First, Wirsching's model, which is widely employed in fatigue reliability anlysis of marine and offshore structures, is analysed systematically. It is found that the very important random variable A in Wirsching...First, Wirsching's model, which is widely employed in fatigue reliability anlysis of marine and offshore structures, is analysed systematically. It is found that the very important random variable A in Wirsching's model can not be directly determined from fatigue experiment because of the irreversibility of fatigue test, and in fact, what Wirsching studied from testing results is not A but a of the statistical Miner's rule. Second, by use of the statistical Miner's rule, a modified Wirsching's model is proposed. Thirdly and more importantly, based on the two-dimensional probabilistic Miner's rule, a new model is established for fatigue reliability analysis of structural components subjected to specified cyclic loading of variable amplitude or stochastic time history. In the end, an example is presented, from which it will be seen that this new model is very convenient to use and feasible to engineering practice.展开更多
Multiple failuremodes and strength degradation are usually inherent in the gear transmission system,which brings new challenges for conducting fatigue reliability analysis and design.This paper proposes a novel dynami...Multiple failuremodes and strength degradation are usually inherent in the gear transmission system,which brings new challenges for conducting fatigue reliability analysis and design.This paper proposes a novel dynamic fatigue reliability analysis method for failure dependence and strength degradation based on the combination of theCopula function and Gamma process.Firstly,the dynamic simulation model of the gear transmission system is established to obtain the dynamic stress-time history.The Gamma process is then used to describe the strength degradation to establish the dynamic stress-strength interference model.The marginal distribution functions of tooth contact fatigue and dedendumbending fatigue are calculated respectively based on the dynamic interferencemodel.Finally,the joint distribution of the two failure modes can be obtained by the t-Copula function to characterize the failure dependence,and so the dynamic fatigue reliability considering failure dependence can be estimated.The effectiveness of the proposed method is illustrated with examples.The results reveal the temporal law of reliability and the effects of failure dependence on dynamic fatigue reliability.展开更多
The aim of this paper is to evaluate the fatigue reliability with hybrid uncertain parameters based on a residual strength model. By solving the non-probabilistic setbased reliability problem and analyzing the reliabi...The aim of this paper is to evaluate the fatigue reliability with hybrid uncertain parameters based on a residual strength model. By solving the non-probabilistic setbased reliability problem and analyzing the reliability with randomness, the fatigue reliability with hybrid parameters can be obtained. The presented hybrid model can adequately consider all uncertainties affecting the fatigue reliability with hybrid uncertain parameters. A comparison among the presented hybrid model, non-probabilistic set-theoretic model and the conventional random model is made through two typical numerical examples. The results show that the presented hybrid model, which can ensure structural security, is effective and practical.展开更多
The blade root fatigue is one of important failure modes of turbocharger turbine for vehicle application,and the reliability and life of turbine with blade root fatigue failure mode are studied.Firstly,the stress char...The blade root fatigue is one of important failure modes of turbocharger turbine for vehicle application,and the reliability and life of turbine with blade root fatigue failure mode are studied.Firstly,the stress characteristics of turbine are analyzed,and based on the operating profile of turbocharger corresponding to the endurance test of engine,the stress spectrum of turbine with blade root fatigue failure mode is studied with the simulation method.Then,with the number of endurance test profile cycle as the life parameter,the reliability model and failure rate model of turbine with blade root fatigue failure mode are derived respectively. Finally,the rules that the reliability and failure rate of turbine with the blade root fatigue failure mode changes as life parameters are studied,and the life probabilistic characteristics of turbine are also studied.展开更多
