Simulation of Turning Process of AISI 1045 and Carbide Tool Using Finite Element Method

Transcription

1 Simulation of Turning Process of AISI 104 and Carbide Tool Using Finite Element Method 1 JAHARAH AG, 2 HENDRI Y, 3 CHE HASSAN CH, 4 RAMLI R, and YAAKOB Z Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi, Selangor, MALAYSIA 1 jaharah@engukmmy, 2 hendriynd@engukmmy, 3 chase@engukmmy, 4 rizauddin@engukmmy, zahira@engukmmy Abstract: - In recent years, the applications of finite element method (FEM) in metal cutting operations have proved to be effective in studying the cutting process and chip formation The simulation results is useful for both researchers and machine tool makers in optimising the cutting parameters and designing new tools This paper present the application of Finite element method (FEM) in simulating the effect of cutting tool geometries and cutting speed on the effective stress and temperature changes in turning AISI 104The tool geometries studied were various rake (α) and clearance (β) in the range of - to, and to 9 for α and β respectively, for cutting speed in the range of m/min, at constant feed rate of 03 mm/rev and depth of cut of 018 mm The effect of cutting speed on turning process was studied for cutting speed in the range of m/min, while the feed rate and depth of cut were kept constant at 03 mm/rev and 03 mm respectively The simulation simulation results show that the effective stress and cutting temperature on the cutting edge were between 1710Pa to 2040MPa and 880 C to 2080 C respectively while varying the tool geometries The simulation results also show that by increasing the cutting speed causes a decrease in effective-stress and increase the temperature of the chip formed to certain extend Key-Words: - Carbide tools, AISI 104, FEM, rake angle, clearance angle, cutting speed 1 Introduction Turning process is a common machining process to produce cylindrical shape parts Understanding of material removal concepts in metal cutting is very important in design process and cutting tool selection to ensure the quality of the products [1] Recently, the application of finite element method (FEM) in metal cutting process was a great help for researchers in study of metal cutting and chip formation Numerical simulation is usefull to study various phenomenon such as chip segmentation, cutting force, wear rate of cutting tool [2] Cutting tool working under specific numerical model are highly depended on the flow stress of work materials, ie tension models, tension rate and temperature, and the friction between the work material and the cutting edge [3] The geometry of the cutting tool is very important in determining the values of the cutting force [4] Machining parameters must be right and carefully selected to ensure the longer life of the cutting tool and therefore minimized the machining cost [ ] The cutting force is normally influenced by machining parameters; cutting tool geometries, and machining conditions and wear of cutting tool [ 6] The wear of the cutting tool was the critical issue in metal cutting as well as in turning of metal, consequently caused the tool failure [7] Numerical model is found to be a good, suitable and capable to forecast the effect of machining parameters such as wear of cutting tool, cutting tool failure and the machined surface [8] Finite Element Analysis (FEA) technique was the first introduced in 1960s and has been widely used to analyze in designing tools and forming processes Based on the success of FEM simulations for bulk forming processes, many researchers developed their own FEM codes to analyze metal cutting processes during the early 1980s up to now [1,9-10] Modeling tool wear using FEM has advantages over conventional statistical approach because it requires less experimental effort and it provides useful information such as deformations, stresses, strain and temperature in chip formation [11] This paper presents the application of Deform-3D in simulation orthogonal cutting process of AISI 104 and carbide tool at various combination of rake angle, clearance angle, and cutting speeds while the other ISSN: ISBN:

