The Fine Constitutive Model Of Stainless Steel At Elevated Temperature And Application In The Component Design

With the development of construction industrialization and the constant adjustment and upgrading of industrial structure in China,more and more attention has been paid to steel structure because of its superior performance.Among them,the stainless steel structure because of its good anti-corrosion performance and excellent performance,designers are very popular.In recent years,due to the diversification of the energy use mode and the negligence of fire management and public awareness,the building fires are frequent,causing serious casualties and property losses.Compared with traditional masonry structure and concrete structure,steel structure is more sensitive to fire,and its mechanical performance and behavior response under fire are more important.The study of mechanical properties of materials under high temperature as a basic research has laid an important foundation for the research on fire resistance of components and structures.The study of mechanical properties of stainless steel materials at home and abroad has been more perfect,but the research on mechanical properties of stainless steel materials at high temperature is still very scarce.Based on the above background,the constitutive model of stainless steel under high temperature and its application in components are studied in this paper.Based on the domestic austenitic S30408 stainless steel,the mechanical properties of the stainless steel materials were tested by tensile test at normal temperature,steady test at high temperature and transient test method(including 8 normal temperature specimens,28 high temperature steady test specimens and 36 high temperature transient test specimens).The mechanical properties of stainless steel materials under different conditions were investigated.The mechanical properties of the modulus of elasticity,yield strength and ultimate strength of stainless steel at normal temperature and high temperature were obtained,and the corresponding stress-strain curves were given,and the large strain range of stainless steel at high temperature was further studied.The development trend of the stress strain curve in the internal stress curve.On this basis,the steady-state test results and the transient test results of the mechanical properties of stainless steel at high temperature are compared.The results show that,when the temperature is not more than 600,the stress-strain curves of the two test results are very close and can be equivalent to each other.When the temperature is higher than 600,the errors are larger and not equivalent.On the basis of the experimental research,the research results of the mechanical properties of high temperature stainless steel materials at home and abroad are collected,and the results of the mechanical properties of materials at high temperature and the results of the existing models are compared and analyzed in this paper.It is easy to find that the existing stainless steel material model at high temperature can not completely and accurately reflect the mechanical properties of materials at high temperature.Therefore,it is necessary to construct a refined constitutive model for stainless steel at elevated temperature.In this paper,two constitutive models of stainless steel under high temperature are established by theoretical deduction and numerical simulation analysis,namely theoretical model and simplified model.First,a theoretical model of stainless steel material constitutive model with 5 basic mechanical properties at high temperature is established by theoretical derivation,and the accuracy of the theoretical model is verified based on the experimental results of this paper.Then,the reduction coefficient of 5 mechanical parameters in the theoretical model is studied and analyzed at high temperature.The expression of the reduction coefficient of various mechanical properties is given,and the reliability analysis of 5 mechanical properties is carried out by using the statistical software SPSS.The analysis results show that the theoretical model is applicable to stainless steel plate and corner area.Finally,based on the Ramberg-Osgood model,after repeated trial calculation and observation,the stress strain curve of stainless steel materials at high temperature is re segmented,a simplified model containing temperature parameters is put forward,and the coefficient in the model is fitted with the software of Matlab.The results show that when the stress is greater than 1,the stress strain curve of the material is close to the straight line when the stress is greater than that of the stainless steel at high temperature.When the stress is greater than 0.8,the stress strain curve of the material is close to the straight line.The theoretical model and simplified model of the mechanical properties of stainless steel materials at high temperature are applied to the numerical simulation of the fire resistance of a rectangular stainless steel rectangular beam,a rectangular stainless steel column with a confined eccentric compression and a H shaped stainless steel column with a confined axial compression.The finite element analysis software ABAQUS is used to simulate the fire resistance of the above three components.The theoretical model of the mechanical properties of stainless steel materials at high temperature and the simplified model are used to calculate the fire resistance index(critical temperature,bearing capacity and so on)of the three components at high temperature,and the numerical simulation results are compared with the experimental results.The results of comparative analysis show that when the strain value is low at low temperature,the fire resistance index calculated by the theoretical model and the simplified model is not quite different from the results calculated by the constitutive model based on the results of the material mechanical performance test.When the strain value is high at high temperature,when the strain value is large,the fire resistance index calculated by the theoretical model and the simplified model is deviated from the results based on the constitutive model of the material mechanical performance test results.The theoretical model and simplified model of stainless steel under high temperature are convenient and reliable in the numerical simulation of fire resistance of components.