Other Pergamon Titles of Interest BEE Materials Engineering CHEN Mechanics and Design of Cam Mechanisms INSTITUTION OF CHEMICAL ENGINEERS User Guide on Process Integration for the Efficient Use of Energy McQUEEN eta/ Strength of Metals and Alloys (in 3 Volumes) NIKU-LARI Advances in Surface Treatments, Volumes 1 & 2 OSGOOD Fatigue Design, 2nd Edition SMITH Fatigue Crack Growth TAIT & GARRETT Fracture and Fracture Mechanics VALLURI Advances in Fracture Research (in 6 Volumes) Pergamon Related Journals Free sample copy gladly sent on request Automatica Computers & Industrial Engineering Computers & Operations Research Engineering Fracture Mechanics Fracture & Fatigue of Engineering Materials & Structures International Journal of Engineering Science International Journal of Impact Engineering International Journal of Machine Tool Design & Research International Journal of Mechanical Sciences Mechanism and Machine Theory Robotics & Computer Integrated Manufacturing CURRENT ADVANCES IN MECHANICAL DESIGN AND PRODUCTION III Proceedings of the Third Cairo University MDP Conference, Cairo, 28-30 December 1985 Edited by S. E. A. BAYOUMI Conference Chairman, Professor, Mechanical Design and Production Department, Cairo University, Cairo, Egypt and M. Y. A. YOUNAN General Secretary and Editor-in-Chief, Associate Professor, Mechanical Design and Production Department, Cairo University, Cairo, Egypt PERGAMON PRESS OXFORD · NEW YORK · TORONTO · SYDNEY · FRANKFURT U.K. Pergamon Press Ltd., Headington Hill Hall, Oxford 0X3 OBW, England U.S.A. Pergamon Press Inc., Maxwell House, Fairview Park, Elmsford, New York 10523, U.S.A. CANADA Pergamon Press Canada Ltd., Suite 104, 150 Consumers Road, Willowdale, Ontario M2J 1P9, Canada AUSTRALIA Pergamon Press (Aust.) Pty. Ltd., P.O. Box 544, Potts Point, N.S.W. 2011, Australia FEDERAL REPUBLIC Pergamon Press GmbH, Hammerweg 6, OF GERMANY D-6242 Kronberg, Federal Republic of Germany JAPAN Pergamon Press Ltd., 8th Floor, Matsuoka Central Building, 1-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160, Japan BRAZIL Pergamon Editora Ltda., Rua Eca de Queiros, 346, CEP 04011, Säo Paulo, Brazil PEOPLE'S REPUBLIC Pergamon Press, Qianmen Hotel, Beijing, OF CHINA People's Republic of China Copyright © 1986 Pergamon Press Ltd. All Rights Reserved. No part of this publication may be re- produced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise, without permission in writing from the publishers. First edition 1986 ISBN 0 08 033440 7 (Hardcover) ISBN 0 08 033441 5 (Flexicover) In order to make this volume available as economically and as rapidly as possible the authors' typescripts have been re- produced in their original forms. This method unfortunately has its typographical limitations but it is hoped that they in no way distract the reader. Printed in Great Britain by A. Wheaton & Co. Ltd.., Exeter PREFACE This volume presents 52 selected papers submitted to the Third Cairo University Conference on Mechanical Design and Production (MDP-3) held in Cairo during the period December 28-30, 1985. Following the first conference (MDP-1) held in 1979 and the second conference (MDP-2) held in 1982, this conference was intended to highlight the current advances in Mechanical Design and Production to help in the dissemination of the latest developments in the disciplines related to the subject by academic and industrial institutions. Several distinguished scientists were invited to address the conference in their fields. Their lectures are included in this volume. The selected papers were received from various countries namely, Egypt, U.S.A., U.K., W. Germany, France, Italy, Austria, Romania, China, Nigeria, Saudi Arabia, Kuwait and Qatar. The papers have been grouped as follows: 1. Fail-safe and stress analysis: Stress analysis measurements, fracture mechanics, creep and creep rupture, fatigue and ratchetting. 2. Dynamic analysis and control: Dynamics of vehicles, mechanisms and robotic manipulators and analysis of control systems and components. 3. Vibrations: Vibration analysis in components and structures, noise and vibration isolation. 4. Materials technology: Developments in ferrous and aluminium alloys and composite materials. 5. Manufacturing technology and productivity: Metal forming, machining, casting, welding, group technology and productivity. 