Tài liệu ASM Metals HandBook P15 docx

Publication Information and Contributors Introduction Mechanical Testing and Evaluation was published in 2000 as Volume 8 of the ASM Handbook.. NASA Research Center at Lewis Field The n

ASM INTERNATIONAL ®

Publication Information and Contributors

Introduction

Mechanical Testing and Evaluation was published in 2000 as Volume 8 of the ASM Handbook The Volume

was prepared under the direction of the ASM Handbook Committee

Wright State University

• George (Rusty) Gray III

Los Alamos National Laboratory

• John (Tim) M Holt

Alpha Consultants and Engineering

Georgia Institute of Technology

National Institute of Standards and Technology

Polytechnique Institute (France)

NASA Research Center at Lewis Field

The new edition of ASM Handbook, Volume 8, Mechanical Testing and Evaluation is a substantial update and

revision of the previous volume This latest edition of Volume 8 contains over 50 new articles, and the scope of coverage has been broadened to include the mechanical testing of alloys, plastics, ceramics, composites, and common engineering components such as fasteners, gears, bearings, adhesive joints, and welds This new scope

is also complemented by substantial updates and additions in the coverage of traditional quasi-static testing, hardness testing, surface testing, creep deformation, high strain rate testing, fracture toughness, and fatigue testing

The efforts of many people are to be commended for creating this useful, comprehensive reference on mechanical testing The ASM Handbook Committee, the editors, the authors, the reviewers, and ASM staff

have collaborated to produce a book that meets high technical standards for the benefit of engineering communities everywhere To all who contributed to the completion of this task, we extend our sincere thanks ASH Khare

President, ASM International

processing ASM Handbook, Volume 20, Materials Selection and Design (1997) reflects this focus in

concurrent engineering and the broadening spectrum of involvement of materials engineers Second, new methods of measurement have evolved such as strain measurement by vision systems and ultrasonic methods for measurement of elastic properties This area will continue to grow as miniaturized sensors and computer vision technologies mature Third, computer modeling capabilities, based on fundamental continuum principles and numerical methods, have entered the mainstream of everyday engineering The validity of these computer models depends heavily on the availability of accurate material properties from mechanical testing

Toward this end, this revision of ASM Handbook, Volume 8 is intended to provide up-to-date, practical

information on mechanical testing for metals, plastics, ceramics, and composites The first section,

"Introduction to Mechanical Testing and Evaluation," covers the basics of mechanical behavior of engineering materials and general engineering aspects of mechanical testing including coverage on the accreditation of testing laboratories, mechanical tests in metalworking operations, and the general mecahnical tests of plastics and ceramics The next three sections are organized around the basic modes of loading of materials: tension, compression bending, shear, and contact loads The first four modes (tension, compression, bending, and shear) are the basic simple loading types for deterimation of bulk properties of materials under quasi-statis or dynamic conditions

The third section, "Hardness Testing," describes the various methods for indentation tesitng, which is a relatively inexpensive test of great importance in manufacturing quality control and materials science This section includes new coverage on instrumented (nano-indentation) hardness testing and the special issues of hardness testing of ceramics Following the section on hardness testing, the fourth section addresses the mechanical evaulation of surfaces in terms of adhesion and wear characteristics from point loading and contact loading These methods, often in conjunction with hardness tests, are used to determine the response of surfaces and coatings to mechanical loads

The next four sections cover mechanical testing under important dynamic conditions of slow strain rates (i.e., creep deformation and stress relaxation), high strain rate testing, dynamic fracture, and fatigue These four sections cover the nuances of testing materials under the basic loading types but with the added dimension of time as a factor Very long-term, slow rate of loading (or unloading) in creep and stress relaxation is a key factor in many high-temperature applications and the testing of viscoelastic materials On the opposite end of the spectrum, high strain rate testing characterizes material response during high-speed deformation processes and dynamic loading of products Fracture toughness and fatigue testing are the remaining two sections covering engineering dynamic properties These sections include coverage on the complex effects of temperature and environmental degradation on crack growth under cyclic or sustained loads

Finally, the last section focuses on mechanical testing of some common types of engineering components such

as gears, bearings, welds, adhesive joints, and mechanical fasteners A detailed article on residual stress measurements is included, as residual stress from manufacturing operations can be a key factor in some forms

of mechanical performance such as stress corrosion cracking and fatigue life analysis Coverage of reinforced composites is also included as a special product form with many special and unique testing and evaluation requirements

fiber-In this extensive revision, the end result is over 50 new articles and an all-new Volume 8 of the ASM Handbook

series As before, the key purpose of this Handbook volume is to explain test set-up, common testing problems and solutions, and data interpretations so that reasonably knowledgeable, but inexperienced, engineers can understand the factors that influence proper implementation and interpretation Easily obtainable and

recognizable standards and research publications are referenced within each article, but every attempt is made

to provide sufficient clarification so that inexperienced readers can understand the reasons and proper interpretation of published industrial test standards and research publications

