Example of Using Splines
Overview
In this example, we use a spline to relate the force of a spring to its deformation. The values in Table 1 show the relation of a force in a spring to its deformation.
When the deflection is: | The force is: |
|---|---|
-0.33 | -38.5 |
-0.17 | -27.1 |
-0.09 | -15.0 |
0.0 | 0.0 |
0.10 | 10.0 |
0.25 | 30.0 |
0.40 | 43.5 |
0.70 | 67.4 |
Using this table, you can determine the force when deflection equals -0.33, and the force when deflection equals -0.17. You cannot, however, determine the force when the deflection is -0.25. To determine the force at any deflection value, Adams View creates a continuous function that relates deflection and force. The continuous approximation is then used to evaluate the value of the spring force at a deflection of -0.25. If you input two sets of values (x and y) using a spline data element, you can define the curve that the data represents.
You would then use the spline data element in a function or subroutine that uses cubic spline functions to fit a curve to the values. The curve allows Adams View to interpolate a value of y for any value of x.
Procedure
Briefly, the steps that you’d perform to use the spline data element to define the force deflections are:
1. Create the spline using the spline editor or the general method.
2. Build a simple nonlinear spring-damper, and then modify it to use the spline. To use the spline in the spring-damper definition, under Stiffness and Damping in the Spring-Damper Modify dialog box, change the stiffness coefficient to Spline: F=f(defo). Adams View builds a function expression for you, using AKISPL and modeled spring length as free length.
Note: | You can also use a single- or multi-component force to define the force deflections. In this case, you would select Custom as you create the force, and then modify the force by entering a function expression, such as:  |
You can use the Function Builder for assistance in building the expression.