Transactions - North East Coast Institution of Engineers and Shipbuilders Volume 3 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1887 Excerpt: ...some recovery from the apparently permanently bent condition would take place in the course of time. The suggestion, therefore, was that the low set referred to in the bridge links might be only a temporary and not a permanent set, but it might nevertheless be an indication of a limit of strain which, if sufficiently often repeated, might induce disintegration of the material; as the fact that friction between the particles was obviously indicated by a temporary set, showed that there must be some actual dislocation of the particles, as distinguished from the mere modification of their form, which we could imagine to be the condition in a perfectly elastic body. The speaker considered this to be the process of failure from fatigue in machinery, which had been supposed from estimates formed upon known data, to be amply strong enough. At the same time the practical permanency of a great deal of machinery, under severe shock and strain tending to produce distortion, went to show that there was some limit within which practical permanency could be calculated upon. His protest against hollow shafting was founded more upon dynamic considerations and the result of pretty wide experience than upon any calculation. No one could for a moment doubt the increased static strength of the hollow form, and he did not suppose that any of them would for a moment cavil at the use of hollow shafts, as steel-makers hare to make them, to obtain sufficient rigidity within moderate weights to enable the shipowner to avoid numerous external brackets in twin screwships, in lengths sometimes exceeding 70 feet; but in the case of the internal machinery generally of a ship he should have considered that the object should be to give the greatest possible capability for elastic flexure f...