Lab 1_torsion Experiment.pdf 455m34

FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA JOHOR(KAMPUS PASIR GUDANG) Laboratory Manual # 1

COURSE

BASIC STRUCTURAL ANALYSIS

COURSE CODE

ECS258

LEVEL OF OPENNESS

0

CATEGORY

TRADITIONAL

DEGREE OF OPEN-ENDED (%)

0

PERIOD OF ACTIVITY

1 WEEK

TITLE

TORSION EXPERIMENT

1.1 Introduction The traditional methods of conducting laboratory activities (assigned as Level 0) will not be able to provide the avenue for students to enhance independent learning activities and inculcate creativity and innovation. The traditional method is fully prescriptive where the three elements namely problem, ways & means and answers are guided/fully given to the students. However, it is still necessary to be implemented as part of the whole laboratory course activity especially to first and second year students. In this laboratory activity students will be exposed to the apparatus and the procedures to carry out torsion experiment. 1.2 Objective The objective of the experiment is: To determine the relationship between the applied torque and the angle of twist and hence obtain the shear modulus. 1.3 Learning Outcomes PREAMBLE

At the end of the laboratory activities, students would be able to:   

identify and use the correct apparatus/tools to carry out torsion experiment; work in a group to undertake the task; and collect and analyze the data correctly and produce the lab report.

1.4 Theoretical Background Shear modulus is a material property that is useful in calculating the compliance of structural materials in torsion, provided that they follow Hooke’s law – that is the angle of twist is proportional to the applied torque.

FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA JOHOR(KAMPUS PASIR GUDANG) Laboratory Manual # 1

Typical value for shear modulus: Material

Shear Modulus (GPa)

Aluminium

26-28

Brass

36-41

Steel

70-81

(Source: Torsion Apparatus Manual by Dr Maslin Hassan)

FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA JOHOR(KAMPUS PASIR GUDANG) Laboratory Manual # 1

PROBLEM (Guided)

2.1 Problem Statement Students are required to conduct torsion experiment to determine the shear modulus of a structural material such as steel, aluminium, etc. 3.1 Apparatus  Torsion experiment apparatus  Test specimen  Vernier caliper

WAYS & MEANS (Guided)

3.2 Procedures 1) Switch on the digital protractor and the load indicator unit to warm the systems. 2) Measure the length (only the round section) and diameter of the specimen. 3) Mount the torsiometer approximately at the center of the specimen setting and set the dial gauge reading to zero. 4) Loosen the top screw that is attached to the specimen setting bar. 5) Attach a socket to the end of the specimen setting bar. 6) Place the specimen in the socket. 7) Place another socket at the free end. 8) Push the specimen setting bar towards the other socket. Once the specimen is in with the socket, try to push the specimen so that it slides into the socket. If this is not possible, turn the handle to rotate the socket slightly so that the specimen can slide into the socket. 9) Once the socket and the specimen are in line, push the specimen until the whole hexagon portion is completely inside the socket. 10) When the hexagon portion is completely inside the socket, lock the position of the specimen setting bar by tightening the top and bottom screws. 11) Set the load indicator reading to zero by pressing the tare button. 12) Set the digital protractor reading to zero by pressing the R button. 13) Set the torsiometer reading to zero by turning the dial indicator face. 14) Turn the handle until the load cell records a small reading (approximately 5 Newtons) and the specimen is tight. This is a preload condition. 15) Set the load indicator, the digital protractor and the torsiometer reading to zero by pressing the tare button, the R button and turning the face of the dial gauge, respectively. 16) Apply torque to the specimen by turning the handle. 17) Record the load cell, the digital protractor and the torsiometer readings initially for every 5 divisions of the torsiometer. 18) Increase the applied torque and for each increment record the corresponding angles of twist. 19) When the torsiometer reading starts to increase rapidly, remove the torsiometer to avoid damage. 20) Continue increasing the load until the specimen breaks. 21) If the experiment is to be conducted in the linear range only, it is advisable that the torsional stress should not exceed 0.3 the yield stress of the material. 22) When conducting test to destruction, remove the torsiometer when the specimen approaches yield.

FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA JOHOR(KAMPUS PASIR GUDANG) Laboratory Manual # 1 3.3 Results The group is required to perform the data acquisition process and complete the information required and Table 1 below. Length of specimen, L

=

mm

Diameter of specimen, D

=

mm

Polar moment of inertia, J

=

mm4

Gauge length ‘torsiometer’

= 50

mm

Torque arm, L

= 100

mm

Note: 1 division represents 0.01 degrees on the torsiometer. Table 1 Load Cell, W

Applied Torque, T = W*100

Torsiometer (Angle of twist), θ

(N)

(Nmm)

(Div)

Torsiometer (Angle of twist), θ = Div*0.01*pi /180 (Radian)

4.1 Analysis From the information obtained and data in Table 1: 1) Draw the graph of applied torque, T (Nmm) versus the angle of twist, θ (Radian). 2) Draw the best fit line through the plotted points. 3) Determine the slope of the graph (T versus θ). 4) Determine the shear modulus, G of the material. ANSWERS (Guided)

4.2 Discussion 1) Describe the relationship between applied torque and angle of twist. 2) If the specimen is tested to failure, describe the failure surface. Does it reflect the type of material (brittle or ductile) being tested? 4.3 Conclusion 1) How does the value of G obtained from the experiment compares with that normally assume in practice for the material being tested? 2) What are the possible errors in this experiment? The report must be submitted 1 week after the completion of this laboratory work.