Thermal cycle curve acquisition method and heat source model establishment method

Abstract

The invention discloses a method for acquiring an internal thermal cycle curve of a weld pool. The method comprises the following steps: setting temperature measurement characteristic points according to a welding mode, a welding path and a macroscopic shape of a weld cross section; setting temperature measurement conditions according to the welding seam temperature measurement scheme and then carrying out a welding experiment to obtain a thermal cycle curve in a welding seam molten pool; the temperature measurement feature points comprise a first feature point which is located on a welding path and is a distance lt from the upper surface of a workpiece; the thickness is 0.3 mm; the second feature point is located on a fusion line on the left side and / or the right side of the molten pool morphology, and the distance from the upper surface of the workpiece is lt; the thickness is 0.3 mm; the third feature point is located on the welding path and located in the middle of the workpiece thickness; the fourth feature point is located on a left and / or right fusion line of the molten pool morphology and located in the middle of the thickness of the workpiece; the fifth feature point is located on the welding path and the distance from the lower surface of the workpiece is lt; the thickness is 0.3 mm; the sixth feature point is located on a left and / or right fusion line of the molten pool morphology, and the distance from the sixth feature point to the lower surface of the workpiece is lt; the thickness is 0.3 mm.

Description

Technical Field

[0001] The present invention belongs to the technical field of welding numerical simulation, and specifically relates to a method for obtaining a thermal cycle curve inside a weld molten pool, a method for establishing a thermal cycle curve of a welding heat source, and a method for establishing an efficient and high-precision heat source model. Background Art

[0002] With the development of computer technology, simulation technology has been widely used in various engineering fields. In the field of welding, numerical simulation has developed rapidly in the study of welding temperature field, stress field and deformation. Using simulation technology to simulate the welding process of key components plays an important role in improving product welding quality, optimizing welding technology and eliminating safety hazards.

[0003] In the finite element simulation calculation of stress and deformation of welded structural parts, the calculation results of the thermoelastic-plastic method can provide the historical process of stress and deformation during the welding process, and the calculation accuracy is relatively high. However, for the calculation of stress and deformation field of complex structural parts, the use of mobile heat sources will lead to excessive simulation calculation costs. Therefore, based on the thermoelastic-plastic theory, the heat source model needs to be simplified. The use of thermal cycle curves instead of the traditional thermal cycle curve method with mobile heat sources can improve the calculation efficiency while ensuring a certain calculation accuracy.

[0004] The thermal cycle curve method is a method based on a segmented moving heat source to improve the efficiency of welding simulation calculations. This method applies a thermal cycle curve to the weld, replaces the temperature of all nodes in the weld with a thermal cycle curve, and heats and cools all nodes in the weld at the same time, thereby simulating the welding of an entire weld, thereby improving the efficiency of welding simulation calculations. In the process of using the thermal cycle curve method to establish a simplified heat source model, it is usually necessary to first use the moving heat source method of the thermoelastic-plastic theory to perform transient simulation on the finite element model to simulate the process of its temperature rise and fall. Then add a tracking point to the result, extract the thermal cycle curve of the point, output it into a table form, and then normalize it to obtain a thermal cycle table. The obtained thermal cycle table is loaded onto the finite element model as a simplified welding heat source to perform simulation calculations on large and complex structural parts.

[0005] However, the traditional thermal cycle curve method, as a thermal cycle curve for loading heat sources, is obtained by transient simulation based on the mobile heat source method of thermoelastic-plastic theory. In this process, it is necessary to repeatedly adjust the parameters of the transient heat source model, compare the cross-sectional morphology of the weld obtained by simulation and experiment, and judge the reliability of the calculation results of the heat source model by the degree of agreement between the two, such as patent CN202010843366.0 and patent CN202310712828.9. This process requires a lot of manpower, time and computer resources. In addition, the essence of the mobile heat source method is to simulate the temperature field distribution of welding by establishing a mathematical model. The thermal cycle curve obtained is difficult to achieve a completely consistent effect with the experimental results. After it is loaded onto the finite element model again as a simplified heat source, the accuracy of the simulation results is further reduced.

[0006] To improve the accuracy of welding simulation, it is necessary to measure the real thermal cycle curve in the weld as the heat source through experiments. Due to the small size of the welding pool, the temperature changes very drastically during the welding process, and it is very difficult to measure the temperature field of the molten pool through experiments. In recent years, domestic and foreign scholars have conducted a lot of research on temperature measurement of the welding process through contact measurement and non-contact measurement.

[0007] The non-contact temperature measurement method mainly uses infrared thermal radiation temperature measurement equipment (including monochrome pyrometers, two-color pyrometers and infrared thermal imagers, etc.) and visible light thermal radiation temperature measurement instruments (mainly CCD cameras) to detect the temperature of the molten pool. This method does not directly contact the high-temperature molten pool, does not affect the temperature distribution of the molten pool and the normal progress of processes such as cladding and welding, and has the advantages of wide measurement range, fast dynamic response and high thermal accuracy. However, the equipment used in this method is expensive and the common temperature measurement schemes in previous studies can only measure the surface temperature of the test plate, such as patent CN200510105426.4. During the welding process, affected by the arc and welding smoke near the heat source, the measured results deviate greatly from the actual temperature.

[0008] The contact temperature measurement method generally uses thermocouples for measurement. The basic principle of thermocouples is to use the thermoelectric effect. By measuring the thermoelectric potential in the circuit and combining it with a graduation table, the temperature of the object to be measured can be known. It is widely used in all walks of life. At present, the contact temperature measurement method generally places the thermocouple on the welding test plate for temperature measurement by spot welding, high-temperature glue pasting, and preset pressure pressing, such as patent CN201410539835.4, patent CN202011116556.9, and patent CN201910601333.2. Due to the high temperature of the molten pool, the fast solidification speed, and the strong impact force of the heat source on the welding plate, it is difficult to obtain the thermal cycle curve inside the welding pool using these temperature measurement schemes.

[0009] The disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed before the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of the present application. Summary of the invention

[0010] In view of this, in order to overcome the defects of the prior art, an object of the present invention is to provide a method for obtaining a thermal cycle curve inside a weld molten pool, so as to more accurately obtain the temperature and thermal cycle curve inside the molten pool during the welding process.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions:

[0012] A method for obtaining a thermal cycle curve inside a weld pool comprises the following steps:

[0013] Set temperature measurement feature points according to welding method, welding path and weld cross-section macroscopic morphology, and determine weld temperature measurement scheme;

[0014] Prepare a welding workpiece, set the temperature measurement conditions according to the weld temperature measurement scheme, and then conduct a welding experiment, monitor the temperature of the temperature measurement feature points, and obtain a thermal cycle curve corresponding to a plurality of the temperature measurement feature points in the weld molten pool;

[0015] The number of the temperature measurement feature points is at least 6, including: the first feature point is located on the welding path, and the distance from the upper surface of the workpiece is <0.3mm; the second feature point is located on the fusion line on the left and / or right side of the molten pool morphology, and the distance from the upper surface of the workpiece is <0.3mm; the third feature point is located on the welding path and is located in the middle of the thickness of the workpiece; the fourth feature point is located on the left and / or right fusion line of the molten pool morphology, and is located in the middle of the thickness of the workpiece; the fifth feature point is located on the welding path, and the distance from the lower surface of the workpiece is <0.3mm; the sixth feature point is located on the left and / or right fusion line of the molten pool morphology, and the distance from the lower surface of the workpiece is <0.3mm.

