Study On Stress Classification Of The Nozzle-Cylinder Intersection

Stress analysis of the nozzle-cylinder intersection is a problem important in engineering butdifficult in mathematics, most stress analysis is completed by finite element method(FEM) atpresent. According to previous research, applying the common stress criteria of current pressurevessel design code to the FEM result from stress-along-a-line method is demonstrated tooconservative, additionally, introducing the stress-along-a-line method to 3D finite element resultdirectly is also unreasonable. Therefore, how to make stress classification and evaluationrationally is a key problem of design by 3D FEM.The primary research work of this paper includes two parts:1. Modify stress criteria of stress-along-a-line method. Firstly, caculate the allowable limitinner pressure of the nozzle-cylinder intersection with different dimension by nonliner FEM.Secondly, apply the allowable limit inner pressure to model and execute elastic analysis. Andfinally, linearize the stresses at the danger location and get the nominal stress intensity. So thelimit of nominal stress intensity is the stress criteria. The study concluded that the primary localmembrane stress limit is 2.0 and the primary membrane plus bening limit is 2.1.2. Research on stress linearization on surface. Firstly, define the principle for location andorientation of stress classification surface, in which the area with 0.2% plastic strain intensity isdesignated as the extension of the stress classification surface, and according to the principle,five stress classification locations is selected. Secondly the empirical equation for the extensionlength is obtained by parametric study. Thirdly, apply the allowable limit inner pressure to modeland make elastic analysis. Finally, by introducing a method of linearizing stresses on curvedsurface (SOCS), execute stresses linearizing and get the nominal stress intensity. The limit of nominal stress intensity is the stress criteria of SOCS. Study shows that the limit varies withlocation, the range of primary local membrane stress limit is 1.5-1.9 and the range of primarymembrane plus bening limit is also 1.5-1.9.