Preface

Residual stress experimental analysis is a topic of great relevance where a lot of effort over the years has led to the development of a considerable number of experimental methods that can be applied conveniently to several different measurement situations. In spite of the large number of papers that have been published in the last decades, the subject is far from be considered as concluded, on the contrary, a lot of research is currently being undertaken in many different directions such as the improvement of the resolution of the measurement, the capability of measuring residual stress even in the core of the component as well as increasing the level of portability and usability of the instrumentation. At the same time, numerical methods have also been under study in order to develop powerful and accurate analytical instruments to predict the level of introduced residual stress along each step of the complex production chain starting with material production and ending with the final manufactured part. The increasing number of materials for which residual stress evaluation is required (nowadays also including biomaterials, additive manufactured materials and composites) makes this challenge even wider. Far from being a comprehensive review of the research performed on this topic, this book specifically aims to provide updated information on some of the most recent advancements in this field. The book opens with an introductory chapter that provides the reader with an overview of the most recent progresses by identifying the most appealing routes for future developments. Some of that will then be discussed in the following chapters of this book divided into two sections. In the first section research advances in experimental methods for residual stress measurements are discussed while the second section is devoted to the advances in residual stress modelling and prediction. In Chapter 1, a very innovative and promising approach is illustrated based upon the synergic use of the Electronic Speckle Pattern Interferometry and the acoustic method. The evaluation of the sound velocity is proposed as a tool for evaluating the elastic modulus and, consequently, the local residual stress while the full-field character of ESPI is exploited to obtain a 2D distribution of the stress field. In Chapter 2, two alternative non-destructive approaches are compared based on the analysis of the magnetic and acoustic response of a material as it is modified by the presence of locked-in residual stress. In particular, interesting observations can be found in relationship to the possibility to evaluate RS at the macro- and micro-scale.

In Chapter 3, experimental analysis using the classical approach of the hole-drilling methods is presented. Even being a well-known, consolidated and standardized method, the authors present a novel approach that is promising in overcoming some current limitations and improving the level of attainable accuracy. In Chapter 4, a coupled thermo-mechanical finite element model is presented allowing determination of residual stress distribution and distortion in a stainless steel part manufactured by direct metal deposition, with an experimental validation presented as well. In Chapter 5, an Inverse Finite Element Method is proposed for evaluating residual stress in thick butt weld joints as well as a validation procedure based on the contour method. Finally, in Chapter 6, a study of residual stress simulation is presented for the case of a steel cylindric block, once calculated the simulated stress field is used as an input for accurate durability assessment.

**II**

**Chapter 6 107**

**Chapter 7 125**

Residual Stress Evaluation with Contour Method for Thick Butt

*by Qingya Zhang, Hong Zhou and Jiangchao Wang*

Durability Assessment Considering Residual Stress

Welded Joint

*by Byung-Ik Kang*

As editor I would like to express my gratitude to all the authors that have contributed their work and their experience to this book. I also would like to acknowledge my co-editors Claudia Barile, Vincenzo Moramarco and Giovanni Pappalettera for their valuable contribution. Our greatest wish is that this publication is useful for experts in the residual stress field and inspiring for young researchers approaching this challenging field.
