38.1.1. Bearing Contact Characteristic

Figure 38.2 Bearing Contact Characteristic dialog box

• Stiffness Coefficient: Specifies a stiffness coefficient for the contact normal force.

• Damping Coefficient: Specifies a viscous damping coefficient for the contact normal force.

• Friction Coefficient: Specifies a dynamic friction coefficient for the contact friction force.

  • They can also be given as user-defined spline curves.

• Friction: Specifies some friction coefficients for the contact friction force as shown in Figure 38.4.

  

  Figure 38.3 Contact friction dialog box

  • Static Threshold Velocity: If the relative velocity between a contact pair is less than this value, the friction coefficient is defined as follows:

    \(\mu =\text{step5}(\nu ,\,\,-{{\nu }_{s}},\,\,{{\mu }_{s}},\,\,{{\nu }_{s}},\,\,-{{\mu }_{s}}\,)\)

  • Dynamic Threshold Velocity :If the relative velocity between a contact pair is greater than :

    This value, the friction coefficient is the same as the specified dynamic friction coefficient.

    The Static Threshold Velocity and less than this value, the friction coefficient is defined as follows:

    \(\mu =\text{step5}\,(\nu ,\,\,{{\nu }_{s}},\,\,-{{\mu }_{s}},\,\,{{\nu }_{d}},\,\,-{{\mu }_{d}}\,)\)

  • Static Friction Coefficient: Specifies the static friction coefficient.

  • Maximum Friction Force: Is checked, the contact friction force is limited to this value.

    

    Figure 38.4 Relationship between relative velocity and friction coefficient

    The friction force of contact elements is determined by the following equations.

    \({{f}_{f}}=-\,\text{sign}\,(v)\,\,\left| \mu (v) \right|\,\,\left| {{f}_{n}} \right|\)

    \({{f}_{f}}=\,\text{sign}\,({{f}_{f}})\,\times \min \left( \left| {{f}_{f}} \right|,{{f}_{\max }} \right)\)

    where, \(f_n\), \(\mu(v)\), and \(f_{max}\) are the Contact normal force, Friction coefficient and Maximum friction force. The friction coefficient of \(f_f\) is determined by a relative and tangential velocity on the contact point.

• Buffer Radius Factor: Allows the numerical integrator reduces the step size by the maximum Stepsize factor if the action body comes closer than the Buffer radius factor* Action body radius.

• Maximum Stepsize Factor: Allows the maximum step size is reduced by a factor of the maximum step size factor.