The rainflow counting method is a reasonable cyclecounting procedure for fatigue life calculation and simulation testing of structures.It defines cycles as closed stress /strain hysteresis loops.Application of the rai...The rainflow counting method is a reasonable cyclecounting procedure for fatigue life calculation and simulation testing of structures.It defines cycles as closed stress /strain hysteresis loops.Application of the rainflow counting method requires a data processing of the loading spectrum,which consists of the elimination of non-peak value data points,load time histories adjustment and loop extraction.In the data processing of the loading spectrum,if a stress point is neither the peak nor the valley,it will be identified and eliminated from the loading spectrum.Generally,the loading process is idealized as a single peak-valley straight line.But in actually,there are polylines or nearly straight lines between peaks and valleys which can't be ignored.Therefore,in the process of eliminating such data points,it will produce error in method itself.To reduce the error produced by the traditional method itself,a new method which can well simplify the polylines in data processing of loading spectrum is proposed in this paper.Comparing with the original approximation method,the proposed method has higher precision.展开更多
Some representative working conditions were measured, and the amplitude distribution rule of each representative working condition after analysis of measured data was got. The building of 2 D distributing function be...Some representative working conditions were measured, and the amplitude distribution rule of each representative working condition after analysis of measured data was got. The building of 2 D distributing function between the range and the mean of random load was discussed. Experiment was carried out to get the fatigue strength data of the material of transmission component. Accessing the P S a S m N camber of combined load of bending and torsion on this material after analysis. And the process of calculating the 2 D fatigue life in multi working condition was discussed.展开更多
Both wave-frequency(WF) and low-frequency(LF) components of mooring tension are in principle non-Gaussian due to nonlinearities in the dynamic system.This paper conducts a comprehensive investigation of applicable pro...Both wave-frequency(WF) and low-frequency(LF) components of mooring tension are in principle non-Gaussian due to nonlinearities in the dynamic system.This paper conducts a comprehensive investigation of applicable probability density functions(PDFs) of mooring tension amplitudes used to assess mooring-line fatigue damage via the spectral method.Short-term statistical characteristics of mooring-line tension responses are firstly investigated,in which the discrepancy arising from Gaussian approximation is revealed by comparing kurtosis and skewness coefficients.Several distribution functions based on present analytical spectral methods are selected to express the statistical distribution of the mooring-line tension amplitudes.Results indicate that the Gamma-type distribution and a linear combination of Dirlik and Tovo-Benasciutti formulas are suitable for separate WF and LF mooring tension components.A novel parametric method based on nonlinear transformations and stochastic optimization is then proposed to increase the effectiveness of mooring-line fatigue assessment due to non-Gaussian bimodal tension responses.Using time domain simulation as a benchmark,its accuracy is further validated using a numerical case study of a moored semi-submersible platform.展开更多
To evaluate the fatigue damage reliability of critical members of the Nanjing Yangtze river bridge, according to the stress-number curve and Miner’s rule, the corresponding expressions for calculating the structural ...To evaluate the fatigue damage reliability of critical members of the Nanjing Yangtze river bridge, according to the stress-number curve and Miner’s rule, the corresponding expressions for calculating the structural fatigue damage reliability were derived. Fatigue damage reliability analysis of some critical members of the Nanjing Yangtze river bridge was carried out by using the strain-time histories measured by the structural health monitoring system of the bridge. The corresponding stress spectra were obtained by the real-time rain-flow counting method. Results of fatigue damage were calculated respectively by the reliability method at different reliability and compared with Miner’s rule. The results show that the fatigue damage of critical members of the Nanjing Yangtze river bridge is very small due to its low live-load stress level.展开更多
This paper provides background information on fatigue and describes the methodology used in Creo Simulation （Pro/Mechanica） fatigue analysis. It covers history and physics of fatigue, the E-N approach-Strain Cycles ...This paper provides background information on fatigue and describes the methodology used in Creo Simulation （Pro/Mechanica） fatigue analysis. It covers history and physics of fatigue, the E-N approach-Strain Cycles Includes the effect of mean residual stresses, hysteresis loop capture and rainflow cycle counting. Factors that affect fatigue life include component size, loading type, surface finish, surface treatment and effect of surface treatments on endurance limit. This paper describes practical problem solution and fatigue strength analysis of the wing-hinge to fuselage connection in Creo Simulation （Pro/Mechanica） environment. It also includes a procedure for calculating the buckling load factor and failure index.展开更多
Firstly,the fatigue damages associated with the random loadings were always deemed as highcycle or very-high-cycle fatigue problems,and based on Chebyshev theorem,the number of rainflow cycles in a given time interval...Firstly,the fatigue damages associated with the random loadings were always deemed as highcycle or very-high-cycle fatigue problems,and based on Chebyshev theorem,the number of rainflow cycles in a given time interval could be recognized as a constant by neglecting its randomness.Secondly,the randomness of fatigue damage induced by the distribution of rainflow cycles was analyzed.According to central limit theorem,the fatigue damage could be assumed to follow Gaussian distribution,and the statistical parameters:mean and variance,were derived from Dirlik's solution.Finally,the proposed method was used to a simulate Gaussian random loading and the measured random loading from an aircraft.Comparisons with observed results were carried out extensively.In the first example,the relative errors of the proposed method are 2.29%,3.52%and 1.16%for the mean,standard deviation and variation coefficient of fatigue damage,respectively.In the second example,these relative errors are 11.70%,173.32%and 18.20%,and the larger errors are attributable to non-stationary state of the measured loading to some extent.展开更多
基金National Natural Science Foundation of China(No.11272082)
文摘The rainflow counting method is a reasonable cyclecounting procedure for fatigue life calculation and simulation testing of structures.It defines cycles as closed stress /strain hysteresis loops.Application of the rainflow counting method requires a data processing of the loading spectrum,which consists of the elimination of non-peak value data points,load time histories adjustment and loop extraction.In the data processing of the loading spectrum,if a stress point is neither the peak nor the valley,it will be identified and eliminated from the loading spectrum.Generally,the loading process is idealized as a single peak-valley straight line.But in actually,there are polylines or nearly straight lines between peaks and valleys which can't be ignored.Therefore,in the process of eliminating such data points,it will produce error in method itself.To reduce the error produced by the traditional method itself,a new method which can well simplify the polylines in data processing of loading spectrum is proposed in this paper.Comparing with the original approximation method,the proposed method has higher precision.
