9R8. Mechanical Shock. Mechanical Vibration and Shock Series, Vol II.- C Lalanne (French Atomic Energy Authority, France). Hermes Sci Publ, Paris. Distributed in USA by Taylor & Francis Publ, New York NY. 2002. 320 pp. ISBN 1-56032-986-6. $150.00.
Reviewed by C Cetinkaya (Dept of Mech and Aeronaut Eng, Clarkson Univ, CAMP 241, Box 5725, Potsdam NY 13699-5725).
The title under review is the English translation of the original volume published in French in 1999. The work covered appears to be based on the author’s professional experience in the French Atomic Energy Authority as a vibration and shock specialist and test specifications developer. This title is the second volume of the author’s five-volume set entitled Mechanical Vibration and Shock. The other volumes cover harmonic excitations, random vibrations, fatigue, and test specification development.
Protecting the human, structures, material, etc, from impact loading conditions has been an essential concern for designers and engineers in modern applications in which operational speeds and power have been steadily increasing. The title under review covers various well-established shock engineering techniques from mathematical analysis to test specification generation for practical use. Compared to other available titles, such as Optimal Protection from Impact, Shock, and Vibration by DV Balandin, NN Bolotnik, and WD Pilkey, the current title is set out to address more practical aspects of the effects of impact and shock testing. In this reviewer’s opinion, its main audience will be experimentalist, practicing engineers and technicians working in the areas of impact protection and safety. The primary objective of the book is to assist technical professionals to develop impact (shock) test specifications, qualification and certification documents.
The book consists of nine chapters. Most chapters begin with a number of concise definitions of the concepts used in the rest of the chapter. While many of these definitions are useful, some would differ slightly from some commonly used definitions used in many English books. Perhaps, every translation book suffers from this minor terminology shift. For example, in 1.1.4 the following is given as a definition for bump: “a bump is a simple shock which is generally repeated many times in testing.” This concept appears to be close to “pulse” or “waveform.” Another example on terminology is the usage of the word digitization in the book for discretization of a function in time (sampling). Introductions are typically brief. Each chapter contains a generous number of plots. While the plots are not as polished as those in high-volume textbooks, they are adequate and useful in clarifying the materials. Listings of a few computer codes developed in BASIC programming language are also contained. However, no CD or diskette comes with the book, so the reader who is interested in running numerical simulations is expected to type these programs in.
The book is concerned strictly with linear and discrete systems. Most of the systems considered are low degree-of-freedom (dof) while some multi-dofs are occasionally used. Virtually all the analysis is based on the Fourier transform of ordinary differential equations modeling system dynamics. A college-level calculus background should be sufficient to follow the derivations and analyses presented in the book.
Chapter 1, entitled Shock Analysis, solely focuses on how the frequency spectra of temporal functions are obtained using Fourier transform and sampling theory (based on the fast Fourier transform algorithm). This is a brief, yet useful overview. In Chapter 2, the frequency responses of spring-mass-dampers systems are discussed in detail. The time and frequency responses of single- and multi-dof under various“standard” dynamic loading conditions are listed. These standard loading conditions are later used in the development of test specifications. Numerical algorithms for calculating system responses are provided. A program developed in BASIC for shock response spectrum of a single-dof is included. Chapter 3 is devoted to shock response of a system at three different frequency ranges: low frequency (static domain), intermediate frequency, and high frequency (impulse domain). Amplitudes of responses of systems in these ranges are discussed and various practical relationships are derived and analyzed. Many examples illustrating the uses of these relationships are provided. This is the most mathematical of all the chapters in the book.
Development of detailed shock testing and measurement specifications for practical use is the main theme of Chapter 4. Various simplification and idealization methods for the impact loading conditions used in the development of test specifications have been discussed in great detail. The role of shock, amplitude, and duration choices in simplifying and representation of the waveforms in testing processes is discussed with many examples. Various simulation techniques are introduced and discussed.
Chapter 5 is a brief chapter focusing on kinematics of the shock excitation forms. The shocks are defined as applied acceleration, velocity, and displacement to an elastic system. Pulse shapes such as half-sine, rectangular, and peak saw are considered with various cases of rebounds. These concepts serve as background for the discussions in the following chapters. Standard shock machines are discussed in Chapter 6. A review of the testing systems utilized in practice is provided. The coverage of the programmers generating desired excitation acceleration profiles is particularly interesting. While a minimal amount of actual experimental data is included in the chapter, the descriptions of test machines and programmers are rather clear. The commercially available MTS test machines and programmers have been covered in somewhat detail. Another useful feature of Chapter 6 is that a number of examples are included. Compared to the shock machines covered in Chapter 6, with electrodynamics exciter known as shakers, more versatile excitation profiles can be generated with better reproducibility of impact. Chapter 7 offers a detailed comparison of shakers with other shock generation methods. In Chapter 8, a brief coverage of damage-based shocks generated by explosive charges is provided with various comparisons.
The final chapter of the book is devoted to the control of shakers to generate particular types of excitations with pre-set shock re sponse spectra. The shock profiles obtainedwith the use of simple drop tests (covered in Chapter 6) are typically insufficient to recreate many practical impact conditions for testing purposes. Actively controlled shakers using analog and digital methods are discussed. Plots provided for various excitation waveforms functions (such as ZERD and WAVESIN) could be particularly useful in selecting an appropriate waveform for an application. In addition to an appendix on dimensional scaling in experimental simulations, a brief history on the development of mechanical test machines has been provided with the book.
Considering the content and depth of Mechanical Shock, practicing engineers and technicians who work in testing and test specification development areas will find this book particularly useful. Also, students and researchers looking for a concise introduction to the field of established impact and shock testing methods would apply practical techniques covered in the book to their specific impact problems. Some readers might find the references to French impact codes particularly interesting. This title can also be used as a quick reference in research laboratories, machines shops, and workshops.