600 



THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1953 



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3 



Z6 



0.1 12 5 10 20 30 40 50 60 70 80 90 95 98 99 



PER CENT OF TERMINALS BELOW INDICATED STRIPPING FORCE 



Fig. 4 — Effect of relaxation on stripping force. 



99.9 



under vibration and handling it may break easily. A practical and gen- 

 erally easily met requirement is that the connection be capable of with- 

 standing unwrapping without wire breakage. 



OTHER TESTS 



A large amount of work has been done other than testing connections 

 in accordance with the foregoing requirements. These tests (See Table 

 II) include measurement of exposure to humidity, hydrogen sulphide 

 corrosion, heating by internal electrical losses, vibration, etc. Many of 

 these tests were made before any clear picture mechanism of deteriora- 

 tion of the connection was available so that they were not exposed to 

 temperature high enough to cause very much relaxation. Therefore, 

 there is no quantitative relation between these tests and the actual 

 aging of connections, but they do indicate a general ruggedness which 

 gives confidence in the reliability of the connections. 



In measuring the effect of relaxation, connections have been tested 

 in a preliminary way by subjecting them to sufficient heat sufficiently 

 long to relax the stresses appreciably more than would be expected in a 

 normal forty-year life. Upon unwrapping, the bright areas of contact 

 were still present. Fig. 4 shows the result of a typical relaxation test on 

 the stripping force. The rise in stripping force after relaxation is attrib- 

 uted to the solid state diffusion process described by Mr. Mason. 



I 



