International Journal of Theoretical and Applied Mechanics. ISSN 0973-6085 Volume 12, Number 2 (2017) pp. 331-342 © Research India Publications http://www.ripublication.com

Finite Element Analysis of an Aluminium Alloy Sheet in a V-Die Punch Mechanism Considering Spring- Back Effect

Shirish Ghimire1,a, Yogesh Emeerith2,b, Rohit Ghosh3,c, Sushovan Ghosh4,d 1, 2, 3, 4 B.Tech Students, Department of Mechanical Engineering, National Institute of Technology Durgapur, 713209, W.B, India

Dr. Rabindra Nath Barman5,e 5 Assistant Professor, Department of Mechanical Engineering, National Institute of Technology Durgapur, 713209, W.B, India

Abstract

Sheet metal parts are used to manufacture a wide range of products. Bending and cutting the sheets into appropriate shapes by means of the physical process of shearing is the very first step in forming such a part. The current work is an attempt to provide the readers with an appropriate understanding regarding the deformation behavior of an aluminium alloy sheet by performing the finite element analysis (FEM) for two distinct die angles. The metal sheet is analyzed before fatigue failure and with the help of a software based analysis; the paper explores the phenomena of spring-back, associated with the metal sheet during its deformation, while subjected to the set of V-die punch, designed with suitable dimensions. The V-die punch as well as the alloy sheet is modeled in Solidworks 13.0 and their dimensions have been taken from practical standards. Finite element analysis for the same is carried out in ANSYS Workbench 16.0 Keywords: Solidworks 13.0, ANSYS Workbench 16.0, V-die punch, Finite element analysis. 332 Shirish Ghimire et al

1. Introduction: Blanking and punching are one of the oldest manufacturing operations. Their applications range from components of very light to heavy appliances and machineries [1]. Punching is a metal forming process that uses a punch press to force a tool, called a punch, through the work piece to create a hole via shearing. When a specially shaped punch is used to create multiple usable parts from a sheet of material the process is known as blanking [2].During blanking, the part is subjected to complex solicitations such as deformation, hardening and crack initiation and propagation. The theoretical modeling of such processes is very difficult due to the complexity in describing the different stages of the whole shearing process starting with the elastic stage and ending with the total separation of the sheet metal [3] .Small punch test (SPT), Ball punch Test, Disk Bend test as well as Shear Punch Test [4-9] are the techniques developing to characterize the mechanical behavior of small specimens. The concept of the small V-die punching is based on placing a thin metal sheet specimen on the die and then the v shaped punch is applied to get the desired shape. In this process the feed is applied to the metal sheet horizontally and the punching is done vertically. In order to get the stable punching and the good punching edge quality of the al alloy and stainless steel alloy sheets [10], it is necessary to choose a narrow punch-die clearance and the heat sheet before punching. Reducing the clearance my increase the bright zone and also reduce the fracture zone as well as the fracture angle, but if the clearance is reduced the punching force and the tooling wear increases [11]. An experimental investigation had been carried out to study the effect of die angle on the quality of extruded product i.e. surface finish and hardness of cold extruded aluminum. The die angles used were 30, 45 and 60 ºs [12]. Similarly, deformation in copper was observed using ECAE technique under variable die angles. The die angles used were 90 º and 120 º for this research [13]. J. W. PILARCZYK and J. MARKOWSKI studied the effect of die angle on strain and stress state in process of drawing of steel for pre-stressed concrete keeping 8, 12 and 18 º dies for the process [14]. Similarly, five different die angles (15, 30, 45, 60 and 90) were used to investigate the extrusion behavior of wrought aluminum alloys [15]. Spring-back is a geometric change, that a sheet metal experiences after it gets rid of the tool forces in a punching process. Spring-back effect results in slight displacement of the sheet metal in the direction of the return stroke of the punch. Spring-back has a very significant role in sheet metal bending process. It leads to some geometric changes in the product. A research work was carried out for reflecting the different parameters on spring-back in U-die bending of different materials with different sheet thickness and tip radius [16].If not correctly predicted and compensated for, spring-back will cause the final part shape to deviate from design specifications and to create assembly problems [17]. H. Laurent conducted the Spring-back study of aluminum alloy in warm forming conditions. A split-ring test was used to analyze the influence of temperature during forming over Spring-back. The obtained experimental results were compared to the numerical simulations [18]. A research was done earlier which studied the spring-back effect in both V-die and U-die punching mechanism. Spring- Finite Element Analysis of an Aluminium Alloy Sheet in a V-Die Punch…. 333 back can only be controlled and minimized but quite difficult to be eliminated [19]. However, a new technique was proposed to eliminate the spring-back of high-strength steel (HSS) sheets in the U-bending process. In this technique, spring-back is eliminated using counter-punch [20]. The reason die angle change is to compensate for spring-back [21]. Friction plays a major role in metal forming processes because of its direct interaction with die and work-piece. Friction creates obstacles in the free movement and significantly affects the deformation of the work-piece. The co- efficient of friction should be specified at the die-work interface [22]. It was also seen that the punch load increases significantly with the increase in co-efficient of friction [23]. PANKAJ TOMAR also investigated the effect of friction at the die-billet interface for a commercially pure aluminum. However, this study was done for hydrostatic extrusion of aluminum [24]. In this analysis we are considering that metal sheets are homogeneous and neglecting the surface roughness.

