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Surface fatigue life of carburized and hardened M50NiL and AISI 9310 spur gears and rolling-contact test bars. (Report)
Simulation ~
o f t h e p o e i f f o n o f f a t i g u e f r a c t u r e plane in
matmfall with bimdld Ioed~ (IlL Mecha, E. Mater. wiss. Werkst. tech. 1989 20, (5), 153--163 A method of determination of the expected fatigue fracture plane position under random triexiel stress state, the weight function method for biexial cyclic loadings, is enelyeacl with digital simulation. The fatigue fracture plane position is determined with mean values of the direction cosine= of principal strees axes. Averaging is done st engte values with the use of weights. Eleven various weights are presented and their usability is analysed on the basis of experimental results from the literature, The weights are shown to be in good agreement with results of simulation tests and experiments. 57 refe. Low-cycle f a t i g u e properties o f steels and t h e i r w e l d metals. Itoh, Y. Z.
and Kashiwaya, H. J. Eng. Mater. Technol. (Trans. ASME) Oct. 1989 111, (4), 4 3 1 - 4 3 7
Completely reversed, strein-controUed, low-cycle fatigue behaviour at room temperature is investigated for steals (304, SM41A, SS41, SMSOA, HT60, HTB0) and their weld metals. Weld metal specimens ware taken from multi-pass weld metal deposited by shield metal arc welding (SMAW) and gas metal arc welding (GMAW), such that their gauge length consisted entirely of the weld metal. Results indicate that there is a trend toward reduction in the low-cycle fatigue life of weld metals as compared with the base metals. In low carbon steel weld metals, the tendency described above is explained in terms of local plastic strain concentration by lack of uniformity of the multi-pess weld metals. The weld metals do not have the same mechanical properties anywhere as confirmed by hardness distribution, and the fatigue crack grows preferentially through the temper softened region in the multipass welds. In Type 308 ctainlaas steal weld metals, the ductility reduction causes reductions in low-cycle fatigue life. This study leads to the conclusion that fairly accurate estimates of the low-cycle fatigue life of weld metals can be obtained using Manaon's universal slope method. However, life estimates of the Type 304 stainless steel is difficult due to a lack of ductility caused by a deformation-induced martensitic transformation. 11 refe.
Fatigue crack g r o w t h prediction u n d e r r a n d o m peaks and sequence loading. Alawi, H. J. Eng. Mater. Technol. (Trans. ASME) Oct. 1989 111, (4), 3 3 8 - 3 4 4 Fatigue crack growth under random amplitude and sequence loading with peaks followin~] the Rayleigh probability density function is simulated using the probabilistic model. Another attempt at fatigue life prediction under the above loads is made by converting random loads into equivalent constant amplitude. Prediction results are compared with experimental findings. Empirical data for fatigue crack growth under random loads at different frequencies are compared with the results of prediction using the above techniques. Experimental results of three steels are used to compare with the findings of the above prediction techniques. These steels are AISI 1018, AISI 4340 and stainless PH 17-7. it is seen that the probebilistic model produces reliable results. It conesrvstively predicts fatigue crack growth when no delay mechanism to retard crack growth is introduced. 14 refs.