[0016] According to some preferred implementation aspects of the present invention, before setting the temperature measurement feature points, pre-welding is required to be performed according to actual welding conditions and parameters such as weld size, and the weld cross-sectional morphology is obtained based on the pre-welding results. Then, the position of the temperature measurement feature points is determined based on the pre-welding molten pool size.

[0017] According to some preferred implementation aspects of the present invention, the second characteristic point, the fourth characteristic point, and the sixth characteristic point are all located on the fusion line on the left side or on the fusion line on the right side of the molten pool morphology.

[0018] According to some preferred implementation aspects of the present invention, the first feature point and the second feature point are located on the same horizontal plane; the third feature point and the fourth feature point are located on the same horizontal plane; and the fifth feature point and the sixth feature point are located on the same horizontal plane.

[0019] Preferably, the first feature point, the third feature point and the fifth feature point are located on the same vertical plane, and the second feature point, the fourth feature point and the sixth feature point are located on the fusion line on the left or right side of the molten pool morphology.

[0020] More preferably, all temperature measurement feature points are located on the same vertical plane.

[0021] According to some preferred implementation aspects of the present invention, the temperature measurement characteristic points are all located at 1 / 3 to 2 / 3 of the length of the weld. Preferably, the temperature measurement characteristic points are all located at 1 / 2 of the length of the weld, that is, all temperature measurement characteristic points are located on a vertical plane at 1 / 2 of the length of the weld.

[0022] According to some preferred implementation aspects of the present invention, the temperature of the temperature measurement characteristic point is obtained by contact measurement, comprising the following steps:

[0023] Prepare a welding workpiece, open a temperature measurement channel on the welding workpiece, the welding workpiece includes a first weldment and a second weldment, a welding path is formed between the first weldment and the second weldment, and the temperature measurement channel includes a first channel and a second channel;

[0024] Extend the positive electrode of the temperature measuring end of the thermocouple temperature measuring wire from the end of one of the first channel or the second channel into the welding path, extend the negative electrode of the temperature measuring end of the thermocouple temperature measuring wire from the end of the remaining one of the first channel or the second channel into the welding path, and electrically connect the positive electrode and the negative electrode on the welding path so that the connection point of the positive electrode and the negative electrode is located on the temperature measurement characteristic point;

[0025] The other end of the thermocouple temperature measuring line is connected to the temperature recorder to obtain the temperature of the temperature measuring characteristic point in the molten pool during the welding process and the corresponding thermal cycle curve.

[0026] According to some preferred implementation aspects of the present invention, the temperature measuring channel is arranged perpendicular to the welding path.

[0027] According to some preferred implementation aspects of the present invention, the first channel is located on the first weldment, the second channel is located on the second weldment, the first channel and the second channel are located on the same horizontal plane and extend in the same direction and have an intersection with the welding path.

[0028] According to some preferred embodiments of the present invention, the first channel and the second channel are both located on the first weldment or the second weldment; the first channel and the second channel are located on the same horizontal plane and extend in the same direction, and pass through the first weldment or the second weldment to communicate with the welding path.

[0029] According to some preferred embodiments of the present invention, the distance between the first channel and the second channel is greater than 0 mm and less than 0.5 mm.

[0030] According to some preferred implementation aspects of the present invention, the diameter of the temperature measurement channel is less than or equal to 1 / 3 of the thickness of the workpiece.

[0031] According to some preferred implementation aspects of the present invention, the diameter of the thermocouple temperature measuring wire is 70% to 90% of the diameter of the temperature measuring channel.

[0032] According to some preferred implementation aspects of the present invention, the thermocouple is one or more of a K-type thermocouple, a B-type thermocouple, and a C-type thermocouple.

[0033] According to some preferred implementation aspects of the present invention, the temperature of the temperature measurement characteristic point is obtained by non-contact measurement, comprising the following steps:

[0034] Prepare a welding workpiece, a transparent glass sheet and an infrared thermal imaging device; the welding workpiece and the transparent quartz glass sheet are bonded together, and the welding path is parallel to the boundary line between the welding workpiece and the transparent quartz glass sheet;

[0035] The plane where the transparent glass sheet is located is arranged perpendicularly to the plane where the welding workpiece is located;

[0036] The infrared thermal imaging device observes and records the welding process of the longitudinal section of the molten pool on the welding path through the transparent glass sheet, and obtains the temperature of the temperature measurement feature point in the molten pool during the welding process and the corresponding thermal cycle curve.

[0037] Preferably, a tool is provided below the welding workpiece, and the transparent glass sheet is against the edge of the weldment, that is, the welding workpiece and the transparent glass sheet are fitted together, and the welding path is parallel to the boundary line between the welding workpiece and the transparent quartz glass sheet. During the welding process, it is ensured that there is a liquid molten pool on the contact side of the weldment and the quartz glass. The boundary line between the welding workpiece and the transparent quartz glass sheet is used as the welding path for obtaining the temperatures of the first characteristic point, the third characteristic point, and the fifth characteristic point. When the laser heat source is offset a certain distance toward the weldment for welding, the welding path is parallel to the boundary line between the glass sheet / weldment, and the temperature curves of the second characteristic point, the fourth characteristic point, and the sixth characteristic point can be obtained respectively.

[0038] Specifically, when obtaining the temperature curves of the first characteristic point, the third characteristic point, and the fifth characteristic point, the welding path is located on the boundary line between the welding workpiece and the transparent quartz glass sheet, and the (first) welding can be obtained. According to the first welding, the molten pool boundary is obtained, and the laser heat source is moved according to the distance between the first characteristic point and the second characteristic point, the distance between the third characteristic point and the fourth characteristic point, and the distance between the fifth characteristic point and the sixth characteristic point, and another three weldings are performed to obtain the temperature curves of the second characteristic point, the fourth characteristic point, and the sixth characteristic point.

