STP 1092 Applications of Automation Technology to Fatigue and Fracture Testing Arthur A Braun, Noel E Ashbaugh, and Fraser M Smith, editors Library of Congress Cataloging-in-Publication Data Applications of automation technology to fatigue and fracture testing! Arthur A Braun, Noel E Ashbaugh, and Fraser M Smith, editors (STP: 1092) Papers presented at a symposium held in Kansas City, Missouri, 22-23 May 1989, sponsored by ASTM Committees E9 on Fatigue and E24 on Fracture Testing "ASTM publication code number (PCN) 04-0l0920-30"-T.p verso Includes bibliographical references and index ISBN 0-8031-1401-X /' Materials-FatigueTesting-Congresses MaterialsFracture- Testing-Congresses I Braun, Arthur A., 1953 II Ashbaugh, Noel E., 1940 III Smith, Fraser M., 1959IV ASTM Committee E9 on Fatigue V ASTM Committee E24 on Fracture Testing VI Series: ASTM special technical publication; 1092 TA418.38.A66 1990 90-43922 620.1'126-dc20 CIP Copyright © 1990 by the American Society for Testing and Materials All rights reserved No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher NOTE The Society is not responsible, as a body, for the statements and opinions advanced in this publication 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 of time and effort on behalf of ASTM Printed in Ann Arbor, MI November 1990 Foreword The papers in this publication, Applications of Automation Technology to Fatigue and Fracture Testing, were presented at a symposium held in Kansas City, Missouri, 22-23 May 1989 The symposium was sponsored by ASTM Committees E9 on Fatigue and E24 on Fracture Testing Arthur A Braun, MTS Systems Corporation, Noel E Ashbaugh, University of Dayton, and Fraser M Smith, Sarcos Research Corporation, presided as cochairmen of the symposium and are coeditors of this publication Contents ~ SYSTEMS IMPLEMENTATION A Computer-Controlled Automated Test System for Fatigue and Fracture TestingRANDY JOHN K NANSTAD, T HUTTON, DAVID ALEXANDER, AND DAVID RONALD L SWAIN, L THOMAS A PC-Based Data Acquisition System for Composite Material Fracture Testing-GLENN E COLVIN, JR., AND STEPHEN R SWANSON 21 A Test System for Computer Controlled Theromechanical Fatigue TestingWENDELL B JONES, DAVID T SCHMALE, 38 AND ROY J BOURCIER Fatigue and Fracture Testing Using a Multitasking Minicomputer WorkstationPETER c McKEIGHAN, RONALD D EVANS, AND BEN M HILLBERRY Dedicated Microprocessor-Based Controller for Fatigue Testing-R SUNDER 52 AND 68 C S VENKATESH A Semiautomated Computer-Interactive Dynamic Impact Testing SystemDAVID JOHN J ALEXANDER, RANDY K NANSTAD, WILLIAM R CORWIN, AND 83 T HUTTON A Fracture Mechanics Test Automation System for a Basic Research LaboratoryGEORGE A HARTMAN AND NOEL ANALYSIS E ASHBAUGH 95 AND SIMULATION Simulation of Mechanical and Environmental Conditions in Fatigue Crack Growth Testing-JOSSI SOLIN AND JUKKA HA YRYNEN 113 ApPLICATIONS Fatigue Crack-Growth Measurement Using Digital Image Analysis TechniqueALEX S REDNER, ARKADY S VOLOSHIN, AND ARVIND NAGAR l-R Curve Testing Utilizing the Reversing Direct Current Electrical Potential Method-VALERIO BICEGO, DINO LlVIERO, CARLO FOSSATI, AND ENRICO LUCON Automated Variable-Amplitude KEITH DONALD 133 Drop 143 Fatigue Crack Growth Technology167 Use of Computer Systems in High- Temperature JAMES c EARTHMAN Crack Growth Studies178 Use of Automated Ball Indentation Testing to Measure Flow Properties and Estimate Fracture Toughness in Metallic Materials-FAHMY M HAGGAG, RANDY K NANSTAD, JOHN T HUTTON, DAVID L THOMAS, AND RONALD L SWAIN Discussion 188 207 LABORATORY SYSTEMSAND INFORMATIONMANAGEMENT Automation Software for a Materials Testing LaboratorY-MIcHAEL PETER J BONACUSE A MeGAWAND 211 Automated Fatigue and Fracture Laboratory with Multiple Load Frames and Single Host Computer System-R SUNDER 232 Collection and Evaluation of Fatigue and Fracture Mechanics Data According to the European High Temperature Materials Databank (Petten) StandardHANS-HELMUTOVER AND BRUNO BUCHMAYR 250 A Data Acquisition and Control Program for Axial-Torsional SREERAMESH KALLURI AND PETER J BONACUSE 269 Fatigue Testing- INDEXES Author Index 291 Subject Index 293 Overview The continuing advancement of computer and software technology has allowed for the automation of materials testing systems and processes to become commonplace Automation, which was at first a very expensive and complicated accessory to a materials testing system, is now a inexpensive and often necessary subsystem Many test techniques now require the speed, consistency, and computational capability inherent in these systems Hardware cost~ have continued to spiral downward in conjunction with incredible increases in computational bandwidth, dispiay technology performance, and mass storage capacity and speed Software technology, the real key to forward progress, has improved significantly, allowing for shorter application development time with higher application performance This is especially true in the area of real-time systems software which is critical for testing system control and data acquisition This symposium is the third in a series of symposia concerned with the advancement of the state of the art in automated fatigue and fracture testing The first was the Use of Computers in the Fatigue Laboratory held in New Orleans, Louisiana in November of 1975 The proceedings were published in STP 613 The second symposium on this topic was entitled Automated Test Methods for Fracture and Fatigue Crack Growth held in Pittsburgh, Pennsylvania during the Fall E9/E24 meeting in November of 1983 The proceedings of this symposium were published in STP 877 This current symposium was organized in order to conduct a state of the art review of the technology The symposium was driven by the work of the task group E9.04.01 on Automated Testing which is a task group of the E9 committee on Fatigue and its' subcommittee on Apparatus