COMSOL Finite Element Simulation Of Stress-assisted Diffusion Problem

With the development of science and technology,more and more engineering problems can not be solved by a single physical field,and often involve the study of coupling of multiple physical fields.Therefore,the analysis and calculation of coupling of multiple physical fields are particularly important.Diffusion is a common physical process in life and engineering.It is found in research that external mechanical force will affect the diffusion rate,which is called stress-assisted diffusion.It can be seen that stress-assisted diffusion is a coupling phenomenon between diffusion field and field.This paper aims to explore the calculation method of a kind of stress-assisted diffusion problem and use this method to quantitatively analyze the diffusion problem in engineering practice.It is considered that in the process of material diffusion: on the one hand,the diffusion rate will be affected by external load;On the other hand,diffusion matrix is not homogeneous material,and its constitutive equation is related to diffusion process.In view of the influence of load on diffusion,Aifantis stress-assisted diffusion equation modeling is adopted in Comsol,and the permeability experiment of coating in clay materials is used to verify it.By comparing the simulated value with the original experimental value and the theoretical value of the equation,the applicability of the equation is verified.Aiming at the influence of diffusion constitutive equation,the carbonation of concrete and the corrosion of reinforcement in concrete are studied in this paper.In the process of carbonization,the full coupling of force field and diffusion field is realized by establishing the function relationship between young's modulus of concrete and carbonization process.The concrete carbonation coupling model is compared with the experimental data,and good consistency is obtained.As for the corrosion of rebar,the influence of corrosion strain produced by the expansion of rebar on the constitutive equation is also considered.By setting up a new constitutive equation of steel reinforcement corrosion in Comsol,the corrosion rate of steel reinforcement under six kinds of chloride ion concentrations was simulated,and compared with the corresponding experimental regression equation,the theoretical results were obtained.In addition,this paper also makes a comparative analysis of fully coupled and single-coupled models in the case of steel reinforcement corrosion.It is found that,under the single-coupled model,the diffusion rate is faster and the radial principal stress of the outermost layer is greater.In practical engineering,the single-coupled model will cause greater damage to peripheral concrete than the fully coupled model.