Impact Wear of Material PDF
Preview Impact Wear of Material
TRlBOLOGY SERIES Advisory Editor: DOUGLAS SCOTT Editorial Board W.J. Bartz (Germany. B.D.R.) I.V. Kragelskii (U.S.S.R.) C.A. Brockley (Canada) K.C. Ludema (U.S.A.) E. Capone (Italy) A.J.W. Moore (Australia) H. Czichos (Germany, B.D.R.) G.W. Rowe (Gt. Britain) W.A. Glaeser (U.S.A.) T. Sakurai (Japan) M. Godet (France) J.P. Sharma (India) H.E. Hintermann (Switzerland) - Vol. 1 Tribology a systems approach to the science and technology of friction, lubrication and wear (Czichos) Vol. 2 Impact Wear of Materials (Engel) TRIBOLOGY SERIES, 2 IMPACT WEAR MATERIALS PETER A. ENGEL IBM System Products Division, Endicott, N. Y., U.S.A. ELSEVIER SCIENTIFIC PUBLISHING COMPANY - - AMSTERDAM OXFORD NEW YORK 1978 ELSEVIER SCIENTIFIC PUBLISHING COMPANY 335 Jan van Galenstraat P.O. Box 211, 1000 AE Amsterdam, The Netherlands Distributors for the United States and Canada: ELSEVIERINORTH-HOLLAND INC. 52, Vanderbilt Avenue New York, N.Y. 10017 First edition 1976 Second impression (with amendments) 1978 230 figures Librar) of Congress Cataloging in Publication Data Engel, Peter A Impact wear of materials. - Includes biblioara-p hical references and indexes. 1, blaterials--3ynanic testing. 2" Iqact. I. Title, ~~418.34~5. 621.8'9 76 -44871 ISBN 0-444-41533 -5 ISBN: 0-444-41533-(5V ol. 2) ISBN: 0-444-41677-(3S eries) @ Elsevier Scientific Publishing Company, 1978 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, electronic, mechanical, photocopy- ing, recording or otherwise, without the prior written permission of the publisher, Elsevier Scientific Publishing Company, P.O. Box 330, 1000 AH Amsterdam, The Netherlands Printed in The Netherlands PREFACE The inspiration to write this book essentially grew out of the author's experience with engineering problems pertaining to impacting machine components. lmpact wear, i.e. the wear resulting from repetitive impact cycles in machinery, is often a limiting factor of service life; its importance is accentuated in modern industrial applications where high-strength materials are called upon to endure a large number of load cycles under high local (contact) stress. These loads induce wear modes which are character- istic of the process of contacting, and thus traditional wear tests would not suffice to evaluate competing designs. Because impact wear has become a significant factor and prior textbooks hod traditionally treated sliding and, to an extent, rolling as the main source of mechanical wear in machinery, this first book devoted to impact wear is hoped to fulfill a vital mission, Following the conception of this book, the author has continued and widened his research activities, and diligently studied the literature of tribology; the latter indicates rapid progress in a field where important discoveries are becoming more frequent. In writing this text, the author was concerned to highlight a hitherto neglected area of wear, and also to give expression to a compact philosophy that considers wear as a geometric phenomenon dependent an the contact stresses and wear mechanisms. Wear phenomena due to erosion and percussion are considered under the unified title of lmpact Wear. Erosion is defined as the action of streams and jets of solid ' particles or liquids, and percussion refers to the impacts of solid bodies of more sub- stantial size, The unification of erosion and percussion appears justified because the common features of impact stress analysis are in abundance despite the fact that wear mechanisms tend to be distinct and characteristic of a particular impact wear process. The studies, beginning in the 1950'~o~f materials eroded by solid particles and liquids have followed distinct patterns in their development. An effort has been made in this text to reconstruct a sense of this historic development within those studies. lmpact wear caused by percussion is a newer topic and this is the area of the author's principal research contributions. Consequently, there is an attempt to show the relationship between the analytical-experimental apparatus used in percussive impact versus sliding and rolling work. The general intent of this book is an analytical-predictive formulation of various cases involving impact wear. New results in erosion theory permit the possibility of quantifying the wear rates that are dependent on a few principal parameters. For per- cussive impact wear, a generalized engineering theory emerged from the author's research, and it centers around the master-curve shifting procedure detailed in this