TELEPHONE APPARATUS SPRINGS 



263 



cycle graphs shown by Figs. 2 to 6 give typical results. The design 

 of specimen is shown by Fig. 7. These specimens were alternately 

 stressed at the rate of 700 cycles per minute. 



IqS I06 10'' 10^ 



OP ERATIONS 



Fig. 5 — Fiber stress vs. fatigue — nickel silver sheet — 24 gage — 10 Nos. hard: 

 A, average of three specimens taken frorn test without failure. 



<«30 



10* 106 10^ 10^ 



OPERAriONS 



Fig. 6 — Fiber stress vs. fatigue — ^phosphor bronze sheet— 24 gage— 10 Nos. hard: 

 A, average of two specimens taken from test without failure. 



