Haiqing Li

A nonlinear fatigue damage accumulation model considering strength degradation and its applications to fatigue reliability analysis

Fatigue is a damage accumulation process in which the material property deteriorates and degenerates continuously under cyclic loading. The analysis of damage accumulation plays a key role in preventing the occurrence of fatigue failures, and the damage evolution mechanism is one of the important focuses of fatigue behavior. In this paper, a residual strength degradation model according to the stress–strength interference (SSI) model is introduced firstly; then a modified nonlinear fatigue damage accumulation model based on the Manson–Halford theory is proposed. Combining the proposed nonlinear damage accumulation model with the residual strength degradation model, a new method is developed for fatigue life prediction under constant and variable amplitude loading, which considers not only the effects of load interactions, but also the phenomenon of strength degradation of materials induced by loading history, and it can be used to predict the reliability and fatigue life of mechanical components. Moreover, the material parameter for the residual strength degradation can be obtained directly from S–N curve without running extra experiments. Finally, experimental data are used to compare with the predicted value in order to demonstrate the proposed residual strength degradation model. In addition, two sets of experimental data are also used to verify the proposed nonlinear fatigue damage accumulation model which is applied to predict fatigue life under two-stress level loading and reliability prediction under multi-stress level loading. The results show that the proposed method has a good agreement between the experimental data and predicted values.

Reliability analysis of CNC hydraulic system based on fuzzy fault tree

Taking account of the fuzziness associated with failure probability of hydraulic systems, a fuzzy fault tree is proposed in the paper by integrating the fuzzy set theory into the conventional fault tree analysis method. The triangular fuzzy numbers are utilized to qualify the fuzzy uncertainty of basic events in the construction of fuzzy fault tree. Moreover, the fuzzy importance measure of each basic event can also be computed. The proposed method is applied to a CNC hydraulic system to demonstrate its effectiveness, and it is able to provide industry practitioners a theoretical basis to facilitate the system reliability assessment, fault diagnosis, as well as maintenance decision.

Software development for mechanical reliability analysis

The quantitative reliability analysis of mechanical components can be approximately divided into two situations: i the performance function is given, ii the performance function is unknown. The limit state equation of complex mechanical component is often implicit, and the performance function can hardly express the analytical expression. As a matter of fact, its especially effective calculating the reliability index of mechanical components by means of the simulation with ANSYS. The reliability index of mechanical components can be achieved by calling ANSYS and random model files repeatedly. To implement the mechanical reliability analysis conveniently and accurately, we developed a kind of software which is able to calculate the reliability index of complex mechanical component. And the programing language and application software including C#, SQL Server, Matlab and ANSYS are used in the process of software development.

Reliability allocation for wafer stage system of lithography based on AHP

To ensure the reliability of the wafer stage system of lithography, all factors affecting the wafer stage system reliability were analyzed. A new method based on experts grading method[1] and analytic hierarchy process(AHP)[2] is developed to allocate the reliability indices of wafer stage system. This approach considers not only the experience and knowledge of the expert, but also combines the Comparative Matrix of analytic hierarchy process to reduce the defect that stronger subjective factors of experts grading method. Finally, the wafer stage system of a certain lithography was taken as an example, and the reliability allocation of the system was obtained. The result indicate that the proposed method is feasible and effective.

A new fatigue damage accumulation model based on nonlinear continuum damage mechanics

This paper presents a new non-linear fatigue damage accumulation model based on continuum damage mechanics. The proposed model has been formulated to take into account the damage evolution of material under different loading levels and the effects of loading sequence on fatigue life. In additional, the model has also considered the mean stress in its damage evolution with fewer parameters. Experimental data of 30NiCrMoV12 under two-stress level loading in literature were used to verify the proposed model. Predicted fatigue lives using the proposed model show a good agreement with reported experimental data.

Grid analysis of lightning parameters based on GIS

With the rapid growth of electricity grid and the unusually changing of global climate in recent years, the comprehensive analysis of the lightning parameters becomes very important. Sichuan Province started to use Lightning Location System (LLS) in 2003, it has been running for 7 years. The database has accumulated a lot of valuable lightning detection data about lightning activity. Comparing with the traditional lightning parameters, lightning detection data is more comprehensive to reflect the characteristics of lightning activity. The grid method is used to count and analyze the lightning detection data. The Components Geographic Information System (Com-GIS) has been developed to achieve the visual statistical analysis of some representative lightning parameters, such as thunderstorm day, flash density, γ, intensity of flash amplitude, the number of lightning in the regions of Sichuan province. And grid distributions of each parameter has been obtained and analyzed. This work could support useful references to the study of lightning activity rules, reducing the damages and threats caused by lightning for the power system transmission lines, substation facilities, and other electrical facilities and equipment, and guiding the lightning preventive construction.

A bootstrap-based method for processing accelerated life test data

This paper proposes a bootstrap-based data processing method to facilitate the accelerated life test (ALT) of He-Ne laser. With assistance of the bootstrap method, the life distribution, reliability parameters, confidences and interval distributions associated with the accelerated model can be computed under normal working condition, hence improve the precision of the accelerated life test.

Fuzzy Dynamic Fault Tree Analysis of Hydraulic System of CNC Machining Center

Fault tree analysis (FTA), as an effective reliability assessment tool, is a widely used in analyzing the risk and reliability of large scale and complex engineering systems. Dynamic fault tree analysis (DFTA) extends the static fault tree by defining additional gates to model the complicated interactions, and in most case, Markov models can be used to solve dynamic gates. In many real systems, it is quite difficult to evaluate the probability of failure events preciously due to many uncertainty factors. To account for the uncertainty resulting from the lack of sufficient data or the subjective adjustments from experts, a fuzzy dynamic fault tree model is proposed to assess the system reliability when acquiring precious probability of failure event is impossible. With the aim of obtaining the membership function of the fuzzy probability of the top event, the extension principle is employed. The proposed method and algorithm are demonstrated by a case study of the hydraulic system of a specific CNC machining center.Copyright

Research on visualization technology and information management system for collaborative production development

A novel product data management mode, CVPDS (Collaborative Visualization Production Development System), which is based on the cooperative design and visualization technology, is proposed in this paper. It also analyzes and establishes the system frame, discusses the key technology of cooperative visualization development and the implementing management flat; studies the realization method of 3D virtual modeling based on network, the information visualization and so on, and then, proves the feasibility and the practicability of the CVPDS by the development and preliminary application of a prototype system, which gives a useful research on resource sharing and interactive technology under the advanced manufacturing mode.