Operational Manual - DCU

@ TQ Education and Training Ltd 2000
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Training Limited.
All due care has been taken to ensure that the contents of this
manual are accurate and up to date. However, if any errors are
discovered please inform TQ so the problem may be rectified.
A Packing Contents List is supplied with the equipment.
Carefully check the contents of the package(s) against the list. If
any items are missing or damaged, contact your local TQ agent
orTQ immediately.
PE/ajp/O200
TQ Education and Training Ltt:l
Products Divislolrl

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Section
Contents
1 INTRODUCTION 1
2 ASSEMBLY
~I
How to Set up the Equipment
3 TORSION TESTING
5
General Notes on Experimental Work
~'
~t
Detailed Procedure
3
5
4
USE OF THE TORQUE METER AND PROCEDURE FOR
CALIBRATION
Procedure for Checking the Calibration
Procedure for Full Calibration
7
7
7
5 EXPERIMENTATION
Notes on Laboratory Sheets
Object
Apparatus
Theory
Experimental Procedure
Results
Suggested Increments of Strain
Notes on the Content of the Laboratory Report
Items to be Included
Discussion of Results
9
9
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9
9
10
10
TYPICAL EXPERIMENTAL RESULTS
The Bauschinger Effect
Upper and Lower Yield Strength of Mild Steel
Relationship between Torque and Surface Stress
Cast Iron
6 11
11
11
11
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APPENDIX A
APPENDIX B
TORSION TEST SPECIMEN
THE TORSIOMETER
Introduction
Construction
Use and Operation of the Torsiometer
Use
Operation
A-1
A-2
A-2
A-2
A-2
A-2
A-2

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The 8Ml Torsion Testing Machine enables forward and
reverse tests on standard 6 mm TQ torsion specimens,
and other hexagon ended specimens requiring torques of
up to 30 Nm. With additional chucks (optional extra) it
can also be used for testing wire up to a length of 0.7 m.
The apparatus is illustrated in Figure 2.
The loads are applied manually through a 60: 1
reduction gearbox. The torque is reacted by a torsion bar
(as shown in Figure 3), whose movement, relative to the
displacement arm, is measured by a linear potentiometer
connected to a TQ Digital Torque Meter. This mett:r is
supplied as standard with the apparatus and is calibnued
to give a readout of torque in Nm or lb.in (see Section 4
on page 7).
11

TQ Torsion Testing Machine
Torque
shaft
DeftectkJn
81m
Lk18ar
potentiometer
Figure 3 End view of torque measurement system
gearbox output shaft and can be used for measurement
in the plastic range. A resettable counter is also fitted to
the gearbox input shaft to give an overall record of input
revolutions (note that one revolution represents 6°).
Two pairs of hexagonal sockets are provided for
holding standard TQ specimens. These sockets fit on the
ends of the input and torque shafts as shown in Figure 2.
The two pairs of hexagonal sockets provided are:
. 3/16" Whitworth - for all specimens (the smaller
sized sockets)
. 12 mm AF - these can be used for cast iron
specimens in order to accommodate any roughness
on the cast ends
In some cases it may be necessary to remove excessive
bumps or flashing from specimens using a file.
Accurate measurement of twist angles, and hence
strain, can be obtained using the TQ Torsiometer which
is an optional extra.
The input rotation (the angle of twist of specimen) can
be measured by three methods as in Figure 2. For
accurate readings in the elastic range a protractor scale
reading 0.10 is fitted to the input shaft of the gearbox. A
second protractor scale reading 10 is fitted to the

