Spring Elements |
 
|
Spring Elements |
|
A spring element provides a restoring force which is directly proportional to the relative movement of its end nodes. The magnitude of the force is defined according to the following relationship:
(1)
where 
is the restoring force, 
is the spring stiffness and 
is the relative displacement between the end nodes of the spring element (the change in length of the spring element from its original length).
The spring may be characterised by a linear (constant) stiffness value, or defined in terms of a non-linear force-displacement relationship. The line of action of the spring is always aligned with the element axis, and the restoring force is such that it opposes the change in length – so the spring is in tension when the element extends, and in compression when the element contracts. The behaviour of a linear spring element is the same in tension and contraction, but the non-linear spring element offers complete generality in this regard.
In terms of directionality, the convention in Flexcom is that spring extensions constitute positive displacements. Spring compression (i.e. element contraction) is considered a negative displacement. This convention should be borne in mind when defining non-linear force-displacement relationships for non-linear springs.
•*SPRING ELEMENT is used to define the stiffness characteristics of spring elements.
If you would like to see an example of how this keyword is used in practice, refer to H03 - Articulated Stinger.
•*NODE SPRING is used to specify the stiffness and direction of node springs.