Numerical calculation method for high-frequency induction heating forming of marine complex bent plate

Abstract

The invention discloses a numerical calculation method for high-frequency induction heating forming of a marine complex bent plate, which comprises the following steps: constructing a plate finite element model according to plate geometry and material parameters, and establishing a heat source model based on heat source parameters; according to the position of the heat source model, grid division is conducted on the plate finite element model, electromagnetic field and force field constraint and thermal boundary conditions are set for the plate finite element model, and technological parameters of sail-shaped plate machining are configured; defining a heat source moving track and a cooling water acting range; simulating a high-frequency induction heating forming process based on a multi-physics field coupling mechanism to obtain plate temperature field spatio-temporal evolution data; extracting forming deformation data in combination with the grid change distribution; and finally, the influence rule of geometric / process parameters on the temperature field and the deformation result is analyzed, and the process parameters are optimized. According to the method, the problem that the simulation precision of the complex bent plate forming process is low is solved, full-process dynamic simulation of heat source moving-cooling-deformation is achieved, and the machining precision and the process design efficiency of the sail-shaped plate are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ship and ocean engineering manufacturing technology, and particularly relates to a numerical calculation method for high-frequency induction heating forming of a complex curved plate for a ship. BACKGROUND

[0002] The International Maritime Organization (IMO) recently issued a new greenhouse gas emission reduction rule, which will be fully implemented in 2023. Greenhouse gas emissions in ship engineering not only concentrate on the ship sailing process, but also account for a large proportion in the shipbuilding process. The forming of a large number of hyperbolic and multi-curved plates in ships still mainly adopts the traditional water fire bending plate technology with a flame as a heat source. In flame heating, the combustible gas is mostly methane, acetylene and other gases. The composition of combustible gas is different in different shipyards. Even if the flow rate is consistent, the temperature field results obtained are also different, and there is no repeatability and automation capability. The induction heating is used as the temperature input, and the power supply parameters are controllable. The input current is accurately and stably processed by the induction heat source equipment, including the current size and frequency. For green ships and intelligent manufacturing, the input power of high-frequency induction heating can be used, which is more green and environmentally friendly compared with fossil fuels for flame heating.

[0003] In shipbuilding, the hull plate is the main component for ensuring the design lines, water tightness, bearing external pressure and resisting wave impact of the ship. The quality and efficiency of ship curved plate forming are the key links to restrict the overall construction quality of the ship. With the fierce market competition in the shipbuilding industry worldwide and the proposal of the concept of green ships and intelligent construction, the traditional gas flame heating in the ship plate forming process has the disadvantages of low heating efficiency, poor repeatability and being not conducive to automation operation, which is contrary to the industry trend and recent policies and advocacies. High-frequency induction heating shows its unique advantages in the above aspects. Therefore, it is of great significance to study the numerical simulation forming of ship plate induction heating forming. The sail-shaped plate is a common hyperbolic plate for ships, especially the sail-shaped plate used in the bow and stern of the ship, which can ensure the streamline and structural strength of the ship to reduce the wave making resistance and friction resistance during sailing.

[0004] In the shipbuilding process, water fire bending plate is the main forming method for complex curved plates of the ship. The sail-shaped plate is an important type of hyperbolic plate for ships, and the difficulty of its forming lies in the planning of the sail-shaped plate forming processing strategy. The traditional line heating forming strategy planning relies heavily on human experience. If the deformation of the curved plate to be processed does not meet the requirements, the flame heat source needs to be replaced by an induction coil heat source for secondary processing. The above problems still exist. SUMMARY

[0005] The present application provides a numerical calculation method for high-frequency induction heating forming of a complex curved plate for a ship, which overcomes the problem that the traditional line heating forming strategy relies heavily on human experience and requires secondary heating when the requirements are not met.

[0006] To achieve the above object, the technical scheme of the present application is:

[0007] 1. A numerical calculation method for high-frequency induction heating forming of a complex curved plate for a ship, comprising:

[0008] S1. Constructing a plate finite element model according to geometric parameters and material parameters of the plate, and constructing a heat source model according to heat source parameters of a heating heat source;

[0009] S2. Dividing a grid for the plate finite element model according to a position of the heat source model, and realizing relative movement between the heat source model and the plate finite element model through a constraint equation method to obtain a grid change distribution of the plate finite element model when the heat source model moves;

[0010] S3. Setting electromagnetic field boundary conditions, plate force field constraint conditions and thermal boundary conditions in a processing process for the plate finite element model;

[0011] S4. Setting process parameters in a process of processing the heated plate into a sail-shaped plate through high-frequency induction;

[0012] S5. Setting a moving track of the heat source model and an action range of cooling water on the plate finite element model;

[0013] S6. Simulating electromagnetic heating of the heat source model according to the electromagnetic field boundary conditions, the plate force field constraint conditions, the thermal boundary conditions and the process parameters, and simulating a high-frequency induction heating forming process of the plate along the moving track of the heat source model and the range of the cooling water to obtain a numerical simulation result of temperature distribution on the plate changing with time in a moving process of the heat source model;

[0014] S7. Obtaining deformation data of the plate finite element model generated after high-frequency induction heating forming according to the numerical simulation result and the grid change distribution of the plate finite element model;

[0015] S8. Analyzing influence laws of geometric parameters and process parameters of the plate on the following two items: the numerical simulation result of temperature distribution changing with time; and the deformation data generated after high-frequency induction heating forming to obtain optimal process parameters.

