### 14.1.7. Interactions - Lagrange/Lagrange - Friction

This window is available for Gap contact and lets you set static friction coefficients between two Parts.

Select Part 1

  Select the first of the two Parts you want to set the friction coefficient between in this box.

Select Part 2

  Select the second of the two Parts you want to set the friction coefficient between in this box.

Friction Coefficient

  Enter the friction coefficient you want to use.

Click to set the friction coefficient between the two selected Parts.

You can apply this procedure as many times as you like to set coefficients between other Parts without exiting the window.

This window is available for Trajectory contact and lets you define static and dynamic friction between two Parts.

Select Part 1

  Select the first of the two Parts you want to set the friction coefficient between in this box.

Select Part 2

  Select the second of the two Parts you want to set the friction coefficient between in this box.

Friction Coefficient

  - A non-zero value for the Static Friction coefficient will activate Coulomb type friction between bodies (F=μR).

  - A non-zero value for the Dynamic Friction coefficient and the Dynamic friction decay constant will activate the use of dynamic friction where an effective friction coefficient, μ, is used which is given by:

    | (14–1)

    where:

    μs = Static

    μd = Dynamic coefficient of friction

    β = Exponential decay coefficient

    v = Relative sliding velocity at point of contact

Click to set the friction coefficient between the two selected Parts.

You can apply this procedure as many times as you like to set coefficients between other Parts without exiting the window.

Note: When using gap contact, friction is not available for Interaction defined by Group. Friction is available when using group contact with trajectory contact. See Interactions - Lagrange/Lagrange - 3D Trajectory Contact Options for information on how to define friction coefficients when using group contact with trajectory contact.

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