In order to increase the fatigue life (FL) of road wheels (RW), a kind of double layer rubber flange (DLRF) is put forward. It consists of two layers of rubber, where metal wires are laid in the inner layer and the ou...In order to increase the fatigue life (FL) of road wheels (RW), a kind of double layer rubber flange (DLRF) is put forward. It consists of two layers of rubber, where metal wires are laid in the inner layer and the outer layer has no inlaid metal wires. Stress, strain and temperature field of DLRF were calculated with ANSYS finite element analysis (FEA) software, FL of DLRF RW was also computed with fracture mechanics fatigue theory. The results of computation indicate that the heat generated in RW's rubber flange (RF) can be reduced by the use of DLRF, and the FL of RW can be increased without affecting the mechanical intensity of RW.展开更多
In present paper, we obtain the inverse moment estimations of parameters of the Birnbaum-Saunders fatigue life distribution based on Type-Ⅱ bilateral censored samples and multiply Type-Ⅱ censored sample. In this pap...In present paper, we obtain the inverse moment estimations of parameters of the Birnbaum-Saunders fatigue life distribution based on Type-Ⅱ bilateral censored samples and multiply Type-Ⅱ censored sample. In this paper, we also get the interval estimations of the scale parameters.展开更多
A method based on solution of the inverse heat conduction problem was presented for online stress monitoring and fatigue life analysis of boiler drums. The mathematical model of the drum temperature distribution is ba...A method based on solution of the inverse heat conduction problem was presented for online stress monitoring and fatigue life analysis of boiler drums. The mathematical model of the drum temperature distribution is based on the assumptions that the difference of temperature along the longitudinal axis of the boiler drum is negligible with changes only in the radial direction and the circumferential direction, and that the outer surface of drum is thermaUy insulated. Combining this model with the control-volume method provides temperatures at different points on a cross-section of the drum. With the temperature data, the stresses and the life expectancy of the boiler drum are derived according to the ASME code. Applying this method to the cold start-up process of a 300 MW boiler demonstrated the absence of errors caused by the boundary condition assumptions on the inner surface of the drum and testified that the method is an applicable technique for the online stress monitoring and fatigue life analysis of boiler drums.展开更多
Based on the transfer matrix method and Forman equation,a new method is proposed to conduct the modal and fatigue life analysis of a beam with multiple transverse cracks.In the modal analysis,the damping loss factor i...Based on the transfer matrix method and Forman equation,a new method is proposed to conduct the modal and fatigue life analysis of a beam with multiple transverse cracks.In the modal analysis,the damping loss factor is introduced by the complex elastic modulus,bending springs without mass are used to replace the transverse cracks,and the characteristic transfer matrix of the whole cracked beam can be derived.In the fatigue life analysis,considering the interaction of the beam vibration and fatigue cracks growth,the fatigue life of the cracked beam is predicted by the timing analysis method.Numerical calculation shows that cracks have a significant influence on the modal and fatigue life of the beam.展开更多
In present paper, we derive the quasi-least squares estimation(QLSE) and approximate maximum likelihood estimation(AMLE) for the Birnbaum-Saunders fatigue life distribution under multiply Type-Ⅱcensoring. Furthermore...In present paper, we derive the quasi-least squares estimation(QLSE) and approximate maximum likelihood estimation(AMLE) for the Birnbaum-Saunders fatigue life distribution under multiply Type-Ⅱcensoring. Furthermore, we get the variance and covariance of the approximate maximum likelihood estimation.展开更多
Vibration fatigue is one of the main failure modes of blade.The vibration fatigue life of blade is scattered caused by manufacture error,material property dispersion and external excitation randomness.A new vibration ...Vibration fatigue is one of the main failure modes of blade.The vibration fatigue life of blade is scattered caused by manufacture error,material property dispersion and external excitation randomness.A new vibration fatigue probabilistic life prediction model(VFPLPM)and a prediction method are proposed in this paper.Firstly,as one-dimensional volumetric method(ODVM)only considers the principle calculation direction,a three-dimensional space vector volumetric method(TSVVM)is proposed to improve fatigue life prediction accuracy for actual threedimensional engineering structure.Secondly,based on the two volumetric methods(ODVM and TSVVM),the material C-P-S-N fatigue curve model(CFCM)and the maximum entropy quantile function model(MEQFM),VFPLPM is established to predict the vibration fatigue probabilistic life of blade.The VFPLPM is combined with maximum stress method(MSM),ODVM and TSVVM to estimate vibration fatigue probabilistic life of blade simulator by finite element simulation,and is verified by vibration fatigue test.The results show that all of the three methods can predict the vibration fatigue probabilistic life of blade simulator well.VFPLPM &TSVVM method has the highest computational accuracy for considering stress gradient effect not only in the principle calculation direction but also in other space vector directions.展开更多
