International Journal of Computational Engineering Research(IJCER)

International Journal of Computational Engineering Research||Vol, 03||Issue, 9||
||Issn 2250-3005 || ||September||2013|| Page 36
Computational Analysis and Design for Precision Forging
Of Aluminium AA 6061 Connector
Santhosh.N 1*
, Vinayaka.N #
, Dr.Aswatha $
, Uday.M €
, Praveena.B.A #
*
Assistant Professor, Department of Aeronautical Engineering, NMIT, Bangalore
#
Assistant Professor, Department of Mechanical Engineering, NMIT, Bangalore
$
Associate Professor, Department of Mechanical Engineering, BIT, Bangalore
€
Assistant Professor, Department of Mechanical Engineering, SJBIT, Bangalore
I. INTRODUCTION:
There has been a growing importance for precision forging of various components like Aluminium AA
6061 connector shown in Fig 1, which would otherwise have been produced by die casting processes or other
metal forming processes that have many disadvantages compared to precision forging process [1].Precision
forging is a unique technique with a goal to produce a net shape, or at least a near-net shape, in the as-forged
condition. The term net describes that no subsequent machining or a minimal of secondary finishing operations
on the forged component is required. Thus, a net shape forging or precision forging process aims at minimizing
the cost and waste associated with post-forging operations. Therefore, the final product from a precision forging
needs little or no final machining. Significant cost savings are achieved from the optimized use of material,
resulting in the overall reduction of energy consumption. Precision forging also requires less of a draft, I.e. 1° to
0°. However the downside of this process is its cost; therefore it is only implemented if significant cost
reduction can be achieved [2-4]. The main problem for forging process is the high cost and long lead time for
the design and production of tooling. For this purpose, CAD, CAM and CAE techniques are used to get faster
results in the design and manufacture of tooling by decreasing the trial and error time to produce successful
forgings [5]. CAD, CAM and CAE programs also develop satisfactory die design for the required process
parameters. 3-D modeling of forging dies is usually made with the aid of CAD software such as
Pro/ENGINEER, CATIA, and SOLID WORKS etc. If there are any problems in the simulation of the process
then the designer of the forging process can easily change his design parameters in the CAD software packages
[6]. The usage of process simulation programs is common for research and development of forging processes.
By using this type of programs, forging tool designer can decrease costs by improving achievable tolerances,
increasing tool life, predicting and preventing flow defects, part properties [7]. In this context it is proposed to
carry out the flow simulation of the entire precision forging process and examine the flow simulation results
obtained.
Finite Volume Method is a simulation method in which the grid points are fixed in space and the
elements are simply partitions of the space defined by connected grid points. The finite volume mesh is a fixed
frame of reference. The material of a billet under analysis moves through the finite-volume mesh; the mass,
momentum, and energy of the material are transported from element to element. The finite-volume solver,
ABSTRACT
Development of a new process methodology which satisfies given criteria is a big challenge
faced by most of the forging industries. The domain of competition is quite large and hence every firm
aims at producing near net shapes thereby eliminating the need for machining and other secondary
operations. The present investigation deals with the flow simulation of Aluminium forgings conforming
to AA 6061 specification and henceforth studies the mechanical characteristics of the flow simulation
results. The Aluminium AA 6061 component considered is precision forged with a hydraulic press in a
die having geometrical interlocking. During precision forging it was difficult to achieve the required
net shape of the component because of unsymmetrical location of small ribs on cylindrical surface and
variation in the cross sections from bottom to top (i.e. unsymmetrical about both X & Y axis). Thus to
eradicate the problem encountered, the flow simulation of the precision forging process was carried
out and the mechanical characteristics of the flow simulation results obtained were studied.
KEYWORDS: Flow simulation, Precision forging, Mechanical characteristics, Hydraulic press,
Billet, Component.