文摘Some representative working conditions were measured, and the amplitude distribution rule of each representative working condition after analysis of measured data was got. The building of 2 D distributing function between the range and the mean of random load was discussed. Experiment was carried out to get the fatigue strength data of the material of transmission component. Accessing the P S a S m N camber of combined load of bending and torsion on this material after analysis. And the process of calculating the 2 D fatigue life in multi working condition was discussed.
基金the financial support of the Major Program of the National Natural Science Foundation of China(No.51490675)the National Science Fund for Distinguished Young Scholars(No.51625902)+1 种基金the Taishan Scholars Program of Shandong Provincethe Fundamental Research Funds for the Central Universities(No.841713035)
文摘Both wave-frequency(WF) and low-frequency(LF) components of mooring tension are in principle non-Gaussian due to nonlinearities in the dynamic system.This paper conducts a comprehensive investigation of applicable probability density functions(PDFs) of mooring tension amplitudes used to assess mooring-line fatigue damage via the spectral method.Short-term statistical characteristics of mooring-line tension responses are firstly investigated,in which the discrepancy arising from Gaussian approximation is revealed by comparing kurtosis and skewness coefficients.Several distribution functions based on present analytical spectral methods are selected to express the statistical distribution of the mooring-line tension amplitudes.Results indicate that the Gamma-type distribution and a linear combination of Dirlik and Tovo-Benasciutti formulas are suitable for separate WF and LF mooring tension components.A novel parametric method based on nonlinear transformations and stochastic optimization is then proposed to increase the effectiveness of mooring-line fatigue assessment due to non-Gaussian bimodal tension responses.Using time domain simulation as a benchmark,its accuracy is further validated using a numerical case study of a moored semi-submersible platform.
基金Project(2001G025) supported by the Foundation of the Science and Technology Section of Ministry of Rail way of Chinaproject(2005) supported by the Postdoctoral Foundation of Central South University
文摘To evaluate the fatigue damage reliability of critical members of the Nanjing Yangtze river bridge, according to the stress-number curve and Miner’s rule, the corresponding expressions for calculating the structural fatigue damage reliability were derived. Fatigue damage reliability analysis of some critical members of the Nanjing Yangtze river bridge was carried out by using the strain-time histories measured by the structural health monitoring system of the bridge. The corresponding stress spectra were obtained by the real-time rain-flow counting method. Results of fatigue damage were calculated respectively by the reliability method at different reliability and compared with Miner’s rule. The results show that the fatigue damage of critical members of the Nanjing Yangtze river bridge is very small due to its low live-load stress level.
文摘This paper provides background information on fatigue and describes the methodology used in Creo Simulation （Pro/Mechanica） fatigue analysis. It covers history and physics of fatigue, the E-N approach-Strain Cycles Includes the effect of mean residual stresses, hysteresis loop capture and rainflow cycle counting. Factors that affect fatigue life include component size, loading type, surface finish, surface treatment and effect of surface treatments on endurance limit. This paper describes practical problem solution and fatigue strength analysis of the wing-hinge to fuselage connection in Creo Simulation （Pro/Mechanica） environment. It also includes a procedure for calculating the buckling load factor and failure index.
文摘Firstly,the fatigue damages associated with the random loadings were always deemed as highcycle or very-high-cycle fatigue problems,and based on Chebyshev theorem,the number of rainflow cycles in a given time interval could be recognized as a constant by neglecting its randomness.Secondly,the randomness of fatigue damage induced by the distribution of rainflow cycles was analyzed.According to central limit theorem,the fatigue damage could be assumed to follow Gaussian distribution,and the statistical parameters:mean and variance,were derived from Dirlik's solution.Finally,the proposed method was used to a simulate Gaussian random loading and the measured random loading from an aircraft.Comparisons with observed results were carried out extensively.In the first example,the relative errors of the proposed method are 2.29%,3.52%and 1.16%for the mean,standard deviation and variation coefficient of fatigue damage,respectively.In the second example,these relative errors are 11.70%,173.32%and 18.20%,and the larger errors are attributable to non-stationary state of the measured loading to some extent.
