Improved stiffness model for helical compression springs with variable pitch
Modèle de raideur amélioré pour les ressorts de compression hélicoïdaux à pas variable
Résumé
Helical springs with variable pitch are commonly used for their nonlinear load/length relation. The standard equations defining the stiffness of cylindrical helical spring with evolving pitch use the same equations as for multiple constant pitch springs in series. However, recent studies highlighted the simplification hypotheses in the standard equations create error in evaluating the stiffness of those springs. The objective of this study is therefore to create a new stiffness model for guided springs with two active parts and parallel ends, based on the model of Cadet, originally created for constant pitch springs. After updating the analytical model to fit the variable pitch spring behavior, it is tested and compared with experimental and numerical data. As a result, the presented analytical model is always successfully superimposed on the numerical or experimental data, while the standard equation always overestimates the stiffness of the spring. This new analytical tool saves both significant computing time compared to numerical model while being as accurate and raw material during production by already giving the right geometry to satisfy the specifications.