Ijems v2is10009 by Allied Journals

International Journal of Engineering, Management & Sciences (IJEMS) ISSN: 2348 –3733, Volume-2, Issue-1, January 2015

Multi- Objective Optimization of Forging of an Automotive Component Ajit Kumar, Avinaw Pratik, Ashutosh Kumar  Abstract— Various process parameters such as Die temperature, Billet temperature, Flash thickness and Flash width affect the forging process differently, thus the optimization design of process parameters is necessary to obtain a good product. In this paper an optimization method for the connecting rod closed die forging is proposed based on the finite element method (FEM) and Taguchi method with multi-objective design. Preform design in forging processes is an important aspect for improving the forging quality and decreasing the production cost. Utilization of designing & simulation tool can reduce iterative & time consuming approaches. The objective of this paper is to obtain an optimal preform shape in the consideration of the influence of the metal flow deformation in closed die forging process. The goal of the simulation and optimization process is to minimize the forging load and produce defect-free forgings. The optimal shape of the billet that gives minimum forging load with complete die filling was obtained after several optimization iterations. Optimization of die temperature, billet temperature, flash thickness & flash width will be performed by DEFORM-3D. Die filling & less wear in the dies will be the required achievements. MINITAB15 software is used for the calculation of S/N ratio & graphs for optimization. Index Terms— DEFORM 3D, Finite element method, Hot die forging, Preform, Taguchi method.. I. INTRODUCTION

Metal forging technology plays an important role in manufacturing industry. Most of forging processes are very complex. Two or more forging stages are usually used to realize a sound final forging process design [1]. The automobile engine connecting rod is a high volume production, critical component. It connects reciprocating piston to rotating crankshaft, transmitting the thrust of the piston to the crankshaft. Every vehicle that uses an internal combustion engine requires atleast one connecting rod depending upon the number of cylinders in the engine. As the purpose of the connecting rod is to transfer the reciprocating motion of the piston into rotary motion of the Crankshaft [2]. Connecting rod is widely applied as an important component in most of the mechanical and automotive industry. In recent years, there has been an increased interest in the production of Connecting rod by the precision forming technique. This is because of their inherent Manuscript received January 09, 2015. Ajit Kumar, Foundry-Forge Technology, NIFFT RANCHI, RANCHI, India, Avinaw Pratik, Foundry-Forge Technology, NIFFT RANCHI, RANCHI, India, Ashutosh Kumar, Foundry-Forge Technology, NIFFT RANCHI, RANCHI, India,

advantages compared with conventional methods. The advantages include the excellent mechanical properties, less raw material, good tolerance, high productivity and cost savings. The precision forging of the Connecting rod is very complicated and various process parameters such as deformation temperature, punch velocity and friction affect the forming quality differently, thus the reasonable process parameter design is very important. Actually, for lack of theoretical instruction, the process parameters of Connecting rod precision forging were determined by repeated experiments with artificial experience, which consume a large amount of materials and time. As a result, the optimization of process parameters is significant to obtain the desired goals such as achieving good die fill quality, reducing the forging force, increasing the die life, obtaining favorable grain size [3]. Mechanical presses are displacement-restricted machines. Mechanical forging press provides opportunity for consistent forging results and offers high productivity and accuracy without requirements for special operator skills. Mechanical presses are replacing hammers in ever increasing numbers, not only because of environmental problems, but also because, in most circumstances, mechanical press forging is less costly than hammer forging [4]. The Finite Element Method (FEM) offers the possibility to design the entire manufacturing process on a computer. This leads to a reduction of the cost and time in process and tool design, tool manufacturing, and die try-out. In addition, it is possible to iteratively modify the process conditions in the simulation to find the best manufacturing conditions for a product [5]. Connecting rods are subjected to forces generated by mass and fuel combustion .These two forces results in axial load and bending stresses. A connecting rod must be capable of transmitting axial tension, axial compression, and bending stress caused by the thrust and full of the piston and by centrifugal force. Finite element (FEM) Model is a modern way for fatigue analysis and estimation of the component [6]. DEFORM 3D are capable of coupled modelling of deformation and heat transfer for simulation of cold, warm or hot forging process, Information on material flow, die fill , forging load, die stress, defect formation, Extensive material database for many common alloys including steel, aluminium, titanium and super alloys [7,10]. Computer modelling and optimization are used to significantly reduce time and costs of process design and to optimize the final material state. The ultimate goal of computer modelling in the forging process is to reduce procurement times from as much as 30 months to as little as 2 months with associated reductions in costs and defects[8]. The closed die forging process is often used to manufacture high quality mass production parts like connecting rods, crankshafts etc at moderate costs. In principle, forging operations are non-steady state processes,

