Mechanical Fuzzy Reliability Design Theory And Application

With the development of the science and technology, the reliability of mechanical products is paid more and more attention in the wide world recently. The reliability is an important quality index in mechanical products, and its level is of vital importance to the competitive power of the products. The aluminum ingot machine is one of the key equipments in producing of the common remelting aluminum ingot, and its reliability affects directly on the productivity and competitive power for market of an enterprise. The theory of mechanical fuzzy reliability design is studied and applied in this thesis.Based on the basic principle of the fuzzy mathematics and theory of the general reliability design, the fundamental principle and method of the mechanical fuzzy reliability design are investigated and studied through integrating the two ideologies in the first part of this thesis. A rule of fuzzy reliability design based on "component's membership of the fuzzy safety state" is presented, furthermore, the method of fuzzy reliability design for machinery component is derived when stress and strength is respectively fuzzy random variable. Meanwhile, the mathematical operators of fuzzy logic gates in fault tree analysis are derived according to the operation rule of the linear fuzzy number. Finally, the theory scheme of mechanical fuzzy reliability design is set up basically.The second part of this thesis analyzes the reliability of the drive system of aluminum ingot machine by use of above theoretic results. Firstly, the qualitative analysis for the abnormal failure reason of conveyor chains is given, and that the main reason lead to failure is the lack of fastness of link joint is obtained. Furthermore, the reliability for joint fastness in roller chains for conveyors is optimized by using the general reliability design theory, and the optimum magnitude of interference of link joint is obtained. Finally, based on its running state, the fault tree of the drive system of aluminum ingot machine is established and analyzed fuzzily, and its reliability datum is obtained. Above results will be helpful to improve the aluminum ingot machine.