The conventional stress-strength interference（SSI） model is a basic model for reliability analysis of mechanical components. In this model, the component reliability is defined as the probability of the strength bei...The conventional stress-strength interference（SSI） model is a basic model for reliability analysis of mechanical components. In this model, the component reliability is defined as the probability of the strength being larger than the stress, where the component stress is generally represented by a single random variable（RV）. But for a component under multi-operating conditions, its reliability can not be calculated directly by using the SSI model. The problem arises from that the stress on a component under multi-operating conditions can not be described by a single RV properly. Current research concerning the SSI model mainly focuses on the calculation of the static or dynamic reliability of the component under single operation condition. To evaluate the component reliability under multi-operating conditions, this paper uses multiple discrete RVs based on the actual stress range of the component firstly. These discrete RVs have identical possible values and different corresponding probability value, which are used to represent the multi-operating conditions of the component. Then the component reliability under each operating condition is calculated, respectively, by employing the discrete SSI model and the universal generating function technique, and from this the discrete SSI model under multi-operating conditions is proposed. Finally the proposed model is applied to evaluate the reliability of a transmission component of the decelerator installed in an aeroengine. The reliability of this component during taking-off, cruising and landing phases of an aircraft are calculated, respectively. With this model, a basic method for reliability analysis of the component under complex load condition is provided, and the application range of the conventional SSI model is extended.展开更多
In order to predict the lifetime of products appropriately with long lifetime and high reliability,the accelerated degradation testing(ADT)has been proposed.Composite wind turbine blade is one of the most important co...In order to predict the lifetime of products appropriately with long lifetime and high reliability,the accelerated degradation testing(ADT)has been proposed.Composite wind turbine blade is one of the most important components in wind turbine system.Its fatigue cycle is very long in practice.A full-scale fatigue testing is usually used to verify the design of a new blade.In general,the full-scale fatigue testing of blade is accelerated on the basis of the damage equivalent principle.During the full-scale fatigue test ing,blade is subjected to higher testing load than normal operat ing conditions;consequently,the performance degradation of the blade is hastened over time.The full-scale fatigue testing of blade is regarded as a special ADT.According to the fatigue failure criterion,we choose blade stiffness as the characteristic quantity of the blade performance,and propose an accelerated model(AM)for blade on the basis of the theories of ADT.Then,degradation path of the blade stiffness is modeled by using Gamma process.Finally,the lifet ime prediction of full-scale megawatt(MW)blade is conducted by combining the proposed AM and blade stiffness degradation model.The prediction results prove the reasonability and validity of this study.This can supply a new approach to predict the lifetime of the full-scale MW blade.展开更多
Residual strength is usually used to characterize the degradation rule of material performance under the cyclic load,which is critical to fatigue life prediction as well as reliability assessment of materials.In order...Residual strength is usually used to characterize the degradation rule of material performance under the cyclic load,which is critical to fatigue life prediction as well as reliability assessment of materials.In order to reveal the probability characteristics of residual strength of material under uncertain cyclic load,the relationship between external stress and fatigue life(i.e.,the equation of S-N curve)is considered in this study.Firstly,the probability density function of fatigue life under uncertain cyclic load is derived from the probability density function of external stress.Then,a probability model of residual strength is proposed on the basis of a fundamental assumption that the residual strength and the remaining life of material depend on the same damage state.Finally,the validity of the proposed model is verified by an illustrative example.The results indicate that the probability distribution of residual strength of material is affected by both the external factor(i.e.,probability characteristics of the load)and the internal factor(i.e.,fatigue performance parameters of material).展开更多
基金supported by National Hi-tech Research and Development Program of China (863 Program, Grant No. 2007AA04Z403)Sichuan Provincial Key Technologies R&D Program of China(Grant No. 07GG012- 002)+1 种基金Gansu Provincial Basal Research Fund of the Higher Education Institutions of China (Grant No. GCJ 2009019)Research Fund of Lanzhou University of Technology of China(Grant No. BS02200903)
文摘The conventional stress-strength interference（SSI） model is a basic model for reliability analysis of mechanical components. In this model, the component reliability is defined as the probability of the strength being larger than the stress, where the component stress is generally represented by a single random variable（RV）. But for a component under multi-operating conditions, its reliability can not be calculated directly by using the SSI model. The problem arises from that the stress on a component under multi-operating conditions can not be described by a single RV properly. Current research concerning the SSI model mainly focuses on the calculation of the static or dynamic reliability of the component under single operation condition. To evaluate the component reliability under multi-operating conditions, this paper uses multiple discrete RVs based on the actual stress range of the component firstly. These discrete RVs have identical possible values and different corresponding probability value, which are used to represent the multi-operating conditions of the component. Then the component reliability under each operating condition is calculated, respectively, by employing the discrete SSI model and the universal generating function technique, and from this the discrete SSI model under multi-operating conditions is proposed. Finally the proposed model is applied to evaluate the reliability of a transmission component of the decelerator installed in an aeroengine. The reliability of this component during taking-off, cruising and landing phases of an aircraft are calculated, respectively. With this model, a basic method for reliability analysis of the component under complex load condition is provided, and the application range of the conventional SSI model is extended.
基金the National Natural Science Founda-tion of China(No.51665029)。
文摘In order to predict the lifetime of products appropriately with long lifetime and high reliability,the accelerated degradation testing(ADT)has been proposed.Composite wind turbine blade is one of the most important components in wind turbine system.Its fatigue cycle is very long in practice.A full-scale fatigue testing is usually used to verify the design of a new blade.In general,the full-scale fatigue testing of blade is accelerated on the basis of the damage equivalent principle.During the full-scale fatigue test ing,blade is subjected to higher testing load than normal operat ing conditions;consequently,the performance degradation of the blade is hastened over time.The full-scale fatigue testing of blade is regarded as a special ADT.According to the fatigue failure criterion,we choose blade stiffness as the characteristic quantity of the blade performance,and propose an accelerated model(AM)for blade on the basis of the theories of ADT.Then,degradation path of the blade stiffness is modeled by using Gamma process.Finally,the lifet ime prediction of full-scale megawatt(MW)blade is conducted by combining the proposed AM and blade stiffness degradation model.The prediction results prove the reasonability and validity of this study.This can supply a new approach to predict the lifetime of the full-scale MW blade.
基金the National Natural Science Foundation of China(No.51665029)。
文摘Residual strength is usually used to characterize the degradation rule of material performance under the cyclic load,which is critical to fatigue life prediction as well as reliability assessment of materials.In order to reveal the probability characteristics of residual strength of material under uncertain cyclic load,the relationship between external stress and fatigue life(i.e.,the equation of S-N curve)is considered in this study.Firstly,the probability density function of fatigue life under uncertain cyclic load is derived from the probability density function of external stress.Then,a probability model of residual strength is proposed on the basis of a fundamental assumption that the residual strength and the remaining life of material depend on the same damage state.Finally,the validity of the proposed model is verified by an illustrative example.The results indicate that the probability distribution of residual strength of material is affected by both the external factor(i.e.,probability characteristics of the load)and the internal factor(i.e.,fatigue performance parameters of material).
