FACULTY OF ENGINEERING AND APPLIED SCIENCE
Mechanics of Solids I
Lab Test #4 – Torsion Test
To carry out a torsion test to destruction in order to determine for a 1020 carbon steel rod specimen: 1. The modulus of rigidity, 2. The shear stress at the limit of proportionality, 3. The general characteristics of the torque, angle of twist relationship.
1. Hibbeler, R. C. "Mechanics of Materials", Prentice-Hall, 7th Edition. 2. Instruction Bulletin of Tecquipment Ltd.
Mild Steel rod 6 mm diameter over 3" length (overall length including hexagon ends = 5⅝").
1. Torsion testing Machine and Torsiometer of Tecquipment Ltd. 2. Steel rule and micrometer.
From the general torsion theory for circular specimen:
T Gθ = J l
where, T = Applied Torque; J = Polar Second Moment of Area; G = Modulus of Rigidity; θ = Angle of Twist (over length l); l = Gauge Length. (Nm) (mm2) (N / mm2) (radians) (mm)
1. Measure the overall length and test diameter 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 firmly in the torsion testing machine as indicated in the operating instructions – see later. (If the Torsiometer is to be used the fixed procedure should be carried as prescribed in the last part the bulletin). For each increment of strain record the following: (a) Angle of twist of the specimen (θ) in degrees. (b) Applied torque (T) (c) Angle of twist over the 50 mm (or 2.0 in) gauge length in radians, as recorded by dial gauge indicator (θ) radians. (d) When the elastic limit has been passed, continue to test destruction with increasing increments of strain, recording for each strain increment, i) ii) Angle of twist in degrees; Applied torque.