Bio-inspired Design of Octafilar, Hexafilar and Quadrifilar Helical Springs

The chameleon's tongue ballistic projection is an example of rapid energy release in the animal realm, which extends at a phenomenal speed and acceleration extending more than six times its length when at rest. Inspired by the rapid projection mechanism, our research examines the biological structure of the chameleon tongue, the regulating principle and its biomechanics to give a comprehensive insight into its geometrical structure. Based on our observations, we concluded that the connective tissue layer that is cylinder-shaped consisting of sheaths that have helically arranged collagen fibre stores elastic energy when the tongue is in a compressed state, and it is the root cause for this projection mechanism. Hence, we have designed three different types of springs, namely octafilar, hexafilar and quadrifilar helical springs, which closely resemble the geometrical arrangements of collagen fibre in the intralingual sheaths of a chameleon's ballistic tongue. So after designing these springs, finite element analysis (FEA) which includes stress, strain, deformation and factor of safety (F.O.S), was performed to confirm the functioning of design, and also, modal analysis was performed to make the spring free of any resonance effect in its operating frequency, the designs which were not safe for application were rejected, and the remaining were compared. Various trends were observed after studying the FEA results by changing the revolution, the number of helical coils and materials, and then comparison was done in order to conclude the best spring design and material for different requirements such as soft or stiff suspension setups.