Insertion welding structure simulation modeling method considering welding discontinuity and nonuniformity

Abstract

The invention discloses an insertion welding structure simulation modeling method considering welding discontinuity and nonuniformity. The method comprises the steps that firstly, an equivalent welding structure sample is designed according to the actual engineering state, and a simulation model is preliminarily established according to the geometric configuration; obtaining geometric details of a welding seam of a welding structure by adopting a three-dimensional scanning method, and completing reconstruction of geometric features of a welding surface; then, carrying out a fatigue test based on the equivalent welding structure sample to obtain fatigue failure data, and updating model material attributes; then, the fusion line state of the sample fracture morphology is collected, updating is conducted on the basis of the model for reconstructing the geometrical characteristics of the welding surface, and effective characterization of the discontinuous and uneven state of a real welding structure is achieved; according to the invention, discontinuity and nonuniformity of the surface of the welding structure are simulated with higher quality; characterization of the uneven and discontinuous state of the welding structure is achieved, the simulation degree of the model and the real configuration is greatly improved, and the method is more suitable for mechanical analysis.

Description

Technical Field

[0001] The invention relates to the technical field of welding structure simulation modeling, and in particular to an insertion welding structure simulation modeling method taking welding discontinuity and non-uniformity into consideration. Background Art

[0002] In modern industrial society, a large number of steel products need to be processed by welding. Welding is a key core technology for advanced equipment manufacturing. However, the welded structure itself is often very complex and often faces harsh service environments and extreme load conditions. Therefore, the safety and reliability of welded structures have become a major issue to ensure the effectiveness of complex products. Inserted welded structures, as typical connection structures, are widely used in various products such as aviation, aerospace, and nuclear industries. Therefore, studying the failure behavior and fatigue failure mechanism of inserted welded structures is an issue worthy of in-depth study.

[0003] However, for the inserted welding structure with large geometric size mutation and discontinuous structure, the existing simulation modeling methods need further research to achieve high-precision characterization of the characteristic state of its welding structure. The existing simulation finite element model is mainly constructed by importing the geometric model through 3D modeling software, and then directly analyzing or roughly dividing the welding area to analyze its failure process. Although this method can simulate the macroscopic geometric mutation, it cannot reflect the discontinuity and unevenness of the real welding structure. First, the surface of the welding part is uneven at the arc starting and arc ending positions of the weld due to the heat mutation, and the conventional modeling technology cannot reflect this detail. Second, the material properties and microstructure of the welding hot melting area and the unmelted area inside the welding area have significant discontinuity and unevenness, and the conventional simulation modeling process has not yet achieved effective construction. The above factors will greatly affect the performance of the welded structure, resulting in poor generalization ability and low prediction accuracy of the current simulation model analysis. As people's demand for in-depth and accurate understanding of the mechanical response and failure mode of insert welded structures increases, the traditional simulation modeling method of insert welded structures can no longer meet the current needs. It is urgent to develop a high-precision modeling method for insert welded structures that is closer to the actual welding state and takes into account welding discontinuity and non-uniformity.

[0004] Therefore, it is necessary to develop a simulation modeling method for inserted welding structure that takes into account welding discontinuity and non-uniformity to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to design a simulation modeling method for an inserted welding structure taking into account welding discontinuity and non-uniformity in order to solve the above problems.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] The simulation modeling method of inserted welding structure considering welding discontinuity and non-uniformity includes:

[0008] Step 1: Insertion welding structure specimen design: Based on the state of the actual insertion welding structure, combined with the test analysis requirements, based on the model test idea, complete the design of the equivalent test piece of the insertion welding structure, and obtain the insertion welding structure specimen;

[0009] Step 2: Construction of the geometric model of the inserted welding structure: Based on the geometric structure dimensions and material property information of the equivalent test piece in step 1, a preliminary geometric simulation model M0 of the inserted welding structure is established;

[0010] Step 3: Acquisition of external morphology of the weld: In step 1, insert the welded structure specimen entity to perform external morphology scanning, capture the geometric details of the weld, and reversely reconstruct the geometric simulation model M0 of step 2 to obtain the simulation model M1;

[0011] Step 4: Update model material property information: Use the inserted welded structure specimen in step 1 to carry out fatigue tests based on the group method and lift method, obtain fatigue limit and draw PSN curve, and use the test results to update the material property information of the simulation model M1 in step 3;

[0012] Step 5: Welding fusion line measurement: Scan the fracture morphology of the sample after the test in step 4, identify the welding fusion line of the sample, and complete the welding fusion line data measurement;

[0013] Step 6: Reconstruct the simulation model; introduce the fusion line in step 5 into the simulation model M1 in step 3, complete the reconstruction modeling of the welding fusion line in the simulation model, and obtain the simulation model M to realize the characterization of the uneven and discontinuous state of the real welding structure; then divide the model, eliminate hard edges and hard points, set load constraints, and complete the construction of the simulation model.

