Astm stp 1323 2001

STP 1323 Nontraditional Methods of Sensing Stress, Strain, and Damage in Materials and Structures: Second Volume G E Lucas, P C McKeighan and J S Ransom, editors ASTM Stock Number: STP1323 ASTM 100 Barr Harbor Drive PO Box C700 West Conshohocken, PA 19428-2959 Printed in the U.S.A Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions autho Copyright 2001 AMERICAN SOCIETY FOR TESTING AND MATERIALS, West Conshohocken, 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, personal, or educational classroom use, or the internal, personal, or educational classroom use of specific clients, is granted by the American Society for Testing and Materials (ASTM) provided that the appropriate fee is paid to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923; Tel: 978-7508400; online: http://www.copyright.com/ Peer Review Policy Each paper published in this volume was evaluated by two peer reviewers and at least one editor The authors addressed all of the reviewers' comments to the satisfaction of both the technical editor(s) and the ASTM Committee on Publications To make technical information available as quickly as possible, the peer-reviewed papers in this publication were prepared "camera-ready" as submitted by the authors 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 the peer reviewers In keeping with long-standing publication practices, ASTM maintains the anonymity of the peer reviewers The ASTM Committee on Publications acknowledges with appreciation their dedication and contribution of time and effort on behalf of ASTM Printed in Saline, MI April 2001 Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Foreword This publication, Nontraditional Methods of Sensing Stress, Strain, and Damage in Materials and Structures: Second Volume, contains papers presented at the symposium of the same name held in Kansas City, Missouri, on 17 November 1999 The symposium was sponsored by ASTM Committee E8 on Fatigue and Fracture The symposium cochairpersons were George F Lucas, MTS Systems Corporation, Peter C McKeighan, Southwest Research Institute, and Joy S Ransom, Fatigue Technology Incorporated Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authori Contents vii Overview F R A C T U R E M E C H A N I C S AND S T R U C T U R A L INTEGRITY Characterizing Crack Growth in Thin Aluminum Panels Under TensionTorsion Loading Using Three-Dimensional Digital Image Correlation-J D H E L M , M A S u ' v r O N , A N D M L B O O N E Sensing Crack Nucleation and Growth in Hard Alpha Defects Embedded in T i - A I - V A l l o y m P c Mcr,EIGHAN, A E NICHOLLS, L C PEROCCm, AND 15 R C M c C L U N G Use Experience with a Development General Purpose Non-Contacting Extensometer with High ResolutionmA TOWSE, C SETCHELL, S K POTTER, A B C L A R K E , J H G M A C D O N A L D , M R W I S N O M , AND R D A D A M S 36 Analysis of Fatigue Crack Propagation by Quantitative Fractography-N R A N G A N A T H A N ) N G E R A R D , A TOUGUI, R LEROY, M B E N G U E D I A B , M M A Z A R I , Y N A D O T , AND J PETIT 52 DAMAGE EVOLUTION AND MEASUREMENT A C o m p a r i s o n o f M a c r o s c o p i c to Microstructnrai Strain Fields in Cortical n o n e - - D P N I C O L E L L A , A E N I C H O L L S , J L A N K F O R D ) A N D D T D A V Y 87 Detection of Localized Plastic Deformation in Pipelines Using the Nonlinear H a r m o n i c s M e t h o d - - G L B U R K H A R D T A N D A E C R O U C H 101 S T R A I N AND D I S P L A C E M E N T M E A S U R E M E N T T E C H N I Q U E S Experimental Measurement of Strains Using Digital Volume Correlation-T S SMITH A N D B K B A Y Measurement of Stress Distributions on Silicon IC Chips Using Piezoresistive SensorsmJ c SUHLING A N D R C J A E G E R 117 127 Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions au Real-time Phase Analysis Methods for Analyzing Shape, Strain and Stress-v MORIMOTOAND M FUJIGArO 153 Strain Gauges, F i b e r Optic Versus E l e c t r i c - - s CHEN AND J S SIRKIS 169 L o n g - T e r m M e a s u r e m e n t of Local C r e e p Deformation by Optical Fi b er M a r k i n g and Remote M o n it o r i n g - - s - T TU, J.-M GONG, X LLNG, AND X.-Y 184 HE Thermal Fracture Mechanisms in Plasma Sprayed Thermal Barrier Coatings Under Cyclic Laser I r r a d i a t i o n - - x Q MA AND M TAr.EMOTO 193 PANEL DISCUSSION SUMMARY Current Status and Future Sensor Development: Panel Discussion Summary-J S R A N S O M A N D P C M c K E I G H A N 211 Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Overview A mechanical test is of little value without some type of sensor to (a) control the test, (b) provide a measurement of physical behavior or (c) indicate when the test is completed The most common sensors are those that measure force, displacement and strain Although many sub-classifications of these devices exist, industrial development of new force, displacement and strain sensors is ongoing, often driven by a new application where the parameters exceed the limits of the currently available sensors Perhaps a good parallel example of this is the ceramics development that occurred during research concerned with the now defunct high-speed civil transport Had this aircraft not