Low-matching butt joint shape design method and device based on equal-stretch-bending composite bearing

Abstract

The invention provides a low-matching butt joint shape design method and device based on equal stretch-bending composite bearing, and belongs to the technical field of welding structure design. The method comprises the steps that the stretch-bending load ratio is determined; determining the yield strength matching ratio of the weld joint to the base metal; calculating a minimum reinforcement curve of a weld zone, and distinguishing whether a structure end is subjected to rotation constraint or not; calculating the minimum weld width of a weld joint, and distinguishing structural end constraint forms; determining the radius of a transition arc at a weld toe by adopting a three-circle tangency method; determining the total weld width of the weld; and according to the minimum excess weld metal curve and the total weld width, the shape of the weld joint and geometric parameter values thereof are obtained. The low-matching butt joint shape design method based on equal-stretch-bending composite load is specifically applied to equal-load design of the low-matching butt joint under the action of the stretch-bending composite load, and is suitable for structural strength design of a welding joint.

Description

Technical Field

[0001] This invention belongs to the field of welding structure design technology, specifically relating to the technical field of equal load-bearing design of low-matching butt joints under combined tensile and bending loads, and is used for the structural strength design of welded joints. Background Technology

[0002] With societal progress, high-strength steel, due to its high strength, has been widely used in various industries. However, its poor ductility and toughness also result in a significant tendency for cold cracking, especially after welding. Welding generally adopts the principle of equal strength, meaning the welding material used is of equal strength to the base metal. However, this equal strength leads to poor weldability, severe cold cracking tendency in the weld, softening and embrittlement of the heat-affected zone, and insufficient weld toughness reserve. Existing low-matching welded joints for high-strength steel are mainly designed for single-load conditions such as compressive or bending loads. However, actual high-strength steel butt joints often bear complex loads, making single-load conditions insufficient for practical applications. Existing low-matching equal-load-bearing welded joint conditions are derived under single-load conditions, and their criteria are primarily applicable to tensile or bending loads. Existing inventions yield high-strength steel welded joints with equal load-bearing capacity that exhibit parabolic weld shape parameters under single load conditions. Furthermore, the weld toe at the interface between the weld and the base metal lacks a smooth transition, resulting in excessively dense stress concentration curves at this point. Although the overall load-bearing capacity of the weld meets welding standards, the weld toe remains in a critical zone, posing a potential safety hazard. To avoid these issues, we design welded materials with lower strength but better plasticity and toughness than the base metal, effectively reducing the tendency for cold cracking in high-strength steel after welding. However, the load-bearing capacity of low-matching joints does not match that of the base metal, hindering their widespread application. Therefore, improving the equal load-bearing design of low-matching welded joints to ensure their failure in practical applications is a pressing problem.

[0003] The traditional method to solve the above problems is to use welding materials with equal strength, and to perform preheating and post-weld heat treatment to reduce the tendency of cold cracking and improve the toughness of the weld. However, these methods increase the amount of time required and production costs. Furthermore, if the workpiece is too large or too complex, preheating and post-weld heat treatment are not suitable, which can lead to problems in the high-strength steel equal-strength weld.

[0004] Using low-matching welding materials with high plasticity and toughness for high-strength steel welding is a commonly used method today. This involves selecting welding filler materials with lower strength than the base metal but higher plasticity and toughness for high-strength steel welding. This reduces the preheating temperature or even eliminates the need for preheating, while also reducing the tendency for cold cracking and improving weld toughness. Because low-matching welded joints have low load-bearing capacity and do not meet the strength requirements of the base metal, the most common approach is to design the weld joint's reinforcement height and weld width geometrically, while simultaneously reducing stress concentration in critical areas of the joint to meet the strength requirements. To date, modeling designs for low-matching joint shapes in compressive load structures and bending load structures have been developed, but modeling designs for low-matching joint shapes under combined tension and bending loads have not yet been achieved. Summary of the Invention

[0005] The present invention aims to solve the technical problem of insufficient load-bearing capacity of low-matching butt joints under combined tensile and bending loads.

[0006] This invention proposes a method for designing the shape of low-matching butt joints based on equal tension-bending composite load-bearing capacity, the method comprising: S1. Determine the tension-bending load ratio; S2. Determine the yield strength matching ratio between the weld and the base metal; S3. Calculate the minimum excess height curve of the weld zone to distinguish whether the structural end is subject to rotational constraints; S4. Calculate the minimum weld width and distinguish the structural end constraint type; S5. The radius of the transition arc at the weld toe is determined using the three-circle tangency method; S6. Determine the total weld width; S7. Based on the minimum excess height curve and the total weld width, obtain the weld shape and its geometric parameter values.

