DESIGN AND DEVELOPMENT OF AN
ECONOMICAL
TORSION TESTING MACHINE
by
Glenn Vallee, Ph.D., P.E.
And
Robert Short
Mechanical Engineering Department
Western New England College
Project Objectives
• Design and build a torsion testing
machine capable of performing the
ASTM Torsion Test
• Machine must measure material
properties to within 5% of published
data
• Machine must be affordable
Torsion Testing Apparatus
• Experimentally determines torsional shear
properties of materials
• A cylindrical test specimen is twisted until
failure
• Applied torque and angle of twist are recorded
• ASTM Standardized Test Method Used
- Specifies Test Procedure / Specimen Geometry
Design Constraints
• Machine must be capable of fracturing a
steel test specimen
• Specimen diameter to be 3/8 inch to allow
examination of fracture surfaces
- ASTM therefore requires a specimen length of
6 inches to meet the min length/diameter ratio
• Torque and angle of twist measuring
devices to be easily accessible to
students
Design Constraints
• Machine must produce measurements
within 5% of published ASTM results
• Budget allocation of $500
• Many Years of Service!!!
Determination of Shear Properties
• Elementary mechanics theory used to relate
applied torque, T to shear stress, τ using
Eq. (1)
T

J
where ρ = radius of the specimen cross section
J = polar moment of inertia of cross section
• Shear strain γ is calculated using
Eq. (2)
γ = ρθ/L
where L = specimen length
θ = angle of twist
Determination of Shear
Properties
• Shear Modulus G is determined by finding the
slope of the shear tress-strain diagram
• Shear modulus may also be calculated using
Eq. (3)
TL

GJ
Design – Torque and Angle of
Twist Requirements
• Equation (1) was used to estimate the
torque required to yield a C1018 plane
carbon steel test specimen in torsion
• 3000 in-lb would be required to fail
C1018 material at constant rotational
velocity
• Experiments were performed using
aluminum to find required angle of
twist (10 revolutions)
Design Layout
FIXED HUB
STRAIN GAGE
ROTATING HUB
SPECIMEN
T-SLIDE
UNIFORM BASE PLATE
CHUCKS
SPROCKET
Drive Train
• A DC motor with an integral gear reduction and speed
controller was used
• A sprocket set having a 6:1 gear ratio developed required
torque
Frame Design
• Two inch square steel channel was welded
together to form the frame
Base
Frame / Motor Sub Assembly
Measurement of Torque
• A torque gauge was fitted to the fixed hub
Gage mounted on
a 45° Angle
Torque Gage
Measurement of Torque
• Strain Gauge aligned with direction of Max Principle
Stress
 max (kpsi)

2Ө
σ2

σ2 = 
State of Pure Shear
σ1
σ (kpsi)
45°
σ1 = 
Measurement of Angle of Twist
• A potentiometer was mounted to a wheel
which contacted the rotating hub.
Weight
Potentiometer
Sprocket
Wheel
Chuck Alignment
• A T-slide was used to prevent development
of axial loads and to aid in alignment
Torque Calibration
• A weighted lever system was used to calibrate
the torque gauge
Gage
Fabricated Torque Wrench
Torque Calibration Curve
Torque (in-lb)
Torque vs Strain
1900
1800
1700
1600
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
Torque vs Strain Calibration Curve
Western New England College
1215 Wilbraham Road Springfield MA
Mechanical Enigneering Laboratory
Generated by Robert Short
April 11, 2005
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000 1050 1100
Strain (m icro in/in)
Experimental
Theoretical
1150
1200 1250 1300 1350 1400 1450 1500 1550 1600
Complete Assembly
Strain Gauge Leads
Potentiometer Leads
Motor Speed
Control
Power Switches /
LEDs
Performance
• Data Collection with Lab VIEW
• Testing of 1018 Cold Drawn Steel
– Shear modulus measured as 10.7 Mpsi, 3%
lower than the published value
• Testing of 2014 Aluminum
– Shear modulus measured as 3.7 Mpsi, 5%
lower than the published value
Budget Analysis
Item Description
Manufacturer
Mfg. #
Vendor
Vendor #
Quantity
Cost Ea. ($)
Total Cost ($)
DC Motor
Dayton
4Z530
Grainger
4Z531
1
258
258
DC Speed Control
Dart Controls
125DV-C-K
Grainger
2M510
1
77
77
2 inch Sprocket
US Tsubaki
50B9F
Grainger
6L927
1
11
11
12 inch Sprocket
Browning
50Q60
Grainger
1L213
1
93
93
Chain (10 feet)
US Tsubaki
50TW10
Grainger
2W095
1
34
34
Potentiometer
EIT
MW22B-10-2K
Newark InOne
83H7568
1
10
10
Drill Chuck
Jacobs
30602
McMaster
3094A17
2
19
38
Neon Lamp Assembly
Radio Shack
2720712
Radio Shack
2720712
1
4
4
Neon Lamp Assembly
Radio Shack
2720708
Radio Shack
2720708
1
4
4
Dual Binding Post
Radio Shack
2740718
Radio Shack
2740718
1
5
5
Final Cost ($)
534
Integration Into the ME Curriculum
• Torsion machine has been integrated in
two ways
- ASTM torsion experiment has been
included in the junior laboratory sequence
- design and use of the torsion machine is
introduced in the sophomore Mechanics of
Materials course
Junior Laboratory Experience
• Students examine the torque cell and
calculate its limiting torsional strength
• Students create calibration curves for
the torque cell and rotational
potentiometer
• Steel and aluminum specimens are
tested o failure and the results are
compared to published data
Mechanics of Materials Course
• Students examine the torque cell and
calculate its limiting torsional strength
• ASTM torsion test is performed in class
• Students determine the shear stressstrain diagram for steel and aluminum
and determine their shear modulii
• Shear failure surfaces are examined
QUESTIONS?