THERMAL ANALYSIS COMPARISON OF EN8 AND AUTOMOTIVE ALUMINA CRANKSHAFT Kiran G. Nath* 1, V.Murugan 2

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1 ISSN IJESR/May 2014/ Vol-4/Issue-5/ Kiran G. Nath et al./ International Journal of Engineering & Science Research THERMAL ANALYSIS COMPARISON OF EN8 AND AUTOMOTIVE ALUMINA CRANKSHAFT Kiran G. Nath* 1, V.Murugan 2 1 PG scholar (Thermal Engineering), Dept. of Mechanical Engg., R.V.S. College of Engineering and Technology, Coimbatore, India. 2 Asst. Prof, Dept. of Mechanical Engg., R.V.S. College of Engineering and Technology, Coimbatore, India. ABSTRACT The Computer aided modeling and analysis of crankshaft is to study was to evaluate and compare the fatigue performance of two competing manufacturing technologies for automotive crankshafts, namely forged steel and ductile cast iron. In this study a static simulation was conducted on two crankshafts, EN8 and automotive alumina, from similar single cylinder four stroke en-gines.finite element analyses was performed to obtain the variation of stress magnitude at critical locations. The dynamic analysis was done analytically and was verified by simulations in ANSYS. Results achived from aforementioned analysis were used in optimization of the crankshaft. Geometry, material and manufacturing processes were optimized considering different constraints, manufacturing feasibility and cost. The optimization Process includes geometry changes compatible with the current engine, fillet rolling and result in in-creased fatigue strength and reduced cost of the crankshaft, without changing connecting rod and engine block Keywords: Crankshaft, Forged steel, Cast iron. 1. INTRODUCTION The objective of this study is to compare the durability of crankshafts from two competing materials, as well as to perform static load and stress analysis. The crankshaft materials used in this study are EN8 and AUTOMOTIVE ALUMINA from a four stroke petrol engine. Material composition tests showed that the EN8 material that we used in the crankshaft. Static load analysis was performed to determine the service loading of the crankshafts and FEA was conducted to find stresses at critical locations. Finally, material, and testing processes were optimized for the AUTOMOTIVE ALUMINA crankshaft. The stresses on the crankshaft depend on the heat treatment temperatures employed, the depth of hardening and the type of quenchant. Process conditions that give rise to compressive residual stresses on the surface of heat treated components are favorable. The finite element analysis is performed by using computer aided engineering software ANSYS. The theory of flexible multi-body systems dynamics is combined with FEA method to study the crankshaft; the dynamic boundary loads on the joints in a working cycle are determined by the simulation on the crankshaft system in the study done by Dr.S.V.Deshmukh et al. [1]. The main objectives of this project are to investigate and analyze the deformation, stress, strain distribution. The dissertation describes the mesh optimization with using finite element analysis technique to predict the higher stress and Critical region on the component. Several aspects of the crankshaft were not up to the technical standards, such as distance between the quenched layer and the web, chemical composition, hardness and microstructure of the quenched layer, yield strength, and impact toughness. The dynamic analysis performed in the paper by Farzin H et al. [2] resulted in the development of the load spectrum applied to the crankpin bearing. This load was then applied to the FE model and boundary conditions were applied according to the engine mounting conditions Crankshaft specifications, operating conditions, and various failure sources are first reviewed. Then design aspects and manufacturing procedures for crankshafts are discussed. This includes a review of the effects of influential parameters such as stresses on fatigue behavior. The common crankshaft material and manufacturing process technologies currently in use are then compared with regards to their durability performance. A comparative study and failure investigation has been conducted and the mechanical properties of the crankshaft *Corresponding Author 225