Fatigue crack g r o w t h o f surface cracks in t h e rail w e b . Jeong, D. Y. and
Orringer, O. Theor. Appl. Fract. Mech. Oct. 1989 12, (1), 4 5 - 5 8
The analytical prediction of surface cracks in the rail web is investigated by two different approaches. The first approach uses engineering fracture mechanics principles with elementary beam theory (is one-dimensional) stress analysis. The second approach applies the strain energy density criterion to a three-dimensional finite element s U m analysis of the rail web. Results are presented in terms of crack size as a function of accumulated tonnage for variations in loading (tangent or curved track), support conditions (foundation modulus), and assumed levels of residual stress. The results of both modMs are consistent in that the predicted growth rates are fairly slow when compared to other types of rail defects (for example, the detail fracture in the rail head). 19 refs. Cyclic analysis o f p r o p a g a t i n g s h o r t cracks at notches and short-crack g r o w t h behaviour. Wang, J. C. and Lu, Y. Z. Eng. Fract. Mech. 1889 34, (4), 8 3 1 - 8 4 0 Elastic-plastic and large-strain finite element analyses of propagating short cracks at notches under cyclic loading and the corresponding fatigue crack growths of short cracks have been studied in low alloy steals. The specimens used in both numerical analyses and crack growth testing were semicircular notched and Vshaped notched flat panels with a through-thickness short crack emanating from the notch root. In the analyses, the cracks were assumed to propagate sequentially with an incremental length of an element size at the maximum load of cyclic loading. Plastic zones, stress fields and strain fields around the crack tips, and crack-closure and crack-opening stresses at different crack lengths were given. It was found that the minimum crack growth rate, obtained by fatigue testing, occurred st the crack length at which the crack-closure stress was the highest. The cyclic J-integral was then computed at different crack lengths by the finite element method and exhibits path dependence. The value of the cyclic J-intagrel with the path near the crack tip is larger than that with the path away from the crack tip and both are less than the value obtained by Dowling's approach. Finally correlation among the fatigue crack growth rate, cyclic J-intagrel and the results of cyclic analyses of propagating short cracks at notches are discussed. Graphs. 29 refs, Dislocation structures in nickel d u r i n g high t e m p e r a t u r e l o w cycle f a t i g u e at large c u m u l a t i v e strains. Chen, S. and Gottstein, G. J. Mater. Sci. Nov. 1989 24, (11), 4 0 9 4 - 4 0 9 9 The development of the dislocation arrangement during high temperature low cycle fatigue in Ni polycrystals was investigated. Special attention was paid to dislocation structures in the vicinity of grain boundaries. It was found that a definite cell structure develops during progressing cyclic deformation. The motion of grain boundaries associated with hig h tamperstu re cychc deformation leads to a dislocation structure gradient in the wake of the boundaries. These structure gradients are suspected to be prone to setting off nucleation of dynamic recwstallizstion. Upon strain path changes, the fatigued structure was observed to become gradually superimposed by a new cell structure, without prmr decomposition. 12 refs. Stochastic approach t o m o d e l l i n g f a t i g u e crack g r o w t h . Spencer Jr, B.
Endurance o f aircraft gas t u r b i n e m a l n s h a f t ball b e a r i n g s - a n a l y s i s using i m p r o v e d f a t i g u e life tlheory: IL A p p l i c a t i o n t o s bearing o p e r a t i n g under diffioult lubrication conditions. Harris, T., Ioannides, E., Ragen, M. and Tam, H. J. Tribology (Trans. ASME) Oct. 1989 111, (4), 7 0 8 - 7 1 0 It is apparent from the analysis performed that the ball bearing fatigue life calculation methods currently defined in the ANSI and ISO standards, and subsequently in bearing manufacturers' catalogues, cannot be used to predict accurate fatigue endurance of high speed, aircraft gas turbine engine, ball bearings. The current rating methods under-reted the bearing fatigue endurance by two orders of magnitude. It was shown that the current rating methods cannot provide a satisfactory explanation of differences m field lives with the use of material factors alone, in contrast, the improved life theory can be effectively used to predict both the extremely long life achievable in applications as well as differences in material and bearing performance by characterizing materials with an additional material constant, the fatigue limit, which brings the rolling contact fatigue theory in line with the traditional structural fatigue theory. Examples of steel MS0 and 52100 are given. 4 refs.
M i x e d m o d e f a t i g u e crack g r o w t h and t h e strain e n e r g y density factor.
Lam, Y. C. Theor. Appl. Fract. Mech. Oct. 1989 12, (1), 6 7 - 7 2 The strain energy density factor S was first proposed by Sih for the prediction of the critical load and failure direction under monotonic, mixed mode loading condition. It seems a natural extension to apply the same concept to fatigue crack propagation. However, a close examination of the existing theory indicates that the strain energy density factor cannot logically account for the phenomena of the Rratio effect and crack arrest. Thus, modification is necessary before the concept can be applied successfully for the prediction of mixed mode fatigue crack propagation. Based on the concept of hysteresis energy dissipation, an effective strain energy density factor range, &Sp.~f, is proposed for the correlation of fatigue crack growth data. ZlSp,effis consistent with the concept of crack closure. Experimental investigation indicates that it could predict the crack growth rates and trajectories. Aluminium alloy 2024 was used. 8 refa.