[0016] Further, the heat source model is a double-loop same-direction inductor model; the double-loop same-direction inductor model comprises a coil and a magnetic conductor, wherein the coil adopts a series coil structure.

[0017] Further, the step of dividing a grid for the plate finite element model comprises:

[0018] S21, by heating the model and the state of the plate finite element model in the heating, the distance between the heat source model and the plate finite element model is set to the upper air and the lower air, the upper air above is defined as the moving assembly, and the lower air below is defined as the static assembly; The moving assembly and the static assembly are divided into different density grids; The moving assembly includes the heat source model, the upper air domain and the far field air domain, and the static assembly includes the plate finite element model and the lower air domain; The grid of the upper air domain is aligned with the grid of the lower air domain;

[0019] S22, in the grid division of the static assembly, the grid division is carried out along the thickness direction by using the proportional setting method, the grid layers between the first layer and the last layer in the thickness direction are constrained, and the grid division in the thickness direction is realized by the proportion of the first layer grid thickness and the last layer grid thickness, the encryption grid is realized in the first layer, and the sparse grid is gradually transitioned in the last layer; The first layer is the skin layer side, and the last layer is the core center side, wherein the core is the internal area of the plate thickness direction away from the skin layer;

[0020] S23, the depth of the skin layer is determined by the skin layer depth calculation formula, and the expression is:

[0021]

[0022] In the formula, f is the current frequency of electromagnetic induction, μ is the magnetic conductivity, and σ is the electrical conductivity.

[0023] Further, the expression of the constraint equation is defined as:

[0024]

[0025] In the formula, U(I) is the degree of freedom of the grid node; N is the number of degrees of freedom in the constraint equation.

[0026] Further, the definition of electromagnetic field boundary condition, plate force field constraint condition and thermal boundary condition in step S3 is as follows:

[0027] The electromagnetic field boundary condition includes electromagnetic field vertical boundary condition, electromagnetic field parallel boundary condition, far field boundary condition and electric potential boundary condition; wherein the electromagnetic field vertical boundary condition is X-Y plane, A z =0; Y-Z plane, A x =0; X-Z plane, A y =0; the electromagnetic field parallel boundary condition is X-Y plane, A x =0 and A y =0; Y-Z plane, A x =0 and A z =0; X-Z plane, A y =0 and A z=0; the far-field boundary condition is A x =0, A y =0, A z =0; the potential boundary condition is the cross-section potential of the tail of the inductor is zero.

[0028] The plate piece force field constraint condition is that spring units are arranged at 1 / 4B, 1 / 2B and 3 / 4B positions in the plate width B direction along the surface length direction of the plate piece finite element model, B is the plate piece width, the spring unit is a LINK180 one-way spring unit, which is constrained to be perpendicular to the plate surface of the plate piece finite element model, and only releases upward displacement at the upper end, so as to simulate the upward displacement of the plate edge during processing;

[0029] The thermal boundary condition includes: air convection heat exchange boundary condition, heat conduction boundary condition, thermal radiation boundary condition and water cooling heat exchange boundary condition.

[0030] Further, the specific movement process of the heat source model is:

[0031] S61, setting a heating line constraint condition: setting the heating line length in the process parameters as x meters, setting the starting point of the heating line at x meters away from the edge of the plate piece finite element model, and setting the end point at the edge of the plate piece finite element model;

[0032] S62, setting a heating constraint condition: making the heating heat source take the center point of the heat source model as a reference point; the movement direction of the heat source model is from the starting point of the heating line to the edge of the plate piece finite element model along the heating line;

[0033] S63, setting a motion constraint condition: setting the heating time as n seconds; making the heat source model move at a constant speed in the first 0.8n seconds; in the last 0.2n seconds, the speed of the heat source model is increased to 1.5 times of the speed before the speed change, until the heating is completed after the heating time reaches n seconds.