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Multi- Objective Optimization of Forging of an Automotive Component

in which deformation of the material takes place under three Die temperature 250,300 & 3500c dimensional stress & strain conditions [9]. Preform design Friction coefficient 0.3(constant) before the finishing operation may not be necessary and economical in case of forging components of simple shapes. Forging equipment Mechanical press However, if the component has varied cross-section as in case Flash thickness 1.5,2 & 2.5 mm of spanner, connecting rod, brake, pedal lever etc. It is necessary to reduce or increase cross sectional area of the bar Ambient 30°C at desired points with a view to improve die life. This will temperature necessitate the preforming operation before finishing. The Flash width 6,8 & 10 mm design of preform using closed die-forging methods or special Die velocity 1.5 mm/sec forging machines are, therefore, important aspects of forging technology and greatly influence the economics of the forging process. This can only be ensured by adequate metal distribution in earlier impression. For designing preform, 1. DESIGN CONSIDERATIONS metal flow characteristics should be studied carefully. The preform shape is determined by the type of forging material and equipment used. The dimensions of the preform must be 1.1 STOCK SIZE CALCULATION:larger than those of the finished part in forging directions to The factors in estimating the stock size include the size and promote forging in the finishing operations by upsetting and shape of the forging, method of heating and method of not by extrusion [11]. This paper describes Sequential forging. The terms used in weight calculation are Approximate Optimization algorithms to optimize forging Net weight – it is the weight of forging as per the given processes using time consuming Finite Element simulations. dimension of the component. The sequential improvement aims at achieving an accurate Net weight = volume of forging × density of material solution of the global optimum with the lowest possible Volume of forging = 218118 mm3 number of FE simulation. Density of material = 7.86×10-6 kg/mm3 II. METHODOLOGY Net weight of forging = volume of forging*density of material = (218118/1000000)*7.86=1.71 kg The goal of the simulation is to find out the shape of the billet Flash loss is the loss of extra material comes out when the top that leads to a minimum forging load and complete die filling and bottom die block has filled. It is determined by flash without any defects. The automotive component selected for thickness and flash width. the simulation purpose is connecting rod. Firstly, optimized Flash loss= 15 to 20 % of net weight =0.342 kg preform is designed with the help of the method of preform Gross weight is the amount of material required to fabricate a design. Preform, upper die & lower die are prepared by using forging. CATIA V5R19. Study of the influence of design related Gross weight = net weight +losses = (1.71+.342) kg = 2.052 variables on output performance characteristics are time kg consuming and costly during the real-time forging process. In Yield % = (1.71/ 2.052)* 100 = 83% this paper the effect of design parameters viz. Die temperature, Billet temperature, Flash thickness and Flash 1.2 FLASH DESIGN:width on preform has been studied in order to obtain The purpose of the flash is to control the metal flow within the minimum forging load with complete die filling along with die cavity. The flash normally cools faster than the main body minimum material loss by using FEM based DEFORM 3D of the forging and hence results resistance in metal flow V6.1 to simulate and validate the optimum result. Final part outwards. The consequence of this flow restriction, metal is forced to take an alternative route, the path of least resistance, and its die are as shown in Fig. 1 and Fig. 3. As DEFORM which normally results in filling dipper die cavities. The flash accepts only ‘.STL’ files, upper die, lower die and billets are thickness and width is directly related to the amount of waste saved with ‘.STL’ extension. Then, Minitab 15 software is material, acts as a pressure release valve for the almost used to form the orthogonal array formation as design of incompressible work metal and restrict the outward flow of the metal so that remote corners and deeper cavities can be experiments. filled up. The flash depression can be in either die or in both dies. Thus design of flash dimensions plays a vital role in Table.1. The component details & input data metal filling. While designing for flash, care must be taken in selecting flash thickness, as thickness being small will Material of billet AISI 1045 STEEL necessitate greater energy or extra blows to bring forging to size, on the other hand thickness being more may cause Mesh type Tetrahedral inadequate die filling. Thus a balanced condition is needed No. Of elements 50000 with just enough volume of metal to ensure that the flash thickness provided would force the work-metal to fill the Die material H13 impression properly without causing excess wear and Billet temperatures 1050,1150 & 1250 0c pressure. Component drawing + Finish allowance = Forging drawing