Due to bad working conditions and complicated structure,kinds of complicated cycle loads work on turbine disc, and it's difficult to determine the stress distribution of their equivalent load.Based on the traditio...Due to bad working conditions and complicated structure,kinds of complicated cycle loads work on turbine disc, and it's difficult to determine the stress distribution of their equivalent load.Based on the traditional stress-strength interference model and conditional reliability,the reliability models of turbine disc without the stress distribution are established in this paper. In the range of fatigue limit, by improving fatigue life curve, the relationship between turbine disc's life probability distribution and material GH4133B's is got,and so is the relationship between life and stress.Then,on the basis of test data of smooth material test-piece from references,the fatigue life probability distribution of material testpiece is found out,and then the fatigue life probability distribution of turbine disc is confirmed. The fatigue life probability distribution of turbine disc is taken into reliability model and the reliability of turbine is analyzed disc under random loads. And this analysis result confirms the variation trend of engine's reliability.展开更多
in reliability design of fatigue under random loading, the influence of loading se-quence must be considered. In order to avoid the uneertain hypothesis in the Miner's rule, ie. thatthe sum of damage equals one re...in reliability design of fatigue under random loading, the influence of loading se-quence must be considered. In order to avoid the uneertain hypothesis in the Miner's rule, ie. thatthe sum of damage equals one represents failure, this paper proposes the probabilistic relativeMine's rule. This paper also presents a new method for calculating reliability, ie. the syntheticmethod of Miner's rule and interference model. This model considers not only the influence ofstress concentration, dimension and surface, but also the influence of stress amplitude and se-quence.展开更多
A method is presented for estimating fatigue reliability under variable loading, which isbased on load cycles-fatigue life interference theory as well as cumulative fatigue damageanalysis. The basic opinion is that fo...A method is presented for estimating fatigue reliability under variable loading, which isbased on load cycles-fatigue life interference theory as well as cumulative fatigue damageanalysis. The basic opinion is that for variable loading the increment of failure probability pro-duced by each load cycle is determined by the stress level as well as the damage state at whichthis load cycle applies Contrast to 'conditional reliability-equivalent life methodology'. this meth-od calculates the equivalent cycle numbers between different stress levels according to cumulativefatigue damage rule but not equivalent failure probability.展开更多
Fatigue failure of gear transmission is one of the key factors that restrict the performance and service life of wind turbines.One of the major concerns in gear transmission under random loading conditions is the disr...Fatigue failure of gear transmission is one of the key factors that restrict the performance and service life of wind turbines.One of the major concerns in gear transmission under random loading conditions is the disregard of dynamic fatigue reliability in conventional design methods.Various issues,such as overweight structure or insufficient fatigue reliability,require continuous improvements in the reliability-based design optimization(RBDO)methodology.In this work,a novel gear transmission optimization model based on dynamic fatigue reliability sensitivity is developed to predict the optimal structural parameters of a wind turbine gear transmission.In the model,the dynamic fatigue reliability of the gear transmission is evaluated based on stress–strength interference theory.Design variables are determined based on the reliability sensitivity and correlation coefficient of the initial design parameters.The optimal structural parameters with the minimum volume are identified using the genetic algorithm in consideration of the dynamic fatigue reliability constraints.Comparison of the initial and optimized structures shows that the volume decreases by 3.58%while ensuring fatigue reliability.This work provides new insights into the RBDO of transmission systems from the perspective of reliability sensitivity.展开更多
A new method for welded joint fatigue reliability analysis on bogie frame of high-speed electric multiple unit(EMU) is proposed according to the International Union of Railways(UIC) standard, the Britain Standard Inst...A new method for welded joint fatigue reliability analysis on bogie frame of high-speed electric multiple unit(EMU) is proposed according to the International Union of Railways(UIC) standard, the Britain Standard Institute(BSI) standard and the Miner rule. Firstly, the fatigue calculation condition is loaded according to the UIC standard. The welded joint damage ratio is calculated by the BSI standard. Fatigue reliability analysis is conducted for a typical welded joint based on probabilistic design system(PDS) module in software ANSYS 14.0.In the system, the automatic program is prepared by ANSYS parametric design language(APDL) to calculate the welded joint fatigue damage ratio. Meantime, the relationship between the input variables and the output response is fitted by the response surface(RS) method. Then, the RS method is improved by the orthogonal design.Specifically, the selecting process optimization for the RS method based on the orthogonal design is conducted to improve the fitting efficiency of the RS method. Finally, a program of the automatic analysis documents is generated by Microsoft foundation class(MFC) technique. Through the self-defined interface, the researchers can easily import the automatic generation of the orthogonal table into the PDS module and analyze the fatigue reliability. Results show that the improved RS method can better fit the RS which covers the sample area, and the distribution law agrees well with the actual situation. At the same time, the improved RS method reduces the calculation time.展开更多
