DEFECTS, FRACTURE AND FATIGUE J)efects, Fracture and Fatigue Proceedings of the Second International Symposium, held at Mont Gabriel, Canada, May 30-June 5, 1982 edited by G.C. SIH Institute of Fracture and Solid Mechanics Lehigh University, Bethlehem, Pennsylvania, USA J.W.PROVAN Mechanical Engineering Department McGill University, Montreal, P.Q., Canada 1983 MARTINUS NIJHOFF PUBLISHERS THEHAGUE/BOSTON/LONDON iv Distributors: for the United States and Canada Kluwer Boston, Inc. 190 Old Derby Street Hingham, MA 02043 USA for all other countries Kluwer Academic Publishers Group Distribution Center P.O. Box 322 3300 AH Dordrecht The Netherlands library of Coogress Cataloging in Publication Data International Symposium on Defects, Fracture, and Fatigue (2nd: 1982 : Mont Gabriel, Quebec) Proceedings of Second International Symposium on Defects, Fracture, and Fatigue. 1. Materials--Defects--Congresses. 2. Fracture mechanics--Congresses. 3. Materials--Fatigue- Congresses. I. Sih, G. C. (George C.) II. Provan, J. W. III. Title. IV. Title: Defects, fracture, and fatigue. TA409.I555 1982 620.1'123 82-24576 ISBN·13:978-94-009-6823-3 e-ISBN '13:978-94-009-6821-9 001:10.1007/978-94-009-6821-9 Copyright © 1983 by Martinus Nifhoff Publishers, The Hague. Softcover reprint of the hardcover 1st edition 1983 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher, Martinus Nifhoff Publishers, P.O. Box 566, 2501 CN The Hague, The Netherlands. CONTENTS PREFACE by G. C. Sih and J. W. Provan ix GENERAL REMARKS by G. C. Sih xi NIGHTMARE by A. C. Eringen xiii SYMPOSIUM PHOTOGRAPHS xv SECTION I DISLOCATION BEHAVIOR AND INFLUENCE Direct observations of crack tip dislocation behavior during tensile and cyclic deformation 3 by S. t4. Ohr, J. A. Horton and S.-J. Chang The behavior of dislocations and the formation of wall structures observed by in situ high voltage electron microscopy 17 by T. Imura and A. Yamamoto Dislocation dynamics in aluminum and in aluminum-based alloys investigated by TEM and NMR techniques 23 by J. Th. M. De Hosson, W. H. M. Alsem, H. Tamler and o. Kanert The cyclic deformation of titanium: dislocation substructures and ef- fective and internal stresses 37 by L. Handfield and J. I. Dickson Fatigue softening in precipitation hardened copper-cobalt single crystals by D. Steiner and V. Gerold 53 SECTION II MODELING OF DISLOCATIONS AND MICROCRACKING The elastic strain energy of dislocation structures in fatigued metals 65 by T. Mura, H. Shirai and J. R. Weertman Dislocation kinetics and the formation of deformation bands 75 by E. C. Aifantis Intergranular fracture criteria and interfacial thermodynamic properties by O. A. Bamiro 85 Statistical mechanics of early growth of fatigue cracks 99 by W. J. Pardee, W. L. Morris, B. N. Cox and B. D. Hughes The effect of homo- and heterogeneous mechanisms coupling on microcrack nucleation in metals 113 by J. Krzeminski SECTION III SLIP-BANDS AND CRACK INITIATION A model of high-cycle fatigue-crack initiation at grain boundaries by persistent slip bands by H. Mughrabi 139 vi Shape and structure of persistent slip bands in iron carbon alloys 147 by K. Pohl, P. Mayr and E. Macherauch Estimation of crack initiation in plain carbon steels by thermometric methods 161 by H. Harig and M. Weber Inhomogeneous work-softening during cyclic loading of SAE 4140 in dif- ferent heat treated states 171 by D. Eifler and E. Macherauch Fatigue crack initiation in iron 183 by C. V. Cooper and M. E. Fine The cyclic response and strain life behaviour of polycrystalline copper and a-brass 195 by N. Marchand, J.-P. Bailon and J. I. Dickson SECTION IV MATERIAL DAMAGE AND FRACTURE Prediction of damage sites ahead of a moving heat source 211 by M. Matczynski and G. C. Sih A pseudo-linear analysis of yielding and crack growth: strain energy den- sity criterion 223 by G. C. Sih and P. Matic Nonlocal mechanics of crack curving 233 by A. C. Eringen and A. Suresh Motion of the crack under constant loading and at high constant tempera- ture 243 by A. Neimitz Creep cavitation and fracture due to a stress concentration in 2~ Cr-l Mo 259 by T.