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Crack path prediction under fretting fatigue—a theoretical and experimental approach
Fatigue Abstracts housings to enable the winding or Lmwinding of rolls of stock material with the minimum of eqnipment down time. The inherent shape and functionality of an airshaft means that failure by fatigue and fracture is a major concern. The airshaft, for example, has a cross-section which changes along its length and it is sut2iected to signilicant bending stresses, which alternate with rotation. The weight of the roll of material will also change appreciably during operation and. in addition, the mflated inner tube pressure l+urther increases stress levels at critical locations, l'his paper analyses the service failure of a specific airshafl, front both fatigue crack initiation and crack propagation considerations, and discusses how the failure might have easily been avoided. The shaft material was ahmmmm alloy. Graphs, 3 ref.
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Design curve to characterize fatigue strength. Shen. C.L,. Wir.whing. P.H. and Cashman, (,:.7~ .I. Eng. Mater. Teetmol. (Transact. ASME) (Oct. 1996) 118(4), 535 54l Fatigue (S-NI data exhibit relatively large scatter. For design puq~oses, an N curve that characterizes )htigue strength is required. This cnrvc should on the lower, or safe, side of the data. A method based on a modification the Owen tolerance interval is proposed. The method is genend and can applied to nonlinear heteroscedastic data having l'unont~-, Graphs, 17 rel.
S lie ol be
Life prediction of notched specimens using multiaxial surface and subsurface strain analyses. Shatil, G. and Smith, l).,I. ,1. Eng. Mater. I'echnM. ¢l'ransaet. ASME) (I991~ 118(4t, 529 534
Crucible Marlok (maraging high-strength die steel). Crucible Marlok is a maragmg ultrahigh-strength die steel designed for use in demanding die applications requiring high thermal fatigue resistance. Crucible Marlok is hardened by relatively low-temperature precipitation heat treatment. A hardened die has a fully martensitic structure, which is impossible to achieve Ik~r HI3. except in thin cross sections. Crucible Marlok dies experience a slight shrinkage of 0.0005 in./in, in heat treatment. Dimensional changes are unili)rm and predictable. This contrasts with HI3 which is unpredictable and can range from 0.0015 inJin, shrinkage to +0.005 in. in. growth. Because no phase translbnnatiml takes place with Crucible Marlok, distortion is minimal and the resulting nlcchanical properties are not inlluenced by die size.
Multiaxial fatigue lil~ prediction analyses arc applied to notched specimens subiected to high strain constant amplitude Ioadiug. The specimens arc inade from isotropic and anisotropic batches of the structural steel I:+NI5R. "l"+~osets of experimental data are used for the analyses: data trom the biaxial lafigue of thin walled specimens and data from the uniaxial fatigue of hourglass specimens. The maximum strain parameter and two multiaxial fatigue approaches, the Brown-Miller and the I+ohr Ellison theories, are used to predict the fatigue life. A simple subsurface strain model is developed to o'.ercome the geometry difference between the thin walled biaxial specimens and the solid bar notched specimens. Fairly good life prediction is obtained v, ith the multiaxial fatigue parameters and the subsnfface model using elastic plastic linite element simulations. Graphs, 23 ref.
Influence of Ce on the microstructure and properties of AI-Li alloy.
Crack path prediction under fretting fatigue--a theoretical and experimental approach.
T S 5 4 l (June 1996) Pp2
Wang, Y.-X. and Xu, L. Mater. Sci. Formn 1199fi) 217-222 12), 1323 1328 Cot!]erence: Aluminium Alloys 77wit Physical and Mechanical Properties. I('AA5. Part 2+ Grenoble, Fr~ince (I 5 July 1996) Curves of -kK,, vs. Aa, h and AK~ vs ,.Xa,, lot AI Li alloy 2090 have been detennined and compared with those lbr traditional AI alloy 2024. The growth resistance of short fatigue cracks for AI Li alloy 2090 is quantitatively e'~aluated. The essential reason for stronger short cracks effect has been ascertained. Influence of Ce on the growth behaviour of short fatigue cracks for aluminumlithium alloy 2090 was investigated. The results show that by adding cerium into this alloy a significant improvement in A& can be achieved and at the same time 5K,,.,h i', increased. Consequently, the essential factor resulting in lower growth resistance of short fatigue cracks for this alloy is removed and the growth resistance of hmg and short fatigue cracks is increased. Graphs, photomicrographs. 6 rel.