[0014] Furthermore, the model test in step one is a technology that simplifies, reduces or expands the external influences of the geometric morphology, load and action time of a certain physical phenomenon according to research needs, but ensures that its physical essence remains unchanged; the equivalent test piece design in step one refers to the design activity carried out considering that the size or shape of the inserted welded structure prototype is not easy to meet the actual needs of the test. The test includes installation, loading and clamping. The size or shape of the equivalent test piece here is different from the prototype structure, but its failure behavior and action mechanism are consistent with the prototype structure.

[0015] Furthermore, the external morphology scanning in step three refers to the process of obtaining surface geometric morphology detail data of the welding part of the sample with a certain accuracy using a device with the ability to insert a three-dimensional scanning of the welding structure morphology.

[0016] Furthermore, the reverse reconstruction in step three refers to the process of correcting the original geometric simulation model M0 in step two according to the geometric morphology detail data of the solid surface of the welding part obtained by external morphology scanning, and this process does not affect the original material properties of the original geometric simulation model M0.

[0017] Furthermore, the reverse reconstruction process includes two steps: first, when the axis of the three-dimensional scanning model is not aligned with the axis of the original geometric simulation model, it is necessary to use the center of the geometric simulation model as the axis to reconstruct the central axis of the scanned geometric details; second, the newly created axis is used as the scanning path to reconstruct and supplement the surface geometric details of the original geometric simulation model M0.

[0018] Furthermore, the lifting method in step 4 refers to a method for determining the fatigue limit under a specified number of cycles, and the steps are:

[0019] a. First, use the single-point test method to test the fatigue strength of the sample, that is, use different stress levels to test a sample, and the test stress level gradually decreases from high to low. i >S i+1 >…>S i+n Within the specified cycle number n, the specimen is at the i-th level stress S i If the damage occurs under the action of i+1 ; If the specimen is at the i+k level stress S i+k If the damage occurs under the action of i+k-1 ;

[0020] b. If the specimen is at level i stress S i Under the action of the i+1st stress level S i+1 If the damage occurs under the action of S, then the corresponding fatigue limit must occur at S i and S i+1 If the two stress differences S i -S i+1 Very small, smaller than S i and S i+1 5%, then take S i and S i+1 The average value of is approximately taken as the fatigue strength limit, that is, S i * =1 / 2(S i +S i+1 );

[0021] c. S i and S i+1 Consider it as a pair of data with opposite test results, repeat the above test process, and the paired data S i* Will appear randomly, with at least n* pairs of data from the starting point to the end point, n≥6, at this time, the median fatigue strength estimate is .

[0022] Furthermore, the group method in step 4 refers to a method for determining the median fatigue life or the safe fatigue life based on the test results of a group of specimens at a certain specified stress or strain level.

[0023] Furthermore, the PSN curve in step 4 refers to a material property that reflects the key welding fatigue strength of the sample. It is a curve fitted by the measured fatigue strength and fatigue limit data points. The PSN curve is obtained based on the welded structure-level sample.

[0024] Furthermore, the welding fusion line in step five refers to the intersection critical line between the welding hot melting area and the unmelted base material area, which represents the interface of the non-uniform and discontinuous state area of ​​the real welding structure;

[0025] The weld fusion line analysis in step 5 mainly refers to the process of obtaining the quantitative data of the weld fusion line. Its main steps are:

[0026] a. First, obtain the morphology of the welding fracture area through SEM and other fracture analysis techniques;

[0027] b. The center point of the fracture section of the specimen is determined based on the center of the original design specimen;

[0028] c. Draw multiple reference lines passing through the center point of the fracture section. Along the reference lines, measure the angle of the point where the curvature of the fusion line suddenly changes from the reference line. The radial distance from the point to the center point of the cross section is used as the welding depth. When encountering multiple inflection points on the fusion line, it is necessary to take points at similar positions. The cross section measurement position should be no less than 8 points.