In this effort, we greatly appreciate the knowledgeable guidance and support of all the section editors in developing content requirements and author recommendations This new content would not have been possible without their help: Peter Blau, Oak Ridge National Laboratory; James C Earthman, University of California, Irvine; Brian Klotz, General Motors Corporation; Peter K Liaw, University of Tennessee; Sia Nemat-Nasser, University of California, San Diego; Todd M Osman, U.S Steel Research; Gopal Revankar, Deere & Company; Robert Ritchie, University of California at Berkeley Finally, we are all especially indebted to the volunteer spirit and devotion of all the authors, who have given us their time and effort in putting their expertise and knowledge on paper for the benefit of others This work would not have been possible without them

• Ash Khare, President and Trustee, National Forge Company

• Aziz I Asphahani, Vice President and Trustee, Carus Chemical Company

• Michael J DeHaemer, Secretary and Managing Director, ASM International

• Peter R Strong, Treasurer, Buehler Krautkrämer

• Hans H Portisch, Immediate Past President, Krupp VDM Austria GmbH

Trustees

• E Daniel Albrecht, Advanced Ceramics Research, Inc

• W Raymond Cribb, Brush Wellman Inc

• Gordon H Geiger, University of Arizona-Tucson Office & Consultant, T.P McNulty & Associates

• Walter M Griffith, Wright-Patterson Air Force Base

• Jennie S Hwang, H-Technologies Group Inc

• C "Ravi" Ravindran, Ryerson Polytechnic University

• Thomas G Stoebe, University of Washington

• Robert C Tucker, Jr., Praxair Surface Technologies, Inc

• James C Williams, The Ohio State University

Members of the ASM Handbook Committee (1984–1985)

Boeing Commercial Airplane Group

Johnson Controls Inc

Previous Chairs of the ASM Handbook Committee

Conversion to Electronic Files

ASM Handbook, Volume 8, Mechanical Testing and Evaluation was converted to electronic files in 2003 The

conversion was based on the First printing (2000) No substantive changes were made to the content of the Volume, but some minor corrections and clarifications were made as needed

ASM International staff who contributed to the conversion of the Volume to electronic files included Sally Fahrenholz-Mann, Sue Hess, Bonnie Sanders, and Scott Henry The electronic version was prepared under the direction of Stanley Theobald, Managing Director

Copyright Information (for Print Volume)

Copyright © 2000 by ASM International

All rights reserved

No part of this book may be reproduced, stored, in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the written permission of the copyright owner

First printing, October 2000

This book is a collective effort involving hundreds of technical specialists It brings together in one book a wealth of information from world-wide sources to help scientists, engineers, and technicians to solve current and long-range problems

Great care is taken in the compilation and production of this volume, but it should be made clear that no warranties, express or implied, are given in connection with the accuracy or completeness of this publication, and no responsibility can be taken for any claims that may arise

Nothing contained in the ASM Handbook shall be construed as a grant of any right of manufacture, sale, use, or reproduction, in connection with any method, process, apparatus, product, composition, or system, whether or not covered by letters patent, copyright, or trademark, and nothing contained in the ASM Handbook shall be construed as a defense against any alleged infringement of letters patent, copyright, or trademark, or as a defense against any liability for such infringement

Comments, criticisms, and suggestions are invited, and should be forwarded to ASM International

Library of Congress Cataloging-in-Publication Data (for Print Volume)

ASM Handbook

Includes bibliographical references and indexes

Contents: v 1 Properties and selection—v 2 Properties and selection—nonferrous alloys and puremetals—[etc.]—v 8 Mechanical testing

1 Metals—Handbooks, manuals, etc 2 ASM International Handbook Committee

Introduction to the Mechanical Behavior of Metals

Todd M Osman, U.S Steel Research; Joseph D Rigney, General Electric Aircraft Engines

Fig 1 Typical specimens for (a) tension testing, (b) notched tension testing, and (c) fracture toughness testing

