A Unified Statistical Methodology for Modeling Fatigue Damage

ISBN-13: 9781402091810 / Angielski / Twarda / 2009 / 232 str.

Enrique Castillo; Alfonso Fernandez-Canteli

Opis

This book is an attempt to provide a uni?ed methodology to derive models for fatigue life. This includes S-N, ?-N and crack propagation models. This is not a conventional book aimed at describing the fatigue fundamentals, but rather a book in which the basic models of the three main fatigue approaches, the stress-based, the strain-based and the fracture mechanics approaches, are contemplated from a novel and integrated point of view. On the other hand, as an alternative to the preferential attention paid to deterministic models based on the physical, phenomenological and empirical description of fatigue, their probabilistic nature is emphasized in this book, in which stochastic fatigue and crack growth models are presented. This book is the result of a long period of close collaborationbetween its two authors who, although of di?erent backgrounds, mathematical and mechanical, both have a strong sense of engineering with respect to the fatigue problem. When the authors of this book ?rst approached the fatigue ?eld in 1982 (twenty six years ago), they found the following scenario: 1. Linear, bilinear or trilinear models were frequently proposed by relevant laboratoriesandacademiccenterstoreproducetheW] ohler?eld. Thiswas the case of well known institutions, which justi?ed these models based on clientrequirementsorpreferences. Thisledtotheinclusionofsuchmodels and methods as, for example, the up-and-down, in standards and o?cial practical directives (ASTM, Euronorm, etc.), which have proved to be unfortunate.

Recenzje

From the reviews:

"This book provides a unified methodology to derive models for fatigue life. ... The book gives a new methodology to build-up fatigue models based on a practical knowledge of fatigue problems, combined with common sense, functional equations and statistical methods. ... Appendix presents a short description of classical and more recent fatigue models existing in the literature. The proposed models allow simple approaches to be implemented in a practical fatigue design, similar to those employed in current engineering standards." (Razvan Raducanu, Zentralblatt MATH, Vol. 1161, 2009)

Spis treści

Introduction and Motivation of the Fatigue Problem An Integrated Overview of Fatigue 1.1 Introduction 1.2 Models with dimensionless variables 1.3 S-N or Wohler curves 1.3.1 Compatibility condition of NlAo and AalN 1.3.2 Statistical considerations 1.4 E-N curves 1.5 Stress-level effect 1.5.1 Compatibility condition of S-N curves for constant o;T, and S-N curves for constant a& 1.6 Crack-growth curves 1.6.1 Crack-growth curves for a constant stress pair T 1.6.2 Crack-growth curves for a varying stress pair T 1.6.3 Compatibility of crack-growth and S-N models 1.7 Crack-growth rate curves 1.8 Size effect 1.9 Normalization 1.9.1 Percentilebased normalizations 1.9.2 Stress range and lifetimebased normalizations 1.9.3 Extended percentile normalization 1.10 Damage measures and damage accumulation 11 Models Used in the Stress-Based Approach 2 S-N or Wohler Field Models 2.1 Introduction 2.2 Dimensional analysis 2.3 Extreme models in fatigue 2.3.1 The Weibull model 2.3.2 The minimal Gumbel model 2.4 Model for constant stress-level and range 2.4.1 Derivation of the model 2.4.2 Parmeter estimation 2.4.3 Alternative methods for dealing with run-outs 2.5 Model for a given stress-level and varying range 2.5.1 Derivation of the model 2.5.2 Some weaknesses of the proposed model 2.5.3 Parameter estimation 2.5.4 Use of the model in practice 2.5.5 Examples of application 2.6 Model for varying stress-level and range 2.7 Dimensional Weibull and Gumbel models 2.8 Properties of the model 2.8.1 Parameter estimation 2.8.2 Use of the model in practice 2.8.3 Example of applications 2.9 Concluding remarks 2.10 Appendix A: Derivation of the general model 2.11 Appendix B: S-N curves for the general model 3 Length Effect 3.1 Introduction 3.2 Modeling the S-N field for different lengths 3.2.1 A previous example 3.2.2 General model for different lengths 3.2.3 Parameter estimation 3.3 Examples of applications 3.3.1 Prestressing wires 3.3.2 Prestressing strands I11 Models Used in the Strain-Based Approach 4 Log-Weibull e-N Model 4.1 Introduction 4.2 Model for a constant strain level and range 4.2.1 Practical example 4.3 Model for a varying strain level and range 4.4 Converting strain into stress-life curves 4.4.1 Practical example 4.5 Concluding remarks IV Models Used in the Fracture-Mechanics Approach 5 Crack-Growth Models 5.1 Introduction and motivation 5.2 Building crack growth models 5.3 Crack-growth curves approach I 5.3.1 Crack-growth curves for constant Aa and a 5.3.2 Crack-growth curves for varying AD and a 5.3.3 Compatibility of crack-growth and S-N models 5.4 crack-growth curves approach I1 5.4.1 crack-growth curves for constant Aa and a; 5.4.2 crack-growth curves for varying Aa and a 5.4.3 Statistical distributions of aI N and Nla 5.4.4 Learning and estimating the mode1 5.4.5 Compatibility of approaches I and I1 5.5 Example of application 5.6 Summary and future work V Damage and Damage Accumulation Models 6 Damage Measures 6.1 Introduction 6.2 Normalization 6.3 Damage measures 6.3.1 Some requirements for a damage measure 6.3.2 Some damage measures 6.4 Concluding remarks 7 Damage-Accumulation 7.1 Damage-accumulation 7.1.1 Accumulated damage after a constant

Blurb

This book aims to provide a unified methodology to derive models for fatigue life prediction. This includes S-N, e-N and crack propagation models. This book is unique in that it contemplates the three main fatigue approaches (stress-based, strain-based and fracture mechanics) from a novel and integrated point of view. As an alternative to the preferential attention paid to deterministic models based on the physical, phenomenological and empirical description of fatigue, their probabilistic nature is emphasized in this book, in which stochastic fatigue and crack growth models are presented.

After an introductory chapter in which an overview of the book is provided, the following chapters are devoted to derive models for the S-N fields for fixed and varying stress level, the e-N fields, the relations between the two, and an analysis of the size effect in fatigue problems. Next, crack grow models are derived based on fracture mechanics, statistical and common sense considerations, which lead to functional equations providing non-arbitrary models. Two different approaches are given, leading to two classes of models, the intersection class of which is derived through compatibility analysis. Then the compatibility of the S-N curves model and the crack growth model, which are two aspects of the same fatigue problem, are used to obtain a model which allows both approaches to be connected. Finally, the problem of selection damage measures is analyzed, and some damage measures are proposed as the most convenient, including the probability of failure and a normalized measure related to the percentile curve. This leads to very simple and useful damage accumulation models, which are illustrated with some examples.

The book ends with an appendix with a short description of some classical and some more recent fatigue models of those existing in the literature.