The effect o f residual stress and its redistribution on f a t i g u e crack ~r~howth. Lam, Y. C. a n d Lien, K. S. ear. Appl. Fract. Mech. Oct. 1989 12, (1), 5 9 - 6 6 There is qualitative understanding of the effects of residual stress on fatigue crack growth; however, the effects have not been completely quantified. The difficulties encountered in quantifi/ing the effects are to measure the residual stress accurately and to take into account stress redistribution as the crack propagates. An experimental method for introducing residual stress in a specimen by local plastic deformation and a technique to measure and delineate the residual stress field are described. The role of residual stress redistribution as the crack grows is also discussed. Results indicate that the approach which accounts for stress redistribution correlates better with experimental data than one which does not consider stress redistribution. Aluminium alloy 2024 was used. 15 refs.
Int J Fatigue May 1990
F., Tang, J. and Artley, M. E. AIAA J. Nov. 1989 27, (11), 1628-1635
An extensive set of fatigue crack growth (FCG) data known as the Virkler data is employed to investigate a recently developed stochastic FCG model that is based on concepts from both fracture mechanics and random process theory. The model represents the crack state as a two-dimensional vectored Marker process and, as a result, has eliminated many objections to previous stochastic FCG models. Two FCG laws are considered for use in the stochastic analysis, and a modified finiteintegral method (MFI) that does not require differentiation of the FCG data is suggested for determining the parameters of the stochastic FCG model. Excellent comparison between theoretical results and experimental date (employing 2024-T6 AI specimens) is obtained for all cases considered. Graphs. 36 refs. Fatigue reliability functions. Akakov, V. A. and Shomperlen, R. G. J. Vib. Acoust.Stress Reliab, Des. (Trans, ASME) Oct. 1989, 111, (4), 443-455 There are many fatigue test and statistical procedures to establish the life distribution function Q = Q(N) at constant stress (S) level. But the stress distribution function, Q = Q(S), st specified life (N) is more important to the designer, and it remains less developed. Generally, if the fatigue life distribution Q(N) and fatigue curve SiN) equations are defined, the fatigue strength distribution Q(S) is implied. However, it has been shown that any life distribution model G(N) may be transformed into the complicated strength distribution function Q(S). Orthogonal relations have been developed to predict complications and to resolve the problem under certain conditions. With the aid of the orthogonal relations, strength distributions Q(S) have bean deduced using (1) Iognormal, (2) two-paremster Waibull, and (3) threeparameter log-Weibull life models Q(N). Examples of AI and Cu alloys are given. 11 refs. Surface f a t i g u e life o f cerbudzed and hardened MSONIL and AISI 9310 gears and rolling-contact t e s t bars. (Report). Townsend, D. P. and
berger, E. N. NASA Tech. Memo. TM-I01979 1988, 16 pp
Spur gear endurance tests and rolling-element surface tests were conducted to mvestigste vacuum-induction-melted, vacuum-arc-melted (VIM-VAR) M5ONiL steel for use as a gear steel in advanced aircraft applications, to determine its endurance characteristics, and to compare the results with those for standard VAR and VIMVAR AISI 9310 gear material. Tests were conducted with spur gears and rollingcontact bars manufactured from VIM-VAR MSONiL and VAR and VIM-VAR AISl 9310. The gear pitch diameter was 8.9 cm. Gear test conditions were an inlet oil temperature of 320 K and outist oil temperature of 350 K, a maximum Hertz stress of 1.71 GPa and a speed of 10 000 rpm. Bench roiling-element fatigue tests were conducted at ambient temperatures with a bar speed of 12 500 rpm and a maximum Hertz stress of 4.83 GPa. The VIM-VAR MSONiL gears had a surface fatigue life that was 4.5 and 11.5 times that for VIM-VAR and VAR AISI 9310 gears, respectively. The surface fatigue life of the VIM-VAR MSONiL rolling contact bars was 13.2 and 21.6 times that for the UiM-VAR and VAR AlSl 9310, respectively. The VIM-VAR MSONiL material was shown to have good resistance to fracture through a fatigue spell and to have fatigue life far superior to that of both VIM-VAR and VAR AlSl 9310 gears and rolling-contact bars. 9 refs.
