BALL_RADIUS=Rb

Defines the radius of the ball in a spherical joint for use in friction-force and torque calculations.

Default: 1.0
Range: BALL_RADIUS > 0

BENDING_REACTION_ARM=Rb

Defines the effective moment arm use to compute the contribution of the bending moment on the net friction torque in revolute, hooke, and universal joints.

Default: 1.0
Range: BENDING_REACTION_ARM > 0

STICTION_TRANSITION_VELOCITY=r

Defines the absolute velocity threshold for the transition from dynamic friction to static friction. If the absolute relative velocity of the joint marker is below STICTION_TRANSITION_VELOCITY, then static friction or stiction acts to make the joint stick.

Default: 0.1 length units/unit time on the surface of contact in the joint.
Range: STICTION_TRANSITION_VELOCITY > 0

EFFECT={ALL[[STICTION, SLIDING]]}

Defines the frictional effects included in the friction model. Stiction is static-friction effect, while sliding is dynamic-friction effect. Excluding stiction in simulations that don’t require it can greatly improve simulation speed.

Default: All

FRICTION_FORCE_PRELOAD=r

Defines the joint’s preload frictional force, which is usually caused by mechanical interference in the assembly of the joint.

Default: 0.0
Range: FRICTION_FORCE_PRELOAD > 0

FRICTION_ARM=Rn

Defines the effective moment arm used to compute the axial component of the friction torque in revolute, hooke, and universal joints.

Default: 1.0
Range: FRICTION_ARM > 0

INACTIVE=STATIC

Specifies that frictional forces not be calculated for a static or quasi-static solution.

Default: none
Range: Static

INITIAL_OVERLAP=Xs0

Defines the initial overlap of the sliding parts in either a translational or cylindrical joint. The joint's bending moment is divided by overlap to compute the bending moment's contribution to frictional forces.

Default: 1000.0
Range: INITIAL_OVERLAP > 0

INPUTS=( {ALL, NONE [[PRELOAD: REACTION_FORCE: BENDING_MOMENT: TORSIONAL_MOMENT]]} )

Defines the input forces to the friction model. By default, all user-defined preloads and joint-reaction force and moments are included. You can customize the friction-force model by limiting the input forces you list in the statement.

Default: ALL

Joint Type: (Available inputs:)

Translational (PRELOAD, REACTION_FORCE, BENDING_MOMENT, TORSIONAL_MOMENT)

Cylindrical, Revolute, Universal, Hooke (PRELOAD, REACTION_FORCE, BENDING_MOMENT)

Spherical (PRELOAD, REACTION_FORCE)

JOINT=id

Identifies the joint to which frictional forces apply.

MAX_STICTION_DEFORMATION=r

Defines the maximum creep that can occur in a joint during the stiction regime. The creep allows Adams Solver (FORTRAN) to impose the Coulomb conditions for stiction or static friction, for example:

Friction force magnitude < µstatic * normal force

Therefore, even at zero velocity, a finite stiction force is applied if your system dynamics requires it.

Default: 0.01 length units
Range: MAX_STICTION_DEFORMATION > 0

MU_DYNAMIC=r

Defines the coefficient of dynamic friction. During the sliding regime, the magnitude of the frictional force is the product of MU_DYN and the magnitude of the normal force in the joint, for example:

Friction force magnitude, F = µN

where µ = MU_DYNAMIC and N = normal force
The dynamic frictional force acts in the opposite direction of the velocity of the joint.

Default: none
Range: MU_DYNAMIC > 0

MU_STATIC=r

Defines the coefficient of static friction in the joint. The magnitude of the frictional force is the product of a function fo MU_STAT, MU_DYNAMIC, and the creep times the magnitude of the normal force in the joint, for example:

Friction Force Magnitude, F = µN

where µ = f (MU_STATIC, MU_DYNAMIC, creep) and N = normal force
The static frictional force acts to oppose the net force or torque along the degrees of freedom of the joint.

