Contacts Panel - Properties Tab - Rigid to Rigid Contact

Parameters for normal and friction force calculations are defined in the Properties tab of the Contacts panel.

contact_properties_tab

Contacts panel - Properties tab - Normal Force

Normal Force

This tab is used to set the method and related properties to calculate the normal force during contact. The following four models for defining the normal force are supported:

•

IMPACT

•

POISSON

•

VOLUME

•	USER-DEFINED

Refer to the Force_Contact MotionSolve statement for additional details regarding each method.

Impact

Use the Impact method for normal force calculation.

contact_properties_normal_force_tab_impact_mv

Impact contact properties:

contact_properties_normal_force_tab_impact_formula_mv

Stiffness (k)

The stiffness of the boundary surface interaction.

Stiffness > 0

Exponent (e)

The exponent on penetration depth in the force-penetration depth characteristic of the contact interface. For a stiffening spring characteristic, it must be greater than 1.0. For a softening spring characteristic, it must be less than 1.0.

Exponent > 1.

Damping (cmax)

The maximum damping coefficient. This value should be greater than 0.0.

Penetration depth (d)

The depth beyond which full damping is applied.

Poisson

Use the Poisson method for normal force calculation.

contact_properties_normal_force_tab_poisson_mv

Poisson contact properties:

contact_properties_normal_force_tab_poisson_formula_mv

where,

•	K Penalty parameter (stiffness).

•	z Contact penetration depth.

•	CR The coefficient of restitution. This is equal to 0 for a perfectly plastic collision and 1 for a perfectly elastic collision.

•	vnorm, trans Normal velocity at which full damping is applied.

Penalty

Determines the local stiffness properties between materials. Larger values lead to reduced penetration between two bodies.

Restitution coefficient

Represents the energy loss between the two bodies in contact. The valid range for this value is between 0.0 and 1.0. A value of 1.0 represents no energy loss and a perfectly elastic contact. A value of 0.0 represents a perfectly plastic contact and all energy is dissipated during contact.

Normal transition velocity

Velocity limit after which full damping force is applied.

Use augmented
Lagrangian formulation

Applicable for the ADAMS SolverMode only. Used to refine the accuracy of the normal force between the two bodies.

Volume Model

This based on an Elastic foundation model. The rigid bodies in contact are assumed to be covered by thin elastic layers. If the tangential shear stress in the layer is ignored, a direct relationship can be found between the normal pressure and normal displacement. This relationship can be used to generate the force between two contacting layers. This model is well-known in the literature regarding contacts.

contact_properties_normal_force_tab_volume_model_mv

Volume Model properties:

contact_properties_normal_force_tab_vol_model_formula_mv

where,

•	K Contact stiffness

•	z Contact penetration depth

•	exp Exponent for the force deformation characteristic

•	c Damping coefficient

•	Acon Area of contact

The VOLUME model assumes that both the colliding bodies are surrounded by a layer of springs whose stiffness is determined by the material’s elastic modulus properties and the depth of this layer. The individual stiffness for each body (I and J) is calculated as:

contact_properties_normal_force_tab_vol_model_formula2_mv

where,

•	ci, cj Stiffness parameter for I and J bodies, respectively

•	Mi, Mj Elastic Modulus for I and J bodies, respectively

•	di, dj Layer depth for I and J bodies, respectively

The equivalent contact stiffness is calculated assuming that the springs for body I and J are in series:

Bulk Modulus

The bulk modulus of a substance measures the resistance of a substance to uniform compression. It is defined as the ratio of the infinitesimal pressure increase to the resulting relative decrease of the volume.

Shear Modulus

The shear modulus or modulus of rigidity, denoted by G, is defined as the ratio of shear stress to the shear strain.

Layer Depth

The layer depth of material.

Exponent

The exponent of the force deformation characteristic.

Damping

The damping coefficient value.

User Defined

Uses a user defined subroutine to calculate the contact normal force.

Refer to Subroutine Interface to MotionSolve to learn more about how user subroutines can be used with MotionSolve.

contact_properties_normal_force_tab_user_def_mv

The following User Defined contact properties are available:

User expr

An expression containing the USER function with parameters that call the subroutine during solution.

Use local file and
function name

Activate the check box to specify a local file containing a subroutine. See Function Type below for supported types of subroutines. If this option is not specified, MotionSolve will search for a subroutine following its User Subroutine Loading Rules.

Function Type

The type of subroutine. A DLL (SO in Linux), Python, and Matlab are all types of subroutines which are supported by MotionSolve.

Local File

Provide a file name containing the subroutine based on the Function Type selected.

Function name

The name of the function within the subroutine to be called by the solver. If no function name is provided, MotionSolve will search for the default function CNFSUB.

Friction Force

This tab is used to determine the options to include or exclude coulomb friction in the calculation of the contact force.

contact_properties_friction_force_tab_mv

Disabled	Friction is turned off.
Dynamics Only	Only dynamic friction or sliding friction is considered in friction calculations. The static regime and transition to sliding is ignored.
Static & Dynamic	All three regimes are considered in friction calculations: static, transition to sliding friction, and sliding friction.
	The following friction properties are available in the case of Dynamic Only or Static & Dynamic:
	MU Static	The static coefficient of friction, which has to be overcome by a body before it can move. Not applicable for Dynamic Only.
	MU Dynamic	The coefficient of friction, which the body experiences while in motion.
	Stiction transition velocity	The velocity limit below which the coefficient of friction becomes MU static. When the slip velocity is between stiction transition velocity and friction transition velocity, the coefficient of friction is in transition between the two. Not applicable for Dynamic Only.
	Friction transition velocity	The velocity above which the coefficient of friction becomes MU dynamic. When the slip velocity is between stiction transition velocity and friction transition velocity the coefficient of friction is in transition between the two.
User Defined	A user subroutine is used to determine friction force.
	User expr	An expression containing the USER function with parameters that call the subroutine during solution.
	Use local file and function name	Activate the check box to specify a local file containing a subroutine. See Function Type below for supported types of subroutines. If this option is not specified, MotionSolve will search for a subroutine following its User Subroutine Loading Rules.
	Function Type	The type of subroutine. A DLL (SO in Linux), Python, and Matlab are all types of subroutines which are supported by MotionSolve.
	Local File	Provide a file name containing the subroutine based on the Function Type selected.
	Function name	The name of the function within the subroutine to be called by the solver. If no function name is provided, MotionSolve will search for the default function CFFSUB.

Note Refer to the Force_Contact MotionSolve statement for additional information on the contact method and friction options.