Spring Characteristic and Stress of Rectangular Wire Helical Springs with Pitch Angle.

Abstract

A helical spring with rectangular wire cross section can conserve more energy than one with circular wire cross section in a limited amount of space. Therefore, it is used widely in press metal mold and other various machine tools. Recently, the rectangular wire helical spring with large pitch angle is used because of their large amount of deflection from the same free length. Rectangular wire helical springs have also been used as the helper spring in a suspension device for rally cars. Furthermore the rectangular wire helical spring with large pitch angle is attempted to be used as the suspension spring for the automobile. However, the accuracy of the results by Liesecke's theory on the stress and the spring constant of the rectangular wire helical springs has not been made clear, especially on the one with large pitch angle. In this research, the theoretical results are compared with the experimental ones and those by the Finite Element Method (FEM). New design formulae for rectangular wire helical springs considering pitch angle effects are derived for various aspect ratio of wire cross section by the FEM analysis.