Astm stp 632 1977

DEVELOPMENTS IN FRACTURE MECHANICS TEST METHODS STANDARDIZATION A symposium presented at St Louis, Mo., May 1976 ASTM SPECIAL TECHNICAL PUBLICATION 632 W F Brown, Jr., NASA-Lewis Research Center, and J G Kaufman, Aluminum Company of America, editors List price $24.75 04-632000-30 AMERICAN SOCIETY FOR TESTING AND MATERIALS 1916 Race Street, Philadelphia, Pa 19103 # NATIONAL AERONAUTICS AND SPACE ADMINISTRATION Copyright by ASTM Int'l (all rights reserved); Mon Dec 21 11:23:28 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized BY AMERICAN SOCIETY FOR TESTING AND MATERIALS 1977 Library of Congress Catalog Card Number: 77-73544 NOTE The Society is not responsible, as a body, for the statements and opinions advanced in this publication is Primed in Baltimore, Md September 1977 Copyright by ASTM Int'l (all rights reserved); Mon Dec 21 11:23:28 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Foreword The symposium on Developments in Fracture Mechanics Test Methods Standardization and this resultant publication were sponsored by ASTM Committee E-24 on Fracture Testing of Metals, in particular Subcommittee E24.01 on Fracture Mechanics Test Methods To a very significant extent, this symposium and publication were cosponsored by NASALewis Research Center, specifically through the coauthorship or presentation of six of the invited papers or both, and a very substantial amount of the technical effort that went into the developments reported The symposium itself was held in St Louis, Missouri at the May 1976 ASTM Committee Week; J G Kaufman, Aluminum Company of America, presided as technical chairman W F Brown, Jr., NASA-Lewis Research Center, and J G Kaufman are editors of this publication Copyright by ASTM Int'l (all rights reserved); Mon Dec 21 11:23:28 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Related ASTM Publications Cracks and Fracture, STP 601 (1976), $51.75, 04-601000-30 Fractography-Microscopic Cracking Process, STP 600 (1976), $27.50, 04-600000-30 Mechanics of Crack Growth, STP 590 (1976), $45.25, 04-590000-30 Copyright by ASTM Int'l (all rights reserved); Mon Dec 21 11:23:28 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 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 Copyright by ASTM Int'l (all rights reserved); Mon Dec 21 11:23:28 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Editorial Staff Jane B Wheeler, Managing Editor Helen M Hoersch, Associate Editor Ellen J McGlinchey, Senior Assistant Editor Kathleen P Zirbser, Assistant Editor Sheila G Pulver, Assistant Editor Copyright by ASTM Int'l (all rights reserved); Mon Dec 21 11:23:28 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Contents Introduction Experience in Plane-Strain Fracture Tougiiness Testing Per ASTM Method E 399—i G KAUFMAN Discussion Fracture Toughness Testing Using the C-Shaped Specimen— J H UNDERWOOD AND D P KENDALL 15 25 Analysis of Radially Cracked Ring Segments Subject to Forces and Couples—BERNARD GROSS AND J E SRAWLEY 39 Recent Developments in/j^ Testing—j D LANDES AND J A BEGLEY 57 Compliance Calibration of Specimens Used in the R-Curve Practice—D E MCCABE AND G T SHA 82 Heavy-Section Fracture Toughness Screening Specimen— J L SHANNON, JR., J K DONALD, AND W F BROWN, JR 96 Sharply Notch Cylindrical Tension Specimen for Screening PlaneStrain Fracture Toughness Part I: Influence of Fundamental Testing Variables on Notch Strength—M H TONES, R T BUBSEY, AND w F BROWN, JR Part 11: Applications in Aluminum Alloy Quality Assurance of Fracture Toughness— R J BUCCI, S F COLLIS, R F KOHM, AND J G KAUFMAN 115 Investigation of Some Problems in Developing Standards for Precracked Charpy Slow Bend Tests—GEORGE SUCCOP, R T BUBSEY, M H JONES, AND W F BROWN, JR 153 Estimation of Kj^firomSlow Bend Precracked Charpy Specimen Strength Ratios—GEORGE SUCCOP AND W F BROWN, JR Fracture Testing with Surface Crack Specimens—T W ORANGE (Reprint from Journal of Testing and Evaluation, Vol 3, No 5, Sept 1975) Appendix I—Standard Method of Sharp-Notch Tension Testing of High-Strength Sheet Materials (E 338-68) Appendix II—Standard Test Method for Plane-Strain Fracture Toughness of MetaUic Materials (E 399-74) Appendix IH—Tentative Recommended Practice for R-Curve Determination (E 561-76T) Appendix FV—Tentative Method for Sharp-Notch Tension Testing with Cylindrical Specimens (E 602-76T) Summary Index Copyright Downloaded/printed University 179 193 213 221 241 260 269 283 by by of STP632-EB/Sep 1977 Introduction ASTM Committee E-24 is responsible for test method standardization as well as technology development in the field of fracture testing, and Subcommittee E24.01 