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*Spring Element

Purpose

To define the stiffness characteristics of spring elements

Theory

Refer to Spring Elements for further information on this feature.

Keyword Format

Two blocks of lines which define linear and non-linear spring elements and which may be repeated as often as necessary.

Definition of linear spring elements:

ELEMENT=List of Elements (Numbers or Labels)

TYPE=LINEAR

Stiffness

Definition of non-linear spring elements, with the third line repeated as often as necessary:

ELEMENT=List of Elements (Numbers or Labels)

TYPE=NONLINEAR

Displacement, Force

Up to 20 elements can be specified after ELEMENT=. At least two points are required for a non-linear spring force-deflection curve. If you specify an element label rather than an element number, it must be enclosed in {} brackets.

Table Input

Linear Springs (By Element)

Notes

(a)A spring element is wholly characterised by its spring stiffness, so no geometric or hydrodynamic properties should be attributed to it. Note that spring elements are massless and unaffected by distributed forces.

Linear Springs (By Set)

Notes

(a)A spring element is wholly characterised by its spring stiffness, so no geometric or hydrodynamic properties should be attributed to it. Note that spring elements are massless and unaffected by distributed forces.

Non-Linear Springs (By Element)

Notes

(a)Use as many lines as you need to completely define the force-deflection relationship for a particular list of elements. Simply leave Column 1 blank for second and subsequent lines. For subsequent lists, put the list in Column 1 and specify the spring characteristics in the same way.

(b)The force-deflection curve for non-linear spring elements may be specified in any order. Flexcom subsequently sorts the data pairs into ascending order of deflection.

(c)If the computed deflection of the spring element lies between the specified force-deflection data pairs, then Flexcom interpolates linearly to evaluate the force in the spring element.

(d)If the computed deflection of the spring element lies outside the specified range of the force-deflection curve, then Flexcom simply extrapolates from the first or last section of the curve as appropriate.

(e)If none of the specified displacement terms have a negative value, the curve is assumed to be symmetrical about the origin (i.e. the behaviour of the spring element is the same for both positive and negative deflections).

Non-Linear Springs (By Set)

Notes

(a)Use as many lines as you need to completely define the force-deflection relationship for a particular set. Simply leave Column 1 blank for second and subsequent lines. For subsequent sets, put the set name in Column 1 and specify the spring characteristics in the same way.

(b)The force-deflection curve for non-linear spring elements may be specified in any order. Flexcom subsequently sorts the data pairs into ascending order of deflection.

(c)If the computed deflection of the spring element lies between the specified force-deflection data pairs, then Flexcom interpolates linearly to evaluate the force in the spring element.

(d)If the computed deflection of the spring element lies outside the specified range of the force-deflection curve, then Flexcom simply extrapolates from the first or last section of the curve as appropriate.

(e)If none of the specified displacement terms have a negative value, the curve is assumed to be symmetrical about the origin (i.e. the behaviour of the spring element is the same for both positive and negative deflections).