Principles of Fracture Mechanics

by Sanford, R. J.

• ISBN13: 9780130929921
• ISBN10: 0130929921
• Edition: 1st
• Format: Paperback
• Copyright: 2002-03-29
• Publisher: Pearson

Summary

The book is a self-contained manual on the mechanics aspects of the theory of brittle fracture and fatigue. It includes a guided introduction to the linear theory of elasticity with pivotal results for the circular hole, the elliptical hole and the wedge leading up to the general problem of bodies containing cracks.Typical chapters include problems which extend the mathematical developments presented in the book, applications problems requiring numerical and/or graphic responses, and essay/literature study questions. Additionally, more comprehensive exercises requiring integration of the knowledge throughout the book are included as an appendix.For professionals in fields of engineering mechanics and design.

Author Biography

Professor Emeritus R.J. Sanford has had two careers involving fracture mechanics. He spent 22 years at the Naval Research Laboratory as a research engineer during a period of intense fracture mechanics discovery at NRL under the direction of George R. Irwin. He left NRL in 1982 to join the faculty at the University of Maryland. At the College Park campus his focus has been on graduate education in solid mechanics and fracture. He is a Fellow in the Society for Experimental Mechanics and has received both their Hetenyi Award (for research) and the Frocht Award (for teaching excellence) and is a member of Committee E08 of the American Society for Materials and Testing (ASTM).

Table of Contents

Most chapters include an Introduction, Summary, References and Exercises.
1. Introduction to Fracture Mechanics.

Historical Overview of Brittle Fracture. Elementary Brittle-Fracture Theories. Crack Extension Behavior.

2. Elements of Solid Mechanics.

Concepts of Stress and Strain. Equations of Elasticity in Cartesian Coordinates. Equations of Elasticity in Polar Coordinates. Solution of the Biharmonic Equation. The Problem of the Elliptical Hole.

3. Elasticity of Singular Stress Fields.

Overview. The Williams Problems. The Generalized Westergaard Approach. The Central Crack Problem. Single-Ended Crack Problems. The Effect of Finite Boundaries. Determining the Geometric Stress Intensity Factor. The Three-Dimensional Crack Problem.

4. Numerical Methods for K Determination.

Boundary Collocation. The Finite Element Method.

5. Experimental Methods for K Determination.

Overview. Classical Photoelesatic Methods. The Method of Caustics. Strain Gages. Multi-Parameter Full-Field Methods: Local Collocation. Interference Patterns. Moire Patterns. Photoelasticity.

6. A Stress Field Theory of Fracture.

The Critical Stress-State Criterion. Crack-Tip Plasticity. The Effect of Variables on Fracture Toughness. R-Curves.

7. The Energy of Fracture.

Griffith's Theory of Brittle Fracture. A Unified Theory of Fracture. Compliance.

8. Fracture Toughness Testing.

Fracture Toughness Standards. Nonstandard Fracture-Toughness Tests.

9. Fatigue.

Stages of Fatigue Crack Growth. Mathematical Analysis of Stage II Crack Growth. The Effects of Residual Stress on Crack Growth Rates. Life Prediction Computer Programs. Measuring Fatigue Properties: ASTM.

10. Designing against Fracture.

Fracture Mechanics in Conventional Design. The Role of NDE in Design. U.S. Air Force Damage-tolerant Design Methodology. Designing by Hindsight: Case Studies.

11. Elastoplastic Fracture.

Nonlinear Elastic Behavior. Characterizing Elastoplastic Behavior. Comments on the J-Integral in Elastoplastic Fracture Mechanics.

Appendix A: Comprehensive Exercises.

General Comments.

Appendix B: Complex Variable Method in Elasticity.

Complex Numbers. Complex Functions.

Appendix C: An Abbreviated Compendium of Westergaard Stress Functions.
Appendix D: Fracture Properties of Engineering Materials.
Appendix E: NASGRO 3.0 Material Constants for Selected Materials.
Index.

Excerpts

OVERVIEW Fracture mechanics as an engineering discipline was introduced in the 1950s under the leadership of George R. Irwin at the Naval Research Laboratory (NRL). The concepts of fracture mechanics were further developed and refined throughout the 1960s by a collaboration of researchers in universities, government laboratories, and the commercial aircraft and aerospace industries. Definable within the context of the linear theory of elasticity, the fundamentals of fracture mechanics have a wide range of engineering design applications, including the analysis of brittle fracture of low-toughness structural materials and many nonmetallics, and the quantitative prediction of fatigue crack growth in a wide range of engineering materials. This latter application is of major importance in contemporary engineering design since over 80 percent of all brittle fractures have their origins in fatigue crack growth. In its current state of development, the discipline of Linear Elastic Fracture Mechanics (LEFMs) is a mature science that can be and, indeed, is being introduced into the basic programs of instruction in mechanical, civil, aerospace, and engineering mechanics departments. The focus of this book, intended for a first course in the mechanics of fracture at the graduate level (or for senior undergraduates with a background in engineering mechanics), is on the mathematical principles of linear elastic fracture mechanics and their application to engineering design. The selection of topics and order of presentation in the book evolved from a graduate course in fracture mechanics developed by the author over the last two decades. The material has been tested on several hundred students over that time, and the level of treatment and extent of mathematical development presented in the text are the result of feedback provided by the students. Many of the chapter exercises and comprehensive design problems are taken from examinations given in the course. A Web site at the University of Maryland ( www.wam.umd.edu/~rsanford ) contains supplemental material, including detailed graphics, data sets, and relevant links to supporting material. The site also provides a convenient way to communicate your suggestions and comments to the author. The material is presented in a conversational, yet rigorous, manner, with the focus on the general formulation of the theory. In this way the origins and limitations of the simplified results presented in other introductory texts are apparent. Throughout the text, key historical results are emphasized to provide a sense of the history of fracture mechanics. This feature makes the book of interest to practicing engineers and researchers interested in a broad overview of the field. Ideally, the study of LEFM should have as a prerequisite a thorough understanding of the linear theory of elasticity: however, the practicalities of scheduling graduate instruction often result in the student having no choice but to study both topics concurrently. The organization of the book anticipates this possibility by including, early on, a chapter on those elements of solid mechanics necessary for understanding the remainder of the text. The minimum mathematical background required to gain a full appreciation of the material is a one-semester introductory course in partial differential equations (often taught at the undergraduate junior level) or its equivalent. Some familiarity with complex variables and functions, but not necessarily a comprehensive knowledge, is also required. Also, some of the exercises assume proficiency in computer-based problem solving at the PC or workstation level. KEY FEATURES OF THE BOOK The book is a self-contained manual on the mechanics aspects of the theory of brittle fracture and fatigue and is suitable for either self-study or classroom instruction. It includes a guided introduction to the l