[0039] According to some preferred implementation aspects of the present invention, when the welding method is arc welding, the temperature of the temperature measurement characteristic point is obtained by contact measurement; when the welding method is laser welding, the temperature of the temperature measurement characteristic point is obtained by non-contact measurement. That is, the temperature measurement scheme of the weld includes contact thermocouple measurement of arc welding weld center temperature and non-contact infrared thermal imaging measurement of laser weld center temperature.

[0040] The present invention also provides a method for establishing a thermal cycle curve of a welding heat source, comprising the following steps:

[0041] A thermal cycle curve of at least 6 temperature measurement characteristic points is obtained according to the method for obtaining the thermal cycle curve inside the weld pool as described above;

[0042] The thermal cycle curves of at least 6 temperature measurement characteristic points in the molten pool are fitted and merged to serve as the thermal cycle curve of the welding heat source.

[0043] The present invention also provides a method for establishing a heat source model, comprising the following steps:

[0044] Establish the finite element model of welding three-dimensional solid element;

[0045] Set the thermal and mechanical boundary conditions of the finite element model;

[0046] The thermal cycle curve according to the above welding heat source is loaded into the finite element model as the welding heat source;

[0047] Verify the accuracy of the calculation results and the reliability of the heat source model.

[0048] According to some preferred implementation aspects of the present invention, the loading is to normalize the obtained thermal cycle curve of the welding heat source with the melting point as the standard to obtain a thermal cycle curve table, and load it to the weld node of the finite element model.

[0049] In some embodiments of the present invention, a method for establishing an efficient and high-precision heat source model comprises the following steps:

[0050] S1. Set temperature measurement feature points according to welding method, welding path and weld cross-sectional macroscopic morphology, and determine weld temperature measurement scheme; that is, before setting temperature measurement feature points, pre-welding is required according to actual welding conditions and weld size and other parameters, and the weld cross-sectional morphology is obtained according to the pre-welding results, and then the position of the temperature measurement feature points is determined according to the pre-welding molten pool size;

[0051] S2. Prepare the welding workpiece, set the temperature measurement conditions according to the weld temperature measurement scheme, and then conduct a welding experiment, monitor the temperature of the temperature measurement feature points, and obtain the thermal cycle curves corresponding to the multiple temperature measurement feature points in the weld pool;

[0052] S3. Establish a finite element model of the three-dimensional solid unit of welding based on the welding method, welding process parameters, welding workpiece size and material properties, and the clamping method of the workpiece in the welding experiment;

[0053] S4. Set the thermal boundary conditions and mechanical boundary conditions of the finite element model according to the actual welding process;

[0054] S5. Processing the thermal cycle curves corresponding to the plurality of temperature measurement characteristic points and loading them onto the finite element model as a welding heat source;

[0055] S6. Verify the accuracy of the calculation results and the reliability of the heat source model.

[0056] Among them, the processing is to fit and merge the thermal cycle curves of at least 6 temperature measurement characteristic points in the molten pool to obtain a thermal cycle curve as a welding heat source, and then normalize the obtained thermal cycle curve based on the melting point to obtain a thermal cycle curve table that is loaded onto the weld node of the finite element model.

[0057] Through the above method and final comparison, not only can the time required for heat source verification be greatly shortened, but more accurate simulation results can also be obtained, with the accuracy of the calculated results reaching more than 90% of the actual results. Compared with the traditional thermal cycle curve method verification, the calculation time is shortened by more than 50%.

[0058] Due to the adoption of the above technical scheme, compared with the prior art, the advantages of the present invention are: the method for obtaining the internal thermal cycle curve of the weld molten pool of the present invention, based on the cross-sectional morphology of the weld, selects at least 6 characteristic points for temperature measurement to obtain multiple thermal cycle curves in the molten pool, and then fits and merges them to obtain the thermal cycle curve as the welding heat source, which can reduce the deviation of subsequent simulation calculations and improve the accuracy of the calculation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0060] Figure 1 A schematic flow chart of a method for establishing a heat source model in a preferred embodiment of the present invention;

[0061] Figure 2 Schematic diagram of the positions of multiple temperature measurement feature points in the weld pool in a preferred embodiment of the present invention;

[0062] Figure 3 It is a schematic diagram of the structure of measuring the temperature and thermal cycle curve of the temperature measuring characteristic point in the CMT welding pool by using a K-type thermocouple in the preferred embodiment 1 of the present invention;

[0063] Figure 4 This is a schematic diagram of the installation structure of the K-type thermocouple temperature measuring wire in the weldment according to the preferred embodiment 1 of the present invention;

[0064] Figure 5 The welding three-dimensional solid unit finite element model of the preferred embodiment 1 of the present invention;

[0065] Figure 6 It is a thermal cycle curve diagram of the mobile heat source obtained in the preferred embodiment 1 of the present invention;

[0066] Figure 7 Schematic diagram of the distribution of residual stress measurement points on the weldment surface in preferred embodiment 1 of the present invention;

[0067] Figure 8 This is a comparison diagram of longitudinal residual stress in the length direction of the weld of the preferred embodiment 1 of the present invention;

[0068] Fig. 9 This is a comparison diagram of transverse residual stress in the vertical weld direction of the preferred embodiment 1 of the present invention;

[0069] Fig.10 This is a schematic diagram of the structure of an infrared thermal imaging device for measuring a thermal cycle curve in a laser welding molten pool according to a preferred embodiment 2 of the present invention;

[0070] Fig.11 This is a schematic diagram of a method for measuring a thermal cycle curve in a laser welding molten pool using an infrared thermal imaging device according to a preferred embodiment 2 of the present invention;

[0071] Fig.12 Schematic diagram of the temperature distribution cloud diagram of the longitudinal section of the molten pool and the cross-section of the weld observed through the quartz glass according to the preferred embodiment 2 of the present invention.

[0072] Fig.13 It is a thermal cycle curve diagram of the mobile heat source obtained in the preferred embodiment 2 of the present invention;

[0073] Fig.14 This is a comparison diagram of longitudinal residual stress in the length direction of the weld of the preferred embodiment 2 of the present invention;

[0074] Fig.15 This is a comparison diagram of transverse residual stress in the vertical weld direction of the preferred embodiment 2 of the present invention;

[0075] Fig.16 A schematic diagram of welding offset to obtain the sixth characteristic point in the preferred embodiment 2 of the present invention;

[0076] Among them, the figure marks include: weldment-1, first weldment-11, second weldment-12, first channel-21, second channel-22, welding gun-3, thermocouple temperature measuring line-4, transparent quartz glass sheet-5, tooling fixture-6, laser heat source-7, infrared imaging equipment-8. DETAILED DESCRIPTION

[0077] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0078] On the cross section of the weld, the heating rate, peak temperature, high temperature residence time and solidification speed of each position in the molten pool are all different. It is not accurate to select only the thermal cycle curve of a certain position as a simplified heat source. The method for obtaining the internal thermal cycle curve of the weld molten pool of the present invention is based on the cross-sectional morphology of the weld, selects at least 6 characteristic points for temperature measurement to obtain multiple thermal cycle curves in the molten pool, and then fits and merges them to obtain the thermal cycle curve as the welding heat source, which can reduce the deviation of subsequent simulation calculations and improve the accuracy of the calculation results.

