A simulation method for welding structure

Abstract

The present invention discloses a simulation method of a welding structure, including establishing a simulation model of the welding structure according to the actual size in a simulation system; the welding structure at least includes a first weldment, a second weldment and a welding joint, and the first weldment and the second weldment are connected integrally at the welding joint; the welding joint is close to one side of the weldment, and is defined as a tempering layer and a heat-affected layer from the outside to the inside; the area between the two heat-affected layers of the welding joint is defined as a weld body; the material mechanical properties of the weld body, the heat-affected layer and the tempering layer are defined respectively, and meshing is performed; the contact type between the weldment and the welding joint and the contact type between the weldment and the weldment are defined, and the contact type between the weldment and the welding joint is defined as a common node; finally, mechanical simulation is performed on the simulation model of the welding structure. The weld connection can be simulated well, and the real organizational structure and stress condition of the welding joint are reflected.

Description

Technical Field

[0001] The invention relates to the technical field of welding, and in particular to a simulation method for a welding structure. Background Art

[0002] Compared with other connection methods, welding is a connection method with extremely high strength and excellent sealing. However, in the simulation analysis process, due to the complexity of weld morphology, structure and organizational performance, most simulation engineers currently define the contact mode of two parts connected by welds as binding contact. However, for welding, this definition is one-sided and cannot simulate the geometric structure and stress conditions of weld connections well, thus reducing the accuracy of simulation. In this case, some industry insiders began to seek more practical and less computationally demanding weld simulation methods. However, these methods are only based on the model and cannot well reflect the real organizational structure and stress conditions of welded joints. Summary of the invention

[0003] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a simulation method for a welding structure. Starting from the organizational structure of the welding joint, the structure and performance of the actual welding joint are reasonably optimized or simplified, the welding joint is more finely divided, a simulation model of the welding structure is established, the mechanical properties of the material are defined, and then the mechanics of the welding structure are simulated.

[0004] Technical solution: To achieve the above-mentioned purpose, a simulation method of a welding structure of the present invention includes establishing a simulation model of the welding structure according to the actual size in a simulation system; the welding structure includes at least a first weldment, a second weldment and a welding joint, and the first weldment and the second weldment are integrally connected at the welding joint; the welding joint is close to the first weldment, and is defined as a tempering layer and a heat-affected layer from the outside to the inside, and the welding joint is close to the second weldment, and is also defined as a tempering layer and a heat-affected layer from the outside to the inside; the weld body is defined between the two heat-affected layers of the welding joint.

[0005] Furthermore, the material mechanical properties of the weld body, heat affected layer and tempering layer are defined respectively; the weld body, heat affected layer and tempering layer are meshed; the contact type between the weldment and the weld joint and the contact type between the weldments are defined, and the contact type between the weldment and the weld joint is defined as a common node; finally, the simulation model of the welding structure is subjected to mechanical simulation.

[0006] Furthermore, when a simulation model of a welding structure is established, the first weldment and the second weldment are not in contact, and the cross-section of the welding joint is rectangular; the heat-affected layers on both sides of the weld body are respectively defined as a first heat-affected zone and a second heat-affected zone, and the side of the first heat-affected zone away from the weld body is defined as a first tempering zone, and the side of the second heat-affected zone away from the weld body is defined as a second tempering zone; the boundary lines between the first heat-affected zone and the second heat-affected zone and the weld body are respectively defined as a first boundary line and a second boundary line, and the middle parts of the first boundary line and the second boundary line are both convex toward the central axis of the weld body.

[0007] Furthermore, the first heat affected zone and the first tempering zone are defined as a third boundary line, the second heat affected zone and the second tempering zone are defined as a fourth boundary line, and the middle parts of the third boundary line and the fourth boundary line are both convex toward the central axis of the weld body.

[0008] Furthermore, the symmetry line of the first boundary line and the second boundary line coincides with each other, and the symmetry line is perpendicular to the central axis.