-S. Liu, T. J. Delph and R. J. Fields SECTION V STRESS AND FAILURE ANALYSIS Stress intensity factors for radial cracks in bimaterial media 273 by O. Aksogan Sudden twisting of partially bonded cylindrical rods 285 by M. K. Kassir and K. K. Bandyopadhyay An axisymmetric-elastodynamic analysis of a crack in orthotropicmedia usinq a path-independent integral 299 by D. A. Scarth, T. R. Hsu and G. S. Pizey Unstable growth of branched cracks 311 by E. E. Gdoutos Experimental stress intensity distributions by optical methods 325 by C. W. Smith and G. Nicoletto SECTION VI FATIGUE CRACK PROPAGATION Analyses of microstructural and chemical effects on fatigue crack growth 339 by H. W. Liu A fractographic study of corrosion-fatigue crack propagation in a duplex stainless steel 359 by M. Ait Bassidi, J. Masounave, J.-P. Bailon and J. I. Dickson Effects of environment on fatigue deformation of iron 373 by D. Majumdar and Y.-W. Chung Microstructural processes prior to and during fatigue softening of struc- tural steels 385 by H. Veith vii SECTION VII STATISTICAL FRACTURE AND FATIGUE On a predictive fatigue crack initiation reliability for large steel castings 399 by U. S. Chawla, Y. Carmel, P. H. B. Hamilton and J. W. Provan Reliability of structures with time dependent properties 409 by G. F. Oswald and G. I. Schu~ller An experimental investigation of fatigue reliability laws 423 by J. W. Provan and Y. Theriault SECTION VIII FRACTURE TESTING AND CONTROL On cracking instability in plates containing circular holes 435 by C. L. Chow Effect of inclusions on dynamic toughness of line-pipe steel 447 by W. R. Tyson, J. D. Boyd and J. T. McGrath Discontinuity sources in manufacturing processes 459 by H. J. Mcqueen A stochastic interpretation of material degradation processes 473 by E. S. Rodriguez III, D. R. Hay and J. W. Provan LIST OF PARTICIPANTS 487 PREFACE The Second International Symposium on Defects, Fracture and Fatigue took place at Mont Gabriel, Quebec, Canada, May 30 to June 5, 1982, and was organized by the Mechanical Engineering Department of McGill University and Institute of Fracture and Solid Mechanics, Lehigh University. The Co-Chairmen of the Sympo sium were Professor G. C. Sih of Lehigh University and Professor J. W. Provan of McGill University. Among those who served on the Organizing Committee were G. C. Sih (Co-Chairman), J. W. Provan (Co-Chairman), H. Mughrabi, H. Zorski, R. Bullough, M. Matczynski, G. Barenblatt and G. Caglioti. As a result of the interest expressed at the First Symposium that was held in October 1980, in Po land, the need for a follow-up meeting to further explore the phenomena of mate rial damage became apparent. Among the areas considered were dislocations, per sistent-slip-bands, void creation, microcracking, microstructure effects, micro/ macro fracture mechanics, ductile fracture criteria, fatigue crack initiation and propagation, stress and failure analysis, deterministic and statistical crack models, and fracture control. This wide spectrum of topics attracted researchers and engineers in solid state physics, continuum mechanics, applied mathematics, metallurgy and fracture mechanics from many different countries. This spectrum is also indicative of the interdisciplinary character of material damage that must be addressed at the atomic, microscopic and macroscopic scale level. Mont Gabriel, si~ated just 39 miles north of Montreal, provided an ideal en vironment for a small group of specialists to gather and interact on a personal basis. Intense discussions between the physical metallurgists and fracture mech anicians are necessary for reconciliating the details of the microstructure with the assumed continua of the computational methods and toughness assessment tech niques. Both groups benefited and developed