738 BELL SYSTEM TECHNICAL JOURNAL 



(a) (b) (c) 



So 



S'So 



Fig. 8 — Stress conditions in a strain-annealed clutch spring. 



steel ^ a number of springs of 0.0068 X 0.021-in. ribbon were wound on 

 0.1486-in. arbors and given various heat-treatments. They were then 

 cooled, released from the arbors, and measured for inside diameter. 

 Table 1 gives the results of these measurements. 



TABLE 1 



Effect of Heat-Treatment on Springs 



Ribbons of 18-8 stainless steel, 0.0068 X 0.021 in., heat-treated on 



0.1486-in. winding mandrels 



The residual stresses were calculated by noting from equation (23) 

 that Sr = S2IS and then obtaining ^'2 from equation (20) rewritten as 



h Ri - Rt 



2R\ Rq 



' 8 per cent nickel, 18 per cent chromium. 



E. 



(25) 



