17.2.3 Connector damping behavior

Products: ABAQUS/Standard ABAQUS/Explicit ABAQUS/CAE

References

Overview

Dashpot-like connector damping behavior:

can be defined in any connector with available components of relative motion;
can be specified for each available component of relative motion independently, in which case the behavior can be linear or nonlinear;
can be specified as dependent on relative positions or constitutive motions in several local directions; and
can be specified for all available components of relative motion as coupled damping behavior.

The directions in which the forces and moments act and the relative velocities are measured are determined by the local directions as described in “Connection-type library,” Section 17.1.5, for each connection type.

Defining linear uncoupled damping behavior

In the simplest case of linear uncoupled damping you define the damping coefficients for the selected components (i.e., for component 1, for component 2, etc.), which are used in the equation

where

is the force or moment in the

component of relative motion and

is the velocity in the

direction. The damping coefficient can depend on frequency (in ABAQUS/Standard), temperature, and field variables. See “Input syntax rules,” Section 1.2.1, for further information about defining data as functions of frequency, temperature, and field variables.

Input File Usage:	Use the following options to define linear uncoupled damping connector behavior:
	CONNECTOR BEHAVIOR, NAME=name* CONNECTOR DAMPING, COMPONENT=component number*, DEPENDENCIES=n

ABAQUS/CAE Usage:

Interaction module: connector property editor: AddDamping: Definition: Linear, Force/Moment: component or components, Coupling: Uncoupled

Defining linear coupled damping behavior

In the linear coupled case you define the damping coefficient matrix components, , which are used in the equation

where

is the force in the

component of relative motion,

is the velocity in the

component, and

is the coupling between the

and

components. The

matrix is assumed to be symmetric, so only the upper triangle of the matrix is specified. In connectors with kinematic constraints the entries that correspond to the constrained components of relative motion will be ignored. The damping coefficient can depend on temperature and field variables. See “Input syntax rules,” Section 1.2.1, for further information about defining data as functions of temperature and field variables.

Input File Usage:	Use the following options to define linear coupled damping connector behavior:
	CONNECTOR BEHAVIOR, NAME=name* *CONNECTOR DAMPING, DEPENDENCIES=n

ABAQUS/CAE Usage:

Interaction module: connector property editor: AddDamping: Definition: Linear, Force/Moment: component or components, Coupling: Coupled

Defining nonlinear damping behavior

For nonlinear damping you specify forces or moments as nonlinear functions of the velocity in the available components of relative motion directions, . These functions can also depend on temperature and field variables. See “Input syntax rules,” Section 1.2.1, for further information about defining data as functions of temperature and field variables.

Defining nonlinear damping behavior that depends on one component direction

By default, each nonlinear force or moment function is dependent only on the velocity in the direction of the specified component of relative motion.

Input File Usage:	Use the following options:
	CONNECTOR BEHAVIOR, NAME=name* CONNECTOR DAMPING, COMPONENT=component number*, NONLINEAR, DEPENDENCIES=n

ABAQUS/CAE Usage:

Interaction module: connector property editor: AddDamping: Definition: Nonlinear, Force/Moment: component or components, Coupling: Uncoupled

Defining nonlinear damping behavior that depends on several component directions

Alternatively, the functions can depend on the relative positions or constitutive displacements/rotations in several component directions, as described in “Defining connector properties to depend on local directions” in “Connector behavior,” Section 17.2.1.

Input File Usage:

Use the following options to define nonlinear damping connector behavior that depends on components of relative position:

*CONNECTOR BEHAVIOR, NAME=name 
*CONNECTOR DAMPING, COMPONENT=component number, 
NONLINEAR, INDEPENDENT COMPONENTS=POSITION, 
DEPENDENCIES=n

Use the following options to define nonlinear damping connector behavior that depends on components of constitutive displacements or rotations:

*CONNECTOR BEHAVIOR, NAME=name 
*CONNECTOR DAMPING, COMPONENT=component number, 
NONLINEAR, INDEPENDENT COMPONENTS=CONSTITUTIVE MOTION, 
DEPENDENCIES=n

ABAQUS/CAE Usage:

Interaction module: connector property editor: AddDamping: Definition: Nonlinear, Force/Moment: component or components, Coupling: Coupled on position or Coupled on motion

Example

Refer to the example in Figure 17.2.3–1.

Figure 17.2.3–1 Simplified connector model of a shock absorber.

In addition to the torsional spring resisting relative rotations, the shock absorber damps translational motion along the line of the shock with a dashpot. To include a nonlinear dashpot coefficient that is dependent on the relative position between the attachment points, use the following input:

*CONNECTOR BEHAVIOR, NAME=sbehavior
...
*CONNECTOR DAMPING, COMPONENT=1,
 INDEPENDENT COMPONENTS=POSITION
1500.0, , 0.0
1750.0, , 10.0
1925.0, , 45.0

Defining connector damping behavior in linear perturbation procedures

In direct-solution or subspace-based steady-state dynamic procedures, the damping defined using an uncoupled connector damping behavior may be frequency dependent. In all other linear perturbation procedures connector damping behavior is ignored.

Output

The ABAQUS output variables available for connectors are listed in “ABAQUS/Standard output variable identifiers,” Section 4.2.1, and “ABAQUS/Explicit output variable identifiers,” Section 4.2.2. The following output variables are of particular interest when defining damping in connectors:

CV	Connector relative velocities/angular velocities.

CVF	Connector viscous forces/moments.