206 REPORTS ON THE STATE OF SCIENCE.—1913. 
45 Hopkinson, B., 1912 The Elastic Hysteresis of Steel. ‘Proc. Roy. Soc, 
and 
Nov. 21, 1912. 
Williams, Gen 
See Report, Appendix I. 
46 Howard, J. E. 1888 Watertown Arsenal Reports. 
1893 See Massachusetts Institute of Technology.’ 
“Quarterly Proceedings,’ 1899. 
47 Do. 1906 Alternate Stress Testing : and Heat Treatment of Steels. 
‘Engineering Record,’ Sept. 22, 1906. ‘Int. Assoc. 
Testing Materials Congress,’ 1906. ‘Sci. Abs.,’ 
1906, No. 1808. 
Rotating loaded bar tests, at 500 r.p.m. Material, steels 0-17 to 0:82 % 
carbon. No steels were found to endure 100 10°* rotations with greater 
stresses than +40,000 lb. per square inch (calculated); but below this 
stress some bars withstood 150 x 10° rotations. 
At 400° F. the endurance was rather greater than at ‘atmospheric ’ 
temperature. 
48 Howard, J. E. 1909 Resistance of Steels to Repeated Alternate Stresses. 
Paper read Intern. Assoc. Testing Materials, 1909. 
See also ‘Mech. Eng.,’ 24, Dec. 31, 1909. ‘Sci. 
Abs.,’ 1910, No. 218. 
Rotating bar tests. Bars, 1 inch diameter, loaded to give uniform 
bending moment over 4 inches. 
Speed, 500 r.p.m. 
Material, 6 grades of open-hearth steel, hot rolled for commercial pur- 
poses ; carbon content, 0-17 to 1-09 per cent. 
Since the existence of or the possibility of finding a ‘limiting range ’ 
stress in rotating bar tests has been questioned the following results are 
quoted :— 
0:55 per cent. C. Steals 
With +35,000 lb. square inch rupture occurred with 9x 10° 
rotations. 
With + 30,000 1b. square inch rupture did not occur with 76 x 10° 
rotations. 
0-82 per cent. C. Steel— 
With +45,000 Ib. square inch rupture occurred with 6-05 10° 
rotations. 
With + 40,000 lb. square inch rupture did not occur with 202 x 10° 
rotations. 
See also some results of Wohler, page 378 Unwin’s ‘ Testing of Mate- 
rials.’ Of the range of steels tested, the highest resistance was found for 
the 0-73 per cent. and 0-82 per cent. carbon. This agrees with Rosenhain’s 
statement (No. 66), also substantially with Nos. 23, 62, 82, 90, 93. Occa- 
sional annealing at intervals during a test did not increase the endurance. 
See section Heat Treatment in Report. 
The number of rotations necessary for fracture was much increased when 
the temperature of the test was 400° F. to 600° F., a result which differs 
apie from Unwin’s (No. 91), and also from the author’s own result in 
o. 47. 
49 Kapp, G. 1911 Alternating Stress Machine. ‘ Zeits. Vereines Deutscher 
Ing.,’ Aug. 26, 1911. 
The stresses are direct tension and compression, and are obtained by the 
pull of an electro-magnet excited by an alternating current. 
50 Lord Kelvin Article Elasticity, ‘ Ency. Brit.,’ vol. vii., 9th ed. 
51 Kommers, J. B. 1912 Repeated Stress Testing. Papers V. 44 and V. 48. 
“Intern. Assoc. for Testing Materials,’ 1912. “€ Bei, 
Abs.,’ A, 1912, 1794. 
Tests on a Landgraf-Turner machine. To and fro bending given by 
an oscillating die, the slot in the die being longer in the direction of the 