has the specific responsibility for fracture-mechanics test methods The latter is the direct descendent of the original Special ASTM Committee on Fracture Testing which started in 1959 to search for means of characterizing the resistance of thin sheet materials to the catastrophic type of fracture which takes place without warning and at stresses below those anticipated from the usual engineering properties Several test methods have already been developed by E24.0I, notably E 338 on Sharp-Notch Tensile Testing of Sheet, E 399 on Plane-Strain Fracture Toughness Testing, E 561 on Resistance Curve Determination, and E 60276T on Sharp-Notch Tension Testing with Cylindrical Specimens and a number of others are in process This volume represents a state-of-the-art report on developments in the field of fracture mechanics test methods within E24.01 These papers were part of an E24.01 sponsored Symposium held in St Louis in May 1976, and include all of the aspects of work within the Subcommittee except that on testing of beryllium The continuing review of the validity requirements in ASTM Method E 399 is the subject of the paper by Kaufman The generation of data which provide information on the effects of individual specimen geometry and testing procedure factors which are not compounded by other variables is slow, but such data may lead eventually to some relaxation or modification of the validity criteria which add to the cost and workability rate of A",^ data The papers by Underwood and Kendall and by Gross and Srawley presage a major change in ASTM Method E 399, namely, the inclusion of a C-shaped specimen with the already present bend and compact specimens; this will answer the need for suitable specimens for cylindrical and tubular components With regard to resistance curves, the development of the most precise calibrations for the various types of specimens employed are described by McCabe and Sha for incorporation into ASTM Method E 561 In the area of new methods, Landes and Begley presented the first complete guidelines for J-integral determination, guidelines which will likely form the basis of a future recommended practice or standard method Copyright by Downloaded/printed Copyright® 1977 b y University of ASTM byInternational AS FM Washington Int'l (all rights reserved); Mon Dec pursuant t www.astm.org (University of Washington) FRACTURE MECHANICS TEST METHODS STANDARDIZATION The subject of part-through-crack testing is represented herein by a reprinting of T N Orange's paper from the September 1975 Journal of Testing and Evaluation A review of this subject was presented at the Symposium by C E Feddersen, but a text of that review is not available With regard to screening tests, the paper by Shannon, Brown, and Donald describes the Metal Properties Council funded study of a new one-side fatigue-cracked, edge-notched specimen being considered to replace the center cracked (CC) specimen in ASTM Method E 338 The complexity of specimen preparation for the latter has resulted in limited use, and a simpler specimen is seen to be needed particularly for very high-strength materials For aluminum alloys, the machined edge-notch (EN) specimen in ASTM Method E 338 has been rather widely used for screening and quality control, and little change is expected here except perhaps a broadening of thickness limits In the area of newer methods for screening tests, Jones and Bucci et al, updated the information on the use of notched cylindrical specimens from both the viewpoint of testing and application This method has been published in the gray pages of Part 10 of ASTM Standards for several years and is now advanced to a Tentative Standard with the designation E 602-76T Another new screening test is covered in two papers from Succop et al, who describe the use of precracked Charpy test to indicate plane-strain fracture toughness; some spinoff to new standard methods in this area is expected within a couple of years Publication of these papers together with the test methods involved provides the most complete document available in the field of fracture toughness testing, and as such it should be of great value to materials research and design engineers J G Kaufman Alcoa Laboratories, Aluminum Company of America, Pittsburgh, Pa 15219; coeditor Copyright by ASTM Int'l (all rights reserved); Mon Dec 21 11:23:28 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized SUMMARY 273 analyses of the ASTM Method E 399-74 bend and compact specimens (Refs 18 19, 20) For the bend specimen (Ref 18), it has been shown that the coefficient in Eq 10 applies to rigid perfectly plastic behavior (where crack