2. Design Specification: To carry out this study, a 5mm thick plate of aluminum alloy was used as the sheet material. Structural Steel was used as the preferred material for both die and punch. The dimensions used in the study for the die and the punch are tabulated below.

334 Shirish Ghimire et al

ITEMS VALUES ITEMS VALUES Length 29.50 mm Length 79.70 mm Width 33.03 mm Width 19.21 mm Depth 19.70 mm Depth 19.70 mm Fillet 2 mm Nose Fillet 2 mm Die opening 23 mm

Table 2.1: dimensions for a 90º punch Table 2.2: dimensions for a 90º die

ITEMS VALUES ITEMS VALUES Length 29.50 mm Length 75.72 mm Width 33.03 mm Width 19.21 mm Depth 19.70 mm Depth 19.70 mm Fillet 2 mm Nose 2 mm Fillet Die opening 23 mm

Table 2.3: dimensions for a 120º punch Table 2.4: dimensions for a 120º die

3. Objectives: The objective of this study is to compare the deformations in the aluminum steel sheet obtained for two different die angles incorporating the spring-back effect with a software based analysis and to have an idea regarding the effective die-angle for the v-die punching process. The spring-back effect reduces with increase in die-angle and the objective of this study is to validate this fact and choose a suitable die for the v-die punching mechanism out of the two die angles used (90º and 120º). The study is carried out with the help of finite element method in the ANSYS Workbench 16.0 software.

4. Computational Investigation of V-die punching: 4.1 Model geometry: The following assumptions are made for the purpose of the present study: Finite Element Analysis of an Aluminium Alloy Sheet in a V-Die Punch…. 335

 To simplify the process we have taken the steady loading condition under plain strain condition, since in the usual blanking operation the punch-die clearance is very small.  It is a quasi-static process and hence the effect of plain strain rate is neglected.  The sheet metal is considered as the nonlinear plastic material, while the die and punch is the rigid bodies.  In this case we have compared the mechanical properties of the aluminium and stainless steel so our focus is only the simulation of the sheet metal. So we neglect the properties of punch & die. In this study the Cartesian co-ordinate system is placed at the midpoint of the sheet metal. We have done our study based on this co-ordinate system. The positive and negative sign only indicates the position of the element with respect to this coordinate system.

