A composite shaft consisting of two stepped portions having spring constants K₁ and K₂ is held between two rigid supports at the ends. Its equivalent spring constant is
K₁ K₂
(K₁ + K₂)/ 2
(K₁ + K₂)/ K₁ K₂
K₁ K₂/ (K₁ + K₂)
K₁ K₂
(K₁ + K₂)/ 2
(K₁ + K₂)/ K₁ K₂
K₁ K₂/ (K₁ + K₂)