1、NASA TECHNICALMEMORANDUMCOCOIXNASA TM X-3316cAN INVESTIGATION OF FRACTURE TOUGHNESS,FATIGUE-CRACK GROWTH, SUSTAINED-LOADFLAW GROWTH, AND IMPACT PROPERTIESOF THREE PRESSURE VESSEL STEELSC. Michael Hudson, J, C. Newman, Jr.,and Peter E. LewisLangley Research CenterHampton, Va. 23665NATIONAL AERONAUTIC
2、S AND SPACE ADMINISTRATION WASHINGTON, D. C. DECEMBER 1975Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. Report No.NASA TMX-33162. Government Accession No.4. Title and SubtitleAN INVESTIGATION OF FRACTURE TOUGHNESS, FATIGUE-CRACK GROWTH, SUSTAINE
3、D-LOAD FLAW GROWTH, ANDIMPACT PROPERTIES OF THREE PRESSURE VESSEL STEELS7. Author(s)C. Michael Hudson, J. C. Newman, Jr., and Peter E. Lewis9. Performing Organization Name and AddressNASA Langley Research CenterHampton, Va. 2366512. Sponsoring Agency Name and AddressNational Aeronautics and Space Ad
4、ministrationWashington, D.C. 205463. Recipients Catalog No.5. Report DateDecember 19756. Performing Organization Code8. Performing Organization Report No.L- 1044710. Work Unit No.505-02-31-0111. Contract or Grant No.13. Type of Report and Period CoveredTechnical Memorandum14. Sponsoring Agency Code1
5、5. Supplementary Notes16. AbstractTests to determine fracture toughness, fatigue-crack growth, sustained-load flaw growth,and impact properties were conducted on three pressure vessel steels: A. O. Smith VMS 5002and VMS 1146A, and ASTM A- 225 Gr.B. The data obtained will help relieve the general pau
6、-city of such data on these pressure vessel steels.The elastic fracture toughness of the three steels does not decrease significantly withdecreasing temperature from room temperature to about 244 K (-20 F). The elastic fracturetoughness of the three steels increases with increasing specimen width an
7、d thickness.The fatigue- crack-growth data for all three steels fall into relatively narrow scatterbands on plots of rate against stress-intensity range. Barsoms equation (Transactions ASME,Journal of Engineering for Industry, Nov. 1971) predicts the upper bounds of the scatter bandsreasonably well.
8、Charpy impact energies decrease with decreasing temperature in the nominal tempera-ture range from room temperature to 244 K (-20 F).The nil- ductility temperatures of VMS 5002 and A- 225 Gr.B are 250 K (-10 F) and 241 K(-25 F), respectively. A lack of test material precluded obtaining the nil-ducti
9、lity temperatureof VMS 1146A.17. Key Words (Suggested by Author(s)VMS 5002VMS 1146AA- 225 Gr.BFracture toughnessFatigue-crack growth19. Security dassif. (of this report)Unclassified18. Distribution StatementUnclassified UnlimitedSubject Category 2620. Security Classif. (of this page) 21. No. of Page
10、s 22. Price“Unclassified 54 $4.25For sale by the National Technical Information Service, Springfield, Virginia 22161Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-AN INVESTIGATION OF FRACTURE TOUGHNESS, FATIGUE-CRACK GROWTH,SUSTAINED-LOAD FLAW GROWT
11、H, AND IMPACT PROPERTIESOF THREE PRESSURE VESSEL STEELSC. Michael Hudson, J. C. Newman, Jr.,and Peter E. LewisLangley Research CenterSUMMARYTests to determine fracture toughness, fatigue-crack growth, sustained-load flawgrowth, and impact properties were conducted on three pressure vessel steels:A.