229
o f t h e p o e i f f o n o f f a t i g u e f r a c t u r e plane in
matmfall with bimdld Ioed~ (IlL Mecha, E. Mater. wiss. Werkst. tech. 1989 20, (5), 153--163 A method of determination of the expected fatigue fracture plane position under random triexiel stress state, the weight function method for biexial cyclic loadings, is enelyeacl with digital simulation. The fatigue fracture plane position is determined with mean values of the direction cosine= of principal strees axes. Averaging is done st engte values with the use of weights. Eleven various weights are presented and their usability is analysed on the basis of experimental results from the literature, The weights are shown to be in good agreement with results of simulation tests and experiments. 57 refe. Low-cycle f a t i g u e properties o f steels and t h e i r w e l d metals. Itoh, Y. Z.
and Kashiwaya, H. J. Eng. Mater. Technol. (Trans. ASME) Oct. 1989 111, (4), 4 3 1 - 4 3 7
Completely reversed, strein-controUed, low-cycle fatigue behaviour at room temperature is investigated for steals (304, SM41A, SS41, SMSOA, HT60, HTB0) and their weld metals. Weld metal specimens ware taken from multi-pass weld metal deposited by shield metal arc welding (SMAW) and gas metal arc welding (GMAW), such that their gauge length consisted entirely of the weld metal. Results indicate that there is a trend toward reduction in the low-cycle fatigue life of weld metals as compared with the base metals. In low carbon steel weld metals, the tendency described above is explained in terms of local plastic strain concentration by lack of uniformity of the multi-pess weld metals. The weld metals do not have the same mechanical properties anywhere as confirmed by hardness distribution, and the fatigue crack grows preferentially through the temper softened region in the multipass welds. In Type 308 ctainlaas steal weld metals, the ductility reduction causes reductions in low-cycle fatigue life. This study leads to the conclusion that fairly accurate estimates of the low-cycle fatigue life of weld metals can be obtained using Manaon's universal slope method. However, life estimates of the Type 304 stainless steel is difficult due to a lack of ductility caused by a deformation-induced martensitic transformation. 11 refe.
Fatigue crack g r o w t h prediction u n d e r r a n d o m peaks and sequence loading. Alawi, H. J. Eng. Mater. Technol. (Trans. ASME) Oct. 1989 111, (4), 3 3 8 - 3 4 4 Fatigue crack growth under random amplitude and sequence loading with peaks followin~] the Rayleigh probability density function is simulated using the probabilistic model. Another attempt at fatigue life prediction under the above loads is made by converting random loads into equivalent constant amplitude. Prediction results are compared with experimental findings. Empirical data for fatigue crack growth under random loads at different frequencies are compared with the results of prediction using the above techniques. Experimental results of three steels are used to compare with the findings of the above prediction techniques. These steels are AISI 1018, AISI 4340 and stainless PH 17-7. it is seen that the probebilistic model produces reliable results. It conesrvstively predicts fatigue crack growth when no delay mechanism to retard crack growth is introduced. 14 refs.
