“…Thus, Scowen and Hughes [2] introduced the 'sulcated spring' and was proved to be a very promising concept in non-linear spring response. Closed-form solutions of the diametrical, in-plane bendingshear and bending-torsional stiffnesses of mid-surface symmetry composite circular springs were derived by Tse et al [6] and verified by experiments. An analytical study using the energy method was followed by Akasaka et al [4] to evaluate the spring constants of elliptic composite springs.…”