On the optimal design of composite material tubular helical springs

A method is presented for the design of helical springs, with particular reference to those made from composite material and having a hollow circular section. Given the technical specifications, (e.g. stiffness, maximum deflection, ...), the method allows to define the spring geometrical and mechanical parameters in order to get the best compromise among spring performances (minimum mass, maximum strength, ...), with constraints on local and global stability, on resonance frequency, ... The method is based on Multi-Objective Programming (a branch of Operations Research), which provides a theoretically correct way for defining the values of many design variables when many objectives (performance indexes) have to be taken into account. Mathematical models are developed for describing the mechanical behaviour of the spring. The models have been validated with satisfactory results. The design solutions coming from the application of the method suggest the best parameter setting for obtaining the desired spring performances.