[0079] Specifically, the method for obtaining the internal thermal cycle curve of the weld pool in this embodiment includes the following steps:

[0080] Set temperature measurement feature points according to welding method, welding path and weld cross-section macroscopic morphology, and determine weld temperature measurement scheme;

[0081] Prepare the welding workpiece, set the temperature measurement conditions according to the weld temperature measurement plan, and then conduct the welding experiment. Monitor the temperature of the temperature measurement feature points and obtain the thermal cycle curves corresponding to multiple temperature measurement feature points in the weld molten pool.

[0082] Among them, the number of temperature measurement feature points is at least 6, including: the first feature point is located on the welding path, and the distance from the upper surface of the workpiece is <0.3mm; the second feature point is located on the fusion line on the left and / or right side of the molten pool morphology, and the distance from the upper surface of the workpiece is <0.3mm; the third feature point is located on the welding path, and is located in the middle position of the thickness of the workpiece; the fourth feature point is located on the left and / or right fusion line of the molten pool morphology, and is located in the middle position of the thickness of the workpiece; the fifth feature point is located on the welding path, and the distance from the lower surface of the workpiece is <0.3mm; the sixth feature point is located on the left and / or right fusion line of the molten pool morphology, and the distance from the lower surface of the workpiece is <0.3mm.

[0083] Preferably, the first characteristic point and the second characteristic point are located on the same horizontal plane; the third characteristic point and the fourth characteristic point are located on the same horizontal plane; the fifth characteristic point and the sixth characteristic point are located on the same horizontal plane. The first characteristic point, the third characteristic point, and the fifth characteristic point are located on the same vertical plane, and the second characteristic point, the fourth characteristic point, and the sixth characteristic point are located on the fusion line on the left or right side of the molten pool morphology. All temperature measurement characteristic points are located on the same vertical plane.

[0084] The temperature measurement characteristic points are all located at 1 / 3 to 2 / 3 of the length of the weld. Preferably, the temperature measurement characteristic points are all located at 1 / 2 of the length of the weld, that is, all the temperature measurement characteristic points are located on a vertical plane at 1 / 2 of the length of the weld.

[0085] There are two welding methods, arc welding or laser welding. The peak temperature of laser welding is very high and difficult to measure with thermocouples. Arc welding has arc light and spatter, and infrared measurement will cause great interference. Therefore, when the welding method is arc welding, the temperature of the temperature characteristic point is obtained by contact measurement; when the welding method is laser welding, the temperature of the temperature characteristic point is obtained by non-contact measurement. That is, the temperature measurement scheme of the weld includes contact thermocouple measurement of arc welding weld center temperature and non-contact infrared thermal imaging measurement of laser weld center temperature.

[0086] Specifically, the temperature of the temperature measurement characteristic point is obtained by contact measurement, including the following steps:

[0087] Prepare a welding workpiece, open a temperature measurement channel on the welding workpiece, the welding workpiece includes a first weldment and a second weldment, a welding path is formed between the first weldment and the second weldment, and the temperature measurement channel includes a first channel and a second channel;

[0088] Extend the positive electrode of the temperature measuring end of the thermocouple temperature measuring wire from the end of one of the first channel or the second channel into the welding path, extend the negative electrode of the temperature measuring end of the thermocouple temperature measuring wire from the end of the remaining one of the first channel or the second channel into the welding path, and electrically connect the positive electrode and the negative electrode on the welding path so that the connection point of the positive electrode and the negative electrode is located on the temperature measurement characteristic point;

[0089] The other end of the thermocouple temperature measuring line is connected to the temperature recorder to obtain the temperature of the temperature measuring characteristic point in the molten pool during the welding process and the corresponding thermal cycle curve.

[0090] The temperature measurement channel is arranged perpendicularly to the welding path. The diameter of the temperature measurement channel is less than or equal to 1 / 3 of the thickness of the workpiece. The diameter of the thermocouple temperature measurement line is 70% to 90% of the diameter of the temperature measurement channel. The thermocouple is one or more of a K-type thermocouple, a B-type thermocouple, and a C-type thermocouple.

[0091] There are two ways to set the temperature measurement channel. The first one is that the first channel is located on the first weldment, the second channel is located on the second weldment, the first channel and the second channel are located on the same horizontal plane and extend in the same direction, and have an intersection with the welding path. That is, the first channel and the second channel are located on two weldments respectively and are independently connected, the first channel and the second channel correspond to each other, and are located on the same vertical plane and the same horizontal plane.

[0092] The second type: the first channel and the second channel are both located on the first weldment or the second weldment; the first channel and the second channel are located on the same horizontal plane and extend in the same direction, and pass through the first weldment or the second weldment to communicate with the welding path. The distance between the first channel and the second channel is greater than 0mm and less than 0.5mm. That is, the first channel and the second channel are simultaneously provided on one of the two weldments, and the first channel and the second channel are located on the same horizontal plane.

[0093] The temperature of the temperature measurement feature point is obtained by non-contact measurement, including the following steps:

[0094] Prepare a welding workpiece, a transparent quartz glass sheet and an infrared thermal imaging device; fit the welding workpiece and the transparent glass sheet together, with the welding path being parallel to the boundary line between the welding workpiece and the transparent quartz glass sheet;

[0095] The plane where the transparent quartz glass sheet is located is perpendicular to the plane where the welding workpiece is located;

[0096] The infrared thermal imaging device observes and records the welding process of the longitudinal section of the molten pool on the welding path through the transparent glass sheet, and obtains the temperature of the temperature measurement feature points in the molten pool during the welding process and the corresponding thermal cycle curve. The transparent quartz glass sheet has high light transmittance, which avoids interference with the results obtained by the infrared thermal imaging device.

[0097] Preferably, a tool is provided below the welding workpiece, and the transparent glass sheet is against the edge of the weldment, that is, the welding workpiece and the transparent glass sheet are fitted together, and the welding path is parallel to the boundary line between the welding workpiece and the transparent quartz glass sheet. During the welding process, it is ensured that there is a liquid molten pool on the contact side of the weldment and the quartz glass. The boundary line between the welding workpiece and the transparent quartz glass sheet is used as the welding path for obtaining the temperatures of the first characteristic point, the third characteristic point, and the fifth characteristic point. When the laser heat source is offset a certain distance toward the weldment for welding, the welding path is parallel to the boundary line between the glass sheet / weldment, and the temperature curves of the second characteristic point, the fourth characteristic point, and the sixth characteristic point can be obtained respectively.

