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A new prediction method of fatigue-creep interaction behavior from a tensile total strain energy viewpoint for high strength superalloy
Crack growth induced b y t h e r m a l - m e c h a n i c a l
Hartman, G.A. and Gallagher, J.P. Exp. Mech. J u n e 1992 32, (2), 1 0 2 - 1 0 8
loading.
John, R.,
Advanced aerospace structures are often subjected to combined thermal and mechanical loads. The fracture mechanics beheviour of these structures may be altered by the thermal state existing around the crack. Hence design of critical structural elements requires the knowledge of stress-intansity factors under both thermal and mechanical loads. The development of an experimental technique to verify the thermal stress-intensity factor generated by a temperature gradient around the crack is described. Thin plate specimens of a model material (AISI-SAE 1095 steel) were used for the heat transfer and thermal-mechanical fracture tests. Rapid thermal loading was achieved using high-intensity focused infrared spot heaters. These heaters were also used to generate controlled temperature rates for heattransfer verification tests. The experimental results indicate that thermal loads can generate stress-intensity factors large enough to induce crack growth. The proposed thermal stress-intensity factors appear to have the same effect as the conventional mechanical stress-intensity factors with respect to fracture. Graphs. 12 refs.
M a c r o p l t t e m o f f a t i g u e - b r o k e n surface o f inclined surface cracks u n d e r blaxlel loading. Zeng, ZJ. and DaL S.-H. Int. J. Pressure Vessels and Piping (1992) 52, (2), 2 0 1 - 2 1 5 The fatigue test scheme and some results for 16MnR steel under the conditions that the biaxisl loading ratio is equal to 0, 0.5 and 1, and the angle of crack inclination is equal to 0°, 30° and 45°, respectively, are reported, with emphasis on the variations in the macro patterns of fatigue-broken surfaces of the surface cracks. This macro pattern may be classified into two categories: in the first category the fatigue-broken surface is smooth and flat, and in the second category it is discontinuous and curved. The present research work suggests that the discontinuity of the fatigue-broken surface of the surface crack is mainly caused by mutual action by mode I and mode III crack driving forces. The variation rule for the mode I and mode III normalized stress intensity factors (SIFs) with the angle of crack inclination and with the biaxial loading ratio is presented. Based on the variation rule of the mode I and mode III normalized SIFs, the variation features of the macro patterns of the fedgue-broken surfaces of inclined surface cracks with the biaxiai loading ratio and with the angle of crack inclination can be explained and predicted. Graphs. 3 refs.
A s t u d y o f f a t i g u e crack g r o w t h in IS-1020 steel u n d e r constanta m p l i t u d e loading. Singh, S.B. and Kumar, R. Int. J. Pressure Vessels and Piping (1992) 52, (2), 177-188 Crack propagation experiments were performed on IS-1020 steel for various load ranges and stress ratios. At constant maximum load, the life of the specimen increased as the load ratio increased. The crack growth data were analysed in terms of &Keff as a function of stress ratio R. The data covered R values of 0, 0.1, 0.2 and 0.3, and a good relation was obtained for U = 0.80-0.3R + 0.15/:/2. A crack growth rate equation was also developed. Aluminum alloys 2024, 2219 and 6063 are discussed. Graphs. 16 refs.
r i c s o f m e l t i n g process for i m p r o v i n g t h e c o n t a c t f a t i g u e life o f
ng steel. Xu, Z ShanghaiJinshu (Shanghai Metals)July 1992 14, (4), 2 9 - 3 2 (in Chinese)
The improvement of contact fatigue life of bearing steel parts by means of improving the melting technologies is reviewed. Graphs. 22 refe.
