Astm stp 1248 1995

STP 1248 Pendulum Impact Machines: Procedures and Specimens for Verification Thomas A Siewert and A Karl Schmieder, Editors ASTM Publication Code Number (PCN): 04-012480-23 AsTM 1916 Race Street Philadelphia, PA 19103 Printed in the U.S.A Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Library of Congress Cataloging-in-Publication Data Pendulum impact machines: procedures and specimens for verification/Thomas A Siewert and A Karl Schmieder, editors p cm. (STP; 1248) "ASTM publication code number (PCN): 04-012480-23" Includes bibliographical references and index ISBN 0-8031-2018-4 i Impact Testing Equipment and supplies Pendulum Notched bar testing Equipment and supplies I Siewert, T A II Schmieder, A Karl (Albert Karl), 1919-III Series: ASTM special technical publication; {248 TA418.34.P46 1995 620.i'123 dc20 95-13999 CIP Copyright 1995 AMERICAN SOCIETY FOR TESTING AND MATERIALS, Philadelphia, PA All rights reserved This material may not be reproduced or copied, in whole or in part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of the publisher Photocopy Rights Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by the AMERICAN SOCIETY FOR TESTING AND MATERIALS for users registered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided that the base fee of $2.50 per copy, plus $0.50 per page is paid directly to CCC,222 Rosewood Dr., Danvers, MA 01923; Phone: (508) 750-8400; Fax: (508) 750-4744, For those organizations that have been granted a photocopy license by CCC,a separate system of payment has been arranged The fee code for users of the Transactional Reporting Service is 0-8031-2018-4/95 $2.50 + 50 Peer Review Policy Each paper published in this volume was evaluated by three peer reviewers The authors addressed all of the reviewers' comments to the satisfaction of both the technical editor(s) and the ASTM Committee on Publications The quality of the papers in this publication reflects not only the obvious efforts of the authors and the technical editor(s), but also the work of these peer reviewers The ASTM Committee on Publications acknowledges with appreciation their dedication and contribution to time and effort on behalf of ASTM Printed in Fredericksburg,VA May 1995 Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Foreword This publication, Pendulum Impact Machines: Procedures and Specimens for Verification, contains papers presented at the symposium of the same name held in Montreal, Quebec, Canada, on 18-19 May 1994 The symposium was sponsored by ASTM Committee E-28 on Mechanical Testing and its Subcommittee E28.07 on Impact Testing The symposium was chaired by Tom Siewert, National Institute of Standards and Technology, and Karl Schmieder, consultant on mechanical testing Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Contents Overview vii THE SPECIMEN The Role of Strike Marks on the Reproducibility of Charpy Impact Test Results A KARL SCHMIEDER, PATRICK T PURTSCFIER, AND DANIEL P VIGLIOTI'I Effect of Squareness Tolerance on Charpy V-Notch Impact E n e r g y - FRANCISJ MARSH 003 019 The Production of Calibration Specimens for Impact Testing of Subsize Charpy Specimens -DAVID J ALEXANDER,WILLIAMR CORWIN, 032 AND THOMAS D OWINGS Miniaturized Notch Test Specimen and Test Machine Design-MICHAEL P MANAHAN, SR., RANDALL B STONESIFER, YANG SOONG, 039 AND JAMES M BURGER The Optimization of Insert Size for Reconstituting Previously Tested Charpy Specimens -JAMES F WILLIAMS,REGISP SHOGAN,AND LEO ALBERTIN THE ANVILS 070 AND THE STRIKER Effect of Surface Finish of Charpy Anvils and Striking Bits on Absorbed Energy-EARL A RUTH, DANIEL P VIGLIO2~'I, AND THOMAS A S1EWERT Striker Geometry and Its Effect on Absorbed Energy EARL A RUTH 091 101 Charpy Impact Test Results on Five Materials and NIST Verification Specimens Using Instrumented 2-mm and 8-mm Strikers -RANDY K NANSTAD AND MIKHAIL A SOKOLOV 111 The Effect of Charpy V-Notch Striker Radii on the Absorbed Energy THOMAS A SIEWERT AND DANIEL P, VIGLIOIWI 140 Effects of the Striking Edge Radius and Asymmetrical Strikes on Charpy Impact Test Results -MEGUMUTANAKA,YOSHINOBUOHNO, HIDEKAZUHORIGOME, HIROSHI TANI, KENICHIRO SHIOTA, AND AKINORI MISAWA 153 Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized ESTABLISHING REFERENCE ENERGIES Production of Charpy Impact Verification Specimens and Verification of Machine Performance -NAMrrERO HIDA 171 Proposed Changes to Charpy V-Notch Machine Certification Requirements-JOLENE D SPLETF AND JACK C.-M WANG 182 Presentation of the French Supply of Charpy V Reference Test Pieces-GERARDGALBAN, IVAN LE MUET, DENIS MOUGIN, GILBERT REVISE, ROGER ROCHE, AND LOUIS ROESCH 195 TESTING PROCEDURES AND OTHER TOPICS Correction of Charpy Impact Values for Kinetic Energy of Test Specimens-RAJESH G CHANDAVALEAND TAMALDUTTA 221 Load Damping Absorbers and the Determination of Load/Displacemnt Data for Precracked Charpy Specimens -KEN J KARISALLENAND JAMES R MATTHEWS 232 Low Cost Lower Bound Toughness Measurements CHRiSTOpHER N MCCOWAN, JAMES W DALLY, DANIEL P VIGLIOTH, AND OUK S LEE 246 Design and Evaluation of a Verification System for Force Measurements Using Instrumented Impact Testing Machines -THOMASJ MACKIN AND DAVID F TOGNARELLI 268 Instrumented Impact Testing of Polymeric Materials -JORG F KALTHOFF AND GERD WILDE Indexes 283 295 Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Overview This was the sixth symposium published by ASTM on the topic of impact testing The five