2 including tensile properties, marohardness (HB) and surface hardness (HV1) were discussed by Zhiwei Yuet al. [3].This is followed by a discussion of durability assessment procedures used for crankshafts, as well as bench testing and experimental techniques. The main objective of this study is to investigate weight and cost reduction opportunities for crankshaft. The need of load history in the FEM analysis necessitates performing a detailed dynamic load analysis. Therefore, this study consists of three major sections: static load analysis, FEM and stress analysis. In this study a static simulation was conducted on two crankshafts, EN8 and AUTOMOTIVE ALUMINA, from similar single cylinder four stroke engines. Finite element analysis was performed to obtain the variation of stress magnitude at critical locations. 2. METHODLOGY Jonathan Williams et al. [4] have done a comparative study on the fatigue behavior of forged steel and ductile iron crankshafts from a one-cylinder engine as well as to determine if the fatigue life of a crankshaft can be accurately estimated using fatigue life predictions. 3. ANALYSIS 3.1 Finite Element Method The Finite Element Method (FEM) is a reliable numerical technique for analyzing engineering designs. FEM replaces a complex problem with many simple problems. It divides the model into many small pieces of simple shapes called elements. Elements share common points called nodes. The behavior of these elements is wellknown under all possible support and load scenarios. The motion of each node is fully described by translations in the X, Y, and Z directions. These are called degrees of freedom (DOFs). Analysis using FEM is called Finite Element Analysis (FEA). R. J. Deshbhratar et al. [5] has discussed the method to find the maximum stress point and dangerous areas are found by the deformation analysis of crankshaft [5]. Ansys formulates the equations governing the behavior of each element taking into consideration its connectivity to other elements. These equations relate the displacements to known material properties, restraints, and loads. Next, the program organizes the equations Copyright 2013 Published by IJESR. All rights reserved 226

3 into a large set of simultaneous algebraic equations. The solver finds the displacements in the X, Y, and Z directions at each node. Using the displacements, the program calculates the strains in various directions. Finally, the program uses mathematical expressions to calculate stresses. Finite element proceeds at present very widely used in the engineering analysis. In the study by Ram.R.Wayzode et al. [6] the analysis was done for different engine speeds and as a result critical engine speed and critical region on the crankshaft were obtained. In this project a constant engine speed of 1500 rpm is considered throughout the analysis. The finite element method is a numerical analysis technique for obtaining approximately solution to varieties of engineering in the finite element analysis actual continuum or body of the matter like solid, liquid or gas is represented as an assemblage of sub division called finite element. These finite elements of field variable inside the finite element can approximately by the single function. The approximately functions are defined in terms of the values of the field variable of the nodes by solving the solid variables the total values of the field variable of the nodes by solving the solid variables the total values of the nodes by soling the solid variables the total values of the field variable can be found out Steps In FEA Definitions of the problem and its domain. Discretization of the domain the continuum. Identification of state variable. Formulation of the problem. Establishing coordinate system. Constructing approximate functions for the elements. Obtaining element matrix and equation. Coordinate transformation. Assembly of element equations. Introduction of the final set of simultaneous equation. Interpretations of the results Advantages of FEA Applicable to any field problem such as heal transfer stress analysis, magnetic field etc. There is no matrix restriction. Approximately it is easily improved by grading the mesh so that more elements appear where field gradients are high and more resolution is required. Compounds that have different behavior and different mathematical description can be solved. 3.2 MATERIALS USED EN8 The crankshafts are most usually made of Forged steel [2] or En8 for production engines. These materials have different properties and suitable for different engines. But in this project Automotive Alumina is used as Crankshaft material. This should achieve better mechanical properties towards the core. Table 1: EN8 Composition 080M40 (EN8) Specification Chemical composition Carbon % Silicon % Manganese % Sulphur Max Phosphorus Max Copyright 2013 Published by IJESR. All rights reserved 227

4 Table 2: Mechanical properties Table 3: EN8 Equivalents 080M40 (EN8) - mechanical properties in "R" condition Max Stress n/mm 2 Yield Stress 465 n/mm 2 Min (up to 19mm LRS) 0.2% Proof Stress 450 n/mm 2 Min (up to 19mm LRS) Elongation 16% Min (12% if cold drawn) Impact KCV 28 Joules Min (up to 19mm LRS Hardness Brinell EN8 Equivalents BS970: 1955 EN8 BS970/PD970: 1970 onwards 080M40 European C40, C45, Ck40,Ck45, Cm40, Cm45 Werkstoff No , , US SAE (AISI) 1039, 1040, 1042, 1043, Automotive Aluminium Aluminium alloys are alloys in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories heattreatable and non-heat-treatable. Aluminium alloys are widely used in engineering structures and components where light weight or corrosion resistance is required. Aluminium matrix composites (AMCs) refer to the class of light weight high performance aluminium centric material systems. The paper by M K Surappa et al. [7] presents an overview of AMC material systems on aspects relating to processing, microstructure, properties and applications. Fig 1: Automotive alumina composition Mallikarjuna G B et al. [8] investigated about Metal Matrix Composites (MMC s) which have been developed to meet the demand for lighter materials with high specific strength, stiffness and wear resistance. 4. DESIGN OF CRANKSHAFT 4.1 Force Imposed On A Crankshaft Copyright 2013 Published by IJESR. All rights reserved 228

