National Conference onAdvances in Mechanical Engineering 2011.03 - 05January, 2011

Finite element analysis and testing of suspension arm

ABSTRACT- Think of av chick without suspension Does itseem feasible??? Absolutely not. So suspension system is must foranyvehicle. The firstessential prerequisite for suspension systems"is suspension system parts. This paper deals with the finiteelementanalysis for MacPherson type suspension systems lower controlann (LCA) of the 4 wheeler suspension .system· The main function In .automotive suspension,. a control arm (sometfl!les· ... '

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::7cl~~icj~lS$i1!:r~t'ti~~~7:~:g~!~)~~~4I~1iI:r,?~!~1~4In this project' we firstdone CAD modeling using NX Unigraphics suspension', while one control arm per wheel makes up athe finite element modelling of the LCA using AltairH yperworks part, usually the lower part, of McPherson strut suspensionsoftware. Then we calculated various dynamic Loadsin pothole. or of various other configurations.bump, kerb strike, braking, cornering and acceleration load casesusing MSC ADAMS. Whilec a1culating loadsi n MSC ADA1v1Stypical front axle and rear axle weight is considered By applyingall this forces in X, Y and Z directions performed a linearstaticanalysis using MSCNastran SOLtOI solution sequence.

Chandrakant M. Chaudhari.Student M. E. ( CAD/CAM), Mechanical EngineeringDepartment, Bharati Vidyapeeth University's C. O. E.,Pune, lndia- 411 043cmchaudhari@gmail.com

The main significance of the analysis is to check thcs tructuralstrength of the LeA using dynamic forces. It will save the cost oftesting and validating thee ach design physically. Validating thefinal finite element analysis results, through the physical testing ofthe component.

The first main aim behind this analysisi s to show the power offinite element analysis. Because it will saves lot of cost, as everyvehicle having 3·4 stages as Prote-I, Alpha, Gamma, Betaa ndFinal product. By believing on the results of finite elementanalysisc ompany can skip the one or two stages between Prot-land Final product. This paper will show thev alidation of finiteelement analysis resultswith actual physical testing.

KEYWORDS· Suspension system, suspension arm, lowercontrol arm, static and dynamic FEA analysis.

INTRODUCTION

Suspension is the term given to the system of springs,shock absorbers and linkages that connects a vehicle to itswheels. Suspension systems serve a dual purpose -contributing to the car's[5] handling and braking for goodactive safety and driving pleasure, and keeping veh icleoccupants comfortable and reasonably well isolated fromroad noise, bumps, and vibrations. These goals are generallyat odds, so the tuning of suspensions involves finding the

Dr. M V. SulakheProfessor, Production Engineering Department,Bharati Vidyapeeth University'S C. O.E .,Pune, India- 411 043

right compromise. The suspension also protects the vehicleitselfand any cargo or luggage from damage and wear. Thedesign of front and rear suspension of a car may bedifferent.

Suspension is the term given to the system of springs,shock absorbers and linkages that connects a vehicle to itswheels. Suspension systems serve a dual purpose -contributing to the car's handling and braking for goodactive safety and driving pleasure, and keeping vehicleoccupants com fortable and reasonably well isolated fromroad noise, bumps, and vibrations. These goals are generallyat odds, so the tuning of suspensions involves finding theright compromise. The suspension also protects the vehicleitself and any cargo or luggage from damage and wear. Thedesign of front and rear suspension of a car may bedifferent.

AI ower control arm suspension is an automobilesuspension design in which one or more arms (or "links")are connected between (and perpendicular to and forwardof) the axle and the chassis. It is usually used on rear axles.A'ieading arm' as used on a CAR, has an arm connectedbetween (and perpendicular to, and to the rear of) the axleand the chassis. It is used on the front axle.

Trailing-arm designs in live axles etups often usej usttwo or three links Panhard rod. A trailing arm design canalso be used in an independent suspension arrangement.Each wheel hub is located only by a large, roughlytriangular arm that pivots at one point, ahead of the wheel.Seen from the side, this arm is roughly parallel to theground, with the angle changing based on roadirregularities. A semi-trailing arm suspension is anindependent rear suspension system for automobiles ill

Department of Mechanical & Manufacturing Engineering, !vUT Manipal

National Conference on Advances in Mechanical Engineering 2011,03 - 05 January, 2011

which each wheel hub is located only by a large, roughlytriangular arm that pivots at two points. Viewed from thetop, the line formed by the two pivots is somewherebetween paral Ie! and perpendicular to the car's longitudinalaxis; it is generally parallel to the ground. Trailing-arm anomuliilink suspension designs are much more commonlyused for the rear wheels of a vehicle where they can allowfor a Ilatter !1UUI and more cargo room. Many small vehiclesfeature a McPherson strut front suspension and trailing-armrear axle.

I. What does suspension do?Apart from your car's tyresa nd seats, the suspension is

_. the prime mechanism that separatesyour bum{arse for_the _.. _._~_ American) .Jro(n·.~lh~f--=:oad:-::lt·aiSQ-:-_QE~¥enls-YOltr Cclf from _.-: . "_."-~4_ ~ . ..; - . • __" ~.

-:~,;~f;W~J~~~~~Ji~i~~~~I!~I~I~~~~~i~~~~t~so harsh. Actually it's harsh because underground trains ~,.-~... -- - >".,. ..", -

have no lateral suspension to speak of. So as the railsdeviate side-to-side sl ightly, so does the entire train, and it'spassengers. In a car, the rubber in your tyre helps with thislittle problem.! n it's most Suspension types. Figure 1: The Ideal Analysis Process flowchart

FINITE ELEi\IENT ANALYSIS

FEA involves the solution of simultaneous,algebraic equations. The algebraic equation result fromsubdividing a( I )[3J complex shape into many discrete,interconnected, simple shapes hence the phrase 'finiteelements'. Many resources exist on finitee \ement theory,including Zienkiewicz (1977) and Cook, Malleus and Plesha(1989). Un fortunately. few guides to practical approaches tofinite element modeling and analysis are available.Finite elements allow us to simulate a wide variety ofphysical phenomena, encompassing mechanical, electricaland even chem ical circumstances. Mechanical simulationrepresents the majority of FEA usage.

