Transient pitting growth simulation platform under interaction of mechanics and electrochemistry

Abstract

The invention discloses a transient pitting growth model simulation platform based on interaction of mechanics and electrochemistry, and belongs to the technical field of corrosion. According to the corrosion simulation platform, electrochemical reaction, solution reaction and diffusion, solution potential drop and mechanical interaction local evolution rules at corrosion defects of a steel plate in a simulated marine environment are established through a COMSOL Multiphysics solid mechanics module and a secondary current distribution module; in a transient pitting growth process, finite elements are used for analyzing stress distribution, corrosion current distribution, corrosion potential distribution and a corrosion defect evolution process at a corrosion defect within 20 years in real time, and then a corrosion simulation process is realized through an App Device. By means of the method, the corrosion evolution process in the next 20 years can be rapidly obtained by inputting parameters of the steel plate size, the corrosion defect size, the seawater conductivity, the temperature and the external load under the actual working condition, a complex bottom layer model and a corrosion mechanism do not need to be known, and the working efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the field of corrosion technology, and in particular relates to the development of a corrosion simulation platform. Background Art

[0002] At present, marine corrosion can cause damage to infrastructure and industrial equipment, economic losses, and problems to the environment and human life. When tackling marine corrosion issues, scholars usually use COMSOL corrosion software to establish corrosion models and restore the corrosion process, avoiding the time-consuming experimental method, the difficulty in real-time monitoring of the corrosion process, and the difficulty in understanding the corrosion mechanism. However, when it comes to multi-physical field coupling, corrosion simulation will have modeling difficulties, large amount of calculations, and require the operator to be proficient in the knowledge of the corrosion field and the use of various COMSOL modules. Summary of the invention

[0003] In order to solve the problem that it is difficult for people in non-corrosion simulation fields to simulate and predict the transient pitting growth model under the interaction of mechanics and electrochemistry, the method of the present invention is combined with the COMSOL model developer to input the parameters of steel plate size, corrosion defect size, seawater conductivity, temperature and external load under actual working conditions to quickly obtain the corrosion evolution process in the next 20 years, without the need to understand the complex underlying models and corrosion mechanisms, thereby improving work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 This is the input bar of the corrosion simulation platform

[0005] Figure 2 This is the output bar chart of the corrosion simulation platform

[0006] Figure 3 Corrosion simulation platform function 1: modeling geometry

[0007] Figure 4 The second function of the corrosion simulation platform: grid division

[0008] Figure 5 Function 3 of the corrosion simulation platform: Simulate the evolution of steel plate corrosion defects over 20 years

[0009] Figure 6 Function 4 of the corrosion simulation platform: Simulate the Von Mises stress distribution diagram of the steel plate corrosion defect within 20 years

[0010] Figure 7 Function 5 of the corrosion simulation platform: Simulate the corrosion potential distribution at the corrosion defects of steel plates within 20 years

[0011] Figure 8 Function 6 of the corrosion simulation platform: Simulate the distribution of anode current density at the corrosion defect of steel plate within 20 years

[0012] Fig. 9 Function 6 of the corrosion simulation platform: Simulate the cathode current density distribution at the corrosion defect of the steel plate within 20 years DETAILED DESCRIPTION

[0013] exist Figure 1 In the illustrated embodiment, actual operating parameters of steel plate length, steel plate width, corrosion defect width, corrosion defect depth, temperature, seawater conductivity, and tensile displacement caused by external loads are input into the corrosion simulation platform input bar.

[0014] exist Figure 2 In the embodiment shown, the corrosion simulation platform user can choose to use geometry, meshing, corrosion defect shape evolution, Von Mises stress distribution, corrosion potential distribution, anode current density distribution, cathode current density distribution according to needs

[0015] And vividly display the evolution results in the form of animation.

[0016] exist Figure 3 In the illustrated embodiment, the two-dimensional geometric shapes of the steel plate containing corrosion defects and the surrounding seawater are drawn: the rectangle and ellipse of the geometric tool are called, the width and height of the rectangle are set to L (Length) and H (Height), respectively, and the a semi-axis and b semi-axis of the ellipse are set to W (Width) and D (Depth), respectively.

[0017] Figure 4-5 In the illustrated embodiment, the corrosion simulation platform will establish the rectangular geometry of the steel plate and the elliptical geometry of the corrosion defect based on the actual working condition parameters input by the user, and use geometric difference to construct the steel plate with corrosion defects.

[0018] Figure 6-9 In the illustrated embodiment, the corrosion simulation platform will predict the evolution of the shape of corrosion defects in steel plates and the Von Mises stress distribution, corrosion potential distribution, anode current density distribution, and cathode current density distribution at the corrosion defects within 20 years at different time steps based on the actual operating parameters input by the user.