[0007] Furthermore, the process in S1 involves applying a tensile load F... N With bending load F M In comparison, the tensile-bending load ratio n is obtained as follows: .

[0008] Furthermore, the S2 process involves increasing the yield strength R of the base metal. e H b Yield strength R of weld metal e H w In comparison, the yield strength matching ratio between the weld and the base metal was obtained. as follows: .

[0009] Furthermore, the S3 process includes: setting selection conditions, and determining the calculation formula for the minimum weld reinforcement curve based on the selection conditions, including: Minimum residual height curve type one: , Minimum residual height curve type two: .

[0010] Furthermore, the selection criteria are the thickness of the base material (2t), the tensile-bending load ratio (n), the span (l), and the matching ratio. And whether the structural end is subject to rotational constraints; if the structural end is not subject to rotational constraints, then select the minimum excess height curve type one; if the structural end is subject to rotational constraints, then select the minimum excess height curve type two.

[0011] Furthermore, the formula for calculating the minimum weld width described in S4 includes: Minimum weld width, type 1: , Minimum weld width, type two: .

[0012] Furthermore, the selection condition for the weld width curve is whether the structural end is subject to rotational constraints. If the structural end is not subject to rotational constraints, then the minimum weld width formula one is selected; if the structural end is subject to rotational constraints, then the minimum weld width formula two is selected.

[0013] Furthermore, the three-circle tangent method described in S5 uses a circular arc instead of the transition arc radius R at the weld toe. min as follows:

[0014] Furthermore, the total weld width 2w is as follows: .

[0015] This invention also proposes a low-matching butt joint shape design device based on equal tension-bending composite load, the device comprising: The load ratio determination module is used to determine the tension-bending load ratio; The matching ratio calculation module is used to determine the yield strength matching ratio between the weld and the base material; The reinforcement curve calculation module is used to calculate the minimum reinforcement curve of the weld zone and distinguish whether the structural end is subject to rotational constraints. The minimum weld width calculation module is used to calculate the minimum weld width and distinguish the structural end constraint type; The transition arc determination module is used to determine the radius of the transition arc at the weld toe using the three-circle tangency method. The total weld width determination module is used to determine the total weld width. The geometry generation module is used to obtain the weld shape and its geometric parameters based on the minimum excess height curve and the total weld width.

[0016] The beneficial effects of this invention are: The present invention describes a method for designing the shape of a low-matching butt joint based on equal tensile-bending composite load-bearing capacity. This method achieves equal tensile-bending composite load-bearing capacity with the base material by modifying the joint geometry. It enhances the tensile-bending composite load-bearing capacity of the low-matching butt joint, enabling it to reach the tensile-bending composite load-bearing capacity of the base material or an equal-matching joint. This economically and efficiently solves the problems of insufficient weld toughness reserve and susceptibility to cold cracking that occur when welding high-strength steel with equal strength. Ordinary low-strength welding materials can be used, reducing or even eliminating preheating temperature, improving the working environment, and saving production costs.

[0017] This invention, based on existing tensile and bending load equalization designs for low-matching joints, studies the load equalization design for combined tensile and bending loads of low-matching joints. Without considering welding defects, ignoring metallurgical effects and residual stress, the invention designs the combined tensile and bending load equalization of low-matching joints within the elastic range, proposing criteria and conditions for achieving equal load. Based on the stress characteristics of beams subjected to combined tensile and bending loads, this invention provides minimum weld reinforcement height and minimum weld width as prerequisites. Then, using a three-circle tangent method, it optimizes the transition arc at the weld toe of the designed load equalization joint, providing a design criterion for combined tensile and bending load equalization of low-matching butt joints.

[0018] Although the load-bearing capacity of low-strength welds is insufficient, the reinforcement height is used to participate in the load-bearing capacity, adjusting the stress distribution of the weld and preventing it from yielding before the high-strength steel base material. This increases the load-bearing capacity of the weld and allows the welded structure to be designed according to the strength of the high-strength base material. This design reduces the defect of excessively dense stress concentration curves in the weld toe zone, lowers the tendency of the weld to develop cold cracks, and ensures that the load-bearing capacity of the low-matching butt joint is not lower than that of the base material, and its toughness is higher than that of the high-strength steel base material.

