An indirect measurement method for inherent strain parameters of welded joints

Abstract

The present invention discloses an indirect measurement method for inherent strain parameters of welding joints in the field of deformation control technology, aiming to solve the problem in the prior art that it is impossible to achieve low-cost measurement of inherent strain parameters under the premise of ensuring credibility. The method includes measuring the actual value of welding deformation of the welding joint; establishing a simulation model of the welding joint; setting an initial strain value, performing inherent strain method welding simulation, and calculating the welding deformation simulation value of the simulation model; adjusting the strain value so that the obtained welding deformation simulation value approaches the actual value of welding deformation; when the deviation between the welding deformation simulation value and the actual value of welding deformation is less than a set limit value, it is determined that the strain value set at this time is the required inherent strain parameter; the present invention is applicable to inherent strain method welding simulation of welding joints, and can achieve the effect of convenient, reliable and low-cost measurement of inherent strain parameters under the premise of ensuring the credibility of the results.

Description

Technical Field

[0001] The present invention relates to the technical field of deformation control, and in particular to a method for indirectly measuring inherent strain parameters of a weld joint. Background Art

[0002] When simulating welding using the inherent strain method, the inherent strain parameters are applied as initial strain values ​​to the welds of the welded structure and its nearby units, and elastic-plastic finite element numerical calculations are performed to achieve a mechanical equilibrium state between the units near the welds and the constraints of the entire model. The welding deformation distribution of the welded structure is obtained through simulation. When simulating the welding deformation of the structure, the simulation calculation effect has obvious advantages over the traditional thermo-elastic-plastic method welding simulation.

[0003] When simulating welding with the inherent strain method, obtaining the inherent strain parameters of the weld joint is an important part of the welding simulation and determines the accuracy of the welding simulation results. The existing ways to obtain the inherent strain parameters are divided into thermoelastic simulation method, overall measurement method, and micro-area measurement method. For the thermoelastic simulation method, the thermoelastic simulation itself has many parameters, especially the material thermophysical parameters, heat source model and other parameters, which usually deviate from the actual measurement, resulting in a reduction in the credibility of the final calculation results. For the overall measurement method, the average value is calculated after measuring the overall plastic strain value. Since the inherent strain varies greatly at different positions in the weld, this method is not accurate. For the micro-area measurement method, the stress and strain are directly measured by drilling holes in a local micro area to obtain the inherent strain parameters. A portable three-coordinate measuring instrument with high measurement accuracy is required. The equipment is expensive and the price is as high as nearly one million yuan.

[0004] Therefore, how to achieve low-cost measurement of inherent strain parameters while ensuring credibility is a key technical problem that needs to be solved urgently. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an indirect measurement method for the inherent strain parameters of a weld joint, so as to solve the current problem that it is impossible to achieve low-cost measurement of the inherent strain parameters while ensuring reliability.

[0006] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0007] The present invention provides an indirect measurement method for inherent strain parameters of a weld joint, comprising the following steps:

[0008] Measure the actual value of welding deformation of welding joints;

[0009] Establish a simulation model of the welded joint;

[0010] Setting an initial strain value, performing inherent strain method welding simulation, and calculating a welding deformation simulation value of the simulation model;

[0011] Adjusting the strain value so that the obtained welding deformation simulation value approaches the actual welding deformation value;

[0012] When the deviation between the welding deformation simulation value and the actual welding deformation value is less than the set limit value, it is determined that the strain value set at this time is the required inherent strain parameter.

[0013] Furthermore, the method for measuring the actual value of welding deformation of the welded joint includes:

[0014] Establish a standard 3D model of the weld joint;

[0015] Adjust the position and posture of the standard test plate so that the constructed standard specimen is consistent with the standard three-dimensional model;

[0016] Welding the standard test plate and measuring the position data of the standard test plate before and after welding;

[0017] The difference in position data before and after welding is calculated to obtain the actual value of welding deformation of the weld joint.

[0018] Furthermore, the method for establishing a standard three-dimensional model of a weld joint includes:

[0019] Determine the type of weld joint to be measured;

[0020] According to the type of welded joint, determine and count the relevant dimensions and process parameters of the welded joint;

[0021] A standard 3D model of the welded joint is established based on relevant dimensions and process parameters.

[0022] Furthermore, the types of welding joints include: T-joints, corner joints, lap joints, butt joints, bottom-lock joints and non-standard joints;

[0023] Among them, non-standard connectors include a collection other than the other 5 types of connectors.