Claims

1. A corrosion simulation platform based on the transient pitting growth model under the interaction of mechanics and electrochemistry, characterized by: The method comprises the following steps: (1) drawing the two-dimensional geometric shapes of the steel plate with corrosion defects and the surrounding seawater: calling the rectangle and ellipse of the geometric tool, the width and height of the rectangle are set to L (Length) and H (Height), the a semi-axis and b semi-axis of the ellipse are set to W (Width) and D (Depth), respectively, and selecting the geometric difference set to construct the steel plate model with corrosion defects. (2) setting the initial state of the steel plate in the simulated seawater: the left and lower ends of the steel plate with corrosion defects in the simulated seawater are fixed boundaries, and the lower end is electrically grounded, the right end of the steel plate is only allowed to have lateral displacement and the controlled displacement method is used, and the upper end of the steel plate is a free boundary. The corrosion defect boundary is the anode, and the two ends of the upper surface of the steel plate are the cathode, and the formation of oxide film is considered. (3) using finite element to calculate the stress distribution on the surface of the corrosion defect and the current potential distribution of seawater; comprising the following steps (3.1)-(3.8): (3.1) setting the solid mechanics module: setting the elastic-plastic deformation on the linear elastic material node by adding the plastic node, and adding the high-strength corrosion-resistant steel material used for marine engineering. Set the initial yield stress, hardening function, Young's modulus, Poisson's ratio, and import the uniaxial tensile and compressive stress-strain curve of the steel plate. Set the initial value of the displacement field, set the boundary conditions of the "Solid Mechanics" physical field interface, and set the displacement in the X direction to disp (mm); (3.2) Set the secondary current distribution module: set the initial values ​​of the electrolyte conductivity and electrolyte potential, and define the anode and cathode reaction expressions; (3.3) Divide the grid, select the free triangular grid, set a finer grid at the corrosion defect boundary, and the maximum unit size of the corrosion defect and non-defect part is 0.001 and 0.01 respectively. Select free deformation in the deformation geometry in the physical field toolbar, and the mesh smoothing type is hyperelastic; (3.4) Set up the study, add a steady-state study solver, and create the Step 1: Steady-state to calculate the solid mechanics module and the Step 2: Steady-state to calculate the secondary current distribution module. Add a transient study, the time unit list is a (year), and select interpolation (0,1,2,5,10,20) in the output time step, inherit the parameter solution of the previous steady-state study from the solution list; calculate the Von Mises stress, corrosion potential, and cathode current density at the corrosion defect for the App development in step (4); (4) Create a corrosion simulation platform: call the AppDeveloper module, select the basic template, a template with a subwindow, the top of the subwindow is a ribbon, the left side is a form collection bar, and contains a graphic object. The input bar creates the steel plate size L and H, the corrosion defect size W and D, the weather temperature T and seawater conductivity sigmal in the marine environment, and the external tensile displacement disp. The function area button selects the geometric model, mesh division, corrosion defect shape evolution, Von Mises stress, corrosion potential, anode current density, cathode current density and annual calculation results as each frame for animation playback. When the actual working parameters change, the corrosion simulation App Developer automatically updates the solution and gives real-time simulation results; (5) Corrosion simulation platform delivery: Through the COMSOL compiler deployment tool, the corrosion simulation software is generated and delivered to mobile phones, tablets and personal computers. COMSOL Server further builds a web-based running application cloud server for the corrosion simulation App Developer. In the hardening function formula (1): ε p is the plastic strain, σ e is the elastic stress (MPa), σ ys is the yield stress (MPa), E is the elastic modulus; in the electrochemical field formulas (2)-(4): i a and i c are the current densities of the anode and cathode of the steel plate (A / m 2 ), the superscript 0 indicates the stress-free state, b a and b c are the Tafel slopes (V) of the anode and cathode of the steel plate respectively; in formula (3) is the anode equilibrium potential of the steel plate (V), △P is the absolute value of the hydrostatic part of the stress tensor (MPa), V m is the molar molecular volume (m 3 / mol), z is the charge transferred by the anodic dissolution reaction, F is the Faraday constant (C / mol), R is the gas constant (J / mol·K), υ is the direction factor (usually 0.4-0.5), α is the constant coefficient (1.67×10 11 cm -2 ), N0 is the initial dislocation density; the first term is the equilibrium potential of the anode reaction when there is no stress, which can be solved according to the Nernst equation; the second term is the negative shift of the anode equilibrium potential caused by elastic stress; The third term is the negative shift of the anode equilibrium potential caused by plastic strain; Mises is the Von Mises stress (MPa). Therefore, a multi-physics field cycle related to tensile displacement and corrosion defect size is generated, namely defect geometry deformation → stress → corrosion → defect geometry deformation → stress; the mathematical concept of deformation geometry interface is introduced in the modeling to describe the evolution of corrosion defect shape of Q420NS. The growth of the defect in width and depth is related to the loss of steel, and the solution allows the defect area to be fully filled. The deformation geometry velocity perpendicular to the boundary between Q420NS steel / seawater is expressed as formula (5), where M is the molar mass (g / mol) and ρ is the density (g / cm 3 ). When the parameters change in the actual working conditions, step (3.4) will be run to update the solution and the drawing of the result graph, and finally synchronized to the corrosion simulation platform. s yhard =max[0,σ exp (e p +s e / E)-s ys ] (1)

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