SECTION 2 ASSEMBLY
The apparatus is despatched fully assembled except for
the following:
(a) Adjustable feet (2 oft)
(b) Levelling handwheel and tie rod assembly
(c) Counter assembly
sufficient room to insert a specimen between the
sockets.
To assemble, first lift each end of the apparatus in turn
and screw an adjustable foot upwards into the
appropriate hole in each of the end castings (see Figure I).
Note that the plastic knob should point downwards and
that there is only one adjustable foot at each end of the
apparatus.
Next fit the levelling handwheel between the torque
arm and the lower bracket at the right of the apparatus.
Secure the tie rod ends in position by inserting the
screwed pins. Lock these in place by fitting the two split
pins provided.
Note: For safety reasons, the screwed pins must be
screwed fully in and the split pins must be fitted to
ensure that the joints do not work loose during
operation.
7:
Fit the counter assembly as follows:
1. Remove and retain the two cap head screws located
on the top of the gearbox.
2. Place the counter on the top of the gearbox with the
cam follower lever resting on the carn of the
handwheel.
3. Secure the counter to the gearbox with the two
screws removed in step (1).
How to Set up the Equipment
I. Level the rig on a suitable bench by adjusting the
two adjustable feet.
2. Connect the electrical lead from the output socket
on the right of the apparatus to the input socket at
the rear of the Digital Meter. Connect the meter to a
mains supply and switch on.
3. Select the required drive sockets and fit them to the
input and torque shafts.
4. Loosen the two locking knobs on the gearbox
carriage and move the carriage along the bed such
that, with the shaft fully to the left, there is just
s.
6.
Set the deflection ann approximately level by
adjusting the handwheel, then set the dial gau~;e to
read zero by rotating the outer bezel. Tap the
apparatus lightly and recheck the dial gauge.
Select the desired range on the Digital Nleter
(metric units or imperial). Set the reading to zero by
adjusting the ZERO adjusting knob at the rear of
the meter. Note that the meter is calibrated ~:fore
leaving the factory, but if required the calibration
can be checked using the procedure given in
Section 4.
If required, fit the Torsiometer to the specunen.
Insert the specimen into one of the sockets, then
rotate the handwheel until the second socket will
slide freely onto the other end of the specimen.
8. Take up any free movement by slowly rotatin!~ the
handwheel clockwise until the Digital Meter
reading just changes (i.e. a reading of 0.1 Nm or
1.0 lb. in). Turning the handwheel clockwise ~~ives
forward loading of the specimen, and anticlockwise
gives reverse loading.
9. Loosen the grubscrew on the scale, and positi,:>n it
in line with the cursor. Set the reading to zero and
lock the scale in position. Zero the counter by
turning the knob at the far end of the counter.
10. All zeros are now set and testing can commenc

