26 



Mi; .1. Ml IK ()N Till: KKCOVEKY OF IRON FROM OVERSTRAIN. 



at 50 C. Similarly, only |th of a unit (the distance between 4 and 5) measures the 

 recovery due to 17 hours at the normal temperature (about 13 C.), while -gths gives 

 the recovery due to a fiirther 15 minutes at 50 C. 



Diagram No. VIII. (Second Part). (Recovery at 60 C., &c.) 



U. *.A*. 



IT. 





Extensions - diminished <*s explained on page 13. 

 Sct*li:-lunit 



Curve No. 13. See first part of diagram. 



14. 20 minutes after No. 13. 



15. After 15 minutes at 60 C. 



16. 10 95 C. 



.. 17. specimen turned down. 



18. 20 minutes after No. 17. 



19. After 5 minutes at 60 C. 



Curve No. 20. After other 15 minutes at 



60 C. 

 ,, 21. After 16 hours at normal 



temperature. 



22. After 15 minutes at 60 C. 

 23. 10 95" C. 



Comparison of Curves Nos. 19, 20, 21, and 22, which illustrate the process of 

 recovery after the passage of the fourth yield-point, shows a similar large difference 

 between recovery at the ordinary temperature and that at 60 C. (140 Fahr. ). In this 

 case Curve No. 21 (obtained 16 hours after No. 20) shows that the material has 

 yi.-liled more, after its long rest, except for the higher loads. This apparent 

 weakening is, of course, not due to the resting, but to the fact that the re-applica- 

 :i<n <f the load, necessary to obtain the readings for Curve No. 20, has had the effect 



further overstraining the material to a slight extent. A curve obtained immedi- 

 ately after No. 20 would have fallen below that curve and also below Curve No. 21, 

 vhile reaching approximately the same top point as No. 20. It may here be 

 emarked that all the curves of this diagram have been obtained from first loadings 



