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Impact strength of materials
Book
Reviews
IMPACT STRENGTH OF MATERIALS, by W. Johnson. 361 pages, diagrams, illustr., 6 x 9 in. London, Edward Arnold, 1972. Price, E12.00 (approx. $30). Recent years have witnessed a relatively important renaissance in research on impact and stress wave effects in solids. Int’erest stems from sources as diverse as high speed metal forming, micro-meteorite cratering, vehicular crashworthiness and energy absorbers. However, instruction in the most basic notions of impact and stress waves have generally been absent from most undergraduate engineering curricula, the lack of an introductory text being a primary reason. This is the expressed motivation for the development of Impact Strength of Materials. In contrast with other monographs on the subject, a technological approach is employed, i.e., in the spirit of strength of materials as opposed to continuum mechanics. The aim is for material that can be used by a large number of students and practicing engineers. This objective is achieved with the presentations of elastic wave theory, applications of elastic stress waves and plasticity theory. The chapters on dynamic loading of beams, rings, frames and plates are somewhat specialized and reflect the author’s background in large plastic deformation and high velocity metal forming as opposed to a traditional structural engineering approach. For example, only plastic response of such structural components to impact loads is considered. A variety of “semi-infinite media” problems are discussed as well, e.g., indentation byprojectiles, jet penetration, water cannons, hypervelocity impact, camouflet and earth shifting problems. The text is presented in a stimulating style with excellent illustrations and 72 fascinating plates. It should certainly have a catalytic effect on instruction and also research on impact phenomena in solids for quite some time. EDWARD G. LOVELL Engineering Mechanics Department University of Wisconsin Madison, Wisconsin
DIGITAL FILTERS, by M. H. Ackroyd. 82 pages, diagrams, 6 x 9 in. London, Butterworths, 1973. Price, ~21.85 (approx. $7.50); Butterworths, Toronto, Canada.
In t.his book, which is part of the ‘Computers in Medicine” series, Dr. Ackroyd concisely and clearly introduces a newcomer to Digital Filters and although the applications have naturally been taken from medical problems, anyone working in a different field should not be deterred as the contents are applicable to such filters used in any area of signal processing. The introductory chapter sets a perspective for digital filters by explaining what they are, why and how they are used and what advantages they have over analogue circuits. It then proceeds to cover the essentials of sampling by briefly explaining analogue-to-digital conversion, Z-transforms, transfer functions, poles and zeros, and the concept of a frequency response, and finally includes a discussion of how t’o program digital filters from a block diagram approach. Then the design of recursive and nonrecursive filters is considered. The author quickly discusses the properties of each type, reviews the approaches available and concentrates on a specific technique: Butterworth and Chebyshev design for recursive and windowing for non-recursive filters. As continual reference is made to the FORTRAN subroutines listed in the Appendix, a newcomer is immediately able to try his hand at designing filters and thus get a feel for the subject. For someone who needs to use other methods, Dr. Ackroyd includes a useful set of References and a comprehensive Bibliography. Finally, a chapter deals with applications such as noise reduction, signal analysis and equilization, and again there is constant reference to practical points, perhaps it is this that makes the book so readable. L. G. CUTHBERT Queen Mary College University of London, London
297 15
Reviews
IMPACT STRENGTH OF MATERIALS, by W. Johnson. 361 pages, diagrams, illustr., 6 x 9 in. London, Edward Arnold, 1972. Price, E12.00 (approx. $30). Recent years have witnessed a relatively important renaissance in research on impact and stress wave effects in solids. Int’erest stems from sources as diverse as high speed metal forming, micro-meteorite cratering, vehicular crashworthiness and energy absorbers. However, instruction in the most basic notions of impact and stress waves have generally been absent from most undergraduate engineering curricula, the lack of an introductory text being a primary reason. This is the expressed motivation for the development of Impact Strength of Materials. In contrast with other monographs on the subject, a technological approach is employed, i.e., in the spirit of strength of materials as opposed to continuum mechanics. The aim is for material that can be used by a large number of students and practicing engineers. This objective is achieved with the presentations of elastic wave theory, applications of elastic stress waves and plasticity theory. The chapters on dynamic loading of beams, rings, frames and plates are somewhat specialized and reflect the author’s background in large plastic deformation and high velocity metal forming as opposed to a traditional structural engineering approach. For example, only plastic response of such structural components to impact loads is considered. A variety of “semi-infinite media” problems are discussed as well, e.g., indentation byprojectiles, jet penetration, water cannons, hypervelocity impact, camouflet and earth shifting problems. The text is presented in a stimulating style with excellent illustrations and 72 fascinating plates. It should certainly have a catalytic effect on instruction and also research on impact phenomena in solids for quite some time. EDWARD G. LOVELL Engineering Mechanics Department University of Wisconsin Madison, Wisconsin
DIGITAL FILTERS, by M. H. Ackroyd. 82 pages, diagrams, 6 x 9 in. London, Butterworths, 1973. Price, ~21.85 (approx. $7.50); Butterworths, Toronto, Canada.
In t.his book, which is part of the ‘Computers in Medicine” series, Dr. Ackroyd concisely and clearly introduces a newcomer to Digital Filters and although the applications have naturally been taken from medical problems, anyone working in a different field should not be deterred as the contents are applicable to such filters used in any area of signal processing. The introductory chapter sets a perspective for digital filters by explaining what they are, why and how they are used and what advantages they have over analogue circuits. It then proceeds to cover the essentials of sampling by briefly explaining analogue-to-digital conversion, Z-transforms, transfer functions, poles and zeros, and the concept of a frequency response, and finally includes a discussion of how t’o program digital filters from a block diagram approach. Then the design of recursive and nonrecursive filters is considered. The author quickly discusses the properties of each type, reviews the approaches available and concentrates on a specific technique: Butterworth and Chebyshev design for recursive and windowing for non-recursive filters. As continual reference is made to the FORTRAN subroutines listed in the Appendix, a newcomer is immediately able to try his hand at designing filters and thus get a feel for the subject. For someone who needs to use other methods, Dr. Ackroyd includes a useful set of References and a comprehensive Bibliography. Finally, a chapter deals with applications such as noise reduction, signal analysis and equilization, and again there is constant reference to practical points, perhaps it is this that makes the book so readable. L. G. CUTHBERT Queen Mary College University of London, London
297 15