been envisioned, several of the current high temperature materials would likely not exist The focus of this symposium is the development and application of nontraditional sensors For instance, several novel methods to measure strain in a body are available using noncontacting techniques In particular, there has been a large amount of work using visionbased sensors to measure the deformation field on a material or structure Although this is only one example, there are other new, novel methods of measuring parameters that may directly correlate with some form of damage within the material or structure The purpose of this symposium is to assess the state of the art of these sensing methods and examine their future potential use as standardized tools within the testing communities Encouraging use of these new sensing methods and extending them into industrial application will presumably be a consequence of the symposium This symposium, held in November of 1999 in Kansas City, is the second in a series of symposia concerned with nontraditional methods of sensing stress, strain and damage The first, STP 1318, was held in May of 1996 in Orlando, Florida and was preceded by two workshops on the same topic in earlier years These Symposia and Proceeding Workshops were instigated by task group E08.03.03 on Sensors, which is a task group of the committee on Fatigue and Fracture and its subcommittee on Advanced Apparatus The scope of this task group is to develop standards and encourage technology interchange concerning measurement sensors that are used in determining fatigue and fracture characteristics of materials and structures Perhaps one of the major differences between the first and second symposium (a span of three and a half years) was the increase in capability apparent in personal computers A close examination of all of the papers in this symposium will show that at the heart of all of the systems presented was a computer As we all know, the speed of the CPU's has been doubling every two years to eighteen months (Moore's Law) However what became apparent during the symposium was not the pivotal role that increased processing speed was playing but rather the enormous impact of infinitely available, low cost RAM and storage space This is probably most clearly evident for vision-based sensors that manipulate and interpret images Greater RAM allowed more on-the-fly computations and high-speed storage space (gigabytes plus) implying enhanced flexibility The twelve papers included in this STP are very diverse, both from the viewpoint of the applications considered as well as concerning the sensors applied Four of the papers included in this STP utilize imaging systems to infer deformation fields Helm, Sutton and Boone use their 3-D system to characterize fatigue crack growth for aluminum panels under tensiontorsion loading Towse et al describe a general purpose, 2-D non-contacting extensometer derived from video images and capable of tracking multiple targets at high speed Two other Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13vii EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized viii NONTRADITIONAL METHODS OF SENSING STRESS/STRAIN papers, Smith and Bay and Nicollela et al examine strain fields in biological material (bone) using image correlation techniques Two papers focused primarily on acoustic emission techniques: McKeighan et al examined crack nucleation and growth from defects in titanium and Ma and Takemoto considered thermal fracture in coatings subjected to cyclic laser irradiation Two other papers focused on fiber optic methods of measuring strain and deformation Chen and Sirkis examined the costs and benefits of fiber optic versus conventional electric strain gages Conversely Tu et al measured long-term creep deformation using quartz optical fiber marking, remote monitoring and image processing The remaining four papers examined relatively unique applications and sensors Suhling and Jaeger present work where the structural reliability of IC chips is measured using piezoresistive sensors bonded to the chip substrate Morimoto and Fujigaki present work concerning the real-time phase analysis of Moire images to analyze shape, strain and stress The final two papers concern damage measurement Ranganathan et al examines methods for quantitative fractography where the fracture surface of a failed specimen can be used to assess loading conditions that led to failure Finally, Burkhardt and Crouch present a magnetic nonlinear harmonics approach to detect localized plastic deformation in pipelines Organizing these papers in some cogent manner is a challenge in view of the diversity of applications, methods, sensors and focus Nevertheless, the approach adopted is intended to address the focus of the papers In the first section, Fracture Mechanics and Structural Integrity, the papers that talk about cracks (either crack growth or fracture) or general stressstrain behavior are included The papers that address the damage state of a material are included in the section entitled Damage Evolution and Measurement whereas the final section considers Strain and Displacement Measurement Techniques Following the