Translational Friction
Friction when moving bodies come into contact .
blockType: AcausalFoundation.Mechanical.Translational.Elements.Friction
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Description
Block Translational Friction represents the friction in contact between moving bodies. The friction force is modeled as a function of relative velocity and calculated as the sum of the components of liquid, viscous, and mixed friction, as shown in the following figure.
Mixed friction, or Shtribek friction, It is a characteristic with a negative slope that occurs at low speeds. Dry or Coulomb friction results in a constant force at any speed. Viscous friction it counteracts movement with a force directly proportional to the relative velocity. The sum of mixed and dry friction near zero velocity is often called separation friction. . The friction is approximated by the following equations:
where
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— friction force;
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— dry (Coulomb) friction;
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— friction of rest;
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— critical speed;
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— speed threshold for Strobe friction;
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— the threshold of the Coulomb velocity;
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and — the absolute speeds of ports R and C, respectively;
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— relative velocity;
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— coefficient of viscous friction.
The exponential function used in the part of the Shtribek force equation is continuous and decays at velocity values exceeding the critical velocity.
The hyperbolic tangent function used in the Coulomb part of the force equation ensures that the relationship is smooth and continuous when passing through , but quickly reaches its full value at non-zero speeds.
The positive direction of the block is from port R to port C. This means that if the speed of port R is greater than the speed of port C, the block transfers power from R to C.
Variables
Use the parameter group Initial Targets to set the priority and initial target values for the block parameter variables before modeling. For more information, see Configuring physical blocks using target values.
Ports
Conserving
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R
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stock
translational mechanics
Details
A mechanical translational port corresponding to a rod, that is, a moving body.
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C
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housing
translational mechanics
Details
A mechanical translational port corresponding to the body, that is, a stationary body.
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Parameters
Parameters
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Breakaway friction force —
resting friction force
N | nN | uN | mN | kN | MN | GN | dyn | lbf | kgf
Details
The frictional force of rest. It must be greater than or equal to the parameter value. Coulomb friction force.
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Breakaway friction velocity —
the critical speed for the friction of the Strobe
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 speed at which the friction of the Strobe reaches its maximum. At this point, the sum of the Shtribek and Coulomb friction is equal to the value of the parameter Breakaway friction force. This parameter sets the speed threshold, which affects the trade-off between simulation accuracy and speed.
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Coulomb friction force —
dry friction force
N | nN | uN | mN | kN | MN | GN | dyn | lbf | kgf
Details
The force of Coulomb friction, that is, friction that opposes motion with a constant force at any speed.
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Yes |
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Viscous friction coefficient —
coefficient of viscous friction
N*s/m | kgf*s/m | lbf*s/ft | lbf*s/in
Details
The coefficient of proportionality between the friction force and the relative velocity. The parameter value must be greater than or equal to zero.
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Yes |