and Test Methods The intent of this task group is to conduct such a technology review on a three to four year time interval thus keeping pace with the rapid advances in computing and software engineering technology as they apply to fatigue and fracture testing There are a number of areas where automation technology enhances fatigue and fracture testing The emphasis of this symposium was placed upon the issues of test system implementation, test techniques, applications of networking and information management within a testing laboratory, control and data acquisition techniques, and applications or implementations where the computer provided enhanced analysis or simulation capability These areas of interest were selected to focus on tasks in the fatigue and fracture testing process that reside at different levels within this process Automated systems implementation and test techniques are closest to the actual tasks of acquiring materials property data In this arena, concerns are primarily on compute bandwidth and real-time software efficiency Fatigue and fracture tests, being dynamic tests, require higher data acquisition and compute bandwidth than many common real-time systems possess The task of determining the crack length in a fatigue-crack growth test via the compliance technique for example requires data acquisition speed, simultaneity, and compute speed for online crack length calculations from resultant compliance data Often the testing task requires parallelism in the system implementation to allow for control, data acquisition, and online conditional processing to be performed in the course of the test This requires multitasking executive software or highly efficient single tasking environments that allow for prioritized interrupt driven system services or polling implementations with sufficient speed to handle all of the tasks at hand A number of systems implementation oriented papers were presented in the first session of the symposium The range of solutions AUTOMATION IN FATIGUE AND FRACTURE TESTING was broad It should be noted that the hardware options ranged from simple personal computers to multitasking engineering workstations The Colvin and Swanson paper on "The Development of a Low Cost PC-Based Data Acquisition System" epitomized the trend toward using cost effective yet high performance personal computers to automate mechanical tests At the other end of the spectrum; McKeighan and Hillberry's paper on "Fatigue and Fracture Testing Using a Multitasking Minicomputer Workstation" is an example of the use of a high-performance engineering workstation where the benefits of using a multitasking executive greatly enhance the utility of such a system in the laboratory by allowing, for example, analysis and network transactions to be performed concurrently with a executing test The next level of application, which is actually a step back from the hardware and software details, revolves around the utilization of the technology to allow a new or unique technique to be developed Fatigue-crack growth near threshold testing may be performed manually without computer automation but with the aid of automation, the system efficiency, test repeatability, and data quality are enhanced significantly The determination of lIe can be a rather arduous chore when using multiple specimens and non automated analysis techniques The computer controlled single specimen adaptation of this test is a much less labor intensive task and is the norm for this fracture toughness test The paper by Bicego et al illustrates the state of the art for this test and the computer automation that is becoming is integral to this test The natural extrapolation of all of this as performance in hardware and software increases is the ability to perform true calculated variable control tests where a calculated parameter either directly or via a cascade control approach is used to maintain some specimen condition Taking yet another step back from the testing system and the local testing techniques leaves one in the laboratory environment A key to competitive success be it in the research laboratory or the industrial design allowables laboratory is in the ability to take the results from automation enhanced testing instruments and rapidly and efficiently analyze the raw data and make these results available to the design function, test requestor, manufacturing organization, materials supplier or materials user Integration of the testing laboratory with the rest of a given organization is becoming a very important consideration Organizing test results and materials data into easily accessed formats and making this information accessible are the key issues The technologies through which this is accomplished are networking, database technology, Laboratory Information Management Systems (LIMS), and common access and analysis applications software These concepts were addressed in the last session of the symposium The paper by McGaw and Bonacuse and the paper by Sunder illustrate the trend to tie all of the testing automation subsystems within a test laboratory together via a network to facilitate the rapid movement of test information and results to points accessible by other segments of an organization This scenario will become more common with time The paper by Over and Buchmayr is concerned with the difficult task of organizing materials data in a database and then providing the tools to allow for easy access to the information As database software technology improves and the tools for data extraction improve (via the standardization of query tools such as SQL-structured query language), the sharing of materials data will be enhanced thus reducing replication of test work or allowing for more critical experimental work to be carried out To summarize, this symposium and the resultant proceedings are intended to provide an update