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Q8) A diesel engine exhaust valve is controlled by two concentric springs. The outer spring is made from 20 mm diameter wire with 10 active coils, a free length of 360 mm and a mean diameter of 254 mm. The inner spring is made from 16 mm diameter wire with 12 active coils, a free length of 380 mm and a mean diameter of 178 mm. When the exhaust valve is shut, the length of both springs is 320 mm.

The travel of the valve from shut to open is 38 mm.

Calculate EACH of the following:

a) the work done to fully open the exhaust valve; (10)

b) the increase in strain energy to fully open the exhaust valve. (6)

Note:

Modulus of Rigidity for both springs =80 GN/m².