previous symposia, Proceedings ofASTM, Vol 22~II (1922), Proceedings ofASTM, Vol 38II (1938), STP 176 (1956), STP 466 (1970), and STP 1072 (1990), were sponsored by ASTM Subcommittee E28.07 (prior to 1969 known as E-1.7) These symposia covered a broad range of topics and occurred rather infrequently The period before 1985 might be characterized as one in which the Charpy test procedure was broadly accepted and changing very slowly However, the last symposium (1989), "Charpy Impact Test: Factors and Variables," was driven by new forces: a recognition within ISO Technical Committee 164 (Mechanical Testing) Subcommittee (Fracture) of shortcomings in the procedure and a desire to know the basis for the requirements Although most of the requirements and procedure details were considered quite reasonable and still valid, there was a desire by the late 1980s to restudy a few of the relationships Some felt that changes in materials and energy ranges (from those under which the original relationships were developed) might justify slight revisions to the procedures Also, some other standards and users in other countries had adopted different procedures, which raised questions about comparison of data developed under these different procedures Authors from five countries presented a broad variety of test data at the 1989 Symposium, which encouraged spirited discussion and comparison of the results The twelve papers in the proceedings (STP 1072) and another paper in the Journal of Testing and Evaluation provided a review of the effects of procedural and specimen variables in Charpy impact testing The data proved to be of interest to many general users of the test, but was of particular interest to the members of ASTM Subcommittee E28.07 (the subcommittee responsible for Standard E23 on the Charpy test) During the past five years, the data presented at the symposium have been the single most important factor in determining whether to change various requirements in Standard E-23 The data have also been useful in supporting tolerances and procedt~ral details during the reballoting of ISO Standard 442 on Charpy testing By 1991, the E28 Subcommittee on Symposia suggested that it was time to schedule another symposium on Charpy impact testing One reason was because the 1989 symposium did not answer certain questions about the choice of tolerances in the specifications Indeed, several of the papers appeared to reach conflicting conclusions about the effect of certain variables The Call for Papers for the 1994 Symposium specifically invited studies on the issues of procedures and specimens for machine verification The following paragraphs describe our success in attracting papers that study the procedural details and suggest changes in the tolerances in ASTM and ISO standards This publication includes three papers comparing the 8-mm and the 2-mm radius striker designs These papers (Nanstad and Sokolov; Siewert and Vigliotti; and Tanaka et al.) confirm that the data taken with the two strikers are not interchangeable and suggest that the 8-mm radius typically produces higher energies below about 20 J and that the 2-mm radius striker produces higher energies above 100 J In the intermediate range, the results are less consistent During the final discussion period, we tried to find ways to resolve the use of different striker radii between countries It became clear that there is no easy solution because each country has Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized viii OVERVIEW developed a large statistical database with their own striker design (8- or 2-ram radius) These data have been incorporated in a complex web of other standards and requirements However, it was very encouraging to learn that the European standards (EN series) may add the 8-ram striker in the next revision (in about four years) and that the ASTM subcommittee plans to add the 2-mm striker in their next revision of E23 Unfortunately, there does not seem to be a similar activity in Japan We heard about the development of standardized specimens for indirect verification of machine performance to supplement direct measurements (primary physical characteristics of the machines) Papers by Hida and by Galban et al described the development of standardized specimens for Japan and France, respectively Building on the statistical calculations contained in these two papers, a paper by Splett and Wang provided more details on the determination of the quality of standardized specimens In the area of machine and specimen tolerances, we learned about the effect of machine alignment on second strike marks (Schmieder et al.), the effect of specimen edge squareness (Marsh), striker geometry tolerances (Ruth), striker surface finish (Ruth et al.), subsize speciments (Alexander et al and Manahan et al.), and reconstitution of specimens (Williams et al.) The topic of machine verification is becoming important for nonmetallic materials as well The Call for Papers was developed in discussions with ASTM Subcommittee D20.10 (Mechanical Properties of Plastics) and Section D20.10.02 (Impact Properties of Plastics) to include papers on Charpy and Izod testing of plastics We received a paper by Mackin and TognareUi on calibration of an impact machine for plastics and one by Kalthoff and Wilde on instrumented impact testing of polymeric materials Other papers covered the use of load-displacement curves for obtaining more information from impact tests (KarisAllen