Detecting gear tooth fatigue cracks in advance of complete fracture. Zakrajsek, d.J. and Lewieki, I).(;. NAS'A 1"M-107145. NASA Centre/br Aerovmce h!fi)rmation. Baltimore. MD 21240 0757, U.S.A. (Jan. 1996) Pp 12
P.O. Box 8757.
Results of using vibration-based methods to detect gear tooth fatigue cracks are presented. An experimental test rig was used to fail a number of spur gear specimens through bending fatigue. The gear tooth fatigue crack in each test was initiated through a small notch in the tillet area of tooth on the gear. The primary purpose of these tests was to verify analytical predictions of fatigue crack propagation direction and rate as a function of gear rim thickness. The vibration signal from a total of three tests was monitored and recorded for gear fault detection research. The damage consisted of complete rim fracture on the two thin rim gears and single tooth fracture on the standard full rim test gear. Vibration-based fault detection methods were applied to the vibration signal both on-lme and after the tests were completed. The objectives of this effort were It) identify methods capable of detecting the fatigue crack, and detemfine how far in advance of total failure positive detection was gi,,en. Results showed that the fault detection methods failed to respond to the fatigue crack prior to complete rim fracture ill lhe thin rim gear tests. In the standard full rim gear test all the methods responded to the fatigue crack in adwmce of tooth fracture: ht~wever, only three of the methods responded to the tatiguc crack in the early stages of crack propagation. Spectra, graphs, 9 ref.
(;ear crack propagation investigatinns. l,ewieki. D.(;. and Ballarini+ R. NASA TM-107147. NASA Centre fl,r Aero,wace lt!/bnmttion, P.O. Box 8757, Bahimore. MI) 21240-0757, U.S.A. (Jan. 1996) Pp 10 Analytical and experimental studies were perlbrmed to investigate the effect of gear rim thickness on crack propagation life. The FRANC (FRacture ANalysis Code) computer program was used to simulate crack propagalion. "The FRANC program used principles of linear elastic fracture mechanics, finite element modelling, and a unique re-meshing scheme to determine crack tip strcss distributions, estimate stress intensity factors and model crack propagation. Various faligue crack growth models were used to estimate crack propagation life based on the calculated stress intensity factors. Experimental tests were perlbrmcd in a gear fatigue rig to validate predicted crack propagation results. Test gears were installed with special crack propagation gauges in the tooth lillet region to measure bending fatigue crack growth. Good correlation between predicted and measured crack growth was achieved when the fatigue crack closnre concept was introduced into the analysis. As the gear rim thickness decreased, the compressive cyclic stress in the gear tooth lillet region increased. This retarded crack growth and increased the number of crack propagation cycles to failure. Gear materials was AISI 9310 steel. Graphs, 22 ref.
Lamueq. V., Duhourg. M.C. and Vincent, L. .I. Trihologv (Transact. ASME) (1996) 118 14). 71 I 720 In this paper, the direction of crack growth under fretting latigue loading is studied through an experimental and theoretical approach. The experimental work enabled the fretting conditions to bc known and the site of siltation and crack trajectory to be viewed; theoretical work permitted a prediction ol those processes. Fretting wear and fretting fatigue loadings induce non proportional mixed mode loading at the tip of the cracks initiated within tbe contact zone, The classical criteria predicting the direction of crack growth cannot account for the non-proportional loading. Tests were carried out Io study the cracking phenomena nnder cumnlative effects ol contact and external Ioadings, that is. fretting fatigue loading. The fretting contact between the two contacting bodies is modeled to evahmtc the operating contact loading conditions. The response of the cracked body is determiued in terms of stress intensity factors using the continuous distribution of dislocations theory coupled with a unilateral contact analysis with friction. The angle of crack extension is then predictetL at different stages of crack life. according to a new approach. The correlation of the predicted angle of crack extension with the experimental observation allows the conclusion thai, under fretting fatigue loading, cracks propagate by a tnode I process. Graphs, photomicrographs. 57 rcl.
