International Journal of Scientific Research Engineering & Technology (IJSRET)Volume 2 Issue2 pp 103-107 May 2013 www.ijsret.org ISSN 2278 – 0882

IJSRET @ 2013

Design & Analysis of Mono Composite Leaf Spring

R D V Prasad1, R.Sai Srinu2 , P.Venkata rao3

Asst.Prof1, M.Tech Student2, Asst.Prof3

1 Asst.Professor Department of Mechanical Engineering, Bits Vizag, Andhra Pradesh, India.2M.Tech Student of Andhra University, Vizag. Andhra Pradesh, India.

3Asst.Professor Department of Chemical Engineering, Andhra University, Vizag, Andhra Pradesh, India.

ABSTRACTLeaf Spring is a critical load bearing element

that connects wheel to the chasis in an automobileapplication. The Suspension leaf spring of one of thepotential items for weight reduction in automobiles inorder to achieve increased fuel efficiency andimproved ride characteristics. The introduction of fiberreinforced plastics (FRP) made it possible to reduceweight of the product without any reduction in loadcarrying capacity and stiffness. Because of thematerial’s high elastic strain energy storage capacityand high strength-to- weight ratio compared with thoseof the steel, multi leaf springs are being replaced bymono Leaf FRP springs.

This paper deals with development ofanalytical formulation for Composite leaf spring andcomparing the obtained results with the ConventionalSteel leaf spring with 4 leaves. Composite leaf springin this project has been developed as a mono blockconstruction with maximum thickness at the centerwhich is preferably glass fiber reinforced polymer. Thethickness reduces towards the end in order to achieveuniform strength construction. The cross-section isconstant at any section along the spring length. Thiscondition is imposed to accommodate theunidirectional fibers and to maintain the fibercontinuity from one end to the other.

At first we designed a conventional Leafspring with 4 leaves using ANSYS 11 and considereddifferent loading conditions to obtain Stresses andDeflections. The dimensions of an existingconventional steel leaf spring of a light commercialvehicle are taken. Then we created a Solid Model ofComposite leaf spring using CATIA V5 and imposeddifferent loading conditions.

Key words – leaf spring, ERP springs, glass fiberreinforced polymer.

I. INTRODUCTION

A spring is an elastic body whose function is to distortwhen loaded and to recover its original shape when theload is removed. Though there are many types ofsprings, the following, according to their shape areimportant. The various applications of springs are tocushion, absorb or control energy due to either shockor vibration, as in car springs, railway buffers, aircraftlanding gears and vibration dampers. To apply forces,as in spring-loaded valves and spring balances. Tocontrol motion by maintaining contact between twoelements as in cams and followers. To measure forcesas in engine indicators and spring balances. To storeenergy as in watches and toys.

II. LITERATURE SURVEY

JOHN E.MUTZNER and DAVIDS.RICHARD[1] told in their paper titled“Development And Testing Of Composite TruckTrailer Spring” that, composite leaf spring constructedof glass fiber reinforced polymeric material have beenrecognized as a variable replacement for steel leafsprings since their introduction on the 1981 generalmotors covette. This acceptance of composite leafsprings has given rise to applications in high volumeproduction passenger cars and utility of composite leafspring is clearly demonstrated in these applications.This paper will discuss the design, laboratory testing,field testing, and development over the past three yearsthat has led to the commercialization of the liteflextrailer springs. This will include the design process forhigh and low deflection composite leaf spring andstress analysis for common springs used in variousaxle spacing worldwide. An explanation of laboratorytest will be given and the rationalization for these testcompared to steel spring test standards. An attemptwill be made to correlate laboratory test tracks, servohydraulic simulator and field tests of liteflex trailer

International Journal of Scientific Research Engineering & Technology (IJSRET)Volume 2 Issue2 pp 103-107 May 2013 www.ijsret.org ISSN 2278 – 0882

IJSRET @ 2013

springs. This testing will demonstrate the soft failuremode if the composite leaf spring and the advantagethis brings to fleet owners. The other advantage ofweight reduction and increased durability will bediscussed.

