Huang Hongzhong

A method of evaluating health state in rotary machinery

On the basis of state monitoring and fault diagnosis technology for equipments, the faults are classified according to the kind of deterioration of performance parameters, and the probability of the faults is analyzed. In this paper, the fault entropy of equipments is defined through the degree of membership of faults. Fault entropy reflects the probability which the faults of equipment may occur. Moreover, a new index is put forward which can comprehensively reflect the health state of equipments on the basis of the fault entropy and monitoring information of the equipment. This method is applied to evaluate the health state of hydraulic turbine and it shows that the method proposed in this paper is effective and practical.

Reliability modeling and analysis of complex multi-state system based on interval fuzzy Bayesian network

With the increasing complexity and large size of modern advanced engineering systems, the traditional reliability analysis and evaluation technology which is based on large number of sample data cannot meet the demand of complex system. Aiming at the engineering application requirement, this paper focuses on the reliability modeling and analysis of complex system with uncertainties and failure dependencies. Due to the diversity of input information and the system failure factors, and system redundancies, the uncertainty and common cause failure (CCF) have become the most important factors for reliability analysis and evaluation of complex system. In consideration of the epistemic uncertainty caused by lack of probability statistical information, the fuzzy theory is employed to express the fuzzy information of system, and the basic events failure probabilities are described by interval-valued fuzzy numbers. Taking account of the influence of CCF to system reliability and the widespread presence of MSS in engineering practices, the CCF is quantified by the β factor parameter model and integrated to Bayesian Network (BN) model through a new defined common cause node. Finally, a comprehensive method for reliability modeling and assessment of a multi-state system (MSS) with CCFs based on interval-valued fuzzy BN is proposed by taking the advantage of graphic representation and uncertainty reasoning of BN. The method has applied to the transmission system of two-axis positioning mechanism of a satellite antenna to demonstrate its effectiveness and capability for directly calculating the system reliability on the basis of multi-state probabilities of components. It has shown that the method proposed has done further improvement of the theory for reliability analysis of complex system and can realize its engineering application.

Probabilistic fatigue life prediction considering the uncertainty of S-N curve

The traditional fatigue life prediction methods based on the S-N curve recognize the parameters in life prediction models can be determined by experiment, simulation and fitting. That is to say, in a given loading environment, various parameters are treated as different constants, and then substitute these parameters into the model, the fatigue life can be obtained. This kind of methods treats the parameters in the model as constants, which belong to deterministic life prediction method. Deterministic life prediction method is suitable for fatigue life prediction and evaluation where the test data is sufficient. However, in practice, because of the restrictions on development cycles and there may be a shortage of funds, combined with technical difficulties, it has great difficulty to carry out a large number of trials. At the same time, due to different test specimens, along with test operations and data reading depend on the accuracy of test equipment and subjective judgment of test personnel, which increases the uncertainty of the fatigue life. S-N curve is the basic parameter of the material or structure life prediction and it is gained mainly through a large number of fatigue tests and fitting analyses. Due to the influence of uncertainty factors, which results in dispersion of fatigue life under constant load in different degrees, so as to the uncertainty of S-N curve. Therefore, in order to keep consistent with the actual situation of the life prediction, taking the uncertainty of S-N curve into account is needed. This article summarizes the uncertainty factors that affect fatigue life of welded joint, the polynomial chaos theory is introduced into the fatigue life prediction, a welded joint cumulative damage model considering the uncertainty S-N curve and probabilistic fatigue life prediction method is built combined with nonlinear cumulative damage model.

Reliability modeling and analysis of heavy-duty CNC machine tool spindle under hybrid uncertainty

Heavy-duty CNC machine tools have been used to process and manufacture the products and the key components with concerns the national economy and defense security, and the quantity of heavy-duty CNC machine tools measures the industrialization level and the comprehensive strength of a country. Compared with the general machine tools, heavy-duty CNC machine tools have a more complex system structure, smaller size sample, less experimental data, incomplete information, more complex failure mechanism and other characteristics. The heavy-duty CNC machine tools as well as its sub-systems are often influenced by hybrid uncertainty and the correlated failures of different components. Therefore, the existing reliability technologies cannot be applied directly, thus new reliability technologies for specific to heavy-duty CNC machine tools are needed. Aiming at the problems analyzed above, this paper focus on the reliability modeling and analysis of heavy-duty CNC machine tool spindle under hybrid uncertainty. Firstly, this paper analyzed various uncertainty factors influencing the reliability of the heavy-duty CNC machine tool spindle and the limitations of the existing uncertainty quantification methods, constructed a unified framework for hybrid uncertainty quantification based on the imprecise probability theory. Secondly, based on the uncertainty quantification framework and stress-strength interference theory, this paper proposed an imprecise structural reliability analysis and modeling method for mechanical components. Finally, the models proposed in this paper were verified through the imprecise structural reliability analysis of a certain type of milling spindle, the imprecise structural reliability models under different failure modes are proposed. And the results are compared with the results calculated by Monte Carlo method. It has shown that the proposed method has a higher computational efficiency.