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Effect of oxide film thickness on the fatigue behaviour of an aluminium-lithium alloy (2090-T8E41)
assess the suitability of the components for further operation. Some results of tests on bolts and castings stressed in long-term operation are presented. The materiels tested were 30CrMoVg, 21CrMoV5 11, XlgCrMoVNbNll 1, and X22CrMoV12 1. Graphs. 11 rofs. metals. Williams, D. ~ hBt Curr. Aware. Bull. Sept. 1989 (193), 1 - 3 Four AFWAL technical reports are reviewed. One of the reports concerns examination of the shot peening process to develop s database from which to develop a mathematical model relating fatigue life to shot peening variables. The metedals tested were 11 different alloys of Ti, AI or steels. Two of the reports concern the feasibility of producing aircraft components by auperplastic forming. The results demonstrated significant savings in cost and weight. This study was performed by Northrup under US Air Force sponsorship. The fourth study, at Rockwell international, concerns superplsstic forming of AI-Li (eg 8091) alloys from aircraft components. Graphs. 4 refs. Rolling contact d e f o r m a t i o n and microstructursl changes in high strength bearing steel. Bhargava, V., Hahn, G. T. and Rubl~n, C. A. Wear Sept. 1989 133, (1), 65-71 The connections between the continuing cyclic plsstic deformation, the etching effects and the fatigue life of high strength bearing steel (eg 52100) under rolling contact were examined. A finite element model is used to calculate the increments of cyclic plastic strain as the roller translates over the running surface. The cyclic plastic strain is related to the plasticity-induced microstructurel changes observed in bearings. The calculations are performed for both elastic linear kinematic hardening plastic and elastic-perfectly plastic materiel beheviours. Observed fatigue lives under rolling contact are compared with the lives obtained in simple cyclic torsion experiments with the same cyclic plastic strain amplitudes. The rotation of the principal shear direction, the smaller strained volume, and the high hydrostatic pressure attending rolling contact may be responsible for the contact lives, which are seven orders of magnitude longer. Graphs. 26 refs.
Propagation o f an inclined subsurface crack in rolling/sliding contact fatigue. Kaneta, M,, Okazaki, T. and Murakami, Y. Key Eng. Mater. 1989 33, 191-212 To elucidate a mechanism of the rolling and/or sliding contact fatigue or wear, the mixed mode three-dimensional stress intensity factors for inclined cracks existing beneath the surface, over which a Hertzian contact pressure accompanied by a surface traction moves, are ceiculsted by taking into account the frictional force between crack faces. A penny shaped or an elliptical crack which is inclined against the direction of, or perpendicular to, the movement of contact load is analysed. Effects of the crack size, the crack depth, the angles of the inclinations, etc. are discussed. Graphs. 39 refs.
Effect o f o x i d e f i l m thickness on t h e f a t i g u e b e h e v i o u r o f an a l u m i n u m - l i t h i u m alloy (2090-TgE41). Tails, J, E. and Mazumdar, P. K. Int. J. Fract. J u l y 1989 40, (3), R67-R71 Oxide film coated on an AI-Li alloy (2090-T8E41) will initially decrease life with thickness and attain its minimum at a critical thickness below 140 nm before indicating an improvement as the oxide becomes thicker. The overall improvement of life with decreasing stress level holds up well with the general stress effect in fatigue, but the life level goes through its minimum at a critical film thickness of approx 50 nm, regardless of the test stress level. Coated and uncoated 2090-T8E41 AI- Li alloy specimens were fatigued under completely reversed tansion-compresslon conditions, ie at a load (= R) ratio of -1. The specimens were then tested for the influence of oxide film thickness on the fatigue behaviour. Graphs. 14 refs. Crack p r o p a g a t i o n in A S T M A516 Grade 70 steel under fatigue loading subjected t o different temperatures, Ukadgaonker, V. G. and Sane, B. G. Int. J. Fract. July 1989 40, (3), R49-R52 The values of C and m in the Paris law, da/dN = C(~K) m, which change with temperature, are determined for ASTM A516 grade 70 steel. The values of m are nearly constant, whereas the values of C change considerably with temperature due to the strain hardening effect. Fatigue crack propagation tests were performed on a 10 tonne MTS universal testing machine for temperatures 23, 75, 150, 225 and 275°C on ASTM A516 grade 70 steel. Graphs. 3 refs. A non-linser high t e m p e r a t u r e fracture mechanics basis f o r strain range partitioning. (Report). Kifamura, T. and Halford, G. R. NASA Tech. Memo. NASA TM-4133 1989, 14 pp A direct link has been established between strain range partitioning (SRP) and hightemperature fracture mechanics by deriving the general SRP inelastic strain range vs. cyclic life relstionships from high-temparsture, non-linear, fracture mechanics considerations. The derived SRP life relationships are in reasonable agreement based on the experience of the SRP behaviour of many high-temperature alloys (304. 316, A286, 2.25Cr-1Mo, Hastelloy X, IN718). in addition, fracture mechanics has served as a basis for derivation of the ductihty-normalized SRP life equations, and for examination of SRP relations that are applicable to thermal fatigue life prediction. Areas of additional links between non-linear fracture mechanics and SRP have been identified for future exploration. These include effects of muitiaxiality and low-strain, nominally elastic, long-life creep-fatigue interaction. Graphs. 47 refs.