Default: none
Range: MU_STATIC > 0

OVERLAP_DELTA={INCREASE, DECREASE, CONSTANT}

To define friction in a sliding joint (either a translational or a cylindrical joint), Adams Solver (FORTRAN) computes the overlap of the joint. As the joint slides, the overlap can increase, decrease, or remain constant. OVERLAP_DELTA is used to define any change in overlap.

Default: CONSTANT

MAX_FRICTION_FORCE = r

Defines the maximum of the friction force for use in translational or cylindrical joint.

Default: 1.0E+40

Range: MAX_FRICTION_FORCE > 0

FRICTION_FORCE_PRELOAD+MAX_FRICTION_FORCE.

MAX_FRICTION_TORQUE = r

Defines the maximum of the friction torque for use in revolute, universal, hooke, spherical, or cylindrical joint.

Default: 1.0E+40

Range: MAX_FRICTION_TORQUE > 0

FRICTION_TORQUE_PRELOAD+MAX_FRICTION_TORQUE.

TRANSITION_VELOCITY_COEFFICIENT = r

Defines the absolute velocity threshold for the transition from static friction to dynamic friction. If the absolute relative velocity of the joint marker is at or above TRANSITION_VELOCITY_COEFFICIENT * STICTION_TRANSITION_VELOCITY, then the dynamic friction coefficient is applied. Between STICTION_TRANSITION_VELOCITY and TRANSITION_VELOCITY_COEFFICIENT * STICTION_TRANSITION_VELOCITY the coefficient of friction is transitioning from the static coefficient of friction to the dynamic coefficient of friction.

Default: 1.5
Range: TRANSITION_VELOCITY_COEFFICIENT > 1

PIN_RADIUS=Rp

Defines the radius of the pin for a revolute, cylindrical, hooke, or universal joint.

Default: 1.0
Range: PIN_RADIUS > 0

REACTION_ARM=Rn

Defines the effective moment arm of the joint-reaction torque about the translational joint’s axial axis (the z-direction of the joint’s J marker). This value is used to compute the contribution of the torsional moment to the net frictional force.

Default: 1.0
Range: REACTION_ARM > 0

FRICTION_TORQUE_PRELOAD=r

Defines the preload friction torque in the joint, which is usually caused by mechanical interference in the assembly of the joint.

Default: 0.0
Range: FRICTION_TORQUE_PRELOAD > 0

I_YOKE J_YOKE

I_YOKE and J_YOKE define the rotational constraint on which the FRICTION statement acts. I_YOKE identifies the yoke to the I marker’s rotational constraint. Likewise, J_YOKE identifies the yoke to the J marker’s rotational constraint. These keywords are used with only hooke and universal joints.

_________

Scalar quantity

Vector quantity

 

 

Summing junction:
c=a+b

 

 

Multiplication junction:
c=axb

MAG

Magnitude of a vector quantity

ABS

Absolute value of a scalar quantity

FRD

Friction regime determination

SW1

PRELOAD

Fprfrc or Tprfc

ON/OFF

SW2

REACTION FORCE

or F

ON/OFF

SW3

BENDING MOMENT

ON/OFF

SW4

TORSIONAL MOMENT

Tn

ON/OFF

 

ALL/NONE sets all applicable switches ON/OFF, respectively

 

 

Dynamic friction

A joint is in dynamic friction if its joint velocity magnitude exceeds the value of the transition velocity coefficient multiplied by the friction transition velocity. The dynamic coefficient of friction (md) is used in the computation of frictional forces.

Transition between dynamic and static friction

If the joint velocity magnitude is between the value of the transition velocity coefficient multiplied by the stiction transition velocity and friction transition velocity, the joint is considered to be transitioning between static and dynamic friction. A STEP function transitions the coefficient of friction between the dynamic (md) and static (ms) coefficients of friction.

Static friction

A joint is in static friction when the joint velocity magnitude falls below the stiction transition velocity. The effective coefficient of friction is computed using the joint creep, joint velocity, and static coefficient of friction (ms).