and Matthews and McCowan et al.) and the kinetic energy of the specimen being tossed from the machines (Chandavale and Dutta for an unbroken specimen; Kalthoff and Wilde for the two broken halves) Many people commented that they found the information presented in this symposium to be particularly interesting One reason for this may be that the 1994 symposium attracted contributions from many countries, Twenty-one of the forty-two authors and coauthors are from outside the U.S., an even broader participation that in the 1989 symposium We believe that this is due partly to wide distribution of the Call for Papers at international meetings and because of the current importance of this topic in international commerce Although the 1994 symposium provided much useful information that will allow us to improve impact testing standards, it also identified other differences between standards and will require further study before a decision can be made The following topics should be considered for inclusion in the Call for Papers for a future symposium: The theoretical effect of striker contact radius on the state of elastic stress at or near the root of a Charpy specimen notch The use of instrumented strikers to separate the energies of crack initiation and of crack propagation for machines with 8-mm and 2-mm striker radii in the range below 25 J Charpy V-notch absorbed energy Correlation of results of static tests for plane-strain fracture toughness to those for Charpy V-notch impact tests at different temperatures, using both the ISO and the ASTM striker By finite element or other analytical techniques, determine the striker form that will minimize the plastic work of crushing and bending the specimen Compare the absorbed energy as measured by machines with C-type pendulums to Utype, including materials with high yield strength and absorbed energy less than 20 J Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized OVERVIEW ix Acknowledgments We appreciate the assistance of E28.07 members, many of whom helped by chairing the sessions and by reviewing the manuscripts We particularly appreciate the assistance of J M Holt who (in his role and Chairman of Subcommittee E28.93 on Symposia) helped us obtain sponsorship of the Symposium and provided valuable advice on the arrangements, and who (in his role as the U.S delegate to ISO Committee 164-TC4) encouraged international participation We also received wise advice from a large number of the ASTM staff on symposium arrangements, selection of reviewers, and the other myraid of details necessary for a successful symposium Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized The Specimen Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 284 PENDULUM IMPACT MACHINES pendulum impact device The measuring technique and the e v a l u a t i o n p r o c e d u r e f o l l o w in p r i n c i p l e the m e t h o d o l o g y of the C h a r p y - t e s t [!] o r i g i n a l l y d e v e l o p e d for t e s t i n g of steel specimens B e c a u s e of the low load a n d e n e r g y v a l u e s that a p p l y in t e s t i n g of p o l y m e r i c s p e c i m e n s c e r t a i n m o d i f i c a t i o n s of the test techniques, however, are usually needed Furthermore, the obtained results require special i n t e r p r e t a t i o n and c o n s i d e r a t i o n as r e g a r d s their v a l i d i t y to r e p r e s e n t true m a t e r i a l p r o p e r t i e s that i n d e e d c h a r a c t e r i z e the actual failure behaviour of the m a t e r i a l This p a p e r addresses some aspects r e l e v a n t to the impact t e s t i n g of p o l y m e r i c specimens $, firll P,N POLYSTYROL168N 80x10~ ram, unnotched 600 V0 ,~ BIs / 400 200 0 a) 981& I I" I t, ms E.J P,N 60O POLYSTYROL 168N 80xlOx & ram, Eunnotched) v e = mls ~ 1,2 - - ~00 0.8 200 0,~ 0 b) + FIG - - T y p i c a l i n s t r u m e n t e d impact t = time, s = d i s p l a c e m e n t , MEASUREMENT 9a/(, S, m m & test data, (P = load, E = energy) OF I M P A C T L O A D S With the m o d e r n version of the i m p a c t test in its instrumented form, the e n e r g y to b r e a k a s p e c i m e n is not d e t e r m i n e d by the d i f f e r e n c e of the h e i g h t s of the p e n d u l u m h a m m e r b e f o r e a n d after the test; instead, w i t h a load sensor at the tup of the s t r i k i n g h a m m e r the load the s p e c i m e n is Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized KALTHOFF AND WILDE ON POLYMERIC MATERIALS 285 subjected to is m e a s u r e d during the entire loading and s u b s e q u e n t f a i l u r e p r o c e s s of the specimen Then, following Newton's law, integration of the m e a s u r e d load-time-trace determines the p o s i t i o n of the s t r i k i n g h a m m e r during the impact process ; this position is equivalent to the d i s p l a c e m e n t s the s p e c i m e n has u n d e r g o n e s(t)=[[Vo - I r p ( t ) d t ] d t j mj with P t m Vo s = = = = = (I) m e a s u r e d load time mass of h a m m e r (initial) impact v e l o c i t y specimen d i s p l a c e m e n t A plot of the m e a s u r e d load P as f u n c t i o n of the c a l c u l a t e d d i s p l a c e m e n t s and another i n t e g r a t i o n w i t h respect to d i s p l a c e m e n t gives the e n e r g y E to break the s p e c i m e n E(s)=~p(s)ds (2) If the i n t e g r a t i o n is not c a r r i e d out over the entire impact process, partial energy values are obtained by integration