SECTION 3 TORSION TESTING
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General Notes on Experimental Work
The tests possible with Torsion Testing Machine
include the determination of the upper and lower yield
strengths for nonnalised steel specimens, demonstration
of the Bauschinger effect, and other effects relating to
work hardening and heat-treatment. The detailed
procedure outlined below should be followed in each
case in order to maintain consistent readings of
specimen twist using the scales provided. If a
torsiometer is used, or if high accuracy is not required,
there is no need to relevel the displacement arm before
each reading (i.e. there is no need to maintain a zero
reading on the dial gauge). This part of the procedure is
only necessary in order to maintain the position of one
end of the specimen stationary whilst registering the
true angle of twist on the protractor scales. Omitting this
step will not affect the accuracy of the torque readings.
It should be noted here that the protractor scales only
give an approximate measure of the twist of the
specimen since readings include the twist of the drive
shafts and specimen ends, and also any slight movement
of the specimen ends in the drive sockets. These effects
will be most significant in the elastic range where the
load increases rapidly for only a small twist of the
specimen. If the modulus of rigidity is to be determined,
it is recommended that a torsiometer should be used.
Reverse loads are applied by turning the handwheel
anti-clockwise. Note that the Digital Meter reading will
then be negative.
IMPORTANT
Always reduce the load to zero if it is required to
remove a specimen before failure (for exam pIle,
for heat treatment). DO NOT ATTEMPT TO
REMOVE A SPECIMEN WHEN UNDER
LOAD.
Detailed
Procedure
1. For forward loading rotate the input handwheel
clockwise until the input shaft has rotated, for
example, through 0.5° as indicated by the dial.
2. Return the reading on the dial gauge to zero by
rotating the levelling handwheel.
3. Record the torque displayed by the Digital Meter,
noting the units and record the total angle of twist
from zero.
4. Repeathe procedure as required until the specimen
has yielded or until all points of interred have l)een
covered. Note that in the plastic range, angles of
twist can be incremented to 6° or multiples of 6°.
For ductile specimens, increments of up to 60° may
be required, as some specimens require up to
revolutions before failure occurs.
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SECTION 4 USE OF THE TORQUE METER AND PROCEDURE FOR
CALIBRATION
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The apparatus is supplied complete with a Digital Meter
for torque measurement and this is calibrated before
leaving the factory. Four trimming controls are fitted to
the rear of the meter as follows:
a. ZERO adjustment knob - this is used for zeroing
the meter (if necessary) prior to applying load.
b. CAL screw - this can be used to adjust the
calibration of the meter in the SI units mode.
c. SI/lMP ADJUST screw - this adjusts the ratio
between the SI and IMPERIAL units as selected by
the SI/IMP switch at the front of the meter.
d. DECIMAL POINTS - this can be used to determine
the number of decimal points displayed.
Controls (b) and (c) should not normally require
adjustment, but if adjustment become necessary this
should be done with care, as the controls are delicate.
Procedure for Checking the Calibration
Deflection
arm "
1"'3
..,.
Calibfation
Dial
gauge
#_.
Levelling
handwheel
Figure 4 Meter calibration using the loading arm
1. For the calibration arm onto the square end of the
torque shaft, then set the deflection arm
approximately level by adjusting the handwheel
(see Figure 4). Set the dial gauge to zero by rotating
outer bezel. Tap the equipment lightly and recheck
the dial gauge.
2. Select SI units and set the Digital Meter to zero by
adjusting the ZERO knob at the rear of the
instrument.
3. Add a load of 5 kg to the calibration arm and return
the reading on the dial gauge to zero by rotating the
handwheel. Check that the reading on the Digital
Meter is 24.5 :to.5 Nm.
4.
5.
Remove the load and check that the meter retools to
zero.
Note: If the error is greater than 0.5 Nm (i.e. 2%)
the calibration should be adjusted using the CAL
screw at the rear of the instrunlent to set the reading
to 24.5 Nm when the load is 5 kg. For refer,ence
purpose, note that the calibration ann is 500 mm
long, hence 5 kg gives 5 x 9.81 x 0.5 = 24.53 Nm.
If it is required to use imperial units (lbf.ft), re'peat
the above procedure with the units switch sc:t to
IMP and set the SI/IMP ADJ screw to give
17.96 Ibf.ft.
Procedure
for Full Calibration
For most purposes it can be assumed that the calibnltion
is linear and setting at one value of load is adeqLlate.
However, if required, the full calibration over the whole
range can be checked as follows:
I. Set an initial zero condition as in steps (I) and (2)
in 'Procedure for Checking the Calibration'.
2. Add weights to the weight hanger in the increments
available (i.e. 500 g, I kg, 2 kg and a further :Z kg,
plus weight hanger at 500 g) and record the meter
reading at each value up to 6 kg. Return dial gauge
to zero at each step, using the handwheel.
3. Reduce the load in the same steps and again record
the meter readings.
4. Plot a graph of meter reading against applied torque
(which equals 0.5 x load x 9.81 Nm). Draw a mean
line through the points and calculate the slOlle of
the line (ideally unity). If there is a significant t:rror,
apply a load of 5 kg, note the reading and divide
this by the average slope, then reset the meter to
this new value.
S. The above procedure can then be repeate,:i, if
desired, to check that the resulting calibration is
correct.
It may be noted that the graph plotted in step (4) will
also show the linearity of the torque measuring system
and any hysteresis which is present due to stiction in the
torque shaft bearings. It will be found that both these
sources of error are mall, but students should be aware
of their existence and should comment on them in their
laboratory reports.

SECTION 5 EXPERIMENTATION
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The fonn of Laboratory Sheets and Reports quite
obviously will depend very much on the individual
lecturer and the type of experiment being carried out;
however for the more elementary work the following
example serve as a guide for the student operator.
Notes on Laboratory Sheets
Using a Torsion Test to Destruction as an example, the
following is a suggested layout for a laboratory sheet.
Object
To carry out a torsion test to destruction in order to
determine for a specimen:
(a) The modulus of rigidity
(b) The shear stress at the limit of proportionality
(c) The general characteristics of the torque, angle of
twist relationship.
Apparatus
Torsion Testing Machine and Torsiometer, steel rule
and micrometer.
Theory
From the general torsion theory for a circular specimen:
T Ge 't
- = =-
J
where:
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T= Applied torque Nm or lbfin
J = Polar second moment of area mm or in
G = Modulus of rigidity N/mm2 of Ibf/in2
e = Angle of twist (over length) radians
I = Gauge length mm or in
t = Shear stress at radius r N/mm2 or 1 bf/in2
r = Radius mm or in
Experimental Procedure
I. Measure the overall length and diameter of the test
section of the specimen.
2. Draw a line down the length of the test section of
the specimen with a pencil; this serves as a visual
aid to the degree of twist being put on the specimen
during loading.
3. Mount the specimen finnly in the Torsion Testing
Machine. For each increment of strain record the
following:
(a) Angle of twist of the specimen in degrees
(b) Applied torque
(c) Angle of twist over the 50 mm gauge length in
radians, as recorded by the dial gauge indicator
(d) When the elastic limit has been passed
continue to test to destruction with ever
increasing increments of strain, recording for
each strain increment:
]. Angle of twist in degrees
2. Applied torque
Note: In some tests it may be found unnecessary to use
the torsiometer after the elastic limit has been reached.
If this is the case, the torsiometer can be removed from
the specimen and readings of twist can be taken din:ctly
from the machine scales. To remove the Torsiom'~ter,
unclamp the two cap screws securing it to the specimen
and slip each end clamp off the specimen. The end
clamps have been slotted for this purpose. It is not
possible to remove the centre cylindrical spacer of the
Torsiometer as this would involve disturbing the end
fixing of the specimen, i.e. releasing it from the chuck.
This should be done under any circumstances during
test.
Results
Initial diameter of specinen
Final diameter of soedmen
Gauge length ~ specinen
Initial overall length of spec"men
Final overall length of specimen
Tabulate the results under pressure headings for the
elastic and non-elastic regions.
Suggested Increments of Strain
To ensure that an adequate number of values are
obtained from the test, particularly during the elastic
region of strain, the following is recommended:
Notes on the Content of the Laboratory
Report
As in the case of the Laboratory Sheet the content of the
report will depend largely on the type of test carrie