[0019] This invention employs low-matching welding materials for high-strength steel butt joints. By adding welding materials, the weld reinforcement and width are increased, achieving a weld with the same strength as the base metal. This improves the weld's ductility and toughness, as well as its overall mechanical properties. High-strength steel butt joints generally follow the principle of equal-strength matching, using welding materials with the same strength as the base metal. Because the welding material strength is the same as the base metal strength, the weld's post-weld strength meets technical requirements. However, due to the high weld strength and rapid cooling after welding, the weld's ductility and toughness are extremely poor. Using low-matching welding materials for high-strength steel welding, where the welding material strength is lower than the base metal strength, results in better ductility and toughness compared to equal-strength matching weld joints. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 This is a flowchart of the low-matching butt joint shape design method based on equal tension and bending composite load as described in this invention.

[0022] Figure 2 This is a schematic diagram of the shape of a load-bearing joint under different matching ratios and combined loads such as bending.

[0023] Figure 3 This is a schematic diagram of the geometry of an X-shaped bevel joint with low-matching tensile-bending composite loads.

[0024] Figure 4 This is a schematic diagram of a three-circle tangent equal-load joint. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Specific implementation method one, combined with Figures 1-4 The present invention provides a method for designing the shape of a low-matching butt joint based on equal tension-bending composite load-bearing capacity. The method includes: S1. Determine the tension-bending load ratio; S2. Determine the yield strength matching ratio between the weld and the base metal; S3. Calculate the minimum excess height curve of the weld zone to distinguish whether the structural end is subject to rotational constraints; S4. Calculate the minimum weld width and distinguish the structural end constraint type; S5. The radius of the transition arc at the weld toe is determined using the three-circle tangency method; S6. Determine the total weld width; S7. Based on the minimum excess height curve and the total weld width, the weld shape and its geometric parameters are obtained.

[0027] The low-matching butt joint shape design method based on equal tension-bending combined load described in this embodiment designs an X-groove low-matching equal-load butt joint under tension-bending combined load according to the equal-load design criterion. Specifically, the joint is designed according to the "equal-load under complex loads" design, satisfying the condition that the stress concentration factor at the bottom center of the weld of the low-matching butt joint is equal to the yield strength matching ratio of the low-matching butt joint, and the stress concentration factor at the weld toe is minimized. Based on this joint design and implementation condition, the geometry of the joint is designed, the influence of the joint geometry parameters on the stress concentration factors at the bottom center of the weld and the weld toe is determined, the joint geometry parameter equation is established, and then the appropriate joint geometry parameters are determined according to different matching ratios and equal-load conditions under complex loads. The core principle of the joint design in this embodiment is that the geometric parameters of the joint can adjust the complex stress and strain distribution inside the joint, reduce the stress concentration in the weak load-bearing areas at the bottom center of the weld and the weld toe, thereby improving the load-bearing capacity of the low-strength weld area. The implementation of the joint design, to a certain extent, allows the weak load-bearing area of ​​the low-matching joint to be transferred from the weld to the base material, so that the welded structure can be designed and implemented according to the strength of the base material.

[0028] In this embodiment, the method begins with step one, in which the tension-bending load ratio is determined. Specifically, for a structure subjected to a combined tension-bending load, the load-bearing requirement is met when the normal stress generated by the structure under the combined action of the tensile and bending loads is not greater than the yield strength of the material. For ease of explanation, this document will refer to the tensile load F as... N With bending load F M The ratio n between the magnitudes of the loads is called the tension-bending load ratio, and the tension-bending load ratio n is as follows: .

[0029] Then proceed to step two, in which the yield strength matching ratio between the weld and the base metal is determined; specifically, the yield strength R of the base metal is determined according to relevant standards. e H b and the yield strength R of the weld metal e H w The yield strength matching ratio between the weld and the base metal is obtained, and different matching ratios are shown in the figure. Figure 1 As shown. The yield strength matching ratio between the weld and the base metal. as follows: .

[0030] Then, proceed to step three. In step three, calculate the minimum reinforcement curve of the weld zone, distinguishing whether the structural end is subject to rotational constraints; set selection conditions, and determine the calculation formula for the minimum reinforcement curve of the weld zone based on the selection conditions, including: Minimum residual height curve type one: , Minimum residual height curve type two: .