on the applications of automation across the field of computer assisted fatigue and fracture testing It is the intention of the Automation task group in E9 to revisit this area every three to four years to keep track of the utilization of advancing hardware and software technology Further advances in artificial intelligence, advanced software development tools, direct digital control, networking technology, and information management systems will OVERVIEW promote new test capability and test techniques and allow for further efficiencies to be obtained in the process of materials characterization Integration of testing laboratories with manufacturing, materials development, inspection capability, and the design functions via automation technology will enhance structural reliability and shorten time to market for new products The symposium cochairmen would like to acknowledge the efforts of all the authors and the ASTM staff members which made the symposium and the resultant publication possible Arthur A Braun MTS Systems Corporation, Minneapolis, MN 55424; symposium cochairman and coeditor Randy K Nanstad,l David J Alexander, Ronald L Swain, John T Hutton,2 and David L Thomas2 A Computer-Controlled Automated Test System for Fatigue and Fracture Testing REFERENCE: Nanstad, R K., Alexander, D J., Swain, R L., Hutton, J T., and Thomas, D L., "A Computer-Controlled Automated Test System for Fatigue and Fracture Testing," Applications of Automation Technolo!?y to Fatigue and Fracture Testing, ASTM STP 1092, A A Braun, N E Ashbaugh, and F M Smith, Eds., American Society for Testing and Materials, Philadelphia, 1990, pp 7-20 ABSTRACT: A computer-controlled system consisting of a servo hydraulic test machine, an in-house designed test controller, and a desktop computer has been developed for performing automated fracture toughness and fatigue crack growth testing both in the laboratory and in hot cells for remote testing of irradiated specimens Both unloading compliance and dc-potential drop can be used to monitor crack growth The test controller includes a dc-current supply programmer, a function generator for driving the servohydraulic test machine to required test outputs, five measurement channels (each consisting of low-pass filter, track/hold amplifier, and 16-bit analog-to-digital converter), and digital logic for various control and data multiplexing functions The test controller connects to the computer via a 16-bit wide photoisolated bidirectional bus The computer, a Hewlett-Packard Series 200/300, inputs specimen and test parameters from the operator, configures the test controller, stores test data from the test controller in memory, does preliminary analysis during the test, and records sensor calibrations, specimen and test parameters, and test data on flexible diskette for later recall and analysis with measured initial and final crack length information During the test, the operator can change test parameters as necessary KEY WORDS: computers, fatigue (materials), crack growth, fracture toughness, test controller, compliance, dc-potential, J"integral, multichannel test controller, J-R curve, analogto-digital converter, photo-isolation, complementary metal oxide semiconductor, clip gage, automation, interface, fracture testing, fatigue testing The automation of materials testing equipment is certainly not a recent concept Researchers have applied various degrees of automation over the years with the general objectives of increasing productivity, efficiency, and consistency The advent of desktop laboratory computer systems capable of machine control and data acquisition was the real catalyst in this area, and the result has been an explosion of computer automation This is evident from the relatively narrow technical field for which this symposium was developed The applications for computer automation span the entire range of technology The characteristics of automated systems are as diverse as the applications, reflecting the particular needs of the user Some are hard, dedicated, inflexible systems that perform precisely the same set of tasks for every operation, while others have a high degree of flexibility and adaptability The needs of the fracture and fatigue testing community span that range The I Group leader, metallurgical engineer, and principal technologist, respectively, Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6151 Development engineer and instrument technician, respectively, Instrumentation and Controls Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6151 AUTOMATION IN FATIGUE AND FRACTURE TESTING rapid evolution of sophisticated desktop computers, peripheral devices, and other electronic hardware, in terms of speed and memory capacity, has likewise allowed for increasingly greater flexibility and capability in the software for test control, data acquisition, storage, and analysis The Fracture Mechanics Group of the Metals and Ceramics Division at Oak Ridge National Laboratory (ORNL) began a computer automation activity in 1978 for the purpose of conducting elastic-plastic fracture mechanics tests The system has evolved markedly since then, particularly in terms of speed The need for test control and rapid data acquisition during fatigue crack growth testing spurred the development of a high-speed, multichannel test controller This paper describes the computer-automated system, test and analysis procedures, and some test results Background Automated testing for evaluation of fracture resistance was largely spurred by developments in elastic-plastic fracture mechanics Starting with the concept of the I-integral by Rice [1] and the description of a practical means for estimating I versus crack extension in test specimens by Rice et al [2], the advantages of computer involvement were apparent It was the development of the unloading compliance test method [3], however, that forced the incorporation of computers in test systems The unloading compliance test procedure requires excellent test control, high-precision data acquisition capability, and rapid calculation The use of computers for automated unloading compliance testing has been described by a number of researchers [4-6] Although the unloading compliance technique is an accepted procedure for determining lIe and I resistance (I-R) curves in ASTM standards, obtaining accurate and consistent test results is not an easy task Because the unloading compliance technique involves a fairly large number of periodic unloading cycles, usually with a hold period at the start of each cycle to allow for load relaxation in the system, the testing time can be on the order of h In many instances, especially those involving remote testing for irradiated specimens in a hot cell, the high expense of facilities and equipment mandate that all feasible reductions in testing time be effected Because the unloading compliance test requires high-precision measurements of displacement during each unloading cycle, the extensometer (usually a clip-on displacement gage) is very important The extensometer must be carefully calibrated and must be seated in such a way that effects of error sources such as friction and vibration are minimized Testing at low and high temperatures adds temperature shifts in extensometer calibration as another source of error The ability to accurately infer crack length without resorting to unloading the specimen (with the associated extensometer and sources of error) has made the dc-potential drop (dc-pd) method for determining the crack length a widely used technique for both fracture mechanics (I-R) [4] and fatigue crack growth (FCG) [7] tests Dc-pd is an important aspect of the testing system and analysis procedures described herein Description of Test System Figure shows a block diagram of the major components of the interactive fracture mechanics test system The computer is a Hewlett-Packard Series 200/300 with MB of random-access memory and Hewlett-Packard technical BASIC operating system and runs a 1.024-MB test control/data acquisition and analysis program developed in-house specifically for this application The computer connects to the test controller via a 16-bit-wide photo-isolated bidirectional control/data bus The test controller (prototype shown in Fig 2) includes a dc-current programmer for controlling a Kepco Model ATE6-100M power supply operated in current-regulation mode, a ramp and sine output function generator for KAllURI AND BONACUSE ON AXIAL-TORSIONAL FATIGUE TESTING 279 yield strengths and the specimen geometry constants generated for the specified test temperature Limiting the axial and torsional loads to about 25% of the respective estimated yield strengths, ensures that no plastic deformation occurs in the specimen during the determination of the elastic moduli The elastic modulus determination is performed under load control with triangular waveforms A schematic illustration of the waveform used for the elastic loadings is shown in Fig The 12-bit D/ A converter is capable of analog output values ranging from -10 to + 10 V with a resolution of part in 4096 The elastic moduli procedure is programmed to calculate the digital equivalents of the previously computed axial and torsional load limits The waveforms are divided into 500 increments each, with the time interval between each increment controlled by a PIT interrupt The PIT is set to operate at a frequency of kHz Thus, if the frequency of the waveform of loading is 0.1 Hz, and the waveform has 500 increments; the interval between each PIT interrupt is 20 ms (20 PIT cycles) At each increment of loading, the digital value of the waveform is computed by the procedure, and the corresponding analog value is output by the D/ A converter to the appropriate servocontroller At the same time, the program resets the AID multiplexer to the first channel and proceeds to take data sequentially on six channels Because the interval is small between conversions (about 17 floS per conversion), data from all six channels are considered to be acquired simultaneously As shown in Fig 7, the axial loading is applied first Once the axial elastic waveform is applied to the specimen, a linear regression is performed on the acquired axial stress and strain data to determine the Young's modulus At this stage, the procedure is repeated with the torsional waveform of loading, to determine the shear modulus The axial and torsional load, strain, and stroke data acquired by this procedure are stored in the elastic compliance data file In addition, the elastic moduli can be checked to ensure that the axial-torsional test system is performing as desired, so that the axial-torsional fatigue experiment can be started with confidence After the elastic moduli have been successfully determined, the input for the axial-torsional fatigue experiment is queried by another procedure The software allows the user to perform the axial-torsional fatigue experiment either in load or strain control The amplitudes, the type of waveforms (triangular or sinusoidal), the frequency, and the phase difference, if any, between the axial and torsional command waveforms are entered into the program The phase difference between the axial and the torsional waveforms can vary from to 90° The digital equivalents of the axial and torsional amplitudes are then computed by the 280 AUTOMATION IN FATIGUE AND FRACTURE TESTING software At this stage, all the specifications of the axial-torsional fatigue test and the results from the elastic moduli experiment are written concisely to a test specification file on the hard disk An example of the test specification file is shown in Table The fatigue test control procedure also initiates a separate task that writes the data collected from the