First of all, the concept of γ_p_S a_S m_N (confidence level_reliability_stress amplitude_stress mean_fatigue life) surface is presented. Then the formulas of p_S a_S m_N surface and γ_p_S a_S m_N ...First of all, the concept of γ_p_S a_S m_N (confidence level_reliability_stress amplitude_stress mean_fatigue life) surface is presented. Then the formulas of p_S a_S m_N surface and γ_p_S a_S m_N surface are derived. In addition, fatigue strength distribution function and two_dimensional reliability Miner rule are obtained. At last, an example is given.展开更多
The fuzzy sets theory is introduced into the fatigue reliability analysis. The concepts of maximizing set and minimizing set are developed to decide the ordering value of each fuzzy number, and these values can be use...The fuzzy sets theory is introduced into the fatigue reliability analysis. The concepts of maximizing set and minimizing set are developed to decide the ordering value of each fuzzy number, and these values can be used to determine the order of the fuzzy numbers. On the basis of the works mentioned above, the membership function defining the fuzzy safety event can be calculated, and then the fuzzy reliability in the case of stress and fuzzy fatigue strength is deduced. An example is given to illustrate the method.展开更多
The cyclic stress-strain responses (CSSR), Neuber's rule (NR) and cyclic strain-life relation (CSLR) are treated as probabilistic curves in local stress and strain method of low cycle fatigue analysis. The randomn...The cyclic stress-strain responses (CSSR), Neuber's rule (NR) and cyclic strain-life relation (CSLR) are treated as probabilistic curves in local stress and strain method of low cycle fatigue analysis. The randomness of loading and the theory of fatigue damage accumulation (TOFDA) are considered. The probabilistic analysis of local stress, local strain and fatigue life are constructed based on the first-order Taylor's series expansions. Through this method proposed fatigue reliability analysis can be accomplished.展开更多
This study aims at the reliability of a large vibration machine ZM2800, including the measurement and analysis of its dynamic load, the stress and reliability analysis of key fragile components as well as the system r...This study aims at the reliability of a large vibration machine ZM2800, including the measurement and analysis of its dynamic load, the stress and reliability analysis of key fragile components as well as the system reliability analysis and calculation of the machine. The result of the study provides valuable reference for the evaluation and improvement of the structure and performance of the machine.展开更多
In this paper, the problem of reliability-based optimal design of simple offshore platform is studied, and a nonlinear fatigue damage model based on damage mechanics and genetic algorithms are used in the fatigue reli...In this paper, the problem of reliability-based optimal design of simple offshore platform is studied, and a nonlinear fatigue damage model based on damage mechanics and genetic algorithms are used in the fatigue reliability optimum design of the structure under stochastic wave load. The fatigue damage model and the yield failure reliability analyzing model are used in the paper. The reliability of the models and the effectiveness of genetic algorithm are shown by the results of optimum design.展开更多
Previous studies have shown that the fatigue life distribution of metal materials fabricated with Additive Manufacturing(AM) methods, such as Direct Energy Deposited(DED) Ti-6.5Al-2Zr-1Mo-1V alloys, exhibits two peaks...Previous studies have shown that the fatigue life distribution of metal materials fabricated with Additive Manufacturing(AM) methods, such as Direct Energy Deposited(DED) Ti-6.5Al-2Zr-1Mo-1V alloys, exhibits two peaks. To promote the application of AM in aerospace and other engineering fields, developing a fatigue strength evaluation method suitable for AM materials based on their unique fatigue behaviours and fatigue life distributions is necessary. In this paper, a novel Detail Fatigue Rating(DFR) method was developed to evaluate the fatigue strength of DED Ti-6.5Al-2Zr-1Mo-1V based on a bimodal Weibull distribution and the excessive restriction on the allowable stress of potential was improved. Meanwhile, a Bimodal Weibull distribution model for fatigue life and its parameter estimation method were established based on a twoparameter Weibull distribution. The fatigue life at a specific reliability level and confidence level was calculated by using the bootstrap method. The calculation results showed that fatigue life estimated by using the bimodal Weibull distribution at the high reliability level and high confidence level is higher than that estimated by using the two-parameter Weibull distribution. Furthermore,The S-N curve at the specified confidence level and reliability level was fitted.展开更多