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International Journal of Engineering, Management & Sciences (IJEMS) ISSN: 2348 –3733, Volume-2, Issue-1, January 2015

As per IS: 3469:Finish allowance upto 200 mm length of component = 1.5 mm/surface By BRUCHANOV & REBELSKII formula, Flash thickness, t=0.015√A Plan area, A = 10345 mm2 So, t=1.525 mm Draft angles for Height of component, H <12 mm =10 For H=12-25 mm, 30 0 0 So, 1 & 3 drafts are taken. Flash thickness , t = 1.525 mm Flash width, b=4t=4*1.525= 6.1 mm Gutter thickness, t1 = 3t= 4.575 mm Gutter width, b1 = 4b = 24.4 mm S1= Plan projected area including flash land=10363.6 mm2 Equivalent diameter = 114.8 mm Net weight of forging = 1.71 kg

III. PREFORM DESIGN

1.3 DIE DESIGN:Length of the die block=2.5 * length of impression=2.5*195= 487 mm Width of die block= 2.5* width of impression= 2.5*128=320 mm Height of die block= 2.5*height of impression=2.5*30=75 mm EQUIPMENT SELECTION:S1= Plan projected area including flash land=10363.6 mm2 Dred = Reduced diameter of circular forging including flash land=1.13(S1)1/2=115 mm σ = Tensile strength at forging temperature = 6.5 kg/mm2 Lmax= Maximum length of forging at parting plane = 195 mm B= average width of forging including flash land= S1/Lmax=53.14 mm For non-circular forging, P=8[1-0.001Dred]*[1.1+20/Dred]2*S1* σ =772586 Kg P’=P*[1+0.1*0.20]=788 Tons So, Mechanical press of 788 tons can be used.

Preform design is one of the most important aspects in metal forming process design. Preform impression allows adequate metal distribution in the final impression. Thus, defect-free, complete die fill and small metal loses into flash can be achieved by a properly designed preform. If the component has varied cross-section as in case of spanner, connecting rod, break, pedal, lever etc. it is necessary to reduce or increase cross sectional area of the bar at desired points with a view to improve die life. This will necessitate the preforming operation before finishing. For better quality forging productions, care must be taken that in the finishing impression to minimize deformation to achieve final shape. Traditionally, the preform design is based on empirical or approximate analysis, requiring time consuming and expensive trial-and–error. Hence it is necessary to optimize the perform design in order to minimize the above drawbacks. The following procedure is used to design preform impression from forging drawing: The plan and the elevation of forging are laid out to full scale.  An estimated outline of the flash of the forging preside is than laid out.  The forging is then divided into various element based on geometric shape.  Vertical lines are drawn through largest and smallest cross sectional area of each element found as above.  The area of the above cross section is calculated and to each such area, cross sectional area of flash is added (flash width× flash thickness).  From the base line of above measurement are plotted and connected with smooth line, then the cross sectional area of perform at each line is determined.  The diameter “D” of the perform is evaluated at each element using the below equation:

Fig.2. Preform design for Connecting rod

Fig.1. Component drawing using CatiaV5

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Multi- Objective Optimization of Forging of an Automotive Component

Table.2. Calculation of Equivalent dia ‘D’ at various section (all dimension are in mm) SECTIONS

Fig.3. Preform Design and Die Design Using Catia D= (4xA/π) (1/2) Where D = equivalent diameter & A = Total area (flash area + job section area) Thereafter, the dimension D is symmetrically plotted about the reference line. These points are finally connected with a smooth curve as shown in Fig.3. A perform impression having this as an approximate contour can provide smooth flow of metal from blank into perform and finally finisher impression. For the present work 9 such performs and their dies were designed for different values of flash thickness, flash width corner and fillet radii.