6. Computer aided analysis of manufacturing processes: Application to metal forming, machining, casting and welding. We would like to acknowledge the generous efforts of the staff of the Mechanical Design and Production Department of Cairo University who undertook the conference organizational activities. We would also like to acknowledge the financial contributions of various Egyptian and international industrial and academic institutions. The financial assistance of the US AID, the British Council and the German Council (DAAD) for covering the expenses of the invited keynote speakers is gratefully acknowledged. We hope this volume will be helpful to researchers and engineers working in the area of Mechanical Design and Production in industrial and academic institutions. Prof. Salah E.A. Bayoumi Dr. Mäher Y.A. Younan v EDITORIAL COMMITTEE Mäher Y.A. Younan E d i t o r - i n - c h i e f Mohamed K. Bedawy Ahmed M.A.Mansour A s s i s t a n t e d i t o r Said M. Megahed Mokhtar O.A.Mokhtar Ibrahim N. Ibrahim SCIENTIFIC COMMITTEE Akeel, A.H. U.S.A. Engler, S. W. Germany Avitzur, B. U.S.A Farag, M. Egypt Arafa, H.A. Egypt Fawzi, I. Egypt Badawy, E.M. Egypt Hassan, M.F. Egypt Bayoumi, S.E.A. Egypt Kamal El-Din, H. Egypt Bily, M. Czechoslovakia Kanninen, M.F. U.S.A. Daoud, R.H. Egypt Khalil, T. U.S.A. Dorn, L. W.Germany Mirza, S. Canada Dowson, D. England Pedersen, P. Denmark El-Ashram, A.E. Egypt Petersen, J. W. Germany El Gomayel, J. U.S.A. Reissmann, H. U.S.A. El-Mehairy, A.E. Egypt Riad, S. Egypt El-Rifai, M.A. Egypt Rifai, M.A. Egypt El-Sabbagh, A.S. Egypt Zienkiewicz, O.C. England El-Salamoni, M.A. Egypt VI EDITORIAL COMMITTEE Mäher Y.A. Younan E d i t o r - i n - c h i e f Mohamed K. Bedawy Ahmed M.A.Mansour A s s i s t a n t e d i t o r Said M. Megahed Mokhtar O.A.Mokhtar Ibrahim N. Ibrahim SCIENTIFIC COMMITTEE Akeel, A.H. U.S.A. Engler, S. W. Germany Avitzur, B. U.S.A Farag, M. Egypt Arafa, H.A. Egypt Fawzi, I. Egypt Badawy, E.M. Egypt Hassan, M.F. Egypt Bayoumi, S.E.A. Egypt Kamal El-Din, H. Egypt Bily, M. Czechoslovakia Kanninen, M.F. U.S.A. Daoud, R.H. Egypt Khalil, T. U.S.A. Dorn, L. W.Germany Mirza, S. Canada Dowson, D. England Pedersen, P. Denmark El-Ashram, A.E. Egypt Petersen, J. W. Germany El Gomayel, J. U.S.A. Reissmann, H. U.S.A. El-Mehairy, A.E. Egypt Riad, S. Egypt El-Rifai, M.A. Egypt Rifai, M.A. Egypt El-Sabbagh, A.S. Egypt Zienkiewicz, O.C. England El-Salamoni, M.A. Egypt VI EXECUTIVE COMMITTEES Members of the Mechanical Design and Production Department, Cairo University: Professors: Arafa H.A. Megahed M.M. (on leave) Bayoumi S.E.A. Mostafa A.A.F. EL-Araby, M. (on leave) Radwan M.A.E. EL-Salamoni M.A. Dept.Chairman Ragab M.S. Fawzi I. Riad M.S.M. Hassan M.F. Said M.E. Xabil Y. Salama A.S. Kandeel S.E. Wifi A.S. (on leave) Metwally S. (on leave) Younan M.Y.A. Mokhtar M.O.A. Radwan A.A. Ragab A.R. Assistant Professors: (on leave) Riad S.M. Basily B.B. Shawky G. (on leave) El-Zoghby A.A.A. Hassan M.E. Ibrahim I.N. Associate Professors: Kamal M.I. Bahgat B.M. Khattab A.A.M. Basyouny F. (on leave) Mansour A.M. Bedewy M.K. Mawsouf N.M. El-Dalil S.A. Megahed S.M. Eleiche A.M. (on leave) Mohamed M.A.A. El-Hebeiry M.R. Salama M.S. El-Sawy A. Shalaby M.A. (on leave) El-Sherbiny M. (on leave) Shash Y. Hassan G.A. (on leave) So.i iman F.A. Kassem S.A. Yacout S.M. Khourshid S. Zeid O.A. Kouta F. Current Advances in Mechanical Design & Production> Third Cairo University MDP Conference, Cairo, dec. 28-30 1986. FRACTURE AS A DESIGN CRITERION* M.F. KANNINEN Institute Scientist,Southwest Research Institute, San Antonio U.S.A. AbblkAC'i. Demands on material performance are continually increasing, while, at the same time, the capabilities for flaw detection are improving. As a consequence, fracture mechanics, the technology that can be used for the assessment of the strength and durability of structural components with crack-like flaws, has become an accepted part of engineering design. This paper outlines the basis for the use of linear elastic fracture mechanics and outlines its application to a broad range of engineering problems. Examples are given to illustrate the similarity between fracture mechanics structural applications and ordinary engineering design calculations. The limitations of the linear elastic approach are discussed to illustrate the need for the on-going research in the subject. KEYWORDS fracture, fracture