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Elevated temperature fatigue crack growth in alloy 718. I. Effects of mechanical variables
Fatigue Abstracts An interactive program for fatigue check of steel highway bridges. Hasegawa,
Y. and Mori, T. Hosei Daigaku Kogakubu Kenkyu Shubu (Bulletin of the College of Engineering, Hosei University) (Mar 1993) (29), 187-200 (in Japanese) Much fatigue damage has appeared in steel highway bridges, which shows the necessity of a rational method and convenient tool for fatigue checking. An interactive program developed for checking the safety of steel highway bridges against fatigue, and estimating fatigue life and remaining life easily, is introduced. This program consists of three subprograms. The first analyses the stress variations caused by passing of various vehicles, the second determines fatigue allowable stress based on the Recommendation for Fatigue Design Method of Japanese Society of Steel Construction, and the last checks the safety by comparison of the stress variations with the allowable stress. Graphs, 13 ref. Proposal of new fatigue life evaluation procedure for steel structural details antler variable-amplitude str--c~es. Mori, T. and Hayashi, N.
Hosei Daigaku Kogakubu Kenkyu Shubu (Bulletin of the College of Engineering, Hosei University) (Mar 1993) (29), 159-173 (in Japanese) Fatigue crack propagation analyses for typical steel structural details are performed under various types of variable-amplitude stresses which may approximately express the stresses in various steel structures. On the basis of the analytical results, the relationship between threshold stress range to give the fatigue damage and the degree of fatigue damage is verified. By combining the relationship with the linear damage conception, a new procedure is proposed to predict the fatigue life under variable-amplitude stresses. Fatigue life estimated by the new procedure is compared with that predicted by previous procedures such as Miner's law, modified Miner's law, Haibach's procedure, etc. Graphs, 11 ref. Statistical analyses of variability/reproducibility of environmentally-assisted cyclic crack growth rate data relative to AK control modes. Tsu]i, H.,
Yokoyama, N., and Kondo, T. J Nucl Mater (June 1993) 202 (1-2), 79-86 Statistical analyses were conducted by using the cyclic crack growth rate data for pressure vessel steels, i.e. SA533B-1 and SA508-2, stored in the JAERI Material Performance Database (JMPD); and comparisons were made on variability and/or reproducibility of the data obtained by AK-increasing and by AK-constant type tests. Based on the results of the statistical analyses, it was concluded that AK-constant type tests are generally superior to the commonly used AK-increasing type tests from the viewpoint of variability and/or reproducibility of the data. Such a tendency was more pronounced in the tests conducted in simulated LWR primary coolants than in those in air. Graphs, 12 ref. The gel electrode revisited: fatigue crack detection with a polymer film. Baxter,
WJ. ASTM J Test Eval (May 1993) 21 (3), 168-173 The gel electrode provides a very sensitive technique for detecting and imaging fatigue cracks in metals. In the past, its utility has been restricted by the requirement that, prior to the formation of a crack, the metal surface must be anodized to form a thin insulating film. This film is ruptured as a crack forms, so that an impressed current from a gel electrode flows preferentially to the crack and forms an image. The anodic film has been replaced by a cathodically deposited polymer film. This film is much easier to apply, is applicable to any metal, and can be applied either before or after crack formation. If applied prior to fatigue loading, it is ruptured in the same manner as an anodic film, but it provides much better insulation, so that freshly formed cracks can now be detected in materials such as cast irons. If applied after fatigue loading, the film does not cover up the previously formed cracks so that the gel electrode current still flows preferentially to the crack. Both sequences of application are illustrated by images of fatigue cracks in low-carbon steel (SAE 1008), modular iron, and austempered ductile iron. The only difficulty experienced has been with previously formed cracks held tightly closed by retained compressive stresses. Otherwise, this combination of polymer film and the gel electrode will detect cracks as small as 0.3 mm in length. Graphs, photomicrographs, 8 ref. Axial-torsional fatigue: a study of tubular specimen thickness effects. Bonacuse,
P.J. and Kalluri, S. ASTM J Test Eval (May 1993) 21 (3), 160-167 A room-temperature experimental programme was conducted on AISI type 316 stainless steel to determine the effect of wall thickness on the cyclic deformation behaviour and fatigue life of thin-wall, tubular, axial-torsional fatigue specimens. The following experimental variables were examined: the depth of the surface work-hardened layer produced in specimen machining, and the effects of strain range and axial-torsional strain phasing. Tubular fatigue specimens were fabricated with wall thicknesses of 1.5, 2.0 and 2.5 ram. One as-fabricated specimen from each wall thickness was sectioned for microstructural examination and microhardness measurement. A specimen of each wall thickness was tested at each of three conditions - high strain range in-phase, low strain range in-phase, and low strain range out-of-phasefor a total of nine axial-torsional fatigue experiments. Little or no variation in the fatigue life or deformation behaviour as a function of wall thickness was observed. The machining-induced work-hardened zone, as a percentage of the gauge section material, was found to have a minimal effect on both deformation behaviour and fatigue life. Out-of-phase fatigue tests displayed shorter fatigue lives and more cyclic hardening than in-phase tests. Numeric data, photomicrographs, graphs, 6 ref.
