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The method of administering thesis work in general involves the following steps: A list of problems, to which, on account of limitations of equipment and the desire to concentrate, the work of the laboratory should be confined, is prepared early in the year. Theses subjects are generally chosen from this list by students. When a subject is chosen by a student, a thesis outline is prepared by the professor in consultation with the student, in which the problem is clearly stated; the authorities, if any, cited; a list of literature, or directions to main source of information given; and the main plan of attack fairly definitely indicated. Details of apparatus, etc., are generally left to the student. At times a student presents a subject of his own choice. It is thought that it is better that he should be given sufficient guidance and should thus come to the end of the year with some definite conclusions reached, than that his energy should result in a mass of tangled data such as the average undergraduate obtains by his own inexperienced planning. Insistence is placed upon form of presentation and analysis of the subject. The written thesis covers a clear and logical account of the purpose of the thesis; the material tested; the methods and machines, with a discussion of error; the actual results; the analysis and presentation of the results; and the conclusions therefrom. All data remain the property of the university and publication of the results may only be made by the student with the consent of the University authorities.
MACHINES AND APPARATUS. The equipment in a testing laboratory in a State University is primarily for routine instruction and incidentally for research and for assistance to the various technical interests of the State or the general public. This equipment should include a preponderance of small machines suitable for routine experiments. The author has found a 30,000 pound universal knife-edgelever machine best suited for this purpose. It should be operated by power and spur gearing. The poise should be a dial poise. Naturally, in this country the choice will be between the Olsen and Riehle type of machine. The speeds should be as follows:
Up and down fast speed for adjusting 24 inches per minute.
Down for flexure .15 inches per minute.
It will be of no particular advantage to have this machine automatic or autographic.
Flexure tests are provided for by placing a small “I” beam across the platform of the testing machine. The machine should be calibrated either by special levers or else according to the practice of the author, by the use of a standard nickel-steel bar whose modulus of elasticity is measured with a calibrated extensometer. The bar is kept in the laboratory and is not strained beyond its elastic limit. In three instances in the author's experience this calibration has been found necessary. A nut on the bed of the machine calibrated had worked loose and through lack of clearance had blocked the main lever at a load on the testing machine of one half its capacity.
For the work of thesis investigation and tests for outside parties machines of large capacity are needed. Such a machine serves for tests on columns, girders, couplers, draft rigging and miscellaneous railway appliances, reinforced concrete beams and “I” beams. Such a machine should have vertical head room of at least ten feet and a distance between screws of twentysix inches.
A cross table for flexure is not necessary and may be provided for by an “I” beam. The futility of providing a cross table designed for the full capacity of the testing machine, as is sometimes the case, is evident.
The capacity of the large machine is a matter needing discussion. The author would provide for a 200,000pound machine, and then jump to one of large capacityover 600,000 pounds. A machine of the latter type need not be a knife-edge machine. It is only useful for testing manufactured articles or large structures in which there is a great inherent variability. A machine whose accuracy is in keeping with such material may be of the hydraulic type. The load may be measured upon a diaphragm gauge. A horizontal machine seems the most convenient. A machine may be calibrated from time to time by the use of a large nickel steel bar with extensometers. This will check up any great variation in friction in the packing of the piston.
A torsion machine should be provided to illustrate the laws of torsion. A 60,000-inch pound machine will be sufficient. Some form of impact machine serves well to illustrate the phenomena of rupture under impact, and the mechanical relations between work and energy. A convenient form of machine is the one recently built by Purdue University for the Bureau of Forestry providing for compression and flexure impact tests. The hammer varies from 50 to 250 pounds. The fall is six feet. The base is seven feet long. Total weight of machine is about 4,000 pounds. The hammer is lifted by an electric motor though the medium of an electric magnet. A gentle and convenient release is brought about by cutting the current off from this electric magnet. There is a pencil attached to the hammer which writes a curve on a revolving drum, whose speed is shown by the record of the tuning fork thereon.
Further apparatus will naturally be governed by the individual interests of the professor in charge, and the interests of the State which the laboratory serves. There is no need of providing certain special apparatus in all laboratories any more than there is need for duplication of highly specialized courses of instruction in some particular branch of technology in two universities near at hand to each other.
Extensometers. The commonly used, electric contact extensometer reading to one ten thousandth of an inch, teaches care of manipulation, but the deformations at the elastic limit and yield point are not evident to the senses as they are in a roller extensometer. The author has found the Johnson extensometer most favorable to the work of instruction and research. He has not found it possible in his laboratory to use the mirror extensometer on account of the jarring of the machinery resulting from the general work of the laboratory.
A compressometer reading to one ten thousandth of an inch is highly useful in determining the fundamental properties of brittle materials, and a number of deflectometers reading to one hundredth of an inch are useful for flexure tests.
The Henning Recorder is a very useful apparatus from an educational standpoint. The rupture-work and the relations of the various constants of the material are brought distinctly to the notice of the students.
The usual micrometers and scales need not be described. A note may be made concerning the usefulness of plaster of Paris in testing concrete or stone specimens.
A drying oven is often needed to determine the moisture in wood, or to dry out bricks before testing. Some form of abrasion machine is useful in preparing stone specimens for compression tests.
The standard equipment of a cement testing laboratory should be included. The automatic shot machine is no doubt the best type of these machines; a type in which the load is applied through the flow of shot from the bucket has proved satisfactory to the author. Mechanical mixers, molders and tampers are of a doubtful value.
As indicative of the growth of the equipment of a laboratory, the following list is given of the machines in the Laboratory for Testing Materials of Purdue University:
One 300,000-pound Universal Riehle testing machine capable of testing specimens in compression up to ten feet in length. This machine is used for testing concrete beams, draft rigging, car bolsters and large work.