mechanics, linear elastic fracture mechanics, dynamic fracture mechanics, structural integrity, crack propagation, crack arrest, pressure vessels, leak-before-break condition, cost of fracture INTRODUCTION Engineers and others concerned with structural integrity need look no further than their daily newspaper for reasons to become interested in the subject of fracture mechanics. For example, the New York Times of 1 September 1985 reported on four separate fracture-related industrial problems: a lethal gas leak from a chemical plant storage tank, municipal bus undercarriage cracking, a train derailment, and jet engine combustion chamber cracking. In the same edition was a further story on the possible use of cryofracture to dispose of obsolete chemical weapons. This was not a particularly unusual issue. Widely reported earlier this year have been cracking incidents associated with nuclear plant piping and pressure vessels, gas transmission pipelines, ship structures, and many others. In the realm of fiction, the plot in a currently popular novel hinges on three separate fracture incidents involving, respectively, a valve in a nuclear submarine power plant, a helicopter transmission casing, and a submarine hull [1]. Nevertheless, in this context, the year of this conference will likely be remembered for other incidents. *lnvited Keynote Lecture 3 4 M.Kanninen Within the first eight months of 1985, five major aircraft disasters have occurred, making this year already one of the worst in the history of aviation. While the causes of these accidents have not been established at the time of this writing, it seems likely that cracking played a significant role in at least some of them. This is rather ironic in that the development of fracture mechanics - the engineering discipline that bears on the assessment of structural components containing cracks - was largely motivated by aerospace applications. Indeed, the most widely used aspect of the subject - linear elastic fracture mechanics (LEFM) - is most applicable to the high strength materials used in aerospace and other transportation-related structures. It would be difficult to determine whether the best available fracture mechanics technology could have prevented any of the tragic aircraft accidents that have occurred within this year. The application of fracture mechanics technology is subject to a number of constraints: limited knowledge of (1) the crack growth resistance properties of the material, (2) the appropriate quantitative crack driving force representation, and (3) the location and size of a crack in a structural component. That fractures occur in service should not therefore be taken as a reflection of the inadequacy of existing fracture mechanics technology. What is clearly true is that ever increasing demands on materials and structural performance that give rise to designs with lower margins of safety and inadequate inspectability are simply making applications of fracture mechanics much more acute. This is true not only in the transportation industry where weight savings are crucial, but also in a wide variety of other engineering applications where they are not. As but one instance that can be taken from the current technical literature, the Engineering News Record recently reported on the catastrophic fracture of a large diameter, stainless steel, high-pressure steam line [2]. The fracture, which apparently initiated from a weld flaw that possibly enlarged by fatigue and/or corrosion to a critical size, propagated rapidly in a longitudinal weld for more than 5 meters. The resulting steam release and explosion killed four men and seriously burned another ten. What is of most technical significance in this instance, just as in the myriad of other examples where fracture has caused extensive loss of lives and property, is not that an undetected flaw existed in the pipe to trigger a fracture. No engineering structure is likely to be flaw free. The appropriate design approach therefore is one that recognizes the possibility that near- critical sized cracks are either present in a structural component when it is put into service, or that these can so readily develop during operation. It is fracture mechanics technology that makes it possible to obtain quantitative assessments of such possibilities. Recognizing that fracture mechanics has