122 



Mr. W. A. Scoble on Ductile 



The results are collected 



cut from the same length of tube 

 below. 



Table B.— Tests of Solid Drawn Steel Tubes. 

 Internal diameter 0*818 in. External diameter 0*885 in. 



The maximum stress has 25,600 and 77,000 lbs./s. inch 

 for its extreme values, and the stress difference varies 

 from 51,200 to 77,800 lbs./s. in. The bending and twisting 

 moments are plotted in fig. 2, in which the numbers of the 

 tests are shown against the points. The letter refers to the 

 tube, and the number indicates the order in which the test 

 was made on that specimen. 



The figure is interesting because it shows very clearly the 

 effect of repeated loading. An ellipse is drawn to lie evenly 

 between the points. Specimens cut from the same length of 

 material are not exactly alike, and an error is possible in 

 locating the yield-point ; but alter allowance is made for 

 these facts, it is evident that the yield-point was raised by a 

 previous test. Nevertheless, the results clearly indicate that 

 the maximum shear stress is more nearly constant than the 

 principal stress, and that the bending moment is again greater 

 than the torque, so that the shearing stress and the stress 

 difference increase with the bendino- moment. 



Test. 



Bending 

 Moment, 



Twisting 

 Moment. 



Tensile 

 Stress 

 due to 



Shear 

 Stress 

 due to 



Maximum 

 Principal 



Minimum 

 Principal 



Stress j 

 Difference j 

 = 2ce 





lbs. ins. 



lbs. ins. 



Bending, 

 lbs./s. in. 



Torque, 

 lbs./s. in. 



Stress, 

 lbs./s. in. 



Stress. 

 lbs./s. in. 



Maximum 



Shear 



Stress. 



Bl 







940 







25600 



25600 



-25600 



51200 



E2 







1030 







28050 



28050 



-28050 



56100 , 



E3 



300 



1090 



16330 



29700 



38970 



-22630 



61600 ( 



E4 



600 



970 



32700 



26400 



47400 



-14700 



62100 



Dl 



800 



(300 



43550 



16330 



48980 



- 5420 



54400 | 



CI 



810 



700 



44100 



19100 



51250 



- 7150 



58400 



B2 



1100 



400 



59900 



10900 



61770 



- 1870 



63640 



B4 



1120 



800 



61000 



21800 



68000 



- 7000 



75000 



Al 



1250 







68100 







68100 







68100 



A2 



1330 







72400 







72400 







72400 



B3 



1400 







76200 







76200 







76200 



B5 



1400 



300 



76200 



8165 



77000 



- 800 



77800 



The Tests on Copper Tubes. 



Tests were also made on solid drawn copper tubes, of 

 0*79 inch internal and 0*881 inch external diameter. The 

 specimens were given a set to correct for their defective 