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Fatigue, 1994, Vol 16, June
The design of a control system for a superimposed frequency fatigue test machine. Stoten, D.P. and Smith, DJ. ASTM J Test Eval (May 1993) 21 (3), 154-159 The conjoint action of high- and low-frequency fatigue on a test specimen; i.e. steel, has been obtained using a servohydraulic test machine. A control strategy was implemented such that only one servo-actuator was required to obtain both low- and high-frequency components. The test rig and the decoupled automatic controller developed for it are described. Test results show that the decoupled strategy synthesis produces satisfactory separation of the low- and high-frequency modes of the closed-loop response. Graphs, spectra, 7 ref. Fatigue of steel bolts having dual phase mixed structures. Fuliki, S.
Tokyo Konye Kaisuz Centa, Kenkyu Hoko (Report of the Tokyo Metropolitan Industrial Technology Center) (Mar 1993) (22)11-14 (in Japanese) Fatigue of steel (SCM435) bolts consisting of mixed dual phases and single phase was studied under completely reversed tension and compression. Although a heat-treated bolt after thread rolling showed similar fatigue strength between the dual phases and the single phase at low cycles, the dual-phase bolt showed longer life than that of the single phase at high cycles. The optimum fatigue strength was obtained on the structure of 30 vol% ferrite and 70 vol% trostite. A thread-rolled bolt after heat treatment improved on the fatigue strength at N cycles. The fatigue life was dependent on the matrix structure, which involved the ratio of volume fraction of each phase and the difference of transformed phases. The bolt consisting of 30 vol% ferrite and 70 vol% martensite showed the longest life under the experiment. Graphs, 6 ref. A design method for avoiding fatigue failure of large Francis turbine runner.
Huang, Y.H. Wang, D.J. Jian, T., Mi, Y.D. and Zhong, S. Jixie Gongcheng Xuebao (Chinese Journal of Mechanical Engineering) (Feb. 1993) 29 (1), 58-65, 89 (in Chinese) According to the complicated conditions and specific environment of a large Francis turbine, a comprehensive design method for avoiding fatigue failure is proposed. The method, which makes use of the theories of random fatigue and corrosion fatigue, is based on a large number of statistical data and fatigue experiments. The determination of design load spectrum, fatigue characteristics of the materials in corrosive environment, various factors affecting fatigue strength, and ways of calculating service life and safety factor are included. The results would supersede the static design method of the turbine and can more efficiently evaluate the safety of the turbine against fatigue failure in design or in service. Graphs, 13 rcf. Elevated temperature fatigue crack growth in alloy 718. I. Effects of mechanical variables. Ghonem, H., Nicholas, T. and Pineau, A. Fatigue Fract Eng mater Struct (May 1993) 16 (5), 565-576 The effects of mechanical variables on the crack growth process in alloy 718 are reviewed and analysed on the basis of the related deformation characteristics in the crack-tip region. The variables included temperature, frequency, wave shape, hold time, load ratio and load interaction. These analyses have suggested that the role of each parameter in the acceleration of crack tip damage is governed mainly by their relative influence on the nature of the corresponding