[0031] Specifically, based on the thickness of the base material 2t, the tensile-bending load ratio n, the span l, and the matching ratio... Depending on the constraint form of the structure, select the formula for calculating the residual height curve. If the end of the structure is not subject to rotational constraints, calculate according to Formula 1 for the minimum residual height curve; if the end of the structure is subject to rotational constraints, calculate according to Formula 2 for the minimum residual height curve.

[0032] Then proceed to step four, in which the minimum weld width is calculated, distinguishing between structural end constraint types; the formula for calculating the minimum weld width includes: Minimum weld width, type 1: , Minimum weld width, type two: ; The selection condition for the weld width curve is whether the structural end is subject to rotational constraints. If the structural end is not subject to rotational constraints, then the minimum weld width formula one is selected; if the structural end is subject to rotational constraints, then the minimum weld width formula two is selected.

[0033] Then proceed to step five, in which the radius of the transition arc at the weld toe is determined using the three-circle tangency method; specifically, the three-circle tangency method uses an arc to replace the radius R of the transition arc at the weld toe. min ,like Figure 3 As shown. Transition arc radius R min as follows:

[0034] Then proceed to step six, in which the total weld width is determined; specifically, the total weld width 2w is determined to be the weld width 2w designed using the three-circle tangent method, and the total weld width 2w is as follows: .

[0035] Finally, step seven is executed. In step seven, the weld shape and its geometric parameters are obtained based on the minimum reinforcement height curve and the total weld width. Specifically, the required weld shape and its geometric parameter values ​​can be obtained based on the minimum reinforcement height curve and the total weld width.

[0036] Specific embodiment two, the low-matching butt joint shape design device based on equal tension-bending composite load of the present invention, the device includes: The load ratio determination module is used to determine the tension-bending load ratio; The matching ratio calculation module is used to determine the yield strength matching ratio between the weld and the base material; The reinforcement curve calculation module is used to calculate the minimum reinforcement curve of the weld zone and distinguish whether the structural end is subject to rotational constraints. The minimum weld width calculation module is used to calculate the minimum weld width and distinguish the structural end constraint type; The transition arc determination module is used to determine the radius of the transition arc at the weld toe using the three-circle tangency method. The total weld width determination module is used to determine the total weld width. The geometry generation module is used to obtain the weld shape and its geometric parameters based on the minimum excess height curve and the total weld width.

[0037] In the third specific implementation method, an X-shaped bevel is made between the weld seam and the flat plate, with a bevel angle of 60 degrees. 0 The bevel gap is 2mm, the blunt edge height is 2mm, double-sided welding is used, the thickness is 2t (10mm), the span is 70mm, and the matching ratio is... With a load ratio of 0.6 and a bending load ratio of n of 10, weld beads of sufficient height and width are deposited upwards and on both sides on the basis of ordinary welds.

[0038] 1. Determine the tension-bending load ratio.

[0039] 2. Determine the matching ratio .

[0040] 3. Determine the minimum reinforcement height curve h of the weld zone according to the formula for minimum reinforcement height curve. min (x): .

[0041] 4. Determine the minimum weld width (2w) under combined tensile and bending loads according to the formula: Minimum weld width formula 1. min .

[0042] 5. The radius R of the transition arc at the weld toe is determined using the three-circle tangency method. min .

[0043] 6. Determine the total weld width as 2w.

[0044] 7. Obtain the required weld shape and its geometric parameters, as well as the yield strength values ​​of the base material, welding wire, and post-weld weld; the geometric parameters are shown in Table 1; the strength values ​​are shown in Table 2. Table 1: Geometric Parameters of Welds

[0045] Table 2: Yield strength values ​​of base metal, welding wire and post-weld weld

[0046] Specific implementation method four: Cut an X-shaped bevel at the weld seam against the flat plate, with a bevel angle of 60 degrees. 0The bevel gap is 2mm, the blunt edge height is 2mm, double-sided welding is used, the thickness is 2t (10mm), the span is 70mm, and the matching ratio is... With a load ratio of 0.5 and a bending load ratio of n of 5, weld beads of sufficient height and width are deposited upwards and on both sides on the basis of ordinary welds.

[0047] 1. Determine the tension-bending load ratio.

[0048] 2. Determine the matching ratio .

[0049] 3. Determine the minimum reinforcement height curve h of the weld zone based on the minimum reinforcement height curve formula two. min (x): . 4. Determine the minimum weld width 2w under combined tensile and bending loads according to Formula 2 for minimum weld width. min .