[0029] d. Calibrate the scale according to the scale of the fracture scan image, take the average value as the measurement scale after multiple calibrations, and count the radial distance from the mutation point to the center line of the cross section;

[0030] e. After the measurement is completed, the data points depicting the fusion line contour of a single sample are obtained; the fracture scan is observed to determine the location of the crack initiation, and the line connecting the crack initiation location and the reference origin is used as the reference line for angle measurement. Points are taken in the clockwise direction, and the contour of the fracture scan is compared with the contour of the pattern entity scan. The initial angle between the radial position corresponding to the deepest part of the welding pit and the crack initiation location is determined so that the subsequent modeling can obtain the correct fusion line location.

[0031] Furthermore, the welding fusion line reconstruction modeling in step 6 refers to the process of introducing the welding fusion line into the model according to the welding fusion line measurement results, and the steps are as follows:

[0032] a. Select three points on the fusion line as reference points to establish a reference plane;

[0033] b. Use the maximum radial value of the external welding defect depth to define the axial position of the introduced fusion line, and the maximum radial value of the external welding defect depth to define the circumferential position of the fusion line starting point. Input the coordinates of the feature points extracted from the fusion line into the 3D modeling software to obtain the corresponding feature point positions;

[0034] c. Use Bezier spline curves to connect the feature points, perform interpolation between two separated points, and finally reproduce the welding fusion line in the model.

[0035] The beneficial effects of the present invention are:

[0036] It solves the problem that the traditional welding structure modeling based on geometric dimensions cannot simulate the external geometric morphology of the welding part, and simulates the discontinuity and unevenness of the welding structure surface with higher quality;

[0037] It solves the simulation problem of the welding fusion zone at the weld in the simulation modeling of the welded structure, realizes the characterization of the uneven and discontinuous state of the welded structure, greatly improves the simulation degree of the model and the real configuration, and is more suitable for mechanical analysis;

[0038] This is a guiding technology. The method has a certain degree of openness in practical application. Its application scope is not limited to insertion welding structures, but can be used in the construction process of simulation models of various connection structures with sudden size changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A flowchart of a high-precision simulation modeling method for an insertion welding structure considering welding discontinuity and non-uniformity according to an embodiment of the present invention is shown;

[0040] Figure 2 A schematic diagram of fusion line measurement of a certain inserted welding structure in an exemplary embodiment of a high-precision simulation modeling method for an inserted welding structure considering welding discontinuity and non-uniformity provided according to an embodiment of the present invention is shown;

[0041] Figure 3 A schematic diagram of the reappearance of the weld fusion line of a certain inserted welding structure in an exemplary embodiment of a high-precision simulation modeling method for an inserted welding structure considering welding discontinuity and non-uniformity provided in accordance with an embodiment of the present invention is shown; wherein A is a schematic diagram before the reappearance, and B is a schematic diagram after the reappearance;

[0042] Figure 4A schematic diagram of an inserted welding structure specimen established in an exemplary embodiment of a high-precision simulation modeling method for an inserted welding structure considering welding discontinuity and non-uniformity provided in accordance with an embodiment of the present invention is shown; wherein A is a schematic diagram of the overall structure, and B is a schematic diagram of a partially enlarged structure;

[0043] Figure 5 A schematic diagram of a simulation model M0 of an inserted welding structure specimen in an exemplary embodiment of a high-precision simulation modeling method for an inserted welding structure considering welding discontinuity and non-uniformity provided in accordance with an embodiment of the present invention is shown; wherein A is a schematic diagram of the overall structure, and B is a schematic diagram of a partially enlarged structure;

[0044] Figure 6 A schematic diagram of obtaining the external morphology state of the weld of an inserted welding structure sample in an exemplary embodiment of a high-precision simulation modeling method for an inserted welding structure considering welding discontinuity and non-uniformity provided according to an embodiment of the present invention is shown; wherein A is a schematic diagram of the overall structure, and B is a schematic diagram of a partially enlarged structure;

[0045] Figure 7 A schematic diagram of a local welding area of ​​a simulation model M1 reconstructed in an exemplary embodiment of a high-precision simulation modeling method for an inserted welding structure considering welding discontinuity and non-uniformity provided according to an embodiment of the present invention is shown; wherein A is a schematic diagram of the overall structure, and B is a schematic diagram of a partially enlarged structure;

[0046] Figure 8 The result diagram of the consistent failure mechanism of the physical specimen and the simulation model in an exemplary embodiment of a high-precision simulation modeling method for an inserted welding structure taking into account welding discontinuity and non-uniformity provided according to an embodiment of the present invention is shown; wherein A is a schematic diagram of the physical specimen, and B is a schematic diagram of the simulation model. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions 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 part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0048] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0050] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use, or are directions or positional relationships commonly understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0051] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and are not to be understood as indicating or implying relative importance.