5 Our selected engine is combustion ignition Petrol Engine. The obvious source of force applied to a crankshaft is the product of combustion chamber pressure acting on the top of the piston. High-performance, contemporary high-performance compression -ignition (CI) engines can see combustion pressures in excess of 25 bar. This kind of force exerted on a crankshaft rod journal which produces substantial bending and torsion moments and the resulting tensile, compressive and shear stresses. 4.2 Design Procedure The crankshaft must be designed or checked for at least two crank positions. First, when the crankshaft is subjected to maximum bending moment and secondly when the crankshaft is subjected to maximum twisting moment or torque. The additional moment due to weight of flywheel, bell tension and other forces must be considered. It is assumed that the effect of bending moment does not exceed two bearing between which a force is considered. F p D p 2 Diameter of piston (D p ) 50 mm Maximum fuel gas pressure (p) 2.5N/mm 2 Length of connecting rod (L c ) Stroke of piston mm Crank radius (r) Weight of flywheel (w) Distance between flywheel and journal (y) Speed of engine (N) 125 m 2 Crank Radius 92 / 2 46 mm 0.24 KN N 75 mm 1000 rpm Permissible stress in bending (σ b )70 /mm 2 Permissible stress in shear (τ) 40 N/mm 2 Permissible stress in bearing (σ c ) 8 N/mm 2 Now maximum force acting on the piston is given by, 2.5 (50) 2 F N, this force is transmitted to the crankshaft through connecting rod. The inclination of connecting rod ( ) with line of stroke for crank angle (θ) at 30 o is found out using (or) Sin -1 Sin o Copyright 2013 Published by IJESR. All rights reserved 229

6 The fuel force F is resolved into radial and tangential components as, Radial force (Force acting along the crank) F r F Cos (θ + ) Cos ( ) F r N Tangential force (force acting perpendicular to crank) F t F Sin (θ + ) Sin (40.7) F t 3201 N Design of crank pin: For the design of crank pin, the fuel force F may be considered. Design is based on bearing stress. Let, L d Length of crank pin Diameter of crank pin Bearing stress (σ c ) Let, Assume (L) 1.1 d (d) d 1/2 1/2 d Then, 23.7 mm L 1.2 d L 26 mm Design of main journal: Let, D L Diameter of journal Length of journal The design of main journal is based on equivalent bending moment due to torque developed by the force and the bending moment developed by the crank. Since the force applied by the connecting rod is shared by the two journals equally. The force on each journal is half of force value. Hence at maximum torque position the twisting moment produced on the journals. T Tangential force crank radius. T Copyright 2013 Published by IJESR. All rights reserved 230

7 T N- mm Bending moment due to weight of flywheel, M w y M > N- mm Equivalent bending moment, M c M c N mm Bending stress, σ b D mm Hence take D 18 mm Then L 1.25 D L 22.5 mm Design of web: Thickness of web,t 0.7 d mm Width of web, w 1.14 d mm Now the centre distance between the journals, x + t + l +t x 78 mm The induced stresses in the crank pin, web, journals are checked as follows, Induced stresses in crank pin. Copyright 2013 Published by IJESR. All rights reserved 231