[0098] Specifically, when obtaining the temperature curves of the first characteristic point, the third characteristic point, and the fifth characteristic point, the welding path is located on the boundary line between the welding workpiece and the transparent quartz glass sheet, and the (first) welding can be obtained. According to the first welding, the molten pool boundary is obtained, and the laser heat source is moved according to the distance between the first characteristic point and the second characteristic point, the distance between the third characteristic point and the fourth characteristic point, and the distance between the fifth characteristic point and the sixth characteristic point, and another three weldings are performed to obtain the temperature curves of the second characteristic point, the fourth characteristic point, and the sixth characteristic point.

[0099] This embodiment also provides a method for establishing a thermal cycle curve of a welding heat source including the above steps, comprising the following steps:

[0100] According to the above method for obtaining the internal thermal cycle curve of the weld pool, a thermal cycle curve of at least 6 temperature measurement characteristic points is obtained;

[0101] The thermal cycle curves of at least 6 temperature measurement characteristic points in the molten pool are fitted and merged to serve as a simplified thermal cycle curve of the welding heat source.

[0102] This embodiment also provides a method for establishing a heat source model including the above steps, comprising the following steps:

[0103] Establish the finite element model of welding three-dimensional solid element;

[0104] Set the thermal and mechanical boundary conditions of the finite element model;

[0105] The thermal cycle curve according to the above welding heat source is loaded into the finite element model as the welding heat source;

[0106] Verify the accuracy of the calculation results and the reliability of the heat source model.

[0107] The loading step is to normalize the obtained thermal cycle curve of the welding heat source with the melting point as the standard to obtain a thermal cycle curve table, and load it to the weld node of the finite element model.

[0108] Specifically, the heat source model establishment method includes the following steps:

[0109] S1. Set temperature measurement feature points according to welding method, welding path and weld cross-sectional macroscopic morphology, and determine weld temperature measurement scheme; that is, before setting temperature measurement feature points, pre-welding is required according to actual welding conditions and weld size and other parameters, and the weld cross-sectional morphology is obtained according to the pre-welding results, and then the position of the temperature measurement feature points is determined according to the pre-welding molten pool size;

[0110] S2. Prepare the welding workpiece, set the temperature measurement conditions according to the weld temperature measurement scheme, and then conduct a welding experiment, monitor the temperature of the temperature measurement feature points, and obtain the thermal cycle curves corresponding to multiple temperature measurement feature points in the weld pool;

[0111] S3. Establish a finite element model of the three-dimensional solid unit of welding based on the welding method, welding process parameters, welding workpiece size and material properties, and the clamping method of the workpiece in the welding experiment;

[0112] S4. Set the thermal boundary conditions and mechanical boundary conditions of the finite element model according to the actual welding process;

[0113] S5. Process the thermal cycle curves corresponding to the multiple temperature measurement characteristic points and load them onto the finite element model as welding heat sources;

[0114] S6. Verify the accuracy of the calculation results and the reliability of the heat source model.

[0115] Among them, the processing is to fit and merge the thermal cycle curves of at least 6 temperature measurement characteristic points in the molten pool to obtain a thermal cycle curve as a welding heat source, and then normalize the obtained thermal cycle curve based on the melting point to obtain a thermal cycle curve table that is loaded onto the weld node of the finite element model.

[0116] Through the above method and final comparison, the accuracy of the calculated results reached more than 90% of the actual results. Compared with the traditional thermal cycle curve method, the calculation time was shortened by more than 50%.

[0117] Embodiment 1:

[0118] like Figure 1 As shown, in order to reduce the time required for arc welding heat source calibration and improve the calculation accuracy of its simplified heat source, the efficient and high-precision heat source model establishment method of this embodiment includes the following steps:

[0119] Step 1: Set multiple temperature measurement feature points according to the welding method, welding path and weld cross-section macro morphology, such as Figure 2 As shown in the figure, determine the weld temperature measurement plan.

[0120] Step 2: prepare the welding workpiece, set the temperature measurement conditions according to the weld temperature measurement plan, and then conduct a welding experiment. Use a K-type contact thermocouple to measure the temperature change curve of 6 characteristic points in the arc welding pool to obtain the thermal cycle curve of the 6 characteristic points in the weld pool.

[0121] Figure 3 Schematic diagram of the scheme for measuring the thermal cycle curve in the CMT welding pool using a K-type thermocouple. Prepare two aluminum alloy plates (the first weldment and the second weldment) with a size of 100mm×90mm×2mm, and open a through hole with a diameter of 0.28mm in the width direction at the middle position of the length direction of the two weldments. The height of the two through holes (the first channel and the second channel) is the same, that is, they are located on the same horizontal plane. Use a K-type thermocouple temperature measuring wire with a diameter of 0.2mm, and the positive and negative poles of the thermocouple temperature measuring wire are inserted along the two temperature measuring channels respectively. Connect the positive and negative poles of the thermocouple temperature measuring wire at the temperature measuring end by spot welding, and the connection position is located at the corresponding temperature measurement characteristic point; the other ends of the two thermocouple temperature measuring wires are connected to the temperature recorder. Figure 4 This is the installation method of the thermocouple temperature measuring wire at the temperature measuring end of the weldment. The temperature is recorded using a HIOKI LR8400 data recorder, with a data acquisition frequency of 10ms / temperature point.

[0122] according to Figure 3 After the welding workpiece is installed, the CMT welding experiment is carried out according to the process parameters shown in Table 1.

[0123] Table 1 Welding process parameters

[0124] Connector Type Welding current (A) Welding voltage(V) Welding speed (mm / s) Wire diameter (mm) Docking 82 11.9 8 1.2

[0125] After multiple welding, the thermal cycle curves of the 6 characteristic points are obtained. Each temperature measurement characteristic point is welded once, and 6 welding operations are required; or the temperature measurement characteristic points that are not on the same horizontal plane are welded once, that is, the temperature measurement of the first characteristic point, the third characteristic point, and the fifth characteristic point is welded once, and the temperature measurement of the second characteristic point, the fourth characteristic point, and the sixth characteristic point is welded once. That is, at least two welding operations are required.

[0126] Step 3, establishing a finite element model of the three-dimensional solid unit of the welding based on the welding method, welding process parameters, welding workpiece size and material properties, and the clamping method of the workpiece in the welding experiment.

[0127] A geometric model consistent with the size of the welded workpiece is established through professional modeling software, and the model is meshed. In the weld and heat-affected zone, the temperature changes dramatically due to the local heat input of the welding heat source. The mesh in this area is fine and dense to ensure the accuracy of the calculation. The parent material area far away from the weld is heated more evenly and the temperature changes slowly. A 2:1 transition to a sparse grid is used to reduce the overall number of grids and improve calculation efficiency. Figure 5 The finite element model of the three-dimensional solid unit is established.