[0024] Furthermore, the relevant dimensions and process parameters of the welded joint include: weld size, manufacturing material, shape and position dimensions and welding process.

[0025] Furthermore, when welding the standard test plate, the selected welding specification should be consistent with the type of weld joint;

[0026] If the welding specification deviation exceeds the allowable limit during welding, the welding is judged to have failed, and the standard sample is replaced and the welding is repeated.

[0027] Furthermore, the method of adjusting the position and posture of the standard test plate so that the constructed standard specimen is consistent with the standard three-dimensional model includes:

[0028] Use the point-matching fixture to adjust the position and posture of the standard test plate to be consistent with the standard three-dimensional model;

[0029] Assemble the adjusted standard test plate.

[0030] Furthermore, the method for measuring the position data of the standard test plate before and after welding includes:

[0031] Before adjusting the position and posture of the standard test plate, drill the standard test plate;

[0032] Before welding the standard test plate, measure the position data of the drill hole;

[0033] After welding the standard test plate, the position data of the drilled holes are measured when the standard test plate cools down to room temperature.

[0034] Furthermore, the position data includes the spacing or height difference of the drill holes.

[0035] Furthermore, the strain value includes: filler metal temperature difference and linear expansion coefficient.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The present invention uses the welding deformation of the standard specimen as a link for indirect measurement. By combining numerical simulation with actual measurement results, the inherent strain parameters are jointly determined. This allows for convenient, reliable, and low-cost measurement of the inherent strain parameters while ensuring the credibility of the results.

[0038] 2. The present invention subdivides welded joints into six major types based on their structural forms, and establishes technical standards that specify factors affecting welding deformation measurement results, such as the dimensional deviation range of standard test plates, the accuracy of joints and assembly, and the floating range of welding current and voltage. This ensures that the welding deformation distribution of the standard specimen is equal to the actual value of the welding deformation of the welded joint, thereby improving the reliability of the obtained inherent strain parameters;

[0039] 3. The present invention formulates corresponding measurement processes and measurement specifications according to the types of welding joints, thereby constructing an inherent strain database of welding joints and ensuring the validity of welding deformation measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0041] Figure 1 This is a flow chart of a method for indirect measurement of inherent strain parameters of a weld joint provided by the present invention;

[0042] Figure 2 It is a cross-sectional schematic diagram of a T-joint;

[0043] Figure 3 is a cross-sectional schematic diagram of a corner joint;

[0044] Figure 4 is a cross-sectional schematic diagram of a lap joint;

[0045] Figure 5 is a cross-sectional schematic diagram of a butt joint;

[0046] Figure 6 It is a cross-sectional schematic diagram of the lock bottom joint;

[0047] Figure 7 This is a three-dimensional model diagram of the T-joint;

[0048] Figure 8 This is a three-dimensional model diagram of the corner joint;

[0049] Figure 9 This is a three-dimensional model diagram of the lap joint;

[0050] Figure 10 The three-dimensional model diagram of the butt joint;

[0051] Figure 11 This is a three-dimensional model diagram of the lock bottom joint;

[0052] Figure 12 Schematic diagram of the drilling position of the T-joint;

[0053] Figure 13 Schematic diagram of the drilling position of the corner joint;

[0054] Figure 14 Schematic diagram of the drilling position of the lap joint;

[0055] Figure 15 Schematic diagram of the drilling positions for butt joints and bottom lock joints;

[0056] Figure 16 This is a schematic diagram of the location of the T-joint points;

[0057] Figure 17 This is a schematic diagram of the joint position of the corner joint;

[0058] Figure 18 Schematic diagram of the locations of the splicing points of the lap joint;

[0059] Figure 19 This is a schematic diagram of the back joint position of the butt joint;

[0060] Figure 20 This is a schematic diagram of the back assembly point positions of the lock bottom joint. DETAILED DESCRIPTION

[0061] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0062] like Figure 1 As shown, the embodiment of the present invention provides an indirect measurement method for inherent strain parameters of welded joints. This flow chart only shows the logical sequence of the method described in this embodiment. Under the premise of no conflict, in other possible embodiments of the present invention, different methods can be used. Figure 1 The steps shown or described are accomplished in the order shown.

[0063] The present invention proposes a method for measuring inherent strain parameters, which uses the welding deformation of a standard specimen as a link for indirect measurement and combines numerical simulation with actual measurement results to jointly determine the inherent strain parameters.