up to or in b e t w e e n c h a r a c t e r i s t i c parts of the load-time-curve A typical l o a d - t i m e - r e c o r d and the d e r i v e d displacement-time-, load-diplacement-, and e n e r g y - d i s p l a c e m e n t - t r a c e s o b t a i n e d in a test with a p o l y m e r i c specimen are shown in Fig i It is e v i d e n t essential quantity FIG from Eqs controlling and that the load is the the final m e a s u r i n g result High s e n s i t i v i t y striker tup m a d e of epoxy resin A r a l d i t e B (left) and c o n v e n t i o n a l steel tup (right) Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 286 PENDULUM IMPACT MACHINES Therefore, techniques considered certain aspects regarding the experimental for m e a s u r i n g loads in i m p a c t tests shall be first U s u a l l y foil s t r a i n g a u g e s at the tup of the s t r i k i n g h a m m e r are u s e d as sensors for m e a s u r i n g the load Since the loads for b r e a k i n g polymeric specimens are rather small (several i00 N) the r e s u l t i n g strains in tups w h i c h are u s u a l l y m a d e of steel are v e r y low As a c o n s e q u e n c e , the r e s u l t i n g s i g n a l s are d i f f i c u l t to m e a s u r e and o f t e n d i s t u r b e d by e l e c t r o n i c noise L a r g e r signals c a n be o b t a i n e d u s i n g s e m i c o n d u c t o r s t r a i n g a u g e s but d i f f i c u l t i e s m a y arise from n o n l i n e a r i t i e s a n d / o r t e m p e r a t u r e effects, w h i c h one u s u a l l y w a n t s to a v o i d c o m p l e t e l y in p r e c i s i o n m e a s u r i n g t e c h n i q u e s The author i n t r o d u c e d a h i g h s e n s i t i v y s t r i k e r tup [~] w h i c h is b a s e d on the p r i n c i p l e t h a t the tup is m a d e f r o m a m a t e r i a l h a v i n g a Y o u n g ' s m o d u l u s lower than of steel: the r e s u l t i n g strains thus b e c o m e larger and can e a s i l y be m e a s u r e d w i t h conventional foil strain gauges Tups from titanium-, aluminium-, or m a g n e s i u m - a l l o y s or from the epoxy resin A r a l d i t e B are used The lower the Y o u n g ' s m o d u l u s the larger the strains, and c o n s e q u e n t l y , the h i g h e r the s e n s i t i v i t y The s e n s i t i v i t y of these tups is thus e n l a r g e d by factors r a n g i n g from to a b o u t i00 B e c a u s e of its r e l a t i v e l y h i g h strength, strongly linear-elastic and rate insensitive behaviour Araldite B represents a material very well suited for m a c h i n i n g tups that a l l o w a c c u r a t e m e a s u r e m e n t s of v e r y small load values F i g u r e shows an A r a l d i t e B tup in c o m p a r i s o n to an e q u i v a l e n t steel tup The tup has b e e n c a l i b r a t e d up to loads of 1000 N (see Fig 3), a s t r o n g l y linear r e s p o n s e is obtained 3.6 AU,V 2.7 / CALIBRATION ARALO I T E - ~ / / 1.8 0.9 FIG /" / ~ I I 0.2 SENSITIVITY o.2e~ kN/V I I 0.& Calibration I I 0.6 I I I 0.8 P,kN 1.0 of an A r a l d i t e B tup High sensitivity striker tups in combination with i n s t r u m e n t e d test t e c h n i q u e s r e p r e s e n t a n o t h e r advantage: In the usual non-instrumented test, pendulum devices of s u f f i c i e n t l y low e n e r g y c a p a c i t y are n e e d e d for the t e s t i n g of Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions author 287 KALTHOFF AND WILDE ON POLYMERIC MATERIALS low s t r e n g t h materials: s u f f i c i e n t l y large d i f f e r e n c e s in the p e n d u l u m h e i g h t s b e f o r e and after the test are thus o b t a i n e d and impact energies w i t h s u f f i c i e n t a c c u r a c y are determined As a consequence, p e n d u l u m devices of d i f f e r e n t sizes with e n e r g y c a p a c i t i e s r a n g i n g from 750 J down to 0.5 J and m a x i m u m impact v e l o c i t i e s from 5.5 m/s down to 2.9 m/s are used With the i n s t r u m e n t e d test and high s e n s i t i v i t y striker tups, however, the a c c u r a c y in d e t e r m i n i n g impact e n e r g y values is only d e t e r m i n e d by the a c c u r a c y of the load m e a s u r e m e n t regardless of the e n e r g y c a p a c i t y of the pendulum Thus, w i t h o u t any d i s a d v a n t a g e s oversized (high energy) pendulum devices can also be a p p l i e d for t e s t i n g of low strength m a t e r i a l s if a striker tup of s u f f i c i e n t l y high s e n s i t i v i t y is used O v e r s i z e d p e n d u l u m devices can a c t u a l l y be a d v a n t a g e o u s since i.) impact v e l o c i t i e s higher than usual can be used (if wanted) for the t e s t i n g of low s t r e n g t h materials, 2.) the loading rate during the impact and s u b s e q u e n t failure process of the s p e c i m e n stays p r a c t i c a l l y constant, and 3.) only one p e n d u l u m device is n e e d e d for tests of any kind of m a t e r i a l of any s t r e n g t h property A high e n e r g y (300 J or 50 J) p e n d u l u m device with interchangeable striker tups of different s e n s i t i v i t y r e p r e s e n t s a U n i v e r s a l Impact P e n d u l u m Test System [l,~] 1.o 0.8 0,6 Z a, 0.4 0.2 Q~ LL FREQUENCY BOUND:/lOkHz y / 1MHz o POLYSTYROL Vo=2,90 mls -0.2 -0,4 ' 0.2 0.4 I | | 0.6 0,8 1.0 1.2 TIME t, ms FIG Load-time-signal registered with d i f f e r e n t upper f r e q u e n c y bound amplifiers of As shown by Fig the load signal