[0009] Furthermore, the heat affected layer between the first boundary line and the third boundary line gradually becomes thinner toward both ends based on the symmetry line; the heat affected layer between the second boundary line and the fourth boundary line gradually becomes thinner toward both ends based on the symmetry line.

[0010] Furthermore, the boundary line between the first tempering zone and the first weldment is defined as a fifth boundary line, and the boundary line between the second tempering zone and the second weldment is defined as a sixth boundary line, and the fifth boundary line and the sixth boundary line are parallel to the central axis of the weld body.

[0011] Further, when the first weldment and the second weldment of the simulation model of the welding structure are in contact, and the contact position of the first weldment and the second weldment forms a linear welding filling groove; the welding joint is filled in the linear welding filling groove;

[0012] In the cross section of any point of the welding joint, a layer of the welding joint attached to the inner wall of the linear welding filling groove is defined as a tempering layer, the inner side of the tempering layer is defined as a heat-affected layer, the inner side of the heat-affected layer is defined as a weld body, the heat-affected layer semi-surrounds the weld body, and the heat-affected layer is located between the weld body and the tempering layer.

[0013] Beneficial effects: The simulation method of a welding structure of the present invention divides the welding structure more finely, can better simulate the geometric structure of the weld connection, and reflect the actual organizational structure and stress conditions of the weld; at the same time, the simulation method of the welding structure of this scheme overcomes the problem that the definition of welding contact in the simulation field can only rely on experience or geometric verification through results, and the verification result has a large error with the actual situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Attached Figure 1 Schematic diagram of the division of welding joint structure;

[0015] Attached Figure 2 Actual schematic diagram of the welded joint structure;

[0016] Attached Figure 3 Schematic diagram of a triangular flat weld joint;

[0017] Attached Figure 4 Schematic diagram of the weld joint of fillet weld;

[0018] Attached Figure 5 Schematic diagram of a rectangular flat weld joint;

[0019] Attached Figure 6 Schematic diagram of a Y-shaped welding joint;

[0020] Attached Figure 7 Schematic diagram of stress and strain for single linear material calculation;

[0021] Attached Figure 8 Schematic diagram of stress and strain in bilinear material calculation;

[0022] Attached Fig. 9 Schematic diagram of stress and strain for multilinear material calculations. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings.

[0024] As attached Figure 1 As shown, a simulation method of a welding structure of the present invention,

[0025] A simulation method for a welding structure of the present invention comprises establishing a simulation model of the welding structure according to actual size in a simulation system; the welding structure comprises at least a first welding part 4, a second welding part 5 and a welding joint 6, wherein the first welding part 4 and the second welding part 5 are integrally connected at the welding joint 6; the side of the welding joint 6 close to the first welding part 4 is defined as a tempering layer 3 and a heat-affected layer 2 from the outside to the inside, and the side of the welding joint 6 close to the second welding part (5) is also defined as a tempering layer 3 and a heat-affected layer 2 from the outside to the inside; and the area between the two heat-affected layers 2 of the welding joint 6 is defined as a weld body 1.

[0026] The welding joint 6 is the area where the contact position of the two welds is re-solidified after being melted at high temperature. The heat-affected zone is the area where the microstructure of the base material of the weld undergoes phase change when heated, that is, the heat-affected layer 2; under specific materials and welding methods, there may be a tempering softening zone between the weld and the heat-affected zone. Although the microstructure of the tempering softening zone has not undergone phase change, due to microscopic geometric defects or changes in specific elements under high temperature conditions, the mechanical properties of the area have undergone corresponding changes. This area is called the tempering softening zone, abbreviated as the tempering zone, that is, the tempering layer 3.

[0027] When establishing a simulation model of a welded structure, first clarify the purpose of the simulation and preliminarily analyze the stress conditions of the weld structure, and select an appropriate simulation analysis method based on the simulation purpose and the preliminary analysis of the weld stress conditions; for example, when the simulation purpose is to test whether the product exceeds the fatigue allowable stress under a specific fatigue load, the welding model can use a quadrilateral weld with lower precision, a hexagonal mesh for meshing, and a linear material for material settings; when the simulation purpose is to study the stress distribution inside a fillet weld under collision conditions, the welding model can use a weld model with a heat-affected zone and a tempering zone, a tetrahedral mesh for meshing, and an elastoplastic material for material settings.