plastic deformation and associated slip-line density. On the basis of this view (which assumes that crack growth damage covers the range from cyclic to fully time-dependent processes), the interactive effects of loading parameters are discussed when considering the corresponding fracture mode. Conflicting experimental observations under different operating conditions are examined. Graphs, 38 ref. The influence of load misalignment during uniaxinl low-cycle fatigue testing. I. Modemng. Kandil, F.A. and Dyson, B.F. Fatigue Fract Eng Mater Struct (May 1993) 16 (5), 509-527 A quantitative model has been proposed which predicts the extent of lifetime scatter in low-cycle fatigue due to the influence of bending caused by load misalignment. The main components of the model are the mechanism of bending, the type of extensometer used to control strain and the fatigue characteristics of the material being assessed. Three mechanisms of bending have been studied and it is argued that the most damaging one is a consequence of a lateral offset in the centre-lines of the load-train with respect to either a machine's frame or ram. Scatter in lifetime is a maximum when strain is controlled by a single extensometer (which is generally the case) and when fatigue behaviour is dictated by crack initiation at the largest surface defect. Two types of scatter have been examined: (i) repeatability scatter due to testing practice within a single laboratory, and (ii) reproducibility scatter between laboratories. An example of the magnitude of reproducibility scatter due to bending has been given by using an equation based on the universal slopes method due to Manson. Graphs, 28 ref. The influence of load misafignment during uninxinl low-cycle fatigue testing. II. Applications. Kandil, F.A. and Dyson, B.F. Fatigue Fract Eng Mater Struct (May 1993) 16 (5), 529-537 Models for predicting scatter bands due to bending have been applied to four alloys, AISI 316L, Nimonic 101, 9Cr-lMo, and IN718. The alloys were tested extensively by 26 laboratories in an international round robin exercise sponsored by the Community Bureau of Reference (BCR) of the EC. After initially selecting data for analysis on the basis of their confirmed conformance to the ASTM bending criterion, it has been shown that in all four materials a major fraction of the data scatter could be attributed to bending. Furthermore, at the lowest strain range, the predicted bending component
Y. and Mori, T. Hosei Daigaku Kogakubu Kenkyu Shubu (Bulletin of the College of Engineering, Hosei University) (Mar 1993) (29), 187-200 (in Japanese) Much fatigue damage has appeared in steel highway bridges, which shows the necessity of a rational method and convenient tool for fatigue checking. An interactive program developed for checking the safety of steel highway bridges against fatigue, and estimating fatigue life and remaining life easily, is introduced. This program consists of three subprograms. The first analyses the stress variations caused by passing of various vehicles, the second determines fatigue allowable stress based on the Recommendation for Fatigue Design Method of Japanese Society of Steel Construction, and the last checks the safety by comparison of the stress variations with the allowable stress. Graphs, 13 ref. Proposal of new fatigue life evaluation procedure for steel structural details antler variable-amplitude str--c~es. Mori, T. and Hayashi, N.