symposium, a brief panel discussion was held focussing on issues such as where sensor development was going, what was spurring sensor development and what ASTM standardization activities could assist this process This was a lively discussion and it is succinctly summarized at the conclusion of this book after all of the technical papers The technical community is clearly faced by some technical challenges first and foremost being the cost of new sensors and the magnitude of the effort required to develop them ASTM can play an important role in this process by insuring that the standards are available to assess the performance of sensors once developed However the breadth of the standards required for this and covering sensor technology not yet even discovered is awe inspiring The editors would like to express their sincere appreciation to all of the authors and coauthors responsible for the papers included in this STP and the presentations made during the symposium Furthermore we would like to recognize the efforts of the reviewers whose high degree of professionalism and timely response ensures the quality of this publication Finally, the editors would also like to express their sincere gratitude to ASTM planning and editorial staff for their assistance with the symposium as well as their critical input to this special technical publication Finally, it should be noted that Tait S Smith, co-author of the paper "Experimental Measurement of Strains using Digital Volume Correlation" formerly with the University of California, Davis, received the "Best Presented Paper Award" for his excellent presentation at the symposium This honor was bestowed based upon the critiques of five seasoned professionals in the audience Peter C McKeighan Southwest Research Institute San Antonio, TX Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13Symposium EST 2015 co-chairman and editor Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions auth Fracture Mechanics and Structural Integrity Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further re J D Helm, L M A Sutton, and M L B o o n e Characterizing Crack Growth in Thin Aluminum Panels Under TensionTorsion Loading Using Three-Dimensional Digital Image Correlation Reference: Helm, J D., Sutton, M A and Boone, M L., "Characterizing Crack Growth in Thin Aluminum Panels Under Tension-Torsion Loading Using Three-Dimensional Digital Image Correlation," Nontraditional Methods of Sensing Stress, Strain, and Damage in Materials and Structures: Second Volume, ASTM STP 1323, G F Lucas, P C McKeighan, and J S Ransom, Eds., American Society for Testing and Materials, West Conshohocken, Pa, 2001 Abstract: The enclosed work was performed to determine whether a critical crack opening displacement (COD) criterion can be used to predict the stable crack growth behavior of thin, 2024-T3 aluminum fracture specimens experiencing tension and torsion loading Due to the complexity of the large deformations that occur near the crack tip in a single edge-cracked specimen under torsion loading, a state of the art three-dimensional computer vision system was developed and employed to make the three-dimensional vector displacement measurements required to determine COD Results from the experimental program indicate that the three-dimensional surface profile and deformation measurement system was fully capable of making the required measurements, even in the presence of large, out-of-plane displacements and surface strains that occurred during the tension-torsion loading process Specifically, the measurements show that (a) critical COD for tension-torsion loading is constant during crack growth, (b) COD is approximately 8% larger than observed for in-plane tension-shear and (c) the surface strain fields during crack growth are quite complex due to the coupling of out-of-plane displacements and in-plane surface strains Keywords: mixed mode fracture experiments; tension-torsion loading; threedimensional digital image correlation; non-contacting measurements; crack opening displacement 1Chief Engineer, Correlated Solutions, Inc.; 300 Main Street; Suite Cl13-N; Columbia, SC 29208 2Professor and former graduate student, respectively; Department of Mechanical Engineering; University of South Carolina; Columbia, SC 29208 Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST32015 Downloaded/printed by Copyright 2001 by(University ASTMofInternational University of@ Washington Washington) pursuantwww.astm.org to License Agreement No further reproductions authorized 198 NONTRADITIONALMETHODS OF SENSING STRESS/STRAIN signals were emitted during the cooling period; another is that Mode-I cracking is predominant among the classified AE signals The AE signals almost were monitored during each cycle of the shock tests at a laser power above 60W, and more AE signals were detected in the No.3 specimen during the first three cycles, but for the No and specimens AE counts appear to increase with increasing cycling numbers The result showed that the No.3 specimen was much susceptible to degradation at the earlier period of the shock tests For the No,1 and specimens, there is no obvious difference in the AE counts when laser