Transcript Forging Lab Presentation

ISE 311
Forging Lab
in conjunction with
Sections 3.1.2 (ch. 3), 19.3 & 19.4 (ch. 19) from the
text book
“Fundamentals of Modern Manufacturing”
Third Edition
Mikell P. Groover
3/25/2008
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Outline
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Introduction
Forging – Basic Principles
Forging – Terminology
Objectives of the forging lab
Forging – materials and equipment
Forging examples – simulations
Summary
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Introduction
Upsetting or Upset Forging is the simplest case of opendie forging involving compression of a workpiece
between two flat dies. Upset forging reduces the height of
the workpiece but increases its cross-sectional area. We
will consider upsetting of a round billet.
Under ideal conditions where there is no friction between
the work piece and the dies, the billet deforms
homogeneously (the cylindrical shape of the billet
remains cylindrical throughout the process). But in
practical conditions the billet tends to barrel since there is
some friction.
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Introduction
The ring compression test is used to evaluate lubrication
in forging by measuring forces and dimensional changes
in the specimen.
In this test, a flat ring is deformed (upset) between two
flat platens. As the height of the ring is reduced, its
outside diameter increases.
If there were no friction between the dies and workpiece
both the inner and outer diameters of the ring would
expand. However, for large friction at material/ die
interface, the internal diameter of the ring is reduced with
increasing deformation.
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Introduction
Homogeneous upsetting of a cylindrical billet (without friction)
Figure 19.10, Groover
V1 = upper die velocity
Do, D, D1 = average billet
diameters before, during and
at the end of deformation
Practical upsetting of a cylindrical billet (with friction & barreling)
Figure 19.11, Groover
ho, h, h1 = billet heights
before, during and at the
end of deformation
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Introduction
Upsetting of a ring with good lubrication (μ is low) and bad
lubrication (μ is high)
Figure 32.2, Kalpakjian
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Terminology
In homogeneous upsetting / no friction:
ho
True Strain ,   ln
h
(1)
ho = starting height of workpiece (before deformation)
h = instantaneous height of the work piece (at an intermediate
press stroke)
F
True Stress  
A
(2)
F = instantaneous upsetting force
A = instantaneous cross sectional area of the workpiece
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Terminology
In homogeneous upsetting:
UpsettingForceF  Yf A
(3)
Y f  flowstress  K
(4)
n
K = strength coefficient, n = strain hardening coefficient
F increases with deformation (press stroke) since Yf and A
both increase with deformation and strain (Eqs. (1), (3) & (4))
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Terminology
Practical Upsetting of a cylindrical workpiece (with friction &
barreling):
F  K f Yf A
(5)
0.4D
Forging Shape Factor K f  1
h
(6)
Where  = coefficient of friction (0.05 – 0.3)
D = instantaneous workpiece diameter, mm (in),
h = instantaneous workpiece height, mm (in)
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The Ring Compression Test
The chart seen to the right gives the
calibration curves for a specific ring
geometry (OD:ID:Height = 6:3:2)
and for different coefficients of
friction, μ.
In this chart, the variation of the %
change in internal diameter is given
for % reduction in height of the
compressed ring.
After the ring compression test is
completed, the ID and height of the
upset ring are measured and the %
reduction of each is found. From the
location of this experimental point on
the chart, μ can be estimated.
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Cold, warm and hot forging
The forging operation (and metal forming operations in
general) can be performed at various temperatures
ranges:
Cold forging
T < 0.3 Tm
Warm forging
0.3 Tm < T < 0.5 Tm
Hot forging
T > 0.5 Tm and usually less than 0.75 Tm
Where Tm is the melting temperature of the metal
Note: for most metals, recrystallization occurs between 30% and 50% of
The melting temperature
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Cold, warm and hot forging
Cold forging vs. Hot forging:
Cold
Hot
Strength/ hardness of the forged billet
Higher
Lower
Ductility/ ability to produce intricate shapes
Lower
Higher
Force/ energy/ machine capacity required
Higher
Lower
Load on the tools (dies)
Higher
Lower
Tool wear
Less
More
Dimensional accuracy
Better
Worse
Surface finish
Better
Worse
The need for heating equipment
No
Yes
Barreling (uniformity of deformation)
Less
More
You have to think about the reasons behind each of the
above mentioned points
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Objectives
This lab has the following objectives:
• Understand fundamentals of the forging process
• Observe the effects of frictional forces in forging
process
• Compare material properties of forged parts with
respect to working temperature
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Objectives
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Students will be able to:
Perform an upsetting test on specimens of two
different materials (steel and aluminum)
Use proper equipment terminology, and know the
parameters to control during the test
Measure and collect the force and height data and
observe the barreling effects
Compare the forces measured in the laboratory tests
with the calculated forces with and without friction
effect
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Upsetting And Hot Forging
• Test Materials and Equipment
– OBI (Open Back Inclinable) mechanical press with the LoadGard system
to measure the upsetting force
– Upset tooling, tongs, acetylene torch
– Specimens: (1) Aluminum, (2) Steel
– Dial Calipers
• Safety Equipment and Instructions
– Safety glasses with side shields are required during the entire lab period
– Pay attention and follow the lab instructor’s directions
– Do not use your hand to put or remove specimens on the die. Instead, use
the supplied tongs
– Turn off the OBI press when ever you need to adjust the press slide
setting (shut height etc.)
– Do not touch the forged specimens with your bare hands until they cool
down to room temperature
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Mechanical Presses Used in Forging
Eccentric Shaft
Flywheel
The drive system used in most
mechanical presses is based on a
slider-crank
mechanism
that
translates
rotary
motion
into
reciprocating motion.
Connecting Rod
Frame
Ram or Slide
Shut height
adjustment modifies
the length of the
connecting rod and
changes the bottom
position of the slide
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Slider-crank Mechanism
TDC
BDC = Bottom Dead Center
Bottom position of the slide
TDC = Top Dead Center
Top position of the slide
• The length of connecting rod
determines the TDC and BDC or
shut height. Its length can be
modified.
• The total slide stroke S = 2r is
unchanged
BDC
Connecting Rod
Shut Height
Adjustment
Force
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OBI press used for forging tests
Flywheel
Load reading system
Connecting rod
Shut height adjustment
Power box to start
and stop the press
Press slide
Yellow pedal to
cycle the press
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Forging
Shims and shut height adjustment:
One of the 5 Shims
Screw for shut height adjustment
Handle to adjust the
stroke
Slot to place handle and rotate slide screw
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The Loadgard and the power box of the press
Load Reading
Reset Button
Start Button
Stop Button
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Hardness testing machine
Hardness Reading
Indenter
Plate on which to place the specimen
Handle to load the specimen
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Forging
Test Specimen before deformation:
• The upsetting can be
conducted with either a
round bar or ring specimen.
• The round bar specimen is
used for the current test.
• The specimen is placed on
the
lower
die
and
deformation is applied using
the motion of the top die.
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Forging
Dial Calipers to measure the dimensions of the test specimen:
Specimen
Dial Calipers
• The height of the specimen during testing is measured using dial
calipers.
• As the specimen is compressed using 5 different slide positions, the
dial calipers are used to measure the dimensions of the specimen
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after each stroke.
Simple Upsetting – Test Procedure
1.
2.
3.
4.
5.
6.
Obtain one steel billet and one aluminum billet from the lab
instructor
Measure and record the initial dimensions of the billets (OD &
height); OD is the outer diameter
Measure the hardness for the steel billet in three different
locations.
Set the OBI press for the first step/shut height in the upsetting
process (shim 1)
Using tongs, insert one of the billets into the tooling. Try to
place it as close to the center of the upsetting platen as
possible
Step on the yellow pedal to cycle the press one time
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Simple Upsetting – Test Procedure
7.
8.
9.
10.
11.
12.
13.
Record the press load from the Loadgard system. (note: after
recording the load, make sure to reset the Loadgard system in
order to prevent false reading for the next measurement)
Use the tongs to remove the deformed billet
Measure and record its new height
Repeat steps 4-9 for each of the other billets
Adjust the press for the next deformation (shims 2 through 5)
Repeat steps 4-9 for a total of 5 deformation steps. (caution: the
flywheel on the punch press must stop, which means the OBI
press must be turned off, before changing shut height)
Measure the hardness for the steel billet in three different
locations
Mark the steel billet such that it can be identified as the cold
forging sample and keep it for comparison with the hot forging
sample
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Ring Compression – Test Procedure
1. Obtain one steel ring and one aluminum ring from
the lab instructor
2. Measure and record the initial dimensions of the
billets (OD: Outer Diameter, ID: Internal Diameter,
& height)
3. Set the OBI press for the first step/shut height in the
upsetting process (shim 1)
4. Place the specimen on the height block and place the
block with the specimen on it as close as possible to
the center of the upsetting platen
5. Step on the yellow pedal to cycle the press one time
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Ring Compression – Test Procedure
6. Set the OBI press for the second step/shut height in
the ring compression test (shim 2)
7. Repeat steps 4 & 5 for the yellow shim
8. Measure and record all dimensions of the specimen
(OD, ID, and height)
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Hot Forging – Test Procedure
1. Obtain one steel billet from the lab instructor
2. You will assume that the initial and final dimensions
are the same as for sample 2 in part 1 (cold forging).
3. Measure the hardness for the steel billet in three
different locations.
4. Set the OBI press for the final step/shut height in the
upsetting process (shim 5)
5. Using the acetylene torch, heat the specimen until it
is glowing red
6. Using tongs, insert the hot billet into the tooling
placing it as close as possible to the center of the
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upsetting platen
Hot Forging – Test Procedure
7. Step on the yellow pedal to cycle the press one time
8. Measure the load and the hardness (at 3 locations)
Note1: the specimen should be allowed to cool slowly (should not be quenched)
as this may affect the hardness.
Note2: The function of the flywheel in a mechanical press is to store kinetic
energy. This energy is used to form the workpiece. If the height reduction
reached in a single stage is very large, the energy required, which is taken from
the flywheel, may be large enough to slow down the flywheel very rapidly. To
avoid this, deformation is done in stages and enough time between these stages
is provided for the motor to build up the flywheel rotational speed to its idle
speed.
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Summary – Forging Lab
Specimen before and after the compression:
Original Specimen
Barreled Specimen
after compression
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Summary – Forging Lab
Specimen before and after the compression:
ho
h1
Do
D1 (avg)
V  billet volum e
Do2 h
4
D1 (average) can be calculated from volume constancy, i.e.,
V .4
D1 
h
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Summary – Forging Lab
Comparison of cold and hot forging:
Original steel specimen
Steel specimen
after cold forging
(5 steps/hits)
Steel specimen
after hot forging
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Summary – Forging Lab
Comparison of original
deformed rings:
Original steel
specimen
Steel specimen
after cold forging
(2 steps/hits)
ring
specimens
Original aluminum
specimen
to
Aluminum specimen
after cold forging
(2 steps/hits)
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Finite Element (FE) Simulations
The next several slides illustrate the simulation of the cylinder, ring, and
hot cylinder compression tests, generated by FEA.
The following slides include:
- Cold upsetting of Al 1100 cylinders (σ = 25.2 ε0.304 Ksi)
- Comparison of Al 1100 and Steel AISI 1010 (σ = 103.8 ε0.22
Ksi) upsetting with respect to forging load
- Illustration of the effect of μ on the internal diameter in ring
compression test of Steel AISI 1010
- Comparison between the upsetting of Steel AISI 1015 at room
temperature (68 oF: σ=117.5 ε0.15 Ksi) and at elevated temperature
(1112 oF: σ=54.7 ε0.072 Ksi)
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Simple upsetting simulation
Cold upsetting of Aluminum 1100
σ = 25.2 ε0.304 Ksi
μ = 0.12
Stage A
Stage B
Stage C
Note the barreling
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Simple upsetting simulation
Load-Stroke curves for Al 1100 (previous simulation) and Steel
AISI 1010
σAl = 25.2 ε0.304 Ksi
σsteel = 103.8 ε0.22 Ksi
μ = 0.12
Load (KLb) vs. Stroke (in)
45
40
Load (KLb)
35
30
25
20
Al 1100
15
Steel 1010
10
5
0
0
0.1
0.2
0.3
0.4
0.5
0.6
Stroke (in)
Note how material properties affect the upsetting force
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Ring compression simulation
Ring compression of Steel AISI 1010 (σ = 103.8 ε 0.22 Ksi) with two
different Friction coefficients: note how increasing μ reduces the final internal
diameter. This idea will be used in the lab to determine μ
Before
After (μ = 0.12)
After (μ = 0.3)
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Note the change in internal diameter
Hot vs. Cold upsetting
A comparison between cold and hot upsetting of steel: note the following:
1- The load in cold forging > hot forging
2- Barreling in cold forging < hot forging
Load (KLbs) vs. Stroke (in) at various temperature
45
40
Cold
35
Load (KLbs)
30
25
T = 68 F
20
T = 1112 F
15
10
Hot
5
0
0
0.1
0.2
0.3
Stroke (in)
0.4
0.5
0.6
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Summary – Upsetting Lab
This lab preparation material introduced:
• The basic principles of the forging (upsetting, ring
compression, and hot upsetting) and the terminology
used (stress, strain, barreling, forging shape factor)
• The objectives of and the expected outcomes from the
evaluation of test results.
• The testing equipment and the test procedure
• FE simulations
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