TQ Torsion Testing Machine
Items to be Included
Include in the report a dimensioned drawing of the
specimen. Using the tabulated results plot a graph of
applied torque, T, against angle of twist a as a base for
the elastic region. Use the slope of this graph to
determine the value of the modules of rigidity. Also
from this graph determine the torque, and then calculate
the shear stress at the limit of proportionality. Plot a
graph of applied torque against angle of twist of the
specimen as a base, for the complete test to destruction.
Discussion of Results
1. State, and comment upon, the values obtained from
the test.
2. Comment upon the overall result obtained from the
test.
3. Comment upon the apparatus and procedures.
4. Discuss the errors involved in determining the
modulus of rigidity using the angle of twist from
the machine dial, and compare the results obtained
with the value found by using the Torsiometer.

SECTION 6 TYPICAL EXPERIMENTAL RESULTS
The Bauschinger Effect
When a metal bar is subjected to torsional overstrain
and the load then removed, the load-free bar is full of
residual stresses. These stresses are of two kinds:
I. Body stresses which affect a relatively large
volume of metal (i.e. macro stresses), and
2. Textural stresses which are really the residual
stresses in between and within the crystals of the
metal caused by deformation of each crystal (i.e.
they are in the actual texture of the metal).
Fortunately body stresses (which are beneficial) are
more stable than textural stresses (which are harmful),
the latter being removed by a low temperature heat
treatment of 200°C.
greater dIan dIe torque at G. This shift of dIe strength
range in dIe direction of dIe plastic defonnation is
sometimes called the 'Bauschinger Effect'.
Upper and Lower Yield Strength Mild StEtel
Normalised mild steel has the peculiar propert)' of
having an upper and lower yield strength. That is, the
initiation of yield occurs at a greater stress than the
propagation of yield along the bar.
This is demonstrated in Figure 6 where, after the ulitial
yielding of the specimen, point A, the load immediately
fallen to a lower value, point B. The strain reduces until
the specimen is again in the elastic range, point C, but
when reloaded it yields at the lower yield strength, lJOint
D, showing that with mild steel the yield propagates at
the lower yield strength stress value.
Figure 5 Reverse torsion tests Relationship between Torque and Surlace
Stress
Reverse torsion tests are possible on the Torsion Testing
Machine, allowing residual stress phenomena to be
readily demonstrated, as shown in Figure 5. In the initial
load cycle the specimen yields at A, is plastically
defoTDled to B, then unloaded and plastically deformed
in the reverse direction to point C. It is then loaded in
the positive direction to point 0, unloaded and given a
low temperature heat treatment, and then reloaded. It
now yields at F rather than O. Thus the harmful effects
of the textural stresses, which were removed by the heat
treatment, were equal to OF. The vertical distance of
point F represents the beneficial effect of the body
stresses.
If the material is now strained to point E and then
strained in the reverse direction to point K (i.e. sight
negative plastic strain). On reloading it arrives back at
the strain represented by point E at a lower torque value
G. Thus, during the strain cycle the strength range has
moved in the negative direction that is the torque at F is
During both the elastic and plastic range of torsional
strain, the relationship between applied torque, 7: and
the maximum shear stress, which occurs at the surface
'tmax, is proportional to 1/ d', the actual relationship
depending upon the stress strain characteristics of the
material being tested. In the elastic range the precise
relationship is:
16T
't= -r
Jtd
Normally this relationship for stress is used throu~~out
the test, but in the plastic region. t is a nominal !;tress
and not the real stress. The real stress is less thw:l the
nominal stress.