m e a s u r e d in impact tests shows c h a r a c t e r i s t i c o s c i l l a t i o n s These o s c i l l a t i o n s not r e p r e s e n t d i s t u r b a n c e s due to an i n s u f f i c i e n t m e a s u r i n g t e c h n i q u e but result from the sudden loading the specimen is s u b j e c t e d to by the i m p a c t i n g hammer Thus, these o s c i l l a t i o n s represent true m e c h a n i c a l behaviour of the s p e c i m e n and, consequently, must correctly be measured, recorded, and Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions author 288 PENDULUM IMPACT MACHINES analyzed Foil s t r a i n gauges b e c a u s e of t h e i r small d i m e n s i o n s are c a p a b l e of c o r r e c t l y r e c o r d i n g v e r y fast signals (up to about MHz) It is o f t e n o v e r l o o k e d , however, that the o v e r a l l r e s p o n s e of the load m e a s u r i n g d e v i c e is d e t e r m i n e d by the e n t i r e m e a s u r i n g chain, in p a r t i c u l a r also by the s t r a i n gauge amplifier Since the oscillations in load signals r e c o r d e d w i t h p o l y m e r i c s p e c i m e n s of sizes u s e d in p e n d u l u m test d e v i c e s are in the range of a b o u t 20 kHz (partly larger) the u p p e r f r e q u e n c y b o u n d of the a m p l i f i e r s h o u l d be a r o u n d 50 kHz, b e t t e r i00 kHz (or e v e n h i g h e r if the r a p i d load drop due to b r i t t l e f a i l u r e p r o c e s s e s shall c o r r e c t l y be recorded) F i g u r e shows l o a d - t i m e - t r a c e s of one e x p e r i m e n t r e c o r d e d w i t h a dual c h a n n e l o s c i l l o s c o p e w i t h one c h a n n e l a t t a c h e d to a MHz a m p l i f i e r and the o t h e r c h a n n e l a t t a c h e d to a 10 kHz amplifier The signal o b t a i n e d w i t h the i0 kHz c h a n n e l shows s m a l l e r o s c i l l a t i o n s and, a d d i t i o n a l l y , a s l o w e r i n c r e a s e of the load w h e n c o m p a r e d to the signal o b t a i n e d w i t h the MHz a m p l i f i e r (see a l s o the d i f f e r e n t r e c o r d i n g s of the r a p i d load drop) The signal of a 100 kHz a m p l i f i e r w o u l d p r a c t i c a l l y be the same as o b t a i n e d w i t h the MHz a m p l i f i e r ; these signals r e p r e s e n t the true s p e c i m e n response 800 P,N 600 ~00 200 STRAIN GAUGEINSTRUM SAN, unnotched vo = 3.SSm/s / No 3306 a) L I I 0.5 1.0 1.5 t, ms 2.0 800 P.N 600 PIEZO-QUARTZ INSTRUM SAN, unnofched vo=3.85m/s &00 200 No, 3006 b) 0.5 FIG I I 1.0 1.5 t, ms 2.0 Load-time-signals recorded with a) strain g a u g e b) p i e z o - q u a r t z i n s t r u m e n t e d tup and Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorize KALTHOFF AND WILDE ON POLYMERIC MATERIALS 289 S o m e t i m e s p i e z o - q u a r t z e s , p o s i t i o n e d b e t w e e n the s t r i k e r tup and the hammer, are u s e d as load sensors Since p i e z o q u a r t z e s have t h e i r own n a t u r a l e i g e n f r e q u e n c y (in the range of 40 - 70 kHz for the f a s t e s t p i e z o - q u a r t z e s available) o n l y signals w i t h f r e q u e n c i e s b e l o w these limit v a l u e s can accur a t e l y be m e a s u r e d and, f u r t h e r m o r e , s u p e r i m p o s e d d i s t u r b i n g e i g e n o s c i l l a t i o n s of the p i e z o - q u a r t z can e v e n t u a l l y s h o w up in the m e a s u r e d load signal - if the e i g e n o s c i l l a t i o n s are e x c i t e d by the e v e n t to be r e c o r d e d F i g u r e shows l o a d - t i m e traces r e c o r d e d w i t h a p i e z o - q u a r t z s e n s o r on the one h a n d and w i t h a strain g a u g e i n s t r u m e n t e d tup on the o t h e r hand, for two e x p e r i m e n t s for w h i c h all test p a r a m e t e r s w e r e i d e n t i c a l [3] A c o m p a r i s o n of the two records shows h i g h e r f r e q u e n c y oscillations in the signal r e c o r d e d by the p i e z o - q u a r t z , r e s u l t i n g from e i g e n o s c i l l a t i o n s of the quartz Care is also n e e d e d in c h o o s i n g i m p a c t v e l o c i t i e s that y i e l d l o a d - t i m e - t r a c e s w h i c h can r e l i a b l y be u s e d as a basis for energy calculations Figure shows load-time-traces o b t a i n e d w i t h s p e c i m e n s of the same m a t e r i a l t e s t e d at v a r i o u s impact v e l o c i t i e s [!] The h i g h e r the v e l o c i t y the m o r e p r o n o u n c e d the o s c i l l a t i o n s , i.e., the larger the a m p l i t u d e of the o s c i l l a t i o n s and the lower the n u m b e r of o s c i l l a t i o n s up to a c e r t a i n d i s p l a c e m e n t , as is expected Thus, the h i g h e r the impact v e l o c i t y , the less r e l i a b l e the d e r i v e d e n e r g y value 0,6 vo= 1.0 m/s m/s vo = 2.9 m/s 0,& z e~ 0,2 el M -0,2 2 DISPLACEMENT s, mm FIG Load-time-signals velocities obtained at v a r i o u s impact In c o n c l u s i o n , for i m p a c t t e s t i n g of p o l y m e r i c m a t e r i a l s load m e a s u r i n g systems of s u f f i c i e n t l y h i g h s e n s i t i v i t y in combination with sufficiently fast electronic processing systems are n e e d e d to c o r r e c t l y r e c o r d load t r a c e s w i t h t h e i r n a t u r a l o s c i l l a t i o n s O n l y by c o r r e c t r e c o r d i n g s of the load- Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions auth 290 PENDULUM IMPACT MACHINES