MR. .T. MUIR ON THE RECOVERY OF IRON FROM OVERSTRAIN. 



35 



of the yield-point was also shown in Diagram No. VIIL, the material being slightly 

 different from that which has just been considered; and, further, it will be shown in 

 Diagram No. XL, whicli gives the history of a specimen of unhomogeneous wrought 

 iron. The distance between the yield-points is 3 to 3^ tons with the common 

 wrought iron and 5 or 6 tons with the semi-mild steel usually employed in these 



Diagram No. XI. (Common iron.) 



tons/in* 

 SO 



. 



Extensions- diminished as explained on page 

 Scale - 1 unit* of AH inch. 1. 



Curve No. 1 . Primary test. 



2. Immediately after No. 1 . 



ii * ii ii it 



4>> 

 ii it ii * 



5. 16 hours after No. 4. 



5'. After a few minutes at 100 C. 



6. Immediately after No. 5. 



Curve No. 7. Immdiatcly after No. 6. 

 lf 8. After a few minutes at 100* C. 

 9. Immediately after No. 8. 

 10. J hour after No. 9. 

 11. After 5 minutes at 55 C. 

 12.- 10 , 100 C. 



experiments. In Diagram No. VIIL yield-points were obtained at loads of about 

 27, 33, 38, 43^, and 49J tons per square inch, fracture occurring at the last 

 mentioned stress. With another specimen from the same steel rod the primary 

 loading was carried to 30 tons per square inch, and after recovery of elasticity a 

 2nd yield-point was obtained at about 35 tons per square inch. On again restoring 

 elasticity a 3rd yield-point was found to occur at a stress somewhat under 40 tons, 



F 2 