12、O. Smith VMS 5002 and VMS 1146A, and ASTM A-225 Gr.B. The data obtained willhelp relieve the general paucity of such data on these pressure vessel steels.The elastic fracture toughness of the three steels does not decrease significantlywith decreasing temperature from room temperature to about 244 K
13、 (-20 F). Theelastic fracture toughness of the three steels increases with increasing specimen widthand thickness.The fatigue-crack-growth data for all three steels fall into relatively narrow scatterbands on plots of rate against stress-intensity range. Barsoms equation (TransactionsASME, Journal o
14、f Engineering for Industry, Nov. 1971) predicts the upper bounds of thescatter bands reasonably well.Charpy impact energies decrease with decreasing temperature in the nominal tem-perature range from room temperature to 244 K (-20 F).The nil-ductility temperatures of VMS 5002 and A-225 Gr.B are 250
15、K (-10 F) and241 K (-25 F), respectively. A lack of test material precluded obtaining the nil-ductilitytemperature of VMS 1146A.INTRODUCTIONThe development of fracture mechanics analysis into a practical tool for predictingthe behavior of cracked structures has precipitated a need for fracture tough
16、ness andfatigue-crack-growth data on many materials. Relatively large quantities of such datahave been generated for materials used for aerospace applications (ref. 1). However,there are relatively few such data on materials used for pressure vessel applications.Consequently, when a fracture mechani
17、cs analysis was recently performed on a series ofProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-pressure vessels at the Langley Research Center, the needed data had to be generated.A series of fracture-toughness and fatigue-crack-growth tests were c
18、onducted onthree pressure vessel steels: A. O. Smith VMS 5002, A. O. Smith VMS 1146A, andASTM A-225 Gr.B. The test temperatures ranged from room temperature to 227 K(-50 F) in the fracture-toughness tests. The test temperature was room temperature inthe fatigue-crack-growth tests.Sustained-load flaw
19、-growth, Charpy impact fracture, and drop-weight impact frac-ture experiments were conducted on the three steels. Properties determined by theseexperiments were also needed in evaluating the integrity of the vessels.This report presents the results of all experiments conducted. The results can beuse
20、d to predict crack growth and failure in these three pressure vessel steels. TheCharpy results are suitable for determining the minimum allowable operating temperaturefor the steels, according to the current ASME Boiler and Pressure Vessel Code (ref. 2).Chicago Bridge Martin Marietta Aerospace(joint
21、ly with LaRC), the fracture-toughness, fatigue-crack-growth, and sustained-loadflaw-growth tests; Martin Marietta Aerospace, the Charpy impact tests; and PittsburghTesting Laboratory, the drop-weight tests.SYMBOLS AND ABBREVIATIONSExcept for the figures, this paper presents physical quantities in bo
22、th the Interna-tional System of Units (SI) and the U.S. Customary Units. For clarity, the figures showonly SI units. All measurements and calculations were made in U.S. Customary Units.Reference 3 presents factors relating the two systems, and appendix A presents thosefactors used in the present inv
23、estigation.a crack length, mm (in.)a crack length at start of fracture-toughness test, mm (in.)asi crack length at start of sustained-load flaw-growth test, mm (in.)CyN energy absorbed in impact test on Charpy V-notch specimen, N-m (ft-lbf)da/dN rate of fatigue-crack growth, nm/cycle (in/cycle)Provi
24、ded by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-e elongation in 51-mm (2-in.) gage length, percentK rate of change of stress intensity factor with time, (MN/m3/2J/sAK stress-intensity-factor range, MN/m / ksi-in / JKp. material fracture-toughness paramete
25、r, MN/m / Vksi-in Kje elastic fracture toughness, MN/m / Vksi-in1/2)KT, elastic stress-intensity factor at start of sustained-load flaw-growth test,MN/m3/2 (ksi-in1/2)maximum stress-intensity factor, MN/m / Vksi-in / jminimum stress-intensity factor, MN/m3/ si-“1 /Ze lateral expansion obtained from
26、Charpy impact test, mm (in.)m material fracture-toughness parameterPo maximum load applied to specimen during fracture-toughness test, N (Ibf)Pm maximum applied load, N (Ibf)?min minimum applied load, N (Ibf)R ratio of minimum stress to maximum stress Sn elastic nominal failure stress, Pa (ksi)Su el
27、astic nominal stress required to produce fully plastic hinge on net section,Pa (ksi)T test temperature, K (F)t specimen thickness, mm (in.)Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-w specimen width, mm (in.)CTU ultimate tensile strength, Pa (ks
28、i)Oy yield strength (0.2-percent offset), Pa (ksi)Abbreviations:COD crack opening displacementCS compact specimen configurationLVDT linear variable differential transformerNDT nil-ductility temperature, K (F)NFG no flaw growth in sustained-load flaw-growth testWOL wedge-opening-load specimen configu
29、rationSPECIMENS, TESTS, AND PROCEDURES .SpecimensTest specimens were made of VMS 5002, VMS 1146A, and A-225 Gr.B ferriticsteels. The VMS 5002 and VMS 1146A are proprietary steels developed by A. O. SmithCorporation for fabricating laminated pressure vessels. The A-225 Gr.B is an ASTMpressure vessel
30、steel (ref. 4). Table I presents the results of the tensile and chemicaltests conducted on the three steels tested in this investigation. The specimens used toobtain the tensile properties met ASTM standards (ref. 5).As mentioned in the Introduction, several laboratories generated the data presented
