Idealized joints connect two parts. The parts can be rigid bodies, Flexible bodies, or Point masses. You can place idealized joints anywhere in your model.

Adams View supports two types of idealized joints: simple and complex. Simple joints directly connect bodies and include the following:

Complex joints indirectly connect parts by coupling simple joints. They include:

You access the joints through the Joint Palette and Joint and Motion Tool Stacks.

The following procedure explains how to create a simple idealized joint. You can select to attach the joint to parts or spline curves. If you select to attach the joint to a curve, Adams View creates a curve marker, and the joint follows the line of the curve. Learn more about curve markers with Marker Modify dialog box help. Attaching the joint to a spline curve is only available with Adams Solver (C++). Learn about switching solvers with Solver Settings - Executable dialog box help.

Note that this procedure only sets the location and orientation of the joint. If you want to set the friction of a joint, change the pitch of a screw joint, or set initial conditions for joints, modify the joint.

You can change several basic properties about an Idealized joints. These include:

You can specify initial conditions for revolute, translational, and cylindrical joints. Adams View uses the initial conditions during an Initial conditions simulation, which it runs before it runs a simulation of your model.

You can specify the following initial conditions for revolute, translational, and cylindrical joints:

If you specify initial conditions, Adams View uses them as the initial velocity of the joint during an assemble model operation regardless of any other forces acting on the joint. You can also leave some or all of the initial conditions unset. Leaving an initial condition unset lets Adams View calculate the conditions of the part during an assemble model operation depending on the other forces acting on the joint. Note that it is not the same as setting an initial condition to zero. Setting an initial condition to zero means that the joint will not be moving in the specified direction or will not be displaced when the model is assembled, regardless of any forces acting on it.

If you impose initial conditions on the joint that are inconsistent with those on a part that the joint connects, the initial conditions on the joint have precedence over those on the part. If, however, you impose initial conditions on the joint that are inconsistent with imparted motions on the joint, the initial conditions as specified by the motion generator take precedence over those on the joint.

You can impose a motion on any of the axes (DOF) of the idealized joint that are free to move. For example, for a translational joint, you can apply translational motion along the z-axis. Learn more About Point Motion.

You can model both static (Coulomb) and dynamic (viscous) friction in revolute, translational, cylindrical, hooke/universal, and spherical joints.

Three friction regimes are allowed in Adams View:

The joint velocity determines the instantaneous friction regime for a joint. The following is a block diagram of the friction regimes available in Adams Solver.

LuGre friction model is a type of state variable friction models, where extra state variables (internal states) are introduced to determine the level of friction. For LuGre friction model, the microscopic average bristle deflection z of the contact surface is adopted as the state variable. Therefore, the friction can be considered as the forces produced by the bending bristles. In 1D translational joint cases, the friction is given by

where is the bristle stiffness, is the microscopic damping, and is the viscous friction coefficient. Notice that since z represents the average deflection rate of the bristle while v is the velocity of the contact body. To determine the value of z, an additional differential equation is used in the formulation

where

N is the normal contact force, Fs and Fd are the maximum static friction and dynamic friction, and are dynamic and static frictional coefficients, respectively. Fss(v) represents the steady-state LuGre friction for a specific v, where and z=const.

For 1D revolute joint cases, the frictional forces between the pin and hole result in the frictional torque, which is given by

where Rp is the pin radius, is the angular displacement, . Based on Eq. (2), the additional differential equation is obtained as

where

represents the steady-state LuGre frictional torque for a specific , where and =const.

In the cases where only dry friction is considered, , which determines whether viscous friction is considered in the model, should be zero. Stribeck velocity vs is always small and is used to determine the range of Stribeck effect. Stribeck effect decay exponent is used to determine the decay speed (the shape of Stribeck effect curve), as shown in above figure. Different values between 0.5 and 2 are recommended in the literature, and =2 is the default in Adams.

The following tables identify conventions used in the block diagrams:

Joint reaction (F) and reaction torque (Tm) combined with force preload (Fprfrc) and torque preload (Tprfrc) yield the frictional force and torque in a cylindrical joint. Notice that Tm multiplies Cm/Xs where Cm stands for the BENDING_FACTOR. Cm was equal to 1.0 in releases previous to 2018. As the block diagram indicates, you can turn off one or more of these force effects using switches SW1 through SW3. The frictional force in a cylindrical joint acts at the mating surfaces of the joint. The FRD block determines the direction of the frictional force. Based on the frictional coefficient direction, the surface frictional force is broken down into an equivalent frictional torque and frictional force acting along the common axis of translation and rotation.

 

Joint reactions (Fa and Fr), bending moment (Tr), and torque preload (Tprfrc) determine the frictional torque in a revolute joint. You can turn off one or more of these force effects using switches SW1 through SW3. The joint reactions (Fa and Fr) are converted into equivalent torques using the respective friction arm (Rn) and pin radius (Rp). The joint bending moment (Tr) is converted into an equivalent torque using pin radius (Rp) divided by bending reaction arm (Rb). The frictional torque (Tfrict) is applied along the axis of rotation in the direction that the FRD block computes.

 

The reaction force (F) and the preload frictional torque (Tprfrc) are the two forcing effects used in computing the frictional torque on a Spherical joint. The ball radius is used to compute an equivalent frictional torque. The FRD block determines the direction of the frictional torque.

Joint reaction force (F), bending moment (Tm), torsional moment (Tn), and force preload (Fprfrc) are used to compute the frictional force in a translational joint. You can individually turn off the force effects using switches SW1 through SW4.

The bending moment (Tm) is converted into an equivalent force using the Cm/Xs block where Cm stands for the BENDING_FACTOR. Cm was equal to 1.0 in releases previous to 2018. Similarly, torsional moment is converted into an equivalent joint force using the friction arm (Rn). Frictional force (Ffrict) is applied along the axis of translation in the direction that the FRD block computes.

The universal/hooke joint contains two yokes (I_YOKE and J_YOKE) that are modeled independently. An equivalent revolute joint represents each yoke. Frictional torques are applied along the axes of rotation of the two yokes.

The following table lists all of the idealized joints except screw, gear, and coupler joints. It does not contain screw joints because they couple one rotational and one translational degree of freedom and cannot be placed in any one of the categories in the table. The table does not contain gears and couplers because they connect joints rather than parts.