Computational Analysis And Design…
therefore, calculates the motion of material through elements of constant volume, and therefore no re-meshing is
required [8]. The most common finite volume software’s used in forging are MSC Super Forge and Deform 3D
to predict the forging variables. Deform 3D is very supportive in optimizing the forging process and defining its
parameters. Forging process can be simulated, Problems related with Product and Process design can be
observed easily, Various dies can be tried and forging process can be analyzed closely by using Deform 3D.
After a number of simulation processes involving different parameters, optimum die set for which the die cavity
gets filled completely while maintaining a lower stress can be selected by using Deform 3D [9].
Fig 1 Model of the component Fig 2 Aluminium AA 6061 billet
II. MATERIAL AND METHODS:
The present investigation examines the intricacies involved in the precision forging of Aluminium AA
6061 billet as shown in Fig 2 into the component as shown in Fig 1.Aluminium alloy 6061 is one of the most
extensively used of the 6000 series Aluminium alloys. It is a versatile heat treatable precipitation hardening
extruded alloy containing magnesium and silicon as its major alloying elements with medium to high strength
capabilities [10].
Table 1: Composition of Aluminium AA 6061
Element Weight %
Aluminium (Al) Min 96.4 to Max 97.9
Silicon (Si) Min 0.40 to Max 0.8
Copper (Cu) Min 0.15 to Max 0.40
Magnesium (Mg) Min 0.8 to Max 1.2
Chromium (Cr) Min 0.04 to Max 0.35
Manganese (Mn) Min 0.04 to Max 0.15
Zinc (Zn) Max 0.25
Titanium (Ti) Max 0.15
Iron (Fe) Min 0.15 to Max 0.7
Other elements not more than 0.05% each 0.15 total
Flange
Rib

2.1 Aluminium AA 6061
Aluminum AA 6061 is a silver white alloy that has a strong resistance to corrosion and like gold, is
rather malleable. It is a relatively light metal compared to metals such as steel, nickel, brass, and copper with a
specific gravity of 2.7. Aluminum AA 6061 is easily machinable and can have a wide variety of surface finishes.
It also has good electrical and thermal conductivities and is highly reflective to heat and light, henceforth
Aluminium AA 6061 alloy has wide applications ranging from aerospace to marine engineering [11].
2.2 T6 Temper Grade
T6 temper Aluminium AA 6061 has an ultimate tensile strength of at least 42,000 psi (300 MPa) and
yield strength of at least 35,000 psi (241 MPa). More typical values are 45,000 psi (310 MPa) and 40,000 psi
(275 MPa), respectively. In thicknesses of 0.250 inch (6.35 mm) or less, it has elongation of 8% or more; in
thicker sections, it has elongation of 10% [12]. The typical value of thermal conductivity for 6061-T6 at 80°C is
around 152 W/m K. A material data sheet defines the fatigue limit under cyclic load as 14,000 psi (100 MPa) for
500,000,000 completely reversed cycles using a standard RR Moore test machine and specimen [13].
2.3 Flow simulation
Flow simulation was carried out using Deform-3D software with the following additional information
gathered for the purpose of simulating the whole process using the above mentioned software.
The additional information and parameters that were necessary for simulation were:
1. STP (STEP) and STL format of the model of the component. (I.e. Aluminium connector)
2. STP (STEP) and STL format of the models of the tool and die set as shown in Fig 3 and Fig 4.
3. Type of the press to be used (in the present investigation, we have considered Hydraulic press).
4. Configuration and characteristics of the press used.
5. Constant movement speed of the press.
6. Temperature of the forging operation (in the present investigation, we emphasize on precision forging which
is usually done below recrystallization temperature, approximately room temperature i.e. cold forging
conditions).
Fig 3 Tool and die set used in the present investigation