Continuum fatigue damage modeling fiw critical design, control, and fault prognosis. Lorenzo, C.t". NASA TM-107065, NASA Centre .h~r Aero.v~ace Iq[bmmmm. I'.0. Box ,~'757, Baltimore, MI) 21240-0757. U.S.A. (Jan. 19961 pp 22 This paper develops a simplilied continuum (continnou,, v,,ilh respect to time, stress, etc.) fatigue damage model for use in critical design, life extending control and fault prognosis. The work is based on the local strain cyclic damage modelmg method. New nonlinear explicit equation forms ol cyclic damage in terms of stress amplitude are derived to facilitate lhe continunm modelling. Stress based continuum models are derived. Extension to plastic strain-strain rate m o d e l s is a l s o presented. Progress tmA'ard a lion z e r o inean stress based is presented. Also new nonlinear explicit equation forms m terms of stress amplitude are derived for this case. Application of the various models to design, control, and fauh prognosis is considered Example material: RQ('+ 100 steel. Graphs, 9 ref.
Reality based integrity assessment of offshore platforms. I)h(II'IPI(IV(LY(IlI, S. Cnmputaliomfl .¢lethod~ l~'xting Eng. Integri(v (1996) Cm!fi'rem e: t"ir~t hirer national Coq/~'rem'e +m Computational Method~ and 7~'stinv /br Em,,inecrin~,, Integrity, Kuala Lumpur, Malaysia (I t) 21 Mar. 1906t Fatigue crack grov+th is one of the main deterioration processes in olfshore structures. The latiguc life of welded connections in offshore structures is therefore an important design criterion and a governing factor for the plannmg of inspection and maintenance actions. Due to the consMcrablc costs associated with inspection and maintenance of offshore structures it is necessary t{+ optimize the inspection and maintenance plans such that the costs are minimized and at the same time the risk kept within acceptable limits. This implies that the estimation of laligue crack growth and the effect of inspection and maintenance actions must be modelled accurately. This paper describes the development of a reliability based structural integrity assessment tool based on fracture mechanics models. Graphs. 9 ref.
Fatigue crack growth analysis of AIZnMg alloy bridge girder. Aliabadi, M.H. and Mi, Y. Computational Methods Te.~ting Eng. IntegriO" (1996) 257 2~6 Co/tfet¥'nee: Firvt International Cot~/erenee Oil Computational Method~ ~l/l~l 7~'sting .fi)r Engineerinr4 Integrio', Kuala Lumpur, Malaysia (19- 21. Mat. 19961 The boundary element method (BEM) is used to predict the filtiguc crack growth in a portable bridge. The predicted results are compared to measure-
731
Design curve to characterize fatigue strength. Shen. C.L,. Wir.whing. P.H. and Cashman, (,:.7~ .I. Eng. Mater. Teetmol. (Transact. ASME) (Oct. 1996) 118(4), 535 54l Fatigue (S-NI data exhibit relatively large scatter. For design puq~oses, an N curve that characterizes )htigue strength is required. This cnrvc should on the lower, or safe, side of the data. A method based on a modification the Owen tolerance interval is proposed. The method is genend and can applied to nonlinear heteroscedastic data having l'unont~-, Graphs, 17 rel.
S lie ol be
Life prediction of notched specimens using multiaxial surface and subsurface strain analyses. Shatil, G. and Smith, l).,I. ,1. Eng. Mater. I'echnM. ¢l'ransaet. ASME) (I991~ 118(4t, 529 534
Crucible Marlok (maraging high-strength die steel). Crucible Marlok is a maragmg ultrahigh-strength die steel designed for use in demanding die applications requiring high thermal fatigue resistance. Crucible Marlok is hardened by relatively low-temperature precipitation heat treatment. A hardened die has a fully martensitic structure, which is impossible to achieve Ik~r HI3. except in thin cross sections. Crucible Marlok dies experience a slight shrinkage of 0.0005 in./in, in heat treatment. Dimensional changes are unili)rm and predictable. This contrasts with HI3 which is unpredictable and can range from 0.0015 inJin, shrinkage to +0.005 in. in. growth. Because no phase translbnnatiml takes place with Crucible Marlok, distortion is minimal and the resulting nlcchanical properties are not inlluenced by die size.