power is below 70W, but the AE counts detected in the No.2 specimen tended to exceed those monitored in the No.1 specimen under higher laser power In addition, the resonant sensor detected more AE signals, and provided additional evidence for more AE signals emitted in the No.2 specimen Figure 3-Simulated out-of-plane displacements due to Mode-land l l fractures Source parameters: rise time = # s, crack volume = 2xlO"15m3; PD = 12ram Estimation o f Crack Source Parameters by a Waveform Simulation Some typically detected waveforms and the simulated out-of-plane displacements ( abbreviated as Displ.) are shown in Figure Specimen, propagation distance and laser power P are described in the figure caption, and the estimated source parameters are shown at the simulated waveforms The initial portion of the simulated waves resemble well the experimental recordings However, the many peaks in the monitored waves after 10 ~t s are the reflected waves Types A, B, D and E fractures represent the vertical cracking in the coatings, and Types C, F and G represent the horizontal cracking or Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized MA AND TAKEMOTO ON CYCLIC LASER IRRADIATION 199 interfacial delamination In the case that the AE responses are quite similar in waveforms for different types of cracking such as Type B and C in Figure 5, the measurement of polarity distribution and simulation of artificial crack source combined with metallographic observation were used to reduce the uncertainty The estimated source parameters are presented in Figure It is noted that the rise times for Mode-I cracking vary in the range of to 3/~ s for the No specimen, and to tz s for the No.2 and specimens The No.1 specimen has a typical crack volume of less than 2x10"~Sm3, and there is no difference in source parameters for Mode-I and II fractures (Figure 6(A)) In contrast, the No.2 specimen has a different rise time of 3-7 tz s and 1-3 tz s for Mode-I and II cracks, respectively In Figure 6(C), some larger crack Figure 4-Count, distribution and fracture mode of AE signals generated during thermal shock test (A) No I specimen, (B) No.2 specimen, and (C) No specimen Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 200 NONTRADITIONAL METHODS OF SENSING STRESS/STRAIN i0"*2 x l O"~2 [ Type A (bk=i,O,O) (mi=1,0,0) Mode I-" ] ~.~ i0 15 x10 l~ Time, Its 20 t" t ~.~ TypeB n4f V'O~ ~ / "~ -0.4 (mi=0,1,0) I0 15 ,dO "t'~ Time, ~s I -o.8[ 20 I t| 10 15 Time, Its xlO'n d 20 A /~tr=2,8 laS ~_ ~ V, , , 20 I0 15 xl0 -iz Time, i/s -2 z Type C (b~:=o,o.l) (mi=o,o,1) t~ ~|r =3.0 tlS ~ = , -is I ~ o -o:~ i0 xl0 "is Time, Its E 15 20 20 i0 15 x10 43 Time, gs ~ [~t,=3.2~ 2.5 = " /, t " Type D (bk=1,0,0) m -lo (mi=o,1,0) I0 15 xl0 "L2 Time, ~s ~ -0.6 -i.o I0 15 Time, Its x.10"~ Type F (b~=~,0,0) ~ (mi=0,0,1) 2.o , 1.0 0.0 -1.0 -2.0 ~ -1.5 -2.0 20 0 10 15 x.10"z~ Time, ~s 20 30 ~t,.4.sus ,-, t E 20 ~Vo.194x10?r~ ~ xl0 a'~ 10 15 Tim% ~ts 20 0.0 -1.0 , 20 i0 15 xlOa-~ Time, Its E 2.o ~ 1.0 0.0 -1.0 Co~:=o4,o) ~ -2.G (mi=o,O,l) 20 E 0.0 : -0.5 0.0 (b~,=o3,o) ~ -1.0 -1.5 M o d e II(rn~=i,o,o) i0 15 xl0"n Time, p.s o ~ (E) 1.0 Type E 20 / \ vo.2.o,,o ,,, Type G I I I 10 15 Time, pa I[ 20 0.0~ j ' , i0 , 15 Time, ~s 20 Figure5-Some detected (left) and simulated (righO waveforms for the Mode-I and II cracks in the TBC specimens (B) No.1 specimen, P=9OW, P.D.=I4mm, (D) No.2 specimen, P=9OW, P.D.=15mm, (F) No.3 specimen, P=9OW, P.D.=21ram, (A) No.3 specimen, P=8OW, P.D.=I 7ram, (C) No.1 specimen, P=7OW, P.D.=2Omm, (E) No.3 specimen, P=7OW, P.D.=17mm, (G) No.2 specimen, P=8OW, P.D.=15mm Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized MA AND TAKEMOTO ON CYCLIC LASER IRRADIATION 201 volumes (>5x10"lSm3 ) due to Mode-II cracks in the No.3 specimen are estimated under laser power over 80W, indicating extensive delamination during the shock test The results of the estimation of source parameters revealed that the fracture and frequency depend on coating thickness, structures and heating conditions, and the thermally induced damage in the TBCs can be reduced by reducing the thickness of the ZrO2 top layer and further applying the bond layer ,0 (A) Mode Mode II 'o E O > t O ~ Source Rise Time,/1 s 30 -= ~ 25 25 To 20 "~ 20 (C) x 15 -i ot, >O a~ o o 0L,~, , ~' , I 81 92 1'0"1'1 Source Rise Time,/1 s O 0 Source Rise Time,/1 s Figure 6-Estimated source parametersfor the cracks in the TBC coatings (A) No specimen, (B) No.2 specimen, and (C) No.3 specimen Simulation of Mode-I and H Fractures by Using Artificial Crack Sources In order to confirm the relation between fracture mode and relevant waveform of the out-of-plane displacement by experimental methods, Mode-I and II fractures were simulated by using artificial crack sources Using a line-focused YAG laser irradiation (half value duration 5ns; power 2mJ; size 0.04mm x 3mm), a Mode-I crack was simulated by adiabatic thermal expansion in the direction normal to the line As shown in Figure 7(A), the laser beam was line focused on the surface of the No.3 specimen in the direction of the surface normal or on the side surface The former simulates the Types A and B, and the latter the Type C A displacement-type sensor