A Study Of Limit Load For Cylindrical Shells With Reinforcement Pad Under Nozzle Moment

With the development of petrochemical, energy and nuclear industry, thecylindrical shell structures with nozzle and reinforcement have now been widely usedin pressure vessel and piping systems. Because of the variety of geometric parameters,fabrication methods and loads, it becomes very difficulty to calculate the local stressin the cylinder-nozzle intersection area. So an overall analysis about the cylindricalshell structures with nozzle and reinforcement is of great value not only for academicresearch but also for engineering applications. This paper was sponsored by PVRC. The limit load study was carried out throughexperiment on opening-reinforcement structure. The main contents in this paper are including: 1. To gain the load-strain and load-displacement curves through electrometric method on the six tested vessels with different d/D ratio and stand pad reinforcement on different load. 2. Besides the vessels used in the experiment, some other key models were studied by three-dimension nonlinear finite element method and a series of data and conclusions were got in the same aspects. 3. Characteristic of contact force and its effect on limit load were investigated between pad and cylinder. In addition, the error derived form mesh disperse were also provided. 4. To investigate the regularity of stress distribution of the cylinder-nozzle area by drawing the stress distribution curves and to study the effect of the pad reinforcement on stress distribution of the cylinder-nozzle area and the limit load of the structure. 5. A series of parametric models have been researched to gain the empirical formula. In the end, the empirical formula was applied to a practical pressure with pad-reinforcement nozzle under external load and then its load and design load were calculated. Some conclusions were obtained through the study above: III南京工业大学硕士学位论文 ABSTRACT 1. Danger area appeared at cylinder-nozzle area and edge of reinforcement pad, transverse section of cylinder-nozzle was minimum life section. 2. Stress distribution appeared symmetrical characteristic in transverse section of cylinder-nozzle. 3. The stress concentration is local obviously. The stress rapidly attenuates to the normal stress level with the increase of the distance off the opening. 4. Finite element results, including the contact element in the analysis, could predict better stress distributions in the cylinder-nozzle structure, compared to the results without contact element. 5. A reinforcement structure reduced effectively the stress concentration of cylinder-nozzle area, increased the limit load of the structure, and it should be recommended to practical application. 6. Both the limit load gotten through load-strain curves and through load-displacements are correct. So in order to simply the procedure of obtaining the limit load of the structure, the way through load- displacement curves is recommended. 7. The verifying result indicated that the empirical formulas for limit load had preferable reliability and application value.