Loaded-Contact Translational Friction

Contact friction with a load between two sliding surfaces.

blockType: Engee1DMechanical.Brakes.LoadedContactTranslationalFriction

Path in the library:

/Physical Modeling/1D Mechanical/Brakes & Detents/Translational/Loaded-Contact Translational Friction

Description

Block Loaded-Contact Translational Friction simulates the friction between two sliding surfaces loaded with a normal force.

The block is implemented as a block-based structural component Fundamental Friction Clutch. From the locked state, the two surfaces are released if the applied force exceeds the static friction determined by the static coefficient of friction and the current normal force. For more information about how locking and unlocking are modeled, see the section Fundamental Friction Clutch.

The force is transmitted by a normal force exceeding the value of the parameter Threshold force.

The equations

This block simulates the friction between sliding surfaces loaded with a normal force. When the two sliding surfaces are not locked, the friction force is determined using these equations:

where

– transmitted power;
– normal strength;
– coefficient of friction;
– relative velocity;
– the strength of viscous resistance;
– coefficient of viscous friction.

A speed-dependent model

You can simulate the effects of speed changes by selecting a speed-dependent model. To select a speed-dependent model in the parameter group Friction set for the parameter Friction model meaning Velocity-dependent kinetic friction coefficient. For information about the friction model, which depends on both velocity and temperature, see Thermal, velocity-dependent model.

For a speed-dependent model, set the parameter values in the parameter group Friction:

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

The thermal model

You can simulate the effects of heat transfer and temperature changes by selecting a temperature-dependent model. To select a temperature-dependent model in the parameter group Friction set for the parameter Friction model meaning Temperature-dependent friction coefficients. For information about the friction model, which depends on both velocity and temperature, see Thermal, velocity-dependent model.

When using a temperature-dependent model, the unit has a thermal port H. To configure the model, set the parameter values:

in the parameter group Friction:
- Temperature vector
- Static friction coefficient vector
- Kinetic friction coefficient vector
- Friction coefficient interpolation method
- Friction coefficient extrapolation method
in the parameter group Thermal Port:
- Thermal mass
- Initial Temperature

Thermal, velocity-dependent model

You can simulate the effects of changes in velocity and heat flow by selecting a model that depends on velocity and temperature. To select a model that depends on both speed and temperature, in the parameter group Friction set for the parameter Friction model meaning Temperature and velocity-dependent friction coefficients.

When using a model that depends on speed and temperature, the unit gets a thermal port H. To configure the model, set the parameter values:

in the parameter group Friction:
- Relative velocity vector
- Temperature vector
- Static friction coefficient vector
- Kinetic friction coefficient matrix
- Friction coefficient interpolation method
- Friction coefficient extrapolation method
in the parameter group Thermal Port:
- Thermal mass
- Initial Temperature

Limitations and assumptions

The model does not take inertia into account. If necessary, add inertia conditions from the outside to ports B and F.
The model calculates the transmitted force, assuming a uniform distribution of the normal force.

Ports

Input

# N — normal force
scalar

Details

Input port associated with normal force. The value can be positive or zero. A value less than zero is equated to zero.

Data types	`Float64`
Complex numbers support	No

Conserving

# F — driven (moving) surface
post-traumatic mechanics

Details

An undirected port connected to a slave (movable) surface.

Program usage name

follower_flange

# B — base surface
translational mechanics

Details

An undirected port connected to the drive (base) surface.

Program usage name

base_flange

Parameters

Friction

# Friction model — the friction model
Fixed kinetic friction coefficient | Velocity-dependent kinetic friction coefficient | Temperature-dependent friction coefficients | Temperature and velocity-dependent friction coefficients

Details

Parameterization method for modeling sliding friction coefficient:

Fixed kinetic friction coefficient — a fixed value is set for the sliding friction coefficient.
Velocity-dependent kinetic friction coefficient — The coefficient of sliding friction is determined by the search table based on the relative velocity between the surfaces.
Temperature-dependent friction coefficients — The coefficient of sliding friction is determined by the temperature-based search table.
Temperature and velocity-dependent friction coefficients — The coefficient of sliding friction is determined by the search table based on the temperature and relative velocity between the surfaces.

Values	`Fixed kinetic friction coefficient` \| `Velocity-dependent kinetic friction coefficient` \| `Temperature-dependent friction coefficients` \| `Temperature and velocity-dependent friction coefficients`
Default value	`Fixed kinetic friction coefficient`
Program usage name	`kinetic_friction_coefficient_type`
Evaluatable	No

# Static friction coefficient — coefficient of static friction

Details

Static or peak value of the coefficient of friction. The static coefficient of friction must be greater than the kinetic coefficient of friction.

Dependencies

To use this parameter, set for the parameter Friction model meaning Fixed kinetic friction coefficient or Velocity-dependent kinetic friction coefficient.

Default value	`0.35`
Program usage name	`static_friction_coefficient_const`
Evaluatable	Yes

# Kinetic friction coefficient — coefficient of sliding friction

Details

Coefficient of kinetic or Coulomb friction. The coefficient must be greater than zero.

Dependencies

To use this parameter, set for the parameter Friction model meaning Fixed kinetic friction coefficient.

Default value	`0.3`
Program usage name	`coulomb_friction_coefficient_const`
Evaluatable	Yes

# Velocity tolerance — threshold value of relative blocking speed
m/s | mm/s | cm/s | km/s | m/hr | km/hr | in/s | ft/s | mi/s | ft/min | mi/hr | kn

Details

The relative velocity below which two surfaces can lock. The surfaces are blocked if the moment of friction forces through ports B and F is less than the product of the effective radius, the coefficient of static friction and the applied normal force.

Units	`m/s` \| `mm/s` \| `cm/s` \| `km/s` \| `m/hr` \| `km/hr` \| `in/s` \| `ft/s` \| `mi/s` \| `ft/min` \| `mi/hr` \| `kn`
Default value	`0.001 m/s`
Program usage name	`v_slip_threshold`
Evaluatable	Yes

# Threshold force — threshold of normal contact force
N | nN | uN | mN | kN | MN | GN | dyn | lbf | kgf

Details

The normal force applied to the scalar port N is applied to the contact only if the magnitude of the force exceeds the value of the parameter Threshold force. The force is less than the parameter value Threshold force they are not applied, so the moment of friction forces is not transmitted.

Units	`N` \| `nN` \| `uN` \| `mN` \| `kN` \| `MN` \| `GN` \| `dyn` \| `lbf` \| `kgf`
Default value	`1.0 N`
Program usage name	`F_vertical_threshold`
Evaluatable	Yes

Viscous Losses

# Viscous drag torque coefficient — coefficient of viscous resistance
N*s/m | kgf*s/m | lbf*s/ft | lbf*s/in

Details

Coefficient of viscous friction , to calculate the friction force. The coefficient depends on the type of working fluid, the temperature of the fluid, and the maximum distance between the surfaces.

Units	`Ns/m` \| `kgfs/m` \| `lbfs/ft` \| `lbfs/in`
Default value	`0.0 N*s/m`
Program usage name	`viscous_coefficient`
Evaluatable	Yes

Initial Conditions

# Initial state — initial condition of the coupling
Unlocked | Locked

Details

The condition of the indoor unit Fundamental Friction Clutch at the beginning of the simulation.

Unlocked – ports B and F are initially sliding relative to each other.
Locked – ports B and F are initially locked together.

Values	`Unlocked` \| `Locked`
Default value	`Unlocked`
Program usage name	`initial_state`
Evaluatable	No