[0052] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms such as "setting" and "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings.

[0054] The present invention provides a high-precision simulation modeling method for inserted welding structures that takes into account welding discontinuity and non-uniformity. First, an equivalent welding structure specimen is designed according to the actual engineering state and a simulation model is preliminarily established according to the geometric configuration; then a three-dimensional scanning method is used to obtain the geometric details of the weld of the welding structure and complete the reconstruction of the geometric features of the welding surface; then a fatigue test is carried out based on the equivalent welding structure specimen, fatigue failure data is obtained, and the model material properties are updated; then, by collecting the fusion line state of the specimen fracture morphology, an update is performed on the basis of the model of the reconstructed welding surface geometric features, so as to achieve effective characterization of the discontinuous and non-uniform state of the real welding structure.

[0055] The following combination Figure 1 An embodiment of the present invention is described. A high-precision simulation modeling method for an insertion welding structure taking into account welding discontinuity and non-uniformity comprises:

[0056] Step 1: Insert welded structure specimen design

[0057] Based on the state of the real inserted welded structure, combined with the test analysis requirements and based on the model test concept, the equivalent test piece design of the inserted welded structure is completed, and the inserted welded structure specimen is obtained;

[0058] Step 2: Insert welding structure geometry model construction

[0059] Based on the geometric structure dimensions and material property information of the equivalent test piece in step 1, a geometric simulation model M0 of the inserted welding structure is preliminarily established;

[0060] Step 3: Obtaining the external morphology of the weld

[0061] In step 1, insert the welded structure sample entity to perform external morphology scanning, capture the weld geometry details, and reversely reconstruct the geometric simulation model M0 of step 2 to obtain the simulation model M1;

[0062] Step 4: Update model material property information

[0063] Use the inserted welded structure specimen in step one to carry out fatigue tests based on the group method and lift method, obtain the fatigue limit and draw the PSN curve, and use the test results to update the material property information of the simulation model M1 in step three;

[0064] Step 5: Welding fusion line measurement

[0065] Scan the fracture morphology of the sample after the test in step 4, identify the welding fusion line of the sample, and complete the welding fusion line data measurement;

[0066] Step 6: Simulation model reconstruction

[0067] The fusion line described in step 5 is introduced into the simulation model M1 described in step 3, and the reconstruction modeling of the welding fusion line in the simulation model is completed to obtain the simulation model M, so as to realize the characterization of the uneven and discontinuous state of the real welding structure. Then the model is segmented, hard edges and hard points are eliminated, and appropriate load constraints are set to complete the construction of the simulation model.

[0068] Among them, the "model test" mentioned in step one mainly refers to the technology that simplifies, reduces or expands the external influences such as the geometric morphology, load, and action time of a certain physical phenomenon according to research needs, but ensures that its physical essence remains unchanged.

[0069] Among them, the "equivalent test piece design" mentioned in step one mainly refers to the design activities carried out considering that the size or shape of the insert welding structure prototype is not easy to meet the actual needs of the test such as installation, loading, clamping, etc. The size or shape of the equivalent test piece here is different from the prototype structure, but its failure behavior, action mechanism and prototype structure remain consistent.

[0070] Among them, the "external morphology scanning" described in step three mainly refers to the process of using a device with the ability to insert a three-dimensional scanning of the welding structure morphology to obtain the surface geometric morphology detail data of the welding part of the sample with a certain accuracy.

[0071] Among them, the "reverse reconstruction" described in step three mainly refers to the process of correcting the original geometric simulation model M0 in step two according to the geometric morphology detail data of the solid surface of the welding part obtained by external morphology scanning. It should be noted that this process does not affect the original material properties of the original geometric simulation model M0.

[0072] Optionally, the process includes two steps: first, when the axis of the three-dimensional scanning model does not coincide with the axis of the original geometric simulation model, it is necessary to reconstruct the central axis of the scanned geometric details with the center of the geometric simulation model as the axis; secondly, the newly created axis is used as the scanning path to reconstruct and supplement the surface geometric details of the original geometric simulation model M0.

