The Effect of Blanking Shear Angle on the Shearing Forces of Blanked Carbon Steel Sheets

International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 11, November2018, pp. 1120–1128, Article ID: IJMET_09_11_115 Available online at http://iaeme.com/Home/issue/IJMET?Volume=9&Issue=11 ISSN Print: 0976-6340andISSN Online: 0976-6359

THE EFFECT OF BLANKING SHEAR ANGLE ON THE SHEARING FORCES OF BLANKED CARBON STEEL SHEETS

Ali Abbar Khleif and Ahmad Saad Jasim Department of Production Engineering and Metallurgy University of Technology, Baghdad. Iraq.

ABSTRACT In this study, numerical analysis has been conducted to investigate effects of shear angle on shearforcefor a low carbon steel sheet (AISI 1008). Five model shave been used in the blanking tests; one conventional flat end punchand four different bevels sheared rooftop punches of (0 °, 5 °, 10 °, 15 °,and 20°), which comparator of top punches. For the selected finite elements method, three-dimensional models were created. A finite element technique (ANSYS Workbench 15)was used for simulating the blanking process. The results showed that the blanking forces could be reduced radically with ideal bevel punch geometry. By using 10° shear angle at the punch end, the cutting force wasdecreased up to (90.5%) compared to the ones of the traditional flat end tool. Keywords: FEA, A sys, sheet metal, blanking, shearing force, and a punch shear angle. Cite this Article: Ali Abbar Khleif and Ahmad Saad Jasim, The Effect Of Blanking Shear Angle On The Shearing Forces Of Blanked Carbon Steel Sheets, International Journal of Mechanical Engineering and Technology, 9(11), 2018, pp. 1120–1128. http://iaeme.com/Home/issue/IJMET?Volume=9&Issue=11 1. INTRODUCTION The sheet metal working operations are extensively used in nearly all industries like defense, automotive, mechanical and medicinal manufacturing. The main benefit for using metal working operation is to advance production rate and to decrease the price per part [1].One of the sheet metal working processes is blanking process; the blanking operation used in the industrial manufacturing establishes the first step of several forming processes. Blanking is the operation of shearing or cutting, from sheet-metal stock, a piece of metal of predetermined contour to attend it for subsequent processes [2].A significant challenge confronted when using blanking to machine sheet metal is the treatment of the shearing force in demand for thick stock and high strength. Increased shearing forces lead to the demand of higher accomplishment predictable from the conclusion in increased wear on the die and punch tool and pressing machine. One of the methods used to decrease the force wanted is the increase of a punch shear angle [3].

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There are many studies in the literature that deal with the scope of blanking process.One of the successful attempts was made by[4], gave the expansion of a pattern to portend the form of the cut side. The model studied the influence of possible parameters affecting the blanking operation and their interactions. This assisted in selecting the operation importantparameters for two conformable units fabricated from two various substances blanked with a plausible quality on the same mold. Finite Element Method and Design of Experiment process were utilizedso as to perform the objectives of purposed model. A collection for both systems was suggested to cause a decrease in the essential experimental price and potential in addendumfor obtaining a higher plane of realization. It can be expressed that the (FEM) fastened with Design of Experiments method supply a significant contribution across the optimization of sheet metal blanking operation. Mackensenet al. [5] offered potentials for decreasing these forces. Experimental studieshave beenconductedusing a novel tool concept that couldassociateessential blanking forces to punch stroke in three dimensions and indirect force path. The results from three various AHSS materials have been presented indicating the differencesindecisive blanking variablesfor example clearance, shearing angle and sheet positioning angle. Behrens et al.[6] invest gated concentrates effects on blanking of thin steel sheets of Dogal1000DP +Z100MBO. Experimental and numerical studies on the effect of punch speed and clearance on the cutting force and the sheared edge geometry have been performed. Tensile and compressive tests at raised temperature were selected for defining the flow and fracture attitude of Dogal1000DP +Z100MBO at various stresses situations. It was displayed that flow curve limited by stack compressive test guides to finer result in force-displacement foretelling of a blanking operation compared by tensile test for determining flow curve. Stress established fracture criterions have been selected for defining damage behavior. Furthermore,the significant effect of fracture locus for negative stress on the geometric of the numerical prophesied sheared edge was presented. Numerical and experimental studies were performed by Wang and Wierzbicki, 2015 [7]on the plane-strain blanking operation in an try to know how the blanking operation acts edge fracture. Blanking experiments on a DP780 steel sheet have been conducted for the Digital Image Correlation (DIC) deformation measurement on a particular fixture using an in-situ microscope. The DIC method supplies a specified deformation field of the sample that was not described in any another publication before. Discontinuous examinations havebeen performedfor investigating the crack creation and spread through the blanking process, although Scanning Electron Microscope (SEM) has been usedfor inspecting the surface quality of blank in addition to the edge profile after the experiment. After the experiment study, a specified (FEM) Model in the critical zone with mesh dimension of 0.01mm for the numerical study was establishing. With matter parameters standardized from the in-plane investigations in addition to precise edge conditions calculated in real examinations, the Finite Element model precisely estimated the blanking operation quantitatively. The present investigation provided quantitative amounts of the parameters of interest through the blanking examination, for example, the local strain inclination history and the universal load-displacement responses. The geometrical characteristics forblanked edge, the extent of the burnished zone and fracture region have been all precisely calculated using current simulation. Through the study of the blanking mechanism (Zhank et al., 2016) [8], it is found that the blanking clearance and the convex die cutting edge radius seriously influence the quality of fracture surface, the wear depth of the punch and the load of the punch. After establishing the appropriate models, finite element analysis software Deform-3D has been implemented for simulating the above forming parameters. The curves between the forming parameters and the quality of fracture surface, the wear depth of the punch and the load of the punch were obtained, optimizing the optimal forming parameters. On these bases, presents five solutions to improve the punch structure. It was found that the comprehensive performance of internal spherical punch is best by comparing the quality of fracture surface, the wear depth of the punch and the