was mounted on the lower surface of the substrate at a propagation distance o f 24ram Because of unknown source parameters for the adiabatic thermal expansion, the source parameters were estimated from the measured displacement due to a Type A crack, and used for computing the displacements of Types B and C cracks The detected and simulated Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 202 NONTRADITIONALMETHODS OF SENSING STRESS/STRAIN displacements due to a Mode-I crack are given in Figure The values o f A t~ and V0 were estimated as 2.5 # s and 2.2x10 Is m 3, respectively The detected displacements generated by the P-, SP-and S waves appear to be comparable to the computed values, and the rise times o f the P-waves agree well, but the monitored amplitudes are slightly larger than the computed data for Types B and C cracks This is a consequence o f using the Green's function o f substrate steel, while the crack occurred in the surface layer o f the coating Utilization o f an experimental transfer function, including combining effect o f a coating and substrate, will provide more accurate source parameters Figure 7-Schematic setup for Mode-I and Mode-H cracks induced by a line-focused YAG laser beam (.4) and a shear-mode PZT element (B), respectively A Mode-II crack was simulated by using a shear-mode PZT element of r mm x w mm x 8r mm (nominal resonant frequency, 1MHz) As shown in Figure 7(B), the PZT element was glued on the surface of the No specimen and excited by a step-wise voltage Types F and G cracks were simulated by an arrangement of the PZT element normal and parallel to the x-axis, respectively The monitored and computed waveforms are presented in Figure The rise time of 6.5 /x s and crack volume of 18.6x10 -15 m were estimated from the detected displacement due to a Type F crack, and used to compute the displacement due to a Type G crack It is noted that the computed amplitude of the P-wave due to a Type F crack (Figure 9) is nearly one order of magnitude larger than that due to Type G The detected values showed a similar change in magnitude, indicating that a Mode-II crack had been simulated effectively by using a shear-mode PZT element By comparing the waveforms due to the artificial cracks (Figure and 9) with those from cracks during the shock test (Figure 5), it is observed that they are comparable while their source parameters are near, such as Mode-I (Types A, B and C) and Mode-II (Type F) Therefore, these results provide some experimental evidences for being able to classify fracture modes and estimate crack source parameters by a source waveform simulation Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorize MA AND TAKEMOTO ON CYCLIC LASER IRRADIATION 203 Mode I Detected ~vaveform xlO.12 Simulated waveforrn ~ 0.5 A (mi=l,O,O) ~ -2.oII m6~o~';" Type A 9~ -1.~0 t0 15 xl0.~ Time, Its 2.0 -o.s ~ (bk=l'0'0) -3 10 15 raO-~3 Time, Its "6.o~ o:o (ml=0,1,0) , v , , 10 xto.~.~ Time, 15 gs 20 (~=o,Lo) , t3 1.5 1.0 0.5 ~ 0.0 ~ -0.5 XJ.O 8.0 6.0f 4.0 I- TypeC "~ -1.o I 20 ~ 4.0 2.0 TypeB _~ o.o ~ / -Lo l" 2o IIlf 1.0 0.5 x " t ~ -1.5 S l"~ o.o 0.0 ~ "~ -1.o 9~ xl0 "t2 9-.0 ~ " I I 10 15 Time, Its 20 (mt=0,0,D (bk=0,0A) , 10 15 T i m e J ItS 20 S SP/VI r 0.0 m -4.0 t -6.0 0I 2.73X10 "5J 10i 15i 20 Time, Its Figure 8-Detected and simulated waveforms due to Mode-I cracks simulated by an adiabatic thermal expansion of line-focused YAG laser Source parameters." rise time = 2.5 # s and crack volume = 2.2xlOtSmS ; P.D = 24ram Fracture Mechanisms in the TBC Specimens under Cyclic Laser Irradiation The microstructures of the TBC specimens were observed after the thermal shock tests The surface morphologies are obviously influenced by the heating conditions At laser power was below 60W, as shown in Figure 10(A), the cracks were initiated mainly in the irradiated zone, and then propagated into the heat-affected region Accordingly, vertical cracks (Mode-I) were observed in the cross-sections of the ZrO2 layer, but no serious delamination was observed in any specimens (Figures ll(A) and (C)) With increasing laser power up to 90W, a melted zone was formed in the center of the irradiated region due to the Gaussian distribution of laser power density (Figure 10(13)) It was observed that more cracks were generated in the center and edge of the melted zone, and also in the adjacent heat affected zone These cracks occurred during the cooling period of the cycles These results also were consistent with those of increasing AE event counts at higher laser power Under the laser irradiation of 90 W and 100W, the ZrO2 coating spalled locally along the edge of melted zone in the No.3 specimen (Figure ll(D)), and at the bond/top coating interface in the No.1 specimen (Figure 10(B)) From the metallographic examination, it also is noted that the number of Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reprod 204 NONTRADITIONALMETHODS OF SENSING STRESS/STRAIN observed cracks is much smaller than the AE counts recorded This implies that a cracking in the specimens experienced different stages of microcrack initiation and growth, and propagated into macrocrack responding to the cross-section cracking in the ZrO2 layer and