[0073] The "lift and drop method" described in step 4 mainly refers to a method for determining the fatigue limit under a specified number of cycles. The steps are:

[0074] a. First, use the single-point test method to test the fatigue strength of the sample, that is, use different stress levels to test a sample, and the test stress level gradually decreases from high to low (S i >S i+1 >…>S i+n ), within the specified cycle number n, the specimen is at the i-th level stress S i If the damage occurs under the action of i+1 If the specimen is at the i+k level stress S i+k If the damage occurs under the action of i+k-1 .

[0075] b. If the specimen is at level i stress S i Under the action of the i+1st stress level S i+1 If the damage occurs under the action of S, then the corresponding fatigue limit must occur at S i and S i+1 If the two stress differences S i -S i+1 Very small, smaller than S i and S i+1 5%, then take S i and S i+1 The average value of is approximately taken as the fatigue strength limit, that is, S i * =1 / 2(S i +S i+1 ).

[0076] c. S i and S i+1 Consider it as a pair of data with opposite test results, repeat the above test process, and the paired data S i * Will appear randomly, with at least n* pairs of data (n≥6) from the starting point to the end point. At this time, the median fatigue strength estimate is .

[0077] Among them, the "group method" described in step 4 mainly refers to a method for determining the median fatigue life or safe fatigue life based on the test results of a group of specimens at a specified stress (or strain) level. For example, when using the group method to obtain a median fatigue life with a reliability of 50%, the number of valid specimens in each group n shall not be less than 3. When processing data, logarithms of all fatigue life observations are taken in advance, and then the sub-sample average values ​​are calculated according to formula (1) and formula (2) respectively. and the sub-sample standard deviation s.

[0078] (1)

[0079] Where:

[0080] n——the number of individuals contained in the subsample, that is, the number of observations in an experimental group;

[0081] ——Each observation x in an experimental group i The average value of

[0082] (2)

[0083] If a group of n fatigue life observations N1, N2, N3, ..., N n According to formula (1), the average value of logarithmic fatigue life sub-samples is obtained for:

[0084] (3)

[0085] Will As an estimator of the mean of the normal population , then

[0086] (4)

[0087] (5)

[0088] The median fatigue life estimate can be obtained from the above formula: , that is, fatigue life with 50% reliability.

[0089] Among them, the "PSN curve" described in step 4 mainly refers to a material property that reflects the key welding fatigue strength of the sample. It is a curve fitted by the measured fatigue strength and fatigue limit data points. The PSN curve described in this article is obtained based on the welding structure-level sample, which is more realistic than the traditional sample obtained only based on the material sample.

[0090] Among them, the "welding fusion line" described in step five mainly refers to the critical line of intersection between the welding hot melting area and the unmelted base material area, which represents the interface of the uneven and discontinuous state area of ​​the real welding structure.

[0091] Among them, the "weld fusion line analysis" in step 5 mainly refers to the process of obtaining quantitative data of the weld fusion line, such as Figure 2 As shown, the main steps are:

[0092] a. First, obtain the morphology of the welding fracture area through SEM and other fracture analysis techniques;

[0093] b. The center point of the fracture section of the specimen is determined based on the center of the original design specimen;

[0094] c. Draw multiple reference lines passing through the center point of the fracture section. Along the reference lines, measure the angle of the point where the curvature of the fusion line suddenly changes from the reference line. The radial distance from the point to the center point of the cross section is used as the welding depth. When encountering multiple inflection points on the fusion line, it is necessary to take points at similar positions. The cross section measurement position should be no less than 8 points.

[0095] d. Calibrate the scale according to the scale of the fracture scan image, take the average value as the measurement scale after multiple calibrations, and count the radial distance from the mutation point to the center line of the cross section;

[0096] e. After the measurement is completed, the data points depicting the fusion line profile of a single sample are obtained. Observe the fracture scan to determine the location of the crack initiation. The line connecting the location of the crack initiation and the reference origin is used as the reference line for angle measurement. Points are taken in the clockwise direction, and the contour of the fracture scan is compared with the contour of the sample entity scan to determine the initial angle between the radial position corresponding to the deepest part of the welding pit and the crack initiation position, so that the subsequent modeling can obtain the correct fusion line position.