基金This project was financially supported by the National Science Foundation of China(59605010)and the Postdoctoral Science Foundation of China
文摘First, Wirsching's model, which is widely employed in fatigue reliability anlysis of marine and offshore structures, is analysed systematically. It is found that the very important random variable A in Wirsching's model can not be directly determined from fatigue experiment because of the irreversibility of fatigue test, and in fact, what Wirsching studied from testing results is not A but a of the statistical Miner's rule. Second, by use of the statistical Miner's rule, a modified Wirsching's model is proposed. Thirdly and more importantly, based on the two-dimensional probabilistic Miner's rule, a new model is established for fatigue reliability analysis of structural components subjected to specified cyclic loading of variable amplitude or stochastic time history. In the end, an example is presented, from which it will be seen that this new model is very convenient to use and feasible to engineering practice.
基金the National Natural Science Foundation of China under Contract No.51875073the Scientific Research Project of Education Department of Liaoning Province under Contract No.JDL2019005+1 种基金the Dalian Science and Technology Innovation Fund Plan under Contract No.2019J11CY017the Innovation Team Support Plan of Liaoning Higher Education under Contract No.LT2016010.
文摘Multiple failuremodes and strength degradation are usually inherent in the gear transmission system,which brings new challenges for conducting fatigue reliability analysis and design.This paper proposes a novel dynamic fatigue reliability analysis method for failure dependence and strength degradation based on the combination of theCopula function and Gamma process.Firstly,the dynamic simulation model of the gear transmission system is established to obtain the dynamic stress-time history.The Gamma process is then used to describe the strength degradation to establish the dynamic stress-strength interference model.The marginal distribution functions of tooth contact fatigue and dedendumbending fatigue are calculated respectively based on the dynamic interferencemodel.Finally,the joint distribution of the two failure modes can be obtained by the t-Copula function to characterize the failure dependence,and so the dynamic fatigue reliability considering failure dependence can be estimated.The effectiveness of the proposed method is illustrated with examples.The results reveal the temporal law of reliability and the effects of failure dependence on dynamic fatigue reliability.
基金supported by the National Natural Science Foundation of China (90816024, 10872017 and 10876100)the 111 Project (B07009)the Innovation Foundation of Beihang University for PhD Graduates
文摘The aim of this paper is to evaluate the fatigue reliability with hybrid uncertain parameters based on a residual strength model. By solving the non-probabilistic setbased reliability problem and analyzing the reliability with randomness, the fatigue reliability with hybrid parameters can be obtained. The presented hybrid model can adequately consider all uncertainties affecting the fatigue reliability with hybrid uncertain parameters. A comparison among the presented hybrid model, non-probabilistic set-theoretic model and the conventional random model is made through two typical numerical examples. The results show that the presented hybrid model, which can ensure structural security, is effective and practical.
基金National Natural Science Foundation of China(No.51375465)
文摘The blade root fatigue is one of important failure modes of turbocharger turbine for vehicle application,and the reliability and life of turbine with blade root fatigue failure mode are studied.Firstly,the stress characteristics of turbine are analyzed,and based on the operating profile of turbocharger corresponding to the endurance test of engine,the stress spectrum of turbine with blade root fatigue failure mode is studied with the simulation method.Then,with the number of endurance test profile cycle as the life parameter,the reliability model and failure rate model of turbine with blade root fatigue failure mode are derived respectively. Finally,the rules that the reliability and failure rate of turbine with the blade root fatigue failure mode changes as life parameters are studied,and the life probabilistic characteristics of turbine are also studied.
