International Journal of Mechanical Engineering and Technology (IJMET) Volume 7, Issue 5, September October 2016, pp.177 183, Article ID: IJMET_07_05_019 Available online at http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=7&itype=5 Journal Impact Factor (2016): 9.2286 (Calculated by GISI) www.jifactor.com ISSN Print: 0976-6340 and ISSN Online: 0976-6359 IAEME Publication DESIGN AND ANALYSIS OF COMPOSITE LEAF SPRING Pinaknath Dewanji Department of Mechanical Engineering, Gitam University, India. ABSTRACT The present paper deals with the Design and analysis of composite leaf spring. The analysis has been conducted by using ANSYS-12 software with the help of static structural tool. A threelayer composite leaf spring with full length leave made of E-Glass/epoxy composite material has been used. The results of Conventional steel leaf spring have been compared with the present results obtained for composite leaf spring. E-glass/epoxy material is better in strength and lighter in weight as compared to the conventional steel leaf spring. Lot of work has been done and is shown in this paper in an interest of justifying the title of the paper. Key words: Leaf spring, Finite element analysis, Fatigue analysis CAE tool. Cite this Article: Pinaknath Dewanji, Design and Analysis of Composite Leaf Spring. International Journal of Mechanical Engineering and Technology, 7(5), 2016, pp. 177 183. http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=7&itype=5 1. INTRODUCTION Leaf spring is widely used in automobiles and is one of the important components of suspension system. It consists of one or more leaves. As a general rule, the leaf spring is regarded as a safety component as its failure could lead to severe accidents. The leaf spring might carry loads, brake torque, driving torque, etc. In addition to shock absorbers, the multi-leaf spring is made of several steel plates of different lengths stacked together. During normal operation, the spring compresses to absorb the shock. The leaf springs bend and slide on each other thereby allowing suspension movement. Fatigue failure is the predominant mode of in-service failure of many automobile components. This is due to the fact that the automobile components are subjected to variety of fatigue loads like shocks caused due to road irregularities, the sudden loads due to the wheel traveling over the bumps etc. The leaf springs are more affected due to fatigue loads as they are a part of the un sprung mass of the automobile. In this paper, the analysis of eight-leaf steel spring is presented. The leaf spring was analysed over its full operating range from 1kN to 10 kn. Bending stress and deflection are the target results. Finally, fatigue life of the steel leaf spring is also predicted. The main objective of this work is to perform finite element analysis of multi leaf spring. experimental results have been taken on a full scale static load testing machine, in which leaf spring is held under an axial load at centre till maximum deflection. These experimental results will be compared with FEA results for validation. http://www.iaeme.com/ijmet/index.asp 177
Pinaknath Dewanji 2. MATERIAL AND METHODS Material properties and Design parameters below is showing the different parameters related to material properties; Design parameters of the multi leaf spring used in this work are: Total span length (eye to eye): 1450mm Number of full length leaves: 02 Length of full length leaves (L-1 and L-2): 1450 mm each Width of all leaves: 70mm Thickness of all leaves: 12mm Number of graduated length leaves: 07 Length of graduated length leaves; (L-3, L-4, L-5, L-6, L-7, L-8 and L-9): 1320mm, 1140mm, 940mm, 800mm, 640mm, 464mm & 244mm respectively. 3. MATERIAL PROPERTIES Material properties of E glass/ Epoxy (GFRP): The different parameters related to GFRP leaf springs are tabulated in the table below: Properties of E-Glass/ Epoxy composite leaf spring Sr. No Parameter Value 1 Tensile Strength (MPa) 900 2 Compressive Strength(MPa) 450 3 Possions Ratio 0.217 4 Density (kg/m 3 ) 2.16x10 5 5 Flexural modulus (E) (MPa) 40000 It is obvious that the composite material have better mechanical properties than conventional steel as the energy storage capacity of composite material is much higher than steel therefore it is the best material http://www.iaeme.com/ijmet/index.asp 178