and total displacements are equal) at all values of a/W and to the total displacements for linear elastic behavior at a/W values above 0.5 The observation that the same coefficient applies to these two extremes of material behavior lends confidence to the use of this coefficient for the ASTM Method E 399-74 three-point bend specimen geometry An analysis of the compact specimen (Ref 20) leads to a modification of Eq 10 which indicates that the use of Eq 10 with a coefficient of two for the ASTM Method E 399-74 compact specimen could underestimate substantially the value of J The same analysis indicates that the use of total displacements for the compact specimen will not lead to significant errors at a/W values greater than 0.45 The proposed Ju test method focuses attention on the onset of crack extension as determined from a /i resistance curve This curve represents the trend of data on a plot of 7r versus crack extension The data are generated from tests on several specimens loaded to progressively higher values of displacement and then unloaded and broken open to determine the amount of crack extension that had occurred Following unloading, the crack advance is marked by heat tinting or some other suitable procedure The 7, value at the unloading load is computed using the appropriate expression for / If everything goes right, the points will define a curve which is nearly linear at small crack advances This curve is then extrapolated to the "blunting line" (see Fig, 4) and the /i value at the intersection taken as Ju Experience has shown that this method of determining Jic while providing a direct measurement of crack extension, in some cases, leads to uncertain values due to scatter in the data which establish the Ji resistance curve Landes and Begley discuss other methods of obtaining /ic including sensing of crack extension from measurements of compliance, electric potential, and ultrasonics These methods have the potential of permitting the determination of /ic from a single specimen, however, as yet there is insufficient experience with them to permit a meaningful comparison with the multiple specimen technique of the proposed test method Landes and Begley recommend the compact specimen of ASTM Method E 399-74 for Jic tests with a modification that permits the clip gage to sense the displacement on a line connecting the loading pin centers However, as the specimen deforms this measurement does not represent the true load point displacement Calculations show that the errors can become significant for specimens close to the size requirements.' 'Donald, K., "Rotational Effects on Compact Specimens," presented at ASTM E24.01.09 Task Group Meeting, 24 March 1977, Norfolk, Va Copyright by ASTM Int'l (all rights reserved); Mon Dec 21 11:23:28 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 274 FRACTURE MECHANICS TEST METHODS STANDARDIZATION Landes and Begley caution against using the maximum load from a test on a single specimen to calculate 7,^ While it is possible that under some circumstances the maximum load values agree with those determined by the proposed test method, such agreement is fortuitous In many cases, large differences are encountered (for example, Fig 15) with the maximum load values being higher than the J\c values determined according to the proposed test method It is probably too early to clearly define various applications of / However, Landes and Begley mention several, including the characterization of fracture originating from a blunt notch, the description of crack extension under corrosive conditions, the correlation of fatigue crack growth rates, the determination of the load carrying capacity of a structure containing a defect surrounded by a well-developed plastic region, and the determination of Ku by conversion of Jic In addition, they discuss a modification of the J-integral for application to crackgrowth rate correlations under high-temperature steady-state creep conditions For all of these applications, considerable additional data will be required to permit a judgment of their practical value An application which is illustrated by experimental data in the author's paper is the conversion of /ic to Ku Here the practical value lies in the considerable reduction in specimen size that would be, in theory, realized for very tough materials However, this conversion is complicated by the fact that different measurement points are used in the 7ic than in the K\c test procedure Thus, 7ic relates to the onset of crack extension while ^ic relates to percent "effective" crack extension Depending on the steepness of the Ji resistance curve, the Ki