FATIGUE ANALYSIS OF COATED I.C. ENGINE CRANKSHAFT

Transcription

1 Vol.2 Issue.9,. FATIGUE ANALYSIS OF COATED I.C. ENGINE CRANKSHAFT M. Senthil kumar 1, Dr.S.Ragunathan 2, M.Suresh 3 Abstract 1 Asst.Professor, Dept. of Mechanical Engg.,Sona College of Technology, Salem. 2 Principal, Jayalakshmi Institute of Technology, Thoppur. 3 M.E, Engineering Design, Sona College of Technology, Salem. msksona@gmail.com ragusubramanian@gmail.com sureshmsona@gmail.com A survey was conducted on crank shaft used in heavy vehicles. It was reported that the failure has been identified at crankpin bearing location and in the pin contact region with the crank web. Mechanical and metallurgical properties of the crank shaft including chemical composition, metal structure were estimated through optical emission spectroscopy and EDAX with SEM images. The crankshaft model was designed through Pro-E with exact dimensions. Fatigue analysis of modeled crankshaft is done with ANSYS 14 workbench. Nickel and Alumina coating were provided over crank pin region of modeled crank shaft and their strength is estimated as solution to identified fatigue failure. The strength of the crankshaft before coating and after coating were compared and analyzed. Keywords-crankshaft, failure analysis, coating, finite element analysis, fatigue. 1. Introduction Crankshaft is the heart of an Internal Combustion Engine [1]. The reciprocating motion of Piston is converted into rotary motion by crankshaft. Crankshafts are generally subjected to torsional stress and bending stress due to self-weight or weights of components or possible misalignment between journal bearings. Crankshaft failures may be resulted from by several causes which are oil absence, defective lubrication on journals, high operating oil temperature, misalignments, improper journal bearings or improper clearance between journals and bearings, vibration, high stress concentrations, improper grinding, high surface roughness, and straightening operations. The crankshaft faults caused high cost of maintenance in automotive industry [2]. Farzin H et al [3], have conducted a dynamic simulation on a crankshaft of a single cylinder four stroke engine. Finite element analysis was performed to obtain the variation of stress magnitude at critical locations. The pressure-volume diagram was used to calculate the load boundary condition in dynamic simulation model, and other simulation inputs were taken from the engine specification chart. The dynamic analysis was done analytically and was verified by simulation in ADAMS which resulted in the load spectrum applied to crank pin bearing. This load was applied to the FE model in ABAQUS, and boundary conditions were applied according to the engine mounting conditions. The analysis was done for different engine speeds and as a result critical engine speed and critical region on the crankshaft were obtained. Stress variation over the engine cycle and the effect of torsional load in the analysis were investigated. Results from FE analysis were verified by strain gauges attached to several locations on the crankshaft. Results achieved from aforementioned analysis can be used in fatigue life calculation and optimization of this component. 11

