Method for evaluating static strength of welded structure
By establishing a finite element model and mesh subdivision, and combining material parameters and safety factors, the problem of inaccurate local calculations caused by stress concentration in welded structures was solved, and the accurate assessment of the static strength of welded parts and the assurance of safety were achieved.
Patent Information
- Application Number
- CN202610355936.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-23
- Publication Date
- 2026-06-26
AI Technical Summary
In static strength assessment of welded structures, stress concentration at the weld location leads to inaccurate local calculations and poses a risk of fracture. Existing technologies cannot accurately assess the strength of welded components.
A finite element model is established, and a coarse mesh is used for preliminary calculations. After locating the weld hotspots, the mesh is subdivided. The total stress of the weld is calculated by linearizing the internal stress. Combined with material parameters, section modulus, welding coefficient, and safety factor, the static strength of the welded part is accurately evaluated.
This improves the accuracy of static strength assessment of welded structures, avoids errors in local calculations, and ensures the safety and reliability of welded components.
Smart Images
Figure CN122287210A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of mechanical structures, and more specifically to a method for evaluating the static strength of welded structures. Background Technology
[0002] When performing static strength assessments on welded structures, the weld seam presents the location of the maximum stress in the welded component. This location exhibits singularity, leading to inaccurate local calculations. Directly reading stress values for assessment during the design process can impose design limitations. For example, in the blade locking device of a wind turbine, the reinforcing ribs are connected by welding, and stress concentration occurs at the weld location during calculations. Local stress concentration can cause the welded structure to be under high stress, increasing the risk of fracture. Therefore, a more accurate method for static strength analysis of welded components is needed. Summary of the Invention
[0003] The purpose of this invention is to propose a method for evaluating the static strength of welded structures in order to solve the problems existing in the prior art.
[0004] To achieve the above objectives, this invention proposes a method for evaluating the static strength of welded structures, comprising: A finite element model of the welded structure was established and a coarse mesh was used to perform finite element static strength calculation. The hot spot location of the weld was located based on the results of the first round of finite element static strength calculation. The hot spots in the weld are finely meshed, and the total stress of the weld is calculated by linearizing the internal stress. Determine the material parameters, including yield strength, tensile strength, elongation at break, Young's modulus, tangent modulus, and total critical strain; Determine the section modulus based on the material parameters; The welding coefficient is determined based on the weld type, welding quality, and stress type. The strength of the welded component is calculated based on the section modulus, the welding coefficient, and the material parameters. The safety factor is determined based on the material parameters and the assessment of the consequences of weld failure. The evaluation result is obtained by comparing the ratio of the strength of the welded component to the safety factor and the total stress of the weld.
[0005] Furthermore, a finite element model of the welded structure is established and meshed, including: The hot spots of the weld are divided into hexahedral meshes with a mesh size of 0.2-0.4 times the plate thickness.
[0006] Furthermore, the total stress of the weld is calculated through internal stress linearization, including: Extracting stress distribution along the plate thickness path (x=0 to x=t) And substitute into the following formula to calculate: in, For membrane stress, For bending stress, It is a nonlinear stress peak. This represents the total stress of the weld.
[0007] Furthermore, the yield strength is determined based on the thickness of the welded structure.
[0008] Further, determining the section modulus based on the material parameters includes: The section modulus is determined by taking a fixed value based on the elongation at break or by calculating it using the section modulus formula.
[0009] Furthermore, the section modulus is calculated using the section modulus formula, including: The plastic limit load and elastic limit load were obtained by finite element analysis. The plastic notch factor is calculated using the plastic limit load and the elastic limit load. The section modulus is calculated based on the Young's modulus, the total critical strain, the yield strength, and the plastic notch factor.
[0010] Furthermore, when the ratio of the yield strength to the tensile strength is less than 0.75, a corrected yield strength value is calculated using the yield strength and the tensile strength, and this value is used to calculate the section modulus.
