Question 5: A semi-elliptic leaf spring (Figure a) is to be designed for infinite life when subjected to a design overload (applied at the center) that varies between 2000 and 10,000 N. The spring rate is to be 50 N/mm. The material is to be shot-peened, 5-mm-thick steel having the strength characteristics represented in Figure b (proper load, F F=1000 to 5000 N, 1.3F size, and surface are reflected in the given curve). Five leaves are to be used. A central bolt, used to hold the leaves together, causes a fatigue stress concentration factor of 2. Using the equations in this section, estimate the required overall spring length, and the width of each leaf.
(a)
800
a=0.52
life bending
MPa)
Design overload point
a=555
1Su 1600
0
400
800 m(MPa)
1200
(q