[0028] As attached Figure 1-2 As shown, when a simulation model of a welding structure is established, the first weldment 4 and the second weldment 5 are not in contact, and the cross-section of the welding joint 6 is rectangular; the heat-affected layers 2 on both sides of the weld body 1 are respectively defined as a first heat-affected zone 21 and a second heat-affected zone 22, and the side of the first heat-affected zone 21 away from the weld body 1 is defined as a first tempering zone 31, and the side of the second heat-affected zone 22 away from the weld body 1 is defined as a second tempering zone 32; the boundaries between the first heat-affected zone 21 and the second heat-affected zone 22 and the weld body 1 are respectively defined as a first boundary line 11 and a second boundary line 12, and the middle parts of the first boundary line 11 and the second boundary line 12 are both convex toward the central axis 9 of the weld body 1.

[0029] As attached Figure 6 As shown, the first weldment 4 and the second weldment 5 are not in contact, and the cross section of the weld joint 6 is not a rectangle, but a shape that is wide at the top and narrow at the bottom, similar to a Y shape. The specific structure of the weld joint 6 is shown in the attached Figure 6 As shown in the attached Figure 6 The area division of the weld joint shown is similar to the area division of the weld joint 6 with a rectangular cross-section; the heat-affected layer 2 on both sides of the weld body 1 is defined as a first heat-affected zone 21 and a second heat-affected zone 22, respectively, the side of the first heat-affected zone 21 away from the weld body 1 is defined as a first tempering zone 31, and the side of the second heat-affected zone 32 away from the weld body 1 is defined as a second tempering zone 32.

[0030] The first heat-affected zone 21 and the first tempering zone 31 are defined as the third boundary line 13, the second heat-affected zone 22 and the second tempering zone 32 are defined as the fourth boundary line 14, and the middle parts of the third boundary line 13 and the fourth boundary line 14 are both convex to the central axis 9 of the weld body 1. The boundary line between the first tempering zone 31 and the first weldment 4 is defined as the fifth boundary line 15, and the boundary line between the second tempering zone 32 and the second weldment 5 is defined as the sixth boundary line 16, and the fifth boundary line 15 and the sixth boundary line 16 are parallel to the central axis 9 of the weld body 1.

[0031] The symmetry line 8 of the first junction line 11 and the second junction line 12 coincides, and the symmetry line 8 is perpendicular to the central axis 9. The heat-affected layer between the first junction line 11 and the third junction line 13 gradually becomes thinner toward both ends based on the symmetry line 8; the heat-affected layer between the second junction line 12 and the fourth junction line 14 gradually becomes thinner toward both ends based on the symmetry line 8.

[0032] The width of the first heat affected zone 21 and the second heat affected zone 22 at the position of the symmetry line 8 is defined as A, and the width of the first heat affected zone 21 and the second heat affected zone 22 at both ends based on the symmetry line 8 is defined as B; generally, the relationship between the width A and the width B is: 1.2B<A≤2B.

[0033] During the welding process, the heat affected zone and the weld body 1 are based on the symmetry line 8, and the width of the central part of the heat affected layer 2 is wider than the width at both ends. This is mainly because the heat dissipation of the middle part after welding is completed is transmitted to the weldments on both sides and the two end parts of the weld body 1, causing the middle part of the heat affected layer 2 to become wider and the two end parts of the heat affected layer 2 to become narrower.

[0034] The width of the weld body 1 is defined as a, the width of the first heat affected zone 2 and the second heat affected zone 3 is defined as b, and the width of the first tempering zone 4 and the second tempering zone 5 is defined as c; the relationship between the width a of the weld body 1 and the width b of the first heat affected zone 2 and the second heat affected zone 3 and the width c of the first tempering zone 4 and the second tempering zone 5 is: in general, a is approximately equal to 4b, and a is approximately equal to 2c; however, the width of the weld body 1, the width of the heat affected layer 2 and the tempering layer 3 will affect the width of each area of ​​the weld joint 6 due to the welding method, welding angle, welding parameters, the groove form of the welding place, and the material of the base material or welding wire; even the width of each area will be affected by the different ambient temperatures; therefore, the specific settings of the width of the weld body 1, the width of the heat affected layer 2 and the width of the tempering layer 3 need to be based on the actual welding situation.

