Abstract
IN his Friday evening discourse delivered at the Royal Institution on March 2, on “Some Current Research Problems in Engineering”, Dr. H. J. Gough, superintendent of the Engineering Department of the National Physical Laboratory, described the main group of researches in progress in his department. As representative examples, researches on wind pressure on structures, impact forces between vehicles and the road and failure of metals in relation to crystalline structure were discussed and demonstrated. An in vestigation of the wind pressures acting on a shed, 100 ft. by 42 ft. by 33 ft., was described, air flow conditions being rendered visible by using a small wind tunnel and models of buildings in conjunction with an optical system employing the Schlieren method. An interesting feature of the investigation was the existence of dangerous suction effects tending to lift off roofs and suck out leeward walls. The importance in engineering service of the particularly dangerous and insidious type of failure known as ‘fatigue’ was discussed; the problem is also one of considerable scientific interest as it affords a convenient line of attack upon the general problem of the cohesion of matter. The use of large metallic single crystals has opened up a new field of study on both the practical and scientific aspects of fatigue. Fatigue in ductile metals is closely bound up with the effects of plastic distortion, or ‘slip’, upon the crystalline structure of these metals. The normal form of metals—consisting of crystals of varying orientations each composed of definite arrangements of atoms—was briefly de scribed and the general and particular mechanisms of slip were demonstrated, employing lattice and other models. The effect of slip upon the actual crystalline structure, as deduced from X-ray data, was discussed, reference being made to ‘crystal break-up’ and lattice distortion, in relation to hardening. A tentative explanation of the cause and location of the initiation of fatigue cracks was described.
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Research in Engineering. Nature 133, 354 (1934). https://doi.org/10.1038/133354c0
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DOI: https://doi.org/10.1038/133354c0