A method and procedure of high cycle fatigue life prediction for helicopter transmission system tail gearbox casing is presented, including fatigue test load, three parameters S-N curve, reduction factor and cumulativ...A method and procedure of high cycle fatigue life prediction for helicopter transmission system tail gearbox casing is presented, including fatigue test load, three parameters S-N curve, reduction factor and cumulative damage law. According to the fatigue test results, the design load spectrum and the three parameters S-N curve, a fatigue life prediction of the tail gearbox casing of a helicopter is performed as an example.展开更多
This paper investigates theoretically the influence of magnetization on fatigue life by using non-equilibrium statistical theory of fatigue fracture for metals. The fatigue microcrack growth rate is obtained from the ...This paper investigates theoretically the influence of magnetization on fatigue life by using non-equilibrium statistical theory of fatigue fracture for metals. The fatigue microcrack growth rate is obtained from the dynamic equation of microcrack growth, where the influence of magnetization is described by an additional term in the potential energy of microcrack. The statistical value of fatigue life of metal under magnetic field is derived, which is expressed in terms of magnetic field and macrophysical as well as microphysical quantities. The fatigue life of AISI 4140 steel in static magnetic field from this theory is basically consistent with the experimental data.展开更多
A fatigue damage model is developed for evaluating accumulative fatigue damage of dumpers. The loading spectrums acted on dumpers are created according to measured strain data in field. The finite element analysis is ...A fatigue damage model is developed for evaluating accumulative fatigue damage of dumpers. The loading spectrums acted on dumpers are created according to measured strain data in field. The finite element analysis is carried out for assessing stress distribution and strength characteristics of dumpers. Fatigue damage indexes and service life are calculated by a modified Palmgren-Miner rule. The investigation shows that fatigue notch factor has a significant influence on the calculation of fatigue damage of dumpers.展开更多
The effects of laser shock peening (LSP) on improving fatigue life of aluminum alloy 7050 are investigated.Surface hardness is increased corresponding to a high dislocation density induced by LSP.The X-ray diffraction...The effects of laser shock peening (LSP) on improving fatigue life of aluminum alloy 7050 are investigated.Surface hardness is increased corresponding to a high dislocation density induced by LSP.The X-ray diffraction stress measurement shows that LSP results in prominent increase of surface compressive stress,quasi-symmetrically distributed in the laser peened region.The fatigue life of the alloy 7050 in rivet fastener hole structure is notably improved owing to LSP.The sequence of LSP and fastener hole preparation also influence the fatigue cycle life of the alloy.展开更多
A novel method is presented to evaluate the complicated fatigue behavior of gears made of20Cr2Ni4 A.Fatigue tests are conducted in a high-frequency push-pull fatigue tester,and acoustic emission（AE）technique is used...A novel method is presented to evaluate the complicated fatigue behavior of gears made of20Cr2Ni4 A.Fatigue tests are conducted in a high-frequency push-pull fatigue tester,and acoustic emission（AE）technique is used to acquire metal fatigue signals.After analyzing large number of AE frequency spectrum,we find that：the crack extension can be expressed as the energy of specific frequency band,which is abbreviated as F-energy.To further validate the fatigue behavior,some correlation analysis is applied between F-energy and some AE parameters.Experimental results show that there is significant correlation among the Fenergy,root mean square（RMS）,relative energy,and hits.The findings can be used to validate the effectiveness of the F-energy in predicting fatigue crack propagation and remaining life for parts in-service.F-energy,as a new AE parameter,is first put forward in the area of fatigue crack growth.展开更多
This paper studies and compares the effects of pull-pull and 3-point bending cyclic loadings on the mechanical fa- tigue damage behaviors of a solder joint in a surface-mount electronic package. The comparisons are ba...This paper studies and compares the effects of pull-pull and 3-point bending cyclic loadings on the mechanical fa- tigue damage behaviors of a solder joint in a surface-mount electronic package. The comparisons are based on experimental investigations using scanning electron microscopy （SEM） in-situ technology and nonlinear finite element modeling, respec- tively. The compared results indicate that there are different threshold levels of plastic strain for the initial damage of solder joints under two cyclic applied loads; meanwhile, fatigue crack initiation occurs at different locations, and the accumulation of equivalent plastic strain determines the trend and direction of fatigue crack propagation. In addition, simulation results of the fatigue damage process of solder joints considering a constitutive model of damage initiation criteria for ductile materials and damage evolution based on accumulating inelastic hysteresis energy are identical to the experimental results. The actual fatigue life of the solder joint is almost the same and demonstrates that the FE modeling used in this study can provide an accurate prediction of solder joint fatigue failure.展开更多
