. Steel rails; their history, properties, strength and manufacture, with notes on the principles of rolling stock and track design . few crystals after a few, say, 5000reversals of stress; with a greater number, say, 40,000, the shp bands increasein number, and those which first appeared broaden and develop into smallcracks, as shown in Fig. 197. If the specimen be repolished, so as to clear off the slip bands, the cracksalone become visible, as at A (Fig. 198). The crack, or flaw, gradually creepsacross the specimen when the number of alternations is still further increased,as shown in Fig. 1
. Steel rails; their history, properties, strength and manufacture, with notes on the principles of rolling stock and track design . few crystals after a few, say, 5000reversals of stress; with a greater number, say, 40,000, the shp bands increasein number, and those which first appeared broaden and develop into smallcracks, as shown in Fig. 197. If the specimen be repolished, so as to clear off the slip bands, the cracksalone become visible, as at A (Fig. 198). The crack, or flaw, gradually creepsacross the specimen when the number of alternations is still further increased,as shown in Fig. 199. Finally the specimen breaks. Ewing and Humfrey state: Whatever the selective action of the stressis due to, the experiments demonstrate that in repeated reversals of stresscertain crystals are attacked, and yield by slipping, as in other cases of non-elastic strain. Then, as the reversals proceed, the surfaces upon which theslipping has occurred continue to be surfaces of weakness. The parts of thecrystal lying on the two sides of each such surface continue to slide back andforth over one another. STRENGTH OF THE RAIL 275. Fig. 197. — SUp Bands. (J. W. Ewing and J. C. W. Humfrey.)
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Keywords: ., bookcentury1900, bookdecade1910, bookidsteelrailsth, bookyear1913