2 S.M.Sorte et al [4], have analysed the stress and design optimization of a single cylinder crankpin of TVS Scooty Pep crankshaft assembly. Three-dimensional models of crankshaft and crankpin were created using Pro/ENGINEER software and ANSYS was used to analyze the stress status on the crankpin. The maximum deformation, maximum stress point and dangerous areas are found by the stress analysis. They concluded analytically that the value of Max.shear stress is 112N/mm 2 and Max. Bending stress is 180 N/mm 2 which is more than the value of allowable stress value of material without taking any factor of safety. The relationship between the crank rotation and force acting on crank pin would provide a valuable theoretical foundation for the material selection and design optimization of crankpin and engine design. R.M. Metkar et al [5], have published a review paper and it considers crankshaft as an important part of engine components, as forces which are acting on crankshaft are many and variable in nature. This paper presents an idea about research undertaken or completed on fatigue life of crankshaft, methods available and role of Finite Element Analysis (FEA) and experimental techniques used. Jian Meng et al [6],have done stress analysis and model analysis of four cylinder engine crankshaft using FEM. The three dimensional model of diesel engine crankshaft was created by Pro-e and also they analysed the vibration modal, the distortion and stress status of crank throw and they found the dangerous areas by stress analysis. The relationship between the frequency and the vibration modal was examined by the modal and harmonic analysis of crankshaft using ANSYS. They concluded that the maximum deformation appeared at the centre of crankpin neck surface. The maximum stress appeared at the fillets between the crankshaft journal and crank cheeks, and near the central point journal. The edge of main journal was high stress area. The failure was due to bending fatigue. Jamin Brahmbhatt et al [7], have conducted dynamic simulation of single cylinder four stroke diesel engine crankshafts. The three dimensional model of diesel engine crankshaft was created using solid works software. They analyzed the variation of stress magnitude at critical location by using FEM software. Simulation inputs were taken from the engine specification chart. The dynamic analysis was done using FEA software which resulted in the load spectrum applied to crank pin bearing. This load was applied to the FE model in ANSYS and boundary conditions were applied according to the engine mounting conditions. Stress variation over the engine cycle and the effect of torsion and bending load in the analysis were investigated. Von-misses stress was calculated theoretically and FEA. The relationship between the frequency and the vibration modal was examined by the modal and harmonic analysis of crankshaft using ANSYS. Ali Keskin et al [8], have gone for failure analysis of nodular graphite cast iron crankshaft used in petrol engine. They tested mechanical and metallurgical properties of the crankshaft including chemical composition, micro-hardness, tensile properties and roughness and were compared with the specified properties of the crankshaft materials. In the comparison, there were no metallurgical defects apart from slightly higher carbon content. All other measured values were within the specified values. The reason identified for the failure was the thermal fatigue because of contact of journal and bearing surface. This condition led to the formation and growth of fatigue cracks. The contact was resulted from defective lubrication or high operating oil temperature. S.Bhagya Lakshmi et al [9], have designed the crankshaft of Honda engine and assembled by connecting rod in Pro-e. The designed model of crankshaft was analysed using Pro-e by using its mechanism. The piston acceleration was calculated theoretically and compared with experimental result. The peak pressure acting on the engine crankshaft was 63 bar. The crank angle was calculated with respect to seconds as it takes sec for each stroke with two revolutions. This value was calculated using spread sheet. It became base for dynamic analysis using Pro-E. 12

3 2.FAILURE ANALYSIS Mechanical and metallurgical properties of the crankshaft including chemical composition, and microstructure were studied to understand the process of failure. A.CHEMICAL ANALYSIS OF CRANKSHAFT The test result from the OES Foundry master showed that the material used in the crank shaft is EN9 (070M55 or AISI/SAE 1055). Fig.1. Portion of Chemical composition measured COMPOSITION RANGE MEASURED Carbon % 0.52% Manganese % 0.76% Silicon % 0.25% Sulphur % 0.025% Phosphorous % 0.017% Table.1. Chemical Composition of crankshaft PROPERTIES VALUES Young s Modulus GPa Density 7850Kg/m 3 Poisson ratio Tensile stress Yield stress Mpa Mpa Hardness HB Table.2 Material Properties of crankshaft 13

4 INTERNATIONAL JOURNAL OF RESEARCH IN AERONAUTICAL AND MECHANICAL B.SEM IMAGE (SCANNING ELECTRON MICROSCOPE) Fig.2 SEM Image With Magnification 108x Fig.3. SEM Image with Magnification 500x Fig.4.SEM Image with Magnification 1.01k X Fig.5. SEM Image with Magnification KX 14

5 3/10/2014 3:38:45 PM Fig.6. SEM Image with Magnification 500 X The scanning electron microscope (SEM) uses a focused beam of high-energy electrons to generate a variety of signals at the surface of solid specimens. The signals that derive from electron-sample interactions reveal information about the sample including external morphology, chemical composition, and crystalline structure and orientation of materials making up the sample. SEM image shows chemical composition and crystalline structure of crankshaft materials at various magnifications. The material structure obtain from the SEM image is martensite. C.ENERGY DISPERSIVE X-RAY ANALYSIS (EDX) COMPOSITION ANALYSE EDAX REPORT Quantitative results 80 Weight% C O Mn Fe Fig.7. Energy Dispersive x-ray analysis image The material structure and compositions are found using energy dispersive x-ray analysis. The structure formed is martensite. The chemical composition test results are given below ELEMENT WEIGHT% ATOMIC% C K O K Mn K Fe K Totals Table.3. chemical composition 15

