TIRED PETALS

Gisborne Times, Volume LXXXII, Issue 12534, 22 April 1935, Page 2

TIRED PETALS

AN INTERESTING DISOQVER.Y. Professor E. N. da O. Andrade, of London, lias discovered that even the purest metal can get tired. It is a conclusion of considerable importance to engineers as well as to all those whose lives depend on : the smooth working of machinery. “Fatigue” in a metal mean's its' liability to fracture under - continually repeated stress, and there are few machines of structural components the working conditions of which can be so adjusted as tp exclude this possibility. On the contrary, the whole tendency. to-day is toward higher engine speeds and working stresses, and on a conservative estimate 80 per cent, of all failures in modern engineering practice can be attributed to fatigue. Breaking as a result of fatigue is accompanied by a “slipping” of successive layers of crystals in the metal. This slipping can be seen under the microscope. Hitherto it has been generally believed that "slipping,” and therefore fatigue, was caused by the presence of impurities in the metal. Now' Professor Andrade has taken the purest metal which he could find, mercury frozen solid at a temperature of some 60deg. below zero, and he finds that “fatigue” is' actually greater than if the metal is less pure. It now appears certain that metallurgists havo been oil the wrong track in thinking that they could reduce' fatigue by eliminating impurities. If a. solution is to be found of. one of the pressing problems of modern engineering, Professor Andrade has shown that it must be along other lines. ’