Influerme o f o r i e n t a t i o n o n t h e f a t i g u e a n d c r e e p b e h a v i o u r o f • single
crystal nickel base superaXoy. Smith, D.J., Shu-Xin, L. and Ellison, G.E. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Rorida, USA, 18-21 May 1992 ( A S M International, Materials Park, Oh, USA, 1992) p p 6 0 3 - 6 0 8 The absence of grain boundaries in single-crystal Ni-bese superalloys leads to material anisotropy which is dependent on crystal orientation. An experimental study was carried out on the single-crystal superalloy SRR99 to examine the mechanical beheviour for different orientations. Smooth bar specimens tested at 950 °C were subjected to fully reversed strain-controlled fatigue-creep cycles for various strain ranges with creep dwells at peak tensile and compressive dwells. It was observed that both the cyclic stress-strain response and fatigue life exhibited an orientation dependence. This dependence is found to be related primarily to the anisotropy based on the elastic properties of the single-crystal superailoy. The elastic modulus for the [111] orientation is larger compared with, eg [001]. Consequently, for tests at the same total strain range, [111J specimens exhibit a higher stress range and also a high inelastic strain range, thereby leading to shorter fatigue lives. It is shown that the orientation dependence of the mechanical beheviour and fatigue life can be described in terms of an orientation function.
Priest, R.H., Cairns, P.M., Gledwin, D.N, and Miller, D.A. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Florida, USA, 18-21 May 1992 ( A S M International,
C r e e p - f a t i g u e i c m m s m e n t o f a w e l d e d steel c o m p o n e n t .
Near-threshold fatigue crack growth b e h a v i o r at h i g h temperatures.
Ohji, K., Kubo, S. and Nakai, Y. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Florida, USA, 18-21 May 1992 ( A S M International, Materials Park, Oh, USA, 1992) pp 3 7 9 - 3 8 8 Fatigue threshold and near-threshold cycle-dependent crack growth behaviour at high temperatures in air was investigated with type 304 stainless steel. An ac electric potential technique was utilized for measuring crack length. Crack growth experiments were made at 650 and 550°C. The threshold J-intagral range (~,Jf)th at 650 °C was lower than that at 550 °C. Above the thresholds crack growth rates were expressed in terms of the J-intagrel range A j or stress intensity range ~K. The character of the threshold for the cycle-dependent crack growth was examined by fatigue crack growth experiments under two-step variable amplitude Ioedings, in which high-range loads were introduced periodically in subthreshold low-range loads. Fatigue cracks were found to grow even at J-intagrai ranges below the threshold value under constant amplitude Ioadings. The estimated crack growth rates (da/dN)Le* under tow-range loads showed that the threshold value decreased by the intermittent introduction of the high-range loads.
S t o e h l l t J e nature on initiation and early g r o w t h c r e e p - f a t i g u e c r i c k i n g . Ohteni, R., Kitamura, T. and
of intergrenuler
Teda, N. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Florida, USA, 18-21 May 1992 ( A S M International,
Materials Park, Oh, USA, 1992) pp 3 6 9 - 3 7 8 The spatial and tamporal scatter of the initiation and early growth of small cracks is attributed to the random distribution of fracture rssistsnce and driving force for each crack caused by the microstructurel inhomogenaity of the material. An intergranular surface cracking is a typical mode of creep-fatigue fracture in polycrystalline steels and alloys at elevated temperatures. A small crack of the size of about one grain boundary facet initiates at a very early stage of fatigue, following the increase in its number and length. The experimental observations conducted mainly on a Type 304 stainless steel were summarized to give evidence of the stochastic nature of crack initiation and early growth. Then, the numerical analysis, which followed a Monte Carlo method based on a simple statistical model of combined damage and fracture mechanics, was performed for characterizing the process of creep fatigue cracking. Emphasis was put on the parameter, Ko/Fo, which was the ratio of the driving force for crack growth to that for crack initiation, to represent the state of cracking.
The influence o f creep on t h e f a t i g u e life o f nickel base l u p l f l i J o y l .