Fig 4 Different views of the tool and die set used in the present investigation
2.4 Procedure
Models of the die set and cylindrical billet were created using SOLID EDGE software package.
Contact elements were constructed on all exterior surfaces of the billet, except for the bottom surface and all
inner surfaces of the top die. These contact elements were constructed between the die and billet surfaces to
prevent the penetration. These elements were modeled by using solid edge software and were converted into
STL and STP (STEP) files. Contact elements were on the inside surfaces of the die and utilized the bottom
nodes of the die. The die set was modeled with rigid material properties and the billet was modeled with an
elasto-plastic material (Aluminium 6061) properties. The front and rear surfaces of die were not explicitly
modeled, but were simulated by boundary conditions. Nodes on the front of billet were constrained from
moving past the plane of the front portion of upper die, thus representing the front closure. The constraints were
incorporated which acts similarly to a contact surface.
The coefficient of friction between the wall-billet interface and the other contact surfaces was kept
constant. The planes of symmetry were simulated by using nodal restraints which did not allow the nodes to
move across. The volume of the cavity of die had the same volume as that of the billet, the aim being that when
the die was completely closed, the billet material would completely fill the die cavity. The top die was pushed
downwards over the billet with a constant imposed velocity by hydraulic ram actuated press, while the bottom
die was kept stationary. The magnitude of velocity was chosen in such a way that the computer run time of the
analysis for this model got drastically reduced. The billet was positioned relative to the die cavity as shown in
Fig 5 in such a manner that it allows flow of the billet material within the die cavity in all three directions. This
produced a three dimensional flow pattern. The material flow simulation of the billet material carried out in
Deform 3D software was studied as it filled the die and the results were obtained. The material model for the
billet was that of an isotropic elasto-plastic material (Aluminium 6061) with a bilinear stress-strain curve. This
model incorporates isotropic hardening where the cylindrical yield surface expands as the material yields.

The young’s modulus, yield stress, and the hardening modulus were specified. The stress calculated by the
deform software made use of the following equation (1).
σ = σy + EP× εP (1)
Where
σ represents the effective stress,
σy represents the yield stress of the material,
εP represents the plastic strain,
EP, the plastic modulus is defined as:
EP =E*Eh/ (E-Eh)
Where Eh is the hardening modulus.
The value of the friction coefficient between the die and billet surface was maintained as a constant, and
considered explicitly at locations where a contact surface of the die touched the contact surface of the billet.
Fig 5 Initial setup of the billet in the die cavity between die halves
III. RESULTS AND DISCUSSION
Flow simulation of the precision forging process carried out has henceforth provided critical results
which gives a detailed description of the effective stress, effective strain, principal stress, principal strain,
velocity and damage analysis of the component as well as die set used in the process. The effect of stress
accumulation, strain distribution, material flow velocity, damage can be clearly visualized and henceforth it can
be critically analyzed from the Fig 6, Fig 7, Fig 8, Fig 9, Fig 10 and Fig 11 respectively.The careful observation
of the results suggest that the effective stress, effective strain, principal stress, principal strain, velocity and
damage are maximum at locations where flange opens out and rib growth begins across the geometrical
interlocking between the two halves of die-set and the component surface.
Fig 6 Effective Stress and strain distribution
Fig 6 shows the effective stress and strain distribution along various cross sections of the component, the
effective stress varies from a minimum of 0.536 MPa to a maximum of 396 MPa and the effective strain varies
from a minimum of 0.0278 to 5.57 mm/mm.

Fig 7 Velocity and Damage analysis
Fig 7 gives a brief outline of the velocity and damage analysis for the component, the velocity of flow of
material during plastic deformation of the component varies from a minimum of 0.0874 mm/sec to a maximum
of 48.8 mm/sec and the damage caused in the component varies from a minimum of 0.0000686 to a maximum
of 3.32.
Fig 8 Effective and principal stress variations across the Die-1 cross section
Fig 8 shows the effective and principal stress distribution along various cross sections of Die-1 with a minimum
Effective stress value of 0.186 MPa, maximum effective stress value of 831 MPa, and the principal stress value
ranging from a minimum of -138 MPa to a maximum of 208 MPa.

Fig 9 Effective-Stress Analysis of Die assembly in MPa
Fig 9 shows the effective stress distribution along various cross sections of Die assembly with a minimum value
of 0.186 MPa and a maximum value of 831 MPa.
Fig 10 Displacement analysis of die-component setup in mm
Fig 10 shows the displacement analysis for the die-component setup, the displacement for the die-component
setup varies from a minimum of 0 mm to a maximum of 0.0127 mm.
Fig 11 Velocity analysis of die-component setup in mm/sec
Fig 11 shows the velocity analysis for the die-component set-up, the velocity of flow of material during plastic
deformation of the component in the die setup varies from a minimum of 0.000 mm/sec to a maximum of
0.0127 mm/sec.

IV. CONCLUSION
[1] The effective stress on the component decreases as the initial temperature of the billet increases.
[2] The maximum effective stress occurs during the initial contact of the lower and the upper die with the
work piece.
[3] The maximum effective stress is found to be lesser on the component if open upsetting is carried out on
billet before final forging stage.
[4] The stress concentration is maximum at the contact surface of parting lines of two halves of die set and
the flange portion of the component.
[5] It is observed that presence of small ribs on the outer cylindrical surface restricts the free flow of metal
in the small recess of die cavity during forging, which leads to surface cracks, improper and incomplete
rib formation.
[6] The critical evaluation of the results of the investigation carried out suggests that the problems faced in
precision forging of the component can be overcome by:
 Increasing the height of the billet, upsetting the billet and then carrying out the press forging.
 Providing suitable fillets in the die-set.
 Ensuring suitable gap between the two die halves when the tool and die setup is pressed.
 Increasing the dimensions of ribs or eliminating the need for ribs in the component.
[7] It has also been found that the Aluminium 6061 connector can be press forged (by precision forging)
with maximum benefits if the critical conclusions drawn from the analysis are successfully
incorporated in the process.
V. REFERENCES
[1] Santhosh N, “Flow simulation and characterization of Aluminium forgings conforming to AA 6061
Specification”, M.E. Thesis, Bangalore University, Bangalore, India 2012.
[2] Oh, S.I., 1982. ”Finite element analysis of metal forming process with arbitrary shaped dies”,
Int.J.Mesh.Sci., Vol.24.
[3] Degarmo, E. Paul; Black, J. T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing
(9th ed.), Wiley, ISBN 0-471-65653-4, pp. 398-399.
[4] O. Jensrud, K. Pedersen, “Cold Forging of High Strength Aluminum Alloys and the Development of
New Thermomechanical Processing”, Journal of Materials Processing Technology, 80–81 (1998). pp.
156–160
[5] Victor Vazguez, Taylan Altan., “New Concepts in Die Design-Physical and Computer Modelling
Applications”, Journal of Materials Processing Technology, 98 (2000). pp. 212-223.
[6] J. S. Gunasekera, “CAD/CAM of Dies”, Ellis Horward Series in Mechanical Engineering, Ohio
University, Athens, USA 1989, Ellis Howard Limited.
[7] Douglas, R., Kuhlmann, D., "Guidelines for precision hot forging with applications". Journal of
Materials Processing Technology, 98 (2000). pp. 182-188.
[8] Y.H. Kim, T.K. Ryou, H.J. Choi, B.B. Hwang, “An Analysis of the Forging Processes for 6061
Aluminum-Alloy Wheels”, Journal of Materials Processing Technology, 123 (2002). pp. 270–276.
[9] Li, G., W. Wu, P. Chigurupati, J. Fluhrer, and S. Andreoli, “Recent Advancement of Extrusion
Simulation in DEFORM-3D,” Latest Advances in Extrusion Technology and Simulation in Europe,
Bologna, Italy, 2007.
[10] Altan, T., Oh, S.I, 1983. "Metal fundamentals and forming application", ASM International.
[11] Materials World, Vol. 12, No. 3, pp. 37-38, March 2004.
[12] ASM Handbook of Heat Treatment, Vol. 4, ISBN: 978-0-87170-379-8, ASM International, 1991.
[13] George E. Totten, D. Scott MacKenzie, “Handbook of Aluminum: Physical Metallurgy and Process”,
Vol. 1, 2003.

International Journal of Computational Engineering Research(IJCER)

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