Three-dimensional analysis o f t h e surface creck-Hertzlan s U m interaction. (Report). Ballarini, R. and Hsu, Y. NASA Contract. Rap. NASA CR-4254 1989, 157 pp
field
The results of a stress intensity factor analysis of semicircular surface cracks in the inner raceway of a M50 steel engine bearing are presented. The loading consists of a moving spherical Hortzian contact load and an axial stress due to rotation and shrink fit. A three-dimensional linear elastic boundary element method code was developed to perform the stress analysis, The element library includes linear and quadratic isoparametric surface elements. Singular quarter point elements were employed to capture the square root displacement variation and the inverse square
226
root stress singularity along the crack front, The program also possesses the capability to separate the whole domain into two subregions. This procedure enables one to solve non-symmetric fracture mechanics problems without having to separate the crack surfaces a priori. A wide range of conflgumtlon parameters was investigated. The ratio of crack depth to bearing thickness wee veded from one-sixtieth to onefifth for several different locations of the Hertzlan load. The strese intensity factors for several crack inclinations were also investigated. The results demonstrate the efficiency and accuracy of the boundary element method. Moreover, the results can provide the basis for crack growth calcoletions end fatigue life prediction. Graphs. 31 refs. Low-cycle f a t i g u e analysis o f notched members. Zhang, D. and Sandor,
B.I. ASTM J. Test. Eval. J u l y 1989 17, (4), 2 1 2 - 2 1 7 Low-cycle fatigue crack initiation and propagation lives of notched members era investigated. By relating Nd (&J/~p)P = Cn to the Coffin-Mansen equation and correlating to test results, p and Cnare found to be functions of several parameters: cyclic stress-strein constants, goomatw of notch (depth end curvature), and stress ratio. (Ajl~,y) is chosen as a parameter for crack propagation in notched members. Fatigue crack initiation and propagation tests were conducted on notched plate specimens of different notch radii and stress ratios. Crack initiation life, crack propagation life, and total fatigue life are compared with the calculations. There are good correlations between the test results and the calculations. Aluminum alloy 7075 was used. Graphs. 17 refs. Fatigue crack p r o p a g a t i o n in rapidly solidified e l u m i n i u m alloys at 25°C and 3000C. Smith, H. H., Michel, D. J. and Reed, J. R. Metall, Trans. A Nov. 1989 20A, (11), 2425-2430 The fatigue crack propagation performance of two rapidly solidified AI alloys was investigated in air at 25 end 300°C. The results show that the crack propagation rates for continuous cycling tests of AI-8Fe-4Ce and AI-4.7Fe-4.7Ni-0.2Cr alloys were similar at 25~C, Although the crack propagation rates of both alloys were increased at 300°C, the AI-Fe-Ce alloy exhibited the greater resistance to crack propagation. The inclusion of a tensile hold time in the fatigue loading cycle at 300°C to produce an increase in the crack propagation performance of the rapidly solidified alloys was not found to be superior when compared with the fatigue crack propagation performance of a wrought AI alloy tested under the same conditions. Transmission and scanning electron microscopy studies of the tested specimens revealed that the crack propagation mode was primarily transgrsnular, with the metastable disperaoid particles providing impenetrable barriers to dislocation motion. Graphs, photomicrographs. 11 refs. U m i t analysis f o r fiat ends in vessels. Kieswetter, N. Tech. Mech. 1989 10, (1), 3 6 - 4 3 (in German) In the design of vessels the I=mit load is the most important criterion of failure, since there occur mainly static or low cyclic loads and ductile materials. Fatigue analysis is required according to TGL 32903 only for cycle numbers >1000. So that failures possibly caused by this practical rule do not occur, unfevoursble structures must be avoided or designed with such thick walls that at least 1000 cycles can be endured. Such unfevourable structures are flat ends with an adjacent cylindrical shell. Fatigue strains may be reduced by designing fiat ends with corner radius or with a groove. The effects of corner radius and groove for the limit load of flat ends are covered. Using the static and kinematic method, respectively, plate and cylindrical shell with corner radius are at first treated separately end then joined to a complete solution. Examples of H52-3 steel are given. Graphs. 10 refs.
