Fatigue life prediction: A comparative study for a three layer EN45A parabolic leaf spring

There are literally several studies accomplished to predict the fatigue life of leaf springs but estimation of fatigue life of a parabolic leaf spring by using CAE tools has not yet been executed in the past. Parabolic spring is an important component in a vehicle suspension system.
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Fatigue life prediction: A comparative study for a three layer EN45A parabolic leaf spring Engineering Solid Mechanics 3 (2015) 157-166 Contents lists available at GrowingScience Engineering Solid Mechanics homepage: www.GrowingScience.com/esmFatigue life prediction: A comparative study for a three layer EN45A parabolic leafspringKrishan Kumar* and M. L. AggarwalAssistant Professor, Mechanical Deptt., YMCA University of Science & Technology, (A Haryana State Govt. University), Faridabad, Haryana, IndiaARTICLE INFO ABSTRACT Article history: There are literally several studies accomplished to predict the fatigue life of leaf springs but Received 6 January, 2015 estimation of fatigue life of a parabolic leaf spring by using CAE tools has not yet been Accepted 10 May 2015 executed in the past. Parabolic spring is an important component in a vehicle suspension Available online system. It needs to have excellent fatigue life and in today’s scenario manufacturers rely on 12 May 2015 Keywords: constant loading fatigue analysis. The objective of this work is to perform the fatigue analysis Parabolic leaf spring of parabolic leaf spring by three different methods where CAE analysis is performed to observe Fatigue life the distribution of stress fatigue life and damage using Goodman approach. In this work, fatigue CAE analysis life of the parabolic leaf spring is determined as per SAE spring design manual and experimentally by testing on full scale fatigue testing machine. ANSYS is used for CAE solution for the prediction of leaf springs fatigue life considering stress theory. The fatigue life estimated by all three modes is then compared for the purpose of validation. The methodology used in this paper brings a practical approach to the professionals in the industries who are engaged for design of mechanical components. © 2015 Growing Science Ltd. All rights reserved.1. Introduction A spring is an elastic devise used to store mechanical energy, usually made out of hardened steel.Parabolic leaf spring is one of essential components in vehicle suspension system, which is commonlyused in many heavy vehicles. It requires to have an excellent static load bearing capacity as well asfatigue life. Large vehicles require a good suspension system that can deliver a good ride and handling.The leaf spring is required to absorb the vertical vibrations due to road irregularities based on variationsin the spring deflection to store the potential energy in spring as strain energy and to release slowly.Fatigue failure is one of the major issues in automotive components because at fluctuating stresses thevehicle structure may fail before achieving the failure stress of that material. That is why it is necessaryto withstand numerous numbers of cycles before failure or never fail at all during the service period.This study is based on a numerical technique called the finite element method (FEM). Using FEA, the* Corresponding author. Tel: +919896596710E-mail addresses: er.krishanverma@yahoo.com (K. Kumar)© 2015 Growing Science Ltd. All rights reserved.doi: 10.5267/j.esm.2015.5.003158parabolic leaf spring as shown in Fig.1 is modeled using the discrete building blocks called elements.Each element has some equations that describe how it responds to certain loads. The sum of theresponse of all the elements in the model gives the total response of the design. Fig.1: Parabolic Leaf Spring Assembly Aggarwal and Chawla (2007) explained that fretting fatigue between leaves can be reduced bycareful control of shot peening parameters. The bending strength of EN45A parabolic leaf spring isdetermined to be higher as compared with semi-elliptic leaf spring. Aggarwal et al. (2006 a) calculatedaxial fatigue strength of EN45A spring steel specimen experimentally as a function of shot peening inthe conditions applied for full-scale leaf springs testing in industries. Optimum shot peening conditionfor specimen has been determined to correlate with S/N curves of leaf springs. A mathematical modelhas been developed to forecast the fatigue life of leaf springs for a given stress at varying shot peeningconditions. Predictions from this model are compared with experimental data. Aggarwal et al. (2006 b)identified the effect of shot flowrate on surface roughness. Full-scale laboratory testing of EN45Aspring steel leaf springs was carried out to present improvement in fatigue life due to shot peening.Double shot peening was performed on leaf springs and its effects on surface roughness, compressiveresidual stress field, and fretting fatigue were noted. Aggarwal et al. (2005) evaluated axial fatiguestrength of EN45A spring steel, experimentally. The effect of almen intensity on compressive residualstress has been discussed for fatigue life extension. Shot peening of leaf spring was illustrated to causeimprovement in fatigue strength, reduction in weight and reliability. Agg ...