文摘In order to increase the fatigue life (FL) of road wheels (RW), a kind of double layer rubber flange (DLRF) is put forward. It consists of two layers of rubber, where metal wires are laid in the inner layer and the outer layer has no inlaid metal wires. Stress, strain and temperature field of DLRF were calculated with ANSYS finite element analysis (FEA) software, FL of DLRF RW was also computed with fracture mechanics fatigue theory. The results of computation indicate that the heat generated in RW's rubber flange (RF) can be reduced by the use of DLRF, and the FL of RW can be increased without affecting the mechanical intensity of RW.
基金Supported by the NSF of China(69971016) Supported by the Shanghai Higher Learning Science Supported by the Technology Development Foundation(00JC14507)
文摘In present paper, we obtain the inverse moment estimations of parameters of the Birnbaum-Saunders fatigue life distribution based on Type-Ⅱ bilateral censored samples and multiply Type-Ⅱ censored sample. In this paper, we also get the interval estimations of the scale parameters.
基金Funded by the National Science and Technology Support Project of China (No. 2006BAA03B02-03)
文摘A method based on solution of the inverse heat conduction problem was presented for online stress monitoring and fatigue life analysis of boiler drums. The mathematical model of the drum temperature distribution is based on the assumptions that the difference of temperature along the longitudinal axis of the boiler drum is negligible with changes only in the radial direction and the circumferential direction, and that the outer surface of drum is thermaUy insulated. Combining this model with the control-volume method provides temperatures at different points on a cross-section of the drum. With the temperature data, the stresses and the life expectancy of the boiler drum are derived according to the ASME code. Applying this method to the cold start-up process of a 300 MW boiler demonstrated the absence of errors caused by the boundary condition assumptions on the inner surface of the drum and testified that the method is an applicable technique for the online stress monitoring and fatigue life analysis of boiler drums.
基金supported by aproject funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Based on the transfer matrix method and Forman equation,a new method is proposed to conduct the modal and fatigue life analysis of a beam with multiple transverse cracks.In the modal analysis,the damping loss factor is introduced by the complex elastic modulus,bending springs without mass are used to replace the transverse cracks,and the characteristic transfer matrix of the whole cracked beam can be derived.In the fatigue life analysis,considering the interaction of the beam vibration and fatigue cracks growth,the fatigue life of the cracked beam is predicted by the timing analysis method.Numerical calculation shows that cracks have a significant influence on the modal and fatigue life of the beam.
基金Supported by the NSF of China(69971016)Supported by the Shanghai Higher Learning Science and Technology Development Foundation(04DB24)
文摘In present paper, we derive the quasi-least squares estimation(QLSE) and approximate maximum likelihood estimation(AMLE) for the Birnbaum-Saunders fatigue life distribution under multiply Type-Ⅱcensoring. Furthermore, we get the variance and covariance of the approximate maximum likelihood estimation.
基金supported by the Aviation Science Foundation of China(No.20150252003)
文摘Vibration fatigue is one of the main failure modes of blade.The vibration fatigue life of blade is scattered caused by manufacture error,material property dispersion and external excitation randomness.A new vibration fatigue probabilistic life prediction model(VFPLPM)and a prediction method are proposed in this paper.Firstly,as one-dimensional volumetric method(ODVM)only considers the principle calculation direction,a three-dimensional space vector volumetric method(TSVVM)is proposed to improve fatigue life prediction accuracy for actual threedimensional engineering structure.Secondly,based on the two volumetric methods(ODVM and TSVVM),the material C-P-S-N fatigue curve model(CFCM)and the maximum entropy quantile function model(MEQFM),VFPLPM is established to predict the vibration fatigue probabilistic life of blade.The VFPLPM is combined with maximum stress method(MSM),ODVM and TSVVM to estimate vibration fatigue probabilistic life of blade simulator by finite element simulation,and is verified by vibration fatigue test.The results show that all of the three methods can predict the vibration fatigue probabilistic life of blade simulator well.VFPLPM &TSVVM method has the highest computational accuracy for considering stress gradient effect not only in the principle calculation direction but also in other space vector directions.
