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Evaluation of residual stress
274
BOOK REVIEWS.
IJ. F. 1.
tabulated only for air in Gas Tables. Correlation of existing data and some measurements to obtain new data are in progress for other gases; and as the results of this work become available they will be incorporated into Gas Tables, according to Professors Keenan and Kaye. Other additional data included in Gas Tables are the properties of combustion products of hydrocarbons and of the constituent gases. All values of thermodynamic properties in Gas "Fables are based on the examination of data from spectroscopic sources which were published in 1945 by F. D. Rossini and his coworkers at the National Bureau of Standards. The base temperature, for which enthalpy is zero, is not the same in Gas "Fables as in Thermodynamic Properties of Air. I t is taken to be zero on the absohlte Fahrenheit scale in accordance with Rossini's d a t a . Negative values of properties are thereby avoided. The molal unit is employed for all tables of thermodynamic properties except air, and as compared with the mass unit, the molal unit makes the range of values between tables very much smaller. I t also permits the use of a single table for the prodncts of combustion corresponding to a wide range of carbon-hydrogen ratios, provided only that the "percentage of theoretical air" is held fixed. Certain other interpretations of the same table in terms of mixtures of air and fuel vapor and of air and w a t e r vapor are also valid to good precision. For engineering application to the design of power apparatus, the precision of Gas "Fables is of the same order as that of modern steam tables, but the convenience is of a higher order. Sources and methods, and examples in application of the tables are included. MAX W. BER6. PnOTO6RAPHIC EMULSmN TECHNIQUE, by T . Thorne Baker. Second edition, ,:f36 pages, 14 X 20 cm., tables, drawings, and illustrations. Boston, American Photographic Publishing .Co., 1948. Price, $7.50. This new edition of the author's earlier work generally follows the same pattern as the first edition in format and chapter headings, with a few changes in subtitles and two new chapter headings, one on three-layer color films, and one on testing emulsioned products. Throughout the book the a u t h o r has revised the text to bring it up-to-date with the best information about emulsions which the manufacturers will divulge. In his introduction he points out that for years there were many closely guarded secrets in the manufacture of photographic emulsions, and that the only way to learn emulsionmaking formulas and technique, until fairly recently, was to be associated in the a c t u a l manufacture of films, which has been the author's experience for thirty years. Beginning about 1923, with the disclosure by Dr. S. E. Shephard, of the sensitizing effect of allyl isothiocyanate, more and more "secrets" were disclosed. (An apochryphal story has it that a buyer of hides for one of the large film companies knew this empirically for many years and always purchased hides from steers slaughtered in the spring when wild mustard was in bloom. Hides from these animals contained allyl mustard oil or allyl thiocyanate, and emulsions made with gelatine derived from these hides were faster than emulsions made with gelatine derived from other sources.) Following Shephard's disclosure, articles were published in many scientific journals by the scientists engaged in research on the subject of emulsions. Mr. B a k e r has gathered together in one volume the theories and also the practical formulas and technique of making emulsions in small batches for experimental purposes in the belief that there are certain phases of research which require emulsions different from the regular runs which manufacturers turn out for the trade, and that the only way a research laboratory can get them is to make them. Chapter references are included in a table at the end of the book as well as a n a u t h o r index and a subject index. GLADYS M 0LLER. EVALUATION OF RESIDUAL STRESS, by K. Heindlhofer. 196 pages, 14 X 21 cm., drawings, tables and illustrations. New York, McGraw-Hill Book Co., Inc., 1948. Price, $4.00. The evaluation of the intensity and distribution of residual stress in metallic structures is of extreme interest to manufacturers, engineers, and metallurgists. But there has been little
March, 1949.]
275
BOOK REVIEWS.
