficient extrapolation method**

In the

**Thermal Port**settings:**Thermal mass****Initial Temperature**

The model does not account for inertia. Add inertia terms externally to the

**B**and**F**ports as required.The model computes the torque assuming a uniform distribution of the normal force.