[0011] Furthermore, the plastic limit load and elastic limit load are obtained through finite element analysis, including: Input the yield strength and linear modulus into the finite element model, apply a uniformly varying external load to the weldment, and the maximum external load is obtained to cause significant deformation of the weldment. The relationship between the external load and the deformation of the weldment is obtained, and the plastic limit load is calculated. Taking 1 / 10 of the maximum external load mentioned above, the elastic limit load is calculated using the following formula: in, For 1 / 10 load, Stress at 1 / 10 load R p It represents the yield strength.
[0012] Furthermore, a safety factor is determined based on the aforementioned material parameters and an assessment of the consequences of weld failure, including: When the ratio of the yield strength to the tensile strength is not greater than 0.75, the safety factor adopts the basic safety factor; When the ratio of the yield strength to the tensile strength is greater than 0.75, the safety factor is calculated using the basic safety factor, yield strength, and tensile strength.
[0013] Furthermore, the basic safety factor is determined by combining the assessment of the consequences of weld failure with the possibility that the highest stress and the most unfavorable stress may occur simultaneously and cause failure.
[0014] This invention employs internal stress linearization to calculate the total stress at the weld, avoiding inaccurate local calculations and more realistically reflecting the stress state at the weld location. For the calculation of welded component strength, the material properties are first determined based on the welded structure thickness, and the design parameters are meticulously categorized according to these material parameters to ensure the accuracy of the welded component strength calculation. For the calculation of the safety factor, the components are first classified according to material parameters, and the consequences of welded component failure are analyzed based on the stress conditions of the welded component within the overall structure, improving the accuracy of the safety factor value. Attached Figure Description
[0015] The following figures are included as part of this invention for understanding its principles. The figures illustrate embodiments of the invention and their descriptions, serving to explain the apparatus and principles of the invention. In the figures, Figure 1 This is a flowchart of the static strength evaluation method for welded structures according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the welding structure according to an embodiment of the present invention. Detailed Implementation
[0016] The present application will now be described in more detail with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of the present application more clearly and are not intended to limit the scope of protection of the present application.
[0017] This invention provides a method for evaluating the static strength of welded structures, such as... Figure 1 As shown, the method includes: Step 1: Establish a finite element model of the welded structure and perform finite element static strength calculation using a coarse mesh. Locate the hot spot of the weld based on the results of the first round of finite element static strength calculation.
[0018] Step 2: Detail the meshing of the hot spots in the weld and calculate the total stress of the weld by linearizing the internal stress.
[0019] The mesh type uses a hexahedral mesh, and the mesh size at weld hotspot locations can be 0.2-0.4 times the plate thickness. For example... Figure 2As shown, if the weldment plate is 30mm thick, the mesh size range will be controlled between 6-12mm. This step, following the initial static strength calculation, involves precise calculation of the actual stress experienced by the weld.
[0020] To avoid model singularity, the total stress in the weld is calculated by linearizing the internal stress. First, the stress distribution is extracted along the plate thickness path (x=0 to x=t). Substitute into the following formula to calculate: (1) (2) (3) (4) in, For membrane stress, For bending stress, It is a nonlinear stress peak. This represents the total stress of the weld.
[0021] Step 3: Determine the material parameters, including yield strength Rp, tensile strength Rm, elongation at break A, Young's modulus E, tangent modulus Et, and total critical strain. .
[0022] This step determines the welding structure material and the material properties based on the structure thickness. The materials for Q355 steel are shown in Table 1 below: Table 1 As can be seen from Table 1, when the structural thickness T is less than 40 mm, the yield strength Rp is 360 MPa; when the structural thickness T is between 40 mm and 100 mm, the yield strength Rp is 335 MPa.
[0023] Step 4: Determine the section modulus based on the material parameters.
[0024] First, the section modulus is determined by taking a fixed value or calculating it using the section modulus formula based on the elongation at break (A). To ensure the accuracy of the evaluation, this application adopts a scheme of classifying the section modulus according to the material's plasticity. Specifically, when A < 6%, the material is brittle or has low plasticity. =1; When A≥6%, the material has good plasticity, and the section modulus can be calculated using the following formula: (5) (6) in, Where E is the section modulus and E is Young's modulus. Rp is the total critical strain, and Rp is the yield strength. The plasticity notch factor, For plastic limit load, This is the elastic limit load.