t i m e - t r a c e s can the a c c u r a c y of the d e t e r m i n e d e n e r g y values be assessed and can indications on p o s s i b l e erroneously d e t e r m i n e d e n e r g y q u a n t i t i e s be obtained KINETIC ENERGY OF THE MOVING SPECIMEN HALVES P r e c a u t i o n s in the m e a s u r i n g t e c h n i q u e s must be taken to o v e r c o m e the p r o b l e m s a d d r e s s e d in the p r e v i o u s chapter; w i t h sufficient care, however, the e n e r g y a b s o r b e d by the specimen during the impact process can a c c u r a t e l y be determined The second part of this paper a d d r e s s e s the q u e s t i o n w h e t h e r this e n e r g y in all cases r e p r e s e n t s the true fracture energy for b r e a k i n g the specimen In particular, it is i n v e s t i g a t e d h o w m u c h effect the kinetic e n e r g y of the m o v i n g s p e c i m e n halves after the impact process, i.e., after the s p e c i m e n has b e e n b r o k e n into two separate halves, will have on the results Especially when specimens fail in a b r i t t l e manner, the specimen halves obviously exhibit certain kinetic energy quantities, w h i c h is e a s i l y recognized, since the b r o k e n parts are often found large d i s t a n c e s away f r o m the test machine FIG High speed p h o t o g r a p h s of the m o v e m e n t s p e c i m e n halves after impact of the b r o k e n In order to q u a n t i f y the m a g n i t u d e of these kinetic energies, e x p e r i m e n t s were p e r f o r m e d for w h i c h the m o v e m e n t of the specimen halves after the impact process has been Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions auth KALTHOFF AND WILDE ON POLYMERIC MATERIALS 291 p h o t o g r a p h e d w i t h a h i g h s p e e d c a m e r a [4,~] A C r a n z - S c h a r d i n 24 spark high speed camera was utilized for these i n v e s t i g a t i o n s ; the c a m e r a was o p e r a t e d in a s p e c i a l r e c o r d i n g m o d e by w h i c h s h a d o w i m a g e s of the object, i.e the s t r i k i n g tup, the s p e c i m e n , and the a n v i l s are p h o t o g r a p h e d To a l l o w for an o p e n v i e w f i e l d t h e s e e x p e r i m e n t s w e r e p e r f o r m e d w i t h a d r o p w e i g h t t o w e r i n s t e a d of a p e n d u l u m device, b u t all test p a r a m e t e r s w e r e k e p t the same F i g u r e shows 15 of the 24 photographs total o b t a i n e d for a t y p i c a l e x p e r i m e n t The p i c t u r e i n t e r v a l time in this s e r i e s of p h o t o g r a p h s is 0.64 ms The graphical representation in Fig shows the s u b s e q u e n t p o s i t i o n s of the m o v i n g s p e c i m e n h a l v e s r e l a t i v e to e a c h o t h e r in one picture FIG - - P o s i t i o n of the b r o k e n s p e c i m e n h a l v e s a f t e r i m p a c t for s u b s e q u e n t times For each photograph, i.e time step, the local c o o r d i n a t e s of the s p e c i m e n h a l v e s h a v e b e e n q u a n t i t a t i v e l y determined, and from these data the translational and r o t a t i o n a l v e l o c i t i e s of the s p e c i m e n halves, vT and ~R, w e r e calculated W i t h these v e l o c i t i e s the k i n e t i c e n e r g y for t r a n s l a t i o n , TT = 89 , a n d for r o t a t i o n , T~ = 89174 , and a l s o the total k i n e t i c energy, TG = 2(TT+TR), w e r e d e t e r m i n e d A l t h o u g h the t r a n s l a t i o n a l v e l o c i t y vT and the r o t a t i o n a l v e l o c i t y ~R s h o w e d some v a r i a t i o n s wit time ( o b v i o u s l y the free m o v e m e n t of the s p e c i m e n h a l v e s is h i n d e r e d by the anvils) the t o t a l k i n e t i c e n e r g y of the s p e c i m e n h a l v e s was - w i t h i n e x p e r i m e n t a l s c a t t e r - d e t e r m i n e d c o n s t a n t w i t h i n the time range investigated Quantitative data were obtained for the material p o l y s t y r e n e (BASF P o l y s t y r o l PS 168 N) U n n o t c h e d s p e c i m e n s m e a s u r i n g 80 x i0 x m m w e r e t e s t e d at a s u p p o r t span of 60 mm E x p e r i m e n t s w e r e p e r f o r m e d w i t h i m p a c t v e l o c i t i e s r a n g i n g f r o m 0.4 to m/s In the e x p e r i m e n t s the total i m p a c t energy, Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproduction 292 PENDULUM IMPACT MACHINES A, was d e t e r m i n e d by the d e s c r i b e d i n t e g r a t i o n p r o c e d u r e s f r o m the r e c o r d e d load-time-traces; the k i n e t i c e n e r g y of the moving specimen halves a f t e r the impact process, TG, was d e t e r m i n e d f r o m the h i g h s p e e d p h o t o g r a p h s The data are s h o w n in Fig The f o l l o w i n g p h e n o m e n a are o b s e r v e d : First, the measured i m p a c t energy, A, s h o w s a d e c r e a s i n g trend with i n c r e a s i n g l o a d i n g rate, o b v i o u s l y the m a t e r i a l e m b r i t t l e s w i t h i n c r e a s i n g l o a d i n g rate Secondly, and m o s t i m p o r t a n t l y , the k i n e t i c energy, TG, of the s p e c i m e n h a l v e s a f t e r the i m p a c t p r o c e s s r e p r e s e n t s a v e r y c o n s i d e r a b l e p o r t i o n of the m e a s u r e d i m p a c t e n e r g y A 1.4 1.2 -, 1.0 ~" x'~ x POLYSTYROL 165N 80xl0x&mm, u n n o t c h e d 1.2 PENDULUM 1.0 x ",, DROPWEIBHTTOWER ~- 0.8 0.8 w 0.6 o~ 0.6 ~ o.~ 0.