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http://www.iaeme.com/IJMET/index.asp 1120 [email protected]
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://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=9&IType=11
ISSN Print: 0976-6340andISSN Online: 0976-6359
© IAEME Publication Scopus Indexed
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://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=9&IType=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].
Ali Abbar Khleif and Ahmad Saad Jasim
http://www.iaeme.com/IJMET/index.asp 1121 [email protected]
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
The effect of Blanking Shear Angle on the Shearing Forces of Blanked Carbon Steel Sheets
http://www.iaeme.com/IJMET/index.asp 1122 [email protected]
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
Ali Abbar Khleif and Ahmad Saad Jasim
http://www.iaeme.com/IJMET/index.asp 1123 [email protected]
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
(E)
Tangent
modulus (Et)
Yield
stress(бy )
Poisson's
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.
The effect of Blanking Shear Angle on the Shearing Forces of Blanked Carbon Steel Sheets
http://www.iaeme.com/IJMET/index.asp 1124 [email protected]
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].
Aα �Lt
tanα
Sy � 2τmax
Fmax � AαSy
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.
Ali Abbar Khleif and Ahmad Saad Jasim
http://www.iaeme.com/IJMET/index.asp 1125 [email protected]
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°).
The effect of Blanking Shear Angle on the Shearing Forces of Blanked Carbon Steel Sheets
http://www.iaeme.com/IJMET/index.asp 1126 [email protected]
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°)
Ali Abbar Khleif and Ahmad Saad Jasim
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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.
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