axial and torsional load, strain, and stroke channels to a fatigue data file (Fig 6) Figure shows a flow diagram that depicts the execution of the axial-torsional fatigue experiment At the beginning of the experiment, the PIT is initialized and the DI A and AID are cleared If a phase difference between the axial and torsional waveforms of loading is specified, the axial waveform is ramped to create the required initial phase angle The amplitudes of both the axial and torsional waveforms are then gradually increased over a TABLE 3-Axial-torsional fatigue test specification file NAME OF THE ENGINEER: PETE AND RAMESH MATERIAL AND SPECIMEN NUMBER: HAST-X No.8 COMPLIANCE CHECK DATA FILE NAME: HXLEMOD.DAT FATIGUE DATA FILE NAME: HX8.DAT AMBIENT TEMPERATURE = 23.0 C TEST TEMPERATURE = 800.0 C MEAN VALUE OF ALPHA = 0.00001600 [mm/mm/C] THE FOLLOWING VALUES WERE COMPUTED AT TEST TEMPERATURE INNER RADIUS = 11.190 [mm] OUTER RADIUS = 13.161 [mm] MEAN RADIUS = 12.175 [mm] CROSS SECTIONAL AREA TORSIONAL MOMENT OF INERTIA = 150.797 [mm**2] = 22499.900 [mm**4] ELASTIC COMPLIANCE DATA ESTIMATED AXIAL YIELD STRENGTH ELASTIC MODULUS REGRESSION COEFF SHEAR MODULUS REGRESSION COEFF = 230.0 [MPa] = 149.503 [GPa] = 0.99818 = 53.187 [GPa] = 0.99970 CONSTANT RATE FATIGUE DATA CONTROL MODE - STRAIN AXIAL CONDITIONER SETTINGS: LOAD :2 STRAIN : STROKE: TORSIONAL CONDITIONER SETTINGS: LOAD :2 STRAIN : STROKE: AXIAL STRAIN LIMITS TORSIONAL STRAIN LIMITS AXIAL STRAIN RATE TORSIONAL STRAIN RATE AXIAL VOLTAGE LIMITS TORSIONAL VOLTAGE LIMITS PHASE ANGLE TRIANGULAR WAVEFORM FREQUENCY = = = = = = = = + I - 0.00250 + I - 0.00433 0.00100 [/see] 0.00173 [I see] + I - 1.255 + I - 2.070 TEST STARTED: Friday January 13, 1989 10:35:07 AM, LAST CYCLE = 1500 0.00 [Degrees] 0.20 [Hz] period of five cycles to the full amplitudes required by the test This experimental technique prevents the extenso meter from slipping out of the indentations in the specimen However, these five cycles are not counted towards the fatigue life of the specimen and no data are collected during this portion of the experiment In both triangular and sinusoidal types of waveforms, the axial and torsional cycles are divided into 500 increments The PIT is used to create the required time interval between two successive digital output increments These digital outputs from the minicomputer are fed to the DI A converters, the output of which is used as command signals for the axial and torsional servocontrollers The digital data are collected from the axial and torsional load, strain, and stroke in a multitasking mode These data are collected continuously during the first 10 cycles and logarithmically thereafter At the beginning of a test, an array is generated that contains the cycle numbers for which the data are to be stored The data are continuously acquired for every cycle during the axial-torsional fatigue experiment and stored alternatingly in two data arrays If the data from a particular cycle are required to be saved, then they are transferred from the data array to a permanent data file on the hard disk in a compact format during the test Two data arrays are utilized so that one array can be used to store the data while the data in the second array are being transferred to the hard disk If the data of a particular cycle are not required to be saved, then the data stored in the data arrays are written over by data acquired in subsequent cycles If the test is required to be paused for surface replication, the execution of the test-control and data acquisition software is periodically halted after a predetermined number of cycles If no interruption is specified, the test continues until the specimen fails The test program can be also interrupted at any moment from the computer keyboard The axial-torsional fatigue test control software has a programmed specimen failure detection scheme If the 282 AUTOMATION IN FATIGUE AND FRACTURE TESTING difference between the command digital signal and the feedback digital signal of either the axial or torsional control channel exceed a programmed limit, then the test specimen is considered to have failed, and the generation of the axial and torsional command waveforms is terminated The data from the last two fatigue cycles are transferred from the data arrays to the compact data file Finally, the digital data stored in the compact format are unpacked and converted into engineering units These data are finally written to a fatigue data file in ASCII format The execution ofthe axial-torsional fatigue test control software is terminated after all of the data are transferred to an ASCII data file A portion of data from the fatigue data file is shown in Table Each axial-torsional fatigue cycle is stored in an array of 500 by elements The first three columns contain the data from the axial load, strain, and stroke channels; and the next three columns contain the corresponding data from the torsional channels The seventh column contains a time stamp for the data in each row At the end of the axial-torsional fatigue experiment, the data are transferred from the minicomputer to the superminicomputer for archiving The data are then transferred cycle by cycle, to desk-top microcomputers, and they are analyzed with commercially available data analysis packages The axial-torsional fatigue test software described meets all four of the requirements discussed earlier in this report Applications of the Axial-Torsional Test-Control Software The axial-torsional test control and data acquisition software described in this report was utilized in two separate programs To date, only in-phase isothermal axial-torsional fatigue testing has been performed with this software However, an isothermal axial-torsional experimental program involving both in-phase and out-of-phase fatigue tests is in progress The results of some of the experiments conducted with