text, An experimental foundation to the analytical results is provided throughout the work, The following considerations enter into each quantitative application: (1) Impact analysis, (2) Identification of material behavior and wear mechanisms, (3) Considerations of the wear geometry, (4) The aspect of surface properties and behavior. The emphasis of this book is on conceptual models and a rational treatment, in- stead of sophisticated mathematical or physico-chemical presentation. It is hoped that this approach will be of benefit to researchers and engineers, and specifically, to machine designers, and will stimulate further investigation at colleges, universities, and research institutions. When used in university courses, this text corresponds to the level of a senior undergraduate or first-year graduate course in engineering and the natural sciences. The organization of the material was designed to enhance an interdisciplinary attitude to the subject matter by engineers, physicists, and chemists working in various special- ized fields,, Therefore an appropriate introduction is provided to prepare the reader for each key aspect of impact wear. Chapter 1 reviews the basic issues of tribology. Chapter 2 discusses impact (and, in general, contact) theory; modern computational techniques such as the finite element method are shown. Chapter 3 is devoted to the various aspects of a single impact on engineering surfaces; layered surfaces, plastically deformed materials, viscoelasticity and lubrication are discussed for their role on impact. An introduction to osperity- models focuses on the "microscopic" elements of contact, the synthesis of which being the "macroscopic" (apparent, Hertzian) contact. Repetitive impact effects are involved inasmuch as heat generation is involved. Ductile cutting and brittle fracture by small erosive particles is described in Chapter 4. Some successful semi-empirical theories combining wear by the ductile and brittle aspects of the material are presented. Chapter 5 treats some of the latest in- vestigations in erosive wear, including the effect of particle fragmentation; single- / particle studies have explained several aspects of erosion dependence an velocity, angle of incidence, etc. Chapter 6 introduces the experimental techniques and various phenomena arising in percussive impact wear; some test apparatuses are described, along with test goals. Chapter 7 is devoted to the initiation of wear and the "zero wear theory" by which it can be predicted based on an engineering description of the materials and loads involved. Chapter 8 starts with the optimal wear-path principle, and combining this with the wear mechanism, laws are derived for the continuous wear process in different geometric configurations. The master-curve shifting process facilitates a rapid estimation of the effects of varying the impact- and sliding velocities, surface roughness, lubrication and other engineering parameters. In Chapter 9, the analytical techniques are extended to contacts loaded .into the plastic range, after reviewing numerous experimental results. Percussive wear of metal vs, nonmetal configurations is treated in Chapter 10; the wear of print-devices and metal vs. polymer pairs is discussed. The erosion of liquid jets is treated in Chapter 11; impact stress analysis and damage due to single impacts is followed by fatigue considerations for multiple hits. The author has been, for many years, principal investigator of impact wear work in the Materials and EngFneering Analyses Section at the IBM Laboratory in Endicott, N. Y. He thanks his management for encouraging the research project and the publica- tion of this work. The thoughtful comments of G. P. Tilly helped shape the final con- tents of the manuscript. The remarks of E. Sacher and M. B. Peterson are greatly appreciated. The interest and helpful attitude of many colleagues at IBM and of the worldwide scientific community are gratefully acknowledged. A special note of admira- tion is due to the researchers of Cambridge University who pioneered in the study of erosion. The author also wishes to thank all workers in the field and their publishers, who consented to lending data and diagrams quoted in this text. The skeleton of this book was born in courses given at IBM and at the School of Advanced Technology, State University of New York at Binghamton. Every student is warmly remembered for his help in crystallizing the material, The author extends his grateful appreciation to Josie Scanlon for producing an excellent manuscript in the