KIKUA TANABE, TAKASHI SEINO[2] ofCentral Engineering Laboratories, Nissan Motors co.,ltd. Yokosuka, Japan in their paper titled“Characteristics Of Carbon/Glass Fiber ReinforcedPlastic Leaf Spring” designed and fabricated andevaluated a tapered leaf spring made of carbon fiberreinforced plastics. To construct the leaf spring, acarbon/glass fiber hybrid lamination is selected. Thisselection was made in concentration of chippingresistance, impact resistance and fatigue resistance.They constructed a prototype of leaf spring whichweighed approximately 2kg included the front and rearsteel eyes. In comparison with the steel spring, thisrepresents a weight reduction of 76%. Prototype areput through a series of evaluations both on the benchand on the vehicle. As a result, the leaf spring provedto be better than the steel in such practical performancearea as car handling and riding quality and endurance.

III MODELLING OF FRP LEAF SPRING

We have designed a solid leaf spring with allrequired dimensions as we calculated earlier. Wedesigned this solid leaf Spring using CATIA V5Software.

FIG1. CATIA MODEL OF FRP LEAF SPRING

3.1 ANALYSIS OF FRP LEAF SPRING.

The element used is SOLID 45(3-D four nodetetrahedral structural solid with rotations).

Solid 45 is well suited to model irregularmeshes (such as produced from various CAD/CAMsystems). The element is defined by four nodes havingsix degrees of freedom at each node; translations in thenodal x, y, z directions and rotations about the nodal x,y and z directions. The element also has the stressstiffening capability. The SOLID 45 element can oftenbe used in place of the SOLID 92 element to reducethe wave front and solution time.

IV. NOMENCLATURE

R- Radius of curvature of ArcM- Bending Moment acting at that pointI- Moment of Inertia of spring section at the pointy- Distance of extreme fiber from Neutral axisfb- Bending Stressb- WidthP- Static load per wheelW- Laden weight of the vehicldb- Bolt diameter

4.1 SPECIFICATIONS (passenger vehicle):Laden load - 14 tonesNumber of springs supporting the load - 4Span of the spring - 1000mmNumber of leaves - 4Permissible deflection - 85mm

Table 1 Mechanical properties of N155 & Inconel718

SL.No Properties Value1 Tensile Modulus along X-

direction Ex, MPa34300

2 Tensile Strength of thematerial, MPa

900

3 Compressive Strength ofthe material, MPa

450

4 Mass density of thematerial, kg/mm3

2.6x10-6

5 Flexural Modulus of theMaterial, MPa

40000

6 Flexural Strength of theMaterial, MPa

1200

V. RESULTS AND DISCUSSION

International Journal of Scientific Research Engineering & Technology (IJSRET)Volume 2 Issue2 pp 103-107 May 2013 www.ijsret.org ISSN 2278 – 0882

IJSRET @ 2013

FIG2 NODAL DELECTION IN Z-DIRECTION FORFRP LEAF SPRING

FIG3 VON MISES STRESSES FOR FRP LEAFSPRING

FIG 4 PRINCIPAL STRESS

FIG5 PRINCIPAL STRESS 2

FIG 6 PRINCIPAL STRESS 3RESULTS: STEEL LEAF SPRING

FIG 7 NODAL DELECTION IN Y-DIRECTION INSTEEL LEAF SPRING

International Journal of Scientific Research Engineering & Technology (IJSRET)Volume 2 Issue2 pp 103-107 May 2013 www.ijsret.org ISSN 2278 – 0882

IJSRET @ 2013

FIG 8 STRESS IN THE STEEL LEAF SPRING

VI DISCUSSIONS

FRP leaf spring was designed in this work as amono leaf constant cross-section area varyingdepth with fibers oriented in axial direction. Thestiffness of the leaf spring must be so controlledthat spring deflects to specified values during thebump ride so that shock will not be transmitted tothe vehicle body. The leaf spring should haverequired fatigue strength to withstand the repeatedloads arising due to bumpy ride.