http://iaeme.com/Home/journal/IJMET 1121 [email protected] The effect of Blanking Shear Angle on the Shearing Forces of Blanked Carbon Steel Sheets max principal stress of the punch. Kumari and Tagore, 2016[9] performed analytical investigations to optimize the factor sheet clearance,and material type for a sheet metal blanking die. Different values for each sheet clearance factor were taken and optimized on the basis of stresses and deformations produced. 3D models of the blanking die and total assembly were done in Pro/Engineer. The forces applied on the blanking die were calculated theoretically. Structural analysis was performed for differentblank materials SS and Aluminum. The analysishas been donebyusing ANSYS software. Patil and Kadlag, 2016[10] studied the influence of quality parameters affecting the blanking operation & their interaction. This helps to select the process leading parameters for similar work piece manufactured from two different materials blanked with suitable quality. Finite element method & taguchi method approaches are useful in order to achieve the required objective of the project. The combination of these two techniques provided a good solution for the optimization of sheet metal blanking process. The study helped to estimate the effect of sheet material thickness, tool clearance, and sheet material. It is useful that before manufacturing blanking die, to do Finite element analysis to know the parameters effect & go for feasible& result oriented design. The result from Taguchi method & finite element method is then validated with physically design blanking die. Engin and Eyercioglu, 2017[11]conducted FEM and experimental investigations for observingclearance effects on punch load, cutting energy and surface zone distributions. AISI 304 stainless steel with 2 mm thickness was blankedutlizing a 300 KN hydraulic pressurewith five virous clearance values (1%, 3%, 5%, 10% and 20% of thickness) for experiment studies. Deform 2D was used for modeling of the process. The results showed that if the purpose is to achieve good surface quality, less than 5% clearance should be used. If punch loads are the main concern, more than 5% clearance should be used. Also, the proposal of the cutting energy parameter and an optimal clearance value for AISI 304 was given in the scope of the work. 2. EXPERIMENTAL WORK The most considerable things to avoid a failure of the sheet metal cutting are matter kind and its characteristics. The properties of the substance to be cut having an important effect on the accomplishment of the blanking process. In the present work, (1008-AISI) a low carbon steel sheet metal was used which has a thickness of (t = 0.5mm). (1008-AISI) low carbon steel was chosen due to its suitable formability and in deep drawing application its widespread use such as fuel cistern, automobiles bodies, and other usages. The compositions have been listed in Table 1.

Table 1 Chemical Composition of (1008-AISI) Low Carbon Steel Sheet. C% P% Cr% Cu% Mo% Ni% S% Si% Mn% 0.07 0.016 0.036 0.04 0.003 0.039 0.027 0.015 0.33 By performing tensile tests,the mechanical characteristics of the blank can be determined. By utilizing a wire electro discharging machine samples can be cut consistent with description ASTM standard E8M pattern. The mechanical properties can be changed according to the rolling direction because the substance utilized here is fabricated by rolling operation, because of anisotropic behavior. Therefore, because regard to the rolling orientation the samples were selected at three orientations (0o, 45o and 90o). The tensile experiments are utilizing computerized general examination device(WDW-200E) and accomplished at velocity (2mm/min). Figure 1 shows the truestress-strain relationship at three different directions for low carbon steel sheets with 0.5mm thickness

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Figure 1 True Stress-Strain Relationship at Three Different Directions for Low Carbon Steel Sheets with 0.5mm Thickness From these tests can be getting for low carbon steel sheet metal on the mechanical properties are listed in Table 2. The results provided by this test are used to define the material parameters of the constituent model designated for the numerical simulation.