delamination at the bond/top coating interface The AE system had monitored and characterized well the cracking processes Figure 9-Detected and simulated waveforms due to Mode-Ilcracks simulated by excitation o f shear-mode P Z T element Source parameters." rise time ~- 6.5/1 s and crack volume = 18.6xllTZS m3; PD = 23mm Figure l O-Surface morphologies o f the specimens subjected to the thermal shock tests (,4) No.1 specimen, P = 50W, and (13) No.3 specimen, P = 90W Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized MA AND TAKEMOTO ON CYCLIC LASER IRRADIATION 205 Figure 11-Optical observation on the cross-sections o f the TBCs subjected to the thermal shock tests (,4) No.1 specimen, P = 60W, (B) No.1 specimen, P = 100141, ( No.3 specimen, P = 60W, and (D) No.3 specimen, P = IOOW Normally, transient stress is developed in the TBC specimen during the heating or cooling period of a shock test, and the initiation of surface cracking is related to larger tensile stress due to a larger temperature gradient across ZrO2 layer during cooling The maximum cooling rate was measured just after laser beam-off, so this examines the burst in acoustic emission that occurred during cooling At low laser powers AE events almost were observed during each cycle of the test, indicate that the vertical cracking was initiated on the surface and progressed toward heat-affected zone steadily At high laser power (>80W), the specimens are subjected to a larger transient thermal stress upon cooling, and the interface delamination resulted from different opening (Mode-I) and shearing deformation (Mode-II) which was consistent with the results of waveform simulation As the transient stress is proportional to temperature gradient, the No.3 specimen suffered more serious degradation than the No.1 and specimens These results revealed that the cracking and delamination had a tendency to occur in the thick ZrO2 From the AE counts and crack volume values, it is postulated that the specimens with or without a bond coating have different cracking characteristics Typically the No and specimens have a ZrO2 layer with the same thickness, but large number of Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authoriz 206 NONTRADITIONALMETHODS OF SENSING STRESS/STRAIN AE events with large crack volumes were emitted in the No.2 specimen without a bond coating It is sure that the bond coating has little influence on transient temperature in the sample, for its thermal properties are comparable to those of the substrate Therefore, the change in AE features is ascribed to the role of the bond coating in relieving transient stress The interface temperature was measured over 650~ corresponding to laser power in excess of 50W, which is in the range of the brittle/ductile transition temperature (BDTT) of NiCoCrA1Y bond layer [9] Consequently, the thermal stress induced by the laser irradiation was partially released by a ductile deformation of the bond coating, and reduce cracking tendency in the specimens Conclusions Plasma sprayed thermal barrier coatings with different thickness and structures were subjected to cyclic laser irradiation, and their sequent fracture progression and dynamics determined by an acoustic emission source inversion processing The major conclusions from the results include: The majority of acoustic signals were emitted during the early cooling period of the cycles, and cracking was monitored during most of the cycles when laser power is over 30W Due to the delamination and rapid propagation of vertical cracks, the severity of coating failure increased with increasing laser power over 70W, especially after the formation of a melted zone in the irradiated ZrO2 coating Mode-I fracture was identified as the predominant fracture type corresponding to vertical cracking, and Mode-II fracture occurred after Mode-I fracture initiated in the thick TBC or at the thin ZrO2 layer/bond interface The tendency to cracking and delamination increased with increasing thickness of the ZrO2 coating due to a built-up of high transient temperature gradient, but further application of a bond coating reduced the coating damage through a mechanism of thermal stress relief Acknowledgment This work was supported by Japan Society for the Promotion of Sciences and Ministry of Culture and Education References [1] Miller, R A., "Current Status of Thermal Barrier Coatings-An Overview," Surface Coat Technol., Vol 30, No 1, 1987, pp 1-11 [2] Sims, C T., "Non-Metallic Materials for Gas Turbine Engines-Are They Real?," Adv.MaterProcess., Vol 139, 1991, pp 32-39 [3] Miller, R A., "Oxidation Based Model for Thermal Barrier Coating Life," J.Am.Cera.Soc., Vol 67, No 8, 1984, pp 517-526 [4] Cruse, T A., Stewart, S E and Ortiz, M., "Thermal Barrier Coating Life Predication Model Development," d.Eng Gas Turbines Power, Vol 110, 1988, pp 610-616 Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized MA AND TAKEMOTO ON CYCLIC LASER IRRADIATION 207 [5] Wadley, H N G and Scruby, C B., "Acoustic Emission Source Characterization," Advances in Acoustic Emission," Dunegan, H L and Hartman, W F., Eds., Dunhart Publishers, Knoxville, 1981, pp 125 [6] Ohtsu, M and Ono, K., "Generalized