[0034] The present application has the following beneficial effects:

[0035] The present application carries out numerical calculation on the simulation process of the high induction heating forming of the sail-shaped plate by establishing the plate piece finite element model and the electromagnetic induction heating model, calculates the final deformation of the steel plate according to the geometric parameters and processing parameters of the steel plate, and can be used to judge whether the designed processing parameters are reasonable. The method quantitatively analyzes the influence law of the geometric / processing parameters on the space-time distribution of the temperature field and the final deformation, automatically generates the optimal process parameter combination, can improve the forming efficiency and precision of the complex curved plate of the marine steel, avoids secondary processing, and saves processing cost;

[0036] The electromagnetic field, force field constraint, thermal boundary and cooling water effect are integrated to realize the full-process coupling simulation of "electromagnetic heating-moving heat source-forced cooling-deformation response", and the physical mechanism of transient temperature gradient, thermal stress evolution and final deformation in the sail-shaped plate processing is accurately restored. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0038] Figure 1 The flow chart of the numerical calculation method for the high-frequency induction heating forming of the complex curved plate for ships in the present application;

[0039] Figure 2a The electromagnetic performance parameter display diagram of the Q235B steel material used in the embodiment of the present application;

[0040] Figure 2b The thermal physical performance parameter display diagram of the Q235B steel material used in the embodiment of the present application;

[0041] Figure 2c The mechanical performance parameter display diagram of the Q235B steel material used in the embodiment of the present application;

[0042] Figure 3 The induction heating forming mechanism schematic diagram in the embodiment of the present application;

[0043] Figure 4a The steel plate-air-inductor part grid schematic diagram in the embodiment of the present application;

[0044] Figure 4b The overall grid schematic diagram in the embodiment of the present application;

[0045] Figure 5 The upper and lower air bag grid diagram in the initial state in the embodiment of the present application;

[0046] Figure 6 The upper and lower air bag grid diagram in the heating process in the embodiment of the present application;

[0047] Figure 7 The magnetic flux boundary condition schematic diagram in the embodiment of the present application;

[0048] Figure 8 The sail-shaped plate force field constraint schematic diagram in the embodiment of the present application;

[0049] Figure 9Figure for the process characteristics of high frequency induction heating forming of the sail-shaped plate in the embodiment of the present application;

[0050] Figure 10 Figure for the temperature distribution when the heat source moves to the end point in the embodiment of the present application;

[0051] Figure 11 Figure for the change of the midpoint temperature of the heating line with time in the embodiment of the present application;

[0052] Figure 12 Figure for the distribution of the local shrinkage along the heating line in the embodiment of the present application;

[0053] Figure 13 Figure for the change of the local shrinkage with time in the embodiment of the present application;

[0054] Figure 14 Figure for the change of the deflection with time in the embodiment of the present application;

[0055] Figure 15 Figure for the influence of the plate length, plate width and radius of curvature on the deformation in the embodiment of the present application;

[0056] Figure 16 Figure for the influence of different heating speeds on the maximum temperature of the steel plate surface in the embodiment of the present application;

[0057] Figure 17 Figure for the influence of heating speed on the local shrinkage under different plate thicknesses in the embodiment of the present application;

[0058] Figure 18 Figure for the influence of heating speed on the deflection under different plate thicknesses in the embodiment of the present application;

[0059] Figure 19 Figure for the influence of heating speed on the local shrinkage in the embodiment of the present application;

[0060] Figure 20 Figure for the influence of heating speed on the deflection in the embodiment of the present application.

[0061] In the figure, 1, heating model; 2, coil; 3, magnetic conductor; 4, upper layer of moving air domain grid; 5, plate; 5, lower layer of static air domain grid; 7, plate grid; 8, skin layer; 9, grid along the plate thickness direction; 10, plate width direction grid; 11, plate length direction grid; 12, air bag grid above the heating model; 13, electromagnetic field parallel condition; 14, far field boundary condition; 15, deflection; 16, plate length; 17, plate width; 18, coil moving path. DETAILED DESCRIPTION

[0062] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0063] The embodiment provides a numerical calculation method for high-frequency induction heating forming of a complex curved plate for a ship, as shown in the figure, comprising: Figure 1

[0064] S1, constructing a plate finite element model according to geometric parameters and material parameters of the plate; and constructing a heat source model according to heat source parameters of a heating heat source;

[0065] S2, performing mesh division on the plate finite element model according to the position of the heat source model; and realizing relative movement between the heat source model and the plate finite element model through a constraint equation method to obtain grid change distribution of the plate finite element model when the heat source model moves;

[0066] S3, setting electromagnetic field boundary conditions, plate force field constraint conditions and thermal boundary conditions in a machining process for the plate finite element model;

[0067] S4, setting process parameters in high-frequency induction heating of the plate to process the plate into a sail-shaped plate;

[0068] S5, setting a moving track of the heat source model and an action range of cooling water on the plate finite element model;

[0069] S6, simulating electromagnetic heating of the heat source model according to the electromagnetic field boundary conditions, the plate force field constraint conditions, the thermal boundary conditions and the process parameters, and simulating a high-frequency induction heating forming process of the plate along the moving track of the heat source model and the range of the cooling water; to obtain a numerical simulation result of temperature distribution on the plate changing with time in a moving process of the heat source model;

[0070] S7, obtaining deformation data of the plate finite element model generated after high-frequency induction heating forming according to the numerical simulation result and the grid change distribution of the plate finite element model;

[0071] S8, analyzing influence laws of geometric parameters and process parameters of the plate on the following two items: the numerical simulation result of temperature distribution changing with time; and the deformation data generated after high-frequency induction heating forming; to obtain optimal process parameters.

