. Cassier's magazine . FIG. 8. DR. J. H. SMITHS MACHINE F is the specimen. C D, guides. B, arm. W, weights. E G, fixed masses. H, spring. the specimen used is a ring in form. Mr. E. M. Eden has obtained someinteresting results with a machine ofthe rotating beam type (Fig. 9), inwhich the specimen is subjected tobending and to sheer. Critics ratherobjected to the Wohler tests (bend-ing) because of the complications in-troduced by the shear stress. The author has devised an alternat-ing torsion testing machine. The principle upon which it works maybe illustrated as follows: Imagine ashaft which
. Cassier's magazine . FIG. 8. DR. J. H. SMITHS MACHINE F is the specimen. C D, guides. B, arm. W, weights. E G, fixed masses. H, spring. the specimen used is a ring in form. Mr. E. M. Eden has obtained someinteresting results with a machine ofthe rotating beam type (Fig. 9), inwhich the specimen is subjected tobending and to sheer. Critics ratherobjected to the Wohler tests (bend-ing) because of the complications in-troduced by the shear stress. The author has devised an alternat-ing torsion testing machine. The principle upon which it works maybe illustrated as follows: Imagine ashaft which is made to oscillate andwhich carries a flywheel. Then theforces necessary to start and to stopthis weight may be easily calculated,and so the stress on the shaft may beobtained. The apparatus is still inthe course of solution, although somevery successful runs have been madein the course of its development. ALTERNATING STRESS TESTING 429. FIG. 9. MR. EDENS MACHINE W, a weight. C D, supports. A B, bearings. Pure bending, no shear, obtained betwen A and B. THE NUMBER OF REVERSALS So far, then, we may say thatmany investigators have entered thisfield of research. The practical manwill at once say: What has been theresult? It has been shown, beyonddispute, that the number of alterna-tions to which a specimen is sub-jected undoubtedly affects its in itself is a great is still more to be learned. Thegreat point at issue now is whetherthe rate at which the alternations aremade has any effect. Dr. Stanton ad-heres to the opinion that it does notmake any difference whether thespecimens in these machines—or anymaterials in machines or structures—are subjected to alternating stresswhich varies slowly or rapidly. , Professor Morley and others are opposed to this opinion. Thenext great step in advance will be thesettlement of this debatable can only be achieved by definiteevidence
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