Advanced Materials Research Vols. 945-949

Abstract: The thermal protection is a key factor to keep the gas generator work longtime under high temperature condition steadily. The main heat transfer paths are analyzed. A numeral simulation of the combustor and its nozzle shows the pipe outside temperature distribution with the change of time, position and thickness. According to the numeral simulation results, two thermal protection measures are bring forward, reduce the temperature, choosing proper thickness and heat resisting material. At last, an experiment results validate that the numeral simulation is credibility; the improvement of the structure is effective. With a longtime run, the outside wall temperature is 870K, which satisfies the operation needs.

Abstract: Blind source separation provides a new method for the separation of mechanical sources under high level background noise, as well as the diagnosis of the compound fault. At present, the blind source separation has been successfully applied to the mecanical fault diagnosis. But the traditional mechanical source separation methods are restricted to non-gauss, stationary and mutually independent source signals. However, the mechanical fault signals do not suffice to these conditions, and generally exhibit non-stationarity and non-independence. For the non-stationary signal, its spectral feature is time-varying. Thus only the time-domain or frequency-domain analysis is not sufficient to describe the characteristics of non-stationary signal. The time-frequency analysis, which can provide the information about that the spectrum of the signal varies with the time, is a useful tool for non-stationary signal analysis. In this paper, combined time-frequency analysis with blind source separation, a blind source separation method for the non-stationary signal of the mechanical equipment based on time-frequency analysis is proposed and studied. The simulation and experimental results show that the proposed approach is feasible and effective.

Abstract: For complex systems or items that experience multiple dependent competing failure processes, the dependency among the failure processes presents challenging issues in reliability modeling. This article, discusses the dependence of the degradation failure processes and the traumatic failure process. On the condition of passion shock processes, a degradation failure reliability model is developed with the wiener degradation processes. By the influence of the degradation, a traumatic failure reliability model is developed under weibull failure distribution. Then, we get system reliability model deals with mutual effect of the two processes. In additional, the parameters estimation of the reliability model is solved. An applied example demonstrated the model correctness and availability.

Abstract: Dynamic responses of a certain system could vary with the place, environment and time of use even if the system itself did not change. Traditionally, kinematical reliability analysis of a multi-body mechanism was a hard point in the reliability field. In order to obtain a large sample data of mechanism’s transient kinetic characteristics, it needed to take lots of time, labor and finance input to acquire. It reported an effective method used for mechanism kinetic reliability analysis, with the combination of VC++ and CAE software’s second develop program, it built a parametric virtual test model for complex mechanism system. Where, it used multiplicative congruent method to program a pseudo-random number function that conformed to normal distribution to simulate the stochastic error distribution of the mechanism, which was convenient for the Monte Carlo parametric modeling to obtain large sample data and calculate the system kinetic reliability.

Abstract: This paper briefly introduces the basic condition of power station boiler operation and failure analysis of the necessity of power plant boiler failure types and main components of power plant boiler failure types of main components. Illustrates the failure analysis of the main analysis method, and introduces the failure analysis of the role of failure analysis.

Abstract: Engine mechanical fault usually causes abnormal change of the body surface vibration signal. Cylinder surface vibration signals under normal condition, piston knocking fault condition and main bearing wear fault condition are analyzed with wavelet packet decomposition method, relative energy value of each frequency band can be calculated and then be regarded as the input vector to form the training sample, BP neural network model is used to identify the fault state, test data shows that this method can effectively recognize the fault types.

Abstract: Temperature induced degradation is a widely recognized failure phenomenon.However, the basic mechanisms that control the onset and progression of such behavior are not well understood and are a topic of considerable interest in the electrical connector community. In this paper, the simulation analysis of temperature field on this topic are described. The distribution graph of temperature field for the electrical connectors and the highest temperature of the surface of electrical connector was achieved by analyzing a single blade/receptacle contact pair FEA model. A mathematical model was developed that related the early stage temperature levels for the connectors.Additionally, the thermal deformation caused by the temperature had little effect on the contact stress based on temperature - structure coupling field analysis for the electrical connector, the impact of temperature on the electrical connector was mainly reflected in the rate of oxidation of the metal surface. The failure physical process of the electric connector was drawn under temperature stress through the model and theory analysis for the electrical connector , and reliability growth program of the electrical connector was achieved under the temperature influence. The same transfer functions for one type of contact pair were obtained from the simulation, and the results showed that for this limited system, finite element modeling and analysis have great potential for evaluating the influence of design variations on degradation behavior.

Abstract: Ship unloader crane was widely used in transportation, and uploaded or unloaded cargoes from ships, which could influence efficiency and benefits of transportation greatly. In order to improve the reliability and safety, and decrease its risk in working flow, a method of fatigue life assessment was proposed in this paper. According to related standards and properties of risk, finite element method and experimental stress analysis were integrated to assess the working condition of a ship unloader crane. Finite element models of primary structures subjected to loads were built to achieve dynamic properties, which could supply a basic reference to experiment and guidance to locate the tested positions. Afterwards, wireless dynamic resistance strain-gauges were adopted to execute static and dynamic stress, and the tested results combined with finite element analysis were applied to strength analysis. Based on nominal stress and Miner principle, rainflow method was developed to fatigue life assessment of this ship unloader crane. The final results indicated that residual life of this crane was 4.67 years.

Abstract: This paper simulated the unbalance vibration conditions by the vibration test platform, measuring some common characteristic parameters of unbalance vibration fault diagnosis. This paper chose the time-domain analysis method, processing the characteristic parameters of the test, so as to achieve the purpose of vibration diagnosis. Through a large number of experimental data, this paper verified the feasibility and the effectiveness of the proposed approach to the unbalance fault diagnosis. The method proposed in this paper not only can be applied to unbalance fault diagnosis, but also can be promoted to apply to the fault diagnosis of other rotating machinery.

Abstract: The reliability of security system affects the ability of the system to protect people's lives and property safety. Failure risk assessment of security system is an effective method to test the reliability of the system. The fault tree analysis method has been applied to analyze the system failure risk from the angle of each part and considering the human factors. The traditional fault tree analysis method assumes that the probability of bottom events is certain to calculate the top event probability. To obtain accurate bottom events probability is difficult, even impossible because statistical data is not sufficient and the bottom events is fuzzy in fact. Analysis of the fuzzy mathematics theory is introduced into the fault tree. The calculation provides reference for the system design and management.