the software are presented in this section In-phase axial-torsional fatigue tests were conducted on 304 stainless steel at room temperature in strain control as part of a round-robin program initiated by the ASTM task group on multiaxial fatigue research Fatigue tests with and without surface replication pauses were conducted with the software [11] The axial and torsional hysteresis loops of one of the tests are presented in Fig These hysteresis loops are constructed from the data collected with the software for a near half-life cycle Figure also shows "cross-plots" of the axial strain versus torsional strain and axial stress versus torsional stress for the same TABLE 4-Example of data stored in axial-torsional fatigue data file Axial Data Torsional Data Stress, MPa Stroke, mm Stress, MPa Strain Stroke, deg Time, Strain -192.0 -192.3 -192.7 - 193.4 -193.0 -193.0 - 193.4 -192.7 -192.7 -192.3 - 0.00171 -0.00175 - 0.00175 -0.00177 - 0.00178 - 0.00180 -0.00179 - 0.00179 -0.00180 -0.00178 -0.0310 -0.1550 - 0.2791 -0.2480 -0.2170 - 0.0620 -0.0310 - 0.1240 -0.2170 -0.2170 - 104.4 - 104.4 - 104.4 - 104.4 - 103.5 - 102.9 -lOLl -98.7 -97.2 -96.0 - 0.00299 -0.00301 - 0.00305 - 0.00304 - 0.00306 - 0.00305 -0.00302 - 0.00299 -0.00296 -0.00294 -0.6348 -0.8789 - 0.6470 -0.9277 - 0.8789 - 0.8423 -0.9033 -0.7690 -0.7690 -0.9033 655.00 655.01 655.02 655.03 655.04 655.05 655.06 655.07 655.08 655.09 s KALLURI AND BONACUSE ON AXIAL-TORSIONAL FATIGUE TESTING 283 284 AUTOMATION IN FATIGUE AND FRACTURE TESTING cycle If the axial strain and torsional strain feedback signals are in-phase, then a cross-plot would show no hysteresis However, it is interesting to note that the axial strain and torsional strain feedback signals are slightly out-of-phase even though the axial and torsional strain command signals were in-phase This is, most likely, due to the small differences in the gains of the axial and torsional servocontrollers The cross-plot of axial stress versus torsional stress exhibits substantial hysteresis compared with the cross-plot of axial strain versus torsional strain This can be attributed to the large amount of inelastic deformation occurring in the specimen The data acquired from the axial-torsional fatigue test software allow these comparisons to be made with relative ease The hardening-softening curves for the axial and torsional stresses are shown in Fig 10 for the same in-phase axial-torsional fatigue test The software presented in this report was developed mainly for controlling and acquiring data from out-of-phase axial-torsional fatigue experiments with any given phase difference between and 90° However, this software can also be utilized to conduct out-of-phase axial-torsional deformation experiments to characterize the constitutive behavior of a material under biaxial conditions Such experiments were conducted by Kanazawa et al [13] on 1Cr-Mo- V steel to study the flow behavior of that material The test control and data acquisition for such out-of-phase axial-torsional deformation experiments would be simplified substantially by the software package described in this paper In the second program, the Young's modulus and the shear modulus were determined at different temperatures for Hastelloy X This is a nickel-base superalloy that is used as a combustor liner material in gas turbine engines A single specimen was used to generate the moduli at 100°C increments starting with the room temperature At each temperature, the axial-torsional fatigue test-control software was initialized, and the elastic modulus determination procedure was executed The results (Fig 11) are in close agreement with the data available for this superalloy [14] Strain-controlled, in-phase axial-torsional fatigue experiments were also conducted on Hastelloy X at 800°C The axial and torsional hysteresis loops from one of the in-phase axial-torsional fatigue experiments on Hastelloy X at 800°C are presented in Fig 12 The hardening-softening curves for the axial and torsional stresses are shown in Fig 13 for the same fatigue test The axial-torsional test-control and data acquisition software presented in this report simplifies the procedures for conducting complex axial-torsional fatigue experiments In addition, it acquires the data from these experiments in a format that eases some of the KAlLURI AND BONACUSE ON AXIAL-TORSIONAL FATIGUE TESTING 285 burden on the data analyst, and it also allows some analysis that would be cumbersome, if not impossible, with data acquired from traditional experimental techniques The axial-torsional test-control and data acquisition software presented in this report is intended primarily for isothermal, continuous-cycling, in-phase and out-of-phase fatigue experiments Clearly, nonisothermal fatigue experiments, such as bithermal and thermomechanical axial-torsional fatigue experiments, would require temperature waveform control For example, in bithermal axial-torsional fatigue experiments [15], the axial and torsional mechanical loading waveforms must be activated at appropriate moments with respect to the temperature waveform The temperature waveform can be controlled by using additional data input and output channels The test-control and data acquisition software will also have to be modifed to perform isothermal creep-fatigue axial-torsional experiments at elevated temperatures Creep strain can be introduced by either a stress-hold or a strain-hold in both axial and torsional directions In order to maintain the synchronization of the axial and torsional waveforms of loading, creep should be introduced at the same time and for the same duration within both waveforms Since creep is time-dependent deformation, the data acquisition rate can be reduced during this portion of the cycle Conclusions A general-purpose computer program to control and acquire data from in-phase and out-of-phase