Theory of Acoustic Emission and Green's Function in a Half Space," J.Acoustic Emission, Vol 3, No 1, 1984, pp 27-40 [7] Takemoto, M and Hayasi, Y., "Microkinetics of Hydrogen Assisted Cracking by Inverse Processing of Acoustic Emission," J Chemical Engineering Japan, Vol 24, No 6, 1991, pp 778-783 [8] Takemoto, M., Suzuki, H and Ono, K., "The Fracture Dynamics in a Dissipative Glass-Fiber/Epoxy Model Composite With AE Source Simulation Analysis," J.Acoustic Emisssion, Vol 14, No 1, 1996, pp 35-50 [9] Nicoll, A R., "A Survey of Methods Used for the Performance Evaluation of High Temperature Coatings," Coatings for High Temperature Applications, Lang, E., Ed., Elsevier Applied Science Publishers, Netherlands, 1983, pp 269-339 Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Panel Discussion Summary Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further r STP 1323-EB/Apr 2001 Current Status and Future Sensor Development: Panel Discussion Summary A panel discussion was conducted for an hour following the symposium presentations consisted of the following individuals: 9 9 The panel Prof Michael A Sutton - University of South Carolina Pros Shiping Chen - University of Maryland Ms Joy S Ransom - Fatigue Technology Inc Dr Peter C McKeighan - Southwest Research Institute The function of the panel participants was to help guide the discussion and instigate audience participation Toward this end, a series of questions were first posed to the audience These questions and some of the audience/panel response are summarized below: What standards activities can be undertaken to transition methods from "laboratory techniques" to more applicable "industrial techniques"? 9 ASTM Standards on new systems will make it easier for industry to accept results or developments from new sensor systems However if ASTM were to specify particular systems, it may stifle creativity concerning design of new or improved systems Rather than specifying systems, the process of developing a sensor needs to be described In order to achieve ASTM action, a committed person is required who wants the standard and can see the process through to completion in two to three years While guiding the process, this individual would need to overcome a variety of technological and political issues What A S T M Standard considerations are necessary to i m p l e m e n t new sensors into accepted methods as alternatives to the traditional methods already adopted? 9 9 Standards are typically written or modified when people are performing similar tests and not achieving the same answer A major question that needs to be overcome is: "How can people have faith in home-built systems?" Industry needs standards that enable calibration of these types of home-built systems to add credence to the development process and demonstrate through some well-defined method that reliable data can be generated using the system However there are serious obstacles to calibration standards For instance, how we calibrate new visual measurement systems? With the many visual measurement methods available, how results of these systems compare both with each other as well as with currently available systems? It may turn out that some nontraditionaI sensors may be un-ealibratable For example, video systems have many variables and an enormous number of degrees of freedom not well suited to conventional calibration A standard guide for non-contacting methods is needed for starters; with a definition of terms t ~Editors Note: Since this symposium was held, the standard practice entitled Standard Guide for Evaluating Non-Contacting Optical Strain Measurement Systems has been balloted and approved by ASTM membership This document will be included in the next publishing of the ASTM standards Copyright by ASTM Int'l (all rights reserved); Wed Dec 211 23 19:45:13 EST 2015 Downloaded/printed by www.astm.org Copyright 9of2001 by ASTM Intemational University Washington (University of Washington) pursuant to License Agreement No further reproductions autho 212 NONTRADITIONALMETHODS OF SENSING STRESS/STRAIN What will be needed to take current developments of these new sensors to ensure they are viable, generally useful and economically available for use in laboratory or other applications? 9 The amount of funding available for basic research is currently limited and shows no sign of becoming more available Obviously this makes it harder to implement new systems into existing laboratories If industry is aware o f an existing technology, it has the potential to he integrated However the basic problem remains: how does industry become aware of a technological development? In this sense ASTM can help by sponsoring symposia such as this that act to make users more aware of the technologies that are available for sensors In the early 1970's the Air Force funded a process of standard development that led to E647, the standard commonly used for fatigue crack growth rate measurement It would be useful if the government once again saw the importance of funding standards development What new methods / technique / sensing strategy has yet to realize its full potential in terms of nontraditional sensing? 