[0064] It can be understood that, on the one hand, the welding deformation of the standard specimen is the parameter that is easiest to measure. The measurement tool is simple, the measurement is convenient, and the error of the measurement result is small. On the other hand, when simulating welding using the inherent strain method, it is relatively simple to apply the inherent strain simulation parameters to the simulation model. The value of the inherent strain parameter determines the distribution and amplitude of the welding deformation of the standard specimen. By comparing the measured results of the welding deformation of the standard specimen with the simulation results, the inherent strain parameters of the welded joint can be obtained.

[0065] It includes the following steps:

[0066] Step A: measuring the actual value of welding deformation of the welded joint;

[0067] Step B: Establish a simulation model of the welded joint;

[0068] Step C: setting an initial strain value, performing inherent strain method welding simulation, and calculating a welding deformation simulation value of the simulation model;

[0069] Step D: adjusting the strain value so that the obtained welding deformation simulation value approaches the actual welding deformation value;

[0070] Step E: When the deviation between the welding deformation simulation value and the actual welding deformation value is less than the set limit value, it is determined that the strain value set at this time is the required inherent strain parameter.

[0071] It should be noted that the inherent strain method welding simulation refers to applying the inherent strain parameters as the initial strain value to the weld and nearby units of the welded structure, performing elastic-plastic finite element numerical calculations, so that the constraints of the units near the weld and the entire model reach a mechanical equilibrium state, thereby simulating the welding deformation distribution of the welded structure.

[0072] It should also be noted that the inherent strain parameter is a comprehensive value that characterizes the weld deformation near the weld. It is the plastic strain value when the thermal strain interacts with the constraint and phase transformation during the thermal cycle and reaches a state of equilibrium. The inherent strain is the total plastic strain when the internal thermal strain of the weld is in equilibrium with the constraint and phase transformation during the welding thermal cycle. It is the local comprehensive plastic strain value that characterizes the degree of weld deformation near the weld.

[0073] The method for measuring the actual value of welding deformation of a weld joint described in step A includes:

[0074] Step Aa: Establish a standard three-dimensional model of the weld joint;

[0075] Step Ab: Adjust the position and posture of the standard test plate so that the constructed standard specimen is consistent with the standard three-dimensional model;

[0076] It should be noted that the constructed standard specimen is used to equivalently replace the weld joint to be measured, so as to facilitate the actual measurement of the actual value of the welding deformation.

[0077] Step Ac: welding the standard test plate and measuring the position data of the standard test plate before and after welding;

[0078] Preferably, when welding the standard test plate, the selected welding specification should be consistent with the type of welded joint; if the welding specification deviation exceeds the allowable limit during welding, the welding is judged to have failed, and the standard sample is replaced and re-welded.

[0079] In addition, the arc starting and arc ending of welding must be inside the arc starting and arc ending plates at both ends.

[0080] In this embodiment, the standard test plate is made of S355 steel and the welding wire grade is 50-6; the welding specifications are as follows:

[0081] If the following situations occur during welding, the welding is considered to have failed;

[0082] 1. During welding, the current deviation exceeds 20A for 3 seconds or the voltage deviation exceeds 2V for 5 seconds;

[0083] 2. The welding foot size exceeds the set value by 1mm;

[0084] 3. The weld surface excess or depression exceeds the set value by 1mm;

[0085] 4. The average welding speed exceeds the set value by 10%;

[0086] 5. The width difference between the two ends of the weld joint gap exceeds 1mm.

[0087] Step Ad: Calculate the difference in position data before and after welding, that is, obtain the actual value of welding deformation of the welded joint.

[0088] The method for establishing a standard three-dimensional model of a weld joint as described in step Aa includes:

[0089] Step Aaa: Determine the type of weld joint to be measured;

[0090] It should be noted that the types of welding joints include: T-joints, corner joints, lap joints, butt joints, bottom-lock joints and non-standard joints; among them, non-standard joints include a collection other than the other five types of joints.

[0091] In order to reduce the measurement errors generated during the actual measurement process, technical standards have been formulated to specify the dimensional deviation range of standard test plates, for example:

[0092] like Figure 2 As shown, for T-shaped joints, Ta and Tb are the thicknesses of test plates A and B respectively, D1 and D2 are the distances from the left and right surfaces of test plate B to the left and right end surfaces of test plate A, and D1 and D2 are both greater than or equal to Ta, Tb is the smaller value, θ is the angle between the test plates, and 5°<θ<175°;

[0093] like Figure 3 As shown, for the fillet joint, at least one of D1 and D2 is smaller than the smaller value of Ta and Tb, θ is the angle between the test plates, and 30°≤θ≤135°;

[0094] like Figure 4 As shown, for lap joints, θ is the angle between the test plates, and 0≤θ≤5°;

[0095] like Figure 5 As shown in the figure, for butt joints, θ is the angle between the surfaces of test plates A and B, 135°≤θ≤180°.