[0035] As attached Figure 3-5As shown, when the first weldment 4 and the second weldment 5 of the simulation model of the welding structure are in contact, and the contact position of the first weldment 4 and the second weldment 5 forms a linear welding filling groove 7; the welding joint 6 is filled in the linear welding filling groove 7;

[0036] In the cross section of any point of the welding joint 6, a layer of the welding joint 6 attached to the inner wall of the linear welding filling groove 7 is defined as a tempering layer 3, the inner side of the tempering layer 3 is defined as a heat-affected layer 2, the inner side of the heat-affected layer 2 is defined as a weld body 1, the heat-affected layer 2 semi-surrounds the weld body 1, and the heat-affected zone 2 is located between the weld body 1 and the tempering layer 3.

[0037] As attached Figure 3-5 As shown in the figure, when establishing the simulation model of the welded structure, the general welds can be divided into flat welds and fillet welds; the weld joints 6 of the fillet welds are shown in the attached figure. Figure 4 As shown in the figure, the flat weld during simulation can be divided into rectangular flat weld and triangular flat weld according to the shape of the weld joint; the weld joint 6 of the rectangular flat weld is shown in the figure. Figure 5 As shown, the welded joint 6 of the triangular flat weld is as shown in the attached Figure 3 As shown in the figure, the shape of the simulated weld joint is selected according to the shape of the weld structure and the preliminary analysis of the weld stress. When the weld joint is rectangular, its advantage is that it is easy to calculate quickly and has low hardware requirements; when the weld joint is triangular, its advantage is that it has a wide range of applications and is more accurate in simulating incomplete welds; and the shape of a fully penetrated weld is closer to a quadrilateral.

[0038] The density of the weld joint 6 will not be much different from that of the weldment, but due to the composition of the weldment, welding wire, and the different forming processes, the tensile, hardness, impact and other mechanical properties of the weld joint 6 area deviate greatly from the performance parameters of the weldment. At this time, it is necessary to investigate and input the performance parameters of the weld joint 6 area by yourself.

[0039] In mechanical simulation, except for Poisson's ratio, the most important properties can generally be reflected in the stress-strain curve after stretching; for welds, the Poisson's ratio of metal materials is generally around 0.3, for example, the Poisson's ratio of steel is set to 0.30, and the Poisson's ratio of aluminum is set to 0.33.

[0040] Define the material mechanical properties of the weld body 1, heat affected layer 2 and tempered layer 3 respectively; obtain the stress-strain curves of the weldment, weld body 1, heat affected layer 2 and tempered layer 3. Strictly speaking, the true stress-strain curve needs to be input. The engineering stress-strain curve can be used for conversion or replacement. Whether to replace depends on the simulation accuracy. The conversion of engineering stress to true stress is:

[0041] σ True =σ Eng (ε Eng +1)

[0042] In the formula, σ True is the true stress, σ Eng is the engineering stress;

[0043] The engineering strain can be converted into true strain as follows:

[0044]

[0045] In the formula, ε True is the true strain, ε Eng Engineering strain.

