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ME312Exp2 2009 by 0268l4DJ


									CE/ME 312
Experiment 2

                             TENSILE TEST OF ALUMINUM AND BRASS

References:                    The Testing and Inspection of Engineering Materials, by Davis, Troxell,
                               and Wiskocil, Chapters 1, 2, 3 (3.1-3.6), 4(4.1-4.11), 5 (5.1-5.7), and
                               Appendix A(A.1-A.5).

                               Experimental Mechanics and Properties of Materials, by Muhlenbruch,
                               Exp. 9.

Equipment:                     Tinius-Olsen, 200 kip, pit mounted, Universal Testing Machine, or
                               Tinius-Olsen, 400 kip, Universal Testing Machine, micrometer (0 - 1
                               inch), ball micrometer (0.2 - 1.2 inch), steel scale (12 inch), dividers,
                               extensometer, 2-in. gage point punch.

Test Specimens:                Standard test specimens with 2-inch gage lengths; 7075 – T651
                               aluminum alloy, and #464 hard naval brass.

Test Procedure:                Students must have a clear understanding of how to operate the
                               Tinius-Olsen UTM before starting an experiment with this
machine. Measure the minimum diameter of the specimen to the nearest 0.001 inch and record it.
Compute the cross-sectional area, and estimate the loads at which the yield strength and ultimate
strength will be reached. On the floor of the laboratory, place the specimen in the marking punch,
and mark the specimen with the 2-in. gage length by applying a light to medium hammer blow. Enter
the required specimen data into the computer. Once the Tinius-Olsen UTM is properly prepared,
install the specimen in the test fixture as demonstrated by the lab technician or instructor.


With the instructor present, apply an initial load of about 100 lbs. to insure a solid grip. Carefully and
properly attach the extensometer to the specimen. Set to zero the load and strain scales on the 398
display unit. Begin the test by clicking the start button on the computer monitor, and then slowly load
the specimen until a load rate of about 1500 to 2000 pounds per minute is reached. Steadily
continue to load the specimen until the UTM’s computer monitor informs the operator to remove the
extensometer. At this point, without stopping the machine or test,


Thereafter, continue to record the elongation by means of the dividers at 0.10-inch increments until
rupture occurs. For this part of the test, the machine speed may be increased. Record the ultimate
and rupture loads. Describe the nature of the fracture and make a neat perspective sketch of it.

                                               Page 1 of 3
CE/ME 312
Experiment 2

                                             DATA SHEET

1. List the experiment number, title, and date.

2. Record the following data:

                Dimensions                        Original                       Final

               Diameter, in.                  _________                        _________
               Area, sq. in.                  _________                        _________
               Gage length, in.               _________                        _________

3. List standard minimum mechanical properties as specified for 2024 - T4 aluminum alloy, and
   #464 hard naval brass.

4. Show the following tabulated data:

                                Load                Elongation
                                 lbs.         in increments of 0.1 in.


Plot the load-strain, P -  , curve, with the data acquisition computer/printer, to show the complete
range of the test, using suitable scales to fit the size of the graph.



On the P -  curve plotted with the data acquisition computer, indicate and label the load points that
correspond to proportional limit, yield strength at 0.2% offset, and the P and  intervals used for
the calculation of the modulus of elasticity.

Using data from the above graph, plot a stress-strain,  -  , curve that includes the load and
elongation data taken after the extensometer was removed. Use proper scales. See the section
entitled “RESULTS SHOWN GRAPHICALLY” of the Standard Mechanical Engineering Laboratory
Report Manual for detailed instructions on graphically presenting experimental data and results.
Indicate and label on this graph the points for ultimate strength and rupture strength.

Calculations and Tables

           Determine and tabulate values for the following:

           (a) Proportional limit                       (e) Modulus of elasticity
           (b) Yield strength, 0.2% offset              (f) Modulus of resilience
           (c) Ultimate strength                        (g) Percent elongation in gage length
           (d) Rupture strength                         (h) Percent reduction in area at fracture

                                              Page 2 of 3
CE/ME 312
Experiment 2


1. Do the materials which you have tested have a yield point? If not, what property should be used to
   specify their elastic deformation capacity?

2. Tabulate the corresponding physical properties of A 36 steel (as obtained in Experiment 1) beside
   those obtained in this test for each of the two materials. Discuss the meaning and significance of the
   eight properties listed above.

                                              Page 3 of 3

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