October, 1944 AIRCRAFT ENGINEERIN G 297 Experimental Stress Analysis. (Proceed shown in its potentialities when it was proving Such a metal mould is termed a die, and the so valuable in the hands of its originators. process of casting is known as die casting. ing s of the Society for Experimental Apart from the advantage that a large number Stres s Analysis.) [Addison-Wcsley Press, Of the twenty papers that make up the of castings may be produced therefrom, it is Inc . $3.00.] present symposium fourteen deal with the evident that the hole or cavity in a metal die "Electrical Resistance Strain Gauge" method of This book is a collection of papers read before stress analysis, tw o with th e photoelastic method can be made more accurately than is possible in the newly-formed American "Society for Ex and three with the use of brittle lacquers. a sand mould and may be of more intricate perimental Stress Analysis" a t its first meeting Among the stress problems attacked by the form. Consequently, the castings produced are in May, 1943, which was held at Detroit. These Resistance Strain Gauge method may be men more accurate, while their smooth surfaces papers constituted at the same time the final tioned the measurement of dynamic stresses in require little subsequent finishing treatment. Such a die mus t be mad e in two or more separate transactions of the Eastern Photoelasticity th e hull of a ship a t launching an d in th e rudder part s to permit of machining out a cavity of Conference at its seventeenth semi-annual during sea trials; the measurement of stress in th e required form and of removing the finished meeting and Experimental Stress Symposium, internal combustion engine connecting rods, casting therefrom. When the different parts are fhe new society covers a wider field tha n the old pistons, cylinder flanges and studs; in volute in tha t it seeks to foster interest not only in assembled together, the cavity conforms to the springs and rotating airscrews; and the analysis photoclastic methods but in all other modern shape and dimensions of the required casting of .residual stresses in heat-treated solid bars. methods of experimental stress analysis, chief with a suitable allowance for shrinkage. There The papers contain not only the results ob of which perhaps is the "Electrical Resistance is also an opening connecting the cavity with tained from these investigations but also valu th e exterior of the die through which the Strain Gauge" method. able descriptions of the techniques used in molten metal is introduced. The metal is poured each case. There is no doubt that they do this sort of into the opening from a ladle and allowed to A very interesting paper is one on "An thing much better in America tha n here in this flow into th e cavity under the action of gravity, country, and we might well tak e a leaf out of the adjunct to th e Strain Rosette". A strai n rosette, thi s method being termed "Gravity Die American book. It is not so much that people b y th e way, is a combination of three resistance Casting". 'in thi s country are less ready to share the fruit strai n gauges placed as close together as of any experience gained in the use of new possible to measure the stresses at a given There is very little literature available on methods as tha t the enterprise necessary to the 'point ' in three different directions, the data thi s subject. Therefore, the present booklet :ffective pooling of experience is somehow thu s obtained being used to deduce the direc covering the whole process, as it does, in a lacking. Here, apart from articles in the tech tion and magnitude of the principal stresses at comprehensive manner, should appeal not only th e point. The computational work involved in nical press or isolated papers read before the t o the designer and production engineer, but th e analysis of a large number of rosettes is a existing learned societies, the only way to also t o students and those interested in casting learn abou t th e uses an d pitfalls of a new method long and tedious business, and the adjunct on an economic basis. is t o visit a firm or institutio n where th e method alluded to in the title is a mechanical device for The author has treate'd his subject in a is known to be employed. The snag in this pro obtaining the principal stresses directly from straightforward manner. In one respect, the cedure is that only certain aspects of the new th e three recorded stresses. Three other papers title of his work may be misleading since the method are likely to be gleaned from such in the form of discussions of the paper just subject-matter is rather more general than the visits so that a comprehensive view of the mentioned are included and five alternative title suggests; the book actually refers, in methods of reducing th e computational work. advantages and disabilities of the method is particular, to similar processes such as Pressure nard t o obtain. Die Castings, which are often confused with Another interesting paper is tha t by a mem Gravity Die Casting and which are produced In America, on the other hand, they do not ber of the staff of Messrs. Baldwin, Southwark, b y the application of pressure to the molten hesitate to form a new society for promul makers of probably the most reliable type of metal in order to force it into th e die in which it gating and popularizing the new methods. The resistance strain gauge on the market. The solidifies. effectiveness with which this is done is well autho r traces th e history of th e resistance strain gauge and gives a valuable description of the exemplified by th e first meeting of the "Society A considerable amount of information re capacities and fields of usefulness of the for Experimental Stress Analysis" in which lating to the costs of gravity die casting com 'tyenty papers were read on various aspects of present-day commercially available gauges. pared with companion methods should be of the new methods of experimental stress investi The papers relating to the use of brittle great assistance, even to the experienced man. gation. A record of these papers in book form is The major portion of the booklet is especially lacquers describe experiments in which this i very useful thing to have both for immediate valuable to draughtsmen, toolmakers, and method was successfully used in the quantita reading and future reference, but its value others responsible for the tooling of dies as it tive determination of stresses and emphasize the cannot compare with the usefulness of actual deals with the technique of gravity die casting potentialities of this method when stresses have attendance at the meeting, when the hundred t o be measured at inaccessible spots and when and the design of moulds. Useful instructions and one questions tha t arise in the mind of the th e stress picture is expected to be complicated. are given for drawing the various details and reader could have been sifted and settled on the th e thoughts reflecting on design are explained The book is well produced and the many spot. b y numerous examples. A noteworthy feature diagrams and photographs are commendably of th e booklet is th e inclusion of a brief descrip One great advantage of disseminating in- clear. tion of original casting developments and, in the Formation in this American way is tha t the risk D.W . final chapter, of detailed data of preparing the of losing hard-won new techniques by th e death Gravit y Die Casting Technique. By George die for the foundry. of their originators is greatly reduced. Much W. Lowe. [Hutchinson. 9s. 6d.] reduced also is the chance of a powerful tool Throughout, the text is simple to understand being littl e exploited after the hand tha t forged Where a number of identical parts are to be and very fully illustrated by good reproductions it has ceased to wield it. There is little doubt cast, much time and expense are saved if the of photographs and line drawings. The booklet, that the method of photoelasticity developed same mould can be used over and over again. in fact, provides a very adequate general survey by the late Professors Coker and Filon in this This is quite practicable when the moulds are of gravity die casting, and -as such can be country would be to-day a much more familiar made of iron or steel, provided that the melting considered of importance. tool to engineers had greater interest been points of the alloys to be cast are not too high. A. J . S.
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Oct 1, 1944