Fatigue crack g r o w t h o f surface cracks in t h e rail w e b . Jeong, D. Y. and
Orringer, O. Theor. Appl. Fract. Mech. Oct. 1989 12, (1), 4 5 - 5 8
The analytical prediction of surface cracks in the rail web is investigated by two different approaches. The first approach uses engineering fracture mechanics principles with elementary beam theory (is one-dimensional) stress analysis. The second approach applies the strain energy density criterion to a three-dimensional finite element s U m analysis of the rail web. Results are presented in terms of crack size as a function of accumulated tonnage for variations in loading (tangent or curved track), support conditions (foundation modulus), and assumed levels of residual stress. The results of both modMs are consistent in that the predicted growth rates are fairly slow when compared to other types of rail defects (for example, the detail fracture in the rail head). 19 refs. Cyclic analysis o f p r o p a g a t i n g s h o r t cracks at notches and short-crack g r o w t h behaviour. Wang, J. C. and Lu, Y. Z. Eng. Fract. Mech. 1889 34, (4), 8 3 1 - 8 4 0 Elastic-plastic and large-strain finite element analyses of propagating short cracks at notches under cyclic loading and the corresponding fatigue crack growths of short cracks have been studied in low alloy steals. The specimens used in both numerical analyses and crack growth testing were semicircular notched and Vshaped notched flat panels with a through-thickness short crack emanating from the notch root. In the analyses, the cracks were assumed to propagate sequentially with an incremental length of an element size at the maximum load of cyclic loading. Plastic zones, stress fields and strain fields around the crack tips, and crack-closure and crack-opening stresses at different crack lengths were given. It was found that the minimum crack growth rate, obtained by fatigue testing, occurred st the crack length at which the crack-closure stress was the highest. The cyclic J-integral was then computed at different crack lengths by the finite element method and exhibits path dependence. The value of the cyclic J-intagrel with the path near the crack tip is larger than that with the path away from the crack tip and both are less than the value obtained by Dowling's approach. Finally correlation among the fatigue crack growth rate, cyclic J-intagrel and the results of cyclic analyses of propagating short cracks at notches are discussed. Graphs. 29 refs, Dislocation structures in nickel d u r i n g high t e m p e r a t u r e l o w cycle f a t i g u e at large c u m u l a t i v e strains. Chen, S. and Gottstein, G. J. Mater. Sci. Nov. 1989 24, (11), 4 0 9 4 - 4 0 9 9 The development of the dislocation arrangement during high temperature low cycle fatigue in Ni polycrystals was investigated. Special attention was paid to dislocation structures in the vicinity of grain boundaries. It was found that a definite cell structure develops during progressing cyclic deformation. The motion of grain boundaries associated with hig h tamperstu re cychc deformation leads to a dislocation structure gradient in the wake of the boundaries. These structure gradients are suspected to be prone to setting off nucleation of dynamic recwstallizstion. Upon strain path changes, the fatigued structure was observed to become gradually superimposed by a new cell structure, without prmr decomposition. 12 refs. Stochastic approach t o m o d e l l i n g f a t i g u e crack g r o w t h . Spencer Jr, B.
Endurance o f aircraft gas t u r b i n e m a l n s h a f t ball b e a r i n g s - a n a l y s i s using i m p r o v e d f a t i g u e life tlheory: IL A p p l i c a t i o n t o s bearing o p e r a t i n g under diffioult lubrication conditions. Harris, T., Ioannides, E., Ragen, M. and Tam, H. J. Tribology (Trans. ASME) Oct. 1989 111, (4), 7 0 8 - 7 1 0 It is apparent from the analysis performed that the ball bearing fatigue life calculation methods currently defined in the ANSI and ISO standards, and subsequently in bearing manufacturers' catalogues, cannot be used to predict accurate fatigue endurance of high speed, aircraft gas turbine engine, ball bearings. The current rating methods under-reted the bearing fatigue endurance by two orders of magnitude. It was shown that the current rating methods cannot provide a satisfactory explanation of differences m field lives with the use of material factors alone, in contrast, the improved life theory can be effectively used to predict both the extremely long life achievable in applications as well as differences in material and bearing performance by characterizing materials with an additional material constant, the fatigue limit, which brings the rolling contact fatigue theory in line with the traditional structural fatigue theory. Examples of steel MS0 and 52100 are given. 4 refs.
M i x e d m o d e f a t i g u e crack g r o w t h and t h e strain e n e r g y density factor.
Lam, Y. C. Theor. Appl. Fract. Mech. Oct. 1989 12, (1), 6 7 - 7 2 The strain energy density factor S was first proposed by Sih for the prediction of the critical load and failure direction under monotonic, mixed mode loading condition. It seems a natural extension to apply the same concept to fatigue crack propagation. However, a close examination of the existing theory indicates that the strain energy density factor cannot logically account for the phenomena of the Rratio effect and crack arrest. Thus, modification is necessary before the concept can be applied successfully for the prediction of mixed mode fatigue crack propagation. Based on the concept of hysteresis energy dissipation, an effective strain energy density factor range, &Sp.~f, is proposed for the correlation of fatigue crack growth data. ZlSp,effis consistent with the concept of crack closure. Experimental investigation indicates that it could predict the crack growth rates and trajectories. Aluminium alloy 2024 was used. 8 refa.