Fig 4.1: V-die punch model in Ansys 16.0

4.2 FEM (Finite Element Method): Numerical methods provide a general tool to analyze arbitrary geometries and loading conditions. Among this numerical analysis FEM (Finite Element Analysis) is used most extensively [25]. This kind of analysis requires the generation of the large amount of data to obtain the more accurate results and consumes huge investment of the computer resources and engineering time [26]. FEM is the good choice to analyze the sheet metal punching processes, since it helps to eliminate the need for the time and cost consuming experiments to optimize the parameters [27]. The finite element method gives an appropriate solution with an accuracy that mainly depends on the type of element chosen and the number of elements. We used the FEM to simulate the punching process in ANSYS 15.0, which is capable of solving the nonlinear behavior of the materials, deformations and stress-strain accurately.

336 Shirish Ghimire et al

4.3 Meshing: To perform the finite element method correctly we have to divide the metal sheet into very small elements i.e. mesh elements and then the simulation is done respectively. There are different types of method to perform the meshing process like Tetrahedron, Hex dominant, Sweep, Multizone etc. We in this study choose the Tetrahedron method. In this study 16804 elements and 31142 nodes are considered. The details of the meshing process are shown the figure below. To get the accurate result we divide the sheet metal into mesh element of sizing 1mm.

Table 4.3: Meshing ELEMENTS VALUES Meshing method Tetrahedron Elements 16804 Nodes 31142 Mesh element sizing 1 mm Minimum edge 0.5 mm length

Fig 4.3: Meshed model V-die punch model Finite Element Analysis of an Aluminium Alloy Sheet in a V-Die Punch…. 337

4.4 Simulation 4.4.1 Result and discussion for 90 º die: The Total deformation and the directional deformations along x, y and z axes are shown in the following fig. The analysis is performed by considering two nonlinear metal sheets of 5mm thickness when subjected to a load of 550 MPa at S.T.P.

Fig 4.4.1.1: total deformation for a 90º die

Fig 4.4.1.1: total deformation for 90 º die

Fig 4.4.1.2: directional deformation for 90 º die

Time is plotted along x axis and the variation of the total deformation is plotted along the y- axis. From this graphs, it is observed that the total deformation for both the metals increases almost uniformly and it’s parabolic in nature.

Table 4.4.1 : total and directional deformation for a 90 º die.

Die-angle ITEMS VALUES 1. Total deformation 10.048 mm (max) ; 0.38139 mm 90 º (min) 2 .Directional deformation 10.046 mm (max) ; 0.38129 mm (min)

338 Shirish Ghimire et al

4.4.2 Result and discussion for 120 º die: In a similar way, the deformation and the directional deformations for 120 º die along x, y and z axes are shown in the following fig. The analysis is performed by considering two nonlinear metal sheets of 5mm thickness when subjected to a load of 550 MPa at S.T.P.

Fig 4.4.2.1: Total deformation for 120º die

Fig 4.4.2.2: Directional deformation for 120 º die.

Time is plotted along x axis and the variation of the total deformation is plotted along the y- axis. From this graph, it is observed that the total deformation for both the metals increases almost uniformly and it’s parabolic in nature.

Table 4.4.2: total and directional deformation for a 120 º die.

Die-angle ITEMS VALUES 1. Total deformation 6.1095 mm (max) ; 0.18962 mm 120 º (min) 2 .Directional deformation 6.1094 mm (max) ; 0.18959 mm (min)

