Flame surface heat treatment simulation method based on Gaussian heat source

Abstract

The invention discloses a flame surface heat treatment simulation method based on a Gaussian heat source. The flame surface heat treatment simulation method comprises the following steps that a target welding part model is obtained; carrying out welding process simulation based on the target welding part model; selecting a corresponding steel high-temperature creep model; designing Gaussian heat source parameters according to actual flame heat treatment equipment; performing flame surface heat treatment simulation on the welded model; and comparing the welding part participates in stress field change before and after heat treatment. Compared with the prior art, a Gaussian heat source is used for simulating a heat source during flame surface heat treatment, accurate simulation of the flame heat source and the moving process of flames on the steel surface are achieved by adjusting heat source parameters, and the thermophysical performance and creep property of the steel at the high temperature are considered; simulation of eliminating welding residual stress through flame surface heat treatment is achieved, and the defect in the technical numerical simulation aspect of eliminating welding residual stress through postweld heat treatment conducted through a flame gun after welding of a large steel structure is completed in the welding heat treatment field is overcome.

Description

Technical Field

[0001] The present invention relates to a simulation method for flame surface heat treatment based on a Gaussian heat source. Background Art

[0002] Research scholars, through the research on the numerical simulation of post-weld heat treatment, hope that when calculating the post-weld heat treatment, the process of heat treatment can be objectively reflected, and all factors affecting the post-weld heat treatment can be considered as much as possible, so as to accurately predict the distribution of the welding stress field of the welded parts after flame surface heat treatment.

[0003] In the prior art, the method of overall heating of the model is adopted, which can only simulate the process of eliminating welding residual stress by overall heating of the welded parts in a resistance furnace. Therefore, this simulation method is only applicable to welded parts that match the size of the resistance furnace, and cannot meet the requirements for research objects in fields such as bridge engineering and building construction. Moreover, the heating processes of overall heating in the resistance furnace and local heating with a flame gun are completely different, as well as their effects on the welded parts. Therefore, how to simulate the process of local heating with a flame gun to eliminate welding residual stress after welding of large steel members has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0004] Aiming at the deficiencies of the above-mentioned prior art, the technical problem to be solved by the present invention is: to provide a simulation method for flame surface heat treatment based on a Gaussian heat source to solve the problem of how to simulate the process of post-weld flame surface heat treatment of large-sized welded parts.

[0005] To solve the above technical problem, a technical solution adopted by the present invention is: to provide a simulation method for flame surface heat treatment based on a Gaussian heat source, including obtaining a target welded part model.

[0006] Conducting numerical simulation of the welding process based on the target welded part model.

[0007] Preferably, the simulation of the welding process uses a double-ellipsoid heat source to simulate the welding heat source, and the double-ellipsoid heat source program is compiled with the ABAQUS software user subroutine DFLUX to achieve the moving loading of the heat source. The heat flux distribution of the double-ellipsoid heat source model is as Figure 3 shown. It can be seen from the figure that the heat flux distribution of this heat source model can be divided into two parts, the front and the rear. The front heat flux density distribution (q1) and the rear heat flux density distribution (q2) can be determined by the following formulas respectively:

[0008] Q = ηUI

[0009]

[0010] f1 + f2 = 2

[0011] Wherein, x0, y0 and z0 are the coordinates of the heat source center, Q is the arc welding power (W), U is the arc voltage (V), I is the welding current (A), η is the arc efficiency, and the arc efficiency of CO2 gas shielded arc welding is taken as 0.8, v is the welding speed (mm / s), f f is the distribution coefficient of the front heat source of the double ellipsoid heat source, f r is the distribution coefficient of the rear heat source of the double ellipsoid heat source, f1 is the heat distribution parameter of the front semi-ellipsoid, f2 is the heat distribution parameter of the rear semi-ellipsoid, and f1 + f2 = 2, and f1 and f2 are taken as 1.2 and 0.8 respectively. Among the shape parameters of the model, b is the depth of the molten pool, c is the width of the molten pool, a1 is the length of the front semi-axis, and a2 is the length of the rear semi-axis.

[0012] The numerical simulation process of the welding process is completed by using the "element birth and death + thermal-mechanical coupling model".