Strain hardening and f a t i g u e o f s i m u l a t e d case microstructurss cerburized steels. Zaccone, M. D., Kelley, J. B. and Krauss, G. Ind. Heat Sept. 1989 56, (9), 38-51
of
The effect of microstructure on high and low cycle fatigue of a series of high carbon (0.8 C) stools was evaluated. In particular, the effect of retained austenite on plastic deformation, strain hardening behaviour, and fracture of tempered martsnsite-austenite composite microstructure was studied. The steels had Cr content of 0, 0.3, 0.6, 0.9, and 1.3 wt.% and other approximate contents of 0.8 C, 0.9 Mn, 0.3 Si, 1.8 Ni, and 0.7 Mo. The retained austenite content varied, generally increasing with increasing content. The steels with the highest Cr contents, and therefore the highest retained austenite contents, had the lowest elastic limits and the lowest strain hardening rates. Tensile flow stresses decreased and plastic strain at fracture increased with increasing amounts of retained austenito. The elastic limit decreased in both compression and tension as retained austanite increased. Graphs, photomicrographs. 17 refs.
Fractography o f AISI 1140 m o d i f i e d steel u n d e r static end cyclic loading conditions. Vecchio, K. S., Hertzberg, R. W. and Schmidt Jr, F. E. ASTM J. Test. Eval. Sept. 1989 1 7 , ( 5 ) , 267-272 The fracture behaviour of modified AISI 1140 rssulphurized steel containing Mn (1.05-1.25%) and sulphur (0.15-0.23%) has been studied under controlled fast fracture and fatigue fracture conditions. 'C'-shepad ring samples were machined from tubes hammer forged at 700°C by the GFM process (Gesellschaft fur Fertigungstechnik und Meschinenbeu (AG) manufactured in Stayr, Austria) so as to develop a highly fibred (axial) microstructure. The microstructure of the material was evaluated and compared with the fracture surface morphology as a function of loading history. It was determined that the MnS inclusion stringers were encapsulated within the ferrita phase and that static fracture progressed along the stringer/ferrita interface. Conversely, fatigue cracks as evidenced by the presence of fatigue striations propagated mainly within the ferrite phase. Photomicrographs. 3 refs. Fatigue p e r f o r m a n c e o f AISI 1140 m o d i f i e d steel. Hertzberg, R. W.,
Vecchio, K. S. and Schmidt Jr, F. E. ASTM J. Test. EvaL Sept. 1989 17, (5). 2 6 1 - 2 6 6 The fatigue behaviour of modified AlSl 1140 resulphurized steel containing Mn (1.05-1.25%) and sulphur (0.15-0.23"/=) was studied at room temperature under load-controlled conditions. Monotonic and cyclic mechanical tests were conducted with samples possessing a 'C' shaped ring configuration; a finite element analysis was used to establish the stress levels appropriate to the 'C'-riog specimen. Quantitative S - N and Goodman diagrams were determined, based on cyclic stresses
Int J Fatigue May 1990
Propagation o f an inclined subsurface crack in rolling/sliding contact fatigue. Kaneta, M,, Okazaki, T. and Murakami, Y. Key Eng. Mater. 1989 33, 191-212 To elucidate a mechanism of the rolling and/or sliding contact fatigue or wear, the mixed mode three-dimensional stress intensity factors for inclined cracks existing beneath the surface, over which a Hertzian contact pressure accompanied by a surface traction moves, are ceiculsted by taking into account the frictional force between crack faces. A penny shaped or an elliptical crack which is inclined against the direction of, or perpendicular to, the movement of contact load is analysed. Effects of the crack size, the crack depth, the angles of the inclinations, etc. are discussed. Graphs. 39 refs.
