. Steel rails; their history, properties, strength and manufacture, with notes on the principles of rolling stock and track design . astic movementsof the metal aggregating considerable distances. The aggregate extension ofthe most strained fiber of the .82 per cent carbon steel which has successfullyendured 202 milhon repetitions amounts to nearly 5 miles per linear inch ofspecimen, a distance quite incomparable to the permanent extension of themetal in the tensile test. * Little attention seems to have been given to the possibility of findinga relation connecting the stress used in endurance
. Steel rails; their history, properties, strength and manufacture, with notes on the principles of rolling stock and track design . astic movementsof the metal aggregating considerable distances. The aggregate extension ofthe most strained fiber of the .82 per cent carbon steel which has successfullyendured 202 milhon repetitions amounts to nearly 5 miles per linear inch ofspecimen, a distance quite incomparable to the permanent extension of themetal in the tensile test. * Little attention seems to have been given to the possibility of findinga relation connecting the stress used in endurance tests with the number ofrepetitions required for rupture. Spangenberg, Reynolds, and Smith, and *The Exponential Law of Endunmcc Tests, O. H. Basquiu, Proceedings of the Auieiiean Soeietyfor Testing Materials, 1910, Vol. X, p. G25. STRENGTH OF THE RAIL 281 Stanton and Bairstow, have shown stress-repetition curves drawn to ordinaryCartesian coordinates. Logarithmic coordinates present a distinct advantage in the study ofsimple exponential curves, because these curves become straight lines for these REPEATED ALTERNATE 600000 grade: .I?C. .3,4C. .55C. .73C. .82C. I09C. 51,000 54,000 59,000 64,000 64,000 Fig. 202. — Comparison of the Behavior of Different Grades of Steel under Repeated Alternate Stresses(Am. Soc. for Testing Materials. —• Howard.) coordinates and their equations may be written at once. Fig. 203 showsstress-repetition curves for nineteen sets of endurance tests, made by five dif-ferent observers. The names of the experimenters, the kind of test, and the material are given in Table LXX. 282 STEEL RAILS TABLE LXX. —EXPERIMENTS ON REPEATED STRESS (Basquin) CurveLetter. A B C* D* E F G H J Lt M N 0 P Qt m TU Experimenter. Wohler tiIItii( at(a t ci Iit Benjamin Reynolds & Smith F. Rogers Foppl Kind of Test. Material. Wrought-iron axles, Phoenix axles, Phoenix Cast steel,
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