SOLDERLESS WRAPPED CONNECTIONS — PART II 



581 



\\dth 100 turns or more of copper wire, a twist of 50° or more can be 

 obtained which is sufficient to measure. 



In order to test first the relaxation in the copper wire alone, the inner 

 terminal was made of clock spring steel 0.0124 inches by 0.062 inches. 

 This was wound with 100 turns of 0.020 inch copper wire tensioned at 

 2.87 pounds (9,300 pounds per square inch). A twist of 25° was obtained 

 which is sufficiently large to measure. If one observed the angle after 

 transient creep has occurred, the angle decreased on the average about 

 17 per cent in the first month as shown by the circles of Fig. 22. The 

 values agree with the solid curve which was estabUshed by relaxation 

 measurements as a function of temperature as discussed in the next 

 paragraph. At room temperature, further decreases in the angle of about 

 10 per cent were observed out to times in the order of a year. 



If, however, the wrapped connection was heated up, a faster relaxa- 

 tion of the hoop stress occurred. Fig. 21 shows the ratio of angle meas- 

 ured to the initial angle as a function of time when the connection is 

 subjected to a temperature of 200°C. As shown by the dashed line, 

 which is a plot of the exponential equation 



R = e~"' where a = 2 X 10~^ 



(18) 



this is not a single relaxation of the type found for grain boundary 

 motion but is a sum of effects occurring -with different activation ener- 



1.1 



1.0 

 0.9 

 0.8 

 0.7 

 0.6 

 0.5 

 0.4 

 0.3 

 0.2 

 0.1 

 



> 2 468 2 468 2 468 2 



10 102 103 10^ 



TIME 'N SECONDS AT 200 DEGREES CENTIGRADE 



4 6 8 



105 



Fig. 21 — Ratio of angles of twist at time shown to initial angles. 



