Light Truck Frame Joint Stiffness Study Phase 1 Final Report

FINITE ELEMENT ANALYSIS
Load Applied Here
Figure 8: Close Up Picture of Loading Fixture
Loading Conditions
The three stiffnesses, K x , K y , and K z are the rotations of the crossmember relative to the side rail. K x is
obtained by applying a vertical load (+/- Z) at the end of the crossmember and measuring the rotation
from the vertical deflection of the non-load-bearing bar on the fixture. K y is obtained by applying a
torsional load (+/- Y) along the crossmember and measuring the rotation from the fore/aft deflection of a
bar attached to the base of the fixture. For K z , a fore/aft load (+/- X) is applied at the cross member and
the rotation from the fore/aft deflection of the non-load-bearing bar on the fixture is measured. Each load
was applied at the end of the loading fixture. The fixture was used to increase applied moment, permitting
lower loading forces and measurable deflections during test. The loading was adjusted for each joint so
the peak stress was 200MPa, permitting the maximum deflection without the risk of yielding the joint. The
model was constrained at the two ends of the side rails with rigid spiders to the center of the section. The
center node was then constrained in all six degrees of freedom. The deflections were measured off a
non-load-bearing bar that was attached to the base plate of the loading fixture. This assured that the
deflections measured would be that of the deformed joint, and not include deformation of the fixture.
Report: A/SP-005-1 Light Truck Frame Joint Stiffness Study 14