[0050] 5. The radius R of the transition arc at the weld toe is determined using the three-circle tangency method. min .

[0051] 6. Determine the total weld width as 2w.

[0052] 7. Obtain the required weld shape and its geometric parameter values, as well as the yield strength values ​​of the base material, welding wire, and post-weld weld; the geometric parameter values ​​are shown in Table 3; the strength values ​​are shown in Table 4.

[0053] Table 3: Geometric Parameters of Welds

[0054] Table 4: Yield strength values ​​of base metal, welding wire and post-weld weld

Claims

1. A method for designing the shape of a low-matching butt joint based on equal tension-bending composite load, characterized in that, The method includes: S1. Determine the tension-bending load ratio; S2. Determine the yield strength matching ratio between the weld and the base metal; S3. Calculate the minimum excess height curve of the weld zone to distinguish whether the structural end is subject to rotational constraints; S4. Calculate the minimum weld width and distinguish the structural end constraint type; S5. The radius of the transition arc at the weld toe is determined using the three-circle tangency method; S6. Determine the total weld width; S7. Based on the minimum excess height curve and the total weld width, the weld shape and its geometric parameters are obtained.

2. The low-matching butt joint shape design method based on equal tension-bending composite load as described in claim 1, characterized in that, The process of S1 is to apply the tensile load F N With bending load F M In comparison, the tensile-bending load ratio n is obtained as follows: 。 3. The low-matching butt joint shape design method based on equal tension-bending composite load as described in claim 1, characterized in that, The S2 process involves increasing the yield strength R of the base metal. e H b Yield strength R of weld metal e H w In comparison, the yield strength matching ratio between the weld and the base metal was obtained. as follows: 。 4. The low-matching butt joint shape design method based on equal tension-bending composite load as described in claim 1, characterized in that, The S3 process includes: setting the selection conditions for the reinforcement curve, and determining the calculation formula for the minimum reinforcement curve of the weld zone based on the selection conditions, including: Minimum residual height curve type one: , Minimum residual height curve type two: .

5. The low-matching butt joint shape design method based on equal tension-bending composite load according to claim 4, characterized in that, The selection criteria for the excess height curve are: the thickness of the base material (2t), the tensile-bending load ratio (n), the span (l), and the matching ratio. And whether the structural ends are subject to rotational constraints; If the structural end is not subject to rotational constraints, then select curve type one with minimum residual height; if the structural end is subject to rotational constraints, then select curve type two with minimum residual height.

6. The low-matching butt joint shape design method based on equal tension-bending composite load according to claim 1, characterized in that, The S4 process includes: setting the weld width selection criteria, and determining the calculation formula for the minimum weld width based on the weld width selection criteria, including: Minimum weld width, type 1: , Minimum weld width, type two: .

7. The low-matching butt joint shape design method based on equal tension-bending composite load as described in claim 6, characterized in that, The selection condition for the weld width curve is whether the structural end is subject to rotational constraints. If the structural end is not subject to rotational constraints, then the minimum weld width formula one is selected; if the structural end is subject to rotational constraints, then the minimum weld width formula two is selected.

8. The method for designing the shape of a low-matching butt joint based on equal tension-bending composite load according to claim 1, characterized in that, The three-circle tangency method described in S5 uses a circular arc instead of the transition arc radius R at the weld toe. min as follows: 。 9. The method for designing the shape of a low-matching butt joint based on equal tension-bending composite load according to claim 1, characterized in that, The total weld width 2w is as follows: 。 10. A low-matching butt joint shape design device based on equal tension-bending composite load, characterized in that, The device includes: The load ratio determination module is used to determine the tension-bending load ratio; The matching ratio calculation module is used to determine the yield strength matching ratio between the weld and the base material; The reinforcement curve calculation module is used to calculate the minimum reinforcement curve of the weld zone and distinguish whether the structural end is subject to rotational constraints. The minimum weld width calculation module is used to calculate the minimum weld width and distinguish the structural end constraint type; The transition arc determination module is used to determine the radius of the transition arc at the weld toe using the three-circle tangency method. The total weld width determination module is used to determine the total weld width. The geometry generation module is used to obtain the weld geometry and its parameters based on the minimum excess height curve and the total weld width; the geometry includes: load-bearing joint shapes such as tension-bending composite load under different matching ratios, load-bearing butt joint shapes such as X-groove low matching tension-bending composite load, and load-bearing joint shapes such as three-circle tangent.

Images