The Plastic Limit Load And Stress Concentration Factor Study Of Axial Oblique Nozzle Under Internal Pressure

Based on the ANSYS finite element analysis method, the cylindrical shell structure with axial oblique nozzles under the action of internal pressure are studied, gain the yield structure, the changing rule of plastic limit load and stress concentration factor. many scholars and experts in this field at home and abroad undertake a large number of experiments and simulation research work, but the studies of small-angle and large aperture ratio (d/D>0.5) are few. Therefore, the analysis and research of limit load of axial oblique nozzle will have higher engineering significance.With the aid of the finite element method, to study of ultimate load of the cylindrical shell structure with axial oblique nozzle of different angle under the action of internal pressure.The main research content is as follows:1. This paper adopts two methods to carry on the limit analysis to opening rate d/D is0.6, the angle are respectively15°,35°,55°,75°four kinds of situation. To study the internal pressure under the action of stress distribution, obtaining maximum stress value, the stress concentration factor is obtained.2. Under the action of internal pressure, get strain values of several key points near cylinder nozzle-vessel junction area and draw out stress strain curves of the key points, according to different criteria, gain the plastic limit load respectively, and compare the analysis.3. Use the grey prediction model GM (1,1) and regression prediction software to forecast the ultimate load finite element simulation results, and compare with simulation results.Through the research above, arrive at the following conclusions:(1) the reduce of the ultimate bearing capacity of axial oblique nozzle, due to the cause of severe stress concentration which is mainly caused by the hole, and with the Angle (?) decreases, and ultimate load decreases,the carrying capacity. Double tangent guidelines,twice elastic slope criterion and zero curvature criterion can be used in the ultimate load calculation of axial oblique nozzle,and the limit load which are gained by different criteria follow relationship: PL>Pt>Pφ(2)The smaller the Angle (?), the greater the stress concentration factor K of the side of acute Angle, namely the more severe the stress concentration. thus, in situations where conditions permit, the axial oblique nozzle of more than Angle45°should be used in actual product.(3) The calculation formula of the stress concentration of axial oblique nozzle under factor internal pressure in ASME boiler and pressure vessel code the third article, stress concentration factor of the Angle (?)>30°to predict more accurately, the stress concentration factor of the Angle theta30°or less prediction error is bigger. It shows that the formula is not applicable to small-angle oblique nozzle for the calculation of stress concentration factor.