[0025] The plastic limit load and elastic limit load are obtained through finite element analysis. Specifically, the yield strength and linear modulus are input into the finite element model, and a uniformly varying external load is applied to the weldment. The maximum external load is used to cause significant deformation of the weldment, and the relationship between the external load and the deformation of the weldment is obtained to calculate the plastic limit load. Taking 1 / 10 of the maximum external load, the elastic limit load is calculated using the following formula: (7) in, For 1 / 10 load, Stress at 1 / 10 load R p It represents the yield strength.
[0026] Materials harden during actual plastic deformation, increasing their yield strength. When using finite element analysis, only a yield value is input, ignoring the hardening phenomenon and leading to a more conservative plastic notch factor. Therefore, to improve the accuracy of the section modulus, this application introduces a yield strength correction value. Tensile strength indirectly reflects the material's hardening ability and plays a compensating role in the formula. Specifically, when the ratio of yield strength Rp to tensile strength Rm (Rp / Rm < 0.75), a yield strength correction value is introduced: (8) Substitute the yield strength correction value into the above formula (5) to calculate the section modulus. .
[0027] Step 5: Determine the welding coefficient based on the weld type, welding quality, and stress type.
[0028] Taking a steel welded structure with full weld penetration as an example, the welding coefficient is [value missing] under the condition that the welding quality is qualified. .
[0029] Step 6: Calculate the strength of the welded part based on the section modulus, welding coefficient, and material parameters.
[0030] The strength of welded components is calculated using the following formula: (9) in, R p For yield strength, For welding coefficient, is the section modulus.
[0031] Step 7: Determine the safety factor based on the material parameters and the assessment of the consequences of weld failure.
[0032] When the ratio of yield strength Rp to tensile strength Rm, Rp / Rm, is ≤0.75, the basic safety factor is adopted: (10) When the ratio of yield strength Rp to tensile strength Rm, Rp / Rm > 0.75, the safety factor is calculated using the basic safety factor, yield strength, and tensile strength. (11) The basic safety factor is determined by combining the assessment of the consequences of weldment failure and the possibility of failure caused by the simultaneous occurrence of the highest stress and the most unfavorable stress, as shown in Table 2 below. The corresponding basic safety factor can be obtained from Table 2. and Regarding the classification of welded component failure consequences, taking "moderate" as an example, this refers to an analysis based on the overall structure in which the welded structure exists. If the welded component fails, there will be no catastrophic consequences, such as the redistribution of loads to other components in a statically indeterminate system. The highest stress refers to the stress with the largest numerical value experienced by the component, and the most unfavorable stress refers to the stress that has the greatest impact on the component's strength. By combining the external loads that cause these two stresses, the failure consequences are assessed, and a comprehensive selection is made.
[0033] Taking the blade locking device of a wind turbine as an example, this device is used to lock the blades during wind turbine maintenance. The probability of the highest / most unfavorable stress combination occurring during the use of the blade locking device is high, and the consequences of failure are severe. Therefore, the basic safety factor is... , The values were selected as 2 and 1.5 in turn.
[0034] Step 8: The evaluation results are obtained by comparing the ratio of the weld strength to the safety factor and the total stress of the weld.
[0035] (12) When the total stress of the weld Not greater than the strength of the welded part With safety factor When the ratio is , the static strength assessment of the welded structure is qualified.
[0036] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software may depend on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods for each specific application to implement the described functions, but such implementation should not be considered beyond the scope of the embodiments of this disclosure.
[0037] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.
[0038] The methods and products (including but not limited to devices and equipment) disclosed in the embodiments herein can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For instance, the division of units may only be a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces, and the indirect coupling or communication connection of devices or units may be electrical, mechanical, or other forms.
[0039] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for descriptive purposes only and is not intended to limit the invention. Terms such as “part” or “component” appearing herein can refer to a single part or a combination of multiple parts. Terms such as “installation” or “installation” appearing herein can refer to one component being directly attached to another component or one component being attached to another component via an intermediary. A feature described in one embodiment herein may be applied, alone or in combination with other features, to another embodiment, unless that feature is not applicable in that other embodiment or is otherwise stated.