written in book form on the nature, detection, measurement and analysis of residual stress. Now in a comprehensive treatment of this ever increasingly important subject, the well qualified author has written a s h o r t but relatively detailed and practical book which can serve as a text for graduate students in mechanical engineering and metallurgy, and at the same time it can be used as a reference by the practicing engineer who is confronted by certain stress problems. Residual stress is that stress which would exist in an elastic solid body if all the external load, acceleration, and gravitation were removed. Fabricators meet with examples of the effects of residual stress as daily occurrences, since they may be induced in, the conrse of the manufacturing process, in castings, welds, and the roiling and joining of metal sheets. Once present, residual stress manifests itself in mechanical a n d / o r chemical effects, such as warping or cracking of quenched high-carbon steel articles, changes in dimensions during machining, and grain-boundary corrosion which may result in loss of cohesion at the boundaries, resulting finally in complete rupture. In some cases, residual stress may be turned into an asset, but to do so requires a basic knowledge of stress and strain relationships, and a good acquaintanceship with the various means for the detection and measurement of residual stress. This book attempts to clarify these points. A first expository chapter is concerned with the nature and significance of residual stress, laying down the mechanical sources of this stress with an explanation of possible consequences when residual stress is present. The nature of metal itself, as a crystal, with its anisotropic properties, is next considered, as are the effects on stress analysis of non-homogeneity and crystalline metal texture. Having thus introduced the subject, the pertinent phases of displacement, starting with the derivation of certain basic formulas restricted to homogeneous strain, a quantitative treatment of strain and stress and their interrelation, shear and various s h e a r diagrams are considered. The case of stress in the vicinity of a point, based upon geometrical relationships, is studied as well as the relation of strain to stress for an isotropic body, which is based on experiments pertaining to the elastic behavior of certain materials such as metals. The impossibility of calculating stresses within a self-stressed body from observations restricted to the surface measurement of strains is discussed. Two chapters are devoted to the various methods of observation and the necessary instruments and circuits. Sectioning, machining, etching, and stress relief are discussed, especially in their relation to means of measurement by usable gauges which are based upon the following physical effects: elastic change in spacing between atomic planes, change in macroscopic spacing, or the change in electric resistance caused by elastic strain in a wire. In this book fundamental ideas of stress and strain, internal and external, are fully explained from the viewpoint of the physicist and metallurgist. I t should be of great interest to the other branches of engineering as a reference guide in this field. S. C I-IARP.
PRINCIPLES OF RADAR, by Denis Taylor and C. H. Westcott. 141 pages, 15 X 22 cm., plates,, drawings and tables. New York, The Macmillan Co.; Cambridge, The University Press; 1948. Price, $3.50. This book is one of a new British series called "Modern Radio Technique" which deals with the advances in radio technique made during the war. I t is intended as an exposition and survey of the principles underlying radar design. The authors predicate the book with a hope that " i t will be of service to readers who have found the sudden release of so much detailed information to lead to mental indigestion, by indicating common factors which underlie the many types of radar equipment which have been developed and used during the war." Dr. Taylor is a Superintendent at the Telecommunications Research Establishment of The Ministry of Supply, and Dr. Westcott is now with the Physics Department at Birmingham University. T o those engineers, physicists, and mathematicians who have been associated with radar techniques during the war years, this book will be attractive because of its clear presentation
BOOK REVIEWS.
IJ. F. 1.
tabulated only for air in Gas Tables. Correlation of existing data and some measurements to obtain new data are in progress for other gases; and as the results of this work become available they will be incorporated into Gas Tables, according to Professors Keenan and Kaye. Other additional data included in Gas Tables are the properties of combustion products of hydrocarbons and of the constituent gases. All values of thermodynamic properties in Gas "Fables are based on the examination of data from spectroscopic sources which were published in 1945 by F. D. Rossini and his coworkers at the National Bureau of Standards. The base temperature, for which enthalpy is zero, is not the same in Gas "Fables as in Thermodynamic Properties of Air. I t is taken to be zero on the absohlte Fahrenheit scale in accordance with Rossini's d a t a . Negative values of properties are thereby avoided. The molal unit is employed for all tables of thermodynamic properties except air, and as compared with the mass unit, the molal unit makes the range of values between tables very much smaller. I t also permits the use of a single table for the prodncts of combustion corresponding to a wide range of carbon-hydrogen ratios, provided only that the "percentage of theoretical air" is held fixed. Certain other interpretations of the same table in terms of mixtures of air and fuel vapor and of air and w a t e r vapor are also valid to good precision. For engineering application to the design of power apparatus, the precision of Gas "Fables is of the same order as that of modern steam tables, but the convenience is of a higher order. Sources and methods, and examples in application of the tables are included. MAX W. BER6. PnOTO6RAPHIC EMULSmN TECHNIQUE, by T . Thorne Baker. Second edition, ,:f36 pages, 14 X 20 cm., tables, drawings, and illustrations. Boston, American Photographic Publishing .Co., 1948. Price, $7.50. This new edition of the author's earlier work generally follows the same pattern as the first edition in format and chapter headings, with a few changes in subtitles and two new chapter headings, one on three-layer color films, and one on testing emulsioned products. Throughout the book the a u t h o r has revised the text to bring it up-to-date with the best information about emulsions which the manufacturers will divulge. In his introduction he points out that for years there were many closely guarded secrets in the manufacture of photographic emulsions, and that the only way to learn emulsionmaking formulas and technique, until fairly recently, was to be associated in the a c t u a l manufacture of films, which has been the author's experience for thirty years. Beginning about 1923, with the disclosure by Dr. S. E. Shephard, of the sensitizing effect of allyl isothiocyanate, more and more "secrets" were disclosed. (An apochryphal story has it that a buyer of hides for one of the large film companies knew this empirically for many years and always purchased hides from steers slaughtered in the spring when wild mustard was in bloom. Hides from these animals contained allyl mustard oil or allyl thiocyanate, and emulsions made with gelatine derived from these hides were faster than emulsions made with gelatine derived from other sources.) Following Shephard's disclosure, articles were published in many scientific journals by the scientists engaged in research on the subject of emulsions. Mr. B a k e r has gathered together in one volume the theories and also the practical formulas and technique of making emulsions in small batches for experimental purposes in the belief that there are certain phases of research which require emulsions different from the regular runs which manufacturers turn out for the trade, and that the only way a research laboratory can get them is to make them. Chapter references are included in a table at the end of the book as well as a n a u t h o r index and a subject index. GLADYS M 0LLER. EVALUATION OF RESIDUAL STRESS, by K. Heindlhofer. 196 pages, 14 X 21 cm., drawings, tables and illustrations. New York, McGraw-Hill Book Co., Inc., 1948. Price, $4.00. The evaluation of the intensity and distribution of residual stress in metallic structures is of extreme interest to manufacturers, engineers, and metallurgists. But there has been little
March, 1949.]