a wider appreciation of the differ ence in viewpoints. A unification of concepts, however, can only be accomplished if effective communications are maintained continuously among researchers and en gineers. To this end, the Organizing Committee has agreed to hold a third Sympo sium two years from now in Europe. The Co-Chairmen wish to take this opportunity to thank the Canadian Commit tee for Research on the Strength and Fracture of Materials for supporting the Symposium and those who have contributed towards the success of the meeting. In particular, Mrs. Evelyn Schliecker of McGill University should be recognized for her attendance at the registration desk and for taking care of many arrange ments. The efforts of Messrs. Louis Archard and Yves Theriault are also appre ciated for providing local transportation. x Finally, the credit for retyping all the manuscripts goes to Mrs. Barbara DeLazaro and Mrs. Constance Weaver of the Institute of Fracture and Solid Mechan ics at Lehigh University. Their quality of work is evidenced in this book. Mont Gabriel, Canada G. C. Sih June 1982 J. W. Provan Co-Chairmen GENERAL REMARKS The theme of this Symposium follows a long standing notion that material failure initiates from defects. Perhaps, the ancient Chinese transcript "Mo Ching" in the -4th Century has said it all: It ~ upon evenne6~ o~ continuity that b~eaking o~ not-b~eaking depend. Let a wught hang on hOviJr.. The hOvi.Jt w.LU b~ea.k beca.~e U ~ not ~ui.y even o~ cont-LnuoM. I6 U w~e, U woui.d not b~ea.k. In recent times, much effort has been made to identify movement of imperfec tions at the earliest possible stage and to follow their growth in details. The results unavoidably have tended to be qualitative and expressed in terms of mi croscopic entities and their interactions such as dislocations, inclusions, slip-bands, grain boundary cracking, environmental effects, etc. This is mainly because of the difficulties associated with constructing a quantitative theory that can consistently assess material damage at the different scale levels rang- ing from the atomic, say 10-8 cm in linear dimension, to the macroscopic, say 10-2 cm. This involves at least six orders of magnitude or more. While the electron microscope has enabled a detailed description of the sequence of events which culminate in material damage, the mathematical models still lag far behind not being able to express the microscopic variables in terms of useful macroscop ic parameters. It is precisely due to this lack of interaction between the phys ical metallurgists and fracture mechanicians that this Symposium has been organ ized to reconcile the intricate details of the microstructure with the assumed mechanics of continua and computational methods. Major difficulties still perplex the practitioners who attempt to estimate fatigue lives of structural components with or without the added complexities of hostile environments. Judgement and experience must often be exercised to provide provision against premature failure. The discipline of fracture mechan ics, however, has provided a drastic improvement over the conventional methods that do not account for the presence of initial defects. Learning to design with defects or cracks is the key for making prediction with increased accuracy. Undoubtedly, consistent description of the qualitative observations can further improve the agreement of theory and experiment. Material damage at the atomic, microscopic and macroscopic scale level needs to be related mathematically in a unifi ed manner. xii Another important objective of this Symposium is its international character that encourages a closer cooperation among the researchers and engineers from different nations. This joint effort to develop better concepts and methods in design concerning with failure prevention should always be kept in mind when organizing future meetings. Mont Gabriel G. c. Sih June 1982 Lehigh University