Danzer, R. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Florida, USA, 18-21 May 1992 ( A S M International, Materials Park, Oh, USA, 1992) pp 3 5 9 - 3 5 8
By means of a large set of fatigue tests, performed on several suparelloys, it is shown that fatigue lifetime is given by the material's creep properties, if cyclic inelastic strain is steady state creep (r~- 1 ). In this case, the simple linear life fraction rule for creep damage (AC rule), which needs no adjustable parameter, can be used to calculate fatigue life. For r > 1, the AC rule overestimates fatigue lifetime. This systematic deviation, which increases with the increase of r, is used to define a new rule, which needs one adjustable (empirical) parameter. It is shown that the new rule describes all measured fatigue data fairly well. For obvious reasons, it is restricted to loading situations, where creep still has some influence. These conditions are characterized by r < 10s.
A n e w prediction m e t h o d o f f a t i g u e - c r e e p Interaction b e h a v i o r f r o m a tensile t o t a l strain e n e q l y v i e w p o i n t f o r h i g h stroe~lth s u p e r o b y .
Matsuda, N. and Umezawa, S. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Rorida, USA, 18-21 May 1992 ( A S M International,
Materials Park, Oh, USA, 1992) pp 3 5 1 - 3 5 8 A new life prediction method is proposed for high-strength materiels such as • cast Ni-besed superalloy under fetigue-creep intaraetion (FCI) conditions based on tensile total strain energy beheviour. This new life prediction method is termed 'frequency modified total strain energy parameter'. The total tensile strain energy, including large elastic strain energy and the time under tensile strees loading, is used to define this tensile strain energy parameter, it is found that strain-controlled FCI and cyclic creep failure life prediction can be estimated using this parameter. Creep rupture strength data are plotted using the best-fittad curve of straincontrolled FCI failure life data. Furthermore, not only failure life but also surface crack initiating and propagating behaviour are found to be expressed by this parameter. The surface crack propagation rate is found to be a function of this parameter and surface crack half length. Thus this new life-predlctlon method may be used to determine surface crack propagation beheviour and initiation life.
N o n - p r o p o r t i o n a l m u t i i e x l a l l o w cycle f a t i g u e u s i n g m!u~ifofm specJmen st elevated t e m p e a t u r e . Itch, T., Sakane, M., OhnamL M., TakahashL
Materials Park, Oh, USA, 1992) pp 4 2 3 - 4 2 9
Y. and Ogate, T. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Rorida, USA, 18-21 May 1992 ( A S M International,
Some power-generating components are subject to combined creep and fatigue loading during their service lifetimes. To assess the integrity of such components, Nuclear Electric plc have developed the so-called R5 procedure. The application of R5 to predict the response of Type 316H steel superheater pipework is discussed. An example of service-induced cracking is shown. Finite-element predictions of the service loading, commensurate with the observed cracking mechanism, are described. Ductility exhaustion, as specified in R5, is then used to rationalize the observed incidence of cracking. Features tests are also described. These were mounted to support the creep-fatigue initiation calculations and have revealed some of the likely conservatisms in the R5 method. Finally, the results of laboratory experiments to characterize crack growth response under creep-fatigue conditions are given. These data may be used with the R5 approach to demonstrate the integrity of the pipework in the presence of cracking.
The multisxial low-cycle fatigue under proportional and non-proportional Ioadings was assessed. Proportional and non-proportional low-cycle fatigue tests were carded out using SUS 304 stainless and 1Cr-1Mo-0.25V steel cruciform specimens at high temperatures. Fatigue tests using the cruciform specimens can achieve s wide range of strain multiaxiality which cannot be performed in tansion-torsion tests using hollow cylinder specimens. The Mises' equivalent strain was not effective for correlating the multiaxial low-cycle fatigue lives, while the equivalent strain range based on crack opening displacement was effective for the correlation. Nonproportional loading did not largely reduce fatigue lives for the cruciform specimens which is attributed to the change of the slip direction caused by the non-proportional loading. The crack morphology was extensively discussed from not only the surface crack direction but also the crack inclination into the specimen.