[0072] ​Specifically, firstly, a plate finite element model is constructed according to plate geometric parameters and material parameters, and a heat source model is established based on the characteristics of a heating heat source; secondly, the plate model is dynamically meshed according to the position of the heat source model, the relative movement coupling of the heat source and the plate model is realized through a constraint equation method, and the grid deformation distribution caused by the movement of the heat source is accurately captured; thirdly, electromagnetic field boundary conditions (excitation source / shielding effect), force field constraint conditions (clamp / boundary constraint) and thermal boundary conditions (convection / radiation heat dissipation) are set, and key process parameters of the sail plate processing are configured, and the movement track of the heat source and the cooling water scope are planned on the plate model, and a complete process simulation environment is constructed; then, the heat source model is driven to move along the preset track based on the multi-field boundary conditions and process parameters, the forming process of electromagnetic heating-cooling water action is simulated synchronously, and the space-time distribution data of the plate temperature is output in real time; the deformation after forming is extracted according to the temperature distribution and the grid deformation data; finally, the influence law of geometric / process parameters on the temperature field evolution and the final deformation is analyzed, and the globally optimal process parameters are obtained through iterative optimization.

[0073] Specifically, the geometric parameters are defined to include: plate length L, plate width B, plate thickness t and curvature radius R.

[0074] The material parameters are defined according to actual conditions, including: resistivity RSVX, relative permeability MURX, density DENS, specific heat capacity C, thermal expansion coefficient ALPX, thermal conductivity KXX, elastic modulus EX, Poisson's ratio PRXY and yield strength σ s ;

[0075] In the embodiment, the ship steel type selected is Q235B steel, and the material performance parameters such as resistivity, relative permeability, material density, thermal conductivity, specific heat capacity, Poisson's ratio and linear expansion coefficient are set in the pre-processing stage of the numerical model establishment. The resistivity RSVX, relative permeability MURX, thermal conductivity KXX, specific heat capacity C, Poisson's ratio PRX and thermal expansion coefficient ALPX at different temperatures are as shown in Figure 2a 、 Figure 2b 、 Figure 2c ;

[0076] Preferably, the ambient temperature is defined as 20℃.

[0077] Specifically, the heat source parameters include: coil, size and shape of magnetic conductor.

[0078] The heat source model is a double-loop homopolar inductor model; the double-loop homopolar inductor model includes a coil and a magnetic conductor, wherein the coil adopts a series coil structure.

[0079] In the embodiment, the design of the heat source model can concentrate energy on the target area, reduce energy loss, and improve the thermal efficiency to more than 80%. At the same time, the uniform magnetic field distribution can avoid local overheating, ensure uniform heating of the whole workpiece, and reduce forging defects; outside the working area, the electromagnetic fields generated by the coils are opposite and offset each other, effectively suppressing electromagnetic wave leakage.

[0080] This feature solves the radiation shielding problem of traditional induction heating equipment and improves the operation safety; through optimizing the energy conversion path, the double-loop design directly converts electrical energy into internal heat energy of the workpiece, and the energy utilization rate is more than 90%, which is 30%-50% lower than the traditional heating method; at the same time, there is no open flame and no waste gas emission, which meets the green production requirements; the mechanism of induction heating forming of the heat source model is as shown in Figure 3

[0081] Specifically, the step of meshing the finite element model of the plate includes:

[0082] S21, as shown in Figure 4a , by setting the distance between the heat source model and the plate finite element model as the upper air and the lower air during heating, defining the part above the upper air as a moving component, and defining the part below the lower air as a stationary component; the moving component and the stationary component are divided into grids of different densities; the moving component includes the heat source model, the upper air domain and the far-field air domain, and the stationary component includes the plate finite element model and the lower air domain; the grids of the upper air domain and the lower air domain are aligned with each other;

[0083] S22, in the meshing of the stationary component, the proportional setting method is used to mesh in the thickness direction, as shown in Figure 4b , by constraining the number of layers of grids between the first layer and the last layer in the thickness direction, and the proportion of the thickness of the first layer grid to the thickness of the last layer grid, the meshing in the thickness direction is realized, and the encryption grid is realized in the first layer, and the sparse grid is gradually transitioned in the last layer; the first layer is the skin layer side, and the last layer is the core center side, wherein the core is the internal area of the plate thickness direction away from the skin layer;

[0084] S23, the depth of the skin layer is determined by the skin layer depth calculation formula, and the expression is:

[0085]

[0086] In the formula, f is the current frequency of electromagnetic induction, μ is the magnetic permeability, and σ is the electrical conductivity.