基金Foundation of China Academic Engineering Physics(No.2013B0203028)
文摘Due to bad working conditions and complicated structure,kinds of complicated cycle loads work on turbine disc, and it's difficult to determine the stress distribution of their equivalent load.Based on the traditional stress-strength interference model and conditional reliability,the reliability models of turbine disc without the stress distribution are established in this paper. In the range of fatigue limit, by improving fatigue life curve, the relationship between turbine disc's life probability distribution and material GH4133B's is got,and so is the relationship between life and stress.Then,on the basis of test data of smooth material test-piece from references,the fatigue life probability distribution of material testpiece is found out,and then the fatigue life probability distribution of turbine disc is confirmed. The fatigue life probability distribution of turbine disc is taken into reliability model and the reliability of turbine is analyzed disc under random loads. And this analysis result confirms the variation trend of engine's reliability.
文摘in reliability design of fatigue under random loading, the influence of loading se-quence must be considered. In order to avoid the uneertain hypothesis in the Miner's rule, ie. thatthe sum of damage equals one represents failure, this paper proposes the probabilistic relativeMine's rule. This paper also presents a new method for calculating reliability, ie. the syntheticmethod of Miner's rule and interference model. This model considers not only the influence ofstress concentration, dimension and surface, but also the influence of stress amplitude and se-quence.
文摘A method is presented for estimating fatigue reliability under variable loading, which isbased on load cycles-fatigue life interference theory as well as cumulative fatigue damageanalysis. The basic opinion is that for variable loading the increment of failure probability pro-duced by each load cycle is determined by the stress level as well as the damage state at whichthis load cycle applies Contrast to 'conditional reliability-equivalent life methodology'. this meth-od calculates the equivalent cycle numbers between different stress levels according to cumulativefatigue damage rule but not equivalent failure probability.
基金supported by the National Natural Science Foundation of China(Grant No.U1864210).
文摘Fatigue failure of gear transmission is one of the key factors that restrict the performance and service life of wind turbines.One of the major concerns in gear transmission under random loading conditions is the disregard of dynamic fatigue reliability in conventional design methods.Various issues,such as overweight structure or insufficient fatigue reliability,require continuous improvements in the reliability-based design optimization(RBDO)methodology.In this work,a novel gear transmission optimization model based on dynamic fatigue reliability sensitivity is developed to predict the optimal structural parameters of a wind turbine gear transmission.In the model,the dynamic fatigue reliability of the gear transmission is evaluated based on stress–strength interference theory.Design variables are determined based on the reliability sensitivity and correlation coefficient of the initial design parameters.The optimal structural parameters with the minimum volume are identified using the genetic algorithm in consideration of the dynamic fatigue reliability constraints.Comparison of the initial and optimized structures shows that the volume decreases by 3.58%while ensuring fatigue reliability.This work provides new insights into the RBDO of transmission systems from the perspective of reliability sensitivity.
基金the National Natural Science Foundation of China(No.11272070)the Natural Science Foundation of Liaoning Province(No.2014028020)+1 种基金the Dalian Science and Technology Project(No.2015A11GX026)the Educational Commission of Liaoning Province(No.JDL2016001)
文摘A new method for welded joint fatigue reliability analysis on bogie frame of high-speed electric multiple unit(EMU) is proposed according to the International Union of Railways(UIC) standard, the Britain Standard Institute(BSI) standard and the Miner rule. Firstly, the fatigue calculation condition is loaded according to the UIC standard. The welded joint damage ratio is calculated by the BSI standard. Fatigue reliability analysis is conducted for a typical welded joint based on probabilistic design system(PDS) module in software ANSYS 14.0.In the system, the automatic program is prepared by ANSYS parametric design language(APDL) to calculate the welded joint fatigue damage ratio. Meantime, the relationship between the input variables and the output response is fitted by the response surface(RS) method. Then, the RS method is improved by the orthogonal design.Specifically, the selecting process optimization for the RS method based on the orthogonal design is conducted to improve the fitting efficiency of the RS method. Finally, a program of the automatic analysis documents is generated by Microsoft foundation class(MFC) technique. Through the self-defined interface, the researchers can easily import the automatic generation of the orthogonal table into the PDS module and analyze the fatigue reliability. Results show that the improved RS method can better fit the RS which covers the sample area, and the distribution law agrees well with the actual situation. At the same time, the improved RS method reduces the calculation time.
