« ÖncekiDevam »
One 200,000-pound Riehle testing machine, autographic and automatic.
One 100,000-pound Olsen Universal testing machine. One 50,000-pound Riehle Hydraulic testing machine.
One 20,000-pound Falkenau-Sinclair Universal testing machine.
Three 30,000-pound Olsen Universal testing machines.
One Impact testing machine for compression and tension with a drum for automatic records, and mechanical hoist. 500- and 800-pound hammers, nine feet free fall in compression.
One Impact testing machine for compression and flexure tests, electric magnet hoist and release. 50-, 100- and 250-pound hammers, six feet free fall. One Impact testing machine for car axles and
couplers with a 2,000-pound hammer and height of 50 feet. Deposited by the Master Car Builders' Association.
One Abrasion testing machine (deposited), Dorry type.
One Rattler for testing paving blocks, Purdue type.
One Riehle wire tester of 600 pounds capacity, with spring dial.
One Flexure machine for testing cast iron. (Deposited.)
One 2,000-pound Olsen cement testing machine.
One 1,000-pound Fairbanks automatic shot cement testing machine.
One 1,000-pound Falkenau-Sinclair automatic shot cement testing machine.
One 60,000-pound Olsen torsion testing machine.
One 60,000-pound Riehle-Miller torsion testing machine. (Deposited.)
The cabinet of the laboratory contains a good collection of scales, micrometers and instruments of precision.
One Riehle-Yale extensometer.
Two Johnson dial extensometers, with auxiliary yokes for compression tests of concrete cylinders.
One Olsen lever extensometer.
TIME DEVOTED TO WORK. Electrical and mechanical engineers report one period of two hours per week for one semester.
Civil engineers report one period of two hours per week for two semesters.
EXPERIMENTS. A list of experiments from which assignments are made in the author's laboratory is as follows:
1. Commercial Tension Test on Iron and Steel. (Without proportional limit or modulus of elasticity.)
2. Henning Recorder, Iron and Steel.
3. Yale Extensometer, Iron and Steel. (Proportional limit and modulus of elasticity.)
4. Johnson Extensometer, Iron and Steel.
5. Compression Test and Flexure Test of Stone and Brick.
6. Compression Test on Wood.
8. Compression Test on Concrete, using compressometer.
9. Flexure Test of Wood Sticks.
10. Flexure Test of built structures like Brakebeams or Bolsters.
11. Flexure Test of Concrete and Reinforced Concrete.
12. Torsion Test of Steel. 13. Impact Tests. 14. Cement Tests. 15. Specific Gravity of Cement. 16. Wire Rope Test—Test of Separate Wires. 17. Wire Rope Test-Entire Rope. 18. Cloth and Yarn Test. 19. Belt Testing. 20. Cold and Quench Bending Test. 21. Hard and Soft Steel Flexural Test. 22. Effect of Overstrain and Subsequent Annealing. 23. Rattler Test for Brick. 24. Analysis of Data. 25. Test of Draft Rigging. 26. Test of Couplers. 27. Calibration.
FORMS AND INSTRUCTIONS. It is recognized that instruction in a laboratory for testing materials demands a more constant supervision and closer attention on the part of the instructor than is the case in, for instance, a steam laboratory, since the operations of placing material in the machine and attaching micrometers differ with nearly every experiment. Furthermore, the attention of the student should be called to the phenomena which occur in the material under test. Due to necessity, however, of organizing the work for the handling of large sections, it is necessary, as far as possible, to prepare forms directing the operations of the student and instructing him with reference to the preparation of the reports.
Such reports in general should state the purpose of the experiment, the material supplied, the methods of tests, a presentation of the actual data, analysis and exhibition of the data in the form of diagrams, and finally the conclusion, or comparison of the results with standard results. It is not the author's belief that the student's time is profitably used in making elaborate drawings of machines and apparatus used, and it is his practice to do away as far as possible with merely clerical work on the part of students by supplying the proper forms.
There is here appended a number of directions for performing the more important experiments in the laboratory. Such instructions are supplied to students in their work. These are offered with the hope that they may prove of use to other instructors, and with the desire to obtain criticism upon the methods therein outlined. The forms are not complete for all the experiments, but the main experiments are included.
TENSION TEST OF IRON AND STEEL.
I. Purpose of the Experiment. The experiment is intended to represent the conditions obtaining in an ordinary commercial test with the exception that the speed of descent of the pulling head of the testing machine is much slower than customary in commercial laboratories. The experiment will determine the strength and ductility of the material which are the common measures of quality. The kind and classification of the material supplied may be known from the results of the experiment.
II. Preliminary. 1. Note the serial number or mark on the specimen.
2. With vernier or micrometer calipers measure the average dimensions of the cross section.
3. Lay off gauge length of eight inches, each inch being marked by a light center punch mark.
4. Carefully balance the testing machine and then insert the test-piece in the wedges, being careful that the test-piece is centrally disposed in the axis of the machine, and that the ends of the test bar project slightly beyond the wedges. Grip the wedges by applying a load of about 500 pounds. Chalk a small area of the bar near the upper gauge mark. Before proceeding with the test allow the instructor to inspect the work.
III. Operations in Testing. One student should insert one leg of a pair of dividers in the lower gauge mark and scribe a line with the upper leg on the area previously chalked. Apply the load at a low and uniform speed and operate the poise so as to keep the scale beam floating.
The operator with the dividers should notify the operator at the poise when the width of the scribed line increases perceptibly due to sudden increase in the rate of stretching of the test bar under the load. At this time the beam may be expected to drop suddenly and remain down. This increase in elongation without a corresponding increase in loads is the “yield point,” or commercially, the “elastic limit.” It is a point beyond the true elastic limit as obtained in experiment No. 3.
During a further stretching of the bar the beam will