Design and Analysis of Composite Leaf Spring for application selected. Also from eq.1 the material with maximum strength and minimum modulus of elasticity is the most suitable material for leaf spring application 4. STATIC ANALSYS The aim of this analysis is to study the multi-leaf steel leaf spring and verification of the results within the desirable limits. ANSYS software is used to analyse the stresses by performing static analysis for the given leaf spring specification and to determine the deflection in leaf springs. Analysis involves discretization called meshing, boundary conditions, loading. 4.1. Elements Type SOLID45-3-D Structural Solid. CONTA174-3-D 8-Node Surface-to-Surface Contact. 4.2. Meshing Meshing involves division of the entire of model into small pieces called elements. It is convenient to select the free mesh because the leaf spring has sharp curves, so that shape of the object will not alter. To mesh the leaf spring the element type must be decided first. Here, the element type is solid 45. The element edge length is taken as 5 mm. The numbers of elements are taken 2225 and the total numbers of nodes are 8099. 4.3. Boundary Conditions The front eye of the leaf spring is coupled directly with a pin to the frame so that the eye can rotate freely about the pin but no translation is occurred. The rear eye of the spring is connected to the shackle which is a flexible link the other end of the shackle is connected to the frame of the vehicle. The force 4169N applied at both the eye end of leaf spring. The both eyes of the leaf spring have the flexibility to slide along the X-direction when load applied on the spring and also it can rotate about the pin in Z- direction. The link oscillates during load applied and removed. So the displacement at the both eye is constrained along the X and Z directions Figure 1 Meshed Model of Steel Leaf Spring with Boundary Conditions http://www.iaeme.com/ijmet/index.asp 179
Pinaknath Dewanji Figure 2 Bending Stress of Steel Leaf Spring Figure 3 Bending Stress of Steel Leaf Spring Figure 4 Bending Stress of Composite Leaf Spring http://www.iaeme.com/ijmet/index.asp 180
Design and Analysis of Composite Leaf Spring Figure 5 Complete Deformation of Composite Leaf Spring 5. RESULTS From the results of static analysis of steel leaf spring, it is seen the displacement of leaf spring is 53.159 mm which is well below the camber length of leaf spring shown in fig.4. It is seen that the maximum bending stress is about 450.73MPa, which is less than the yield strength of the material shown in fig.3. The FEA results are compared with the theoretical results and found that the theoretical result and FEA result are nearer to each other. Table 4 Comparison between theoretical and ANSYS results of conventional steel leaf spring Parameter Theoretical Results FEA Results for for steel leaf spring steel leaf spring Variation Load, N 4169 4169 NIL Bending Stress, MPa 466.84 450.73 3.04 % Total Deflection, mm 51.24 53.159 3.06 % After that the multi leaf spring with E-Glass/Epoxy material is analyzed in ANSYS-12 with same dimension and same boundary condition as that of conventional leaf spring, showing bending stress and deflection under load in figures.5 & 6. The comparison between steel leaf spring and composite leaf spring for deflection and bending stress results from the ANSYS is shown in the Table-V. Table 5 FEA results comparison between steel and composite leaf spring FEA Results for steel FEA Results for Parameter leaf spring composite leaf spring Variation Load, N 4169 4169 NIL Bending Stress, MPa 450.73 338.03-25.05 % Total Deflection, mm 53.159 34.676-34.76 % http://www.iaeme.com/ijmet/index.asp 181