8 The maximum bending moment at the centre of crank pin, M N mm Induced bending stress, σ b N/mm 2 < (σ b ) Induced direct shear stress, τ N/mm 2 < (τ) Induced stresses in the journal: The induced bearing stress in the journal σ b This bearing load is the resultant load produced by the flywheel weights acting vertically and the reaction due to crank pin force acting horizontally, assuming inclination of connecting rod. Weight of flywheel, w N Reaction acting on one journal, F N Resultant force, R N Bearing pressure, P b Copyright 2013 Published by IJESR. All rights reserved 232

9 2.071 N/mm 2 < (σ c ) Direct stress in the web, σ o 8.35 N/mm 2 Bending stress due to radial force, σ br N/mm 2 Total induced stress, σ σ o + σ br +σ bt σ bt N/mm 2 σ σ N/mm 2 Since this is more than allowable value (70 N/mm 2 ) let us increase the width of crank w 80 mm Now we get, σ o 8.10 N/mm 2 σ br N/mm 2 σ bt N/mm 2 σ N/mm 2 Since all the induced stresses are less than their allowable values, our design is safe. 5. MODEL GENERATION 5.1 Modeling In Part modeling you can create a part from a conceptual sketch through solid feature-based modeling, as well as build and modify parts through direct and intuitive graphical manipulation. The Part Modeling Help introduces you to the terminology, basic design concepts, and procedures that you must know before you start building a part. Part Modeling shows you how to draft a 2D conceptual layout, create precise geometry using Copyright 2013 Published by IJESR. All rights reserved 233

10 basic geometric entities, and dimension and constrain your geometry. You can learn how to build a 3D parametric part from a 2D sketch by combining basic and advanced features, such as extrusions, sweeps, cuts, holes, slots, and rounds. Finally, Part Modeling Help provides procedures for modifying part features and resolving failures Design Concepts for Creating Crank Shaft We can design many different types of models in Solid works. However, before we begin our design project, we need to understand a few basic design concepts: Design Intent - Before we design our model, we need to identify the design intent. Design intent defines the purpose and function of the finished product based on product specifications or requirements. Capturing design intent builds value and longevity into your products. This key concept is at the core of the Solid works featurebased modeling process. Feature-Based Modeling - Solid works part modeling begins with creating individual geometric features one after another. These features become interrelated to other features as you reference them during the design process. Parametric Design - The interrelationships between features allow the model to become parametric. So, if we alter one feature and that change directly affects other related features, then Solid works dynamically changes those related features. This parametric ability maintains the integrity of the part and preserves your design intent. Associability Solid works maintains design intent outside Part mode through associatively. As we continue to design the model, we can add parts, assemblies, drawings, and other associated objects, such as piping, sheet metal, or electrical wiring. All of these functions are fully associative within Solid works. So, if we change our design at any level, our project will dynamically reflect the changes at all levels, preserving design intent. Solid works Part enables to design models as solids in a progressive three-dimensional solid modeling environment. Solid models are geometric models that offer mass properties such as volume, surface area, and inertia. If you manipulate any model, the 3-D model remains solid. Solid works provides a progressive environment in which we can create and change your models through direct graphical manipulation. You drive the design process for your project by selecting an object (geometry) and then choose a tool to invoke an action on that object. This object-action workflow provides greater control over the design of your models while allowing you to express your creativity. The user interface provides further support for this design process. As you work with your model, the context sensitive user interface guides you through the design process. After you choose an object and an action, Solid works interprets the current modeling context and presents requirements and optional items to complete the task. This information is displayed in a non obtrusive user interface called the dashboard that enhances your ability to directly work with your models by assessing your actions and guiding you through the design process. The Solid works progressive modeling environment streamlines the design process enabling you to concentrate on product development and drive your designs to new levels of creativity. 5.2 Importing Model Into Ansys Fig 2: Final model of the crankshaft Copyright 2013 Published by IJESR. All rights reserved 234