2 machining parameters of feed rate and depth of cut were kept constant 2 Methodology The commercial software Deform-3D for deformation analysis was used to simulate orthogonal metal cutting process It is based on an updated Lagrangian formulation and employs an implicit integration scheme The software is used to simulate the geometry of the cutting tool and machining parameters in turning the AISI 104 using uncoated carbide tool Simulation process is carried out by changing the rake, clearance angle, and cutting speed Later, the effective stress and temperature on the cutting edge are analysed Simulation is carried out to reach at steady state, which allowed the thermal to flow into the work material during the simulation of the cutting process The simulation is continued to reach the transient condition Tool stress analysis is performed to obtain stress data on the cutting tool Cutting tool will be fixed as an elastic and the force is interpolated so that the system will interpolate the force on the cutting tool to produce the resultant cutting force acting on the cutting edgework material is assumed to be a rigidviscoplastic in a rectangle shaped The cutting tool is classified as rigid body and will consider temperature transfer to model the cutting temperature Properties of stress flow, physical, and work material thermalmechanical are shown in Table 1 Table 2 shows the parameters used in the simulation process for studying the effect of tool geometries, and Table 3 shows the input parameters in studying the effect of cutting speed Table 1 Flow stress models for AISI-104 carbon steel Work material; AISI 104 (Oxley s Equation - ' (,, T ) ) [17] i) Flow stress data Tempera ture Strain Strain rate ii)thermal conductivity W/mK iii) Thermal expansion iv) Heat capacity v) Young modulus Table 2 Input parameters used in the simulation process for various tool geometries Parameters Rake angle ( ) Clearance Angle ( ) Cutting speed Feed Rate (mm/rev) 03 Depth of cut (mm) constant at 018mm Nose Radius (R n ) constant at 04 mm (mm) Heat transfer 01 N/s mm C coefficients at the workpiece- tool interface Table 3 Input Parameters in the simulation for cutting speed effect Parameters Cutting Speed Feed Rate Depth of cut at interval of 0 m/min Kept constant at 03 mm/rev Kept constant at 03 mm 3 Results and Discussions 31 Detailed Study of FEM Simulation Fig 1(a) shows the example of simulation result for displacement The longer the chip generation caused higher mesh displacement as shown at the end of chip formed The biggest deformation was occurred on the primary deformation zone, followed by the secondary deformation zone This cause higher stress occurred in this section This result is agreeable with findings from Kalhori [12], where the major deformation during cutting process was concentrated in two region, near to the cutting tool edge, and the biggest deformation was occurred in the primary deformation zone, followed by secondary deformation zone, sliding region and sticking region as shown in Fig 1(b) ISSN: ISBN:

3 increases the cutting temperature as discussed by Saglam et al [4] Table 4 Results for temperature and effective stress at various combinations of rake and clearance angles Rake angle, α, ( ) - Clearan ce angle, β, ( ) 9 Cuttin g speed (mm/ min) 300 Feed rate (mm /rev) 03 Temp eratur e ( C ) 2080 Effecti ve stress (MPa) (a) Displacement (b)effective-stress Fig 1 Simulation results for displacement and effectivestress at cutting speed of 100m/min, feed rate of 03 mm/rev and depth of cut of 03 mm 32 Effect of tool geometries on the effective-stress and temperature Finite element analysis is used to study the temperature changes and effective-stress with different combination of rake angle, clearance angle, cutting speed, and feed rate Table 4 shows the simulation results obtained for temperature and effective-stress by varying the rake and clearance angles It is found that the temperature increases when using negative rake angle According to Gunay et al [13], negative rake angle will increase the cutting force and therefore high heat will be generated The effective stress obtained from the simulation process is between 1710MPa to 2040MPa The minimum effective-stress is achieved at a combination of + of rake and +7 clearance angles This result is agreeable with the findings from Lo [14] According to him, the stress on the cutting edge will decreases with increases of rake angle Baradie [1] found that the optimum clearance angle for carbide tool is between -11 to + Small changes in clearance angle will greatly influence the wear mechanism and consequently the tool life Generally, at high cutting speed and feed rate will caused high temperature is generated According to Gunay et al [13], temperature at the cutting edge increases with increased in contact area between chips and the cutting edge According to Coelho et al[16], reducing the clearance angle while fixing the rake angle, will generate wear on the cutting edge, and therefore shorten the tool life Cutting with high clearance angle will cause bigger contact area between the cutting edge and the work material, consequently 33 Effect of Increasing of Cutting Speed on the effective-stress and temperature The effective-stress and chip temperature at various cutting speed were studied and analyzed as shown in Table Whereas, Fig 2 and Fig3 show the plot of these simulation results No Cut Speed Av Effectivestress (MPa) Av Tempera ture (C ) Fig2 shows that by increasing the cutting speed, it reduces the effective-stress This is also agreeable with theory and finding from Cerenitty et al [9] Fig3 shows that when the cutting speed increases, the generated temperature on chip also increases This result is also agreeable with Cerenitti et al [9], where the maximum temperature of the chip formed are increasing with increasing in cutting speed The increase of cutting speed from 100 m/min to 40 m/min resulted in increases of chip temperature from 16 o C to 83 o C This is due to the increase of required energy at high cutting speed More heat will be generated as cutting speed increases, consequently the maximum temperature on the tool and workpiece ISSN: ISBN:

