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Über dieses Buch

Mechanical engineering, an engineering discipline born of the needs of the industrial revolution, is once again asked to do its substantial share in the call for industrial renewal. The general call is urgent as we face profound issues of productivity and competitiveness that require engineering solutions, among oth­ ers. The Mechanical Engineering Series features graduate texts and research monographs, intended to address the need for information in contemporary areas of mechanical engineering. The series is conceived as a comprehensive one the will cover a broad range of concentrations important to mechanical engineering graduate education and research. We are fortunate to have a distinguished roster of consulting editors, each an expert in one of the areas of concentration. The names of the consulting editors are listed on the first page of the volume. The areas of concentration are applied mechanics, biomechanics, computational mechanics, dynamic systems and control, energetics, mechanics of materials, processing, thermal science, and tribology. Professor Winer, the consulting editor for applied mechanics and tribology, and I are pleased to present this volume of the series: High Sensitivity Moire: Experimental Analysis for Mechanics and Materials by Professor Post, Dr. Han and Dr. Ifju. The selection of this volume underscores again the interest of the Mechanical Engineering Series to provide our readers with topical monographs as well as graduate texts.

Inhaltsverzeichnis

Frontmatter

Introduction

1. Introduction

Abstract
We live in an amazing period of technological and scientific expansion. The rapid advance of computer modeling and computer simulation is largely responsible, together with advancing techniques of physical measurement and efficient data analysis. The book is devoted to one element in this spectrum, the physical measurement.
Daniel Post, Bongtae Han, Peter Ifju

Fundamentals

Frontmatter

2. Elements of Optics

Abstract
This introduction is a brief treatment of the concepts and tools of optics encountered in the following chapters. Standard textbooks on optics can be consulted for more information. The wave theory of light is sufficient to explain all the characteristics of moiré. In what follows, we will describe a model of light consistent with the wave theory. A parallel beam of light propagating in the z direction is depicted at a given instant as a train of regularly spaced disturbances that vary with z as
$$A = a\cos 2\pi \frac{z}{\lambda }$$
(2.1)
For mathematical convenience, this expression is often replaced by the real part of the complex equation
$$A = a{{e}^{{i2\pi \frac{z}{\lambda }}}}$$
(2.1a)
The symbol A describes the strength of the disturbance, which is usually viewed as the strength of an electromagnetic field at a point in space, particularly, the electric field strength; A will be called field strength. The coefficient a is a constant called the amplitude of the field strength. The field strength varies harmonically along z, where the distance between neighboring maxima is λ, called the wavelength.
Daniel Post, Bongtae Han, Peter Ifju

3. Geometric Moiré

Abstract
Our goal in this chapter is to build a foundation for easy assimilation of the concepts of high-sensitivity moiré interferometry. An additional goal is to review many ideas of geometric moiré that are usually addressed in the study of optical methods of experimental mechanics and engineering practice.
Daniel Post, Bongtae Han, Peter Ifju

4. Moiré Interferometry

Abstract
Moiré interferometry combines the concepts and techniques of geometrical moiré and optical interferometry. In his definitive monograph, Guild1 shows that all moiré phenomena can be treated as cases of optical interference, although moiré generated by low-frequency bar-and-space gratings can also be explained by obstruction or mechanical interference. Moiré interferometry is capable of measuring in-plane displacements with very high sensitivity. A sensitivity of 2.4 fringes/µm displacement is demonstrated for all the patterns in this chapter except Figs. 4.7 and 4.45, where the sensitivity is 4.0 and 1.2 fringes/µm displacement, respectively. In Chapter 5, the sensitivity is even higher.
Daniel Post, Bongtae Han, Peter Ifju

5. Microscopic Moiré Interferometry: Very High Sensitivity

Abstract
Many fields of study require deformation measurements of tiny specimens or tiny regions of larger specimens. The mechanics of microelectronic assemblies is an example, where the ever increasing demand for closer packing exacerbates the problems of thermal stresses. Other fields include crack-tip analyses in fracture mechanics; grain and intragranular deformations of metals and ceramics; interface problems; etc. Moiré interferometry adapted for such micromechanics studies is the subject of this chapter.
Daniel Post, Bongtae Han, Peter Ifju

