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Über dieses Buch

This book fills a unique position in the literature as a dedicated mechanical shock analysis book. Because shock events can be extremely damaging, mechanical shock is an important topic for engineers to understand. This book provides the reader with the tools needed to quantitatively describe shock environments and their damage potential on aerospace, civil, naval and mechanical systems. The authors include the relevant history of how shock testing and analysis came to its current state and a discussion of the different types of shock environments typically experienced by systems. Development of single-degree-of-freedom theory and the theory of the shock response spectra are covered, consistent with treatment of shock spectra theory in the literature.
What is unique is the expansion to other types of spectra including less common types of shock spectra and energy spectra methods using fundamental principles of structural dynamics. In addition, non-spectral methods are discussed with their applications. Non-spectral methods are almost completely absent from the current books on mechanical shock. Multi-degree-of-freedom shock spectra and multi-degree-of-freedom testing are discussed and the theory is developed. Addressing an emerging field for laboratory shock testing, the authors bring together information currently available only in journals and conference publications.
The volume is ideal for engineers, structural designers, and structural materials fabricators needing a foundation to practically analyze shock environments and understand their role in structural design.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract
The study of mechanical shock has its origins in several disciplines. Many aspects of the field originated with the military and the need to keep weapons and equipment functional and reliable under harsh operating conditions. Similarly, civil engineering needs have contributed through seismic resistant designs. Earthquakes can be extremely damaging and cause significant loss of life due to the unpredictable nature of the event and the fact that many structures have historically not been designed to be shaken. Shocks are also common in transportation systems: rail car couplings, poor quality roads, aircraft operation, and space systems. The various types of mechanical shock can precipitate both structural failures and functional failures. This chapter provides a historical introduction to the various types of mechanical shock.
Carl Sisemore, Vít Babuška

Chapter 2. Common Mechanical Shock Environments

Abstract
Mechanical shock events are as varied as the systems they influence. Shocks can occur in many forms, with many different dynamic parameters. While mechanical shocks can be varied in their sources and characteristics, many similarities do exist and the same analysis techniques are applicable to all types of mechanical shock events. This chapter provides an overview and context for several different types of mechanical shock events including transportation, handling, pyroshock, seismic, and military shocks. It is intended to introduce some of the most common sources of mechanical shock and show that while they originate from disparate sources, they have many similarities.
Carl Sisemore, Vít Babuška

Chapter 3. Single Degree-of-Freedom Systems

Abstract
This chapter introduces the response of single degree-of-freedom systems to shock loading. A single degree-of-freedom system is one whose motion is governed by a single, second-order differential equation. Only two variables, position and velocity, are needed to describe the trajectory of the system. Many structures can be idealized as single degree-of-freedom systems. Understanding how a single degree-of-freedom system responds to shock provides the engineer with important insights into the fundamental behavior of general systems. In this chapter, the transient response of a single degree-of-freedom system to a shock is described.
Carl Sisemore, Vít Babuška

Chapter 4. Shock Environment Characterization Using Shock Response Spectra

Abstract
This chapter introduces the shock response spectrum, or SRS, as one of the fundamental tools in shock analysis. Shock is a transient phenomenon requiring specialized tools and analysis techniques. The shock response spectrum provides information about the spectral content of the transient signal. The shock response spectrum is simply a plot of an extremal response quantity of interest from a series of SDOF oscillators to a transient excitation. This makes it a tool to assess the potential severity of shock excitation on a structure. Typical response quantities are maximum absolute acceleration and velocity, although numerous other options can be derived. This chapter discusses the origins of shock response spectra, presents information on the various types of shock response spectra, and methods for calculating the response spectrum from the transient excitation. Examples are provided along with optimal ways of presenting and interpreting the resulting spectra data.
Carl Sisemore, Vít Babuška

Chapter 5. Classical Shock Theory

Abstract
Classical shocks are defined by a single, one-sided shock pulse with a non-zero velocity change. There are five classical shocks: the haversine, half-sine, initial and terminal peak saw-tooth, and trapezoidal pulse shapes. Each of these shocks is easily described mathematically and can be easily replicated using shock test machines. This chapter discusses the different types of classical shocks and their unique characteristics and their similarities. Discussion of SRS properties specific to classical shocks and more generally to shocks with a non-zero velocity change is included. Also included are methods for interpreting specific SRS features, such as the low-frequency slope and the shock bandwidth, as they relate to the classical shocks.
Carl Sisemore, Vít Babuška

