FATIGUE CRACK GROWTH UNDER SPECTRUM LOADS

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2 FATIGUE CRACK GROWTH UNDER SPECTRUM LOADS A symposium presented at the Seventy-eighth Annual Meeting AMERICAN SOCIETY FOR TESTING AND MATERIALS Montreal, Canada, June 1975 ASTM SPECIAL TECHNICAL PUBLICATION 595 R. P. Wei and R. I. Stephens symposium cochairmen List price $ AMERICAN SOCIETY FOR TESTING AND MATERIALS 1916 Race Street, Philadelphia, Pa

3 9 AMERICAN SOCIETY FOR TESTING AND MATERIALS 1976 Library of Congress Catalog Card Number: NOTE The Society is not responsible, as a body, for the statements and opinions advanced in this publication. Printed in Tallahassee, Fla. May 1976

4 Foreword The Symposium on Fatigue Crack Growth Under Spectrum Loads was held on June 1975 at the Seventy-eighth Annual Meeting of the American Society for Testing and Materials in Montreal, Quebec, Canada. Committee E-24 on Fracture Testing of Metals and Committee E-9 on Fatigue sponsored the symposium. R. P. Wei, Lehigh University, and R. I. Stephens, The University of Iowa, served as the symposium cochairmen. Serving as members of the Symposium Organizing/Program Committee and as session chairmen were J.M. Barsom, U. S. Steel Corp.; W. G. Clark, Jr., Westinghouse R & D Center; N. E. Dowling, Westinghouse R & D Center; C. M. Hudson, NASA Langley Research Center; E.K. Walker, Lockheed California Co.; and Howard Wood, AFFDL/ FBR, Wright-Patterson AFB.

5 Related ASTM Publications Handbook of Fatigue Testing, STP 566 (1974), $17.25, Fatigue at Elevated Temperatures, STP 520 (1973), $45.50, Probabilistic Aspects of Fatigue, STP 511 (1972), $19.75,

6 A Note of Appreciation to Reviewers This publication is made possible by the authors and, also, the unheralded efforts of the reviewers. This body of technical experts whose dedication, sacrifice of time and effort, and collective wisdom in reviewing the papers must be acknowledged. The quality level of ASTM publications is a direct function of their respected opinions. On behalf of ASTM we acknowledge with appreciation their contribution. ASTM Committee on Publications

7 Editorial Staff Jane B. Wheeler, Managing Editor Helen M. Hoersch, Associate Editor Charlotte E. DeFranco, Senior Assistant Editor Ellen J. McGlinchey, Assistant Editor

8 Contents Introduction Observations on the Prediction of Fatigue Crack Growth Propa. gation Under Variable.Amplitude Loading--J. SCHIJVE Loads in Service Differences Between Crack Growth Studies Definition and Measurement of Interaction Effects Interaction Effects in Tests with Overloads or Step Loading Interaction Effects in Tests with Program Loading, Random Loading, or Flight-Simulation Loading Prediction Methods for Variable-Amplitude Loading SIMPLE SPECTRA: EFFECT OF LOADING VARIABLES Fatigue Crack Growth with Negative Stress Ratio Following Single Overloads in 2024-T3 and 7075-T6 Aluminum Alloys---R. I. STEPHENS, D. K. CHEN, AND B. W. HOM Material and Experimental Procedures Test Results of Results Summary and Effect of Single Overload/Underload Cycles on Fatigue Crack Propagation--W. X. ALZOS, A. C. SKAT, JR., AND B. M. HILLBERRY Test Program Experimental Procedure Data ReductionwNumerical Differentiation Test Results Comparison with Crack Closure

9 Effects of Rest Time on Fatigue Crack Retardation and Observations of Crack Closure--W. N. SHARPE, JR., D. M. CORBLY, AND A. F. GRANDT, JR. Retardation Measurements Surface Measurement of Opening Loads Ultrasonic Measurements Mechanisms of Overload Retardation During Fatigue Crack Propagation--P. J. BERNARD, T. C. LINDLEY, AND C. E. RICHARDS Types of Single Overload Effect Experimental Results SIMPLE SPECTRA: ENVIRONMENTAL EFFECTS AND MODELING Spike Overload and Humidity Effects on Fatigue Crack Delay in A17075-T651--OTTO BUCK, J. D. FRANDSEN, AND H. L. MARCUS Experimental Procedures Results Influences of Chemical and Thermal Environments on Delay in a Ti-6AI-4V Alloy--T. T. SHIH AND R. P. WEI Material and Experimental Work Results and s Summary Effect of Various Programmed Overloads on the Threshold for High-Frequency Fatigue Crack Growthm S. W. HOPKINS, C. A. RAU, G. R. LEVERANT, AND A. YUEN Experimental Procedure Experimental Results and Metallography and Fractography General

10 A Model for Fatigue Crack Growth Delay Under Two-Level Block Loads--O. A. ADETIFA, C. V. B. GOWDA, AND T. H. TOPPER Previous Quantitative Models Composite Stress Intensity Parameter Crack Arrest Condition Summary and Mathematical Modeling of Crack Growth Interaction Effects--- P. D. BELL ANDA. WOLFMAN Results and Concluding Remarks Experimental Results and a Hypothesis for Fatigue Crack Propagation Under Variable.Amplltude Loadingu G. H. JACOBY, H. NOWACK, AND H. T. M. VAN LIPZIG Experimental Crack Propagation Behavior and l COMPLEX SPECTRA: LOAD DEFINITION, MODELING, AND SERVICE SIMULATION Effect of Spectrum Type on Fatigue Crack Growth Life-- J. A. REIMAN, M. A. LANDY, AND M. P. KAPLAN Mission Profile Definition Spectrum Development Analytical Model Verification Results and Stress Spectrums for Short-Span Steel Bridges-- K. H. KLIPPSTEIN AND C. G. SCHILLING Field Measurements Control Tapes for Fatigue Tests Fatigue Crack Growth Under Variable-Amplitude Loading in Various Bridge Steels--J. M. BARSOM Materials and Experimental Work Results and Summary

11 Equivalent Constant-Amplitude Concept for Crack Growth Under Spectrum Loading--WOLF ELBER Analysis Testing Results and Concluding Remarks Crack Growth in Ti-8AI-IMo-IV with Real.Time and Accelerated Flight-by-FUght Loading--L. A. IMIG Experimental Considerations Crack-Growth Analysis Results and Concluding Remarks LIFE PREDICTION AND APPLICATIONS Prediction of Fatigue Crack Growth Under Irregular LoadinguD. V. NELSON AND H. O. FUCHS Input Data for Predictions Crack Growth Rate Relations Prediction of Crack Growth for Irregular Loadings Comparison of Predictions with Test Results for Irregular Loadings Structural Reliability Prediction Method Considering Crack Growth and Residual Strength--S. R. VARANASI AND I. C. WHITTAKER Analytical Development Crack Growth Model Residual Strength Model Structural Reliability Model Results Spectrum Crack Growth Prediction Method Based on Crack Surface Displacement and Contact Analyses--H. D. DILL AND C. R. SAFF Crack Surface Displacement Analyses Contact Stress Analyses Constant-Amplitude Crack Growth Crack Growth Following High Loads Blocked Spectrum Crack Growth

12 Spectrum Fatigue Crack Growth in Lugs--L. F. IMPELLIZZERI AND D. L. RICH Test Program Analytical Techniques Summary Glossary