Multiaxial fatigue lil~ prediction analyses arc applied to notched specimens subiected to high strain constant amplitude Ioadiug. The specimens arc inade from isotropic and anisotropic batches of the structural steel I:+NI5R. "l"+~osets of experimental data are used for the analyses: data trom the biaxial lafigue of thin walled specimens and data from the uniaxial fatigue of hourglass specimens. The maximum strain parameter and two multiaxial fatigue approaches, the Brown-Miller and the I+ohr Ellison theories, are used to predict the fatigue life. A simple subsurface strain model is developed to o'.ercome the geometry difference between the thin walled biaxial specimens and the solid bar notched specimens. Fairly good life prediction is obtained v, ith the multiaxial fatigue parameters and the subsnfface model using elastic plastic linite element simulations. Graphs, 23 ref.
Influence of Ce on the microstructure and properties of AI-Li alloy.
Crack path prediction under fretting fatigue--a theoretical and experimental approach.
T S 5 4 l (June 1996) Pp2
Wang, Y.-X. and Xu, L. Mater. Sci. Formn 1199fi) 217-222 12), 1323 1328 Cot!]erence: Aluminium Alloys 77wit Physical and Mechanical Properties. I('AA5. Part 2+ Grenoble, Fr~ince (I 5 July 1996) Curves of -kK,, vs. Aa, h and AK~ vs ,.Xa,, lot AI Li alloy 2090 have been detennined and compared with those lbr traditional AI alloy 2024. The growth resistance of short fatigue cracks for AI Li alloy 2090 is quantitatively e'~aluated. The essential reason for stronger short cracks effect has been ascertained. Influence of Ce on the growth behaviour of short fatigue cracks for aluminumlithium alloy 2090 was investigated. The results show that by adding cerium into this alloy a significant improvement in A& can be achieved and at the same time 5K,,.,h i', increased. Consequently, the essential factor resulting in lower growth resistance of short fatigue cracks for this alloy is removed and the growth resistance of hmg and short fatigue cracks is increased. Graphs, photomicrographs. 6 rel.
Detecting gear tooth fatigue cracks in advance of complete fracture. Zakrajsek, d.J. and Lewieki, I).(;. NAS'A 1"M-107145. NASA Centre/br Aerovmce h!fi)rmation. Baltimore. MD 21240 0757, U.S.A. (Jan. 1996) Pp 12
P.O. Box 8757.
Results of using vibration-based methods to detect gear tooth fatigue cracks are presented. An experimental test rig was used to fail a number of spur gear specimens through bending fatigue. The gear tooth fatigue crack in each test was initiated through a small notch in the tillet area of tooth on the gear. The primary purpose of these tests was to verify analytical predictions of fatigue crack propagation direction and rate as a function of gear rim thickness. The vibration signal from a total of three tests was monitored and recorded for gear fault detection research. The damage consisted of complete rim fracture on the two thin rim gears and single tooth fracture on the standard full rim test gear. Vibration-based fault detection methods were applied to the vibration signal both on-lme and after the tests were completed. The objectives of this effort were It) identify methods capable of detecting the fatigue crack, and detemfine how far in advance of total failure positive detection was gi,,en. Results showed that the fault detection methods failed to respond to the fatigue crack prior to complete rim fracture ill lhe thin rim gear tests. In the standard full rim gear test all the methods responded to the fatigue crack in adwmce of tooth fracture: ht~wever, only three of the methods responded to the tatiguc crack in the early stages of crack propagation. Spectra, graphs, 9 ref.
(;ear crack propagation investigatinns. l,ewieki. D.(;. and Ballarini+ R. NASA TM-107147. NASA Centre fl,r Aero,wace lt!/bnmttion, P.O. Box 8757, Bahimore. MI) 21240-0757, U.S.A. (Jan. 1996) Pp 10 Analytical and experimental studies were perlbrmed to investigate the effect of gear rim thickness on crack propagation life. The FRANC (FRacture ANalysis Code) computer program was used to simulate crack propagalion. "The FRANC program used principles of linear elastic fracture mechanics, finite element modelling, and a unique re-meshing scheme to determine crack tip strcss distributions, estimate stress intensity factors and model crack propagation. Various faligue crack growth models were used to estimate crack propagation life based on the calculated stress intensity factors. Experimental tests were perlbrmcd in a gear fatigue rig to validate predicted crack propagation results. Test gears were installed with special crack propagation gauges in the tooth lillet region to measure bending fatigue crack growth. Good correlation between predicted and measured crack growth was achieved when the fatigue crack closnre concept was introduced into the analysis. As the gear rim thickness decreased, the compressive cyclic stress in the gear tooth lillet region increased. This retarded crack growth and increased the number of crack propagation cycles to failure. Gear materials was AISI 9310 steel. Graphs, 22 ref.
