20. [Ans. 9; 71.8 mm] A semi-elliptical laminated spring is made of 50 mm wide and 3 mm thick plates. The length between the supports is 650 mm and the width of the band is 60 mm. The spring has two full length leaves and five graduated leaves. If the spring carries a central load of 1600 N, find: 1. Maximum stress in full length and graduated leaves for an initial condition of no stress in the leaves. 2. The maximum stress if the initial stress is provided to cause equal stress when loaded. [Ans. 590 MPa ; 390 MPa ; 450 MPa ; 54 mm] 3. The deflection in parts (1) and (2).