Optimal Design Of Fatigue Loaded Heavy-duty
Machine Spring Elements
Author(s)
H. Martikka & I. Pöllänen
Abstract
The aim of this paper is to present results of using fundamental machine element
design principles into re-designing optimally heavy-duty springs used in terrain
machinery and in industry. The use of standard procedures often results in
recurrent fatigue fracture failures. This reveals the need for optimal innovative
design principles which are not found in standards. Analytical calculations reveal
the main causes of failures to be the local bending due to eccentric highly impact
force application at squared and ground ends and wearing away of the shot
peening protection. Optimum design is used to solve the problem by finding the
optimal spring. Goals are minimisation of wire volume, space restriction, desired
spring rate, avoidance of surging and achieving reliably long fatigue life.
Available fatigue dimensioning methods are used with amplitude-mean stress
diagrams and S-N curve approaches. Conclusions are supported by using full 3D
solid FEM analysis by which the stresses, strains, deformations and natural
frequencies and modes are obtained. Then FEM is used to optimally fine tune
and validate the best result.
Keywords: industrial optimisation, helical springs, fatigue.
1 Introduction
Background for this study is observation that conventionally designed helical
springs did not have the expected long lifetime. Analyses of many case studies
have gives gave clue that a additional effects contributed strongly, Among these
are the highly impacting bending and torsional stress peaks due to non
symmetric pressure application at ground spring ends. The conventional
standards of dimensioning do not take these effects into account.
Keywords
industrial optimisation, helical springs, fatigue.
Related Book
Other papers in this volume
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