[0096] like Figure 6 As shown, for the lock bottom joint, Ta and Tb are the thicknesses of test plates A and B, Ta<3Tb, and t is the lock bottom thickness.

[0097] Step Aab: Determine and count the relevant dimensions and process parameters of the welding joint according to the type of the welding joint;

[0098] It should be noted that the relevant dimensions and process parameters of welding joints include: weld size, manufacturing material, shape and position dimensions and welding process.

[0099] Geometric dimensions include surface angle, end distance, root gap, plate thickness, length, groove angle, groove depth, transition chamfer angle, and bend radius. Different types of welded joints contain different elements. Welding process factors include welding parameters (current, voltage, and speed), number of weld layers, welding sequence, welding direction, preheat temperature, and single-wire / double-wire welding.

[0100] Step Aac: Establish a standard three-dimensional model of the weld joint based on relevant dimensions and process parameters;

[0101] It is understandable that in order to facilitate the subsequent construction of standard specimens, it is necessary to first establish a standard three-dimensional model; in order to improve the assembly accuracy of the standard specimens, the size of the test plate assembly used to establish the standard three-dimensional model must be consistent with the standard test plate, and the thickness, joint gap, groove angle, weld size and other parameters of the test plate assembly must be consistent with the design drawings of the welded joint to be measured.

[0102] In this embodiment, the length and width of the test plate assembly are fixed in size, with two specifications of 300mm×200mm and 200mm×150mm. The size of the welding pad is uniformly specified as 200mm×32mm×10mm. The three-dimensional models of various types of welded joints are as follows: Figure 7-11 shown.

[0103] The method described in step Ab for adjusting the position and posture of the standard test plate so that the constructed standard specimen is consistent with the standard three-dimensional model includes:

[0104] Step Aba: Use the point-matching fixture to adjust the position and posture of the standard test plate to be consistent with the standard three-dimensional model;

[0105] For example: The utility model patent with application number CN202121669036.0 "A point assembly tool for calibrating the inherent strain of welding joints" can be used to assemble standard test plates, which can ensure the consistency of the initial state before measurement. In combination with the C-type clamp, the positioning, clamping and spot welding fixation of different types of welding joint samples can be achieved.

[0106] Step Abb: assembling the adjusted standard test plate;

[0107] It is necessary to ensure that the relative position of the standard sample is accurate before the joint is made. Preferably, the surface of the standard test plate is cleaned by grinding with a wire brush, angle grinder, etc. before the joint is made; in this embodiment, the size of the spot welding leg is uniformly specified to be 5mm, and the spot welding position and quantity are specified for each type of joint sample, such as Figure 16-20 shown.

[0108] The method for measuring the position data of the standard test plate before and after welding described in step Ac includes:

[0109] Step Aca: Drilling the standard test plate before adjusting its position and posture;

[0110] It is understandable that the welding deformation of the standard test plate can be reflected by the change of the hole position data. A small bench drill can be used for drilling, using a drill bit with a diameter of 3mm. The drilling depth is required to be greater than 2mm and less than 4mm. The location and number of drilling holes are different for different types of welded joints. The drilling position requirements for the five types of joints are as follows: Figure 12-15 shown.

[0111] Step Acb: Before welding the standard test plate, measure the position data of the drill hole;

[0112] Step Acc: After welding the standard test plate, wait for the standard test plate to cool to room temperature, and then measure the position data of the drilled holes.

[0113] It should be noted that the position data includes the spacing or height difference between the drill holes. The spacing between the drill holes can be measured using a vernier caliper with a range of 0-300mm and an accuracy of 0.02mm. The height difference between the drill holes is measured using a digital height measuring instrument equipped with a digital micrometer.

[0114] In this embodiment, the simulation model of the weld joint established in step B may be a finite element mesh model of a standard specimen established using Hypermesh software.

[0115] The mesh type is a second-order solid tetrahedron. Specific nodes are set at corresponding locations in the mesh model. These locations correspond to the drilled holes in the measured standard specimens, facilitating the extraction of subsequent simulation results. The mesh size is 4.0 mm or 8.0 mm, and the simulation model uses mirror symmetry.

