Tolerance Analysis, In Service Pressure Vessel

This paper is one part of the project the fracture and fatigue life of pressure vessels? which is supported by science foundation of Department of Labor and Social Security of GanSu Province. Based on investigation, the following results are obtained: (1) Firstly, this paper reviewed briefly the development of safety assessment for pressure vessels. That include: 0 the development of FAD technology; ?the application of probabilistic method; he application of fuzzy method(esp. artificial neural network); Othe new advances on engineering assessment methods for fatigue. In the last, the developing direction in the future is prospected in the paper. (2)The fatigue of Pressure Vessel is a popular problem in engineering. The method of estimate fatigue life is very shorter than examination because of the dispersion of examination data. A formula is presented in this paper that is suitable to estimate fatigue crack growth Rate of the pressure vessels. The formula which separate the elastic and plastic component can be used in Paris zone and quickly growth zone. in this paper, the reasonableness is interpreted and the estimation method that could be used easily is presented. The application of this formula can improve the precision of calculate. (3) It has been widely used that the Paris law can discripted the relation between the fatigue crack growth rate and the stress intensity factor. The parameter of Paris law can be achieved by experiment. In this paper, a manner based on the artificial neural network is presented, which can estimate the parameter of Paris law in order to reduce experiments, take advantage of data and save times. Through comparing the results of estimation with experiment data, we prove that it抯 practical to estimate the rate by neural network method. (4)the fatigue life of a pressure vessel is estimated by this formula, and it抯 LBB analysis is presented. (5)Mixed mode cracks is in existence universally. Because of its complexity of combined stresses just as strength theory , a lot of mixed mode fracture criteria are presented based on some hypothesis. In this paper a mixed mode fracture criteria was established which based on the Yu's unified strength theory from the commonness of both theory.