Objective by nikeborome


									                             Torsion of Prismatic Bars
                              ME 272 Experiment #5

  The objective of this experiment is to develop an experimental method utilizing the
  torsion testing apparatus that will determine the relationship between / angles of twist
  (0 to 3 degrees) and torsional load.

Reference: Sections 2.14 - 2.15 and 3.1 - 3.5 in Mechanics of Materials; Beer, Johnston,
   and DeWolf

NOTE: Do Not Exceed The Maximum Load Posted ON The Apparatus.

  For this experiment, you will be utilizing the torsion test machine. There is one
  output and one input for this machine. The input is the twist applied to the specimen.
  The value of this twist is the amount of rotation applied to the right side of the
  specimen by the hand crank. This is read from two different degree wheels. The one
  on the right side of the machine measures 360o per revolution. The wheel facing the
  front of the machine reads a much more precise 6o per revolution. Most of your
  readings will be made from the 6o degree wheel, using the 360o wheel to keep track of
  how many revolutions the other wheel has completed. The output of this machine is
  the applied torsional load. This is read from the digital load cell interface as Nm.

Test sample installation:
   The lower clamp on the right side of the machine allows for the lateral movement of
   the input shaft to accommodate samples of various lengths. With this clamp
   loosened, slide the input shaft to the right enough to allow the sample to fit between
   the input shaft and the pendulum shaft. Install the sample into the socket on the input
   shaft. After firmly tightening the clamp on the input socket, slide the input shaft
   towards the pendulum shaft until the sample is far enough into the other socket.
   Because the end of the sample is hex shaped, you may have to rotate the hand crank
   to allow the sample to align with the clamp on the pendulum shaft. Tighten the lower
   clamp and the socket clamp on the pendulum shaft. For the circular cross section
   rods, the length is the length of the circular area. For the hexagonal cross section
   rods, the length is the distance between the clamps of the apparatus, which needs to
   be set to the free length of 4 inches.

       1. Document this experiment with a formal lab report following the report
          guidelines set forth in the ME 272 lab manual.
       2. Design an experiment that will accomplish the objective. This will be
          documented in the experimental procedure section of the report
       3. Create plots showing the torsional load/twist relationship for each specimen.
          The shear modulus should be determined by the analysis of the circular cross
          section plots. The plots of the circular cross section rods are of little concern
          to the readers, therefore, it would be appropriate to only include these in the
       4. Present the shear modulus, plot of torsion versus twist, plot of torsion versus
          shear stress, and the obtained functions of these for each of the materials in
          the Results section.

Figure 3-1

                               Torsion of Prismatic Bars
                                ME 272 Experiment #5
                                 Pre-Lab Assignment

1. What is the primary equation that relates applied torque to resulting twist?

2. When plotting torsion vs. twist, what is the equation defining the slope, m, of the line?

3. Given the following experimentally obtained data, determine the shear modulus and
   identify the material. (use the slope of the trendline to determine shear modulus)

Show all calculations as well as a plot of torsion vs. twist.

   Sample is a circular cross-section rod
   Radius = 1.5 cm
   Length = 15 cm

                Data Point            Twist (degrees)            Torsion (Nm)
                    1                         2                      296.1
                    2                         4                      592.2
                    3                         6                      888.3
                    4                         8                     1184.4
                    5                        10                     1480.4


To top