In this project, a procedure for designing amono leaf composite leaf spring is formulatedconsidering the constant cross section area. Thethickness and width at various sections arecalculated. Mono leaf FRP leaf spring is designedaccording to the given specifications for a truck.The three cases taken for calculating maximumload are:Case 1: vehicle passing over a bump whilebraking.Case 2: vehicle passing over a bump whileaccelerating.Case 3: vehicle passing over a bump whilecornering.

The designed FRP leaf spring is modeled inCATIA V5.

Finite Element Analysis has been done in thecreated FRP model, for the maximum load of107394N. Here we used SOLID 45 element for theFRP leaf spring. First the leaf is meshed, boundaryconditions are applied by arresting all the degreesof freedom in the eyes. Loads are applied in the

bottom part of the leaf spring. In the postprocessing, the results are viewed. Graphicaldisplay of displacement and stresses are shown inchapter 7. The main criteria of the design areobtained, but the structure is safe.

The maximum deflection and maximum stressare found and it is shown in figures.

Table 1 Maximum Deflection for FRP SpringS.No Load, N Ux, mm Uy,

mmUz,mm

1 107394 0.1153 1.2 11.0472 98406 0.1038 1.097 10.1223 98800 0.1054 1.102 10.1624 34300 0.03614 0.3831 3.52

Table 2 Maximum Stress for FRP Spring

Which are within the allowable limit.Steel leafspring is designed and modeled in ANSYS for thegiven specifications. Finite Element Analysis istaken out in ANSYS using the element BEAM 4for the maximum load condition with sameboundary conditions. In the post processing resultsare viewed and displayed in chapter 7.

Table 3 Maximum Deflection for Steel SpringS.No Load,

NUx,mm

Uy,mm

TheoreticalDeflection

1 107394 1.262 9.65 15.532 98406 1.156 8.843 14.233 98800 1.161 8.878 14.294 34300 0.4029 3.082 4.96

Table 4 Maximum Stress for Steel SpringS.No Load, N Line

StressN/mm2

TheoreticalStress

1 107394 1247 1242.912 98406 1114 1138.953 98800 1120 1143.514 34300 402.86 396.98

International Journal of Scientific Research Engineering & Technology (IJSRET)Volume 2 Issue2 pp 103-107 May 2013 www.ijsret.org ISSN 2278 – 0882

IJSRET @ 2013

Fig 8 Load Vs Deflection Graph

Fig 9 Load Vs Stress Graph

Both the FRP and steel leaf spring are designed andmodeled and results are compared:Weight of steel leaf spring = 347kgWeight of FRP leaf spring = 196kgAmount of weight saving = 43.5%Max. stress in steel leaf spring= 1247N/mm².Max. stress in FRP leaf spring= 158.23N/mm².

VII CONCLUSION & FUTURE SCOPE

A procedure to design a composite leaf springhas been established. Leaf spring made up of E-Glass/Epoxy multi layered composites has beendesigned. FRP and steel models are created in ANSYS.The Finite Element Modeling presented in the analysisis able to predict the stress distribution.

When maximum load is applied on the steel leafspring, the maximum stress is greater than that of FRPleaf spring. Even under the maximum load, themaximum stress in the FRP is within the allowable

limit. The weight reduction has greater influence innoise and vibration characteristics. Glass fibers are formanufacturing instead of carbon due to low cost. Theresults are encouraging and suggest that ANSYS canbe used effectively and efficiently in other complexand realistic designs often encountered in engineeringapplications, where experimental is not possible due toshortage of time and other constraints.

VIII REFERENCE

1. W.G.GOTTENBERG and K.H.L.O IN THE 38th

Annual Conference, Reinforced Plastics/CompositeInstitute, The society of Plastics Industry, inc.February 7-11, 1983 titled Glass Fiber ReinforcedEpoxy Leaf Spring Design.

2. JOHN E. MUTZNER and DAVID S.RICHARDtitled “Development and Testing of Composite TruckTrailer Leaf Spring”.

3. Concepts and applications of Finite ElementMethods― ROBERT D.COCK

4. Introduction to Finite Element Methods―TIRUPATHI CHANDRUPATLAASHOK D.BELEGUNDU

5. User Hand Book of ANSYS.

6. Introduction to Composite Material―AUTARK.KAW