Spring definition
- @SPRING_DEFINITION {
- @SPRING_NAME {SpringName} {
- @FUNCTION_1D_TYPE {Fun1DType}
- @FUNCTION_1D_NAME {Fun1DName}
- @FUNCTION_1D_NAME {Fun1DNameDeriv}
- @INITIAL_STRETCH {Δ_{i}}
- @COMMENTS {CommentText}
- }
- }
Introduction
A spring defines the nonlinear relationship between the force and stretch of an elastic spring. Two types of springs can be defined.
- Rectilinear springs define the relationship between the spring elastic force, F^{el}, and stretch, Δ. Rectilinear springs are used with relative displacement elements or are part of a more complex elastomeric device model.
- Torsional springs define the relationship between the spring elastic moment, M^{el}, and rotation, φ. Torsional springs are used with relative rotation elements or are part of a more complex elastomeric device model.
NOTES
- Parameter Fun1DType defines the nature of the spring. It can take either of two values.
- Fun1DType = RECTILINEAR_SPRING defines a rectilinear spring, and
- Fun1DType = TORSIONAL_SPRING defines a torsional spring.
- The characteristics of the spring are defined by 1D function, Fun1DName, F = F(x), which maps to F^{el} = F^{el}(Δ) and M^{el} = M^{el}(φ) for the rectilinear and torsional springs, respectively. The 1D function can be a Chebyshev function, a harmonic function, a tabulated function, or a user function. For tabulated functions, the discrete function must approximated by its expansion in terms of Chebyshev polynomials.
- It will also be required to compute the derivative of the spring force or moment with respect to the stretch or rotation, respectively. If the 1D function is defined as a Chebyshev, harmonic, or tabulated function, this derivative is computed analytically and a 1D function associated with this derivative will be generated automatically. If the 1D function is defined as a user function, this derivative must be provided as an independent user function, Fun1DNameDeriv. In this case, both Fun1DName and Fun1DNameDeriv must refer to user functions.
- If an initial stretch, Δ_{i}, of the spring is defined, the elastic force in the spring is computed with the total stretch s + Δ_{i}.
- It is possible to attach comments to the definition of the object; these comments have no effect on its definition.