Translational

A translational joint is a one degree-of-freedom kinematic pair used in mechanisms. Translational joints provide single-axis rotation function in places such as splined shafts and slider mechanisms.

1. If the Joints panel is not currently displayed, select the desired joint by clicking on it in the Project Browser or in the modeling window.
   The Joints panel is automatically displayed.
2. From the Connectivity tab, click Body 1 and pick a body from the modeling window, or double-click Body 1 to open the Model Tree (from which the desired body can be selected).
   Note: If the selected joint is a pair entity, first distinguish between the Left and Right tabs in the panel, and then edit the properties. When defining a pair joint, use pair entities for Body, Origin, etc.
3. Similarly, click Body 2 and select the desired body from the modeling window (or use the Model Tree).
4. Click the Point collector (under Origin) and select a point from the modeling window, or double click the Point collector to open the Model Tree (from which the desired point can be selected).
5. Specify the alignment axis for the joint.
   • Point - Select a point that lies on the desired alignment axis for the joint.
   • Vector - If the alignment axis for the joint is along any of the global axes, then the global x, y,or z axis can be selected by clicking on the desired axis in the modeling window or by browsing through the Model Tree.
6. Define initial conditions.
   1. Click the Initial Conditions tab on the panel.
   2. Activate the Translation check box.
   3. Enter values for displacement and velocity.
7. Specify the frictional properties for the joint.
   1. Activate the Use Friction check box from the Friction Properties tab.
      The Friction Properties tab displays.
   2. Specify the friction coefficients, effect options, and geometrical parameters.
      • The Stiction Transition Velocity determines the velocity at which the friction regime transitions from stiction to dynamic friction.
      • Force Preload: Specify the preload force in the joint (*if a preload effect is activated).
      • Initial Overlap: Specify the initial overlap of the sliding bodies connected by the joint.
      • Reaction Arm: Specify the moment arm about the translational joint axial axis used in computing the contribution of the torsional moment on joint friction.
      • Overlap Delta: Specify the overlap of the joint, as the connecting bodies slide.
   1. Click the LuGre Parameters tab and input desired values.
      MotionSolve uses the LuGre (Lundt-Grenoble) model for friction. Refer to the MotionSolve Force_JointFriction modeling statement for additional details.

      • Bristle stiffness: Specify the bristle stiffness in the LuGre model. This models the stiffness resisting micro-deformation in the friction element.
      • Damping Coefficient: Specify the damping coefficient for the pre-displacement (or stiction) regime. This damps out bristle vibrations in the pre-displacement regime.
      • Viscous Coefficient: Specify the coefficient for the viscous damping force that occurs when relative sliding actually begins. This is responsible for the increase in friction force with the increase in the slip velocity.