Hosei Daigaku Kogakubu Kenkyu Shubu (Bulletin of the College of Engineering, Hosei University) (Mar 1993) (29), 159-173 (in Japanese) Fatigue crack propagation analyses for typical steel structural details are performed under various types of variable-amplitude stresses which may approximately express the stresses in various steel structures. On the basis of the analytical results, the relationship between threshold stress range to give the fatigue damage and the degree of fatigue damage is verified. By combining the relationship with the linear damage conception, a new procedure is proposed to predict the fatigue life under variable-amplitude stresses. Fatigue life estimated by the new procedure is compared with that predicted by previous procedures such as Miner's law, modified Miner's law, Haibach's procedure, etc. Graphs, 11 ref. Statistical analyses of variability/reproducibility of environmentally-assisted cyclic crack growth rate data relative to AK control modes. Tsu]i, H.,
Yokoyama, N., and Kondo, T. J Nucl Mater (June 1993) 202 (1-2), 79-86 Statistical analyses were conducted by using the cyclic crack growth rate data for pressure vessel steels, i.e. SA533B-1 and SA508-2, stored in the JAERI Material Performance Database (JMPD); and comparisons were made on variability and/or reproducibility of the data obtained by AK-increasing and by AK-constant type tests. Based on the results of the statistical analyses, it was concluded that AK-constant type tests are generally superior to the commonly used AK-increasing type tests from the viewpoint of variability and/or reproducibility of the data. Such a tendency was more pronounced in the tests conducted in simulated LWR primary coolants than in those in air. Graphs, 12 ref. The gel electrode revisited: fatigue crack detection with a polymer film. Baxter,
WJ. ASTM J Test Eval (May 1993) 21 (3), 168-173 The gel electrode provides a very sensitive technique for detecting and imaging fatigue cracks in metals. In the past, its utility has been restricted by the requirement that, prior to the formation of a crack, the metal surface must be anodized to form a thin insulating film. This film is ruptured as a crack forms, so that an impressed current from a gel electrode flows preferentially to the crack and forms an image. The anodic film has been replaced by a cathodically deposited polymer film. This film is much easier to apply, is applicable to any metal, and can be applied either before or after crack formation. If applied prior to fatigue loading, it is ruptured in the same manner as an anodic film, but it provides much better insulation, so that freshly formed cracks can now be detected in materials such as cast irons. If applied after fatigue loading, the film does not cover up the previously formed cracks so that the gel electrode current still flows preferentially to the crack. Both sequences of application are illustrated by images of fatigue cracks in low-carbon steel (SAE 1008), modular iron, and austempered ductile iron. The only difficulty experienced has been with previously formed cracks held tightly closed by retained compressive stresses. Otherwise, this combination of polymer film and the gel electrode will detect cracks as small as 0.3 mm in length. Graphs, photomicrographs, 8 ref. Axial-torsional fatigue: a study of tubular specimen thickness effects. Bonacuse,
P.J. and Kalluri, S. ASTM J Test Eval (May 1993) 21 (3), 160-167 A room-temperature experimental programme was conducted on AISI type 316 stainless steel to determine the effect of wall thickness on the cyclic deformation behaviour and fatigue life of thin-wall, tubular, axial-torsional fatigue specimens. The following experimental variables were examined: the depth of the surface work-hardened layer produced in specimen machining, and the effects of strain range and axial-torsional strain phasing. Tubular fatigue specimens were fabricated with wall thicknesses of 1.5, 2.0 and 2.5 ram. One as-fabricated specimen from each wall thickness was sectioned for microstructural examination and microhardness measurement. A specimen of each wall thickness was tested at each of three conditions - high strain range in-phase, low strain range in-phase, and low strain range out-of-phasefor a total of nine axial-torsional fatigue experiments. Little or no variation in the fatigue life or deformation behaviour as a function of wall thickness was observed. The machining-induced work-hardened zone, as a percentage of the gauge section material, was found to have a minimal effect on both deformation behaviour and fatigue life. Out-of-phase fatigue tests displayed shorter fatigue lives and more cyclic hardening than in-phase tests. Numeric data, photomicrographs, graphs, 6 ref.
300
Fatigue, 1994, Vol 16, June
The design of a control system for a superimposed frequency fatigue test machine. Stoten, D.P. and Smith, DJ. ASTM J Test Eval (May 1993) 21 (3), 154-159 The conjoint action of high- and low-frequency fatigue on a test specimen; i.e. steel, has been obtained using a servohydraulic test machine. A control strategy was implemented such that only one servo-actuator was required to obtain both low- and high-frequency components. The test rig and the decoupled automatic controller developed for it are described. Test results show that the decoupled strategy synthesis produces satisfactory separation of the low- and high-frequency modes of the closed-loop response. Graphs, spectra, 7 ref. Fatigue of steel bolts having dual phase mixed structures. Fuliki, S.