Table 2 Low Carbon Steel Sheets Metal Properties

Modulus of elasticity Tangent Yield Poisson's (E) modulus (Et) stress(бy ) Ratio (ν) 200(GPa) 0.5(GPa) 204 (MPa) 0.3 3. FINITE ELEMENT ANALYSIS In engineering, computational techniques can be utilized to get approximate solutions of border values problem called the finite element analysis (FEA), occasionally mentioned asfinite element method (FEM). Border values problems are mathematical problems in which one or more dependent variables should satisfy differential equations and satisfy certain situations on the border of the field anywhere inside a recognized field of independent variable. Border values problem is too occasionally named domain problem. The domain is the field of concern and predominately represents a physical structure. The differential equations can be governed the domain variable which is the dependent variable of interest. The Border State is the specific value on the borders of the domain of the domain variable (or connected variable for example derivative). The domain variable may contain to name only a few fluid velocity, heat flux, temperature, and physical displacement, depending on the kind of physical problems being investigated [12]. 4. NUMERICAL ANALYSIS In this research, A Finite Element technique(ANSYS Workbench 15)has be enutlized for simulating the blanking process. Together sheet metal and blanking tools have been simulated in three dimensional as shown in Figure 2.The methodwas used as an iterative solver in all cases.

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Figure 2 Sheet Metal and Blanking Tools. The shear stresses can be obtained from simulation by ANSYS Workbench 15. Hence,the maximum shear forces were computed by using the following equation [13]. L t Aα = tanα Sy = 2 τmax Fmax = Aα Sy Where: Aα = region of the cut, angular (mm2) tanα = sheared surface angle of the punch (Rad) L= cut length, linear (mm) t = material thickness (mm) Sy = the material yield strength (MPa)

Table 3

No. punch Angeles Aα (mm) τmax Sy F (KN) 1 0 78.54 463.09 463.09 36.37 2 5 15.67 232.97 445.44 6.98 3 10 7.774 227.32 454.07 3.53 4 15 5.116 416.06 832.12 4.25 5 20 3.766 589.49 1179 4.44 5. RESULTS AND DISCUSSIONS By implementing the numerical technique, blanking forces were specified in a blanking operation with clearances 0.03 mm. The friction coefficient is supposed to be fixed and equivalent to µ= 0.10.The punch stroke was adjusted to be 1,5,10,15,20 mm for angles0°,5°,10°,15°,20° Sequentially to guarantee that the parts were cut and extracted from the die. The experiments tests have been doneutilizing five various punch angles and one clearance. The result has indicated that shearing force was considerably influenced by a beveled punch with an oblique shearing.

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Through numerical simulation and by using the explicit dynamic analysis,the maximum shear stresseshavebeen found as shown in figures 3 to 7.The maximum shear force wascalculated fromthe equation above as shown in Figure8. By comparing the results from figures,it can be seen that byincrementof shear angle, the blanking force was continuously reduced.It was clear that the shear force for flat end punch number1 has a maximum value of 36.37 kN.When the shear anglewas increased to 5° in punch number 2, the force was decreased to 6.58 kN,and the differencewas 82%.While punch number 3 which has an angle of 10°, the shear force equal to 3.42kN and the difference was 90.5%.For punch number 4 which hasan angle of 15°, the shear force equal to 4.25kN,and the difference was 88%. When the shear angle was increased to 20° in punch number 2, the forceequal to 4.44kN,and the difference was 87.5%. It can be observed the shear force for flat end punch be maximum since cutting force assumes that the complete cut along the sheared limit amount is created at the one time. While, reducing the maximum force by using an angled cutting edge on the punch, the cut diffusions over time and decreases the force at any one instant. Also, with increasing shear angle the creation of force peaks decreases. When using a bevel ground punch, the blanking force was reduced by at least 90.5% compared to punches with a flat surface, as only a certain part of the die was engaged at any one time.

Figure 3 Maximum shear stress (kN) for the flat end punch.