[0087] ​In specific embodiments, the relative movement mode of the heat source model and the plate finite element model mainly has three kinds, which are dynamic loading method, grid re-partitioning method and constraint equation method; the constraint equation method is used in the embodiment to realize the relative movement between the heat source model and the plate finite element model, so as to obtain the grid change distribution of the plate finite element model when the heat source model moves;

[0088] Specifically, in the induction heating process, the continuity of the magnetic vector degree of freedom is maintained by constraining the magnetic vector equation at the interface of the upper and lower air packs, Figure 5 The upper and lower air pack grid states in the initial state are shown, and in order to balance the calculation resources and the calculation accuracy, the air packs at the plate width, the plate length and the position above the inductor are reasonably grid divided and overlapped; meanwhile, the magnetic vector coupling equation between the upper and lower air pack grids in the initial state needs to be deleted at the beginning of the moving heating, Figure 6 The grid diagram of the upper and lower air packs in the induction heating process is shown, the relative movement between the inductor and the workpiece is realized by the constraint equation method, and the magnetic vector coupling equation is re-constrained after movement to realize the continuity of the degrees of freedom between the grids;

[0089] Specifically, the expression of the constraint equation is defined as:

[0090]

[0091] In the formula, U(I) is the degree of freedom of the grid node; N is the number of degrees of freedom in the constraint equation.

[0092] Specifically, the process of calculating the magnetic vector coupling equation is:

[0093] S241, based on the Maxwell equation set, the expression of the process of calculating the magnetic generation electricity, the electricity generation magnetism, the eddy current and the original magnetic field interaction is:

[0094]

[0095] In the formula, H is the magnetic field intensity; J is the current density; E is the electric field intensity; B is the magnetic induction intensity; ω is the sine change angular frequency; D is the electric displacement; and ρ is the charge density.

[0096] S242, the magnetic field vector potential satisfying the following condition is introduced:

[0097]

[0098] S243, the magnetic field intensity, the current density, the electric field intensity and the magnetic induction intensity satisfy the following conditions:

[0099] B = μA (8)

[0100] J = σE (9)

[0101] S244, the electric field intensity is expressed according to the magnetic field vector potential as:

[0102]

[0103] wherein φ is a scalar potential;

[0104] S245, according to the formula 6 to formula 9, the expression of the magnetic vector coupling equation is obtained as:

[0105]

[0106] Specifically, the definition of the electromagnetic field boundary condition, the plate force field constraint condition and the thermal boundary condition in step S3 is as follows:

[0107] The electromagnetic field boundary condition includes electromagnetic field vertical boundary condition, electromagnetic field parallel boundary condition, far field boundary condition and electric potential boundary condition; wherein the electromagnetic field vertical boundary condition is X-Y plane, A z =0; Y-Z plane, A x =0; X-Z plane, A y =0; the electromagnetic field parallel boundary condition is X-Y plane, A x =0 and A y =0; Y-Z plane, A x =0 and A z =0; X-Z plane, A y =0 and A z =0; the far field boundary condition is A x =0, A y =0, A z =0; the electric potential boundary condition is the electric potential of the tail section of the inductor is zero;

[0108] The plate force field constraint condition is that along the surface length direction of the plate finite element model, at the positions of 1 / 4B, 1 / 2B and 3 / 4B in the plate width B direction, B is the plate width, a spring unit is set; the spring unit is a LINK180 one-way spring unit, which is constrained to be perpendicular to the plate surface of the plate finite element model, and only releases upward displacement at the upper end, so as to simulate the upward displacement of the plate edge during processing;

[0109] The thermal boundary condition includes air convection heat exchange boundary condition, thermal conduction boundary condition, thermal radiation boundary condition and water cooling heat exchange boundary condition;

[0110] Preferably, the air convection heat exchange boundary condition is as follows:

[0111]

[0112] Wherein, Nu is Nusselt number, Kxx is thermal conductivity, and l is characteristic length;

[0113] The steel plate surface convective heat transfer coefficient HP is calculated. l ) 10 +(Nu t ) 10 ] 1 / 10 Wherein, Nu l is Nusselt number of complete laminar heat exchange, and Nu t is Nusselt number of complete turbulent heat exchange;

[0114] The calculated steel plate surface convective heat transfer coefficient is shown in Table 1:

[0115] Table 1

[0116]

[0117] The heat conduction boundary condition is as follows:

[0118]

[0119] Wherein, λ is thermal conductivity, T is temperature, ρ is density of material, c is specific heat capacity, t is time, λ, ρ, c and the like change with temperature;

[0120] When the steel plate is not heated, the temperature field of the steel plate and the surrounding is the same, and is the same as the ambient temperature, that is:

[0121] T=T ∞ ,t=0 (14)

[0122] Wherein, T ∞ is ambient temperature;

[0123] The heat radiation boundary condition is as follows:

[0124]

[0125] Wherein, ε is emissivity of material, σ is Stefan-Boltzmann constant, T w is wall temperature, and T ∞ is temperature of environment, and the temperature unit is Kelvin;

[0126] The water cooling heat exchange boundary condition is a numerical simulation heat flow boiling boundary condition, that is, the starting point wall temperature T w(ONB) of bubble state boiling, T w(ONB) is determined according to water temperature, flow rate and heat transfer surface length; the steel plate surface temperature does not exceed T w(ONB) , the water cooling heat exchange boundary condition adopts one-way flow heat exchange, and when the temperature exceeds this temperature, the boundary condition adopts flow bubble state boiling.