Tokyo Konye Kaisuz Centa, Kenkyu Hoko (Report of the Tokyo Metropolitan Industrial Technology Center) (Mar 1993) (22)11-14 (in Japanese) Fatigue of steel (SCM435) bolts consisting of mixed dual phases and single phase was studied under completely reversed tension and compression. Although a heat-treated bolt after thread rolling showed similar fatigue strength between the dual phases and the single phase at low cycles, the dual-phase bolt showed longer life than that of the single phase at high cycles. The optimum fatigue strength was obtained on the structure of 30 vol% ferrite and 70 vol% trostite. A thread-rolled bolt after heat treatment improved on the fatigue strength at N cycles. The fatigue life was dependent on the matrix structure, which involved the ratio of volume fraction of each phase and the difference of transformed phases. The bolt consisting of 30 vol% ferrite and 70 vol% martensite showed the longest life under the experiment. Graphs, 6 ref. A design method for avoiding fatigue failure of large Francis turbine runner.
Huang, Y.H. Wang, D.J. Jian, T., Mi, Y.D. and Zhong, S. Jixie Gongcheng Xuebao (Chinese Journal of Mechanical Engineering) (Feb. 1993) 29 (1), 58-65, 89 (in Chinese) According to the complicated conditions and specific environment of a large Francis turbine, a comprehensive design method for avoiding fatigue failure is proposed. The method, which makes use of the theories of random fatigue and corrosion fatigue, is based on a large number of statistical data and fatigue experiments. The determination of design load spectrum, fatigue characteristics of the materials in corrosive environment, various factors affecting fatigue strength, and ways of calculating service life and safety factor are included. The results would supersede the static design method of the turbine and can more efficiently evaluate the safety of the turbine against fatigue failure in design or in service. Graphs, 13 rcf. Elevated temperature fatigue crack growth in alloy 718. I. Effects of mechanical variables. Ghonem, H., Nicholas, T. and Pineau, A. Fatigue Fract Eng mater Struct (May 1993) 16 (5), 565-576 The effects of mechanical variables on the crack growth process in alloy 718 are reviewed and analysed on the basis of the related deformation characteristics in the crack-tip region. The variables included temperature, frequency, wave shape, hold time, load ratio and load interaction. These analyses have suggested that the role of each parameter in the acceleration of crack tip damage is governed mainly by their relative influence on the nature of the corresponding plastic deformation and associated slip-line density. On the basis of this view (which assumes that crack growth damage covers the range from cyclic to fully time-dependent processes), the interactive effects of loading parameters are discussed when considering the corresponding fracture mode. Conflicting experimental observations under different operating conditions are examined. Graphs, 38 ref. The influence of load misalignment during uniaxinl low-cycle fatigue testing. I. Modemng. Kandil, F.A. and Dyson, B.F. Fatigue Fract Eng Mater Struct (May 1993) 16 (5), 509-527 A quantitative model has been proposed which predicts the extent of lifetime scatter in low-cycle fatigue due to the influence of bending caused by load misalignment. The main components of the model are the mechanism of bending, the type of extensometer used to control strain and the fatigue characteristics of the material being assessed. Three mechanisms of bending have been studied and it is argued that the most damaging one is a consequence of a lateral offset in the centre-lines of the load-train with respect to either a machine's frame or ram. Scatter in lifetime is a maximum when strain is controlled by a single extensometer (which is generally the case) and when fatigue behaviour is dictated by crack initiation at the largest surface defect. Two types of scatter have been examined: (i) repeatability scatter due to testing practice within a single laboratory, and (ii) reproducibility scatter between laboratories. An example of the magnitude of reproducibility scatter due to bending has been given by using an equation based on the universal slopes method due to Manson. Graphs, 28 ref. The influence of load misafignment during uninxinl low-cycle fatigue testing. II. Applications. Kandil, F.A. and Dyson, B.F. Fatigue Fract Eng Mater Struct (May 1993) 16 (5), 529-537 Models for predicting scatter bands due to bending have been applied to four alloys, AISI 316L, Nimonic 101, 9Cr-lMo, and IN718. The alloys were tested extensively by 26 laboratories in an international round robin exercise sponsored by the Community Bureau of Reference (BCR) of the EC. After initially selecting data for analysis on the basis of their confirmed conformance to the ASTM bending criterion, it has been shown that in all four materials a major fraction of the data scatter could be attributed to bending. Furthermore, at the lowest strain range, the predicted bending component