[0097] The "welding fusion line reconstruction modeling" described in step 6 mainly refers to the process of introducing the welding fusion line into the model based on the welding fusion line measurement results. The steps are:

[0098] a. Select three points on the fusion line as reference points to establish a reference plane;

[0099] b. Use the maximum radial value of the external welding defect depth to define the axial position of the introduced fusion line, and the maximum radial value of the external welding defect depth to define the circumferential position of the fusion line starting point. Input the coordinates of the feature points extracted from the fusion line into the 3D modeling software to obtain the corresponding feature point positions;

[0100] c. Use Bezier spline curves to connect the feature points, perform interpolation between two points, and finally reproduce the welding fusion line in the model. The process is shown in Figure 3 shown.

[0101] According to an implementation case of the present invention, a high-precision simulation modeling method for insert welding structure considering welding discontinuity and non-uniformity is provided. In an exemplary example of an implementation case of the present invention, the present invention is designed as follows Figure 4 The thin-walled conduit inserted into the welded structure test piece is shown to verify the effectiveness of the proposed method. In actual engineering applications, the thin-walled conduit inserted into the welded structure has the characteristics of large conduit slenderness ratio and sudden change in structural size at the welding part. It is necessary to use the method mentioned in the present invention to establish a more accurate simulation model to guide the failure mechanism analysis of the welded structure and improve the accuracy of the analysis conclusion.

[0102] An exemplary example of applying the method of the embodiment of the present invention to a typical use of inserting a thin-walled conduit into a welding structure will be described below with reference to the accompanying drawings. The exemplary example includes the following steps.

[0103] Step 1: Insertion welding structure specimen design, through the data survey of thin-walled catheter insertion welding structure, according to the use scenario of thin-walled catheter insertion welding structure, the geometric dimensions of the catheter insertion welding studied are clarified, which is 80.25mm long and 10mm wide, and the material selected is stainless steel. And considering the needs of the general standard fatigue testing machine, the following design is made: Figure 4 Insert welded structure specimen shown.

[0104] Step 2: Construction of the geometric model of the inserted welding structure. For the inserted welding structure specimen designed in step 1, the mesh is divided according to the operating mechanism, boundary conditions, material quality, etc. of the actual function of the thin-walled pipe inserted into the welding structure, and then the geometric simulation model M0 of the inserted welding structure is established. Figure 5 shown.

[0105] Step 3: Obtain the external morphology of the weld. Scan the external morphology of the inserted welded structure specimen described in step 1 to capture the weld geometry details. The results are shown in Figure 6 As shown. Figure 6It can be found that there are obvious mutations at the positions of arc starting and arc ending in the weld. This geometric feature has a significant impact on the local stress at the crack initiation position, but it cannot be constructed using the traditional simple simulation model established using geometric dimensions. In order to consider this feature in the finite element model, it is necessary to reconstruct the geometric simulation model M0 of step two. First, the center axis of the geometric morphology details is reconstructed with the center of the geometric simulation model as the axis, and then the surface geometric morphology details of the original geometric simulation model M0 are reconstructed with the newly created axis as the scanning path. And reversely reconstruct the geometric simulation model of step two to obtain the simulation model M1;

[0106] Step 4: Update the model material property information. Use the inserted welded structure specimen in step 1 to conduct fatigue tests based on the group method and lifting method to obtain the fatigue limit and draw the PSN curve. Use the test results to update the material property information of the simulation model M1 in step 3. Since the model parameters only use the model library data when M0 is initially modeled, most of its performance parameters, including fatigue limit, PSN curve and other key data, are general material-level data, and there is no more realistic data at the structural level that considers the geometric configuration to support it. After updating the parameters in this step, the effectiveness of the simulation model M1 will be greatly improved.

[0107] Step 5: Welding fusion line measurement. Scan the fracture morphology of the sample after the step 4 test. First, use SEM and other fracture analysis techniques to obtain the morphology of the welding fracture area. Use the original design sample center as the reference to determine the center point of the sample fracture section. Draw multiple reference lines passing through the center point of the fracture section. Along the reference line, measure the angle of the point where the fusion line curvature suddenly changes from the reference line. The radial distance from the point to the center point of the cross section is used as the welding depth. When encountering multiple inflection points on the fusion line, it is necessary to take points at similar positions and count the radial distances from the mutation point to the center point of the cross section. After the measurement is completed, the data points that depict the contour of the fusion line of a single sample are obtained. The results are shown in Figure 7 Observe the fracture scan, take the line between the crack initiation position and the reference origin as the reference line for angle measurement, take points in the clockwise direction, and determine the initial angle between the radial position corresponding to the deepest part of the welding pit and the crack initiation position.

