ABSTRACT
Note that the joint expands more than the bolt does. This will cause an increase in preload. The change in load caused by the differential thermal expansion FT can be found using the equation [2]
(4)
where KB and K1 are the spring rates of the bolt and joint, respectively. The spring rate of a flat washer is negligible. Using the figures for the spring rates and expansions calculated earlier, the increase in preload FT is 1425 lb. This increase is reflected on the joint diagram in Figure 14. Remember that the elastic curve is nonlinear above the preload because the joint begins to yield at 7000 lb.