[0046] and defining the material properties of the weldment, the weld body 1, the heat-affected layer 2 and the tempering layer 3; the material properties are divided into single-linear material, double-linear material and multi-linear material;

[0047] When the stress on the weldment, weld body 1, heat affected layer 2 or tempered layer 3 exceeds the yield strength, or when verifying whether the weld area exceeds its yield strength, it is defined as a single linear material; the material elastic modulus is calculated based on the stress-strain curve, and the density and Poisson's ratio are used as input material properties; after being defined as a single linear material, only elastic deformation needs to be considered, and plastic deformation does not need to be considered. When doing mechanical analysis, the material characteristic parameters that need to be input are only density, elastic modulus and Poisson's ratio; the material elastic modulus is:

[0048]

[0049] Where Δy1 is Figure 7 The change in elastic modulus engineering stress, Δx1, is Figure 7 The change in engineering strain of the elastic modulus;

[0050] When the stress on the weldment, weld body 1, heat affected layer 2 or tempered layer 3 exceeds the yield strength, it is defined as a bilinear material or a multilinear material. Compared with multilinear materials, bilinear materials have faster calculation speed but lower accuracy.

[0051] When defined as a bilinear material, the material elastic modulus and material tangent modulus are calculated based on the stress-strain curve, and the density, Poisson's ratio, yield strength and tensile strength are used as input material properties; the material elastic modulus is:

[0052]

[0053] Where Δy1 is Figure 7 The change in elastic modulus engineering stress, Δx1, is Figure 7 The change in engineering strain of the elastic modulus;

[0054] The material tangent modulus is:

[0055]

[0056] Where Δy2 is Figure 8 The change in the engineering stress of the tangent modulus, Δx2, is Figure 8 The change in engineering strain of the tangent modulus;

[0057] Yield strength is the strength of a material when it changes from elastic deformation to plastic deformation, and tensile strength is the maximum strength a material can withstand during stretching.

[0058] When defined as a multilinear material, the coordinates of no less than 8 points on the stress-strain curve are used as the input material properties together with the density and Poisson's ratio. Generally speaking, there are thousands of stress-strain data points after a tensile test. When all these data are input, the amount of computer calculation will be greatly increased. Therefore, the curve can be optimized and fitted. The position and number of the points are defined by the user. Fig. 9 As shown in the figure, in the mechanical properties simulation, it is only necessary to Fig. 9 The eight coordinate points (x0,y0), (x1,y1), (x2,y2), (x3,y3), (x4,y4), (x5,y5), (x6,y6), (x7,y7), and (x8,y8) can be input to satisfy the calculation.

[0059] The weld body 1, heat affected layer 2 and tempering layer 3 are meshed; the mesh type and size are selected according to the shape and accuracy requirements of the weld joint 6. The mesh types of the weld joint 6 are divided into tetrahedral mesh and hexahedral network. The tetrahedral mesh has a slow calculation speed, but is suitable for all structures. The hexahedral mesh has a fast calculation speed, but the structure is relatively simple to use. The hexahedral mesh must be a square welding structure without curved surfaces; generally, a quadrilateral weld is defined as a hexahedral structure, and a triangular weld and a composite weld of a triangle and a quadrilateral are defined as a tetrahedral structure.

[0060] The mesh size determines the accuracy and resolution of the calculation results. The smaller the mesh size, the higher the accuracy and resolution of the calculation results, and the slower the calculation speed. The mesh size of the welding joint can be adjusted according to needs.

[0061] The contact type between the weldment and the welding joint 6 and the contact type between the weldments are defined. The contact type between the weldment and the welding joint 6 is defined as a common node; and the contact between the weldments can be defined according to actual conditions; finally, a mechanical simulation is performed on the simulation model of the welding structure.

[0062] Example

[0063] Due to the differences in welding methods, welding parameters, welding materials, and welding groove forms, the size of the weld is also different; for example: for a 3mm thick steel plate that is welded by laser welding without filler wire and without a groove, the weld model generally uses a quadrilateral weld model with a width of 1mm and a depth of 3mm (full penetration weld); for a 3mm thick aluminum plate that is welded by CMT fillet welding without a groove, the weld model generally uses a triangular weld model with a right angle of 3.5mm; for a 20mm thick stainless steel plate that is welded by argon arc welding with a groove angle of 45° and a Y-shaped groove with a blunt edge of 5mm, the weld model will use a combination of a quadrilateral and a triangle, as shown in the attached figure. Figure 6 shown.

[0064] The above is only a description of the preferred embodiments of the present invention. Ordinary technicians in this technical field can make several modifications and optimizations based on the above disclosure without departing from the above basic principles. These improvements and optimizations should be regarded as the understood protection scope of the present invention.

Claims

1. A simulation method for a welding structure, characterized in that: The method comprises establishing a simulation model of a welding structure according to actual size in a simulation system; the welding structure comprises at least a first welding part (4), a second welding part (5) and a welding joint (6); the first welding part (4) and the second welding part (5) are integrally connected at a welding joint (6); a side of the welding joint (6) close to the first welding part (4) is defined as a tempering layer (3) and a heat-affected layer (2) from the outside to the inside, and a side of the welding joint (6) close to the second welding part (5) is also defined as a tempering layer (3) and a heat-affected layer (2) from the outside to the inside; and a portion between the two heat-affected layers (2) of the welding joint (6) is defined as a weld body (1); The material mechanical properties of the weld body (1), the heat-affected layer (2) and the tempered layer (3) are defined respectively; the weld body (1), the heat-affected layer (2) and the tempered layer (3) are meshed; the contact type between the weldment and the weld joint (6) and the contact type between the weldments are defined, and the contact type between the weldment and the weld joint (6) is defined as a common node; and finally, a mechanical simulation is performed on the simulation model of the welded structure; When a simulation model of a welding structure is established, the first weldment (4) and the second weldment (5) are not in contact, and the cross-section of the welding joint (6) is rectangular; the heat-affected layers (2) on both sides of the weld body (1) are respectively defined as a first heat-affected zone (21) and a second heat-affected zone (22); the side of the first heat-affected zone (21) away from the weld body (1) is defined as a first tempering zone (31); the side of the second heat-affected zone (22) away from the weld body (1) is defined as a second tempering zone (32); the boundary lines between the first heat-affected zone (21) and the second heat-affected zone (22) and the weld body (1) are respectively defined as a first boundary line (11) and a second boundary line (12); the middle parts of the first boundary line (11) and the second boundary line (12) are both convex toward the central axis (9) of the weld body (1); When a first weldment (4) and a second weldment (5) for establishing a simulation model of a welding structure are in contact, and the contact positions of the first weldment (4) and the second weldment (5) form a linear welding filling groove (7); the welding joint (6) is filled in the linear welding filling groove (7); In a cross section at any point of the weld joint (6), a layer of the weld joint (6) attached to the inner wall of the linear weld filling groove (7) is defined as a tempering layer (3), the inner side of the tempering layer (3) is defined as a heat-affected layer (2), the inner side of the heat-affected layer (2) is defined as a weld body (1), the heat-affected layer (2) semi-surrounds the weld body (1), and the heat-affected layer (2) is located between the weld body (1) and the tempering layer (3).

2. The method for simulating a welding structure according to claim 1, characterized in that: The first heat affected zone (21) and the first tempering zone (31) are defined as a third boundary line (13), the second heat affected zone (22) and the second tempering zone (32) are defined as a fourth boundary line (14), and the middle parts of the third boundary line (13) and the fourth boundary line (14) are both convex toward the central axis (9) of the weld body (1).

3. The simulation method of a welding structure according to claim 2, characterized in that: The symmetry line (8) of the first boundary line (11) and the second boundary line (12) coincide with each other, and the symmetry line (8) and the central axis (9) are perpendicular to each other.

4. The simulation method of a welding structure according to claim 3, characterized in that: The heat-affected layer between the first boundary line (11) and the third boundary line (13) is based on the symmetry line (8) and gradually becomes thinner towards both ends; the heat-affected layer between the second boundary line (12) and the fourth boundary line (14) is based on the symmetry line (8) and gradually becomes thinner towards both ends.

5. The simulation method of a welding structure according to claim 1, characterized in that: The boundary line between the first tempering zone (31) and the first weld (4) is defined as a fifth boundary line (15), and the boundary line between the second tempering zone (32) and the second weld (5) is defined as a sixth boundary line (16), and the fifth boundary line (15) and the sixth boundary line (16) are parallel to the central axis (9) of the weld body (1).

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