Design Analysis and Experimental investigation of Composite Mono Leaf spring

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1 Design Analysis and Experimental investigation of Composite Mono Leaf spring Prof. Gayatri J. Abhyankar 1, Vaibhav Holkar 2, Bhiva Malkar 3, Ganesh Sutar 4, Rajesh teli 5 1,2,3,4,5 Professor of mechanical engineering, Finolex Academy of Management and Technology, Ratnagiri Abstract: Reducing weight while increasing or maintaining strength of products is getting to be highly important research issue in this modern world. Composite materials are one of the material families which are attracting researchers and being solutions of such issue. The Automobile Industry has great interest for replacement of steel leaf spring with that of composite leaf spring, since the composite materials has high strength to weight ratio, good corrosion resistance. The material selected was glass fiber reinforced polymer (E-glass/epoxy). The design parameters were selected and analyzed with the objective of minimizing weight of the composite leaf spring as compared to the steel leaf spring. The work also gives focus on the application of FEA concept to compare two materials for leaf spring and propose the one having higher strength to weight ratio. Two materials used for comparison are; conventional steel and composite E-Glass/Epoxy. The deflection and bending stresses induced in the two leaf springs are compared. The solid modelling of leaf spring is done in SOLIDWORKS and analyses using ANSYS (WORKBENCH) In addition to this experimentation is done on the UTM. Keywords E-Glass/Epoxy, Leaf spring, SOLIDWORKS, Ansys 16.2 (Workbench). I. INTRODUCTION Suspension system of any vehicles contains leaf spring to absorb jolts. Leaf springs are mainly used in suspension systems to absorb shock loads in automobiles like light motor vehicles, heavy duty trucks and in rail systems. It carries lateral loads, brake torque, driving torque in addition to shock absorbing. The advantage of leaf spring over helical spring is that the ends of the spring may be guided along a definite path as it deflects to act as a structural member in addition to energy absorbing device.the vehicles must have a good suspension system that can deliver a good ride and good human comfort. It is observed that the failure of steel leaf springs is usually catastrophic. According to studies made for leaf spring the for weight reduction in automobiles as it leads to the reduction of un-sprung weight of automobile. The elements whose weight is not transmitted to the suspension spring are called the unsprung elements of the automobile. This includes wheel assembly, axles, and part of the weight of suspension spring and shock absorbers. The leaf spring accounts for 10-20% 0f the un-sprung weight. Material with maximum strength and minimum modulus of elasticity in the longitudinal direction is the most suitable material. To meet the need of natural resources conservation, automobile manufacturers are attempting to reduce the weight of vehicles in recent years. Weight reduction can be achieved primarily by the introduction of better material, design optimization and better manufacturing processes. In order to reduce the accidents, arising out of such failures conventional steel leaf spring can be replaced with gradually failing composite leaf springs. By doing this, the weight of the vehicle may also be reduced while maintaining the strength of the leaf spring. A composite material is nothing but DOI: /IJRTER XGEI5 350

2 permutation of two materials that produce an effect so that the combination produces combined properties that are different from any of those of its constituents. This is done purposefully in today s scenario to achieve different design, manufacturing as well as service advantages of product. In this paper leaf spring is representative of those products, for which automobile manufacturers are working to get best composite material that meets the current requirement of strength and weight reduction in one, to replace the existing steel leaf spring. The objective of the paper is to design leaf springs for deflection and bending stress made of steel and composite material. II. OBJECTIVE In order to safeguard natural resources and economize energy, weight reduction has been the main focus of automobile manufacturers in the present development. The introduction of better material, design optimization and better manufacturing processes can cause weight reduction in vehicle. The leaf spring is one of the potential items for weight reduction in automobile as it accounts for ten to twenty percent of the un-sprung weight. 1) To achieve substantial weight reduction in the suspension system. 2) Comparison of the results of standard Steel leaf spring and composite leaf spring. 3) Validation of results by theoretical calculations and experimentation on UTM. 4) Static analysis of standard Steel leaf spring and composite E-glass/Epoxy leaf spring using FEA. Finding out the deflection and bending stress for the same. III. DESIGN OF LEAF SPRING Mahindra Bolero Pick up FB PS specifications: Kerb weight = 1725 kg Load carrying capacity = 1250 Kg Gross weight of vehicle (m) = =2975 Kg Taking factor of safety (FOS) = 1.3 Acceleration due to gravity (a) = 9.81 m/s^2 Therefore, Total weight W = m a FOS = = N = = N Fig 1. Cantilever leaf The table I below shows the specifications of conventional leaf spring for selected vehicle: Parameter Value Length of the master leaf spring (2L) 900 mm Mass of the master leaf spring Kg Thickness (t) 8 mm Width (b) 60 mm

