REPORTS ON THE STATE OF SCIENCE.—1913. 
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Rotating cantilever tests in which mild steel appeared to have slightly 
greater endurance at 400° to 500° F. than at ordinary temperatures. J. E. 
Howard (No. 48) finds that the number of rotations for fracture was very 
much increased at temperatures of 400° F. to 600° F. This is partly a 
metallurgical question, as the condition of the steel previous to the warming 
may affect the result. Further, it is known that the elongation in tensile 
tests of the steels dealt with would be slightly improved at the temperatures 
named, which is broadly in agreement with these authors’ results. 
92 Unwin, W. C. General Considerations on Safe Working Limits of 
Stress. ‘Testing of Materials of Construction,’ Art. 
255, 1910 edition. 
93 Wohler, A. 1871 Ueber die Festigkeitsversuche mit Eisen und Stahl. 
See ‘Engineering,’ vol. II., or Unwin’s ‘ Testing 
of Materials.’ 
94 (Various writers) 1910 Enquéte sur la fatigue des Métaux. ‘La Technique 
Moderne,’ 1910, vol. 2, pp. 19-21, 83-84, 151-4, 
210-4, 280-4, 345-7. 
Discussion of these questions, proposed by the Editors :— 
1. Is it established that metals undergo, in time, fatigue which noticeably alters 
their endurance ? 
2. Are the circumstances of this known and can they be avoided ? 
3. Are there means of recognising the symptoms of this state, and hence avoiding 
disasters resulting from it ? 
4, What inferences can be drawn from the existence of these phenomena from 
the point of view of determining the safety of metallic machines and structures ? 
The replies received are generally of the utmost vagueness, or are quite platitudes 
to all concerned materially in the subject, or are of little practical bearing (e.g., most 
of Retjo’s theory). 
A. Mesnager quotes Le Chatelier (Internat. Congr. for Testing Materials, 1900, 
p. 90) that an alteration of the decrement would be produced by alteration of the 
material, and seems to suggest this as an indication of the progress of fatigue in a 
piece. [Evidently this would rarely be applicable.—F. R.] E 
P. Breuil refers to the fact that the vastly greater part of the work on the subject 
is British, both combined stress and alternating. Eighty per cent. of the failures 
are due to ignorance on the part of the designer (as to stress which will actually come 
upon the piece). It is not known whether any stress, however small, will produce a 
permanent deformation, or, if so, whether this deformation is localonly. The micro- 
scope is the best instrument at present available in this respect. It is necessary to 
do fatigue tests above the elastic limit, and desirable to register deformation at each 
alternation of the same stress, or to register each load necessary to give equal alter- 
nating deflections. Importance of hysteresis. Importance of annealing to restore 
from the effects of fatigue ; but this is not always practicable. 
F. Schule.—Microscope has not given a satisfactory answer to (2). 
Do.—Suggests electric conductivity should be tried as a test for progress of fatigue 
for (3). 
(This is of very little use.—F. R.) 
4, Suggests scrapping after a certain life; i.e. ‘ life’ factor of safety. 
A. Retjo.—Treats the subject mathematically, following Van der Waals and 
Amagat. 
L. Grenet.—It is not fully evident that annealing will restore fatigued material. 
(Of course not. Qualification is necessary. See comment below.—F. R.) 
In design, so far as possible, it should be endeavoured to calculate the shock 
absorbable ; in general, he recognises the importance of resilience ; he suggests par- 
ticularly tests of the safe limit of repeated shock, accompanied by the use of a large 
factor of safety. 
Cellerier and Breuil.—Report on a broken rail. Failure ascribed to fatigue of 
the intensely cold-worked (in service) surface layer. 
L. Guillet.—Troubles are usually due to bad treatment of metals. His answer to 
(3) and (4) is ‘ Prudence,’ 