[0013] Preferably, for the "element birth and death + thermal-mechanical coupling model", the use of element birth and death means that the welding process simulates the process of weld filling through the element birth and death function in ABAQUS, that is, before welding starts, all elements representing the weld are "killed", and during welding, the "killed" elements are sequentially "activated" according to the welding time. At the same time, a welding heat source is applied to the sequentially activated weld elements, and the action time of the heat source is the actual welding time;

[0014] Preferably, for the "element birth and death + thermal-mechanical coupling model", the thermal-mechanical coupling model first calculates the temperature field of the welding process, and then uses the calculation result of the temperature field as the load to calculate the stress field;

[0015] Select the corresponding high-temperature creep model for the steel.

[0016] Preferably, the Field&Field model is selected as the high-temperature creep model, and the creep constitutive equation of this model is as follows:

[0017] ε cr =at b σ c

[0018] Where: t = X + F + M, ε cr is the high-temperature creep strain min; X is the time in the heating-up stage; F is the time in the heat-insulating stage; M is the time in the cooling stage; σ is the stress, and ɑ, b, c are parameters related to temperature.

[0019] Design the Gaussian heat source parameters according to the actual flame heat treatment equipment and conduct the simulation of flame surface heat treatment.

[0020] Preferably, the Gaussian heat source is calculated by the following formula:

[0021]

[0022] Among them, α is the heat source absorption coefficient, r is the effective heating radius of the heat source, q m is the maximum heat flux density at the center of the heat source, and q(x, y) is the surface heat flux at the node (x, y).

[0023] Preferably, the Gaussian heat source is implemented through the Dflux subroutine in the ABAQUS software.

[0024] Preferably, the Gaussian heat source controls its movement through time, thereby realizing the movement process of flame heat treatment.

[0025] A method for simulating flame surface heat treatment based on a Gaussian heat source according to the present invention has at least the following beneficial effects: Compared with the prior art, when the present invention uses a Gaussian heat source to simulate the heat source during flame surface heat treatment, the accurate simulation of the flame heat source and the movement process of the flame on the steel surface are realized by adjusting the heat source parameters, and the thermophysical properties and creep properties of the steel at high temperature are considered to realize the simulation of eliminating welding residual stress by flame surface heat treatment, supplementing the lack of numerical simulation in the field of welding heat treatment for eliminating welding residual stress by using a flame gun after welding large steel structures. Description of the Drawings

[0026] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0027] Figure 1 is a flowchart of a specific implementation manner of a method for simulating flame surface heat treatment based on a Gaussian heat source disclosed by the present invention;

[0028] Figure 2 is a schematic diagram of the process of flame surface heat treatment of a welded part with a flame gun in an embodiment of the present invention;

[0029] Figure 3 is a double-ellipsoid heat source model for simulating a welding heat source during the simulation of the welding process in an embodiment of the present invention;

[0030] Figure 4 is a Gaussian heat source model for simulating a flame gun heat source in an embodiment of the present invention;

[0031] Figure 5 is a numerical simulation diagram of the temperature field during the flame surface heat treatment process in an embodiment of the present invention;

[0032] Figure 6 is a distribution nephogram of the welding residual stress field of the welded part before the flame surface heat treatment according to the present invention;

[0033] Figure 7This is the distribution nephogram of the welding residual stress field of the welded part after the surface heat treatment by flame of the present invention. Detailed implementation manners

[0034] The present invention will be further described below with reference to the accompanying drawings.

[0035] A method for simulating the surface heat treatment by flame based on a Gaussian heat source of the present invention includes:

[0036] Obtain a target welded part model;

[0037] Conduct numerical simulation of the welding process based on the target welded part model;

[0038] Select the corresponding high-temperature creep model of steel;

[0039] Design Gaussian heat source parameters according to the actual flame heat treatment equipment;

[0040] Conduct simulation of the surface heat treatment by flame on the model after welding is completed,

[0041] Extract the numerical values of the residual stress of the welded part before and after heat treatment, and compare the influence of the surface heat treatment by flame on the welding residual stress.