348
Materials Park, Oh, USA, 1992) pp 3 3 1 - 3 3 9
Int J Fatigue July 1993
Hartman, G.A. and Gallagher, J.P. Exp. Mech. J u n e 1992 32, (2), 1 0 2 - 1 0 8
loading.
John, R.,
Advanced aerospace structures are often subjected to combined thermal and mechanical loads. The fracture mechanics beheviour of these structures may be altered by the thermal state existing around the crack. Hence design of critical structural elements requires the knowledge of stress-intansity factors under both thermal and mechanical loads. The development of an experimental technique to verify the thermal stress-intensity factor generated by a temperature gradient around the crack is described. Thin plate specimens of a model material (AISI-SAE 1095 steel) were used for the heat transfer and thermal-mechanical fracture tests. Rapid thermal loading was achieved using high-intensity focused infrared spot heaters. These heaters were also used to generate controlled temperature rates for heattransfer verification tests. The experimental results indicate that thermal loads can generate stress-intensity factors large enough to induce crack growth. The proposed thermal stress-intensity factors appear to have the same effect as the conventional mechanical stress-intensity factors with respect to fracture. Graphs. 12 refs.
M a c r o p l t t e m o f f a t i g u e - b r o k e n surface o f inclined surface cracks u n d e r blaxlel loading. Zeng, ZJ. and DaL S.-H. Int. J. Pressure Vessels and Piping (1992) 52, (2), 2 0 1 - 2 1 5 The fatigue test scheme and some results for 16MnR steel under the conditions that the biaxisl loading ratio is equal to 0, 0.5 and 1, and the angle of crack inclination is equal to 0°, 30° and 45°, respectively, are reported, with emphasis on the variations in the macro patterns of fatigue-broken surfaces of the surface cracks. This macro pattern may be classified into two categories: in the first category the fatigue-broken surface is smooth and flat, and in the second category it is discontinuous and curved. The present research work suggests that the discontinuity of the fatigue-broken surface of the surface crack is mainly caused by mutual action by mode I and mode III crack driving forces. The variation rule for the mode I and mode III normalized stress intensity factors (SIFs) with the angle of crack inclination and with the biaxial loading ratio is presented. Based on the variation rule of the mode I and mode III normalized SIFs, the variation features of the macro patterns of the fedgue-broken surfaces of inclined surface cracks with the biaxiai loading ratio and with the angle of crack inclination can be explained and predicted. Graphs. 3 refs.
A s t u d y o f f a t i g u e crack g r o w t h in IS-1020 steel u n d e r constanta m p l i t u d e loading. Singh, S.B. and Kumar, R. Int. J. Pressure Vessels and Piping (1992) 52, (2), 177-188 Crack propagation experiments were performed on IS-1020 steel for various load ranges and stress ratios. At constant maximum load, the life of the specimen increased as the load ratio increased. The crack growth data were analysed in terms of &Keff as a function of stress ratio R. The data covered R values of 0, 0.1, 0.2 and 0.3, and a good relation was obtained for U = 0.80-0.3R + 0.15/:/2. A crack growth rate equation was also developed. Aluminum alloys 2024, 2219 and 6063 are discussed. Graphs. 16 refs.
r i c s o f m e l t i n g process for i m p r o v i n g t h e c o n t a c t f a t i g u e life o f
ng steel. Xu, Z ShanghaiJinshu (Shanghai Metals)July 1992 14, (4), 2 9 - 3 2 (in Chinese)
The improvement of contact fatigue life of bearing steel parts by means of improving the melting technologies is reviewed. Graphs. 22 refe.
