Strain Hardening Load-carrying Capability Research Of Austenitic Stainless Steel Pressure Vessel

It has become the significant topic for pressure vessels development that how toactualize the light design considering safety and economy. With the elastic-plastic analysisdesign method introducing into European Union and United States standards of pressurevessel, the strain hardening technology based on the elastic-plastic analysis design hasbecome the important way to achieve the trend of light-weight for austenitic stainless steelpressure vessels, and the application prospect is great significance. With the characteristic ofgood plasticity and low ratio of yield strength and tensile strength, austenitic stainless materialis extremely suitable for strain hardening design, and it can enhance the yield strength andreduce the wall thickness, from this to reduce the weight of pressure vessel and achieve theaim of energy conservation and emission reduction.According to the elastic-plastic analysis design method, this dissertation mainly researchin these questions of the engineering use for the austenitic stainless steel strain hardeningpressure vessel, the main research contents and conclusions are as follows:（1）The tensile testing at room temperature shows that austenitic stainless steel S30408made in China can meet the standard requirements, and it has fine plasticity and toughness.The four types of material curve models have different merit and demerit. They can apply indifferent situation. The result of S30408gap round bar tensile testing shows: the notch radiussize has an obvious effect on yield strength, tensile strength, elongation and fracture strain ofthe specimen.（2）Using the finite element simulation calculation method to have a quantitativeanalysis of the cylinder length and wall thickness on the influence of plastic buckling pressureof cylinder vessel and spherical vessel, compare and calculate the plastic buckling pressure ofcylinder and spherical vessels under four different constitutive model. Quantitative calculatethe safety margin of the pressure vessel at strengthen pressure and design pressure underdifferent pre-deformation. Results showed that the pre-deformation of the strain strengtheningcylinder vessel and spherical vessel should be controlled within3%.（3）Analyzed the relationship between triaxial stress degree coefficient and fracturestrain of S30408material by the gap round bar tensile experiment combined with the finite element analysis calculation results. The result showed that: specimen ductile fracture failurewhen a tensile test specimen notch radius less than or equal to2.0mm; specimen plasticinstability failure when a tensile test specimen notch radius greater than2.0mm. It is not safeto limit the strain of austenitic stainless steel material S30408according to ASME Ⅷ-22007.（4）Built the nonlinear finite element complex structure pressure vessel model withopen hole tube, and quantitative analyzed the load and strain relations at the principal part andtube root part of the cylinder and spherical vessels at different load. The result shows that theequivalent strain at the tube root part is nearly2times of the equivalent strain at the principalpart. Quantitative calculate the safety margin of the pressure vessel at strengthen pressure anddesign pressure under different pre-deformation, the results shows that: to meet the safetyrequirements of the engineering use, the pre-deformation should be controlled in less than3%.