Finite Element Analysis of an Aluminium Alloy Sheet in a V-Die Punch…. 339

4.4 Conclusion: From this analysis we can see that the total deformation on the sheet metal for 90 º die is greater than that in case of 120 º die. Total deformation on the sheet metal for a 90 º die is 10.048 mm (max) and that when die angle equals to 120 º is 6.1095 mm (max). Similarly, the directional deformation on the sheet metal for a 90 º die is 10.046 mm (max) in the vertical direction and that when using a 120 º die is 6.1094 mm (max). Hence, we see that the deformation in the 90 º die is much greater than that in the 120 º die. After removal of the tool, the final directional deformation on the metal sheet for a 90 º die is 8.0578 mm and that when using a 120 º die is 5.1489 mm. For the 90 º die, a reduction of 1.9882 mm for directional deformation from the initials and a reduction of 0.9605mm for the 120 º die is obtained. Hence, we understand that the phenomena of spring back produces different effects for different die angles.With the increase in die-angle, the spring-back effect is reduced. In the present study it is found that, the spring-back effect for 120 º die is lesser than that for the 90 º die which validates the concept of spring back phenomena in the context of variable die angles. In addition to that, the spring-back effect being an unwanted effect, deformation in the 120 º die is the desired deformation and hence 120 º die would be the preferred one.

Table 4.4 : Conclusion Table For 90 º die For 120 º die ITEM NAME

Maximum Total Deformation 10.048 mm 6.1095 mm

Maximum Directional Deformation along y-axis 10.046 mm 6.1094 mm (initial)

Directional Deformation with Spring-back effect 8.0578 mm 5.1489 mm

Reduction in Directional Deformation 1.9882 mm 0.9605 mm

4.5 FUTURE SCOPE OF WORK Further investigation is needed to explore more parameters and operating conditions to develop a general model for more material types by using the combination of various techniques. A combination of techniques can be used in order to achieve a higher level of verification and to reduce the cost of the necessary experimental effort. It is recommended to experimentally perform the punching process that combines the optimal set of parameters and monitor its output quality. 340 Shirish Ghimire et al

REFERENCES [1] F.W. Timmerbil, Werkstatt. Maschin. 46 (1956) 58–66. [2] https://en.wikipedia.org/wiki/Punching [3] F. Faura, J. Lo´ pez, C. Lu´ is, M.A. Sebastia´n, and Blanking of stainless steel: tool life equation model, in: T. Altan (Ed.), Advanced Technology of Plasticity, vol. II, Columbus, OH, 1996, pp. 655–663 [4] Russell biagi, hilary bart smith,“imperfection sensetivity of pyramidal core sandwich structure” international journal of solids and structures 44 (2007) 4690–4706 [5] Sisheng yang, xiang ling, yangyan zheng, rongbiao ma, “creep life analysis by an energy model of small punch creeptest”,journalhomepage:www.elsevier.com/locate/matdes [6] Wen chun jiang, b. yang, b.y.wang, h. chen, j.m. gong, “experimental and numerical study on the residual stress in a lattic truss sandwich atructure: effect of geometrical dimension of punching die”journal homepage: www.elsevier.com/locate/matdes [7] Pusit mitsomwang, shigeru nagasawa,”effect of mechanical conditions on cutting characteristics of polycarbonate sheet subjected to straight punch/die shearing” (ICTP) 2014, 19-24 October 2014, Nagoya Congress Center, Nagoya, Japan, Procedia Engineering 81 ( 2014 ) 1145 – 1150 [8] Soumya subramoniana, taylan altana,n, bogdan ciocirlanb, craig campbellb, “optimum selection of variable punch-die clearance to improve tool life in blanking non-symmetric shapes” (IJMTM), journal homepage: www.elsevier.com/locate/ijmactool [9] E. falconnet, j.chambert, h. makich, g. monteil, “prediction of abrasive punch wear in copper alloy thin sheetblanking”journalhomepage:www.elsevier.com/locate/wear [10] L. komgrit, h. hamasaki, r. hino, f.yoshida, “elimination of springback of high strength steel sheet by using additional bending with counter punch” (JMPT),journalhomepage:www.elsevier.com/locate/jmatprotec [11] Debayan das, saurav rajgadia, anush karki, ankit basnet, pawan jaiswal, rakesh jaiswal, anupam raj jha, rabindra nath barman, “design and finite element analysis of connecting rod using solidworks and ansys workbench” (ijreat), Volume 3, Issue 4, Aug-Sept, 2015 ISSN: 2320 – 8791 [12] International Journal of Emerging Technology and Advanced Engineering www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 7, July 2012) Experimental Evaluation of Effect of Die Angle on Hardness and Surface Finish of Cold Forward Extrusion of Aluminum G. A. Chaudhari,S.R. Andhale, N.G. Patil Finite Element Analysis of an Aluminium Alloy Sheet in a V-Die Punch…. 341