[0127] In specific embodiments, the process parameters for processing the plate member include: air gap Agap, heating wire length l, heating wire position, and heating speed v;

[0128] Specifically, the minimum value of the heating speed v is subject to the target deformation and the steel plate material; according to field experience, reducing the heating speed is beneficial to the formation of the sail-shaped plate, but the surface temperature of the plate is too high, which will damage the material of the steel plate; according to the quality standard of Chinese shipbuilding, when the carbon equivalent of Q235B steel exceeds 0.40%, in order to avoid grain coarsening, oxidation and quenching crack, the maximum heating temperature of the surface needs to be strictly controlled below 950℃ under the condition of water cooling immediately after heating; this threshold balances the material performance and the process feasibility, which is the key control point of the heat treatment of the ship steel.

[0129] The heating wire length l is subject to the target deformation and the size of the plate width, and the heating wire length cannot be set at will, and the design of the heating wire length should comprehensively consider the deformation to be processed and the plate width; in the figure, the coil is heated along the moving path. Figure 9

[0130] In specific embodiments, according to the electromagnetic field boundary condition, the plate member force field constraint condition, the thermal boundary condition and the process parameters, the heat source model simulates electromagnetic heating, and the high-frequency induction heating forming process of the plate member is simulated along the moving track of the heat source model and the range of the cooling water; as shown in Figure 10 The numerical simulation result of the temperature distribution on the plate member changing with time during the moving process of the heat source model is obtained;

[0131] In this embodiment, the specific moving process of the heat source model is as follows:

[0132] S61, setting the heating wire constraint condition: setting the heating wire length in the process parameters to 0.3 meters, setting the starting point of the heating wire at 0.3 meters away from the edge of the plate member finite element model, and setting the end point at the edge of the plate member finite element model;

[0133] S62, setting the heating constraint condition: making the heating heat source take the center point of the heat source model as the reference point; the moving direction of the heat source model is from the starting point of the heating wire to the edge of the plate member finite element model along the heating wire;

[0134] S63, setting the motion constraint condition: setting the heating time to 100 seconds; making the heat source model move at a constant speed in the first 80 seconds; in the last 20 seconds, the speed of the heat source model is increased to 1.5 times of the speed before the speed change, until the heating is completed after the heating time reaches 100 seconds.

[0135] ​In specific embodiments, according to the numerical simulation results, the deformation data of the plate finite element model after high-frequency induction heating forming is obtained; wherein, the smaller the time step of the numerical simulation results, the higher the calculation accuracy, but too small time step will waste computing resources, and reasonable time step is 0.5s after multiple verifications.

[0136] In specific embodiments, according to the demand, the standardized temperature and deformation result output result files are set, such as the result files recording the time history change of temperature and deformation and the result files recording the deformation distribution; including but not limited to the following files:

[0137] 1. The result file recording the change of the midpoint temperature of the heating line with time is used for analyzing the change rule of the temperature, and the temperature change curve is drawn by using the data in the file as shown in Figure 11 . In the initial stage of heating, the heat source is far away from the midpoint, and has no effect on the midpoint temperature. As the heat source approaches, the temperature at the midpoint becomes higher and higher. When the heat source moves to the midpoint of the heating line, the temperature rises to the highest temperature of 847.51℃. Then, the heat source moves away, and the temperature at the midpoint gradually decreases, and then decreases sharply under the action of the cooling water until it is consistent with the ambient temperature.

[0138] 2. The result file recording the local shrinkage distribution along the heating line is used for analyzing the distribution rule of the local deformation, and the local shrinkage distribution curve is drawn by using the data in the file as shown in Figure 12 ; the local shrinkage increases first and then slowly increases with the movement of the heat source, and the maximum local shrinkage is 0.499mm. The position of the maximum local shrinkage is at the end of the heating line, because the closer to the plate edge, the smaller the surrounding cold metal area, which causes heat accumulation and increases the expansion process of heating forming, so that the local shrinkage increases.

[0139] 3. The result file recording the local shrinkage and deflection of the midpoint of the heating line with time is used for analyzing the change rule of the deformation of the marine steel sail-shaped plate with time, and the change curves of the local shrinkage and deflection with time are drawn by using the data in the file as shown in Figure 13 and Figure 14 ; in the initial stage, the heat source is far away from the midpoint of the heating line, so the deformation of the sail-shaped plate is not obvious. When the heat source moves to the midpoint of the heating line, the deformation of the sail-shaped plate changes obviously. When the heat source moves to the end of the heating line, the plate produces sharp shrinkage under the action of the cooling water, so that the local shrinkage and deflection increase sharply and finally tend to be stable.

[0140] In specific embodiments, the plate deformation results are compared with the physical experiment results to determine whether the results are consistent under the same parameters; if not, the heat source parameters in S1 are modified to re-simulate; if yes, it indicates that the accuracy of the induction heating forming finite element model is reliable.