文摘A method and procedure of high cycle fatigue life prediction for helicopter transmission system tail gearbox casing is presented, including fatigue test load, three parameters S-N curve, reduction factor and cumulative damage law. According to the fatigue test results, the design load spectrum and the three parameters S-N curve, a fatigue life prediction of the tail gearbox casing of a helicopter is performed as an example.
文摘This paper investigates theoretically the influence of magnetization on fatigue life by using non-equilibrium statistical theory of fatigue fracture for metals. The fatigue microcrack growth rate is obtained from the dynamic equation of microcrack growth, where the influence of magnetization is described by an additional term in the potential energy of microcrack. The statistical value of fatigue life of metal under magnetic field is derived, which is expressed in terms of magnetic field and macrophysical as well as microphysical quantities. The fatigue life of AISI 4140 steel in static magnetic field from this theory is basically consistent with the experimental data.
文摘A fatigue damage model is developed for evaluating accumulative fatigue damage of dumpers. The loading spectrums acted on dumpers are created according to measured strain data in field. The finite element analysis is carried out for assessing stress distribution and strength characteristics of dumpers. Fatigue damage indexes and service life are calculated by a modified Palmgren-Miner rule. The investigation shows that fatigue notch factor has a significant influence on the calculation of fatigue damage of dumpers.
文摘The effects of laser shock peening (LSP) on improving fatigue life of aluminum alloy 7050 are investigated.Surface hardness is increased corresponding to a high dislocation density induced by LSP.The X-ray diffraction stress measurement shows that LSP results in prominent increase of surface compressive stress,quasi-symmetrically distributed in the laser peened region.The fatigue life of the alloy 7050 in rivet fastener hole structure is notably improved owing to LSP.The sequence of LSP and fastener hole preparation also influence the fatigue cycle life of the alloy.
基金Supported by the National Natural Science Foundation of China(50975030)
文摘A novel method is presented to evaluate the complicated fatigue behavior of gears made of20Cr2Ni4 A.Fatigue tests are conducted in a high-frequency push-pull fatigue tester,and acoustic emission（AE）technique is used to acquire metal fatigue signals.After analyzing large number of AE frequency spectrum,we find that：the crack extension can be expressed as the energy of specific frequency band,which is abbreviated as F-energy.To further validate the fatigue behavior,some correlation analysis is applied between F-energy and some AE parameters.Experimental results show that there is significant correlation among the Fenergy,root mean square（RMS）,relative energy,and hits.The findings can be used to validate the effectiveness of the F-energy in predicting fatigue crack propagation and remaining life for parts in-service.F-energy,as a new AE parameter,is first put forward in the area of fatigue crack growth.
基金Project supported by the National Basic Research Program of China(Grant No.2010CB631006)the National Natural Science Foundation of China(GrantNos.11072124 and 11272173)
文摘This paper studies and compares the effects of pull-pull and 3-point bending cyclic loadings on the mechanical fa- tigue damage behaviors of a solder joint in a surface-mount electronic package. The comparisons are based on experimental investigations using scanning electron microscopy （SEM） in-situ technology and nonlinear finite element modeling, respec- tively. The compared results indicate that there are different threshold levels of plastic strain for the initial damage of solder joints under two cyclic applied loads; meanwhile, fatigue crack initiation occurs at different locations, and the accumulation of equivalent plastic strain determines the trend and direction of fatigue crack propagation. In addition, simulation results of the fatigue damage process of solder joints considering a constitutive model of damage initiation criteria for ductile materials and damage evolution based on accumulating inelastic hysteresis energy are identical to the experimental results. The actual fatigue life of the solder joint is almost the same and demonstrates that the FE modeling used in this study can provide an accurate prediction of solder joint fatigue failure.
