Adams Car Package > Shared Material > Appendix > Preload

Preload

The spring force definition depends on the type of spring and the installation method. Springs may be defined as either linear or nonlinear, and the installation methods vary accordingly.

dmCalc is the distance magnitude between the I and the J coordinates at the design configuration.

For a linear spring:

Spring Force = k * (DM(I,J) - OffsetCalc) + Preload

There are two installation methods, and OffsetCalc depends on which is chosen:

■Preload

♦Preload = user specified force

♦OffsetCalc = dmCalc

■Installed Length

■Preload = 0.0

■Installed_Length = user specified length

■OffsetCalc = Free_Length - Installed_Length + dmCalc

For a nonlinear spring:

For nonlinear springs, the force in your template-based product is expressed using Akima spline interpolation of force versus spring deflection or spring length. Because the distance between the I and J coordinate references differs from the installed length, your template-based product calculates an offset distance to use in the force equation:

■Force vs. deflection (TeimOrbit and XML property files)

■Spring Force = AKISPL(OffsetCalc - DM(I, J), 0, Spline)

■OffsetCalc = Free_Length - Installed_Length + dmCalc

■Force vs. length (XML property files only)

■Spring Force = AKISPL(OffsetCalc + DM(I, J), 0, Spline)

■OffsetCalc = Installed_Length - dmCalc

There are three installation methods, and OffsetCalc depends on which is chosen:

■Preload

■Installed_Length = calculated by interpolating the Spline

■Installed Length

■Installed_Length = user specified length

■Use Hardpoints

■Installed_Length = dmCalc