4 surface increase at higher cuting speed From the theory, during machining, it is assumed that all the cutting energy is converted to heat and, therefore, a considerable amount of heat is generated at the following three distinct zones as given Fig 4, those are 1) Shear zone (7%); 2) Chip sliding on the tool face (20%); and c) Tool sliding on the workpiece machined surface (%) which is neglected for perfectly sharp cutting tools The maximum heat is produced at shear zone because of the plastic deformation of the metal, practically all of this heat is carried away by the chip [18] Fig 4 Heat generated and heat dissipation in metal cutting [18] Fig2 Effective-stress vs cutting speed at constant feed rate of 03 mm/rev and depth of cut of 03 mm 4 Conclusions From simulation result, the following can be concluded: 1 The minimum effective-stress and temperature on the chip formed of 1710 MPa and 880 o C are achieved at a combination of + of rake and +7 clearance angles 2 Increases in cutting speed while turning AISI 104 using carbide tool will decrease the effective- stress to 1400 MPa 3 The cutting temperature on the chips formed is increases with the cutting speed from 61 o C to 961 o C Acknowledgement The authors would like to Government of Malaysia and Universiti Kebangsaan Malaysia for their financial support under SF1214 and UKM-GUP-BTT Grants Fig3 Chip temperature vs cutting speed at constant feed rate of 03 mm/rev and depth of cut of 03 mm References: [1] CShet, and X Deng, X 2000 Finite element analysis of the orthogonal metal cutting process Journal of Materials Processing Technology 10: [2] D DUmbrello, LFilice, SRizzuti, FMicari, L Settineri, 2007 On the effectiveness of Finite Element simulation of orthogonal cutting with particular reference to temperature prediction Journal of Materials Processing Technology 189 (2007) [3] THC Childs, 1998 Material property needs in modeling metal machining, in: Proceedings of the CIRP International Workshop on Modeling of Machining Operations, Atlanta, Georgia, USA, 19 May 1998, [4] HSaglam, S Yaldiz, F Unsacar, 200 The effect of tool geometry and cutting speed on main ISSN: ISBN:

5 cutting force and tool tip temperature Materials and Design 28 (2007) [] WHYang, and YS Tarng, 1998 Design optimization of cutting parameters for turning operations based on Taguchi method, J Mater Process Technol 84 (1998) [6] NN Zorev, 1966 Metal cutting mechanics New York: Pergamon Press [7] DM Woodrow, 200 A tool wears comparative study in turning versus computer simulation in 1018 steel Brigham Young University [8] TOzel, and E Zeren, 2004 Determination of work material flow stress and friction for FEA of machining using orthogonal cutting tests Journal of Materials Processing Technology (2004) Piscataway, USA [9] Marusich, TD and Ortiz, (199), Modeling and Simulation of High-Speed Machining, International Journal Num Metallurgy Engineering In press [10] Cerenitti AE, Fallbohmer BP, W Wu CWT, Altan BT (1996), Application of 2D FEM to Chip Formation in Orthogonal Cutting, Journal of materials Processing Technology, 9: [11] Mackerle J (1999), Finite Element Analysis and Simulation of Machining: a Bibliography ( ), Journal of Materials Processing Technology, Elsevier Science, Volume 86 [12] Kalhori V 2001, Modelling and Simulation of Mechanical Cutting, Doctoral Thesis, Institutionen for Maskinteknik [13] MGunay, I Korkut, E Aslan, U Seker, 200 Investigation of the effect of rake angle on main cutting force [14] S P Lo, 2000 An analysis of cutting under different rake angles using the finite element method Journal of materials processing technology 10 : [1] MAEl Baradie, 199 The effect of varying the workpiece diameter on the cutting tool clearance angle in tool-life testing Wear 19: [16]RTCoelhoLR Silva, A Braghini, Jr AA Bezerra, 2004 Some effect of cutting edge preparation and geometric modifications when truning INCONEL 718TM at high cutting speeds Journal of Materilas Processing Technology 148 : [17] Oxley, P L B (1989) Mechanics of Machining: An Analytical Approach to Assessing Machinability, 1989, pp (Ellis Horwood, Chichester, West Sussex) [18] El-Hofy, H (2006), Fundamentals of Machining Processes: Conventional and Nonconventional Processes, Published by CRC Press, QEZpyCv4C&vq=cutting+speed&dq=af fecting,+temperature,+cutting+speed&so urce=gbs_summary_s&cad=0 on line 10/11/ 2008 ISSN: ISBN: