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constantly thrusting itself into prominence in some form. For the honor of human nature, it is gratifying to be able to put on record that during nearly thirty years of almost constant testing, only once have direct financial considerations been urged upon us to influence our verdict in regard to material. On the other hand, we have heard representatives of entirely reputable business organizations say openly, “It costs us something to sell our goods, and it is entirely immaterial to us whether this money goes to our selling agents, or to the representatives of the consumers.” And this is not the worst phase of the matter. It is well known that the representatives of consumers who act in some sense in the capacity of testing engineers, in that their opinion or decision determines the placing of orders, not only accept substantial considerations from producers, but even demand them, if not openly, at least indirectly. The subject is one on which much might be said. An hour could readily be filled in narrating incidents and portraying the forms in which the hydra-headed monster, graft, manifests itself. We are confident that neither side is free from blame: we are equally confident that strict, open honesty is the only safe course. It may not be amiss to add that so insidious are the forms in which this evil manifests itself, that, in the words of the Scripture, they would at times deceive the very elect, and while it is not possible to discuss these matters without raising interminable questions of casuistry and metaphysics, it is possible to so act as to have the continuous approval of a good, clean conscience. No universal rule can be given. Each one in a sense must be a law unto himself. Perhaps the best every-day

working rule for young testing engineers is, do nothing you would not be willing to talk over with your employer, even in the presence of the other party. It is sometimes a bit hard to resist and say “no," but of one thing be sure-every departure from strict integrity will, sooner or later, return to plague you, and should your actions ultimately result in your downfall, from none will you get less sympathy than from those who may have contributed to your disaster.

A LABORATORY COURSE IN TESTING MATERIALS

OF CONSTRUCTION.*

BY W. KENDRICK HATT,
Professor of Applied Mechanics, Purdue University.

Prefatory Note.- A laboratory course of practice in the determination of the mechanical and physical properties of materials, commonly called “testing materials,” has come to be a part of an engineering course, either as a separate course or as part of a course in the general engineering laboratory. The author does not know of any special discussion of the content and method of administration of such a course, and here presents such a discussion with the desire of obtaining criticisms from professional testing engineers. This paper is based upon the course developed in the Laboratory for Testing Materials of Purdue University. The practice of administration of the course as far as the sequence of experiments is concerned it not wholly logical, but is conditioned by the necessity of arranging instruction for large sections of students.

OUTLINE OF WORK IN LABORATORY FOR TESTING

MATERIALS. Aims.- The aims of administering the work in the laboratory are as follows:

1. The student is to obtain a knowledge of materials * The author desires to acknowledge the assistance given by Messrs. E. J. Fermier and E. L. Hancock, instructors in applied mechanics in Purdue University, in the preparation of the above paper.

by handling them and watching their behavior under stress. From the appearance before and after test he is led to recognize the nature of normal and defective samples, and the degree of uniformity to be expected. This knowledge will give character to the work of engineering design, and will be of service in work of inspection.

2. A knowledge of the technique of testing materials is gained, by which he may know afterwards if proper methods are being used in cases that come under his inspection, and by which he may judge the significance of results of the tests of material submitted to him.

3. A training is given in precise methods of observation.

4. The class-room instruction in Applied Mechanics is reinforced with concrete knowledge of things and properties, which are otherwise only words defined in textbooks. The application of theoretical analysis to the tests performed in the laboratory becomes of individual interest and is fixed in the mind. Discrepancies between theoretical deductions and results of tests of actual material as supplied to the market also become evident. Many of the fundamental facts relating to metals, such as the relative stiffness of hard and soft steel, the elevation of the yield point, and the lowering of the elastic limit through overstrain can also be brought to the student's notice by a few well-selected experiments.

5. Thesis work in testing materials presents a ready and attractive medium by which students can receive some training in proper methods of planning and executing experimental investigations. The work may be

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individual, or performed by groups of students, and the expense of material is small. If the professor is interested in some one field of investigation and systematically plans or lays out the field for a term of years, the theses in time are of use in extending knowledge.

Methods of Instruction.- Work is assigned from day to day according to the progress of the student. The laboratory work is self-contained, i. e., the work is all to be performed during the time assigned by the faculty and the calculations are performed and the reports written up under the eye of the instructor. The students work in parties of three. An outline of the experiment is given to the student before performing the test. The data is taken and the reports are handed in as results. Slide rule calculations are used. From time to time lectures are given explaining the manufacture and properties of the common materials tested, and dealing with the technique of testing.

One valuable feature of the work as administered is that the student is referred to standard text-books and standard specifications, and is asked to ascertain how far the material tested deviates from the character of the normal material. At times materials are given to the student without description or name and he is asked to make tests and determine their commercial rating.

The specifications on hand are: American Society for Testing Materials; Pennsylvania Railroad, and J. I. Case Threshing Machine Company. The volumes in the laboratory are in part:“Reports of Tests of Metals, Watertown Arsenal”; “Materials of Construction," by J. B. Johnson; “Masonry Construction," by I. O. Baker; and “Handbook of Testing Materials,” by A. Martens (translated by Gus Henning).

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