3 For steel leaf spring The mechanical Properties of conventional steel are as shown in table II below; Mech anical Properties of EN 47 Steel Properties Values Unit Young s modulus Mpa Tensile strength Mpa Elongation 8-25 % Fatigue 275 Mpa Yield strength Mpa Density 7700 Kg/m^3 Deflection of the leaf spring is given by, = I Bending stress in the leaf spring is given by, σ = II Let, W-Load on vehicle (N) L- Length of spring (mm) n- No. of spring E-Young Modulus (MPa) b- Width of leaf spring (mm) t- Thickness (mm) δ- Deflection of spring (mm) σ- Bending Stress (MPa) For manufacturing of composite leaf spring, we selected E glass/epoxy composite material the properties of the material are mentioned in table below in table. [1] Sr.no. Properties Value 1 Tensile modulus along X-direction (Ex) MPa 2 Tensile modulus along Y-direction (Ey) 6530 MPa 3 Tensile modulus along Z-direction (Ez) 6530 MPa 4 Tensile strength of the material 900 MPa 5 Compressive strength of the material 450 MPa 6 Shear modulus (Gxy) 2433 MPa 7 Shear modulus (Gyz) 1698 MPa 8 Shear modulus (Gzx) 2433 MPa 9 Poisson ratio along XY-direction(μxy) Poisson ratio along YZ-direction (μyz) Poisson ratio along ZX-direction (μzx) Mass density of the material (ρ) 2.6*10^6 kg/mm3 13 Flexural modulus of the material Flexural strength of the material 1200 By using the equation I and II the maximum deflection and maximum stress for steel leaf are calculated and using these values thickness of the composite leaf is calculated by keeping width constant and select the maximum thickness. The values are, E= N/mm^2 t = 15mm IV. FINITE ELEMENT ANALYSIS Finite element analysis is a computer based analysis technique for calculating the strength and behavior of structures. In the FEM the structure is represented as finite elements. These elements are joined at particular points which are called as nodes. The FEA is used to calculate the deflection,

4 stresses, strains temperature, buckling behavior of the member. In our project FEA is carried out by using the ANSYS Initially we don t know the displacement and other quantities like strains, stresses which are then calculated from nodal displacement. Finite Element Analysis is a simulation technique which evaluates the behavior of components, equipment and structures for various loading conditions including applied forces, pressures and temperatures. Thus a complex engineering problem with non-standard shape and geometry can be solved using finite element analysis where a closed form solution is not available. The finite element analysis methods provide results of stress distribution, displacements and reaction loads at supports etc. for the model. Static analysis: A static analysis is used to determine the displacements, stresses, strains and forces in structures or components caused by loads that do not induce significant inertia and damping effects. A static analysis can however include steady inertia loads such as gravity, spinning and time varying loads. In static analysis loading and response conditions are assumed, that is the loads and the structure responses are assumed to vary slowly with respect to time. The kinds of loading that can be applied in static analysis includes externally applied forces, moments and pressures, steady state inertial forces such as gravity and spinning Imposed non-zero displacements. If the stress values obtained in this analysis crosses the allowable values it will result in the failure of the structure in the static condition itself. To avoid such a failure, this analysis is necessary. Stepwise procedure for the static analysis of the leaf spring: 1) Prepare a geometric model of leaf spring by using solid works or other modelling software as per the designed dimension. This geometric model is save in step file format. 2) Open the ANSYS Workbench 16.2, select static structural ANSYS system and drag into the work place. 3) Update engineering data. For composite leaf spring, add the new material as E-glass fiber with its mechanical properties. 4) Import geometry and slice is into two parts and supress the left half section. 5) Modelling : a) Meshing b) Application of fixed support and force. 6) Solve. 7) Get the result. The FEA of the leaf spring of both the materials are carried out and obtained results for deformation and Equivalent von misses stresses in the leaf spring for different loads. The fig. shows the results for deformation and Equivalent von misses stresses in both conventional and composite leaf springs. The results are for design load i.e All Rights Reserved 353

5 Fig 2. Deformation in steel leaf spring Fig 3. Equivalent (von-mises) stress in steel leaf Spring Fig 4. Deformation in E-glass fiber leaf spring Fig 5. Equivalent (von mises) stress in E-glass fiber leaf spring V. EXPERIMENTATION The composite leaf springs are tested by using the UTM. The spring to be tested is examined for any defects like cracks, surface abnormalities, etc. The spring is loaded from zero to the prescribed maximum deflection and back to zero. The load is applied at the centre of spring; the vertical deflection of the spring centre is recorded in the load interval of 1000 N. The supports are given at the both end of using fixtures and the deflection of the spring centre is All Rights Reserved 354

6 Experimental Procedure 1. The spring is loaded from zero to the prescribed maximum deflection and back to zero. 2. The load is applied at the center of spring. 3. In the testing, firstly move the plunger up to desired height so that we can fix the fixture and leaf spring for test. 4. Fix the position of fixture. 5. On the fixture place the specimen. 6. Set the universal testing machine. 7. Apply the load gradually from 0 KN upto the fracture occurs. 8. The vertical deflection of the spring Centre is recorded simultaneously 9. The results are obtained in the form of graph of Load Vs Deflection. Test specimen before testing and the cracks occurred in the test specimen after the testing are shown below: Fig 6. Test specimen before testing Fig 7. Crack at the center of leaf Fig 8. Crack at end of leaf