Figure 4 Maximum shear stress (kN) for punch with a shearing angle (5°).

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Figure 5 Maximum shear stress (kN) for punch with a shearing angle (10°).

Figure 6 Maximum shear stress (kN) for punch with a shearing angle (15°)

Figure 7 Maximum shear stress (kN) for punch with a shearing angle (20°)

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Figure 8 Maximum shearing forces kN for the punch-die assemblies with a shearing angle(°) 6. CONCLUSION In this paper, the blanking of AISI 1008 low carbon steel metal with 0.5 mm thickness was cut. Investigations were performed by using the FEM method to observe the blanking shear angle influence on the shearing forces. When calculating blanking forces in particularwith light sheet metals, it can be observed that a machine was designed to have enough energy for blanking but not enough blanking force. In this situation, it is probable to decrease the blanking force by utilizing a beveled punch. In this numerical investigation, the punching forces of the conventional flat end punch were compared to the punching forces of the bevel sheared punches. The investigation showed that the cutting forces of the low carbon steel (1008-AISI) could be decreased significantly by utilizing ideal shearing angle of the punch. With the instruments and substances used in this investigation, the smallest calculated punching force was a mounted over 90.5 % compared to the punching forces of the conventional level end punch. Increasing in the shear angle also increased deformations, which caused warping of the work piece to ensure that the slug work piece remains flat. In blanking operations, bevel shear or double-bevel shear angles should be used on the punch. Hence, big shearing angle of the punch produced several passive characteristics to the blank quality. The application of the sheared blanks appoints the quality options,and this is why the most significant amounts of the shearing anglesare not desired. In this study, the shearing angle of 10° for punch 3 was the better middle solution among the cutting quality and the force drooping. There search was in evolved the blanking of low carbon steel. It could be extended for investigating other common materials for example copper, aluminum, and austenitic stainless steel. It could also be extended for investigating the impact of other parameters on blanking processes such as thickness, clearance between die and punch, lubrication and punch speed. REFERENCES

[1] Avadhani, S. P., Phadnis,P., Nikhil R and Patil, S. P. Design and Analysis of Blanking and Piercing die punch.International Research Journal of Engineering and Technology, 4, 2017, pp. 2760-5. [2] Black, B. J. Workshop processes, practices and materials.5th edition, London and New York :Routledge, 2015.

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[3] Gürün, H., Göktaş, M., andGüldaş, A. Experimental Examination of Effects of Punch Angle and Clearance on Shearing Force and Estimation of Shearing Force Using Fuzzy Logic. Transactions of FAMENA, 40, 2016, pp. 19-28. [4] Al-Momani, E., andRawabdeh, I. An application of finite element method and design of experiments in the optimization of sheet metal blanking process. JJMIE, 2, 2008, pp. 53-63. [5] Mackensen, A., Golle, M., Golle, R., & Hoffmann, H. Experimental investigation of the cutting force reduction during the blanking operation of AHSS sheet materials. CIRP annals, 59, 2010, pp. 283-286. [6] Behrens, B. A., Bouguecha, A., Vucetic, M., Krimm, R., Hasselbusch, T., & Bonk, C. Numerical and experimental determination of cut-edge after blanking of thin steel sheet of DP1000 within use of stress based damage model. Procedia Engineering ,81 ,2014, pp. 1096-1101. [7] Wang, K., &Wierzbicki, T. Experimental and numerical study on the plane-strain blanking process on an AHSS sheet. International Journal of Fracture, 194, 2015, pp. 19-36. [8] Zhang, Z. J., Chen, D. H., and Wang, Y. K. Study on Blanking of Thick Steel Plate and Failure of Punch. DEStech Transactions on Materials Science and Engineering, 2016. [9] Kumar M. V. and Tagore, K. R.Analytical Investigations to Optimize Factors Affecting the Sheet Metal Blanking Process, International Journal of Engineering Technology Science and Research,5, 2016, pp. 7014-6. [10] Patil, A. N., andKadlag, V. L. Blanking Process Optimization using Finite Element Analysis and Taguchi Method.International Journal of Science Technology andEngineering,2,2016, pp 553-562. [11] Engin, K. E. and Eyercioglu O.Purpose Oriented Clearance Selection in Blanking Process, European International Journal of Science and Technology,6 ,2017, pp.66-76. [12] Hutton, D. V.Fundamentals of finite element analysis, New York : McGraw-Hill, 2017, pp.1 [13] Suchy, I. Handbook of die design, NewYork :McGraw-Hill, 2006, pp.264-5

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