Plastic Load And Safety Margin Research Of Austenitic Stainless Steel Pressure Vessel

The resources is becoming less and less now, how to actualize the light design andmanufacture of cryogenic vessels is the important topic in front of everyone. Design byanalysis and strain strengthening design are important ways to realize the light design. Withthe development of plastic mechanics theory and nonlinear finite element technology,elastic-plastic analyses of pressure vessel have made great development. The design methodof elastic-plastic analysis was introduced into European Union and the United Statesstandards of the pressure vessel. Strains strengthen technique of pressure vessel for austeniticstainless steel has been used many years in foreign, but just begin to use the technique indomestic. Elastic-plastic analysis design and strain strengthening design of pressure vesselconsider t he the strain strengthening affect of materials and the structure deformationcharacteristics of component. It is an advanced pressure vessel design technology, theapplication prospect are great significance. But the realization of design by elastic-plastic forpressure vessel is by the way of the nonlinear finite element analysis, it need to spend muchtime and not easy to understand. If we can find the analytical formula of the load-strainrelations、plastic collapse pressure and safety margins, it can greatly promote the applicationof design by elastic-plastic analysis for pressure vessel and easy to be understood.In this paper, according to the problems above, the main research contents and researchconclusions are as follows:（1）To compare and analyze the different materials curve model. The results show thatSwift curve model has bigger error to the measured curve model, and the ASME curve modelhas smaller errors, especially when the strain is small. It is accurate to use ASME curvemodel for the finite element simulation. Automatic operation procedure can acceleratecalculation of the ASME curve model.（2）Validate the analytical formula of load-strain relationship and plastic collapsepressure deduced by predecessors with the finite element analysis. The results show that theresults calculated by the analytical formula of load-strain relationship and finite elementanalytical is very consistent, calculating the load and strain with the analytical formula ofload-strain relationship is feasible. The pressure calculated by the analytical formula of plastic collapse pressure is bigger than the pressure calculated by the finite elementsimulation. Calculating the plastic collapse pressure with the analytical formula, the result ispoor.(3) Validate the analytical formula of safety margin deduced in this paper with the finiteelement analysis. The results show that calculating the safety margin of the pressure vesselsof austenitic stainless steel with the analytical formula derivate by this paper is feasible.(4) Having the nonlinear finite element analysis for strain hardening cylinder andspherical shell of austenitic stainless steel with the two true ASME stress-strain curvesestablished independently by standard material values and measured material values. Theresults show that when the theoretical stain of pressure vessel is10%, the actual strain is only3%-5%; when the theoretical stain of pressure vessel is5%, the actual strain is only1%;when designing the strain hardening pressure vessel according to standard, the safety marginis satisfying the requirement; but in the actual strengthening process of pressure vessel,keeping the strain of pressure vessel at3%is much better, which can make the actual vesselsafety close or bigger than2.4and is benefit to the control of the pressure in the strainhardening process.