Study On The Numerical Characterization Of The Stress-Strain Curves Of Pressure Vessel Materials

The numerical characterization of stress-strain curves means using function method to fit the stress-strain relationship of materials. Tests show that most of the pressure vessel materials have significant strain hardening characteristics in the process of drawing. Therefore, elastic and plastic analysis method should be used to make full use of the material strain hardening property when designing a pressure vessel, in order to increase the pressure bearing capacity of the pressure vessel reasonably, and reduce the thickness of the vessel wall. However, because there is no sufficient data support regarding the strain hardening in our country, the elastic plastic analysis method is seldom used. In addition, the development of pressure vessel design is restricted for the lack of basic data. In this thesis, based on the tensile tests of pressure vessel materials, a method of numerical simulation of stress-strain relationship of materials is proposed and the fitting of the stress-strain curves of some materials is completed. The main work is as follows:(1)Tensile tests for 14 kinds of pressure vessel materials at normal temperature and high temperature referring to the relevant norms of the national standards 228.1-2010 GB/T and 4338-2006 GB/T were finished. Two tensile tests for each 50 degrees Celsius in the allowable temperature range were performed and the test data are analyzed.(2) The MPC model in ASME code was analyzed. Effects of different parameters on the fitting results were compared and the error between the MPC model and the test results at different temperatures was examined with the causes of error being analyzed. Thus, the applicability of MPC model to the material properties in China was discussed.(3) A numerical method for material properties was established considering the specific conditions of our country. The tensile test results of different materials were compared and the materials were classified based on the behaviors at the yield stage. As a result, different fitting models were proposed for different types of materials.(4) All materials were described by numerical methods according to the tensile test results. The fitting results were compared with the MPC model and the error is calculated. The numerical characterization method of the stress-strain curve of pressure vessel materials is summarized.