Influerme o f o r i e n t a t i o n o n t h e f a t i g u e a n d c r e e p b e h a v i o u r o f • single
crystal nickel base superaXoy. Smith, D.J., Shu-Xin, L. and Ellison, G.E. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Rorida, USA, 18-21 May 1992 ( A S M International, Materials Park, Oh, USA, 1992) p p 6 0 3 - 6 0 8 The absence of grain boundaries in single-crystal Ni-bese superalloys leads to material anisotropy which is dependent on crystal orientation. An experimental study was carried out on the single-crystal superalloy SRR99 to examine the mechanical beheviour for different orientations. Smooth bar specimens tested at 950 °C were subjected to fully reversed strain-controlled fatigue-creep cycles for various strain ranges with creep dwells at peak tensile and compressive dwells. It was observed that both the cyclic stress-strain response and fatigue life exhibited an orientation dependence. This dependence is found to be related primarily to the anisotropy based on the elastic properties of the single-crystal superailoy. The elastic modulus for the [111] orientation is larger compared with, eg [001]. Consequently, for tests at the same total strain range, [111J specimens exhibit a higher stress range and also a high inelastic strain range, thereby leading to shorter fatigue lives. It is shown that the orientation dependence of the mechanical beheviour and fatigue life can be described in terms of an orientation function.
Priest, R.H., Cairns, P.M., Gledwin, D.N, and Miller, D.A. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Florida, USA, 18-21 May 1992 ( A S M International,
C r e e p - f a t i g u e i c m m s m e n t o f a w e l d e d steel c o m p o n e n t .
Near-threshold fatigue crack growth b e h a v i o r at h i g h temperatures.
Ohji, K., Kubo, S. and Nakai, Y. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Florida, USA, 18-21 May 1992 ( A S M International, Materials Park, Oh, USA, 1992) pp 3 7 9 - 3 8 8 Fatigue threshold and near-threshold cycle-dependent crack growth behaviour at high temperatures in air was investigated with type 304 stainless steel. An ac electric potential technique was utilized for measuring crack length. Crack growth experiments were made at 650 and 550°C. The threshold J-intagral range (~,Jf)th at 650 °C was lower than that at 550 °C. Above the thresholds crack growth rates were expressed in terms of the J-intagrel range A j or stress intensity range ~K. The character of the threshold for the cycle-dependent crack growth was examined by fatigue crack growth experiments under two-step variable amplitude Ioedings, in which high-range loads were introduced periodically in subthreshold low-range loads. Fatigue cracks were found to grow even at J-intagrai ranges below the threshold value under constant amplitude Ioadings. The estimated crack growth rates (da/dN)Le* under tow-range loads showed that the threshold value decreased by the intermittent introduction of the high-range loads.
S t o e h l l t J e nature on initiation and early g r o w t h c r e e p - f a t i g u e c r i c k i n g . Ohteni, R., Kitamura, T. and
of intergrenuler
Teda, N. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Florida, USA, 18-21 May 1992 ( A S M International,
Materials Park, Oh, USA, 1992) pp 3 6 9 - 3 7 8 The spatial and tamporal scatter of the initiation and early growth of small cracks is attributed to the random distribution of fracture rssistsnce and driving force for each crack caused by the microstructurel inhomogenaity of the material. An intergranular surface cracking is a typical mode of creep-fatigue fracture in polycrystalline steels and alloys at elevated temperatures. A small crack of the size of about one grain boundary facet initiates at a very early stage of fatigue, following the increase in its number and length. The experimental observations conducted mainly on a Type 304 stainless steel were summarized to give evidence of the stochastic nature of crack initiation and early growth. Then, the numerical analysis, which followed a Monte Carlo method based on a simple statistical model of combined damage and fracture mechanics, was performed for characterizing the process of creep fatigue cracking. Emphasis was put on the parameter, Ko/Fo, which was the ratio of the driving force for crack growth to that for crack initiation, to represent the state of cracking.
The influence o f creep on t h e f a t i g u e life o f nickel base l u p l f l i J o y l .
