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chinery and all of the coal and lignites to be tested, should be furnished to the government free of charge.

Considerable delay in equipping the plant was occasioned by these provisions, as it was necessary to induce a large number of manufacturers to incur the expense of providing the equipment necessary to carry on the work. Labor strikes at some of the factories supplying the equipment occasioned a still further delay, and the plant was not put in operation until September 1, 1904.

The railroad companies entering St. Louis, or having coal resources along their lines have coöperated most heartily in these investigations, a preliminary report of which may be obtained upon application to the director of the United States Geological Survey.

This exhibit and the Collective Portland Cement Exhibit and Model Testing Laboratory of the Association of American Portland Cement Manufacturers, which is fully described in the paper on the subject, by Mr. Richard L. Humphrey, formed two very interesting features of the exposition. They were working exhibits and accomplished much good in an educational way, besides yielding valuable data relative to fuels and the various building sands and gravels of this country, and were supported with funds available only for the period of the exposition.

The important results obtained and to be secured through a continuance of the work led to an earnest appeal to Congress on the part of those interested in the work which resulted in a liberal appropriation for the continuance of the investigation of fuels and structural materials on a much more extensive plan. With theç appropriation for structural materials which bethe paste can be spread out without cracking on the suface.

Trowel the paste on the glass to thin edges, and set the pat thus made aside in a damp chamber, and observe the time that elapses until (1) it will bear the quarter pound standard needle without appreciable indentation; (2), the weight of the one pound standard needle without appreciable indentation.

Tests for Strength.- Mix up the mortar consisting of three parts standard crushed quartz stone and one part Portland cement, proportion being taken by weight. Mix the sand and cement thoroughly until the mixture presents a uniform color. Gauge with about eight per cent. of water and work over the mixture thoroughly about six times. Tamp in molds in layers, and finish the surface of the briquette. Record the initials on one corner of the briquettes, and leave the briquettes in the molds. They will be taken therefrom by the instructor and placed under water after twenty-four hours.

SECOND DAY's WORK. At the laboratory period one week following, the briquettes are to be taken from the water and tested for strength.

Tests for Fineness of Grinding.- Sift about four ounces of cement through No. 100 and No. 80 sieve and weigh the residue left on the sieves.

The Report.- Each student should report the results of the tests made by him as an individual to determine the fineness of grinding, the time of setting, and the strength of the five briquettes. Reports should be made on blank forms provided for that purpose.

Special instructions are issued to civil engineers.

AN ELEMENTARY COURSE IN PROPERTIES OF

MATERIALS.

BY GEORGE L. CHRISTENSEN, Assistant Professor of Mechanical Engineering, Michigan College

of Mines.

Instruction in the properties of engineering materials should have the following objects in view :

1. To illustrate the behavior of materials under stress.

2. To establish clear and definite conceptions as to the meaning of such fundamental terms as elastic limit, yield point, ultimate strength, percentage of elongation, modulus of elasticity, resilience.

3. To familiarize the student as far as possible with the methods by which materials are tested to obtain numerical results indicating their qualities.

4. To fix in the memory a few of the'average numerical values for the more common materials such as cast iron, wrought iron, steel, timber, stone and concrete; thus establishing a very convenient mental standard of reference for the more detailed study of these and kindred materials, and at the same time forming the basis for that ready judgment so essential to the engineer.

5. To illustrate the use of these numerical values in simple problems of designing, thus associating and connecting the material itself, and the mathematical considerations involved, and laying the foundation for that habit of thought which must ever recognize the material in its various strengths and elasticities, in every problem of design.

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Beginning the course, the first week is devoted to a class-room consideration of definition of terms and the behavior of materials under tensile stress. In the laboratory period of the second week, tensile tests are made of two specimens both cut from the same wrought iron or mild steel bar, one being rough, one inch in diameter, and the other turned down to a smaller size (Fig. 1). The group of ten students gathers around the testing machine, there is room enough for all to note everything that takes place-and each student is

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required to keep full records just as though he were making the test individually. This being the first test, the construction and operation of the testing machine is explained. The rough bar is tested first. It is marked off in the presence of the class, with punch marks an inch apart, and placed in the machine. As the test proceeds, attention is first directed to the detection of the yield point by noting the drop of the beam, then the breaking down action is watched as shown by the loosening of the mill scale, then interest centers in the rapid stretching of the bar, readily noted with a pair of dividers, and finally, in turn, the ultimate load, the

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