文摘First of all, the concept of γ_p_S a_S m_N (confidence level_reliability_stress amplitude_stress mean_fatigue life) surface is presented. Then the formulas of p_S a_S m_N surface and γ_p_S a_S m_N surface are derived. In addition, fatigue strength distribution function and two_dimensional reliability Miner rule are obtained. At last, an example is given.
基金This project is supported by National Naied Science Foundation of China(59475043). Manuscript received on July 8,1999 revised m
文摘The fuzzy sets theory is introduced into the fatigue reliability analysis. The concepts of maximizing set and minimizing set are developed to decide the ordering value of each fuzzy number, and these values can be used to determine the order of the fuzzy numbers. On the basis of the works mentioned above, the membership function defining the fuzzy safety event can be calculated, and then the fuzzy reliability in the case of stress and fuzzy fatigue strength is deduced. An example is given to illustrate the method.
文摘The cyclic stress-strain responses (CSSR), Neuber's rule (NR) and cyclic strain-life relation (CSLR) are treated as probabilistic curves in local stress and strain method of low cycle fatigue analysis. The randomness of loading and the theory of fatigue damage accumulation (TOFDA) are considered. The probabilistic analysis of local stress, local strain and fatigue life are constructed based on the first-order Taylor's series expansions. Through this method proposed fatigue reliability analysis can be accomplished.
文摘This study aims at the reliability of a large vibration machine ZM2800, including the measurement and analysis of its dynamic load, the stress and reliability analysis of key fragile components as well as the system reliability analysis and calculation of the machine. The result of the study provides valuable reference for the evaluation and improvement of the structure and performance of the machine.
基金This work was financially supported by the National Science Foundation of China
文摘In this paper, the problem of reliability-based optimal design of simple offshore platform is studied, and a nonlinear fatigue damage model based on damage mechanics and genetic algorithms are used in the fatigue reliability optimum design of the structure under stochastic wave load. The fatigue damage model and the yield failure reliability analyzing model are used in the paper. The reliability of the models and the effectiveness of genetic algorithm are shown by the results of optimum design.
基金the support from the National Key Research and Development Program of China(No.2017YFB1104003)National Natural Science Foundation of China(No.11772027)Aeronautical Science Foundation of China(No.201909051002)。
文摘Previous studies have shown that the fatigue life distribution of metal materials fabricated with Additive Manufacturing(AM) methods, such as Direct Energy Deposited(DED) Ti-6.5Al-2Zr-1Mo-1V alloys, exhibits two peaks. To promote the application of AM in aerospace and other engineering fields, developing a fatigue strength evaluation method suitable for AM materials based on their unique fatigue behaviours and fatigue life distributions is necessary. In this paper, a novel Detail Fatigue Rating(DFR) method was developed to evaluate the fatigue strength of DED Ti-6.5Al-2Zr-1Mo-1V based on a bimodal Weibull distribution and the excessive restriction on the allowable stress of potential was improved. Meanwhile, a Bimodal Weibull distribution model for fatigue life and its parameter estimation method were established based on a twoparameter Weibull distribution. The fatigue life at a specific reliability level and confidence level was calculated by using the bootstrap method. The calculation results showed that fatigue life estimated by using the bimodal Weibull distribution at the high reliability level and high confidence level is higher than that estimated by using the two-parameter Weibull distribution. Furthermore,The S-N curve at the specified confidence level and reliability level was fitted.