[0040] The present invention has been described through the above embodiments. However, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the present invention to the described embodiments. Furthermore, those skilled in the art will understand that the present invention is not limited to the above embodiments, and many variations and modifications can be made based on the teachings of the present invention, all of which fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method of welded structure static strength evaluation, characterized by, include: A finite element model of the welded structure was established and a coarse mesh was used to perform finite element static strength calculation. The hot spot location of the weld was located based on the results of the first round of finite element static strength calculation. The hot spots in the weld are finely meshed, and the total stress of the weld is calculated by linearizing the internal stress. Determine the material parameters, including yield strength, tensile strength, elongation at break, Young's modulus, tangent modulus, and total critical strain; Determine the section modulus based on the material parameters; The welding coefficient is determined based on the weld type, welding quality, and stress type. The strength of the welded component is calculated based on the section modulus, the welding coefficient, and the material parameters. The safety factor is determined based on the material parameters and the assessment of the consequences of weld failure. The evaluation result is obtained by comparing the ratio of the strength of the welded component to the safety factor and the total stress of the weld.
2. The welded structure static strength evaluation method according to claim 1, characterized by, Establish a finite element model of the welded structure and perform mesh generation, including: The hot spots of the weld are divided into hexahedral meshes with a mesh size of 0.2-0.4 times the plate thickness.
3. The welded structure static strength evaluation method according to claim 1, characterized by, The total stress of the weld is calculated by linearizing the internal stress, including: Stress distribution is extracted along the plate thickness path (x=0 to x=t) and entered into the following equation to calculate: ； ； ； ； in, For membrane stress, For bending stress, It is a nonlinear stress peak. This represents the total stress of the weld.
4. The method for evaluating the static strength of welded structures according to claim 1, characterized in that, The yield strength is determined based on the thickness of the welded structure.
5. The method for evaluating the static strength of welded structures according to claim 1, characterized in that, Determining the section modulus based on the material parameters includes: The section modulus is determined by taking a fixed value based on the elongation at break or by calculating it using the section modulus formula.
6. The method for evaluating the static strength of welded structures according to claim 5, characterized in that, The section modulus is calculated using the section modulus formula, including: The plastic limit load and elastic limit load were obtained by finite element analysis. The plastic notch factor is calculated using the plastic limit load and the elastic limit load. The section modulus is calculated based on the Young's modulus, the total critical strain, the yield strength, and the plastic notch factor.
7. The method for evaluating the static strength of welded structures according to claim 6, characterized in that, When the ratio of the yield strength to the tensile strength is less than 0.75, a corrected yield strength value is calculated using the yield strength and the tensile strength, and this value is used to calculate the section modulus.
8. The method for evaluating the static strength of welded structures according to claim 6, characterized in that, The plastic limit load and elastic limit load were obtained through finite element analysis, including: Input the yield strength and linear modulus into the finite element model, apply a uniformly varying external load to the weldment, and the maximum external load is obtained to cause significant deformation of the weldment. The relationship between the external load and the deformation of the weldment is obtained, and the plastic limit load is calculated. Taking 1 / 10 of the maximum external load mentioned above, the elastic limit load is calculated using the following formula: ； in, For 1 / 10 load, Stress at 1 / 10 load R p It represents the yield strength.
9. The method for evaluating the static strength of welded structures according to claim 1, characterized in that, The safety factor is determined based on the material parameters and the assessment of the consequences of weld failure, including: When the ratio of the yield strength to the tensile strength is not greater than 0.75, the safety factor adopts the basic safety factor; When the ratio of the yield strength to the tensile strength is greater than 0.75, the safety factor is calculated using the basic safety factor, yield strength, and tensile strength.
10. The method for evaluating the static strength of welded structures according to claim 9, characterized in that, The basic safety factor is determined by combining the assessment of the consequences of weld failure with the possibility that the highest stress and the most unfavorable stress may occur simultaneously and cause failure.