6 3. DESIGN CALCULATIONS A.ENGINE SPECIFICATION DESCRIPTIONS Engine Type DETAILS 4Stroke, 6 Cylinder, Air Cooled Displacement Bore and Stroke 97.2 cc Compression Ratio 17:1 Max. Power Max. Torque Transmission 104X 113mm rpm rpm 6 Speed, Syncro mesh Table.4. Engine Specification B.FORCE ANALYSIS OF 4 STROKE 6 CYLINDER DIESEL ENGINE Volume (V) = π.d2.l / 4 = π / 4x0.104^2 x = 9.599x10-4 m3 Mean Effective Pressure (Pmean) = P x 60 x n / N x V = 97x60x2/2400x9.599x10-4 = 5.05 Mpa Piston Load ( FL )= Pmean x Area = 5.05x8.0154x10^3 FL = 43 KN Crank effort (FT) Table.5. Details of crank effort 16

7 Where Crank effort (F T ) = F P. Sin ( + ) / Cos Piston Effort (F P ) = F L + F i + W R Maximum force on piston (F L ) = 43 KN Inertia force (F i ) =-m R x r 2 (Cos + (Cos2 / n)) Angular speed ( )= rad/sec Crank Radius (r) = m Connecting rod length (l) = m n = l/r = FINITE ELEMENT ANALYSIS (FATIGUE ANALYSIS) Finite element analysis is a computer based numerical technique for calculating the strength and behavior of engineering structures. Finite element analysis is a technique to simulate loading condition on a design and determine the design s response to those conditions. We used Pro-E as design software for modeling and analyzed using ANSYS- 14 work bench. A.MODELING The dimensions of the crankshaft is measured accurately (reverse engineering). By using these dimensions, model of the crank shaft was drawn using Pro-E software Fig.8. Pro-E model of Crankshaft Fig. 9. Pro-E Model of Coated crankshaft B.ANALYSISOF CRANK SHAFT 17

8 We used ANSYS-14 (WORK BENCH) software for analysis. The model was imported to ANSYS 14 work bench. Material property and S-N curve details are entered for the crankshaft (EN9).By doing reverse engineering process the crankshaft was measured and drawn in Pro E and imported to the Ansys 14 work bench. From fatigue analysis we obtained the result like deformation, equivalent stress, alternating stress, life and damage of crankshaft. Meshing was generated for coated crankshaft. Meshing is used to convert the single component into number of elements and nodes. This process increases the accuracy of result and can give us the stress and deformation value at any desired location. Fig.10. Meshed geometry of coated crankshaft Then boundary conditions were applied to the crankshaft. Arresting the bearing supports on both sides. Applying gas pressure on the top of the crank pin portion depends up on the firing order and angle of crank. In the ANSYS picture point A shows fixed support and other points B,C,D,E,F,G shows force acting on various crank pin (B F1:25000N,C F5:22000N,D F3:19000N,E F6:13000,F F2:8000,G F4:4000) Fig.11. Boundary condition applied to coated crankshaft B.1.ANALYSIS OF CRANK SHAFT WITHOUT COATING The value of von-mises stress spread across the crank shaft are indicated in colour bandwidth which has Red colour indicates maximum stress value as X10^8 Pa. 18

9 Fig.12. Equivalent Alternating Stress Of Non-Coated Crankshaft The stress is maximum at the fillet region of crankpin which is shown in RED colour. The maximum value of alternating stress is e8 Pa. Fig.13. Life of Non-Coated Crank Shaft The maximum life of crankshaft is 8e6 cycles and the minimum value is e6 cycles. Poisson ratio and density were given to material models. By doing fatigue analysis, we found that the life of crankshaft is finite and it is 5.63 x 10 6 cycles. In order to increase the life of the crankshaft, we have given coating of Al 2 O 3 and Ni to the crankshaft at crankpin portion. The material property of Alumina and nickel was given. B.2.ANALYSIS OF Al 2 O 3 COATED CRANKSHAFT Fig.14. Equivalent Alternating Stress of Al 2 O 3 coated crankshaft The red color shows that the Maximum Alternating stress value as e8 N/m 2 and the blue color shows that the Minimum Alternating stress value as e5 N/m 2. 19