275
BOOK REVIEWS.
written in book form on the nature, detection, measurement and analysis of residual stress. Now in a comprehensive treatment of this ever increasingly important subject, the well qualified author has written a s h o r t but relatively detailed and practical book which can serve as a text for graduate students in mechanical engineering and metallurgy, and at the same time it can be used as a reference by the practicing engineer who is confronted by certain stress problems. Residual stress is that stress which would exist in an elastic solid body if all the external load, acceleration, and gravitation were removed. Fabricators meet with examples of the effects of residual stress as daily occurrences, since they may be induced in, the conrse of the manufacturing process, in castings, welds, and the roiling and joining of metal sheets. Once present, residual stress manifests itself in mechanical a n d / o r chemical effects, such as warping or cracking of quenched high-carbon steel articles, changes in dimensions during machining, and grain-boundary corrosion which may result in loss of cohesion at the boundaries, resulting finally in complete rupture. In some cases, residual stress may be turned into an asset, but to do so requires a basic knowledge of stress and strain relationships, and a good acquaintanceship with the various means for the detection and measurement of residual stress. This book attempts to clarify these points. A first expository chapter is concerned with the nature and significance of residual stress, laying down the mechanical sources of this stress with an explanation of possible consequences when residual stress is present. The nature of metal itself, as a crystal, with its anisotropic properties, is next considered, as are the effects on stress analysis of non-homogeneity and crystalline metal texture. Having thus introduced the subject, the pertinent phases of displacement, starting with the derivation of certain basic formulas restricted to homogeneous strain, a quantitative treatment of strain and stress and their interrelation, shear and various s h e a r diagrams are considered. The case of stress in the vicinity of a point, based upon geometrical relationships, is studied as well as the relation of strain to stress for an isotropic body, which is based on experiments pertaining to the elastic behavior of certain materials such as metals. The impossibility of calculating stresses within a self-stressed body from observations restricted to the surface measurement of strains is discussed. Two chapters are devoted to the various methods of observation and the necessary instruments and circuits. Sectioning, machining, etching, and stress relief are discussed, especially in their relation to means of measurement by usable gauges which are based upon the following physical effects: elastic change in spacing between atomic planes, change in macroscopic spacing, or the change in electric resistance caused by elastic strain in a wire. In this book fundamental ideas of stress and strain, internal and external, are fully explained from the viewpoint of the physicist and metallurgist. I t should be of great interest to the other branches of engineering as a reference guide in this field. S. C I-IARP.
PRINCIPLES OF RADAR, by Denis Taylor and C. H. Westcott. 141 pages, 15 X 22 cm., plates,, drawings and tables. New York, The Macmillan Co.; Cambridge, The University Press; 1948. Price, $3.50. This book is one of a new British series called "Modern Radio Technique" which deals with the advances in radio technique made during the war. I t is intended as an exposition and survey of the principles underlying radar design. The authors predicate the book with a hope that " i t will be of service to readers who have found the sudden release of so much detailed information to lead to mental indigestion, by indicating common factors which underlie the many types of radar equipment which have been developed and used during the war." Dr. Taylor is a Superintendent at the Telecommunications Research Establishment of The Ministry of Supply, and Dr. Westcott is now with the Physics Department at Birmingham University. T o those engineers, physicists, and mathematicians who have been associated with radar techniques during the war years, this book will be attractive because of its clear presentation