APPENDIX A
TORSION TEST SPECIMEN
~ A standard range of metric specimens can be supplied For specimens of gauge 6", see catalogue order no.
by TQ. Each specimen is stamped with a code reference TRIO6O to TRIO85.
and has dimensions as shown in Figure 9.
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Figure A 1 Standard torsion specimen
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APPENDIX B THE TORSIOMETER
Introduction
The TQ Torsiometer has been speciany designed to fit
onto the standard test specimens listed above. The
Torsiometer can accommodate the fun range of strain
by continual adjustment of its dial indicator and can
thus be used to accurately measure strains in both the
elastic and plastic regions.
Construction
A sectional arrangement of the Torsiometer is shown in
Figure 10. It consists of two end clamps, which are
located axially by the centre cylindrical spacer. Each
end clamp contains a 90° cone point socket headed cap
screw, used to clamp the Torsiometer onto the
specimen. A gauge length of 50 millimetres is
maintained between the two clamping screws by the
intermediate spacer.
The end clamps are slotted to facilitate easy
insertion and removal of the specimen. Each end cap
contains two hardened steel rollers to locate the
Torsiometer centrally onto the specimen when clamped
in position. The two component parts of the end clamp
are held rigidly together by the knurled nut. The lefthand
end clamp carries a dial gauge reading to an
accuracy of 0.00 I of an inch. The plunger of the dial
gauge is positioned exactly one inch from the centre of
the specimen and bears on the flat portion of a rod,
which is integral with right-hand clamp. This
positioning of the dial gauge relative to the other over
its gauge length will be represented on the dial gauge in
0.00 I of an inch.
Note that an angular displacement on the dial gauge
represented by 0.001 of an inch is equivalent to an
angular displacement of 0.001 radian. This is because
the dial gauge plunger is exactly 1 inch from the
specimen centreline, acting on a circumference of 27t
radians in a circle the angular displacement shown on
the dial gauge in inches is therefore equivalent to
angular displacement in radians.
Use and Operation
of the Torsiometer
Use
The Torsiometer should be used where more accurate
measurement of strain over a precise gauge length is
desired. Strain can be measured accurately in both the
elastic and plastic regions, thus allowing the Modulus of
Rigidity to the determined in the elastic region and also
providing very accurate means of measuring the work
hardening properties of the specimen. To continue
reading on the dial indicator over these regions it will be
found necessary to adjust the assembly as described at
the end of this section.
Operation
Place the Torsiometer on the specimen. This is done in
three stages, referring to Figure A2.
I. Push one end of the specimen firmly into the socket
mounted on the tailstock of the Torsion Machine.
Separate the Torsiometer into its three main
components - the two end clamps and the
cylindrical centre spacer.
Rod
I~"
,-
End
,clamp
-1$1-
End
I
cap'" r , -'1~ 1t"-T- ,/ End
\
.-" cap
.~
/
Cap
screw \
End
Knurled
clamp Centre nut
Figure A2 Layout of the torsiometer
spacer
'Cap
screw
Page A-2

Ta Torsion Testing Machine
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2.
3.
Slide the cylindrical spacer over the specimen and
onto the spigot on the right-hand end clamp.
Place the remaining end clamp onto the specimen
taking care to locate the spigot on this end clamp as
far as possible into the open end of the spacer. Turn
the end lamp until the dial gauge plunger contacts
the flat on the end of the rod. The dial gauge should
be in such a position that the dial is clearly visible.
Hold the three components together and ftTDlly
tighten the cap screw in the left-hand end clamp.
The spacer should just be free to rotate without any
end play. The whole assembly firmly fixes to the
test specimen and the tailstock can be slid along the
bed until the free hexagon end of the specimen is
inside the headstock socket. Lock the straining head
in position.
The Torsiometer is now ready for use. Should the full
scale deflection of the dial gauge be insufficient at this
first clamp position of the rod it may be adjusted to
register further straining of the specimen by just
slackening the knurled nut and resetting the position of
the rod. In this way the position of the TorsioI11leter
clamping on the specimen is in no way disturbed, and
continual adjustment throughout the whole loading
range is obtained.
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