[0141] In the present embodiment, the commands of steps S1 to S8 are written as a parameterized program in APDL in Mechanical under the ANSYS software package to realize the whole process of finite element simulation of high-frequency induction heating forming of a sail-shaped plate of a marine steel.

[0142] A physical experiment of line heating forming of a complex curved plate of a marine steel is designed and carried out, and the deformation result of the experiment is recorded; the geometric parameters of the steel plate used in the experiment are consistent with those in step S1, the process parameters are the same as those in step S4, and the material parameters are consistent with those in step S1;

[0143] The parameterized program is read in the ANSYS software, the numerical calculation deformation result of the marine steel plate is output, and is compared with the actual complex curved plate line heating physical experiment result, to determine whether the temperature field and the deformation field of the high-frequency induction heating are consistent with the result observed in the line heating process under the consistent geometric and process parameters, and meet the expectation.

[0144] It is determined whether the error of the numerical calculation result and the experiment is within the engineering allowable range, if not, the error of the heat source parameter setting in the numerical calculation is large, and the simulation is carried out after the heat source parameter in step S1 is modified, if yes, it is indicated that the precision of the numerical calculation model is reliable.

[0145] Specifically, according to the steps in the embodiment of the present application, a reliable command stream suitable for the existing conditions and applicable to the numerical calculation of high-frequency induction heating forming of a sail-shaped plate of a marine low-carbon steel is obtained; different geometric parameters and process parameters are designed in the command stream, a large number of command streams of simulation of high-frequency induction heating forming of a sail-shaped plate of a marine low-carbon steel under different working conditions are obtained; a Windows batch file is designed, and all the command streams are combined by using a batch program; the combined command stream is read, and a large number of result files of temperature and deformation under different working conditions are output; the result files are processed, and the influence law of the geometric parameters and the process parameters on the temperature and the deformation of the high-frequency induction heating forming of the sail-shaped plate of the marine steel is obtained.

[0146] The influence of the plate length, the plate width and the curvature radius on the shrinkage and the deflection is as shown in Figure 15 ;

[0147] The influence of the heating speed on the highest temperature on the surface of the steel plate under different times T is as shown in Figure 16 ; the highest temperature on the surface of the steel plate under the same working condition increases with the decrease of the heating speed; in the actual process, in order to ensure that the material quality of the steel plate is not damaged, the heating speed needs to be controlled so that the highest temperature on the surface of the plate is within the allowable range;

[0148] The influence of the heating speed on the shrinkage and the deflection under different plate thicknesses is as shown in Figure 17 and Figure 18As shown in the drawings; at the same speed, the thicker the steel plate, the smaller the local shrinkage and deflection generated by the line heating forming of the sail-shaped plate; at the same plate thickness, the faster the heating speed, the smaller the local shrinkage and deflection generated, which is caused by the low temperature of the steel plate surface; in order to make the steel plate surface produce deformation, the heating speed should be reduced, but too low heating speed will make the surface temperature of the steel plate too high and lead to the reduction of the performance of the steel plate and even the damage of the material, so the heating speed should be reasonably controlled;

[0149] The influence of heating speed on local shrinkage and deflection is shown in the drawings Figure 19 and Figure 20 When only the heating speed is changed, the slower the heating speed, the greater the local shrinkage and deflection generated, because the heating time is longer when the heating speed is slow, and the steel plate absorbs more heat.

[0150] The present application has the following beneficial effects:

[0151] The present application establishes a plate finite element model and an electromagnetic induction heating model, carries out numerical calculation on the simulation process of high induction heating forming of the sail-shaped plate, calculates the final deformation of the steel plate according to the geometric parameters and processing parameters of the plate, and can be used to judge whether the designed processing parameters are reasonable. The method quantitatively analyzes the influence of geometric / technological parameters on the space-time distribution of the temperature field and the final deformation, automatically generates the optimal process parameter combination, can improve the forming efficiency and precision of the complex curved plate of the marine steel, avoids secondary processing, and saves processing cost;

[0152] The electromagnetic field, force field constraint, thermal boundary and cooling water action are integrated to realize the full-process coupling simulation of "electromagnetic heating-moving heat source-forced cooling-deformation response", and accurately restore the physical mechanism of transient temperature gradient, thermal stress evolution and final deformation in the processing of the sail-shaped plate.