[0128] Step 4: Set the thermal boundary conditions and mechanical boundary conditions of the finite element model according to the actual welding process.

[0129] In the welding heat process analysis, the ambient temperature and the initial temperature of the workpiece are set to 20°C. The convection heat transfer coefficient between the workpiece and the environment is set to 20W / (m 2 ·K), the radiation heat transfer coefficient is set to 0.6. The workpiece is clamped with a clamp, and the clamping force is set to 98N.

[0130] Step 5, processing the thermal cycle curve obtained in step 2 and loading it onto the finite element model as a welding heat source.

[0131] Specifically, after obtaining the thermal cycle curves of the 6 characteristic points, they are fitted and merged to obtain the thermal cycle curve as the welding heat source, such as Figure 6 shown.

[0132] The obtained thermal cycle curve is normalized with the melting point as the standard to obtain the thermal cycle curve table shown in Table 2. The value of the ordinate in the thermal cycle table represents the room temperature, and 1 represents the melting temperature of the weld material; the value of the abscissa represents the time point when the heat source moves to the middle position of the weld path. The thermal cycle curve table is loaded into the finite element model as the welding heat source.

[0133] Table 2 Thermal cycle curve

[0134] Abscissa-time (s) Vertical axis - temperature normalization -6.24 0.04 -3.22 0.13 -1.64 0.29 -0.74 0.67 -0.2 0.91 0 1.20 0.5 1.01 3.08 0.90 8.6 0.82 16.7 0.72 26.32 0.58 45.04 0.38 63.06 0.27 81.64 0.19 95.26 0.16

[0135] Step 6: Verify the accuracy of the calculation results and the reliability of the heat source model.

[0136] When performing stress analysis on thin plates, the residual stress is usually not taken as an influencing factor in the calculation because of its small size. The longitudinal residual stress in the length direction of the weld and the transverse residual stress in the direction perpendicular to the weld are mainly considered. Figure 7 The distribution diagram of residual stress measurement points on the weldment surface. The stress on the workpiece surface after welding is tested using the blind hole method and compared with the residual stress obtained by simulation. Figure 8 and Fig. 9 The longitudinal residual stress comparison diagram in the weld length direction and the transverse residual stress comparison diagram in the vertical weld direction are shown respectively. It can be seen that compared with the residual stress distribution of the weldment obtained by the traditional thermal cycle curve method, the residual stress distribution obtained in this embodiment is closer to the experimental results, with a maximum deviation of no more than 3%, which enhances the credibility of the simulation results. In addition, this method shortens the amount of engineering calculations and improves the efficiency of simulation.

[0137] Embodiment 2:

[0138] like Figure 1 As shown, in order to reduce the time required for heat source calibration during laser welding and improve the calculation accuracy of the simplified heat source, the efficient and high-precision heat source model establishment method of this embodiment includes the following steps:

[0139] Step 1: Set multiple temperature measurement feature points according to the welding method, welding path and weld cross-section macro morphology, such as Figure 2 As shown in the figure, determine the weld temperature measurement plan.

[0140] Step 2: prepare the welding workpiece, set the temperature measurement conditions according to the weld temperature measurement scheme, and then conduct a welding experiment. Use non-contact infrared thermal imaging to measure the temperature change curve of 6 characteristic points in the laser molten pool to obtain the thermal cycle curve of the 6 characteristic points in the weld molten pool.

[0141] Fig.10 Schematic diagram of the scheme for measuring the thermal cycle curve in the laser welding molten pool using infrared thermal imaging equipment. Prepare an aluminum alloy (weld) with a size of 100mm×90mm×2mm and a transparent quartz glass sheet with a size of 150mm×20mm×2mm. Fig.10 The workpiece is fixed in the scheme shown, and the horizontal plane where the weldment is located is perpendicular to the vertical plane where the transparent quartz glass sheet is located. The welding path is carried out along the joint between the weldment and the quartz glass, or the welding path is offset to the weldment side but remains parallel to the weldment / quartz glass joint. During the welding process, it is ensured that there is a liquid molten pool on the contact side of the workpiece and the quartz glass. The thermal imaging device is fixed on a tripod, and the welding thermal cycle process of the longitudinal section of the molten pool is observed and recorded through the quartz glass, such as Fig.11 shown.

[0142] according to Fig.10 After the welding workpiece is installed, the laser welding experiment is carried out according to the process parameters shown in Table 3.

[0143] Table 3 Laser welding process parameters

[0144] Welding method Laser power(W) Welding speed (mm / s) laser 2340 45

[0145] The thermal cycle curves at 6 characteristic points were obtained by adjusting the distance between the welding path and the joint of the welding workpiece / quartz glass. Fig.12 The temperature distribution cloud map of the longitudinal section of the molten pool and the schematic diagram of the weld cross section observed through the quartz glass are used to analyze the temperature change cloud map on the longitudinal section through software, extract the temperature change process of each point on the surface, and obtain the corresponding thermal cycle curve.

[0146] Specifically, when obtaining the temperature curves of the first characteristic point, the third characteristic point, and the fifth characteristic point, the welding path is located on the boundary line between the welding workpiece and the transparent quartz glass sheet, and the (first) welding can be obtained. The molten pool boundary is obtained according to the first welding, and then the laser heat source is moved to one side of the welding workpiece according to the horizontal distance between the first characteristic point and the second characteristic point, the horizontal distance between the third characteristic point and the fourth characteristic point, and the horizontal distance between the fifth characteristic point and the sixth characteristic point, and another three weldings are performed. At this time, the welding path is parallel to the boundary line between the welding workpiece and the transparent quartz glass sheet, so as to obtain the temperature distribution cloud map and temperature curve of the second characteristic point, the fourth characteristic point, and the sixth characteristic point on the interface between the welding workpiece and the transparent quartz glass sheet.

[0147] like Fig.16 As shown, the left side of the vertical solid line is quartz glass, and the right side is the welding workpiece. The vertical solid line is the interface between the quartz glass and the welding workpiece, which is also the welding path of the first welding. After the first welding, the temperature distribution cloud map of the longitudinal section of the molten pool can be observed through the quartz glass, and then the thermal cycle curves of the first characteristic point, the third characteristic point, and the fifth characteristic point are obtained, and the morphology of half of the molten pool and the molten pool boundary (solid line curve on the right) are obtained, and then the horizontal distance between the first characteristic point and the second characteristic point, the horizontal distance between the third characteristic point and the fourth characteristic point, and the horizontal distance between the fifth characteristic point and the sixth characteristic point can be obtained. After that, the laser heat source is moved to one side of the welding workpiece to move the molten pool boundary (dashed line curve), and the moving distance is controlled so that the sixth characteristic point is located on the interface between the quartz glass and the welding workpiece. The temperature distribution cloud map of the longitudinal section of the molten pool can be observed through the quartz glass, and then the thermal cycle curve of the sixth characteristic point is obtained. The moving distance of the laser heat source is controlled again, and then the thermal cycle curves of the second characteristic point and the fourth characteristic point are obtained respectively.