form of camera-ready copy. Finally, the author's wife deserves high praise for her patience and cheerful support during the years of work. Binghamton, N.Y. July, 1976 BORROWED ILLUSTRATIONS The author is grateful for the permission granted by publishers of several books and journals to reproduce material in this text. The publications that are quoted include the following: Technical books published by Edward Arnold, London; Pergamon Press Ltd., Oxford; Oxford University Press, Oxford; Wiley and Sons, New York. Journal articles: ASLE Transactions Amer. Soc. of Lubrication Engineers, Park Ridge, ll linois ASME Transactions Amer. Soc. of Mechanical Engineers, Journal of Applied Mechanics New York, N.Y. Journal of Basic Engineering Journal of Engineering for Industry Journal of Lubrication Technology Comptes Rendus de I'Academie des Sciences Centrale des Revues Dunod-Gauthier- Vil lars, Paris Experimental Mechanics Society of Experimental Stress Analysis, Bridgeport, Connecticut IBM Journal of Research and Development IBM Corporation, Armonk, N. Y. International Journal of Mechanics and Pergamon Press Ltd., Oxford Physics of Sol ids International Journal of Solids and Structures Pergamon Press Ltd., Oxford International Journal of Numerical Wiley and Sons, New York Methods in Engineering Journal of Applied Physics Amer. lnsti tute of Physics, New York Journal of Macromolecular Science, Marcel Dekker Journals, New York Reviews in Macromolecular Chemistry Journal of Materials Amer. Soc. of Testing Materials, Philadelphia, Pa. Journal of Research of the National U. S. Department of Commerce, Bureau of Standards Washington, D.C. Metals Engineering Quarter1y Amer. Soc. for Metals, Metals Park, Ohio Proceedings and Philosophical Oxford University Press, Oxford Transactions of the Royal Society of London Wear Elsevier Sequoia, Lausanne NOMENCLATURE Symbols which are only used locally are not listed here. A Area A, Real area of contact a Contact radius for spherical contact; major axis of contact ellipse aT(T) Viscoelastic shift factor B Bulkmodulus b Half-length of cor\tact, for cylindrical contact; minor axis of contact ellipse C Constraint factor; stress severity factor C Specific heat c Velocity exponent in erosion; sound velocity; clearance c Phase velocity D Ductility; contact diameter; erosion resistance; damage d Indenter diameter; distance; particle size (diameter); jet diameter E Modulus of elasticity E, Reduced modulus of elasticity, [ ((1 - vl2 )/"El) + ((1 - v22 )/rE 2)1 -1 E* Complex modulus e Coefficient of restitution F Friction force f Slip factor, vibration frequency G Shear modulus H Oil film thickness; layer thickness; hardness h Depth of wear I Moment of inertia; erosion intensity J Impulse J1,2,3 Invariants of the stress deviator tensor K Wear constant; stiffness matrix; thermal conductivity k Spring constant L Span length M Bending moment; mass m Mass N Impulse; number of cycles n Impact repetition rate Normal contact force Linear normal force per unit width Flow pressure; hardness; fluid pressure Heat; volume; failure parameter Contact pressure Volumetric heat generation Radius of curvature; roundness Reynolds number Sliding pass-length; sheor force; shape factor; impact strength Radius of wear crater; percentage of weight undersize for erosive particle sample Temperature; modulus of toughness; tension Time Contact time (duration) Slipping time during impact Energy Velocity; radial surface displacement Impact velocity Tangential (sliding) velocity Volume (or mass) of wear (Elastic) displacement; width of cylindrical indenter SI ip Sliding distance In subscript, denotes yield Contact approach; pressure-viscosity constant; angle of attack Combined curvature; surface damage contribution factor; rake angle Y Wear factor A Logarithmic decrement 6 Peak-t~-~eosku rface finish tan 6 Viscoelastic dissipation factor Strain; deformation wear factor; energy Nondimensional curvature parameter Viscosity; asperity density Angle; rotation Thermal diffusivity Nondimensional curvature parameter for wearing plane Coefficient of friction Poisson's ratio Mass density; nondimensional curvature parameter for wearing round body Normal stress; contact pressure; standard deviation of asperity heights Shear stress impact frequency; cutting Weor factor ; primary erosion factor Probability distribution Contact force ratio, P/F; optical reflection coefficient Angle between principal planes of contacting bodies; plasticity index; secondary erosion factor Angular speed
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