[0042] In the prior art, the method of overall heating of the model can only simulate the process of eliminating the welding residual stress by overall heating of the welded part in a resistance furnace. Therefore, this simulation method is only applicable to the welded parts that match the size of the resistance furnace, and cannot meet the requirements for large-size research objects in fields such as bridge engineering and building construction. Generally, a welding torch is used to conduct post-weld heat treatment on the weld area of the welded part, as Figure 2 shown. However, the heat treatment processes of overall heating in the resistance furnace and local heating with a welding torch are completely different, as well as their influences on the welded part. Therefore, how to simulate the process of eliminating the welding residual stress by using a welding torch for post-weld heat treatment after the welding of large steel components has become an urgent problem to be solved by those skilled in the art.

[0043] During specific implementation, a double-ellipsoid heat source program is compiled by using the user subroutine DFLUX of the ABAQUS software for simulating the welding process to realize the moving loading of the heat source. The heat flux distribution of the double-ellipsoid heat source model is as Figure 3 shown. It can be seen from the figure that the heat flux distribution of this heat source model can be divided into two parts, the front part and the rear part. The front heat flux density distribution (q1) and the rear heat flux density distribution (q2) can be determined by the following formulas respectively:

[0044] Q = ηUI

[0045]

[0046] f1 + f2 = 2

[0047] Wherein, x0, y0, and z0 are the coordinates of the heat source center, Q is the arc welding power (W), U is the arc voltage (V), I is the welding current (A), η is the arc efficiency, and the arc efficiency of CO2 gas shielded arc welding is taken as 0.8, v is the welding speed (mm / s), f f is the front heat source distribution coefficient of the double ellipsoid heat source, f r is the rear heat source distribution coefficient of the double ellipsoid heat source, f1 is the heat distribution parameter of the front half ellipsoid, f2 is the heat distribution parameter of the rear half ellipsoid, and f1 + f2 = 2, f1 and f2 are taken as 1.2 and 0.8 respectively. Among the shape parameters of the model, b is the molten pool depth, c is the molten pool width, a1 is the front semi-axis length of the molten pool, and a2 is the rear semi-axis length of the molten pool.

[0048] During specific implementation, the numerical simulation process of the welding process is completed by using the "element birth and death + thermal-structural coupling model". The use of element birth and death means that the welding process simulates the process of weld filling through the element birth and death function in ABAQUS, that is, before welding starts, all elements representing the weld are "killed", and during welding, the "killed" elements are sequentially "activated" according to the welding time. At the same time, the welding heat source is applied to the sequentially activated weld elements, and the action time of the heat source is the actual welding time. The use of the thermal-structural coupling model means that the temperature field during the welding process is first calculated, and then the calculation result of the temperature field is used as the load for the calculation of the stress field;

[0049] During specific implementation, the high-temperature creep model selects the Field&Field model, and the creep constitutive equation of this model is as follows:

[0050] ε cr = at b σ c

[0051] Wherein: t = X + F + M, ε cr is the high-temperature creep strain, min; X is the time during the heating-up stage; F is the time during the heat-insulation stage; M is the time during the cooling stage; σ is the stress; ɑ, b, and c are parameters related to temperature.

[0052] During specific implementation, the flame heat source is simulated by a Gaussian heat source, and the heat flux distribution of the Gaussian heat source is as Figure 4 shown and is calculated through the following formula:

[0053]

[0054] Among them, α is the heat source absorption coefficient, r is the effective heating radius of the heat source, q m is the maximum heat flux density at the heat source center, and q(x, y) is the surface heat flux at the node (x, y);

[0055] In the present invention, the parameters of the Gaussian heat source distribution are determined according to the actual parameters of the actual flame gun.

[0056] As Figure 5 shown, the present invention discloses a simulation method for flame surface heat treatment based on a Gaussian heat source. The simulation of heat source movement during flame surface heat treatment is as Figure 5 .

[0057] The present invention discloses a simulation method for flame surface heat treatment based on a Gaussian heat source. The distribution patterns of residual stress nephograms before and after the flame surface heat treatment of the welded part are as Figure 6 and Figure 7 shown. It can be clearly seen that the residual stress of the welded part has been significantly reduced before and after the heat treatment.