Lamueq. V., Duhourg. M.C. and Vincent, L. .I. Trihologv (Transact. ASME) (1996) 118 14). 71 I 720 In this paper, the direction of crack growth under fretting latigue loading is studied through an experimental and theoretical approach. The experimental work enabled the fretting conditions to bc known and the site of siltation and crack trajectory to be viewed; theoretical work permitted a prediction ol those processes. Fretting wear and fretting fatigue loadings induce non proportional mixed mode loading at the tip of the cracks initiated within tbe contact zone, The classical criteria predicting the direction of crack growth cannot account for the non-proportional loading. Tests were carried out Io study the cracking phenomena nnder cumnlative effects ol contact and external Ioadings, that is. fretting fatigue loading. The fretting contact between the two contacting bodies is modeled to evahmtc the operating contact loading conditions. The response of the cracked body is determiued in terms of stress intensity factors using the continuous distribution of dislocations theory coupled with a unilateral contact analysis with friction. The angle of crack extension is then predictetL at different stages of crack life. according to a new approach. The correlation of the predicted angle of crack extension with the experimental observation allows the conclusion thai, under fretting fatigue loading, cracks propagate by a tnode I process. Graphs, photomicrographs. 57 rcl.
Continuum fatigue damage modeling fiw critical design, control, and fault prognosis. Lorenzo, C.t". NASA TM-107065, NASA Centre .h~r Aero.v~ace Iq[bmmmm. I'.0. Box ,~'757, Baltimore, MI) 21240-0757. U.S.A. (Jan. 19961 pp 22 This paper develops a simplilied continuum (continnou,, v,,ilh respect to time, stress, etc.) fatigue damage model for use in critical design, life extending control and fault prognosis. The work is based on the local strain cyclic damage modelmg method. New nonlinear explicit equation forms ol cyclic damage in terms of stress amplitude are derived to facilitate lhe continunm modelling. Stress based continuum models are derived. Extension to plastic strain-strain rate m o d e l s is a l s o presented. Progress tmA'ard a lion z e r o inean stress based is presented. Also new nonlinear explicit equation forms m terms of stress amplitude are derived for this case. Application of the various models to design, control, and fauh prognosis is considered Example material: RQ('+ 100 steel. Graphs, 9 ref.
Reality based integrity assessment of offshore platforms. I)h(II'IPI(IV(LY(IlI, S. Cnmputaliomfl .¢lethod~ l~'xting Eng. Integri(v (1996) Cm!fi'rem e: t"ir~t hirer national Coq/~'rem'e +m Computational Method~ and 7~'stinv /br Em,,inecrin~,, Integrity, Kuala Lumpur, Malaysia (I t) 21 Mar. 1906t Fatigue crack grov+th is one of the main deterioration processes in olfshore structures. The latiguc life of welded connections in offshore structures is therefore an important design criterion and a governing factor for the plannmg of inspection and maintenance actions. Due to the consMcrablc costs associated with inspection and maintenance of offshore structures it is necessary t{+ optimize the inspection and maintenance plans such that the costs are minimized and at the same time the risk kept within acceptable limits. This implies that the estimation of laligue crack growth and the effect of inspection and maintenance actions must be modelled accurately. This paper describes the development of a reliability based structural integrity assessment tool based on fracture mechanics models. Graphs. 9 ref.
Fatigue crack growth analysis of AIZnMg alloy bridge girder. Aliabadi, M.H. and Mi, Y. Computational Methods Te.~ting Eng. IntegriO" (1996) 257 2~6 Co/tfet¥'nee: Firvt International Cot~/erenee Oil Computational Method~ ~l/l~l 7~'sting .fi)r Engineerinr4 Integrio', Kuala Lumpur, Malaysia (19- 21. Mat. 19961 The boundary element method (BEM) is used to predict the filtiguc crack growth in a portable bridge. The predicted results are compared to measure-