Effect o f o x i d e f i l m thickness on t h e f a t i g u e b e h e v i o u r o f an a l u m i n u m - l i t h i u m alloy (2090-TgE41). Tails, J, E. and Mazumdar, P. K. Int. J. Fract. J u l y 1989 40, (3), R67-R71 Oxide film coated on an AI-Li alloy (2090-T8E41) will initially decrease life with thickness and attain its minimum at a critical thickness below 140 nm before indicating an improvement as the oxide becomes thicker. The overall improvement of life with decreasing stress level holds up well with the general stress effect in fatigue, but the life level goes through its minimum at a critical film thickness of approx 50 nm, regardless of the test stress level. Coated and uncoated 2090-T8E41 AI- Li alloy specimens were fatigued under completely reversed tansion-compresslon conditions, ie at a load (= R) ratio of -1. The specimens were then tested for the influence of oxide film thickness on the fatigue behaviour. Graphs. 14 refs. Crack p r o p a g a t i o n in A S T M A516 Grade 70 steel under fatigue loading subjected t o different temperatures, Ukadgaonker, V. G. and Sane, B. G. Int. J. Fract. July 1989 40, (3), R49-R52 The values of C and m in the Paris law, da/dN = C(~K) m, which change with temperature, are determined for ASTM A516 grade 70 steel. The values of m are nearly constant, whereas the values of C change considerably with temperature due to the strain hardening effect. Fatigue crack propagation tests were performed on a 10 tonne MTS universal testing machine for temperatures 23, 75, 150, 225 and 275°C on ASTM A516 grade 70 steel. Graphs. 3 refs. A non-linser high t e m p e r a t u r e fracture mechanics basis f o r strain range partitioning. (Report). Kifamura, T. and Halford, G. R. NASA Tech. Memo. NASA TM-4133 1989, 14 pp A direct link has been established between strain range partitioning (SRP) and hightemperature fracture mechanics by deriving the general SRP inelastic strain range vs. cyclic life relstionships from high-temparsture, non-linear, fracture mechanics considerations. The derived SRP life relationships are in reasonable agreement based on the experience of the SRP behaviour of many high-temperature alloys (304. 316, A286, 2.25Cr-1Mo, Hastelloy X, IN718). in addition, fracture mechanics has served as a basis for derivation of the ductihty-normalized SRP life equations, and for examination of SRP relations that are applicable to thermal fatigue life prediction. Areas of additional links between non-linear fracture mechanics and SRP have been identified for future exploration. These include effects of muitiaxiality and low-strain, nominally elastic, long-life creep-fatigue interaction. Graphs. 47 refs.
Three-dimensional analysis o f t h e surface creck-Hertzlan s U m interaction. (Report). Ballarini, R. and Hsu, Y. NASA Contract. Rap. NASA CR-4254 1989, 157 pp
field
The results of a stress intensity factor analysis of semicircular surface cracks in the inner raceway of a M50 steel engine bearing are presented. The loading consists of a moving spherical Hortzian contact load and an axial stress due to rotation and shrink fit. A three-dimensional linear elastic boundary element method code was developed to perform the stress analysis, The element library includes linear and quadratic isoparametric surface elements. Singular quarter point elements were employed to capture the square root displacement variation and the inverse square
226
root stress singularity along the crack front, The program also possesses the capability to separate the whole domain into two subregions. This procedure enables one to solve non-symmetric fracture mechanics problems without having to separate the crack surfaces a priori. A wide range of conflgumtlon parameters was investigated. The ratio of crack depth to bearing thickness wee veded from one-sixtieth to onefifth for several different locations of the Hertzlan load. The strese intensity factors for several crack inclinations were also investigated. The results demonstrate the efficiency and accuracy of the boundary element method. Moreover, the results can provide the basis for crack growth calcoletions end fatigue life prediction. Graphs. 31 refs. Low-cycle f a t i g u e analysis o f notched members. Zhang, D. and Sandor,
B.I. ASTM J. Test. Eval. J u l y 1989 17, (4), 2 1 2 - 2 1 7 Low-cycle fatigue crack initiation and propagation lives of notched members era investigated. By relating Nd (&J/~p)P = Cn to the Coffin-Mansen equation and correlating to test results, p and Cnare found to be functions of several parameters: cyclic stress-strein constants, goomatw of notch (depth end curvature), and stress ratio. (Ajl~,y) is chosen as a parameter for crack propagation in notched members. Fatigue crack initiation and propagation tests were conducted on notched plate specimens of different notch radii and stress ratios. Crack initiation life, crack propagation life, and total fatigue life are compared with the calculations. There are good correlations between the test results and the calculations. Aluminum alloy 7075 was used. Graphs. 