[0108] Step 6: Reconstruct the simulation model. Introduce the fusion line described in step 5 into the simulation model M1 described in step 3 to complete the reconstruction modeling of the welding fusion line in the simulation model. First, select 3 points on the fusion line as reference points to establish a reference plane. Use the external welding defect depth at the radial maximum position to define the axial position of the introduced fusion line. The external welding defect depth at the radial maximum depth defines the circumferential position of the fusion line starting point. Input the coordinates of the feature points extracted on the fusion line into the three-dimensional modeling software to obtain the corresponding feature point positions. Use Bezier spline curves to connect the feature points, perform interpolation processing between the two points apart, and finally achieve the reproduction of the welding fusion line in the model to obtain the simulation model M, and realize the characterization of the uneven and discontinuous state of the real welding structure. Then divide the model, eliminate hard edges and hard points, set appropriate load constraints, and complete the construction of the simulation model.

[0109] The analysis was carried out based on the simulation model with the same load as the physical specimen, and the results are shown in Figure 8 As shown in the figure, the stress concentration area and macroscopic failure form are consistent with the actual object, indicating that the simulation model constructed by this method is effective and can be used for failure mechanism analysis of welded structures.

[0110] 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 simulation modeling method for insert welding structure considering welding discontinuity and non-uniformity, characterized in that: include: Step 1: Insertion welding structure specimen design: Based on the state of the actual insertion welding structure, combined with the test analysis requirements, based on the model test idea, complete the design of the equivalent test piece of the insertion welding structure, and obtain the insertion welding structure specimen; Step 2: Construction of the geometric model of the inserted welded structure: Based on the geometric structure dimensions and material property information of the equivalent test piece in step 1, a preliminary geometric simulation model of the inserted welded structure is established M 0; Step 3: Obtaining the external morphology of the weld: In step 1, insert the welded structure specimen entity to perform external morphology scanning, capture the weld geometry details, and reversely reconstruct the geometric simulation model of step 2. M 0, get the simulation model M 1; Step 4: Update model material property information: Use the inserted welded structure specimen in step 1 to conduct fatigue tests based on the group method and lift method, obtain the fatigue limit and draw the PSN curve, and use the test results to update the simulation model in step 3. M 1. Update the material property information; Step 5: Welding fusion line measurement: Scan the fracture morphology of the sample after the test in step 4, identify the welding fusion line of the sample, and complete the welding fusion line data measurement; Step 6: Simulation model reconstruction; introduce the fusion line in step 5 into the simulation model in step 3 M 1. Complete the reconstruction modeling of the welding fusion line in the simulation model to obtain the simulation model M , to represent the uneven and discontinuous state of the real welding structure; then divide the model, eliminate hard edges and hard points, set load constraints, and complete the construction of the simulation model.

2. The insertion welding structure simulation modeling method considering welding discontinuity and non-uniformity according to claim 1 is characterized in that: The model test in step one is a technology that simplifies, reduces or expands the external influences of the geometric morphology, load and action time of a physical phenomenon according to research needs, but ensures that its physical essence remains unchanged; the equivalent test piece design in step one refers to the design activity carried out considering that the size or shape of the inserted welded structure prototype is not easy to meet the actual needs of the test. The test includes installation, loading and clamping. The size or shape of the equivalent test piece here is different from the prototype structure, but its failure behavior and action mechanism are consistent with the prototype structure.

3. The insertion welding structure simulation modeling method considering welding discontinuity and non-uniformity according to claim 1 is characterized in that: The external morphology scanning in step three refers to the process of using a device with the ability to insert a three-dimensional scanning of the welded structure morphology to obtain surface geometric morphology detail data of the welded part of the specimen with a certain accuracy.

4. The insertion welding structure simulation modeling method considering welding discontinuity and non-uniformity according to claim 1 is characterized in that: The reverse reconstruction in step 3 refers to correcting the original geometric simulation model in step 2 based on the detailed geometric morphology data of the solid surface of the welding part obtained by external morphology scanning. M 0 process, which does not affect the original geometric simulation model M The original properties of the material are 0.

5. The insertion welding structure simulation modeling method considering welding discontinuity and non-uniformity according to claim 4 is characterized in that: The reverse reconstruction process includes two steps: first, the axis of the 3D scanning model does not coincide with the axis of the original geometric simulation model, so the center axis of the geometric simulation model needs to be used as the axis to reconstruct the center axis of the scanned geometric details; second, the newly created axis is used as the scanning path to reconstruct and supplement the original geometric simulation model. M 0 surface geometry details.

6. The insertion welding structure simulation modeling method considering welding discontinuity and non-uniformity according to claim 1 is characterized in that: The lifting and lowering method in step 4 refers to a method for determining the fatigue limit at a specified number of cycles, and its steps are: a. First, use a single-point test to test the fatigue strength of the sample, that is, use different stress levels to test a sample, and the test stress level gradually decreases from high to low. S i > S i+1 >…> S i+n , at the specified number of cycles n Within the range, the sample is i Level stress S i If the damage occurs under the action of S i+1 If the sample is in the i+k Level stress S i+k If the damage occurs under the action of S i+k-1 ; b. If the sample is in i Level stress S i Under the action of i +1 level stress S i+1 If damage occurs under the action of S i and S i+1 If the two stress differences S i - S i+1 Very small, smaller than S i and S i+1 5%, then take S i and S i+1 The average value of is approximately taken as the fatigue strength limit, that is S i * =1 / 2( S i + S i+1 ); c. S i and S i+1 The data are regarded as a pair of data with opposite test results. The above test process is repeated. S i * Will appear randomly, with at least n * For data, n ≥6, then the median fatigue strength estimate is .

7. The insertion welding structure simulation modeling method considering welding discontinuity and non-uniformity according to claim 1 is characterized in that: The group method in step 4 refers to a method for determining the median fatigue life or safe fatigue life based on the test results of a group of specimens at a specified stress or strain level.

8. The insertion welding structure simulation modeling method considering welding discontinuity and non-uniformity according to claim 1 is characterized in that: The PSN curve in step 4 refers to a material property that reflects the key welding fatigue strength of the sample. It is a curve fitted by the measured fatigue strength and fatigue limit data points. The PSN curve is obtained based on the welded structure-level sample.

9. The insertion welding structure simulation modeling method considering welding discontinuity and non-uniformity according to claim 1 is characterized in that: The welding fusion line in step 5 refers to the critical line between the welding hot melting area and the unmelted base material area, which represents the interface of the non-uniform and discontinuous state area of ​​the real welding structure; The weld fusion line analysis in step 5 mainly refers to the process of obtaining the quantitative data of the weld fusion line. Its main steps are: a. First, obtain the morphology of the welding fracture area through SEM and other fracture analysis techniques; b. The center point of the fracture section of the specimen is determined based on the center of the original design specimen; c. Draw multiple reference lines passing through the center point of the fracture section. Along the reference lines, measure the angle of the point where the curvature of the fusion line suddenly changes from the reference line. The radial distance from the point to the center point of the cross section is used as the welding depth. When encountering multiple inflection points on the fusion line, it is necessary to take points at similar positions. The cross section measurement position should be no less than 8 points. d. Calibrate the scale according to the scale of the fracture scan image, take the average value as the measurement scale after multiple calibrations, and count the radial distance from the mutation point to the center line of the cross section; e. After the measurement is completed, the data points depicting the fusion line contour of a single sample are obtained; the fracture scan is observed to determine the location of the crack initiation, and the line connecting the crack initiation location and the reference origin is used as the reference line for angle measurement. Points are taken in the clockwise direction, and the contour of the fracture scan is compared with the contour of the pattern entity scan. The initial angle between the radial position corresponding to the deepest part of the welding pit and the crack initiation location is determined so that the subsequent modeling can obtain the correct fusion line location.

10. The insertion welding structure simulation modeling method considering welding discontinuity and non-uniformity according to claim 1, characterized in that: The welding fusion line reconstruction modeling in step 6 refers to the process of introducing the welding fusion line into the model according to the welding fusion line measurement results. The steps are as follows: a. Select three points on the fusion line as reference points to establish a reference plane; b. Use the maximum radial value of the external welding defect depth to define the axial position of the introduced fusion line, and the maximum radial value of the external welding defect depth to define the circumferential position of the fusion line starting point. Input the coordinates of the feature points extracted from the fusion line into the 3D modeling software to obtain the corresponding feature point positions; c. Use Bezier spline curves to connect the feature points, perform interpolation between two separated points, and finally reproduce the welding fusion line in the model.

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