[0148] Step 3, establishing a finite element model of the three-dimensional solid unit of the welding based on the welding method, welding process parameters, welding workpiece size and material properties, and the clamping method of the workpiece in the welding experiment.

[0149] A geometric model consistent with the size of the welded workpiece is established through professional modeling software, and the model is meshed. In the weld and heat-affected zone, the temperature changes dramatically due to the local heat input of the welding heat source. The mesh in this area is fine and dense to ensure the accuracy of the calculation. The parent material area far away from the weld is heated more evenly and the temperature changes slowly. A 2:1 transition to a sparse grid is used to reduce the overall number of grids and improve calculation efficiency.

[0150] Step 4: Set the thermal boundary conditions and mechanical boundary conditions of the finite element model according to the actual welding process.

[0151] In the welding thermal process analysis, the ambient temperature and the initial temperature of the workpiece are set to 20°C. The convection heat transfer coefficient between the workpiece and the environment is set to 20W / (m 2 ·K), the radiation heat transfer coefficient is set to 0.6. The workpiece is clamped with a clamp, and the clamping force is set to 98N.

[0152] Step 5, processing the thermal cycle curve obtained in step 2 and loading it onto the finite element model as a welding heat source.

[0153] Specifically, the data recorded by the infrared thermal imaging device is extracted to obtain the thermal cycle curves of the 6 characteristic points, which are then fitted and merged to obtain the thermal cycle curve as the welding heat source, such as Fig.13 shown.

[0154] The obtained thermal cycle curve is normalized with the melting point as the standard to obtain the thermal cycle curve table shown in Table 4. The value of the ordinate in the thermal cycle table represents the room temperature, and 1 represents the melting temperature of the weld material; the value of the abscissa represents the time point when the heat source moves to the middle position of the weld path. The thermal cycle curve table is loaded into the finite element model as the welding heat source.

[0155] Table 4 Thermal cycle curve

[0156] Abscissa-time (s) Vertical axis - temperature normalization -0.44 0.18 -0.18 0.20 -0.06 0.26 -0.01 0.61 0 1.20 0.01 0.83 0.08 0.34 0.25 0.26 0.46 0.22 0.87 0.19

[0157] Step 6: Verify the accuracy of the calculation results and the reliability of the heat source model.

[0158] When performing stress analysis on thin plates, the residual stress is usually not taken as an influencing factor in the calculation because of its small size. The longitudinal residual stress in the length direction of the weld and the transverse residual stress in the direction perpendicular to the weld are mainly considered. Figure 7 The distribution diagram of residual stress measurement points on the weldment surface. The stress on the workpiece surface after welding is tested using the blind hole method and compared with the residual stress obtained by simulation. Fig.14 and Fig.15 The longitudinal residual stress comparison diagram in the length direction of the weld and the transverse residual stress comparison diagram in the direction perpendicular to the weld are shown respectively. It can be seen that compared with the residual stress distribution of the weldment obtained by the traditional thermal cycle curve method, the residual stress distribution obtained in this embodiment is closer to the experimental results, with a maximum deviation of no more than 2%, which enhances the credibility of the simulation results. In addition, this method shortens the amount of engineering calculations and improves the efficiency of simulation.

[0159] The method for establishing an efficient and high-precision heat source model of the present invention includes the following steps: setting temperature measurement feature points according to the welding method, welding path and weld cross-section macroscopic morphology to determine the weld temperature measurement scheme; preparing the welding workpiece, setting the temperature measurement conditions according to the weld temperature measurement scheme, and then conducting a welding experiment to obtain the thermal cycle curves of multiple feature point positions in the weld molten pool; establishing a finite element model of a three-dimensional solid unit based on the welding method, welding process parameters, welding workpiece size and material properties, and the clamping method of the workpiece in the welding experiment; setting the thermal boundary conditions and mechanical boundary conditions of the finite element model according to the actual welding process; processing the obtained thermal cycle curve and loading it onto the finite element model as a welding heat source; verifying the accuracy of the calculation results and the reliability of the heat source model. Compared with general methods, the heat source model establishment method provided by the present invention can realize the rapid and accurate verification of the welding heat source, thereby realizing efficient simulation calculation of the welding temperature field, stress field and deformation field. The beneficial effects of the method for establishing an efficient and high-precision heat source model provided by the present invention are:

[0160] 1. The present invention uses the thermal cycle curve in the weld pool measured experimentally as a simplified heat source for simulation calculation. Compared with the traditional thermal cycle curve method, it reduces the steps of obtaining the thermal cycle curve by transient simulation calculation based on the moving heat source method, and reduces the time required for heat source verification. For the simulation process of large and complex components, the efficiency of simulation calculation is greatly improved.

[0161] 2. The mobile heat source method based on the thermoelastic-plastic theory simulates the temperature field distribution of the weldment by establishing a mathematical model. In the process of establishing the mathematical model, certain assumptions are usually set in consideration of the complexity of the welding environment and the computational efficiency and convergence of the simulation results. This leads to a certain deviation between the temperature field of the weldment simulated by this method and the temperature field of the actual weldment. In contrast, the thermal cycle curve of the weld directly measured by the present invention is used as a simplified heat source for simulation calculation with higher accuracy, which is more conducive to accurate analysis of the subsequent stress field and deformation of the weldment.

[0162] 3. The present invention installs the thermocouple wire on the workpiece by processing the temperature measuring channel pair in the width direction at different thickness positions of the welding workpiece. The diameter difference between the temperature measuring channel and the temperature measuring wire does not exceed 30%, which can ensure that the position of the thermocouple temperature measuring point does not move or fall out of the molten pool when impacted by the arc, and accurately obtain the thermal cycle curve at any position inside the welding molten pool.

[0163] 4. In general non-contact temperature measurement schemes, only the temperature of the workpiece surface can be measured, and since there are a lot of arcs and smoke on the weld surface, the measurement results generally have large errors. The present invention clamps and fixes the welding workpiece and transparent quartz glass through a fixture. The welding path is carried out along the joint of the workpiece / quartz glass. The thermal imaging equipment can observe and record the thermal cycle changes of the longitudinal section of the workpiece welding molten pool through the quartz glass, and the observation on the longitudinal section can avoid most of the influence of arcs and smoke, which increases the temperature measurement range of the molten pool and makes the result more accurate.

