430 



REPORT — 1887. 



Table V. — Wrought Iron subjected to Tension. 

 (Tons per Square Inch.) 



The next table relates also to bars strained by tension only, but it 

 indicates the effect of more varied treatment of the bar. It will be seen, 

 in the case of the first bar, that loading again immediately after stretching 

 to the yielding point, the elastic limit is lowered from ITS to 8"05 tons. 

 In the case of the second bar, similarly strained but with a period of rest 

 of 69 hours allowed, the elastic limit is raised from 12 to 20 tons. But 

 on reloading immediately the elastic limit is lowered to 4-05 tons. With 

 a three years' period of rest it is raised to 33 tons, just the load with 

 which it had previously been strained. But this artificially produced 

 elastic limit is so unstable that on hammering the bar on the end and 

 reloading it has fallen to 12-5 tons. 



Table VI. — BaiiscMnger's Exj>erinients on the Change of Position of the 



Elastic Limit. 

 (Bar subjected to Tensions only. Tons per Square Inch.) 



Treatment 



Bar of Bessemer Steel. No. 93!)c. — 



1. Original condition .... 



2. 1 day after 



3. Immediately after (2) . 



4. Immediately after (3) .... 



5. 1 day after (4). [Broke with 34 tons] 



Bar 939b. Same Steel— 



1. Original condition .... 



2. 69 hours after (1). 



3. h hour after (2). Straightened in the lathe 



4. 68 hours after (3) 



5. 3 years after (4) 



6. 2 days after, and after being vibrated by ham- 



mering on end 



7. After 2 years, and after heating to cherry red 



and cooling in water. [Broke at 35-8 tons.] 



Elastic 

 Limit 



11-6 

 8-05 



120 

 20-0 

 405 

 6-9 

 330 

 12-5 



Yielding 



Stress or 



Breaking 



down 



point 







17-4 

 24-8 

 27-0 

 28-3 

 32-4 



18-6 

 24-0 

 25-6 

 330 

 33-0 

 32-0 



24-6 



Greatest 

 Stress 



imposed 

 on Bar 



22-6 

 26-8 

 28-3 

 29-6 

 34-0 



21-3 

 26-6 

 32-3 

 33-0 

 330 

 320 



25-2 