a key role to play in engineering design, the objectives of this paper are first to introduce fracture mechanics to those not previously acquainted with it and, second, to describe the wide applicability of the subject for others. This account draws upon the recently published book Advanced Fracture Mechanics, by M.F. Kanninen and C.H. Popelar [3], to which the reader is directed for further information and references. CURRENT FRACTURE MECHANICS AND ITS APPLICATIONS Kanninen and Popelar [3] offer a formal definition of fracture mechanics, as follows: Fracture mechanics is an engineering discipline that quantifies the conditions under which a load-bearing solid body can fail due to the enlargement of a dominant crack contained in that body. M.Kanninen 5 Thus, fracture mechanics draws upon the disciplines of applied mechanics, materials science, and nondestructive evaluation (NDE). It is usually applied to relate the maximum permissible applied loads acting upon a structural component to the size and location of a crack, either real or hypothetical, in that component. But, it can also be used to predict the rate at which a crack can approach a critical size in fatigue and/or by environmental influences. Following initiation, fracture mechanics technology can be used to determine the conditions in which a rapidly propagating crack can be arrested. Current procedures make most effective use of these capabilities for materials that otherwise behave in an essentially linear elastic manner. Accordingly, it will be appropriate for the purposes of this paper to concentrate on linear elastic fracture mechanics and its applications. Basis of Linear Elastic Fracture Mechanics There are three general ways in which a flaw can appear in a structure. These are, (1) inherent defects that occur in the material (e.g., inclusions in a metal, debonded regions in a composite), (2) defects introduced during the fabrication of a structural component (e.g., lack of fusion in a weld, welding arc strikes), and (3) damage incurred during the service life of the component (e.g., dents and cuts from mechanical impact, fatigue and environmentally assisted cracking). Within the confines of linear elastic fracture mechanics, it makes no difference how a flaw is introduced. A crack-like flaw of a given size and position in a body is assumed to obey the same fracture rules regardless of its origins. The basic capability that fracture mechanics provides is commonly employed in either of two general ways. First, the maximum safe operating loads that an engineering structure can sustain for the sizes and locations of existing flaws can be determined. Such cracks might be those actually found during an inspection, whereupon the continued safe operation of the structure is in question. Second, for given loads, the largest crack size that can exist without fracture can be determined. This will provide specifications to be set in advance of an inspection. Like all fracture mechanics approaches, LEFM relates the size of a crack with the loading that will fracture a given component by linking two separate activities: (1) a mathematical stress analysis of the loaded structure, and (2) experimental measurements of the material's fracture properties. Expressed in quantitative terms, fracture will occur when K(a,D,G) = Kc(T,i,B) (1) where K is a calculated parameter that, as indicated in eq.(1), depends on crack size a, component dimensions D, and applied stress σ. It will not depend on the material. In contrast, K is a material property known as the fracture toughness that depends on the temperature at the crack tip T, the rate of loading σ, and the thickness of the cracked section B. It is an experimentally measured quantity that is independent of the crack/structure geometry, the loading imposed on the structure, and the crack size. It is particularly important to understand that, in order to perform a fracture mechanics assessment, both K and KQ are needed: neither parameter is meaningful by itself. In this, there is a clear analogy to ordinary structural design this is amplified in the following section of this paper. Of most importance in regard to linear elastic fracture mechanics are applications where weight is a primary concern. When the resistance to yielding is high (e.g., in a high strength steel), the fracture toughness tends to be