. Cassier's magazine . weight was suspendedat the end. The results obtained by Wohlerwere many and important. Theysubstantiated, for the first time, bydirect numerical data, the statementthat the range of stress had an effectupon the number of revolutions anaxle could run before fracture. Withmaximum values of tons persquare inch tension and compressiona material (homogeneous iron) wasrotated 2,375 times and then frac-tured. With maximum tons persquare inch for these stresses 94,311revolutions were recorded. Withmaximum values tons per squareinch 3,930,150 revolutions were madeb
. Cassier's magazine . weight was suspendedat the end. The results obtained by Wohlerwere many and important. Theysubstantiated, for the first time, bydirect numerical data, the statementthat the range of stress had an effectupon the number of revolutions anaxle could run before fracture. Withmaximum values of tons persquare inch tension and compressiona material (homogeneous iron) wasrotated 2,375 times and then frac-tured. With maximum tons persquare inch for these stresses 94,311revolutions were recorded. Withmaximum values tons per squareinch 3,930,150 revolutions were madebefore fracture. The results onKrtipps cast-steel axles were equallystriking. With alternating tensionon compression tests of tons persquare inch 55,100 revolutions weremade. When the stresses were the number of revolutions was45,050,640. It is worth noting thatthis material which failed at tonsafter forty-five millions of alternatingstresses carried tons per square ALTERNATING STRESS TESTING 425. FIG. 3.—wohlers alternating stress bending machine A A, the specimens. D D, rigid bearings. B> pulley. C, mandrel. F F, springs. G G, nutsto regulate pull-on springs and specimens. inch during the ordinary tension test. professor Arnolds machineThe well-known metallurgist whoholds the chair of that science in theUniversity of Sheffield conceived theidea of making the Wohler type ofalternating stress tests more possiblefor commercial work by reducing thetime taken. He therefore devised amachine (shown diagrammatically inFig. 5) which stressed the materialjust beyond the elastic limit. Theevidence which has been supplied bythe numerous tests made by Profes-sor Arnold shows that his method ismore practical and more useful thanWohlers for commercial work. Itis, however, of no value in the ratherfascinating- search after the causes ofelastic breakdown of steels. In this same catalogue of bendingstress machines may be placed thatdevised by Captain Sankey. This is
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