10 Fig.15. Life of Al 2 O 3 coated crankshaft The blue color shows that the Maximum life value as 8e6 cycles and the red color shows that the Minimum life value as 7e6 cycles. B.3.ANALYSIS OF NICKEL COATED CRANKSHAFT Fig.16.Equivalent Alternating Stress of Ni coated Crankshaft The red color shows that the Maximum Alternating stress value as e8N/m 2 and the blue color shows that the Minimum Alternating stress value as e5N/m 2. Fig.17. Life of Ni coated Crankshaft The blue color shows that the Maximum life value as e6 cycles and the red color shows that the Minimum life value as 6.8e6 cycles. 20

11 5. RESULT AND DISCSSION We have chosen the heavy vehicle Engine Crankshaft for analysis of fatigue strength. From our analysis, the fatigue life of Non-coated crankshaft is 5.63x10 6 cycles. In order to increase the life of the crankshaft, we have given coating by Al 2 O 3 and Nickel. The life of Al 2 O 3 Coated Crankshaft is 7x10 6 cycles and Nickel coated Crankshaft is 6.8x10 6 cycles. By comparing the result Coated Crankshafts have better life than Noncoated crankshaft. 6. FUTURE WORK Non- Coated crankshaft Al 2 O 3 Coated Crankshaft Nickel coated Crankshaft Fatigue stress N/mm 2 Fatigue Life (cycles) 5.63x10 6 7x x10 6 Table 6.Comparison of fatigue life of coated and Non-coated crankshaft The coating of Nickel and Alumina on any material is found to be increasing its fatigue life which validates the claim of coating the material improve the fatigue life of crank shaft. Hence, the amount of increase in fatigue life on coated crank shaft is under experimental testing. REFERENCES 1. Silva.F.S. (2003), Analysis of a vehicle Crankshaft Failure, Pergamon, Engineering Failure Analysis, 10, Xue-qin Hou et al (2010), Fracture Failure Analysis of Ductile Cast Iron Crankshaft in a Vehicle Engine, ASM International. 3. Farzin H. et al (2007), Dynamic load and stress analysis of a Crankshaft, SAE International Journal, Sorte. S.M. et al (2013), Stress Analysis and Design Optimization of Crankpin, International Journal of science and Modern Engineering, Vol 1, Issue R.M. Metkar,V.K. Sunnapwar and S.D. Hiwase 2011, A Fatigue Analysis And Life Estimation of Crankshaft,International Journal of Mechanical and Materials Engineering (IJMME), Vol.6 (2011), No.3, Jian Meng, (2011), Finite Element Analysis of 4-Cylinder Diesel Crankshaft,Image Graphics and Signal Processing, 5, Jamin Brahmbhatt et al (2012), Design and Analysis of Crankshaft for Single cylinder 4-stroke Diesel Engine, International Journal of Advanced Engineering Research and Studies, Vol 1, Issue 4, Ali KESKIN et al (2010), Crack Analysis of a Gasoline Engine Crankshaft, Gazi University Journal of science, 23 (4):

12 9. BhagyaLakshmi.S, et al (2012), Dynamic Analysis of Honda Engine Crankshaft, International Journal of Engineering and Innovative Technology Vol.2, Issue Hassan Nosrati1, Seyedhadi Tabaiyan, Seyed mohammad mahdihadavi (2012), Effect of Nickel Pulse Electroplating Parameters on ST12 Steel,ISSN: ( ). 11. Imran M Quraishi,Mrs.Madhuvi S Harne (2012), Stress analysis and optimization of crankshaft under dynamic loading,issn Volume 3, Issue 3, pp Alfares. M.A. et al (2007), Failure Analysis of a Vehicle Engine Crankshaft, ASM International. 13. Becerra.J.A.et al (2011), Failure Analysis of Reciprocating Compressor Crankshafts, Elsevier, Engineering Failure Analysis 18,