Non Linear Spring 01
Introduction:
(If you want to skip this intro, just click here)
The Usfos Non Linear Spring element is a 1 node element (Spring to Ground), which gets it's properties in the 6 degrees of freedom by the P_d curves referred to through the material reference MREF. All 6 degrees of freedom may have different properties, and refrerring to P_D curve with ID=0, the actual degree of freedom gets no stiffenss. The properties defined for the non linear spring to ground are referred to the global coordinate system, but local (skew) syetems may be defined (3x3 transformation matrix).
The non linear spring has following properties, only one (bold) is mandatroty, the rest are optional:
Non linear Spring behaviour:
Properties of the spring are defined by discrete points as shown in the figure below. (If pure linear behaviour is required, specify a straight P_d curve or try the 1 node linear spring).
The curves are always defined from the very left side (3'rd qudrant) towards right (1'st quadrant) as indicated above. The curve may have any shape, and different behaviour in tension (1'st quadrant) and compression (3'rd quadrant) is possible. F ex: A simple contact spring is obtained by specifying ~Zero tension capacity and relatively high stiffenss in compression (too high stiffness might cause numerical problems!).
Single Beam with Nonlinear Spring Support
A linear spring to ground is attached to both end 1 and 2 of the beam. The spring at has stiffenss proerties defined for doef 5 and 6 only, while the spring in end 2 has all 6 degrees of freedom defined. It is possible to combine the spring with "normal" node boundary as demonstrated for Node 1 (has 4 dof's fixed).