INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN ENGINEERING AND TECHNOLOGY (IJARET)

Transcription

1 INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN ENGINEERING AND TECHNOLOGY (IJARET) ISSN (Print) ISSN (Online) Volume 4, Issue 2 March April 2013, pp IAEME: Journal Impact Factor (2013): (Calculated by GISI) IJARET I A E M E COMPARATIVE STUDY OF SAE 1045 (CARBON STEEL) AND ALUMINIUM ALLOY 7075-T6 FOR LOWER SUSPENSION ARM OF A SEDAN CAR Prof. Pinank A. Patel 1 1 Department of Mechanical Engineering, Marwadi Education Foundations Group of Institutions-Rajkot, India, Vivek G. Patel 2 2 Department of Mechanical Engineering, Marwadi Education Foundations Group of Institutions-Rajkot, India, Dr. Shashikant S. Khandare 3 3 Principal B.D. Collage of Engineering-Wardha, ABSTRACT Automobile parts are subjected to variable amplitude loads; fatigue characteristics vary with material and loading conditions. This research focuses on the finite element based fatigue life prediction of lower suspension arm subjected to numerous loads. Objectives of this analysis are to predict fatigue life of the lower suspension arm using Strain-life approach and to discover suitable material for the suspension arm. The CAD model of lower suspension arm is developed using ProE (Wildfire4.0); later transferred to Ansys 12.1, where finite element analysis for fatigue life analysis was performed employing the Strain-life approach subjected to variable amplitude loading. While performing fatigue analysis, two types of non-uniform variable amplitude loads are considered including zero mean loading (SAEBKT) and positive mean loading (SAETRN). We employed Morrow and SWT Method, wherein tetrahedron mesh is applied to the model for fatigue analysis. Keywords: Fatigue Life, Strain Life Approach, Aluminum Alloy, Non uniformly Varying Load (SAEBKT, SAETRANS) 119

2 I. INTRODUCTION Recent technological research and efforts have focused on new automobile material forms. At present, in automotive industry it is very crucial task to produce lighter; cheaper and more efficient parts can sustain high loads. Every automotive suspensionn is meant for two aims; vehicle control and passenger comfort. A good car suspension system should have satisfactory road holding ability, while providing comfort during riding over bumps and pits on the road. For the prediction of fatigue life stress and strain life approach can be applied, due to presence of stress concentrated area stress life can t give accurate results. For here we employed strain life approach for the prediction of fatigue life of lower suspension arm. II. STRAIN LIFE APPROACH Strain life method is employed where plastic deformation occurs at critical regions (like notches). In this method plastic strain or deformation is directly measured and quantified because Stress life approach fails to account for plastic strain. Even when the component is under heavy loading conditions, it is necessary to have a plastic deformation at stress concentration zone where strain life approach is superior to stress life approach. The local Strain Life approach has gained acceptance as a useful method of evaluating fatigue life of a component. The Strain-Life Curve can be formed by summing up the elastic and plastic strains. Total Strain, ε t = ε e + ε p ε σ' f = (2N f ) + ε' f (2N f ) 2 E The effect of the elastic and plastic components on the strain-life curve is shown in Figure 1. Figure 1 : Strain Life Curve 120

3 σ' f - σ o Morrow s Strain Life Equation: ε a = (2N f ) + ε' f (2N f ) E Smith-Watson-Topper (SWT): σ max ε a E = (σ' f ) (2N f ) + ε' f ε' E (2N f ) III. CAD MODEL, BOUNDARY CONDITION AND MESHED MODEL Figure shows CAD model of lower suspension arm and its bounding box dimensions are mentioned in table. Direction Length Unit X mm Y Mm Z Mm Figure 2 : Cad Model Figure 3 shows the meshed model of lower suspension arm with 2.0 mmm of mesh size and 10node Tetrahedron element (TET10) were considered for the analysis. Figure 3 shows boundary condition applied to the Lower suspension arm. Figure 3 : Meshed Model and Boundary Condition IV. MATERIAL PROPERTIES Fatigue behavior of any material is highly dependent on its tensile strength; higher the tensile strength, material will have high fatigue life. The mechanical properties of C45 & AL 7075-T6 (Aluminum alloy) are shown in Table 121

4 Table 1: Material Properties Properties Unit C45 AL 7075-T6 Strain-Life Parameters Strength Coefficient Pa Strength Exponent Ductility Coefficient Ductility Exponent Cyclic Strength Coefficient Pa Cyclic Strain Hardening Exponent V. LOADING CONDITION The standard ultimate loading cases what we considered are as shown in Table 2. For prediction of fatigue life of lower suspension arm we considered two non-constant varying load SAEBKT (Bracket History) and SAETRANS (Transmission History) as shown in Figure 4&5. Table 2: Loading Condition Conditions X Y Z A Pothole brake limit load B Oblique kerb limit load C Lateral kerb strike limit load Figure 4: Sae Bracket History Figure 5: Sae Transmission History VI. RESULTS From the following results it is being clear that fatigue life of lower suspension arm is considerably increased by employing AL7075-T6 aluminum alloy as a lower suspension arm. Lateral kerb limit is the highest loading condition. 122