Claims

1. A flame surface heat treatment simulation method based on Gaussian heat source, characterized in that: The following steps are involved: Obtaining a target weldment model; Simulate welding process based on target weldment model; Select the corresponding steel high temperature creep model; Design Gaussian heat source parameters according to actual flame heat treatment equipment; Conduct flame surface heat treatment simulation on the model after welding; Compare the changes in stress field of welded parts before and after heat treatment.

2. A flame surface heat treatment simulation method based on Gaussian heat source as claimed in claim 1, characterized in that: In the step of simulating the welding process based on the target weldment model: the simulation of the welding process uses a double ellipsoid heat source to simulate the welding heat source, and the double ellipsoid heat source program is compiled using the ABAQUS software user subroutine DFLUX to realize the mobile loading of the heat source; the heat flux distribution of the double ellipsoid heat source model is divided into two parts, the front heat flux density distribution (q1) and the rear heat flux density distribution (q2) can be determined by the following formulas respectively: Q=ηUI f1+f2=2 Where x0, y0 and z0 are the coordinates of the heat source center, Q is the arc welding power (W), U is the arc voltage (V), I is the welding current (A), η is the arc efficiency, the arc efficiency of CO2 gas shielded welding is 0.8, v is the welding speed (mm / s), f f is the heat source distribution coefficient in front of the double ellipsoid heat source, f r is the heat source distribution coefficient of the double ellipsoid heat source, f1 is the heat distribution parameter of the front half ellipsoid, f2 is the heat distribution parameter of the back half ellipsoid, and f1+f2=2, f1 and f2 are 1.2 and 0.8 respectively. Among the shape parameters of the model, b is the molten pool depth, c is the molten pool width, a1 is the front half axis length, and a2 is the back half axis length.

3. The flame surface heat treatment simulation method based on Gaussian heat source according to claim 2, characterized in that: In the steps of numerical simulation of welding process: the welding process is completed using birth-death unit and thermal-mechanical coupling model.

4. The flame surface heat treatment simulation method based on Gaussian heat source according to claim 3, characterized in that: In the steps of numerical simulation of welding process: birth and death units are used to simulate the process of weld filling through the birth and death unit function in ABAQUS. Before welding starts, all units representing welds are "killed". During welding, the "killed" units are "activated" in sequence according to the welding time. At the same time, welding heat source is applied to the weld units activated in sequence, and the action time of the heat source is the actual welding time.

5. The flame surface heat treatment simulation method based on Gaussian heat source according to claim 3, characterized in that: In the step of numerical simulation of the welding process: the thermal-mechanical coupling model first calculates the temperature field of the welding process, and then uses the temperature field calculation result as a load to calculate the stress field.

6. A flame surface heat treatment simulation method based on Gaussian heat source according to any one of claims 1 to 5, characterized in that: In the step of selecting the corresponding high temperature creep model for steel: the high temperature creep model uses the Field&Field model, and the creep constitutive equation of the model is as follows: e cr =at b s c Where: t = X + F + M, ε cr is the high temperature creep strain; X is the time of the heating stage; F is the time of the insulation stage; M is the time of the cooling stage; σ is the stress, ɑ, b, c are parameters related to temperature.

7. The flame surface heat treatment simulation method based on Gaussian heat source according to claim 6, characterized in that: In the steps of designing Gaussian heat source parameters according to actual flame heat treatment equipment: The Gaussian heat source is calculated using the following formula: Among them, α is the heat source absorption coefficient, r is the effective heating radius of the heat source, and q m is the maximum heat flux density at the center of the heat source, and q(x,y) is the surface heat flux at the node (x,y).

8. The flame surface heat treatment simulation method based on Gaussian heat source according to claim 7, characterized in that: In the steps of designing Gaussian heat source parameters according to actual flame heat treatment equipment: Gaussian heat source is realized by Dflux subroutine in ABAQUS software.

9. The flame surface heat treatment simulation method based on Gaussian heat source according to claim 6, characterized in that: In the step of designing Gaussian heat source parameters according to actual flame heat treatment equipment: the Gaussian heat source controls its movement through time, thereby realizing the movement process of flame heat treatment.

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