17 refs. Fatigue crack p r o p a g a t i o n in rapidly solidified e l u m i n i u m alloys at 25°C and 3000C. Smith, H. H., Michel, D. J. and Reed, J. R. Metall, Trans. A Nov. 1989 20A, (11), 2425-2430 The fatigue crack propagation performance of two rapidly solidified AI alloys was investigated in air at 25 end 300°C. The results show that the crack propagation rates for continuous cycling tests of AI-8Fe-4Ce and AI-4.7Fe-4.7Ni-0.2Cr alloys were similar at 25~C, Although the crack propagation rates of both alloys were increased at 300°C, the AI-Fe-Ce alloy exhibited the greater resistance to crack propagation. The inclusion of a tensile hold time in the fatigue loading cycle at 300°C to produce an increase in the crack propagation performance of the rapidly solidified alloys was not found to be superior when compared with the fatigue crack propagation performance of a wrought AI alloy tested under the same conditions. Transmission and scanning electron microscopy studies of the tested specimens revealed that the crack propagation mode was primarily transgrsnular, with the metastable disperaoid particles providing impenetrable barriers to dislocation motion. Graphs, photomicrographs. 11 refs. U m i t analysis f o r fiat ends in vessels. Kieswetter, N. Tech. Mech. 1989 10, (1), 3 6 - 4 3 (in German) In the design of vessels the I=mit load is the most important criterion of failure, since there occur mainly static or low cyclic loads and ductile materials. Fatigue analysis is required according to TGL 32903 only for cycle numbers >1000. So that failures possibly caused by this practical rule do not occur, unfevoursble structures must be avoided or designed with such thick walls that at least 1000 cycles can be endured. Such unfevourable structures are flat ends with an adjacent cylindrical shell. Fatigue strains may be reduced by designing fiat ends with corner radius or with a groove. The effects of corner radius and groove for the limit load of flat ends are covered. Using the static and kinematic method, respectively, plate and cylindrical shell with corner radius are at first treated separately end then joined to a complete solution. Examples of H52-3 steel are given. Graphs. 10 refs.
Strain hardening and f a t i g u e o f s i m u l a t e d case microstructurss cerburized steels. Zaccone, M. D., Kelley, J. B. and Krauss, G. Ind. Heat Sept. 1989 56, (9), 38-51
of
The effect of microstructure on high and low cycle fatigue of a series of high carbon (0.8 C) stools was evaluated. In particular, the effect of retained austenite on plastic deformation, strain hardening behaviour, and fracture of tempered martsnsite-austenite composite microstructure was studied. The steels had Cr content of 0, 0.3, 0.6, 0.9, and 1.3 wt.% and other approximate contents of 0.8 C, 0.9 Mn, 0.3 Si, 1.8 Ni, and 0.7 Mo. The retained austenite content varied, generally increasing with increasing content. The steels with the highest Cr contents, and therefore the highest retained austenite contents, had the lowest elastic limits and the lowest strain hardening rates. Tensile flow stresses decreased and plastic strain at fracture increased with increasing amounts of retained austenito. The elastic limit decreased in both compression and tension as retained austanite increased. Graphs, photomicrographs. 17 refs.
Fractography o f AISI 1140 m o d i f i e d steel u n d e r static end cyclic loading conditions. Vecchio, K. S., Hertzberg, R. W. and Schmidt Jr, F. E. ASTM J. Test. Eval. Sept. 1989 1 7 , ( 5 ) , 267-272 The fracture behaviour of modified AISI 1140 rssulphurized steel containing Mn (1.05-1.25%) and sulphur (0.15-0.23%) has been studied under controlled fast fracture and fatigue fracture conditions. 'C'-shepad ring samples were machined from tubes hammer forged at 700°C by the GFM process (Gesellschaft fur Fertigungstechnik und Meschinenbeu (AG) manufactured in Stayr, Austria) so as to develop a highly fibred (axial) microstructure. The microstructure of the material was evaluated and compared with the fracture surface morphology as a function of loading history. It was determined that the MnS inclusion stringers were encapsulated within the ferrita phase and that static fracture progressed along the stringer/ferrita interface. Conversely, fatigue cracks as evidenced by the presence of fatigue striations propagated mainly within the ferrite phase. Photomicrographs. 3 refs. Fatigue p e r f o r m a n c e o f AISI 1140 m o d i f i e d steel. Hertzberg, R. W.,
Vecchio, K. S. and Schmidt Jr, F. E. ASTM J. Test. EvaL Sept. 1989 17, (5). 2 6 1 - 2 6 6 The fatigue behaviour of modified AlSl 1140 resulphurized steel containing Mn (1.05-1.25%) and sulphur (0.15-0.23"/=) was studied at room temperature under load-controlled conditions. Monotonic and cyclic mechanical tests were conducted with samples possessing a 'C' shaped ring configuration; a finite element analysis was used to establish the stress levels appropriate to the 'C'-riog specimen. Quantitative S - N and Goodman diagrams were determined, based on cyclic stresses
Int J Fatigue May 1990