axial-torsional isothermal fatigue experiments has been developed This software has greatly simplified the procedures for conducting axial-torsional fatigue experiments and the analysis of the resulting data The computer program utilizes the multitasking capabilities of the computer system to generate two separate command waveforms and acquire data from six different channels In-phase axial-torsional fatigue experiments were successfully conducted with the computer program on 304 stainless steel at room temperature and on Hastelloy X at 800°C The same computer program can also be used to control and acquire data from inphase and out-of-phase axial-torsional isothermal deformation experiments 286 AUTOMATION IN FATIGUE AND FRACTURE TESTING KAllURI AND BONACUSE ON AXIAL-TORSIONAL FATIGUE TESTING 287 References [i] Brown, M W and Miller, K J., Proceedings, Institution of Mechanical Engineers, Vol 187, No 65/73, 1973, pp 745-755 [2] Krempl, E in The influence of State of Stress on Low-Cycle Fatigue of Structural Materials: A Literature Survey and Interpretive Report, ASTM STP 549, American Society for Testing and Materials, Philadelphia, 1974, pp 1-46 [3] Garud, Y S., Journal of Testing and Evaluation, Vol 9, No.3, May 1981, pp 165-178 [4] Brown, M W and Miller, K J., Journal of Testing and Evaluation, Vol 9, No.4, July 1981, pp 202-208 [5] Lohr, R D and Ellison, E G., Fatigue of Engineering Materials and Structures, Vol 3, 1980, pp 19-37 [6] Penn, R w., Fong, J T., and Kearsley, E A in Use of Computers in the Fatigue Laboratory, ASTM STP 613, H Mindlin and R W Landgraf, Eds., American Society for Testing and Materials, Philadelphia, 1976, pp 78-93 [7] Morrow, J., Fatigue Design Handbook, SAE Advances in Engineering, Vol 4, 1968, pp 21-28 [8] Leese, G E and Morrow, J in Multiaxial Fatigue, ASTM STP 853, Miller and Brown, Eds., American Society for Testing and Materials, Philadelphia, 1985, pp 482-496 [9] Fuchs, H O and Stephens, R I., Metal Fatigue in Engineering, Wiley, New York, 1980, p 29 [10] Bannantine, J A., "Observations of Tension and Torsion Fatigue Cracking Behavior and the Effect on Multiaxial Damage Correlations," University of Illinois at Urbana-Champaign, College of Engineering, Report No 128, July 1986, pp 79-95 [11] Bonacuse, P J and Kalluri, S., "Results of In-phase Axial-Torsional Fatigue Experiments on 304 Stainless Steel," NASA TM-101464, National Aeronautics and Space Administration, Washington, DC, March 1989 [12] McGaw, M A and Bartolotta, P A., Proceedings, Fourth Annual Hostile Environments and High Temperature Measurements Conference, Society for Experimental Mechanics, Inc., Bethel, 1987, pp 12-29 [13] Kanazawa, K., Miller, K J., and Brown, M W., Fatigue of Engineering Materials and Structures, Vol 2, 1979, pp 217-228 [14] "Hastelloy Alloy X," Cabot Wrought Products Division, Cabot Corporation, Kokomo, IN, 1984, pp 1-15 [i5] Halford, G R., McGaw, M A., Bill, R C., and Fanti, P D., Low Cycle Fatigue, ASTM STP 942, Solomon, Halford, Kaisand, and Leis, Eds., American Society for Testing and Materials, Philadelphia, 1988, pp 625-637 Indexes Author Index A K Kalluri, S., 269 Alexander, D J., 7, 83 Ashbaugh, N E., 95 L B Liviero, D., 143 Lucon, E., 143 Bicego, V., 143 Bonacuse, P J., 211, 269 Bourcier, R J., 38 Buchmayr, B., 250 M McGaw, M A., 211 McKeighan, P c., 52 C N Colvin, G E.,Jr., 21 Corwin, W R., 83 Nagar, A., 133 Nanstad, R K., 7, 83,188 D o Donald, J K., 167 Over, H.-H., 250 E R Earthman, J c., 178 Evans, R D., 52 Redner, A S., 133 S F Fossati, Schmale, D T., 38 Solin, J., 113 Sunder, R., 68, 232 Swain, R L., 7, 188 Swanson, S R., 21 c., 143 H Haggag, F M., 188 Hartman, G A., 95 Hayrynen, J., 113 Hillberry, 52 Hutton, J T., 7,83,188 T Thomas, D L., 7, 188 V J Venkatesh, C S., 68 Voloshin, A S., 133 Jones, W B 38 291 Subject Index A data acquisition and control, 269 electric potential drop, 143 European high temperature materials databank 250 high-temperat~re crack growth, 178 microprocessor-based controller, 68 multitasking minicomputer work station, 52 PC-based data acquisition, 21 semiautomated system, 83 single host computer system, 232 software, 95, 211 variable amplitude, 167 Axial-torsional fatigue, 269 Ada, 211 Amplitude loading, 113 Analog-to-?igital converter, AS ME BOIler and Pressure Vessel Code Case N-47, 38 ASTM Standards D 1141-75, 124 D 3039-76(1982), 22 E 23-88, 88, 89 E 184-79, 88 E 399-83, 56, 81 E646-78, 195,200 E 647-83, 121, 123, 125 E 647-88,56,81, 102,237,244 E 647-88a, 134 E 813-81, 199, 260 E 813-87, 56, 153, 156, 260 E 1049-85, 116 STP 613, STP 877, Automated ball indentation testing, 188 Automated data acquisition for composite materials testing, 21 Automated digital analysis technique, 133 Automated fatigue and fracture laboratory schematic, 234 Automated fatigue crack growth testing, 113 Automated materials testing, 52, 178 Automated test system for fatigue and fracture testing, 1, 7, 23 Automated testing, 232 Automated thermo mechanical fatigue testing,38 Automated variable-amplitude, 167 Automatic test control, 52 Automation computer-controlled systems, C Charpy specimens test methods, 83 Clip gage, Closure, 113 Complementary metal oxide semiconductor, Compliance, 7, 113, 167 Composite materials, 21 Compression tests, 38 Computer and software technology in materials testing systems, Computer control, 52, 95 Computer control-automation software, 211 Computer control for simulation of mechanica I and environmental conditions, 113 Computer control program for axial-torsional fatigue testing, 269 Computer controlled fatigue testing, Computer feedback control, 178 Computer programs, 83 Computers, fatigue (materials) testing, 7, 38 Constant-amplitude loading, 232 293 294 AUTOMATION IN FATIGUE AND FRACTURE TESTING Corrosion fatigue, 113 Control program, axial-torsional fatigue testing, 269 Crack growth testing computer controlled system, databank, 