The Process of Analysis

In the scope of product design, analysis fits intonearly all design phases. The following represents asimplified design cycle and a guideline of when analysiscould be useful.

On a more detailed level. the analysis process can vary fromthe ideal process, which is long and thorough, to seat-of-the-pants, single iteration analysis.

Techniquevalidation

The ideal analysis consists of two phases, atechnique validation phase and an optimization phase. Thetechn ique validation phase ver ifies that the 1ll1J<.L:ii,;,;techniques and assumptions are corr ectf or the problem. Forinstance, during this phase, one could determine and refinethe FEA technique from a static linear analysis to a time-dependent, large deflection method due to extremedeformation, high strains and impact loading. Experiencewill reduce the duration and number of iterations of thisphase. Additionally, the physical testing may require carefulrefinement to ~epresent actual operating conditions.

The optimization phase simply establishes abaseline, and iterates on design changes until it meetst hespecified design criteria.

Although it should be a goal, the full analysisprocess may not be realistic for many design cycles. Manytimes the techniquev alidation phasei s skipped. This canaffect the confidence of a particular solution, thus affectingthe test requiranents and factors of safety. Additionally,multiple iterations are not timely enough for someschedules. What is left is a single iteration analysis with novalidation and DO reference point. This can be dangerous,buti t is better to performo ne analysis than none.Ultimately, each omission of the ideal FE analysis cycleresults in lost confidence.

Deportment of Mechanical & Manufacluring Engineering, Ml T Manipal

National Conference on Advances in Mechanical Engineering 2011,0 3 - 05 January, 201J

STATIC LOAD ANALYSIS OF SUSPENSION ARM

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Figure 2- General suspension arrangement

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Figure 3- Free body diagram-l

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Figure 6: Calculations for free body diagram-l

Department of Mechanical & Manufacturing Engineering, M1T Manipal

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National Conference on Advances in Mechanical Engineering 2011,03 - 05January, 2011

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Figur'e 8- Free body diagram-S

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As per FEA for static analysis purpose forces and knO\\TI andunknownv ariables are calculated from above shownf reebody diagrams.[5J[3)

STATIC LOAD ANALYSIS OF SliSPENSION ARi'1

From CAD model by using AL rAIR l lyperworksllyperrnesh(6) software FE model prepared for the lowercontrol arm assembly ass hown below. Aller that dynamicloads arc calculated from l\ISC :\[)A1'-lSs oftwar e andconverted them into static loads for static FE .ualysis

.t~purpose_ Various load cases such as front RHbump, both

wheel bump, Braking, cornering and acceleration areconsidered for analysis purpose,

Figure 10- Free body diagram-S

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Figure 11- vonMises Stress plot for both bump load case

Maximum vonMises stress is plotted in above figure, ShOVV11

location having maximum stresses in the part,

VALIDATION OF FE RESULTS THROUGH TEST

Departrnent of Mechanical & Manufacturing Engineering, M1TManipal

Figure 12- Test setup

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National Conference onAdvances inMechanical Engineering 201 J, 0 3 - 05January, 2011

Above figure shows the typical test setup for the same bothbump load case. At high stress location strain gauging donewith the help of modem instrumentation techniques. Theresults of finite element. analysis and actual testing arematching.[5) The acceptance of the material is 160 MPa asyield point strength and 270 MPa as-tensile strength. Thefinite. element analysiss tresses are above the yield andabove the tensile strength of the material. Becauseo f thatduring testing crack propagation started and part broken atsame location. As shown in below figure.

.•..-...--.----Figure 13 : Actual tested sample

Figure 14 : FE analysis result for botb' bump load case

CONCLUSION

The suspension system in any vehicle plays important rolein riders comfort. Presentlv we are workinz onmodifications in the same desig;;. The validation shO\~s theaccuracy off inite element analysis with actual testing. Theproper co re lati on shown in th is paper..

The main aspects will be under consideration arecost, comfort and a compact design. Testing of all designsas per the IS norms. Co-relation of various analysis resultswith actual test results.

ACKNO\VL£DGM£NT

J wish to express my deep sense of gratitudetowards Or. M. V. Sulakhe for his valuable guidance,untiring devotion, support and encouragement throughoutthe paper work, "FE Analysis and testing of suspensionAnn". His valuable advice and suggestion have been ofimmense at every stage of m y project work.

I also express my deep gratitude & thanks toProf. N. S. Shr eenivasan, H.O.D. Mechanical EngineeringDepartment for his continuous guidance for the paper work.I even thankful to all staff members, our friends and otherpersonalities who had helped me directly and indirectly.

REfEH E_'~CES

[I J P Seshu, "Textbook of Finite EJementA nalysrs"

[2J Rober Westfield, "Suspension .. A. Novel(P S)"

[3J [l.1SC NASTR .:\N User manual

[4\ Robert D Cook, "Finne Element l\lodding for Stress Analysis"

[51 Terry L. Satchell· Pontia cM ot.or Div. Genera! l\lotors Corp "Thedesign of trai ling arm axle", S,.\ E international paper, 198 I

[6J . Alta~r Hyperworks user m~nu"l

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Department oj Mechanical & Manufact uri ng Engineering, ivflT iYftnipa/