Chapter 6. Oscillatory and Complex Shock Theory

Abstract
Oscillatory shock pulses are more complex waveforms, often built up of multiple periodic, decaying harmonic functions. Oscillatory shocks also have sharp distinction from classical shocks in that there is little or no net velocity changes associated with the shock event. This chapter presents the SRS characteristics of oscillatory shocks including bandwidth and duration, inflection points in the SRS, and methods for interpreting the SRS for pure two-sided shocks and more complex shocks.
Carl Sisemore, Vít Babuška

Chapter 7. Design for Shock with SDOF Spectra

Abstract
When designing a laboratory shock test to simulate a shock environment measured in the field, the SRS serves as a common reference. If the two SRS are the same, then the laboratory test is considered to be representative and have the same damage potential as the field environment. But, what does it mean for two SRS to be the same? What features in the SRS are most important to represent faithfully in the laboratory environment? Another question is: how can the component designer use the SRS to make design decisions to make the part robust to shock. To answer this question, one again must know what features of the SRS are important and how to use them in component design. In Chap. 4, we briefly discussed how to assess the potential severity of shock excitation on a structure when we introduced the SRS. In this chapter, we expand on that to answer those questions and assist the component designer in passing shock tests.
Carl Sisemore, Vít Babuška

Chapter 8. Multi-Degree-of-Freedom Systems

Abstract
The single degree-of-freedom oscillator provides insight into the structural dynamics of linear systems, but real systems are more complex. Evaluating the response of general structures requires multi-degree-of-freedom (MDOF) models . Previously, we introduced the shock response spectrum as a tool to gain insight into the frequency content of a transient excitation. We also described how the SRS may be used to design a structure that can be represented as single degree-of-freedom system to survive shock loads. For MDOF systems the SRS is used primarily for structural design and efficient estimation of the response of a structure to transient excitation. In this chapter we review the basic concepts needed to understand the response of complex structures to shock (i.e., transient) excitation and how to use the SRS for transient analysis of MDOF systems.
Carl Sisemore, Vít Babuška

Chapter 9. Shock Testing

Abstract
Shock testing is a critical part of shock engineering, because it provides proof that the engineering was done correctly. Shock testing can be performed using a wide range of methods including: shock machines, shaker systems, actual system drops or crashes, and live-fire tests. This chapter discusses some of the more popular shock testing methods along with the applicability of the various methods. Shock test methods are very specialized and as a result it is very important to match the test method to the test requirements. This chapter provides information of drop test machines, resonant fixture shock machines, shaker shocks, and some of the specialized U.S. Navy shock machines. A discussion of fixture design is also included since fixtures are an integral part of testing.
Carl Sisemore, Vít Babuška

Chapter 10. Temporal Information

Abstract
The longest running criticisms of the shock response spectrum are that the transform is non-unique and that all temporal information is lost in the transform. This means that any number of theoretical shock time histories can be synthesized to yield nominally the same SRS. The risk then is that a very long duration shock might be used in the laboratory to mimic a very short duration field environment. There has long been an interest in preserving temporal information about the underlying shock pulse as an aid in synthesizing more appropriate laboratory tests by better understanding field data. This chapter is largely focused on the development and application of temporal moments to shock analysis. Temporal moments are derived and examples are presented to illustrate the fundamental concepts. In addition, a discussion of the limitations of temporal moments is provided along with examples.
Carl Sisemore, Vít Babuška

Chapter 11. Development of Shock Test Specifications

Abstract
Often, shock test specifications are provided by statute or contract and the goal is to perform the required test as defined. Other times, it is the engineer’s job to take environmental data and derive the appropriate shock test specifications based on the test goals. This chapter presents different methods for developing shock test specifications for different shock machines and how to match the measured environment to the test machine. A comprehensive discussion of test tolerances and test error is also presented. Finally, information about margin testing is provided as well as basic options for shock test compression.
Carl Sisemore, Vít Babuška

Chapter 12. Energy Spectra Methods

Abstract
This chapter presents an overview of energy response spectra and their application to single and multi-degree-of-freedom systems. The energy response spectrum falls into the group of analysis approaches called energy methods. The basis for energy methods is conservation of energy. Conservation of energy requires that all of the energy input to a structure be absorbed, dissipated, or converted to kinetic energy. The civil engineering community, specifically the earthquake engineering community, uses energy methods for analyzing the damage potential to structures from earthquakes. However, energy methods can provide insight into how any structure might fail when subjected to shock loading.
Carl Sisemore, Vít Babuška

Backmatter

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