As will be highlighted throughout the discussion below, mechanical properties are highly dependent on microstructure (e.g., grain size, phase distribution, second phase content), crystal structure type (i.e., the arrangement of atoms), and elemental composition (e.g., alloying element content, impurity level) A common illustration of the relationship between micro-structure and mechanical performance is the often observed increase in yield stress with a decrease in grain size Relationships like these between metal structure and performance make mechanical property determination important for a wide variety of structural applications in metal working, in failure analysis and prevention, and in materials development for advanced applications The following discussions are designed to briefly introduce typical relationships between metallurgical features (such as crystal structures and microstructures) and the mechanical behavior of metals Using basic examples, deformation and fracture mechanisms are introduced Typical properties measured during mechanical testing are then related to these deformation mechanisms and the microstructures of metals

Introduction to the Mechanical Behavior of Metals

Todd M Osman, U.S Steel Research; Joseph D Rigney, General Electric Aircraft Engines

Structure of Metals

At the most basic level, metallic materials (as well as many nonmetallic ones) are typically crystalline solids, although it is possible to produce amorphous metals (i.e., those with random atomic arrangement) in limited quantities The basic building block of the crystal lattice is the unit cell, some examples of which are shown in Fig 2(a) through (d) By repeating this arrangement in three dimensions, a crystal lattice is formed (see Fig 2.) Although the arrangement of atoms in space can be of fourteen different types (or Bravais lattices), most metals have face-centered cubic (fcc) (e.g., nickel, aluminum, copper, lead), body-centered cubic (bcc) (e.g., iron, niobium, tungsten, molybdenum), or hexagonal close-packed (hcp) (e.g., titanium, magnesium, zinc) structures

as the unit cell structure In very specific applications, materials can be used as single crystals where an entire component is fabricated with one spatial orientation repeating throughout More often than not, however, engineering materials usually contain many crystals, or grains, as shown in Fig 3 Depending on the composition and thermomechanical processing, these grains are typically approximately 1 to 1000 μm in size (although finer grain sizes can be produced via other techniques) While the crystal lattice within a grain is consistent, the crystalline orientations vary from one grain to another

Fig 2 Examples of crystal structures Unit cells: (a) simple cubic, (b) face-centered cubic, (c) centered cubic, and (d) hexagonal close-packed A crystal lattice: (e) three-dimensional simple cubic

body-Fig 3 Examples of metallic microstructures: (a) Grains in an ultralow-carbon steel Courtesy of U.S Steel (b) Grains in pure niobium (c) Precipitates at grain boundaries in niobium (d) Discontinuously reinforced metal matrix composite (silicon carbide particles in an aluminum matrix) Source:Ref 1 Note: the grains in a–c are highlighted through the use of a chemical etchant

Although some nonstructural applications may require pure metals because of certain physical property advantages, additions of alloying elements are usually made for purposes of enhancing the mechanical properties or other material characteristics (e.g., corrosion resistance) Metal alloys may consist of over ten different elements in specific concentrations with the purpose to optimize a variety of properties Minor alloying additions typically do not alter the basic crystal structure as long as the elements remain in solid solution At sufficiently high concentrations, other phases (either with the same or different crystallographic forms) may precipitate within the base metal (at grain boundaries or in the grain interior) as shown in Fig 3 Phase diagrams are used by metallurgists and materials engineers to understand equilibrium solubility limits in engineering alloys and predict the phases which may form during thermomechanical processing (Ref 2) As will

be discussed later, solid solution elements and precipitates/particles are often used during alloy design to improve the strength of a metal

Metal matrix composites can also be fabricated in which dissimilar constituents (e.g., ceramics and intermetallics) are incorporated into the metallic microstructure in order to enhance mechanical properties The example microstructure in Fig 3 shows the reinforcement material to be dispersed throughout a continuous metallic matrix with the metal representing 50% or greater of the total volume Although the example shows particles as the reinforcement, these materials can be designed with whiskers, short fibers, or long fibers (e.g., rods or filaments) Processing of these composites typically entails thGe incorporation of the reinforcement material into the metal using ingot metallurgy or powder metallurgy techniques (Ref 3)

To the structural engineer, or in the macroscopic view (1×), most metals appear to be continuous, homogeneous, and isotropic Continuity assumes that structures do not contain voids; homogeneity assumes that the microstructure (in views at ~100–1000×) and properties will be identical in all locations; isotropic behavior assumes that the properties are identical in all orientations While these assumptions have been used in continuum mechanics to study the strength of materials and structures under load, engineering materials are often inhomogeneous and anisotropic While it is desirable to minimize such inhomogeneities, it is often impossible to completely eliminate them As discussed above, microstructural evaluation typically shows that