Project ForgeMachine Design
Design Against Static Load
GATE 2008
Medium
A compression spring is made of music wire of 2 mm diameter having a shear strength and shear modulus of 800 MPa and 80 GPa respectively. The mean coil diameter is 20 mm, free length is 40 mm, and the number of active coils is 10. If the mean coil diameter is reduced to 10 mm, the stiffness of the spring is approximately
- Adecreased by 8 times
- Bdecreased by 2 times
- Cincreased by 2 times
- increased by 8 times
Explanation
Spring stiffness k=Gd⁴/(8D³N) is inversely proportional to D³. Halving D (20mm→10mm) increases k by a factor of 2³=8.
Source: GATE ME 2008 (2008)
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