~ ~ 0.2 0.2 0 i i I i & i S IMPACT VELOCITY vo, m/s FIG - - M e a s u r e d i m p a c t e n e r g y a n d k i n e t i c e n e r g y of the b r o k e n s p e c i m e n h a l v e s a f t e r i m p a c t for v a r i o u s impact v e l o c i t i e s It m u s t be c o n c l u d e d t h e r e f o r e that the m e a s u r e d i m p a c t energy, n o w d e n o t e d A M~As for c l a r i t y (A = AMEAS), does not represent a true m a t e r i a l property, i.e a p r o p e r t y that c o r r e c t l y c h a r a c t e r i z e s the r e s i s t a n c e of the m a t e r i a l a g a i n s t failure O b v i o u s l y , o n l y a c e r t a i n p o r t i o n of the m e a s u r e d i m p a c t e n e r g y is u s e d as f r a c t u r e e n e r g y for b r e a k i n g the specimen, a n o t h e r o b v i o u s l y v e r y large p o r t i o n is c o n v e r t e d into k i n e t i c e n e r g y of the m o v i n g s p e c i m e n halves As a true and r e l i a b l e m a t e r i a l s t r e n g t h c h a r a c t e r i z a t i o n , therefore, the d i f f e r e n c e of the c o n v e n t i o n a l l y m e a s u r e d impact e n e r g y and the r e s u l t i n g k i n e t i c e n e r g y of the m o v i n g s p e c i m e n h a l v e s is p r o p o s e d A = A TG (3) This d i f f e r e n c e e n e r g y is d e n o t e d i m p a c t f r a c t u r e energy, A TRue R e g a r d l e s s of w h e t h e r the c o n v e n t i o n a l impact energy, A MEAs, or the true impact fracture energy, A TRU~, is considered, a Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized KALTHOFF AND WILDE ON POLYMERIC MATERIALS d e c r e a s i n g trend w i t h i n c r e a s i n g data shown in Fig loading rate results 293 for the Only for specimens that fail in a b r i t t l e m a n n e r are kinetic energy quantities T G of considerable magnitude observed, more ductile failure processes result in c o n s i d e r a b l y smaller or n e g l i g i b l e k i n e t i c energy quantities D i f f e r e n t to the r e p o r t e d behaviour, s p e c i m e n s in the latter case often even not b r e a k c o m p l e t e l y into two s e p a r a t e halves but still remain c o n n e c t e d by c e r t a i n u n b r o k e n parts of the ligament Also, w h e n c o m p a r e d to other, non-polymeric types of materials, the m a g n i t u d e of the kinetic energy, TG, of the m o v i n g s p e c i m e n halves w i t h respect to the c o n v e n t i o n a l impact energy, A, is of p r e d o m i n a n t i m p o r t a n c e for p o l y m e r i c materials only and of much less importance for other materials With steels, for example, even if they fail in a brittle manner and kinetic energies are observed, these kinetic energies are small w i t h respect to the impact e n e r g i e s since the s t r e n g t h and d u c t i l i t y p r o p e r t i e s of steels are higher than of polymers and, consequently, impact e n e r g i e s of c o n s i d e r a b l y h i g h e r m a g n i t u d e s result SUMMARY AND CONCLUSIONS Several aspects of m e a s u r i n g t e c h n i q u e s and e v a l u a t i o n procedures for determining impact energies of polymeric specimens in i n s t r u m e n t e d impact tests h a v e been a d d r e s s e d and requirements for obtaining valid data that correctly c h a r a c t e r i z e the true f a i l u r e b e h a v i o u r of the m a t e r i a l have b e e n presented In particular, it has b e e n shown that the load measuring s y s t e m must m e e t c e r t a i n r e q u i r e m e n t s : the load sensing striker tup must be of s u f f i c i e n t l y high s e n s i t i v i t y and the electronic measuring system must exhibit a s u f f i c i e n t l y high upper f r e q u e n c y b o u n d in order to a l l o w for a correct r e c o r d i n g of the forces the s p e c i m e n is s u b j e c t e d to during the impact process O n l y correct r e c o r d i n g s of the load a l l o w for the correct and r e l i a b l e d e t e r m i n a t i o n of impact e n e r g y values Furthermore, impact energies, although correctly determined, not n e c e s s a r i l y r e p r e s e n t the actual fracture energy for b r e a k i n g the specimen K i n e m a t o g r a p h i c r e c o r d i n g s of the m o v e m e n t of the b r o k e n specimen halves after the impact process have shown that a c o n s i d e r a b l e p o r t i o n of the m e a s u r e d impact energy is t r a n s f e r r e d into kinetic e n e r g y of the m o v i n g specimen halves Thus, only the d i f f e r e n c e of the m e a s u r e d impact energy and the k i n e t i c energy of the specimen halves, denoted impact fracture energy, can serve as a r e l i a b l e quantity characterizing the true failure property of the material E s t i m a t e s on the m a g n i t u d e of these kinetic energy quantities for v a r i o u s c o n d i t i o n s are given An appropriate consideration of these kinetic energy Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions auth 294 PENDULUM IMPACT MACHINES quantities requires further clarification and additional research When impact energies for polymers that fail in a ductile manner are compared to those that fail is a brittle manner, however, the different magnitudes of kinetic energies involved should at least in principle be taken into account REFERENCES [i] ESIS-Document "Proposed Standard Method for the Instrumented Charpy-V Impact Test on Metallic Materials", Draft Ii, prepared by Working Party "European Standard on Instrumented Charpy Testing" of the European