Pinaknath Dewanji By the comparison of results between steel leaf spring and the composite leaf spring from ANSYS-12 the deflection is decreased by 34.76 % in composite leaf spring that is within the camber range. The bending stresses are decreased by 25.05% in composite leaf spring means less stress induced with same load carrying conditions. The conventional multi leaf spring weights about 10.27kg whereas the E-glass/Epoxy multi leaf spring weighs only 3.26 kg. Thus, the weight reduction of 67.88% is achieved. By the reduction of weight and the less stresses, the fatigue life of composite leaf spring is to be higher than that of steel leaf spring. Totally it is found that the composite leaf spring is the better that of steel leaf spring. Table 6 Percent saving of weight by using composites Materials Weights % weight saving Conventional Steel 10.27 kg ----- E-glass/epoxy 3.26 kg 67.88% 6. CONCLUSION In the present work, a steel leaf spring was replaced by a composite leaf spring due to high strength to weight ratio for the same load carrying capacity and stiffness with same dimension as that of steel leaf spring. A semi-elliptical multi leaf spring is designed for a four wheel automobile and replaced with a composite multi leaf spring made of E-glass/epoxy composites. Under the same static load conditions the stresses and the deflection in leaf springs are found with great difference. Stresses and deflection in composite leaf springs is found out to be less as compared to the conventional steel leaf springs. All the FEA results are compared with the theoretical results and it is found that they are within the allowable limits and nearly equal to the theoretical results. A comparative study has been made between steel and composite leaf spring with respect to strength and weight. Composite leaf spring reduces the weight by 67.88% for E-Glass/Epoxy. E-glass/epoxy composite leaf spring can be suggested for replacing the steel leaf spring both from stiffness and stress point of view. Totally it is found that the composite leaf spring is the better that of steel leaf spring. Therefore, it is concluded that composite multi leaf spring is an effective replacement for the existing steel leaf spring in vehicles. REFERENCE [1] M.Venkatesan Design and Analysis Of Composite Leaf Spring In Light Vehicle, International Journal of Modern Engineering Research (IJMER) Vol.2, Issue.1, Jan-Feb 2012 pp-213-218 ISSN: 2249-6645. [2] M.M. Patunkar Modeling And Analysis of Composite Leaf Spring Load Condition By Using FEA, (IJMIE) International Journal of Mechanical & Industrial Engineering, Volume 1 Issue 1-2011. [3] U. S. Ramakanth, K. Sowjanya Design and analysis of automotive multi-leaf springs using composite materials International Journal of Mechanical Production Engineering Research and Development (IJMPERD) ISSN 2249-6890,Vol. 3, Issue 1, Mar 2013, 155-162 TJPRC Pvt. Ltd. [4] N.V. Hargude, J.G. Herekar and P.P. Awate, Analysis of Composite Mono Leaf Spring. International Journal of Advanced Research in Engineering and Technology (IJARET), 5(5), 2014, pp. 9 16. [5] B.Vijaya Lakshmi, I. Satyanarayana static and dynamic analysis on composite leaf spring in heavy vehicle International Journal of Advanced Engineering Research and Studies E-ISSN2249 8974, IJAERS/Vol. II/ Issue I/Oct.-Dec.,2012/80-84. http://www.iaeme.com/ijmet/index.asp 182
Design and Analysis of Composite Leaf Spring [6] Y. N. V. Santhosh Kumar & M. Vimal Teja Design an d Analysis of Composite Leaf Spring International Journal of Mechanical and Industrial Engineering (IJMIE), ISSN No. 2231 6477, Vol-2, Issue-1, 2012. [7] Syambabu Nutalapati, Design and Analysis of Leaf Spring by using Composite Material for Light Vehicles. International Journal of Mechanical Engineering and Technology (IJMET), 6(12), 2015,pp. 36 59. [8] Dara Ashok, M.V. Mallikarjun and Venkata Ramesh Mamilla design and structural analysis of composite multi leaf spring International Journal of Emerging trends in Engineering and Development ISSN 2249-6149,Issue 2, Vol.5 (July 2012). [9] Rakesh Hota, Kshitij Kumar, Ganni Gowtham and Avinash Kumar Kotni, Experimental Investigation of Fiberglass Reinforced Mono-Composite Leaf Spring. International Journal of Design and Manufacturing Technology (IJDMT), 4(1), 2016, pp. 30 42. http://www.iaeme.com/ijmet/index.asp 183