The effect o f residual stress and its redistribution on f a t i g u e crack ~r~howth. Lam, Y. C. a n d Lien, K. S. ear. Appl. Fract. Mech. Oct. 1989 12, (1), 5 9 - 6 6 There is qualitative understanding of the effects of residual stress on fatigue crack growth; however, the effects have not been completely quantified. The difficulties encountered in quantifi/ing the effects are to measure the residual stress accurately and to take into account stress redistribution as the crack propagates. An experimental method for introducing residual stress in a specimen by local plastic deformation and a technique to measure and delineate the residual stress field are described. The role of residual stress redistribution as the crack grows is also discussed. Results indicate that the approach which accounts for stress redistribution correlates better with experimental data than one which does not consider stress redistribution. Aluminium alloy 2024 was used. 15 refs.
Int J Fatigue May 1990
F., Tang, J. and Artley, M. E. AIAA J. Nov. 1989 27, (11), 1628-1635
An extensive set of fatigue crack growth (FCG) data known as the Virkler data is employed to investigate a recently developed stochastic FCG model that is based on concepts from both fracture mechanics and random process theory. The model represents the crack state as a two-dimensional vectored Marker process and, as a result, has eliminated many objections to previous stochastic FCG models. Two FCG laws are considered for use in the stochastic analysis, and a modified finiteintegral method (MFI) that does not require differentiation of the FCG data is suggested for determining the parameters of the stochastic FCG model. Excellent comparison between theoretical results and experimental date (employing 2024-T6 AI specimens) is obtained for all cases considered. Graphs. 36 refs. Fatigue reliability functions. Akakov, V. A. and Shomperlen, R. G. J. Vib. Acoust.Stress Reliab, Des. (Trans, ASME) Oct. 1989, 111, (4), 443-455 There are many fatigue test and statistical procedures to establish the life distribution function Q = Q(N) at constant stress (S) level. But the stress distribution function, Q = Q(S), st specified life (N) is more important to the designer, and it remains less developed. Generally, if the fatigue life distribution Q(N) and fatigue curve SiN) equations are defined, the fatigue strength distribution Q(S) is implied. However, it has been shown that any life distribution model G(N) may be transformed into the complicated strength distribution function Q(S). Orthogonal relations have been developed to predict complications and to resolve the problem under certain conditions. With the aid of the orthogonal relations, strength distributions Q(S) have bean deduced using (1) Iognormal, (2) two-paremster Waibull, and (3) threeparameter log-Weibull life models Q(N). Examples of AI and Cu alloys are given. 11 refs. Surface f a t i g u e life o f cerbudzed and hardened MSONIL and AISI 9310 gears and rolling-contact t e s t bars. (Report). Townsend, D. P. and
berger, E. N. NASA Tech. Memo. TM-I01979 1988, 16 pp
Spur gear endurance tests and rolling-element surface tests were conducted to mvestigste vacuum-induction-melted, vacuum-arc-melted (VIM-VAR) M5ONiL steel for use as a gear steel in advanced aircraft applications, to determine its endurance characteristics, and to compare the results with those for standard VAR and VIMVAR AISI 9310 gear material. Tests were conducted with spur gears and rollingcontact bars manufactured from VIM-VAR MSONiL and VAR and VIM-VAR AISl 9310. The gear pitch diameter was 8.9 cm. Gear test conditions were an inlet oil temperature of 320 K and outist oil temperature of 350 K, a maximum Hertz stress of 1.71 GPa and a speed of 10 000 rpm. Bench roiling-element fatigue tests were conducted at ambient temperatures with a bar speed of 12 500 rpm and a maximum Hertz stress of 4.83 GPa. The VIM-VAR MSONiL gears had a surface fatigue life that was 4.5 and 11.5 times that for VIM-VAR and VAR AISI 9310 gears, respectively. The surface fatigue life of the VIM-VAR MSONiL rolling contact bars was 13.2 and 21.6 times that for the UiM-VAR and VAR AlSl 9310, respectively. The VIM-VAR MSONiL material was shown to have good resistance to fracture through a fatigue spell and to have fatigue life far superior to that of both VIM-VAR and VAR AlSl 9310 gears and rolling-contact bars. 9 refs.
229