CROSS SECTION

TOTAL AREA

EQIVALENT DIAMETER

X COORDINATE

Y COORDINATE

0*0

26*1.5

7.04

3.52

38*30

1140

38.1

19.05

51*30

1530

44.14

22.07

54*30

1620

45.42

22.71

55*30

1650

45.84

22.92

56*30

1680

46.26

23.13

57*30

1710

46.67

23.34

57*30

1710

46.67

23.34

57*30

1710

46.67

23.34

59*30

1770

47.48

23.74

60*20

1200

39.09

19.545

62*20

1240

39.74

19.87

63*20

1260

40.06

20.03

65*20

1300

40.69

101

20.345

66*20

1320

41.00

116

20.50

86*20

1720

46.80

124

23.40

126*20

2520

56.65

134

28.325

126*20

2520

56.65

145

28.325

126*20

2520

56.65

155

28.325

126*20

2520

56.65

160

28.325

126*30

3780

69.39

165

34.695

100*30

3000

61.81

170

30.9

97*30

2910

60.88

175

30.44

87*30

2610

60.84

180

30.42

84*1.5

126

12.66

192

6.33

0*0

195

IV. FEM- BASED PROGRAM DEFORM Deform consists of three parts A. Pre-processor The pre-processor includes (i) an input module for iterative data input verification, (ii) an automatic mesh generation program which creates a mesh by considering various process related parameters such as temperature, strain, strain-rate a well as die and work piece geometry; and (iii) an interpolation module that can interpolate various simulation results of an old mesh onto a newly generated mesh. The combined and the automated use of the modules for automatic mesh generation and interpolation, called automatic remeshing, allow a continuous simulation of a forming process without any intervention by the user, even if several remeshings are required. This automatic remeshing capability drastically reduces the total processing time of finite element analysis. All the input data generated in the pre-processor can be saved (i) in a text form which enables the user to access the input data through any text editor; and/or (ii) in a binary form which is used by the simulation engine explained below.

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International Journal of Engineering, Management & Sciences (IJEMS) ISSN: 2348 –3733, Volume-2, Issue-1, January 2015 V. TAGUCHI EXPERIMENTAL DESIGN B. Simulation The actual FEM-based analysis is carried out in this portion of Taguchi design of experiment is a powerful analysis tool for DEFORM. This simulation engine is based on a rigid-plastic modeling and analyzing the influence of control factors on FE formulation and can handle a multiple number of billets performance characteristics. The most important stage in this (either dense material or porous material, or combination of method lies in the selection of control factors. Billet these materials) and dies (either rigid or linear elastic) with temperature , die temperature, flash thickness & flash width non-isothermal simulation capability. The simulation results are the main parameters which influences the forging process are stored in binary form and accessed by the user through the of any component. These parameters each at three levels are post-processor. considered for the present study. The operating conditions C. Post processor under which test are carried are shown in Table 3. The post-processor is used to display the results of the The total degree of freedom (DOF) for four factors each at simulation in graphical or alphanumeric form. Thus, available three levels is 8. Therefore L9 orthogonal array is selected for graphic representations include (i) FE mesh; (ii) contour plots experimental design and is shown in Table. Simulations are of distributions of strain, stress, temperature etc., (iii) velocity run as per Taguchi experiment plan based on the experimental vectors, and (iv) load-stroke curves. Two other useful layout depicted in Table, and respective value of forging load capabilities in the post-processor are (i) ‘point tracking’, for each simulation run are converted into their respective S/N which provides deformation histories of selected points in the ratios as per equation below and are given in Table. Since, our workpiece throughout the deformation; and (ii) ‘flownet’, main objective is less forging load with complete die filling which allows the user to observe the deformation of circles or therefore smaller the better function is chosen. rectangles ‘inscribed’ on the undeformed workpiece for any Objective Function: Smaller-the-Better desired step through the simulation [10,12]. S/N Ratio for this function: Table.3. Factors and their levels Factors Symbol Level Level Level Unit 1 2 3 Billet BT 1050 1150 1250 0C temperature 0 Die DT 250 300 350 C Where, n= Sample Size, and y= load in that run. temperature Flash FT 1.5 2.0 2.5 mm SIMULATION TRIAL 1 thickness Flash width FW 6 8 10 mm

SIMULATION TRIAL 2

Fig.4. Process Flow Diagram

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Multi- Objective Optimization of Forging of an Automotive Component

SIMULATION TRIAL 6

SIMULATION TRIAL 3

SIMULATION TRIAL 4

SIMULATION TRIAL 7

SIMULATION TRIAL 5 SIMULATION TRIAL 8

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SIMULATION TRIAL 9

International Journal of Engineering, Management & Sciences (IJEMS) ISSN: 2348 â&#x20AC;&#x201C;3733, Volume-2, Issue-1, January 2015

Fig.5. Simulation trials of a process from 1 to 9 Fig. (a) Billet temperature (b) Die temperature (c) Flash thickness (d) Flash width

