| Heavy-duty CNC machine tools have been used to process and manufacture the products and the key components which concerns the national economy and defense security, and the quantity of heavy-duty CNC machine tools measures the industrialization level and the comprehensive economic strength of a country. The domestic heavy-duty CNC machine tools have obtained a lot of achievements after years of development, yet some issues are still existed. For domestic heavy-duty CNC machine tools, the technological innovation is insufficient, the basic experiment conditions is absent, and the advanced core technology isn’t breakthrough, thus the domestic heavyduty CNC machine tools have frequent early failures, bad quality stability, high maintenance costs during their usages. These issues have raised lots of difficulties and challenges to the machine tool users, and directly, also lead to the poor reliability, low product additive value, and a weak international competitiveness of domestic heavy-duty CNC machine tools. However, the existing reliability technology has been developed for the medium and small-sized CNC machine tools, not for the heavy-duty CNC machine tools, which show a large difference with the medium and small-sized CNC machine tools in their structures, working environments and machining task. The existing reliability technologies can’t be applied directly, thus new reliability technologies for specific to heavy-duty CNC machine tools are needed.Reliability analysis and modeling is one of the key reliability technologies for the heavy-duty CNC machine tools. Through the characteristics analysis of reliability data and impact factor analysis of reliability, reliability analysis and modeling is to study how to construct reliability model in accordance with the structure function characteristics of heavy-duty CNC machine tools. Compared with the general machine tools, heavy-duty CNC machine tools have a more complex system structure, smaller size samples, less experimental data, incomplete information, more complex failure mechanism and other characteristics. Aiming at the problems analyzed above, the major research contributions and innovative outcomes are summarized as follows.(1) Take a heavy-duty CNC machine tool spindle as the research object, 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 an unified framework for hybrid uncertainty quantification(UQ) based on the imprecise probability theory. Based on the UQ framework and stressstrength interference theory, this paper proposed an imprecise structural reliability analysis and modeling method for mechanical components. The models proposed in this paper are verified through the imprecise structural reliability analysis of a certain type of milling spindle.(2) Based on the UQ framework, this paper proposed an improved imprecise structural reliability model by considering the correlation of multiple failure modes. Failure correlation is the common characteristic of the heavy-duty CNC machine tool spindle, the existing researches on failure correlation are based on a large number of statistical failure data. The existing researches can’t be applied under the situation of insufficient data and it is not in consonance with the characteristic of heavy-duty CNC machine tools. Thus, this paper introduced a copula function into the structural reliability model, proposed an improved imprecise structural reliability model to consider the failure correlation, and then applied the improved model to the reliability analysis and modeling of the milling spindle to verify its effectiveness.(3) The heavy-duty CNC machine tool as well as its sub-systems are often influenced by hybrid uncertainties and the correlated failures of different components. According to this, this paper proposed an imprecise structural analysis and modeling method for mechanical system considering hybrid uncertainties and failure correlations. Most mechanical system reliability model can be regard as the combination of typical system reliability model, thus this paper proposed an imprecise structural reliability model for the typical system. Moreover, considering the importance of failure tree analysis on system reliability analysis and modeling, this paper proposed an imprecise structural reliability analysis and modeling method under failure tree analysis. Heavy-duty CNC machine tool spindle system includes many components, correlation analysis of these components often leads to a huge workload. Thus, this paper adopted DEMATEL method to analyze the importance and the failure correlation degree of different components, then the imprecise structural reliability analysis and modeling of a milling spindle is carried out.(4) During the life cycle of heavy-duty CNC machine tools, the reliability data is constantly updating and the reliability parameters are constantly changing. After an intensive study on the changing rule of reliability, the paper constructed an imprecise reliability growth model and an imprecise usage reliability assessment model. During the design and manufacture stages, heavy-duty CNC machine tool experienced the repeatable process of ‘design-test-improvement-edesign-retest’ and ‘manufacture-test-improvement-remanufacture-retest’, its reliability is ever-increasing, the reliability data of the former growth stage can be treated as the prior information of the later growth stage. Considering the prior distribution can’t be precisely determined under the condition of lack of data, this paper adopted imprecise Dirichlet prior distribution family to represent the prior information and constructed the imprecise reliability growth model. The usage reliability has a relationship with the inherent reliability, thus this paper took the information of inherent reliability as the prior information and realized the reliability assessment of usage reliability. |
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