[0153] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A numerical calculation method for high frequency induction heating forming of a complex curved plate for a ship, characterized by, The method comprises the following steps: S1, constructing a finite element model of the plate according to the geometric parameters and material parameters of the plate, and constructing a heat source model according to the heat source parameters of a heating heat source; S2, performing mesh division on the finite element model of the plate according to the position of the heat source model, and realizing the relative movement between the heat source model and the finite element model of the plate through a constraint equation method to obtain the grid change distribution of the finite element model of the plate when the heat source model moves; S3, setting the electromagnetic field boundary condition, the plate force field constraint condition and the thermal boundary condition in the processing of the finite element model of the plate; S4, setting the process parameters in the processing of the plate into a sail-shaped plate through high-frequency induction heating; S5, setting the moving track of the heat source model and the range of the cooling water on the finite element model of the plate; S6, simulating the electromagnetic heating of the heat source model according to the electromagnetic field boundary condition, the plate force field constraint condition, the thermal boundary condition and the process parameters, and simulating the high-frequency induction heating forming process of the plate along the moving track of the heat source model and the range of the cooling water to obtain the numerical simulation result of the temperature distribution on the plate changing with time during the movement of the heat source model; S7, obtaining the deformation data of the plate after high-frequency induction heating forming according to the numerical simulation result and the grid change distribution of the finite element model of the plate; S8, analyzing the influence of the geometric parameters and the process parameters of the plate on the numerical simulation result of the temperature distribution changing with time and the deformation data of the plate after high-frequency induction heating forming to obtain the optimal process parameters.

2. The numerical calculation method of the complex curved plate high-frequency induction heating forming for ship according to claim 1, characterized in that, The heat source model is a double-loop same-direction inductor model, and the double-loop same-direction inductor model comprises a coil and a magnetic conductor, wherein the coil adopts a series coil structure.

3. The numerical calculation method of the complex curved plate high-frequency induction heating forming for ship according to claim 1, characterized in that, The mesh division on the finite element model of the plate comprises the following steps: S21, setting the distance between the heat source model and the finite element model of the plate as the upper air and the lower air according to the state of the heating model and the finite element model of the plate during heating, defining the part above the upper air as a moving component and the part below the lower air as a stationary component, dividing the moving component and the stationary component into grids with different densities, wherein the moving component comprises the heat source model, the upper air domain and the far-field air domain, the stationary component comprises the finite element model of the plate and the lower air domain, and the grids of the upper air domain and the lower air domain are aligned with each other; S22, in the mesh division of the stationary component, the mesh division is performed along the plate thickness direction by using a proportional setting method, the number of layers of the mesh between the first layer and the last layer in the plate thickness direction is constrained, and the proportion of the plate thickness of the first layer mesh to the plate thickness of the last layer mesh is constrained to realize the mesh division in the thickness direction, the first layer is the skin layer side, the last layer is the core center side, and the core is the internal area of the plate thickness direction away from the skin layer; S23, determining the depth of the skin layer by a skin layer depth calculation formula, and the expression is as follows: In the formula, f is the current frequency of electromagnetic induction, μ is the magnetic permeability, and σ is the electrical conductivity.

4. The numerical calculation method of complex curved plate high frequency induction heating forming for ship as claimed in claim 1, wherein, The expression of the constraint equation is defined as follows: In the formula, U(I) is the degree of freedom of the grid node; N is the number of degrees of freedom in the constraint equation.

5. The numerical calculation method of complex curved plate high frequency induction heating forming for ship as claimed in claim 1, wherein, The electromagnetic field boundary condition, the plate force field constraint condition and the thermal boundary condition in step S3 are defined as follows: The electromagnetic field boundary conditions include electromagnetic field perpendicular boundary conditions, electromagnetic field parallel boundary conditions, far-field boundary conditions, and potential boundary conditions; wherein, the electromagnetic field perpendicular boundary condition is the XY plane, A z =0; YZ plane, A x =0; XZ plane, A y =0; the electromagnetic field parallel boundary condition is the XY plane, A x =0 and A y =0; YZ plane, A x =0 and A z =0; XZ plane, A y =0 and A z =0; the far-field boundary condition is A x =0, A y =0, A z =0; the potential boundary condition is the potential of the cross-section at the tail of the inductor. It is zero; The plate force field constraint condition is that a spring unit is arranged at the positions of 1 / 4B, 1 / 2B and 3 / 4B in the plate width B direction along the surface length direction of the plate finite element model, B is the plate width, the spring unit is a LINK180 one-way spring unit, which is constrained to be perpendicular to the plate surface of the plate finite element model, and only releases upward displacement at the upper end, so as to simulate the upward displacement of the plate edge during processing; The thermal boundary condition includes: air convection heat exchange boundary condition, heat conduction boundary condition, thermal radiation boundary condition and water cooling heat exchange boundary condition.

6. The numerical calculation method of complex curved plate high frequency induction heating forming for ship as claimed in claim 1, wherein, The specific movement process of the heat source model is as follows: S61, setting a heating line constraint condition: setting the heating line length in the process parameters as x meters, setting the starting point of the heating line at a distance of x meters from the edge of the plate finite element model, and setting the end point at the edge of the plate finite element model; S62, setting a heating constraint condition: making the heating heat source take the center point of the heat source model as a reference point; the movement direction of the heat source model is from the starting point of the heating line to the edge of the plate finite element model along the heating line; S63, setting a motion constraint condition: setting the heating time as n seconds; making the heat source model move at a constant speed in the first 0.8n seconds; in the last 0.2n seconds, the speed of the heat source model is increased to 1.5 times of the previous speed until the heating is completed after the heating time reaches n seconds.

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