588 



BELL SYSTEM TECHNICAL JOURNAL 



The improvement in the endurance Hmit due to cold rolling brass, 

 nickel silver and phosphor bronze is not consistent with the increase 

 in tensile strength produced by the same means. This is shown by 

 Table II where in practically every instance material hardened by 

 cold work shows a progressive decrease in the ratio of endurance 

 limit to tensile strength. 



15 

 ENDURANCE 



LIMIT - PS! X 10^ 



Fig. 12 — Relation of Ultimate Tensile Strength to Endurance Limit, No. 24 

 B. & S. Gauge, Non-Ferrous Sheet. 



Previous investigators have shown a close correlation between 

 endurance limit and tensile strength for iron and steel. Fig. 12 fails 

 to reveal such a general correlation for the sheet metals under test. 

 For a particular alloy, however, there appears to be a progressive 

 increase in endurance limit with increase in tensile strength due to 

 cold work but the slope of the curves shown are widely different for 

 the various alloys. 



