Reliability-Based Sensitivity Design And Application Of Mechanical And Structural Parametric Correlation And Serial And Parallel Systems

There are uncertain factors in the mechanical structures extensively. Therefore, it'll be much more accordant to consider uncertain factors in the mechanical structure design. The safety and reliability of the mechanical structures is one of the major objectives of the mechanical structures design. The reliability analysis of the mechanical structures can help the designer to establish the acceptable tolerances on the mechanical structures and to govern the fluctuations of the system parameters for safe operations. In the end, the reasonable mechanical structures could be designed with enough reliability and little cost.In the reliability-based design of the mechanical structures, the reliability theory which is based on mathematic theory such as the probabilistic theory, mathematical statistics and statistic process etc. usually consider geometric parameters, material properties and loads etc. as random parameters. Because the influence characters and degree of different design parameters to reliability of the mechanical structures are different, it is necessary to do reliability-based sensitivity analysis to make sure the influence of design parameters to reliability of the mechanical structures. Then reliability design of the mechanical structures can be made. The reliability-based design, the reliability-based optimization design and robust design are very advanced design ideas. They have extensive application prospects on account of significance in improving product quality and making performance stability.The reliability-based design and the reliability-based optimization design utilize reliability theory to deal with uncertainties, and robust design attempts to make the variations of mechanical structures are insensitive to variations of design variables. The aforementioned methods are all very effective to improve design level of the mechanical structures. These methods have usually been used separately in different design stages for different purposes. Therefore, it is essential to combine the reliability-based optimization theory, the reliability sensitivity analysis technique and the robust design method and to develop a reliability-based robust design approach.In this dissertation, on the basis of summarizing the reliability-based design theory, the reliability-based sensitivity design method and the idea of robust design in the world, the reliability-based sensitivity of correlation coefficients among the random variants obeying Gaussian and arbitrary distributions was studied; the positive and negative character and its determinative condition of the reliability-based sensitivity of the covariance and the correlation coefficients were analyzed; the reliability-based sensitivity design methods of serial and parallel structural system was proposed; then the reliability-based mechanical and structural robust design based on the reliability-based sensitivity was realized.There are 6 Chapters in all in the dissertation, and the main research contents of the dissertation are as follows:Chapter 1: Introduction. We explicated the background and meaning of the dissertation; introduced the rise, the development and the actuality of reliability-based theory; described briefly the meaning and research advances in reliability-based design method; and set forth the initiation and development of the robust design method and the research advances in reliability-based robust design. And the main content of my work was described briefly.Chapter 2: Mathematics background and basic theory of reliability. In Chapter 2, the mathematic theories and methods used by this dissertation are introduced firstly. Then the basic theories and methods of reliability analysis were described briefly. At last, the reliability-based perturbation methods were explicated in detail.Chapter 3: Reliability-based optimization design with arbitrary distribution parameters. In Chapter 3, the numerical method of reliability-based sensitivity design was studied from the level of the mean, the variance (covariance) and the correlation coefficients of basic random variants obeying Gaussian and arbitrary distributions. The influences of variance (covariance) and correlation coefficients of basic random variants on reliability of mechanical structures are discussed. The positive and negative characters and its determinative conditions of the reliability-based sensitivity of variance (covariance) and correlation coefficients were analyzed. The reliability-based sensitivity design theory is made much more perfect.Chapter 4: Reliability sensitivity design. In Chapter 4, on the basis of the reliability theory of serial and parallel system and sensitivity analysis method, reliability-based sensitivity of serial and parallel mechanical and structural system with multiple failure models was discussed. The calculation approach of reliability sensitivity is presented. The change laws of the reliability sensitivity are given. The influences of design parametric changes on reliability of mechanical structures are studied and theoretic foundation are provided for reliability-based design of mechanical structures.Chapter 5: Reliability-based robust design. In Chapter 5, on the basis of the reliability-based optimization design theory, the reliability sensitivity analysis technique and the robust design method, the reliability-based robust design of mechanical structures is discussed based on the reliability-based optimization model. A mathematical model of reliability-based robust design was established according to such an idea that reliability-based robust design problem was equalized to multi-objective optimization problem satisfying the reliability constrictions by including the reliability-based sensitivity functions to the objective functions of reliability-based optimization design model. The reliability-based robust design method was applied to the design of serial system with multiple failure models.Chapter 6: Conclusions and prospects. We draw the main conclusions of this dissertation and discuss the developments prospects of mechanical and structural reliability theory research and applications.