40 
41 
42 
43 
COMPLEX STRESS DISTRIBUTIONS IN ENGINEERING MATERIALS. 205 
The machines are on the principle of Stanton and Bairstow’s alternating- 
shock bending machine (No. 78). 
Notched specimens are used; the number of blows is 80 per minute. 
The machines are arranged to give, if desired, + of a turn to the specimen 
after each blow. No results are given. 
Haigh, B. P. 1912 Alternating Load Tests. ‘ British Association,’ 1912- 
‘ Engineering,’ Nov. 29, 1912. ‘Sci. Abs.,’ 1912, 
No. 1612. 
A description of the author’s machine for testing wire in repeated ten 
sion. A few preliminary experiments only are recorded, the cycles having a 
frequency of 60 per second, and the stresses varying between 0 and a tensile 
maximum. 
Hancock, E. L. 1906 ‘Tests of Metals in Reverse Torsion. ‘ Phil. Mag.,’ 12, 
pp. 426-30. ‘Sci. Abs.,’ A, 1906, 1810. 
This paper is concerned with alterations of elastic limits by torsional over- 
strain in alternate directions of twist, the latter being slowly applied. 
Haughton, S. A. 1905 Failure of an Iron Plate through Fatigue. ‘Sci. Abs.,’ 
A, 1905, 1846. 
Failure of a barrel plate of a boiler. The plate had been exposed to 
severe ‘ panting’ stresses. 
Hopkinson, B. 1912 A High-speed Fatigue Tester and the Endurance of 
Metals under Alternating Stress of High Frequency. 
‘ Proc. Roy. Soc.,’ A, 86, Jan. 31, 1912. ‘Sci. Abs.,’ 
1912, No. 628. 
Description of the Hopkinson high-speed machine and of the checks on 
the calculated stresses. A variety of results given for speeds of 7,000 cycles 
er minute. It is conclusively shown that there is a very marked speed 
effect, both the number of cycles and the time required for producing fracture 
being greater than with machines at one or two thousand cycles per minute. 
Table of Limiting Ranges of Stress, with Three Machines of Different Type for 
same Material. 
| Stanton’s Direct- | Wohler Rotating-bar Hopkinson’s 
Material stress Machine. Machine, N.P.L. Machine. 
1,100 per minute 2,200 per minute 7,000 per minute 
tons per squareinch | tons per square inch tons per square inch 
Cc | 25 —_— +32 
Ds +26-5 +31-5 
+24 
It is inferred that ‘ recovery of elasticity ’ is not an important factor in 
tests with equal + alternations at high speeds, though at low speeds ‘ re- 
covery ’ may be sufficient to mark the speed effect. 
It is pointed out that it is not proved that the limiting range is higher, 
but that the apparent resistance to fatigue (in time and in number of cycles) 
is increased. The speed effect is shown to be the reverse of that found by 
Reynolds and Smith, No. 59. 
Nos. 23, 65, 80, 82 and 84 show that speed effect is apparently negligible 
at speeds between 60 and about 2,400 cycles per minute. 
44 Hopkinson, B., 1905 Elastic Properties of Steel at High Temperatures. 
and F. Rogers “Proc. Roy. Soc.,’ A, 76, 1905. 
Tensile tests of iron and steel, using an extensometer, at temperatures 
up to 900° C. Tests not carried to fracture. 
The elastic time effect (7.e., that strain which occurs with lapse of time 
under a constant load, and which disappears with lapse of time upon removal 
of the load, as distinguished from hysteresis, which is independent of time) 
probably increases with temperature, since it was found to be very great 
at high temperatures. 