31、herein. Each laboratory used specimen configurations adaptable to the testing equipmenton hand. Consequently, two, and sometimes three, specimen configurations were testedto determine fracture toughness, fatigue-crack growth, and sustained-load flaw growth.The results of these tests were analyzed by
32、 using the appropriate stress-intensity factorfor each configuration.Fracture-toughness specimens.- Figures 1, 2, and 3 show the configurations of thecompact specimens (CS) tested. The following table gives the configurations, thicknesses,and widths of the various specimens for each material:Provide
33、d by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MaterialVMS 5002VMS 1146 AA-225 Gr.BConfigurationTypeCSCSCSCSCSCSCSCSFigureKa)Kb)Kc)l(a)2l(a)Kb)3Specimenthicknessmm25.445.7109.225.425.425.445.783.8in.1.01.84.31.01.01.01.83.3Specimenwidthmm50.891.471.150.891
34、.450.891.471.1in.2.03.62.82.03.62.03.62.8A chevron notch was machined into each specimen to initiate fatigue cracks. The25.4- and 45.7-mm (1.0- and 1.8-in.) thick specimens met at the ASTM standards (ref. 6)for specimen configuration. The 83.8- and 109.2-mm (3.3- and 4.3-in.) thick specimensdid not
35、meet the ASTM standards; however, a boundary collocation analysis (ref. 7) gavestress-intensity factors for these nonstandard specimens. These factors were used tocalculate the fracture toughness of the specimens at failure.Fatigue-crack-growth specimens.- Figures l(a) and 4 show the configurations
36、of thecompact specimens (CS) tested. The following table gives the thicknesses and widths ofthe specimens:MaterialAll three steelsAll three steels.ConfigurationTypeCSCSFigureKa)4Specimenthicknessmm25.45.1in.1.00.2Specimenwidthmm50.863.5in.2.02.5Chevron and straightthrough notches were machined into
37、the 25.4-mm (1.0-in.)thick and the 5.1-mm (0.2-in.) thick specimens,.respectively, to initiate fatigue cracks.Fine lines scribed on the surfaces of the 25.4-mm (1.0-in.) thick specimens marked inter-vals along the crack path. The spacing between lines was 1.3 mm (0.050 in.). Thesescribe lines provid
38、ed a means of monitoring crack growth but1, being parallel to the loadingdirection, introduced no stress concentration in the specimens. The 5.1-mm (0.2-in.)thick specimens required no scribe lines, because a crack-opening-displacement (COD)gage monitored crack growth. , , .Provided by IHSNot for Re
39、saleNo reproduction or networking permitted without license from IHS-,-,-Sustained-load flaw-growth specimen.- Figures l(a) and 5 show the configurationsof the compact (CS) and wedge-opening-load (WOL) specimens tested. The following tablegives the thicknesses and widths of the specimens:MaterialAll
40、 three steelsVMS 5002 andA-225 Gr.BVMS 1146AConfigurationTypeCSWOLWOLFigureKa)5(a)5(b)Specimenthicknessmm25.435.625.4in.1.01.41.0Specimenwidthmm50.891.491.4in.2.03.63.6Chevron and straight-through notches were machined into the CS and WOL speci-mens, respectively, to initiate fatigue cracks.Charpy i
41、mpact specimens.- Figure 6 shows the configuration of the Charpy impactspecimens tested. These specimens were 55.9 mm (2.2 in.) long and 10.2 mm (0.4 in.)thick. A 2.0-mm (0.08-in.) deep V-notch was cut into the center of each specimen toinitiate failure. This configuration met the ASTM standards (re
42、f. 8) for Charpy impactspecimens. Specimens were machined from all three steels.Drop-weight test specimens.- Figure 7 shows the configuration of the drop-weightspecimens tested. These specimens were 127.0 mm (5.0 in.) long, 50.8 mm (2.0 in.)wide, and 15.7 mm (0.62 in.) thick. A brittle weld bead was
43、 laid in the center of eachspecimen, and a notch cut across the crown of the weld to initiate failure. This config-uration met the ASTM standards (ref. 9) for drop-weight specimens. Specimens weremachined from VMS 5002 and A-225 Gr.B steels.only. A lack of material precludeddrop-weight testing the V
44、MS 1146A.Testing MachinesFracture-toughness testing machines.- The following table lists the capabilities ofthe three testing machines used for the fracture-toughness tests:Machine typeHydraulicHydraulicHydraulicMaximum loadcapacitykN894454448Ibf20 000100 0001 000 000Machine descriptionsourceRef. 10
45、Appendix B. Appendix BProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Fatigue-crack-growth testing machines.- The following table lists the capabilitiesof the two testing machines used for the fatigue-crack-growth tests:Machine typeInertia forcecompe
46、nsationHydraulicMaximum loadcapacitykN89445Ibf20 000100 000Operatingfrequency usedHz205 to 10cpm1200300 to 600Machine descriptionsourceRef. 11Appendix BSustained-load flaw-growth testing machine.- Static loads were applied to the CSspecimens by a tester having a 44-kN (10 000-lbf) static load capaci
47、ty (ref. 12). Staticloads were applied to the WOL specimens by tightening the bolt which is threaded throughthe upper half of the specimen and butts against the lower half. (See fig. 5.)Charpy impact and drop-weight testers.- Standard Charpy impact and drop-weighttesters were used for the impact and
48、 drop-weight tests. References 8 and 9 describe thetest apparatus in detail.Test ProceduresFracture-toughness tests.- Test specimens were fatigue cracked to predeterminedlengths (final a/w values varied from 0.375 to 0.625) by applying constant-amplitudefatigue loadings with R 0 and AK g 0.30KIe. Th
49、is cracking was done at room tem-perature. The specimens were then cooled (if called for in the test program) and monoto-nically loaded to failure at stress-intensity rates K between 0.92 and 2.75 MN/m j/s(,50 and 150 ksi-in /miiy. Throughout each fracture-toughness test a calibrated CODgage was mounted in the machined notch of e