[13] Effect of die angle on the deformation texture of copper processed by equal channel angular extrusion W.H. Huang a, L. Chang b, P.W. Kao a,*, C.P. Chang www.elsevier.com:locate:msea Materials Science and Engineering A307 (2001) 113–118 [14] J. W. Pilarczyk, J. Markowski FEM Analysis Of Effect Of Die Angle On Strain And Stress State In Process Of Drawing Of Steel For Prestressed Concrete [15] Extrusion Characteristics Dependence of Wrought Aluminium Alloy on Extrusion Variables S. O. Adeosun, Akpan E. I,*. Gbenebor O. P. American Journal of Materials Science 2013, 3(4): 77-83 DOI: 10.5923/j.materials.20130304.03 [16] Investigating Springback effect in U-Die Bending Process by varying different Parameters Jaydeep R. Shah*12, S. K. Sharma#1, B. C. Patel$1 #Associate professor, Mechanical Department $Assistant Professor, Mechanical Department *Research Scholar, Mechanical Department. [17] Creep and anelasticity in the springback of aluminum J.F. Wang a, R.H. Wagoner a,*, W.D. Carden b, D.K. Matlock c, F. Barlat. Elsevier. International journal of plasticity. [18] Mechanical Behavior and Springback Study of an Aluminum Alloy inWarm Forming Conditions H. Laurent,1, 2 J. Co¨er,1, 2 R. Gr`eze,1 P. Y. Manach,1 A. Andrade-Campos,3 M. C. Oliveira,2 and L. F.Menezes2 , International Scholarly Research Network ISRN Mechanical Engineering Volume 2011, Article ID 381615 [19] A Comprehensive Review of Experimental Approaches Used in the Measurement of Springback 1A.B. Abdullah, 2S.M. Sapuan, 1Z. Samad and 2N.A. Aziz [20] Elimination of springback of high-strength steel sheet by usingadditional bending with counter punchL. Komgrita,b,∗, H. Hamasakic, R. Hinoc, F. Yoshidac, Journal of Materials Processing Technology 229 (2016) 199–206, elsevier [21] http://www.thefabricator.com/article/bending/bending-basics-why-do-die- angles-changer [22] Prediction of coefficient of friction for Aluminum Billet Ajay Kumar Kaviti; Om Prakash and P. Vishwanath Kumar , Scholars Research Library Archives of Applied Science Research, 2011, 3 (4):328-335 [23] The effect of friction coefficient on punch load and thickness reduction in deep drawing process Sadık Olguner, A. Tolga Bozdana, INTERNATIONAL JOURNAL OF MATERIALS , Volume 3, 2016 342 Shirish Ghimire et al

[24] Theoretical Investigation of Friction at Die/Billet Interface in Hydrostatic Extrusion of Commercially Pure Aluminum, PANKAJ TOMAR, SCIENCE DIRECT [25] An Application of Finite Element Method and Design of Experiments in the Optimization of Sheet Metal Blanking Process Emad Al-Momani, Ibrahim Rawabdeh * [26] Haydn n.g. wadley, norman a. fleck, anthony g. evans, “fabrication and atructural performance of periodic cellular metal sandwich structures”. Composite scienceand technology 63 (2003) 2331-2343. [27] S. Maiti, A. Ambekar, U. Singh, P. Date, and K. Narasimhan, “Assessment of influence of some process parameters on sheet metal blanking”. Journal of Materials Processing Technology, Vol. 102, 2000, 249-256.