Creep Buckling Of Long-term-service Furnace Tube Subjected To High Temperature Loading

As one of the most important components in high-temperature equipment,high-temperature furnace tubes have a variety of excellent properties and are widely used in chemical and engineering fields.The working environment of high temperature is extremely harsh for furnace tube,long time service can easily cause creep,corrosion and other damage,which will lead to a sharp drop in the strength and stability of high-temperature furnace tubes.The problem of components due to high-temperature is relatively complex and the impact factors are quite diverse.The research concerning the influence of high-temperature on components is still a major challenge in academia.At the same time,the research of creep stability of furnace tubes caused by high-temperature has significant engineering meaning.This paper aims to study the creep buckling of the furnace subjected to external pressure in a high temperature environment.In this paper the furnace tube is regarded as a finite-length cylindrical shell simply supported at both ends.According to creep aging theory and classical theory of thin shells,considering the effects of temperature field and pressure field,creep buckling of cylindrical shell subjected to external pressure under high-temperature is studied.The influence of different factors on the creep buckling performance of cylindrical shell is investigated.The main contents are as follows:Firstly,the nonlinear stress-strain constitutive relation for creep deformation of the furnace tube in high-temperature environment is established based on the deformation theory of plastic mechanics.Due to the influence of high-temperature environment,furnace tubes creep and the stress-strain relationship of the furnace tube is changed,which makes the constitutive relations different from elastic buckling in the room temperature environment.During the analysis,the creep buckling process of the furnace tube in the high-temperature field is considered as two stages: The first stage is the creep deformation of the furnace tube under high-temperature and external pressure where the material stiffness continues to decreases as the time increases;the second stage is the instantaneous bifurcation buckling of the tube.According to the theory of aging,and by analyzing the stress mechanism in the furnace tube subjected to external pressure,the creep constitutive equation of the furnace tube is established.Secondly,governing equations for creep buckling of furnace tubes by influence of initial curvature are established and solved.On the basis of the Karman-Donnell equation,the equations of the non-shallow cylindrical shell by the influence of the initial curvature on Curvature and bending are established,the creep constitutive equation of the furnace tube subjected to external pressure is derived.The differential equations in terms of displacements suitable for the creep bifurcation buckling of non-shallow cylindrical shell with finite length are derived.By examining the failure mechanism for the buckling of the cylindrical shell subjected to external pressure,the buckling displacement functions that satisfy the simply supported boundary conditions are introduced to solve the governing equation.And then,the analytical solutions are compared with the experimental results from the existence literatures to validate the model.Using the material properties given by the existing literature,the furnace tubes of two different materials,nickel and zirconium alloys,are theoretically analyzed,and the creep buckling loads of the furnace tubes are obtained.The theoretical solutions of the obtained buckling load are compared with the experimental results to verify the rationality of the theoretical analysis.Finally,numerical examples and finite element analysis are performed.The parameters for different temperatures are given and MATLAB programming is developed to calculate the specific example values.The influence of different factors on the ultimate buckling strength of the furnace tube,including the material parameters,length-to-diameter ratio,diameter-to-thickness ratio,time and temperature,are studied.Using ABAQUS software,finite element simulations are performed and the results are compared with the theoretical solutions.