[0116] In addition, considering the possible deviation of simulation results caused by the size and asymmetry of tetrahedral unit mesh, the following measures can be taken to reduce it: First, the tetrahedral mesh size used in simulation calibration is required to be consistent with the mesh size used in pre-processing of the simulation model to eliminate the error caused by the different mesh unit sizes; second, when constructing the simulation model, the finite element model is required to be set as symmetrically as possible to reduce the simulation error caused by the characteristics of the mesh unit.

[0117] Preferably, the strain value includes: filler metal temperature difference and linear expansion coefficient.

[0118] Specifically, in this embodiment, the cooling shrinkage of the weld filler metal is simulated and calculated using the Marc.MSC software. By setting the corresponding temperature difference and linear expansion coefficient for the filler metal, the cooling shrinkage deformation of the weld metal is calculated and the welding deformation distribution of the entire simulation model is simulated.

[0119] The mechanical properties of the test plate assembly were set as follows: Young's modulus and yield strength were identical to those used for the standard test plate, in this case, S355 steel. The thermal conductivity of all elements in the model was set to zero to minimize temperature variations during the calculation. The boundary conditions of the simulation model were set based on the clamping method used for the standard specimen during welding, ensuring good consistency between the two.

[0120] When the linear expansion coefficient and temperature difference of the simulation model make the deviation between the simulation value of the welding deformation of the simulation model and the actual value of the measured welding deformation less than the set limit value of 10%, the linear expansion coefficient and temperature difference set at this time are the required inherent strain parameters.

[0121] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for indirect measurement of inherent strain parameters of welded joints, characterized in that: The following steps are involved: Measure the actual value of welding deformation of welding joints; Establish a simulation model of the welded joint; Setting an initial strain value, performing inherent strain method welding simulation, and calculating a welding deformation simulation value of the simulation model; the strain value includes: filler metal temperature difference and linear expansion coefficient; Adjusting the strain value so that the obtained welding deformation simulation value approaches the actual welding deformation value; When the deviation between the welding deformation simulation value and the actual welding deformation value is less than the set limit value, the strain value set at this time is determined to be the required inherent strain parameter; The method for measuring the actual value of welding deformation of a welded joint comprises: Establish a standard 3D model of the weld joint; Adjust the position and posture of the standard test plate so that the constructed standard specimen is consistent with the standard three-dimensional model; Welding the standard test plate and measuring the position data of the standard test plate before and after welding; Calculate the difference in position data before and after welding to obtain the actual value of welding deformation of the welded joint; The method for measuring the position data of the standard test plate before and after welding includes: Before adjusting the position and posture of the standard test plate, drill the standard test plate; Before welding the standard test plate, measure the position data of the drill hole; After welding the standard test plate, the position data of the drilled holes are measured when the standard test plate cools down to room temperature.

2. The indirect measurement method of inherent strain parameters of welded joints according to claim 1, characterized in that: Methods for establishing standard 3D models of welded joints include: Determine the type of weld joint to be measured; According to the type of welded joint, determine and count the relevant dimensions and process parameters of the welded joint; A standard 3D model of the welded joint is established based on relevant dimensions and process parameters.

3. The indirect measurement method of inherent strain parameters of welded joints according to claim 2, characterized in that: The types of welding joints include: T-joints, corner joints, lap joints, butt joints, bottom lock joints and non-standard joints; Among them, non-standard connectors include a collection other than the other 5 types of connectors.

4. The indirect measurement method of inherent strain parameters of welded joints according to claim 3, characterized in that: The relevant dimensions and process parameters of the welding joint include: weld size, manufacturing material, shape and position dimensions and welding process.

5. The indirect measurement method of inherent strain parameters of welded joints according to claim 4, characterized in that: When welding standard test plates, the selected welding specification should be consistent with the type of weld joint; If the welding specification deviation exceeds the allowable limit during welding, the welding is judged to have failed, and the standard sample is replaced and the welding is repeated.

6. The indirect measurement method of inherent strain parameters of welded joints according to claim 1, characterized in that: Methods for adjusting the position and posture of the standard test plate so that the constructed standard specimen is consistent with the standard three-dimensional model include: Use the point-matching fixture to adjust the position and posture of the standard test plate to be consistent with the standard three-dimensional model; Assemble the adjusted standard test plate.

7. The indirect measurement method of inherent strain parameters of welded joints according to claim 1, characterized in that: The position data includes the spacing or height difference of the drill holes.

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