The figure below shows a drawing of a 4-mm thick by 20-mm
wide latching spring. A preload is obtained during assembly by
shimming under the bolts to obtain an estimated initial
deflection of 2 mm. The latching operation itself requires an
additional deflection of exactly 4 mm. The material is ground
high-carbon steel, bent then hardened and tempered to a
minimum hardness of 490 BHN. Assume that the yield strength
of the material to be 90 percent of the ultimate strength.
(a) Find the maximum and minimum latching forces.
(b) Determine the fatigue factor of safety for infinite life of the spring assuming that the fatigue failure occurs at 140 mm from the spring end.