Structural Integrity Society (ESIS) TC 5, Technical Sub-Committee on Dynamic Testing at Intermediate Strain Rates, Chairman H MacGillivray, Imperial College, London, U.K., 1994 [2] Kalthoff, J.F., and Achterfeldt, K., "Hochsensitive Schlagfinne zur PrUfung von Kunststoff- oder Keramikproben im instrumentierten Kerbschlagbiegeversuch", Proceedings 13 GESA-Symposium Experimentelle Mechanik in Forschung und Praxis, Bremen, i0./ii May 1990, VDI-Berichte 815, VDI-Verlag, DUsseldorf, Germany, 1990, pp 389-402 and Proceedings WerkstoffprUfung 1990, 6./7 Dec 1990, Bad Nauheim, DVM, Deutscher Verband fur Materialforschung und -prUfung, Berlin, Germany, 1990, pp 43-54 [3_] Kalthoff, J.F., "Ermittlung des Werkstoffverhaltens von Kunststoffen unter schlagartiger Beanspruchung mit dem instrumentierten Schlag-Biege-Versuch", Bericht der Wolpert Forschung und Entwicklung, FE 1/93, Amsler Otto Wolpert-Werke GmbH, Ludwigshafen, Germany, 1993 Kalthoff, J.F., and Takahashi, S., "Characterization of the Strength of Ceramic and Polymeric Materials by Instrumented Impact Testing", Proc IMEKO/GESA Symposium on Risk Minimization by Experimental Mechanics, DUsseldorf, April 28-30, 1992, VDI-Berichte 940, VDI-Verlag DUsseldorf, Germany, 1992, pp 333-344 [_5] Kalthoff, J.F., and Takahashi, S., "On the Measurement of the True Impact Energy of Polymeric and Ceramic Specimens in Instrumented Impact Tests", Proc Int Symp on Impact Engineering, Ed I Maekawa, Sendai, Japan, Nov 2-4, 1992, pp 538-545 Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorize STP1248-EB/May 1995 Author Index A N Nanstad, R K., 111 Albertin, L., 70 Alexander, D J., 32 O B Burger, J M., 39 Ohno, Y., 153 Owings, T D., 32 C P Purtscher, P T., Chandavale, R G., 220 Corwin, W R., 32 R D Revise, G., 194 Roche, R., 194 Roesch, L., 194 Ruth, E A., 91, 101 Dally, J W., 245 Dutta, T., 220 G Galban, G., 194 S Schmeider, A K., Shiota, K., 153 Shogan, R P., 70 Siewert, T A., 91, 140 Sokolov, M A., 111 Soong, X., 39 Splett, J D., 181 Stonesifer, R B., 39 H Hida, N., 170 Horigome, H., 153 K KarisAllen, K J., 231 Kalthoff, J F., 282 T L Tanaka, M., 153 Tani, H., 153 Tognarelli, D F., 267 Lee, O S., 245 Le Muet, I., 194 M V Mackin, T J., 267 Manahan, Sr., M P., 39 Marsh, F J., 19 Matthews, J R., 231 McCowan, C M., 245 Misawa, A., 153 Mougin, D., 194 Vigliotti, D P., 3, 91, 140, 245 W Wang, J C.-M., 181 Wilde, G., 282 Williams, J F., 70 295 Copyright 1995Int'l by (all ASTM www.astm.org Copyright by ASTM rightsInternational reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized STP1248-EB/May 1995 Subject Index Drop-weight testing machines, 267 Ductile-brittle transition temperature, 39 A Absorbed energy, 3, 32, 101, 111 striker effect on, 140, 153 Acceptance limits, 181 Anvil, 91 ASTM standards A 302B: 70 A 533:245 A 533B: 70, 111 E 23: 19, 39, 70, 91, 101 E Elastic-plastic analysis, 39 Electronic frequency response, 282 Energy levels, references for, 170 European Structural Integrity Society, 111 F C Calibration specimens, 32 Certification, machine, 181 Charpy testing machines certification for, 181 compliance, 231 Japanese standards for, 170 verification, 194, 267 Charpy V-notch specimens, 3, 101 impact energy, 19, 194 Japanese standards for, 170 lower bound toughness, 245 miniaturized, 39 neutron damage monitoring with, 39 notch location, 153 reconstituted, 70 reference specimens, 181, 194 striker, 111, 231 striker radii, 140 subsize, 32 surface finish, 91 velocities, 220 Crack initiation, 245 D Damping absorbers, load, 231 Damping, viscous, 267 Deformation analysis, large, 39 Density, 220 Finite element analysis, 39 Force measurement, 267 Forging, 111 Fourier analysis, 267 Fracture behavior, transitional, 39 French standards, 194 Friction, 91 I Impact, controlled, experiments, 267 Impact energy, 19, 194 J Jamming after fracture, 19 Japanese standards, 170 K Kinetic energy, 220, 282 L Lateral expansion, 111, 153 Load cells, 267 Load/displacement data, 231 Loading, asymmetry of, Load traces, 282 Lower bound toughness, 245 297 Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 298 PENDULUMIMPACT MACHINES M Mechanical damping, 231 Metals, 3, 32, 70 Charpy V-notch squareness tolerance, 19 A 302B: 70 A 533:245 A 533B: 70, 111 E 23: 19, 39, 70, 91, 101 Modeling, Charpy shift trend curve, 39 N National Institute of Standards and Technology, 111, 181 National Testing Laboratory, 194 Neutron damage monitoring, 39 Nuclear reactor, 39, 70 Nylon alloy, 267 P Polymeric specimens, 282 Pressure vessel, 39, 70, 111 Projection welding, 91 Standards (See also ASTM standards) EN 10045-2, 194 ISO DIS 442, 194 ISO TC, 140 Japanese, 170 National Institute of Standards and Technology, 111, 181 Steel, 32, 70 high strength, Stress intensity, 245 Stress waves, 267 Strike marks, Striker, 91, 101, 111 edge, 153 radius, 140 striker geometry, 101 tups, 282 Surface finish, 91 Symmetry effects, 153 T Three-dimensional analysis, 39 Three-point bend test, 231 T-test, 19 Toughness, 70, 245 Tup, instrumented, 245 Tup, striker, 282 Tup, verifier, 267 Two-dimensional analysis, 30 U R Reconstitution, 70 Reference specimens, 19, 111, 140, 181, 194 Restitution, coefficient of, 220 Upper shelf energy, 39, 70 Upper shelf submerged arc weld, 111 V Velocity, 220 S W Shear lips, Spinning, specimen, 19 Squareness tolerance, 19 Weld, 111 Welding, projection, 70, 91 Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:24:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized I I 0 I I:~ Z I I