[0164] 5. In the traditional thermal cycle curve theory, usually only a certain position in the weld is selected to extract the thermal cycle curve calculated based on the moving heat source method, and it is directly loaded on the weld as a welding heat source for calculation. However, on the cross section of the weld, the heating rate, peak temperature, high temperature residence time and solidification speed of each position in the molten pool are all different. It is not accurate to select only a thermal cycle curve at a certain position as a simplified heat source. Based on the cross-sectional morphology of the weld, the present invention selects at least 6 characteristic points for temperature measurement to obtain multiple thermal cycle curves in the molten pool, and then fits and merges them to obtain a thermal cycle curve as a welding heat source, which can reduce the deviation of subsequent simulation calculations and improve the accuracy of the calculation results.

[0165] The above embodiments prepared by the method of the present invention are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for obtaining a thermal cycle curve inside a weld pool, characterized in that: The steps include: Set temperature measurement feature points according to welding method, welding path and weld cross-section macroscopic morphology, and determine weld temperature measurement scheme; Prepare a welding workpiece, set the temperature measurement conditions according to the weld temperature measurement scheme, and then conduct a welding experiment, monitor the temperature of the temperature measurement feature points, and obtain a thermal cycle curve corresponding to a plurality of the temperature measurement feature points in the weld molten pool; The number of the temperature measurement feature points is at least 6, including: the first feature point is located on the welding path, and the distance from the upper surface of the workpiece is <0.3mm; the second feature point is located on the fusion line on the left and / or right side of the molten pool morphology, and the distance from the upper surface of the workpiece is <0.3mm; the third feature point is located on the welding path and is located in the middle of the thickness of the workpiece; the fourth feature point is located on the left and / or right fusion line of the molten pool morphology, and is located in the middle of the thickness of the workpiece; the fifth feature point is located on the welding path, and the distance from the lower surface of the workpiece is <0.3mm; the sixth feature point is located on the left and / or right fusion line of the molten pool morphology, and the distance from the lower surface of the workpiece is <0.3mm.

2. The acquisition method according to claim 1, characterized in that: The second characteristic point, the fourth characteristic point and the sixth characteristic point are all located on the fusion line on the left side or on the fusion line on the right side of the molten pool morphology.

3. The acquisition method according to claim 1, characterized in that: The first feature point and the second feature point are located on the same horizontal plane; the third feature point and the fourth feature point are located on the same horizontal plane; and the fifth feature point and the sixth feature point are located on the same horizontal plane.

4. The acquisition method according to claim 1, characterized in that: The temperature measurement characteristic points are all located at 1 / 3 to 2 / 3 of the weld length.

5. The acquisition method according to claim 1, characterized in that: The temperature of the temperature measurement characteristic point is obtained by contact measurement, including the following steps: Prepare a welding workpiece, open a temperature measurement channel on the welding workpiece, the welding workpiece includes a first weldment and a second weldment, a welding path is formed between the first weldment and the second weldment, and the temperature measurement channel includes a first channel and a second channel; Extend the positive electrode of the temperature measuring end of the thermocouple temperature measuring wire from the end of one of the first channel or the second channel into the welding path, extend the negative electrode of the temperature measuring end of the thermocouple temperature measuring wire from the end of the remaining one of the first channel or the second channel into the welding path, and electrically connect the positive electrode and the negative electrode on the welding path so that the connection point of the positive electrode and the negative electrode is located on the temperature measurement characteristic point; The other end of the thermocouple temperature measuring line is connected to the temperature recorder to obtain the temperature of the temperature measuring characteristic point in the molten pool during the welding process and the corresponding thermal cycle curve.

6. The acquisition method according to claim 5, characterized in that: The first channel is located on the first weldment, the second channel is located on the second weldment, the first channel and the second channel are located on the same horizontal plane and extend in the same direction, and have an intersection with the welding path.

7. The acquisition method according to claim 5, characterized in that: The first channel and the second channel are both located on the first weldment or the second weldment; the first channel and the second channel are located on the same horizontal plane and extend in the same direction, and pass through the first weldment or the second weldment to communicate with the welding path.

8. The acquisition method according to claim 7, characterized in that: The distance between the first channel and the second channel is greater than 0 mm and less than 0.5 mm.

9. The acquisition method according to claim 5, characterized in that: The diameter of the temperature measuring channel is less than or equal to 1 / 3 of the thickness of the workpiece.

10. The acquisition method according to claim 5, characterized in that: The diameter of the thermocouple temperature measuring wire is 70% to 90% of the diameter of the temperature measuring channel.

11. The acquisition method according to claim 5, characterized in that: The thermocouple is one or more of a K-type thermocouple, a B-type thermocouple, and a C-type thermocouple.

12. The acquisition method according to claim 1, characterized in that: The temperature of the temperature measurement characteristic point is obtained by non-contact measurement, including the following steps: Prepare a welding workpiece, a transparent glass sheet and an infrared thermal imaging device; the welding workpiece and the transparent glass sheet are bonded together, and the welding path is parallel to the boundary line between the welding workpiece and the transparent quartz glass sheet; The plane where the transparent glass sheet is located is arranged perpendicularly to the plane where the welding workpiece is located; The infrared thermal imaging device observes and records the welding process of the longitudinal section of the molten pool on the welding path through the transparent glass sheet, and obtains the temperature of the temperature measurement feature point in the molten pool during the welding process and the corresponding thermal cycle curve.

13. The acquisition method according to claim 1, characterized in that: When the welding method is arc welding, the temperature of the temperature measurement characteristic point is obtained by contact measurement; when the welding method is laser welding, the temperature of the temperature measurement characteristic point is obtained by non-contact measurement.

14. A method for establishing a thermal cycle curve of a welding heat source, characterized in that: The steps include: The method for obtaining the internal thermal cycle curve of the weld pool according to any one of claims 1 to 13 obtains a thermal cycle curve of at least 6 temperature measurement feature points; The thermal cycle curves of at least 6 temperature measurement characteristic points in the molten pool are fitted and merged to serve as the thermal cycle curve of the welding heat source.

15. A method for establishing a heat source model, characterized in that: The steps include: Establish the finite element model of welding three-dimensional solid element; Set the thermal and mechanical boundary conditions of the finite element model; Loading the thermal cycle curve of the welding heat source according to claim 14 into the finite element model as the welding heat source; Verify the accuracy of the calculation results and the reliability of the heat source model.

16. The establishment method according to claim 15, characterized in that: The loading is to normalize the obtained thermal cycle curve of the welding heat source with the melting point as the standard to obtain a thermal cycle curve table, and load it to the weld node of the finite element model.

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