International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –

6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME

119

COMPARATIVE STUDY OF SAE 1045 (CARBON STEEL) AND

ALUMINIUM ALLOY 7075-T6 FOR LOWER SUSPENSION ARM OF

A SEDAN CAR

Prof. Pinank A. Patel1

1Department of Mechanical Engineering, Marwadi Education Foundations’ Group of Institutions-Rajkot, India,

Vivek G. Patel2

2Department of Mechanical Engineering, Marwadi Education Foundations’ Group of Institutions-Rajkot, India,

Dr. Shashikant S. Khandare

3

3Principal 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)

INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN

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ISSN 0976 - 6480 (Print) ISSN 0976 - 6499 (Online) Volume 4, Issue 2 March – April 2013, pp. 119-124 © IAEME: www.iaeme.com/ijaret.asp Journal Impact Factor (2013): 5.8376 (Calculated by GISI) www.jifactor.com

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International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976

6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March

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 suspension 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

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, εt = εe + εp

The effect of the elastic and plastic components on the strain

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976

6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME

120

Recent technological research and efforts have focused on new automobile material automotive industry it is very crucial task to produce lighter; cheaper

parts can sustain high loads. Every automotive suspension 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

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.

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

h 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

fe approach has gained acceptance as a useful method of evaluating fatigue life of a

can be formed by summing up the elastic and plastic strains.

∇ε σ'f

= (2Nf) + ε'f (2Nf)

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

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –

April (2013), © IAEME

Recent technological research and efforts have focused on new automobile material automotive industry it is very crucial task to produce lighter; cheaper

parts can sustain high loads. Every automotive suspension 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

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

of lower suspension arm.

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

h 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

fe approach has gained acceptance as a useful method of evaluating fatigue life of a

can be formed by summing up the elastic and plastic strains.

life curve is shown in Figure 1.

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976

6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March

Morrow’s Strain Life Equation:

Smith-Watson-Topper (SWT):

III. CAD MODEL, BOUNDARY

Figure shows CAD model of lower suspension arm and its bounding box dimensions

are mentioned in table.

Figure 2 : Cad Model Figure 3 shows the meshed model of lower suspension arm with 2.0 mm of mesh size

and 10node Tetrahedron element (TET10) were considered for the analysis. 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; highertensile strength, material will have high fatigue life.7075-T6 (Aluminum alloy) are shown in Table

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976

6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME

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σ'f - σo s Strain Life Equation: εa = (2Nf) + ε'f (2Nf)

E

σmax εa E = (σ'f ) (2Nf) + ε'f ε' E (2Nf)

BOUNDARY CONDITION AND MESHED MODEL

Figure shows CAD model of lower suspension arm and its bounding box dimensions

Cad Model

Figure 3 shows the meshed model of lower suspension arm with 2.0 mm of mesh size and 10node Tetrahedron element (TET10) were considered for the analysis. Figure 3 shows boundary condition applied to the Lower suspension arm.

Meshed Model and Boundary Condition

PROPERTIES

Fatigue behavior of any material is highly dependent on its tensile strength; highertensile strength, material will have high fatigue life. The mechanical properties of C45 & AL

T6 (Aluminum alloy) are shown in Table

Direction Length

X 436.03Y 363.52

Z 65.00

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –

April (2013), © IAEME

MODEL

Figure shows CAD model of lower suspension arm and its bounding box dimensions

Figure 3 shows the meshed model of lower suspension arm with 2.0 mm of mesh size Figure 3 shows

Fatigue behavior of any material is highly dependent on its tensile strength; higher the The mechanical properties of C45 & AL

Length Unit

436.03 mm 363.52 Mm

65.00 Mm

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –

6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME

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Table 1: Material Properties

Properties Unit C45 AL 7075-T6

Strain-Life Parameters Strength Coefficient Pa 1099000000 876323996

Strength Exponent -0.11 -0.0751 Ductility Coefficient 0.52 0.4664

Ductility Exponent -0.54 -0.7779 Cyclic Strength Coefficient Pa 1402000000 943203168

Cyclic Strain Hardening Exponent

0.201 0.0966

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 5688.2 −60.4 −4801.2

B Oblique kerb limit load -9579.7 238.3 2382.1

C Lateral kerb strike limit load 549.7 845.9 12218.3

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.

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –

6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME

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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/ C45

Load Cases

Strain Life

C45 AL 7075 T6

SAEBKT SAETRANS Bracket Transmission

1 Pothole brake limit load

32232 124833 111763 123848

2 Oblique kerb limit load

923866 3404196 175206502 444289956

3 Lateral kerb strike limit load

2268 1058 805 1197

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –

6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME

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CONCLUSION

From the analysis of lower suspension arm it is concluded that if Al alloy (Al 7075-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

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