After conducting the experiments according to Taguchiâ&#x20AC;&#x2122;s experimental design we observed that in experiment no. 1, 2, 4, 5, 7, 8 & 9 the problem of underfilling occurred. In experiment no. 1 & 2, this may be due to less die temperature and billet temperature. In experiment no. 4, flash width is high & in experiment 5 flash thickness is high. In experiment 7 flash thickness is high & in experiment 8 flash width is very high. In experiment 9, die temperature & billet temperatures are high. Table.4 L9 Orthogonal array with their response

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Multi- Objective Optimization of Forging of an Automotive Component

In the above graph, load in different simulation trials is drawn. But, only in simulation trial 3 & 6 complete die filling occurred. So, respective loads are 1.83 * 105 klb & 4.7* 105 klb. So minimum among both i.e. 1.83 * 105 klb is the optimum load value. Data analysis is made using MINITAB15 software. Main effect plot is used to determine the optimum factor levels for minimum forging load, which BT level-3(1250 0C, DT level-2(3000C), FT level-1(1.5 mm) and FW level-1 (6 mm) are corresponding to the largest values of S/N ratio for all control parameters. Table 5. Results comparison Theoretical results Billet Temperature Die Temperature Flash thickness Flash width

1230°C

Simulated results 1250°C

1.525 mm

Billet Temperature Die Temperature Flash thickness

6 mm

Flash width

8 mm

205-315°C

connecting rod”, Journal of Materials Processing Technology, 59, pg no.95-105, 1996 [6] Ajit Kumar Senapati, Gopal Krushna Mohanta, “Optimization of Connecting rod by using non-linear static finite element analysis”, VSRD International Journal of Electrical, Electronics & Communication Engineering, Vol.III, Issue XII, 2013 [7] Hyunkee kim, Kevin Sweeney , t altan , “ application of computer aided simulation to investigate metal flow in selected forging operations”, journal of material processing technology, vol 46, 1994, page no 127-154. [8] Michael L. Chiesa, Reese E. Jones, Kenneth J. Perano, Tamara G. Kolda, “Parallel Optimization of Forging Processes for Optimal Material Properties”, Materials Processing and Design: Modelling Simulation and Applications, CP712, NUMIFORM 2004. [9] Taylan Altan, Victor Vazquez, “Status of Process Simulation using 2D and 3D finite element method”, Journal of Material Processing Technology, Vol. 71, 1997, page no. 49-63. [10] Deform 3d user manuals,. scientific forming technologies corporation ohio, 2000, page no. 1-182. [11] SN Prasad, “Criteria for equipment selection & perform design for forging”, Proceedings of the international seminar on metal forming technology, today & tomorrow”, Organized by iim at NIFFT, Ranchi, April 12-13th, 1980. [12] G.D. Satisha, N.K. Singh,1, R.K. Ohdar, “Preform optimization of pad section of front axle beam using deform”, Journal of materials Prcessing Tech,203, 102-106 ,(2008)

300°C 1.5 mm

VI. CONCLUSION FEM-based computer simulation has been used to optimize the design parameters viz. as Die temperature, Billet temperature, Flash thickness and Flash width on perform shape of connecting rod using Taguchi method, design parameters were optimized individually for forging load. The conformation experiment was conducted by taking the optimized value (output of Taguchi, s experiment) and was simulated once again. The results shows that at optimum factor level setting complete die filling is achieved with minimum forging load. It is found that optimization can be achieved quickly and efficiently through the use of simulation software. Modelling provides more information about the process i.e. load requirement and metal flow at different stages of the process. These techniques are also cheaper than performing tryouts with actual dies and equipments. From the above table we conclude that the theoretical results matches well with the simulation results.

Ajit Kumar-M.Tech. (Foundry-Forge Technology) from NIFFT Ranchi in 2013 and B.Tech (Production Engineering) from BIT Sindri Dhanbad in 2011. Paper entitled “Effect of section thickness on microstructure and hardness of grey iron”Published in IJERTVol. 3 Issue 7, July – 2014 Avinaw Pratik- M.Tech. (Foundry-Forge Technology) from NIFFT Ranchi in 2013 and B.Tech (Mechanical ) from RVSCET Jamshedpur. Paper entitled “Effect of section thickness on microstructure and hardness of grey iron”Published in IJERT Vol. 3 Issue 7, July – 2014 .

Ashutosh Kumar- M.Tech. (Foundry-Forge Technology) from NIFFT Ranchi in 2014 and B.Tech (Production Engineering) from BIT Sindri Dhanbad in 2008.

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