11 In this prompt, the dimensions of the real part model has been modeled using Solid Works, the solid works is best suitable only for modeling the crank shaft and the part model is imported as *.prt file. In solid works the 3 Dimensional parts has been converted into*. Para-solid file. Now we can be able to set the actual dimensions appearance for the converted model file. After setting the require data in solid works. After completing the designing processes of crankshaft, the file is imported to the Ansys software. Ansys specialized in the area of analyzing the materials and different kinds of parts.this part model may be imported to Ansys as *.IGES file. Thus the IGES file has been imported in Ansys work bench, and in Ansys, static structural analysis has been made on the IGES file. After the process it has been stored. That it can be viewed in Ansys bench as a link to Ansys products launcher. Thus the result can be generated in the general post processor using the Ansys product launcher. The ANSYS commitment is to provide unequalled technical depth in any simulation domain. Whether it s structural analysis, fluids, thermal, electromagnetics, meshing, or process & data management we have the level of functionality appropriate for your requirements. Through both significant R&D investment and key acquisitions, the richness of our technical offering has flourished. A strong foundation for multiphysics sets ANSYS apart from other engineering simulation companies. Our technical depth and breadth, in conjunction with the scalability of our product portfolio, allows us to truly couple multiple physics in a single simulation. Technical depth in all fields is essential to understand the complex interactions of different physics. The portfolio breadth eliminates the need for clunky interfaces between disparate applications. The ANSYS capability in multiphysics is unique in the industry; flexible, robust and architected in ANSYS Workbench to enable to solve the most complex coupled physics analyses in a unified environment Meshing In Ansys Fig 3: Imported IGS file in ANSYS In preparing the model for analysis, Ansys subdivides the model into many small tetrahedral pieces called elements that share common points called nodes. Type of mesh global Element size 0.5 Mode of mesh Key points volume all Copyright 2013 Published by IJESR. All rights reserved 235

12 Elements can have straight or curved edges. Fig 4: Meshing of Crankshaft Each node has three unknowns, namely, the translations in the three global directions. The process of subdividing the part into small pieces (elements) is called meshing. In general, smaller elements give more accurate results but require more computer resources and time. Ansys suggests a global element size and tolerance for meshing. The size is only an average value, actual element sizes may vary from one location to another depending on geometry. It is recommended to use the default settings of meshing for the initial run. For a more accurate solution, use a smaller element size. After meshing the model the boundary conditions are applied properly then the final results are obtained. The following figure shows the final results of structural analysis for different materials like austenitic alloy, titanium alloy, plastic reinforced carbon and stainless steel. 6. ANAYLSIS OF EN8 AND AUTOMOTIVE ALUMINA 6.1 En8 Analysis In Ansys 6.1.1total Deformation Occured In engineering, deflection is the degree to which a structural element is displaced under a load. It may refer to an angle or a distance.the deflection distance of a member under a load is directly related to the slope of the deflected shape of the member under that load and can be calculated by integrating the function that mathematically describes the slope of the member under that load Equivalent elastic strain Fig 5: Total deforamtion EN8 Elastic strain, ε e, is any strain that takes place before exceeding the yield stress. However, it is important to note that, for hardening materials, elastic strain is increasing during post yield also. Hence,strain that is removed during unloading is a better definition of elastic strain. Plastic strain,ε p, is permanent strain that remains after unloading. Total strain is the sum of elastic strain and plastic strain, ε ε e + ε p.when hardening occurs the value of the yield stress changes. Copyright 2013 Published by IJESR. All rights reserved 236

13 6.1.3 Equivalent Von-Mises Stress Fig 6: Elastic strain in EN8 Von-Mises Stress suggests that the yielding of materials begins when the second deviatoric stress invariant reaches a critical value. It is part of a plasticity theory that applies best to ductile materials, such as metals. Prior to yield, material response is assumed to be elastic. Scalar stress value that can be computed from the stress tensor. In this case, a material is said to start yielding when its von Mises stress reaches a critical value known as the yield strength. The von Mises stress is used to predict yielding of materials under any loading condition from results of simple uniaxial tensile tests. The von Mises stress satisfies the property that two stress states with equal distortion energy have equal von Mises stress. Fig 7: Equivalent von mises stress in EN8 6.2.Automotive Alumina Analysis In Ansys 6.2.1Total static structural Deformation Occured Min Deformation:0 m Max Deformation: E^-8 m Copyright 2013 Published by IJESR. All rights reserved 237

14 Fig 8: Total deformation in automotive Alumina crankshaft Equivalent elastic strain Min equivalent strain: 1.676E^ -18 Max equivalent strain: E^-6 Fig 9: Equivalent elastic strain in Automotive Alumina Equivalent Von-Mises Stress Min equivalent stress:2.3352e-7 pa Max equivalent stress: E5 pa Fig 10: Equivalent von-mises stress in automotive alumina Copyright 2013 Published by IJESR. All rights reserved 238

15 7. RESULTS AND DISCUSSION From the following tabulation we get the differences in deformation, equivalent strain and Von-misses Stress between EN8 and AUTOMOTIVE ALUMINA material. 7.1 Total Structural Deformation 7.2 Equivalent Strain Result Material Max (mm) Min( mm) EN E-08 0 AUTOMOTIVE ALUMINA E-08 0 Material Max strain(m/m) Min strain(m/m) EN e e-19 AUTOMOTIVE ALUMINA e Von Misses Stress Result Accurate stresses are critical input to fatigue analysis and optimization of the crankshaft. The total structural deformation of alumina is less compared to EN8.The results from the analysis show longer lives for alumina than the EN8. Critical locations on the crankshaft geometry are all located on the fillet areas because of high stress gradients in these locations which result in high stress concentration factors. So this area prone to appear the bending fatigue crack. Since the alumina crankshaft is able to withstand the static load, it is concluded that there is no objection from strength point of view also, in the process of replacing the EN8 crankshaft by alumina crankshaft. The reduction in weight also increases the efficiency of engine. 8. CONCLUSION Finite Element Analysis of the single cylinder EN8 and Automotive Alumina crankshaft has been done using FEA tool ANSYS Workbench. From the results obtained by finite element analysis, many discussions have been made and concluded that automotive alumina is having better structural and thermal behaviors. Since the Automotive Alumina crankshaft is able to withstand the static load and have better tensile strength than EN8 and it is concluded that there is no objection from strength point of view also, in the process of replacing the EN8 crankshaft by Automotive Alumina crankshaft. We can also reduce Automotive Alumina crankshaft cost by the mass production. This project will make an impressing mark in the field of automobile industries. 9. SCOPE FOR FUTURE This project has been chosen out of interest in analyzing the crank shaft by change the web position changes and the dimensions of shaft by the same way we have found that the above said two materials satisfied to the fullest. The estimated scope for future work is to analyze various 4-stroke engines and to re-engineer the current crankshaft. Various tests would be performed to get efficient crankshaft. Finite element analysis will be performed on both EN8 and Automotive alumina crankshaft. It would also encompass optimization of crankshaft geometry. The future research would also strive to improve the efficiency of the engine by altering the composition of crankshaft material. REFERENCES Material Max stress(n/m²) Min stress(n/m²) EN8 6.55e e-7 AUTOMOTIVE ALUMINA 6.65e e-7 [1] Deshmukh SV, Wayzode RR, Alvi NG. Dynamics Simulation on Crankshaft System. Golden research thoughts 2012; 1(xi): 1-4. Copyright 2013 Published by IJESR. All rights reserved 239

16 [2] Montazersadgh FH, Fatemi A. Dynamic Load and Stress Analysis of a Crankshaft. SAE International [3] Yu Z, Xu X. Failure analysis of a diesel engine crankshaft Elsevier. Engineering failure analysis 2005; 12: [4] Williams J, Fatemi A. Fatigue Performance of Forged Steel and Ductile Cast Iron Crankshafts. SAE International [5] Deshbhratar RJ, Suple YR. Analysis & Optimization of Crankshaft Using Fem. International Journal of Modern Engineering Research 2012; 2(5): [6] Wayzode RR, Mehar PG, Mujbaile VN. A Generalized Methodology for the Analysis and Simulation of Four Stroke Diesel Engine Crankshaft. Golden research thoughts 2012;1(x): 1-4. [7] Surappa MK. Aluminium matrix composites: Challenges and opportunities. Sadhana 2013; 28(1&2): [8] Mallikarjuna GB, Sreenivas Rao KV, Jayaprakash RH. Preparation and property evaluation of Aluminiumsilica composites by casting Route. International Journal of Mechanical Engineering and Robotic Research 2012; 1(3). Copyright 2013 Published by IJESR. All rights reserved 240