9 A new area to examine is how damage is defined (fracture mechanics based?) and what methods can be used to find this damage This in essence could drive subsequent design methods We need a standard that can be used to validate data, albeit some type of new image or other technology People will misuse technology if they not understand it, or make improper decisions based on unknowns in the technology if not given some appropriate guidance ASTM needs proactive and fruitful liaisons to other committees, for example the SEM Experimental Mechanics Group or VAMAS or ISO organization Although these linkages exist, it is difficult for excellent informatinn/technology sharing to occur when the personnel involved are not intimalely aware of what the Sensor group within ASTM E08 is doing potential applications, not yet addressed with nontraditional methods, are expected to be in the f u t u r e ? W h a t is t h e p r i m a r y r o a d b l o c k to t h i s happening and what can we in the technical community about i t ? What 9 9 9 9 We need a database of ideas and technology that are out there Harmonic magnetic resonance (HMR) and eddy current probes to look for damage ahead of cracks New optical methods to measure stress and strain without sensors on specimen surface Sensing of chemical species using some kind of molecular imprinted polymers Molecular computing - send current through molecules sensing changes of structure This method requires measurement sensors on the sub-pico level Better and more capable software for sensors Sensing small cracks and differentiating between plastic strain and damage There is no generalized computerized technology that allows interpreting the behavior of real structure Work needs to he done to develop strategies to sense changes in actual structure and hence recognize damage to prevent failure before it occurs One of the major roadblocks is that the small amount of available funding is tightening up and little basic research money is available Government needs to commit to incur some risk so that they can assist in developing new techniques What are the potential funding avenues for s e n s o r / t e c h n i q u e development? Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further repr PANEL DISCUSSION SUMMARY 9 213 Government-aided SBIR programs are available for development work Advancements in technologies like ceramics are driving alternate sensor techniques There are big hurdles to overcome economic factors Industry needs new applications that require using new, more advanced and special sensor techniques Alternatively, additional government monies are required to assist in new sensor development ~md insure that new tools are available for the next scientific advances What is the role of: universities, government labs, private industry (large concerns and start-ups) in developing and commercializing new nontraditional sensors? * 9 Universities need to push new technology into their undergraduate teaching so that the technology, is available for companies when they hire fresh engineers from school The university role is for the transfer of technical information and new sensor strategies Getting into new techniques is a huge challenge for private industry and independent labs who, by their basic business nature, can not leverage the technological advance into product uniqueness Government labs need additional funding to develop and use new systems This will hasten the transfer of the new systems to industry SBIR/STTR funding bridges the gap between university and high tech companies We need to identify these companies and partnerships Other General Comments * Small businesses not know what new-tech stuff is out there ASTM assists in our knowing by sponsoring symposia such as this Nevertheless, the question remains: How can we get the information presented here into our own facilities and how we tap into the brains of people who can help us develop these resources? A solution to getting the information to the right people would be for ASTM members to post problems, perhaps on a website Other people, perhaps researchers at Universities or other engineers, can then examine these postings and recommend solutions based upon their experience This is a method that marries the source of the problem to the person that can help solve the problem Perhaps somebody like ASTM could sponsor this type of forum and method of collaboration Small businesses with the ability to develop and rapidly advance new technology are the major driving force in sensor technology development But these new high tech companies are not going to tell you what they have until they are selling the product This is one reason why it is so important to insure that government funding is involved with the creation of these sensors or strategies This will mitigate the ownership issue by insuring that all have access to the new methods/sensors Joy S Ransom Fatigue Technology Inc Seattle, WA Symposium co-chair and editor Peter C McKeighan Southwest Research Institute San Antonio, TX Symposium co-chair and editor Copyright by ASTM Int'l (all rights reserved); Wed Dec 23 19:45:13 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized