Dynamic Reliability Evaluation and Life Prediction of Transmission System of Multi-Performance Degraded Wind Turbine

Wind power is a kind of important green energy.Thus,wind turbines have been widely utilized around the world.Wind turbines are composed of many important components.Among these components,the failure rate of the transmission system is relatively high in wind turbines.It is because the components are subjected to aerodynamic loads for a long time.In addition,its inertial load will result in fatigue fracture,wear and other problems.In this situation,wind turbines have to be repaired at a higher cost.Moreover,the traditional reliability methods are difficult to deal with the above challenges when performing the reliability analysis of the transmission system of wind turbines.To solve this problem,a stress-strength interference model based on performance degradation is introduced.Based on considering the strength degradation of each component,the improved Monte Carlomethod simulation based on the Back Propagation neural network is used to obtain the curve of system reliability over time.Finally,the Miner linear cumulative damage theory and the Carten-Dolan cumulative damage theory method are used to calculate the cumulative damage and fatigue life of the gear transmission system.

Dynamic Reliability Sensitivity of Cemented Carbide Cutting Tool

Influence of geometric and cutting parameters of cemented carbide cutting tool on reliability of cutting tool has become more and more mature, yet influence of its physical and material parameters on reliability is still blank. In view of this, cutting test and fatigue crack growth test of YT05 cemented carbide cutting tool are conducted to measure such data as the original crack size, growth size, times of impact loading, number and time of cutting tool in failure, and stress distribution of cutting tool is also obtained by simulating cutting process of tools. Mathematical models on dynamic reliability and dynamic reliability sensitivity of cutting tool are derived respectively by taking machining time and times of impact loading into account, thus change rules of dynamic reliability sensitivity to physical and material parameters can be obtained. Theoretical and experimental results show that sensitive degree on each parameter of tools increases gradually with the increase of machining time and times of impact loading, especially for parameters such as fracture toughness, shape parameter, and cutting stress. This proposed model solves such problems as how to determine the most sensitive parameter and influence degree of physical parameters and material parameters to reliability, which is sensitivity, and can provide theoretical foundation for improving reliability of cutting tool system.

Performance-based global reliability assessment of a high-rise frame-core tube structure subjected to multi-dimensional stochastic earthquakes

When evaluating the seismic safety and reliability of complex engineering structures,it is a critical problem to reasonably consider the randomness and multi-dimensional nature of ground motions.To this end,a proposed modeling strategy of multi-dimensional stochastic earthquakes is addressed in this study.This improved seismic model has several merits that enable it to better provide seismic analyses of structures.Specifically,at first,the ground motion model is compatible with the design response spectrum.Secondly,the evolutionary power spectrum involved in the model and the design response spectrum are constructed accordingly with sufficient consideration of the correlation between different seismic components.Thirdly,the random function-based dimension-reduction representation is applied,by which seismic modeling is established,with three elementary random variables.Numerical simulations of multi-dimensional stochastic ground motions in a specific design scenario indicate the effectiveness of the proposed modeling strategy.Moreover,the multi-dimensional seismic response and the global reliability of a high-rise frame-core tube structure is discussed in detail to further illustrate the engineering applicability of the proposed method.The analytical investigations demonstrate that the suggested stochastic model of multi-dimensional ground motion is available for accurate seismic response analysis and dynamic reliability assessment of complex engineering structures for performance-based seismic resistance design.

Dynamic Fatigue Reliability Analysis of Transmission Gear Considering Failure Dependence

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.

Reliability Evaluation and Sensitivity Analysis for Multi-state System Based on Time Degradation Measures

The performance and state of multi-state system depend on its structure and different state combinations of the components. In order to evaluate the reliability of multi-state system effectively,a reliability evaluation and sensitivity analysis method based on the time degradation measures was proposed. The equivalence sets of the multi-state system under different output performances were established. The state combinations were classified according to the performance level. The degradation probability models under different states were established,and the new reliability measures,such as dynamic probability of multi-state system,holding time in each state,dynamic expectation function and integrated expectation function of the performance,were proposed and used to implement the dynamic reliability evaluation and sensitivity analysis. A certain diesel engine fuel feeding system was taken as an application example to illustrate the proposed method. The results show that not only the holding time in the desired state of the components and the system can be predicted,but also the best state component in a certain time period can be obtained.

Dynamic Reliability Analysis of Braced Frame Structures Considering Inter Story Correlation

Adding buckling restrained braces(BRB)of reinforced concrete frame structure can effectively improve the safety performance of the structure.The dynamic reliability analysis based on Poisson continuous process assumption and the first exceeding failure probability can be used to obtain the failure probability of the buckling restrained brace frame system under earthquake load,and the relationship between the failure probabilities of each floor of the structure is analyzed to obtain the frame system reliability interval of frame structure.The results show that the reliability of BRB frame structure is higher than that of pure frame structure,and the discrete failure probability is lower.

Dynamic Reliability Assessment of Heavy Vehicle Crossing a Prototype Bridge Deck by Using Simulation Technology and Health Monitoring Data

Overloads of vehicle may cause damage to bridge structures,and how to assess the safety influence of heavy vehicles crossing the prototype bridge is one of the challenges.In this report,using a large amount of monitored data collected from the structural health monitoring system(SHMS)in service of the prototype bridge,of which the bridge type is large-span continuous rigid frame bridge,and adopting FEM simulation technique,we suggested a dynamic reliability assessment method in the report to assess the safety impact of heavy vehicles on the prototype bridge during operation.In the first place,by using the health monitored strain data,of which the selected monitored data time range is before the opening of traffic,the quasi dynamic reliability around the embedded sensor with no traffic load effects is obtained;then,with FEM technology,the FEM simulation model of one main span of the prototype bridge is built by using ANSYS software and then the dynamic reliability when the heavy vehicles crossing the prototype bridge corresponding to the middle-span web plate is comprehensively analyzed and discussed.At last,assuming that the main beam stress state change is in the stage of approximately linear elasticity under heavy vehicle loads impact,the authors got the impact level of heavy vehicles effects on the dynamic reliability of the prototype bridge.Based on a large number of field measured data,the dynamic reliability value calculated by our proposed methodology is more accurate.The method suggested in the paper can do good for not only the traffic management but also the damage analysis of bridges.

Maintenance Strategy of Multi-Component System Due to Degradation and Shock

The proposed maintenance strategy uses component grades and survival signature to describe and update system structure. A system dynamic stress-strength reliability(SSR) model was established to describe component failure processes because of internal degradation and external shock. Besides, a corrective maintenance rule and two-level preventive maintenance rule made up the proposed maintenance strategy. The former combined sequentially minimal repair and corrective replacement(SMRCR) based on system structure updating. The latter considered group importance measure based on the system dynamic SSR and preventive maintenance cost. Further, a cost model was developed by the proposed strategy, and the optimal decision variables were found by genetic algorithm. Finally, using a case system to illustrate the above strategy improved system and reduced maintenance costs.

Progress in high-speed train technology around the world

This is a review of high-speed train development in the sense of technology advances all over the world. Three generations of high-speed trains are classified according to their technical characteristics and maximum operating speed. Emphasis is given to the newly developed high-speed train in China, CRH380. The theoretical foundations and future development of CRH380 are briefly discussed.

Simulation-based automatic generation of risk scenarios

A methodology for automatically generating risk scenarios is presented.Its main idea is to let the system model ＂express itself＂ through simulation.This is achieved by having the simulation model driven by an elaborated simulation engine,which：（i） manipulates the generation of branch points,i.e.event occurrence times;（ii） employs a depth-first systematic exploration strategy to cover all possible branch paths at each branch point.In addition,a backtracking technique,as an extension,is implemented to recover some missed risk scenarios.A widely discussed dynamic reliability example（a holdup tank） is used to aid in the explanation of and to demonstrate the effectiveness of the proposed methodology.

Simulation and uniform design-based automatic generation of risk scenarios

This paper presents a methodology for automatically generating risk scenarios for dynamic reliability applications in which some dynamic characteristics(e.g.,the order,timing and magnitude of events,the value of relevant process parameters and initial conditions) have a significant influence on the evolution of the system.The main idea of the methodology is:(i) making the system model "express itself" through simulation by having the model driven by an elaborated simulation engine;(ii) exploiting uniform design to pick out a small subset of representative design points from the space of relevant dynamic characteristics;(iii) for each selected design point,employing a depth-first systematic exploration strategy to cover all possible scenario branches at each branch point.A highly dynamic example adapted from the literature(a chemical batch reactor) is studied to test the effectiveness of the proposed methodology.

Reliability analysis on civil engineering project based on integrated adaptive simulation annealing and gray correlation method

Dynamic reliability is a very important issue in reliability research. The dynamic reliability analysis for the project is still in search of domestic and international research in the exploration stage. By now, dynamic reliability research mainly concentrates on the reliability assessment; the methods mainly include dynamic fault tree, extension of event sequence diagram and Monte Carlo simulation, and et al. The paper aims to research the dynamic reliability optimization. On the basis of analysis of the four quality influence factors in the construction engineering, a method based on gray correlation degree is employed to calculate the weights of factors affecting construction process quality. Then the weights are added into the reliability improvement feasible index （RIFI）. Furthermore, a novel nonlinear programming mathematic optimization model is established. In the Insight software environment, the Adaptive Simulated Annealing （ASA） algorithm is used to get a more accurate construction subsystem optimal reliability under different RIFI conditions. In addition, the relationship between construction quality and construction system reliability is analyzed, the proposed methods and detailed processing can offer a useful reference for improving the construction system quality level.

Dynamic stress–strength reliability estimation of system with survivalsignature

In this paper, we proposed a dynamic stress–strength model for coherent system. It is supposedthat the system consists of n components with initial random strength and each component issubjected to random stresses. The stresses, applied repeatedly at random cycle times, will causethe degradation of strength. In addition, the number of cycles in an interval is assumed to followa Poisson distribution. In the case of the strength and stress random variables following exponential distributions, the expression for the reliability of the proposed dynamic stress–strengthmodel is derived based on survival signature. The reliability is estimated by using the best linearunbiased estimation (BLUE). Considering the Type-II censored failure times, the best linear unbiased predictors (BLUP) for the unobserved coherent system failure times are developed basedon the observed failure times. Monte Carlo simulations are performed to compare the BLUE ofparameters with different values and compute the BLUP. A real data set is also analysed for anillustration of the findings.

A novel imprecise stochastic process model for time-variant or dynamic uncertainty quantification

This paper proposes a novel model named as “imprecise stochastic process model” to handle the dynamic uncertainty with insufficient sample information in real-world problems. In the imprecise stochastic process model, the imprecise probabilistic model rather than a precise probability distribution function is employed to characterize the uncertainty at each time point for a time-variant parameter, which provides an effective tool for problems with limited experimental samples. The linear correlation between variables at different time points for imprecise stochastic processes is described by defining the auto-correlation coefficient function and the crosscorrelation coefficient function. For the convenience of analysis, this paper gives the definition of the P-box-based imprecise stochastic process and categorizes it into two classes: parameterized and non-parameterized P-box-based imprecise stochastic processes. Besides, a time-variant reliability analysis approach is developed based on the P-box-based imprecise stochastic process model,through which the interval of dynamic reliability for a structure under uncertain dynamic excitations or time-variant factors can be obtained. Finally, the effectiveness of the proposed method is verified by investigating three numerical examples.