Danzer, R. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Florida, USA, 18-21 May 1992 ( A S M International, Materials Park, Oh, USA, 1992) pp 3 5 9 - 3 5 8
By means of a large set of fatigue tests, performed on several suparelloys, it is shown that fatigue lifetime is given by the material's creep properties, if cyclic inelastic strain is steady state creep (r~- 1 ). In this case, the simple linear life fraction rule for creep damage (AC rule), which needs no adjustable parameter, can be used to calculate fatigue life. For r > 1, the AC rule overestimates fatigue lifetime. This systematic deviation, which increases with the increase of r, is used to define a new rule, which needs one adjustable (empirical) parameter. It is shown that the new rule describes all measured fatigue data fairly well. For obvious reasons, it is restricted to loading situations, where creep still has some influence. These conditions are characterized by r < 10s.
A n e w prediction m e t h o d o f f a t i g u e - c r e e p Interaction b e h a v i o r f r o m a tensile t o t a l strain e n e q l y v i e w p o i n t f o r h i g h stroe~lth s u p e r o b y .
Matsuda, N. and Umezawa, S. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Rorida, USA, 18-21 May 1992 ( A S M International,
Materials Park, Oh, USA, 1992) pp 3 5 1 - 3 5 8 A new life prediction method is proposed for high-strength materiels such as • cast Ni-besed superalloy under fetigue-creep intaraetion (FCI) conditions based on tensile total strain energy beheviour. This new life prediction method is termed 'frequency modified total strain energy parameter'. The total tensile strain energy, including large elastic strain energy and the time under tensile strees loading, is used to define this tensile strain energy parameter, it is found that strain-controlled FCI and cyclic creep failure life prediction can be estimated using this parameter. Creep rupture strength data are plotted using the best-fittad curve of straincontrolled FCI failure life data. Furthermore, not only failure life but also surface crack initiating and propagating behaviour are found to be expressed by this parameter. The surface crack propagation rate is found to be a function of this parameter and surface crack half length. Thus this new life-predlctlon method may be used to determine surface crack propagation beheviour and initiation life.
N o n - p r o p o r t i o n a l m u t i i e x l a l l o w cycle f a t i g u e u s i n g m!u~ifofm specJmen st elevated t e m p e a t u r e . Itch, T., Sakane, M., OhnamL M., TakahashL
Materials Park, Oh, USA, 1992) pp 4 2 3 - 4 2 9
Y. and Ogate, T. Proc. Conf. Creep: Characterization, Damage and Life Assessments, Lake Buena Vista, Rorida, USA, 18-21 May 1992 ( A S M International,
Some power-generating components are subject to combined creep and fatigue loading during their service lifetimes. To assess the integrity of such components, Nuclear Electric plc have developed the so-called R5 procedure. The application of R5 to predict the response of Type 316H steel superheater pipework is discussed. An example of service-induced cracking is shown. Finite-element predictions of the service loading, commensurate with the observed cracking mechanism, are described. Ductility exhaustion, as specified in R5, is then used to rationalize the observed incidence of cracking. Features tests are also described. These were mounted to support the creep-fatigue initiation calculations and have revealed some of the likely conservatisms in the R5 method. Finally, the results of laboratory experiments to characterize crack growth response under creep-fatigue conditions are given. These data may be used with the R5 approach to demonstrate the integrity of the pipework in the presence of cracking.
The multisxial low-cycle fatigue under proportional and non-proportional Ioadings was assessed. Proportional and non-proportional low-cycle fatigue tests were carded out using SUS 304 stainless and 1Cr-1Mo-0.25V steel cruciform specimens at high temperatures. Fatigue tests using the cruciform specimens can achieve s wide range of strain multiaxiality which cannot be performed in tansion-torsion tests using hollow cylinder specimens. The Mises' equivalent strain was not effective for correlating the multiaxial low-cycle fatigue lives, while the equivalent strain range based on crack opening displacement was effective for the correlation. Nonproportional loading did not largely reduce fatigue lives for the cruciform specimens which is attributed to the change of the slip direction caused by the non-proportional loading. The crack morphology was extensively discussed from not only the surface crack direction but also the crack inclination into the specimen.
348
Materials Park, Oh, USA, 1992) pp 3 3 1 - 3 3 9
Int J Fatigue July 1993