6. On the Limits of Moiré Interferometry

Abstract
The main focus of this chapter is potential limitations imposed by the aperture of the camera lens. Numerical and experimental investigations were performed to validate moiré interferometry for extremely large strain gradients and discontinuities.
Daniel Post, Bongtae Han, Peter Ifju

Applications and Advances

Frontmatter

7. Laminated Composites in Compression: Free-edge Effects

Abstract
This chapter excerpts material from a series of tests of thick laminated composites in compression.1 As illustrated in Fig. 7.1, the graphite/epoxy specimens were cut from thick-walled cylinders with two different stacking sequences (i.e., the sequence of fiber directions in successive plies of the laminate). They are called quasi-isotropic and cross-ply laminates. In-plane and interlaminar compression tests were conducted, with the compressive loads applied parallel and perpendicular to the plies, respectively. Note that the coordinate system maintains x perpendicular to the plies and y parallel to the plies. The loading fixture of Fig. 4.10 was used.
Daniel Post, Bongtae Han, Peter Ifju

8. Thermal Stresses Near the Interface of a Bimaterial Joint

Abstract
The state of elastic strains and stresses in a bimaterial joint subjected to a uniform change of temperature was analyzed by moiré interferometry.1,2 The specimen configuration is illustrated in Fig. 8.1. The steel and brass plates were joined by a very thin, high-temperature silver-solder film along the mating surfaces. The experimental analysis measured the deformations caused by a change of temperature of -133°C.
Daniel Post, Bongtae Han, Peter Ifju

9. Textile Composites

Abstract
Although it was projected more than a decade ago that laminated composite materials would become the material of choice, aluminum is still the primary structural material for aircraft. High manufacturing costs, poor out-of-plane properties, and low damage tolerance1 have been limiting factors for laminated composites. In response to these shortcomings, a new generation of composite materials is being evaluated. This class of materials is called advanced textile composites. They have the potential for superior through-the-thickness properties, damage tolerance,2 and cost effectiveness.
Daniel Post, Bongtae Han, Peter Ifju

10. Thermal Deformations in Electronic Packaging

Abstract
An understanding and documentation of the micromechanics of electronic devices is critical to the industry, and moiré interferometry is taking a leadership role for experimental analyses. In the industry, the technology dealing with the interconnections of electronic components is called electronic packaging. Thermal strains are the major cause of fatigue failures of interconnections. The strains result from the mismatch of the thermal expansions of the various elements comprising the package. As the components and structures are made smaller, the thermal gradients increase and the strain concentrations become more serious. Hence, there is a continuously increasing activity in experimental analysis, both for specific studies and for guidance of numerical programs.
Daniel Post, Bongtae Han, Peter Ifju

11. Advanced Composites Studies

Abstract
Brief descriptions of several studies are presented in this chapter. Diverse experiments are described where the common thread is composite materials. They address the mechanics of highly complex bodies. These examples were chosen to demonstrate the broad scope of moiré interferometry and to express the virtue of whole field observations. These are not in-depth reports. Instead, numerous fringe patterns are shown and discussed to familiarize the reader with real-world analysis.
Daniel Post, Bongtae Han, Peter Ifju

12. Metallurgy, Fracture, Dynamic Loading

Abstract
A broad range of studies is introduced to emphasize the diverse capabilities of moiré interferometry. This work was performed during the last several years at six different photomechanics laboratories. They are at the Idaho National Engineering Laboratory (INEL), University of Strathclyde, University of Washington, Rockwell Science Center, IBM Corporation and Virginia Polytechnic Institute and State University (VPI&SU).
Daniel Post, Bongtae Han, Peter Ifju

13. Strain Standard for Calibration of Electrical Strain Gages

Abstract
Moiré interferometry can be used as a tool for precision measurements in numerous fields. In this chapter it will be applied to calibrate a test stand1 which will be used for subsequent calibration of strain gages. Electrical resistance strain gages are in extensive use in two fields: experimental strain (and stress) analysis and transducer measurements. In the latter category, they are used in engineering and in commercial products to measure force, torque, pressure, and other parameters.
Daniel Post, Bongtae Han, Peter Ifju

Backmatter

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