Residual Stress

Abstract

As industries find that the market for their goods and services is often as closely connected to their quality as to their price, they become more interested in inspection and quality control. Non-destructive testing is one aspect of this topic; the subject of this book is a sub-field of this domain. The techniques for measuring residual stresses have a long history for a technological subject. Yet, in the last decade or so there has been renewed and vigorous interest, and, as a result of this, there has been considerable progress in our understanding and in our methods. It seemed a proper time to bring the new material together in an organized form suitable for a course or for self-teaching, hence this book.After an initial introduction to the qualitative ideas concerning the origin, role, and measurement of residual stresses, we follow with chapters on classical elasticity and the relatively new subject of microplasticity. These are primarily introductory or review in nature, and the reader will find it important to consider further the quoted references if he is to be involved in a continuing basis in this area. There follows a chapter on diffraction theory, and then we fuse these subjects with a chapter on diffraction techniques for measuring stresses and strains which at present is our most general tool for non-destructive evaluation in this area. In Chap. 6 we explore how to evaluate errors in such a measurement, a topic almost as important as the stress itself and certainly vital in automating the measurement. Practical examples are described in Chap. 7 and means for measuring the strain distribution, in Chap. 8, in contrast to the measurement of average values described in the earlier chapters.The Appendices include solutions to the problems given at the end of some of the chapters, Fourier analysis, and sources of useful data.We emphasize diffraction because in our opinion it is the most well understood and reliable tool available for the measurement of stresses. Of course our own background in niffraction colors our opinion, but we hope this book will reveal to the reader why we feel this way.Dr. M. James provided Appendices E and F, and Mr. W. P. Evans supplied many practical examples for Chap. 7. Both gave us helpful comments on the manuscript.

On the diffractive determination of single-crystal elastic constants using polycrystalline samples

“…The problem can be understood as the inverse to that of the typical diffractive residual-stress analysis (Noyan & Cohen, 1987;Hauk, 1997). In the latter case, the components of the mean (`macroscopic') second-rank stress tensor ' in the irradiated volume of the sample need to be determined, using (a) the known single-crystal constants 0 S, (b) the measured d hkl for several sample directions y, (c) information on the structure/texture of the sample, and (d) a micro-mechanical model that combines the orientation-dependent individual strains and stresses of the interacting grains of the polycrystalline sample with the d hkl (y).…”

“…Recently, a growing number of groups have been tackling the inverse problem (Bittorf et al, 1998;Singh et al, 1998;Gna È upel-Herold et al, 1998;Howard & Kisi, 1999). However, as for the direct problem of stress analysis (Noyan & Cohen, 1987), in general only relatively simple situations have been considered, such as high crystal symmetries, no texture, and micro-mechanical models with Reussand Voigt-like assumptions, linear in 0 S or 0 C averaging.…”

Non-destructive Micro-structural Characterization of Metallic Specimens with a Portable X-ray Diffraction based Residual Stress Analyzer

“…The procedure of stress measurements involves recording profile of a diffraction peak (for a given crystallographic plane) at different inclination angles ѱ (angle between associated crystallographic plane (hkl) and specimen surface normal) with inter planar spacing "d" (refer figure 1b). Using the resultant d-Sin 2 ѱ plot, the magnitude of surface residual stress in the given direction is estimated (Cullity 1978, Noyan & Cohen, 1987. The investigated spot on surface of the specimen is controlled by using apertures of different sizes.…”

Residual Stress in Metal-Matrix Composite Cylinder Measured by Neutron Diffraction and Contour Method

“…Neutron diffraction is particularly suitable for measuring both the micro-and macrostresses in composite materials [2] although analysis of the data is notoriously…”

“…Neutron diffraction is particularly suitable for measuring both the micro-and macrostresses in composite materials [2] although analysis of the data is notoriously difficult, requiring the solution of the d 0 problem (i.e., a knowledge of the stress-free lattice parameter of each phase of a composite), the choice of elastic constants [3] and, finally, the separation of the micro-and macrostress fields [4]. With all these experimental difficulties, a reliable alternative method is highly desirable for validation.…”