Study On The Stree Concentration Factor Rule Of The Large Opening Nozzle With The Angle Less Than 45°

Small angle and large opening of axial oblique nozzle structure is widely used in the field of engineering,its application environment and structure form is more and more complex.The structure and stress distribution of the open hole inclined connecting pipe and cylindrical shell are complicated,which cause the difficulty in the research of stress state,and there are a series of technical problems in the practical production and application.At present,there are few studies about the law of stress concentration factor of structure with small angle and large opening,and the relevant provisions of the existing pressure vessel and pipeline structure design code are not clear enough.Therefore,it is necessary to find the regularity of the stress concentration factor of the open hole inclined connecting structure with the small angle and large opening.This paper systematically have studied the axial oblique structure,which the angle is less than 45° and the opening rate Dd is greater than 0.5,based on the electrical measuring method test,the credibility of finite element analysis was inclined.In order to get detailed study of the elastic stress analysis,the three dimensional finite element method have been used in this paper.We have obtained the stress concentration factor rules which were affected by parameters.The main work summarized as follows:1.The structure model was designed,the angle is 20° and the opening rate Dd is 0.615 and 0.802;the joint form is protruding nozzle.The model provided a reliable basis for the test study.2.On the basis of the electrical measuring method test,we have obtained 78 strain values over the eight paths and got the stress trend.3.Using three dimensional elastic finite element analysis to get the model's stress state,which the model had the same structure parameters with test model.The FEA results were compared to the results of test study,so as to verify the accuracy of the finite element calculation model and meshing scheme.4.The parametric model was established by ANSYS.These angles were 45°,40°,25°,35°,30°,20°;these opening rates were 0.35,0.517,0.674,0.84,and these nozzles allowance ?=DtdT were 0.4,0.646,0.8,1.0,1.2.The maximum stress and the stress concentration factor were obtained.5.Based on the finite element calculation results of structure with the angle below 45°,the related curves between SCFs and angles,the opening rates,the nozzles strength allowance have been obtained,also the stress concentration trends and the three-dimensional trend chart have been obtained.All the above things provided an important basis for the further research.The trend curves and 3D graph could have a very good reference value and a certain foundation for the following analysis and research.