Flexcom > Data Inputs > $MODEL

Purpose

To define damper elements in the structural discretisation.

Theory

Refer to Damper Elements for further information on this feature.

Keyword Format

At least one line (in the case of translational damper) repeated as often as necessary.

[TYPE=TRANSLATIONAL]

Element (Number or Label) [, C1 or C1=Name] [, C0 or C0=Name] [, C2 or C2=Name]

[, C0_THRESHOLD=C0_Threshold]

[TYPE=ROTATIONAL]

Element (Number or Label) [, C1]

All coefficients default to zero. If TYPE= not specified it defaults to TRANSLATIONAL. For translational dampers, each coefficient may be specified in terms of a single value, or as a series of values which depend on time or velocity. For rotational dampers, the damping coefficient must be a single numerical value. You must use the *DAMPER DATA keyword to define any damping coefficient relationship you reference here.

Table Input

Translational Damper Elements

Input:	Description
Element:	The element (number or label) of the damper element. If you specify an element label rather than an element number, it must be enclosed in {} brackets.
Linear Coefficient (C1):	The linear damping coefficient for the damper element.
Constant Force (F0):	The constant damping force for the damper element.
Quadratic Coefficient (C2):	The quadratic damping coefficient for the damper element
Velocity Threshold:	A velocity threshold below which the constant damping force is linearly ramped. By default no ramping is applied, so the constant damping force is applied in full at all times.

Rotational Damper Elements

Input:	Description
Element:	The element (number or label) of the damper element. If you specify an element label rather than an element number, it must be enclosed in {} brackets.
Linear Coefficient (C1):	The linear damping coefficient for the damper element.

Notes

(a)For translational damper elements, the axial force exerted by the element, F, is defined as follows:

where is the relative velocity between the element end nodes in the axial direction of the element, F0 is the constant damping force, and C1 & C2 are the linear and quadratic damping coefficients respectively. Each coefficient may be specified in terms of a single value, or as the name of a damping coefficient relationship. Refer to Damper Elements for further information.

(b)For rotational damper elements, the moment exerted by the element, M, is defined as follows:

where is the relative rotational velocity between the element end nodes and C1 is the linear damping coefficient.

(c)If the name of a damping coefficient relationship is specified, then the relationship must be defined in the *DAMPER DATA keyword.