5 Figure 6: Lateral kerb strike limit load / Bracket / AL7075-T6 Figure 7: Lateral Kerb Strike Limit Load / Bracket / C45 Figure 8: Lateral kerb strike limit load /Transmission/ AL7075-T6 Figure 9: Lateral kerb strike limit load/transmission/ C Load Cases Pothole brake limit load Oblique kerb limit load Lateral kerb strike limit load Strain Life C45 AL 7075 T6 SAEBKT SAETRANS Bracket Transmission

6 CONCLUSION From the analysis of lower suspension arm it is concluded that if Al alloy (Al T6) will give comparative higher fatigue life then C45. Hence, weight of the component made up from Al Alloy (Al 7075-T6) is subsequently reduced (Approx 60%). REFERENCES [1] Sigmund Kyrre Ås, "Study of fatigue crack initiation in rough surfaces using the finite element method and measured surface topography," Norwegian University of Science and Technology, Trondheim, Norway, [2] N.A. AL-ASADY, A. K. ARIFFIN, M.M. RAHMAN, AND Z. M. NOPIAH S. ABDULLAH, "FEA Based Fatigue Life Assessment of an Automobile Lower," International Conference on APPLIED and THEORETICAL MECHANICS, vol. 4th, 2008 [3] K. Kadirgama, M. M. Noor, M. R. M. Rejab, S. A. Kesulai M. M. Rahman, "Fatigue Life Prediction of Lower Suspension Arm Using Strain-Life Approach," European Journal of Scientific Research, vol. 30, no. 3, pp , [4] M.M. Rahman, K. Kadirgama, M.M. Noor and Rosli A. Bakar Z. Husin, "Prediction of fatigue life on lower suspension arm subjected to variable amplitude loading," in National Conference in Mechanical Engineering Research and Postgraduate Studies, Pahang, Malaysia, 2010, pp [5] S. Abdullah, A. K. Ariffin, S. M. Beden, and M. M. Rahman N. A. Al-Asady, "Fea based durability using strain-life models for different medium carbon steel as fabrication materials for an automotive component," International Journal of Mechanical and Materials Engineering (IJMME), vol. 4, no. 2, pp , [6] Rahman M. M, and Omar R.M Hemin M. M, "Novel Design of Lower Arm Vehicle Using Finite Element Analysis and Statistical Method," Journal of Advanced Science and Engineering Research, vol. 2, pp , March [7] N.A.Al-Asady, A.K. Arrifin, M.M. Rahman S. Abdullah, "A Review on Finite Element Analysis Approaches in Durability Assessment of Automotive Components," Journal of Applied Sciences, no. 8, [8] MOHD KHAIRIL AZIRUL BIN KHAIROLAZAR, "Robust design of lower arm suspension using stochastic," university malaysia pahang, MALAYSIA, [9] Bernd Heißing & Metin Ersoy, Chassis Handbook, ed., Bernd Heißing and Metin Ersoy., Ed. Berlin, Germany: MercedesDruck, [10] ArkanJawdat Abassa, DhaferSadeq Al-Fatal, Experimental And Theoretical Study Of The Influence Of The Addition Of Alumina Powder To 7020 Aluminum Alloy Foam On The Mechanical Behavior Under Impact Loading International Journal of Mechanical Engineering & Technology (IJMET) Volume 3 Issue 3 (September - December 2012) pp , ISSN PRINT : , ISSN ONLINE : Published By IAEME. [11] I.M.Jamadar, S.M.Patil, S.S.Chavan, G.B.Pawar and G.N.Rakate, Thickness Optimization of Inclined Pressure Vessel Using Non Linear Finite Element Analysis Using Design by Analysis Approach International Journal of Mechanical Engineering & Technology (IJMET) Volume 3 Issue 3 (September - December 2012) pp ISSN PRINT: , ISSN ONLINE: Published By IAEME. [12] U. D. Gulhane, M.P.Bhagwat, M.S.Chavan, S.A.Dhatkar And S.U.Mayekar, Investigating The Effect Of Machining Parameters On Surface Roughness Of 6061 Aluminium Alloy In End Milling International Journal of Mechanical Engineering & Technology (IJMET) Volume 4 Issue 2 (March - April 2013) pp , ISSN PRINT: , ISSN ONLINE: Published By IAEME. 124