Fuzzy Reliability Analysis For A Flanged Connection System Of Rocket Motors

The structural fuzzy reliability and sealing fuzzy reliability of a flanged connection system for rocket motors have received much attention in the last decades. Involving interaction of gasket, bolts and flange rings, the load-deformation and the structural fuzzy reliability of each component are analyzed in the case of ideality, external loads and creep-relaxation respectively. And then, the sealing fuzzy reliability of the flanged connection system is researched.The function of each part of genetic algorithm is analyzed in application to nonlinear unconstrained and constrained optimization. The optimization algorithm presented has both advantages of genetic algorithm and Newton iteration, globe optimal solution can be obtained with high accuracy in large range. An algorithm of solving nonlinear coupled equations is given which transforms the solving problem to unconstrained optimization problem and the coupled equations are solved by a genetic algorithm and Newton iteration.The research for theory and calculation method of structural fuzzy reliability is made. If either of strength and stress is stochastic variable and another is fuzzy variable, the .fuzzy variable can be transformed to section number on the assumption that the probability of fuzzy variable taking some points in that section is proportional to its value of membership function respectively, then the probability of structural fuzzy event is transformed to general probability with stochastic strength and stress variables and can be solved by general probability theory.Structure strength of flanged connection for rocket motors must be guaranteed in bolt-up and operating conditions. Firstly, the load-deformation relationship of the flanged connection system for rocket motors is analyzed by elastic theory, in which the flanged system is regarded as integer, in the same time, the effects of interior pressure and rotation of flange ring on load-deformation of flanged connection system are considered. Compared with traditional methods that neglect the rotation of flange, the present approach is closer to the actual situation. Secondly, the fuzzy limited state equations of the bolts and flange rings are determined according to a limited load method and their fuzzy reliabilities are calculated. The calculation result demonstrates the validity of the method presented.The fuzzy sealing reliability of the flanged connection system for rocket motors is investigated under the ideal case that creep-relaxation of each part of the flanged connection system is not concerned. Then a new method is proposed to calculate the flanged connection system for rocket motors under the bolt-up and operating conditions. Finally the sealing reliability is analyzed while the effect of creep-relaxation of each component of flanged connection system for rocket motors is considered.A new calculation method of load-deformation of the flanged connection system for rocket motors is presented when the flanged connection system is subjected to pressure and external bending loads. The structural fuzzy reliability and sealing reliability of the flanged connection system are researched in that case. The calculation result tends to be closer to the experimental result than traditional engineering calculation methods.