7 VI. RESULT AND DISCUSSION Percentage mass saving: The table shows the comparison between the mass of the steel Leaf spring and composite mono-leaf spring. Table 1: % Mass saving 1. Mass of the steel leaf spring Kg 2. Mass of the composite leaf spring Kg 3. Percentage saving in mass % Above table shows that by using composite mono leaf spring 41.04% saving in mass is achieved. Theoretical results: The theoretical values of the deflection and the stresses for steel leaf spring and E-glass fibre mono leaf spring for the loads from 1000N to 10000N are tabulated in the table given below: Table 2: Theoretical results for deflection and stress Deflection (mm) Max. Stress (N/mm^2) Load (N) For EN47 steel For E glass Fibre For EN47 steel For E glass Fibre The results obtained by theoretical calculation are represented on graphs as follows: Plot of Load Vs Deflection (theoretical results) plot of Load Vs Max. stress (theoretical All Rights Reserved 356

8 FEA results: Similarly the values of the deflection and maximum stresses for the steel leaf and composite mono leaf spring obtained from the FEA analysis are tabulated in the table given below. Table 3: ANSYS results for deflection and stress Deflection (mm) Max. Stress (N/mm^2) Load For EN47 steel For E glass For EN47 steel For E glass (N) Fibre Fibre The results obtained from the analysis of the leaf spring are represented on graphs as follows: Plot of Load Vs Deflection (ANSYS results) Plot of Load Vs Max stress (ANSYS results) Experimentation result: The composite mono leaf spring is tested on the UTM, the results are obtained in the form of graph of Load vs All Rights Reserved 357

9 Plot of Load Vs Cross head travel VII. CONCLUSION As automobile world demands research of reducing weight and increasing strength of products, composite material should be up to the mark of satisfying these demands. As leaf spring contributes considerable amount of weight to the vehicle and needs to be strong enough, a single E-Glass/Epoxy composite leaf spring is designed and analyzed following the design rules of composite materials. The mass of the Composite mono-leaf spring is reduced by 41.07%. From static analysis of standard steel leaf spring and composite E-glass fiber mono-leaf spring using FEA, we found that deflection and max. stress in composite mono leaf spring is lesser than conventional leaf spring hence conventional leaf spring can be easily replaced by composite mono leaf spring. Experimentation shows that failure has occurred just before the designed load but by increasing the thickness we can make it safe. REFERENCES 1. Gulur Siddaramanna shiva shankar, Sambagam vijayarangan, (2006), Mono Composite Leaf Spring for Light Weight Vehicle Design, End Joint Analysis and Testing. Material Science, vol. 12, pp M.Venkatesan, D. Helmen Devaraj (2012), Design and analysis of Composite leaf spring in light vehicle. International Journal of Modern Engineering Research (IJMER), vol. 3, pp M. M. Patunkar, D. R. Dolas, (2011), Modelling and Analysis of Composite Leaf Spring under the Static Load Condition by using FEA. International Journal of Mechanical & Industrial Engineering, vol. 1, pp Pankaj Saini, Ashish Goel, Dushyant Kumar, (2013), Design and analysis of composite leaf spring for light vehicle. International Journal of Innovative Research in Science, Engineering and Technology, vol. 2, pp Mr. Akshay Kumar, Mr. V. J. Shinde, Mr. S. S. Chavan, (2014), Design, Analysis, Manufacturing and Testing of Mono Composite Leaf Spring Using UD E-Glass Fiber/Epoxy. International Journal of Advanced Technology in Engineering and Science, vol. 2, pp M. Sureshkumar, Dr. P. Tamilselyam, G. Tharanitharan, (2015), ), Experimental Investigation of Hybrid Fiber Mono Composite Leaf Spring for Automobile Applications. International Journal of Mechanical Engineering and Research, vol. 5, pp K. Nagendra Babu, P. Sudheer kumar, (2016), Design and analysis of Jute / E-Glass / Epoxy Composite Mono-leaf Spring of varying c/s area using Ansys14.5 International Journal of Innovations in Engineering and Technology, vol. 7 pp Achamyeleh, A Kassie, R Reji Kumar and Amrut Rao,(2014), Design of single composite leaf spring for light weight vehicle. International Journal of Mechanical Engineering and Robotic Research, vol. 3, pp Ms. Surekha Sangale, Dr. Kishor B. Kale, Dhighe Y. S. (2015), Design analysis of carbon / Epoxy composite leaf spring. International Journal of Research in Advent Technology, vol. 5, pp Sushil B.Chopade, Prof.K.M.Narkar, Pratik K Satav, (2013), Design and analysis of Eglass/Epoxy composite mono-leaf spring for light vehicle. International Journal of Innovative Research in Science, vol. 4, pp. All Rights Reserved 358