250 digital image analysis, 133 electrical potential drop, 143 simulation of mechanical and environmental conditions, 113 single host computer system, 232 Crack length, 133 Creep crack growth, 178 Creep fatigue, 38 Creep (materials), 250 Cyclic loading, 188 D Data acquisition automation software, 211 European high temperature materials databank, 250 multitasking minicomputer workstation, 52 PC-based, 21, 23 Data acquisition for axial-torsional fatigue testing, 269 Data acquisition-system software, 26 Database, 211 dc-potential, Deformation testing, 38, 211 Digital image analysis, 133 Direct measurement, 133 Dynamic impact testing system, 83 E Elastic-plastic fracture mechanics, 8, 143 Electric potential drop, 143, 167 Elevated temperature fatigue, 38, 133 Environmental exposure 113 European high temperature materials databank, 250 F Failure, 188, 269 FALSTAFF, 167 Fatigue and fracture mechanics databank, 250 Fatigue behavior of materials-data acquisition, 269 Fatigue crack growth automated variable-amplitude, 167 fracture mechanics test automation system, 95 measurement using digital analysis, 133 simulation of mechanical and environmental conditions, 113 Fatigue data acquisition, 269 Fatigue life, 113 Fatigue life prediction models, 269 Fatigue materials, 52, 250 Fatigue testing automated ball indentation, 188 automated variable-amplitude, 167 automation software, 211 crack growth, 113, 133 European high temperature materials databank, 250 fracture mechanics test automation, 95 high-temperature crack growth, 178 microprocessor-based controller, 68 multitasking minicomputer workstation, 52 PC-based data acquisition, 21 semiautomated testing system, 83 single host computer system, 232 thermomechanical, 38 Fatigue testing, computer-controlled, Field apparatus, 188 Field indention microprobe apparatus for nondestructive testing, 188 process flow chart, 191 schematic, 190 Flow properties, 188 Fracture mechanics, 95, 250 Fracture testing automated ball indentation, 188 automated variable-amplitude, 167 automation software, 211 axial-torsional fatigue, 269 computer-controlled, crack ,growth, 113, 133 data acquisition and control, 269 digital image analysis, 133 European high temperature materials databank, 250 fracture mechanics test automation system, 95 high-temperature crack growth, 178 microprocessor-based controller, 68 multitasking minrcomputer workstation, 52PC-based data acquisition, 21 INDEXES semi automated testing system, 83 single host computer system, 232 thermomechanical, 38 Fracture toughness, 52, 188 H Heat affected zone, 188 High temperature compression tests, 38 fracture, 178 tension tests, 38 High temperature crack growth experiments schematic of automated testing system, 180 High temperature materials databank, 250 Hysteresis loops, 269 295 Mechanical response of composite materials to loading variety, 21 Mechanical test language, 68 Mechanical testing, 95, 143, 188 Metallic materials fracture toughness testing, 188 Microprocessor-based controller for fatigue testing, 68 schematic, 72 Multiaxial stress and strain-data acquisition,269 Multichannel test controller, Multiple isothermal deformation tests, 38 Multitasking, 269 Multitasking minicomputer workstation materials testing laboratory, 211 schematic, 55 SUN workstation computer, 52 versus microcomputer (PC), 53 I N Image trasmission, 133 In-phase test, 269 Intelligent mechanical test controller (IMTC), 68-82 In situ testing, 188 Interface, Irradiated materials, 83 Irradiated steels, 188 Isothermal deformation tests, 38 Isothermal fatigue, 211 J J-integral, J-R curve, 7, 143 L Laboratory fatigue tests, 38 Networking, 211 Nondestructive testing, 188 o ORNL (Oak Ridge National Laboratory) computer-controlled fatigue and fracture testing systems, Out-of-phase test, 269 p Partial unloading, 188 PASCAL, 211 Personal computer, 21 Petten-European high temperature terials databank, 250 Photo-isolation, ma- R M Material testing, 250 Materials behavior research automation software, 211 Materials databank, 250 Materials testing laboratory automation software, 211 Materials testing systems computer and software technology, 1,7, 95, 178 Measurement applications desk-top computer, 178 Radiation-induced embrittlement nondestructive testing apparatus, 188 Real-time control, 52 S Semiautomated systems design, 84 for dynamic impact testing, 83 Servo hydraulic loadframe, 68 Single host computer system, 232 Software development, 269 296 AUTOMATION IN FATIGUE AND FRACTURE TESTING Software portability, 211 Software technology for automated fatigue and fracture laboratory, 232 for materials testing laboratory, 211 Spectrum fatigue testing, 113 Spectrum loading, 232 Spherical indenter, 188 Stainless steel, 38 Standardization, 250 Strain-controlled LCF data, 38 Stress and strain-data acquisition, 269 System verification, 21 Thermomechanical fatigue, 38, 211 Thesaurus-European high temperature materials databank, 250 Toughness testing automated system, using a multitasking minicomputer workstation, 52 U Uniaxial fatigue, 211 V Variable amplitude, 167 T Tension tests, 38 Test automation, 68, 95 Test controller, Test equipment, 52 Testing systems computer technology, schematic diagram, 43 W Waveform data acquisition strategies, 211 Welds, 188 y Yield strength, 188 ... intended to provide an update on the applications of automation across the field of computer assisted fatigue and fracture testing It is the intention of the Automation task group in E9 to revisit... Overview The continuing advancement of computer and software technology has allowed for the automation of materials testing systems and processes to become commonplace Automation, which was at first... gage, automation, interface, fracture testing, fatigue testing The automation of materials testing equipment is certainly not a recent concept Researchers have applied various degrees of automation