1. ISE 311 Forging Lab in conjunction with Sections 3. 1. 2 (ch. 3), 19
ISE 311 Forging Lab in conjunction with Sections (ch. 3), 19.3 & 19.4 (ch. 19) from the text book “Fundamentals of Modern Manufacturing” Third Edition Mikell P. Groover 3/25/2008 1

2. Outline Introduction Forging – Basic Principles Forging – Terminology
Objectives of the forging lab
Forging – materials and equipment
Forging examples – simulations
Summary

3. Introduction
Upsetting or Upset Forging is the simplest case of open-die 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.

4. 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.

5. Introduction
Homogeneous upsetting of a cylindrical billet (without friction)
Practical upsetting of a cylindrical billet (with friction & barreling)
Figure 19.10, Groover
V1 = upper die velocity
Do, D, D1 = average billet diameters before, during and at the end of deformation
Figure 19.11, Groover
ho, h, h1 = billet heights before, during and at the end of deformation

6. Introduction
Upsetting of a ring with good lubrication (μ is low) and bad lubrication (μ is high)
Figure 32.2, Kalpakjian

7. Terminology In homogeneous upsetting / no friction:
ho = starting height of workpiece (before deformation)
h = instantaneous height of the work piece (at an intermediate press stroke)
F = instantaneous upsetting force
A = instantaneous cross sectional area of the workpiece
(1)
(2)

8. Terminology In homogeneous upsetting: (3)
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))
(3)
(4)

9. Terminology
Practical Upsetting of a cylindrical workpiece (with friction & barreling):
Where  = coefficient of friction (0.05 – 0.3)
D = instantaneous workpiece diameter, mm (in),
h = instantaneous workpiece height, mm (in)
(5)
(6)

10. 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.

11. Cold, warm and hot forging
The forging operation (and metal forming operations in
general) can be performed at various temperatures
ranges:
Where Tm is the melting temperature of the metal
Note: for most metals, recrystallization occurs between 30% and 50% of
The melting temperature
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 Tm

12. Cold, warm and hot forging
Cold forging vs. Hot forging:
You have to think about the reasons behind each of the
above mentioned points
Cold
Hot
Strength/ hardness of the forged billet
Higher
Lower
Ductility/ ability to produce intricate shapes
Force/ energy/ machine capacity required
Load on the tools (dies)
Tool wear
Less
More
Dimensional accuracy
Better
Worse
Surface finish
The need for heating equipment No
Yes
Barreling (uniformity of deformation)

13. 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

14. Objectives 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

15. 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

16. Mechanical Presses Used in Forging
Shut height adjustment modifies the length of the connecting rod and changes the bottom position of the slide
Ram or Slide
Frame
Connecting Rod
Flywheel
Eccentric Shaft
The drive system used in most mechanical presses is based on a slider-crank mechanism that translates rotary motion into reciprocating motion.

17. Slider-crank Mechanism
TDC
BDC
Connecting Rod
Shut Height Adjustment
Force
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

18. OBI press used for forging tests
Flywheel
Load reading system
Shut height adjustment
Power box to start and stop the press
Yellow pedal to cycle the press
Connecting rod
Press slide

19. Forging Shims and shut height adjustment: One of the 5 Shims
Screw for shut height adjustment
Handle to adjust the stroke
One of the 5 Shims
Slot to place handle and rotate slide screw

20. The Loadgard and the power box of the press
Load Reading
Reset Button
Start Button
Stop Button

21. Hardness testing machine
Hardness Reading
Indenter
Handle to load the specimen
Plate on which to place the specimen

22. 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.

23. Forging Dial Calipers to measure the dimensions of the test specimen:
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 after each stroke.

24. Simple Upsetting – Test Procedure
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

25. Simple Upsetting – Test Procedure
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

26. Ring Compression – Test Procedure
Obtain one steel ring and one aluminum ring from the lab instructor
Measure and record the initial dimensions of the billets (OD: Outer Diameter, ID: Internal Diameter, & height)
Set the OBI press for the first step/shut height in the upsetting process (shim 1)
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
Step on the yellow pedal to cycle the press one time

27. Ring Compression – Test Procedure
Set the OBI press for the second step/shut height in the ring compression test (shim 2)
Repeat steps 4 & 5 for the yellow shim
Measure and record all dimensions of the specimen (OD, ID, and height)

28. Hot Forging – Test Procedure
Obtain one steel billet from the lab instructor
You will assume that the initial and final dimensions are the same as for sample 2 in part 1 (cold forging).
Measure the hardness for the steel billet in three different locations.
Set the OBI press for the final step/shut height in the upsetting process (shim 5)
Using the acetylene torch, heat the specimen until it is glowing red
Using tongs, insert the hot billet into the tooling placing it as close as possible to the center of the upsetting platen

29. Hot Forging – Test Procedure
Step on the yellow pedal to cycle the press one time
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.

30. Summary – Forging Lab Specimen before and after the compression:
Original Specimen
Barreled Specimen after compression

31. Summary – Forging Lab Specimen before and after the compression:Do
D1 (avg) h1 ho
D1 (average) can be calculated from volume constancy, i.e.,

32. Original steel specimen
Summary – Forging Lab
Comparison of cold and hot forging:
Steel specimen
after cold forging
(5 steps/hits)
Original steel specimen
Steel specimen
after hot forging

33. Summary – Forging Lab
Comparison of original ring specimens to deformed rings:
Aluminum specimen
after cold forging
(2 steps/hits)
Original aluminum
specimen
Original steel
specimen
Steel specimen
after cold forging
(2 steps/hits)

34. 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 = 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)

35. 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

36. Simple upsetting simulation
Load-Stroke curves for Al 1100 (previous simulation) and Steel
AISI 1010
σAl = 25.2 ε0.304 Ksi
σsteel = ε0.22 Ksi
μ = 0.12
Note how material properties affect the upsetting force

37. Ring compression simulation
Ring compression of Steel AISI 1010 (σ = 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)
Note the change in internal diameter

38. 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
Cold
Hot

39. 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