Method for evaluating fatigue behavior of cross-welded structure of dynamic load high-strength steel

Abstract

The application discloses a kind of dynamic load high-strength steel cross-welded structure fatigue behavior evaluation method, consider the complex residual stress state caused by the interaction of butt weld and fillet weld in high-strength steel serving in dynamic load occasion, and the actual situation that has significant influence on the overall fatigue behavior of structure during service, and through fatigue specimen model and size design, cross-welded joint design and production, fatigue behavior evaluation test process control, to accurately simulate the complex residual stress state in the actual cross-welded structure, realize the indirect evaluation of high-strength steel box structure fatigue behavior serving in dynamic load occasion.

Description

Technical Field

[0001] This invention relates to the evaluation technology of high-strength steel cross-welded structures, and more specifically, to a method for evaluating the fatigue behavior of high-strength steel cross-welded structures under dynamic loads. Background Technology

[0002] In many important industrial structures, welded joints often become the weakest link during service, especially welded structures operating under dynamic loads. Even alternating fatigue loads below the material and structural yield strength cause intense stress concentrations at the weld toe on both sides of the weld. Coupled with the inherent microscopic discontinuities of welded structures, fatigue failure of welded joints is the main form of structural failure. Early fatigue failure of welded structures caused by the initiation, propagation, and fracture of fatigue cracks has become a significant factor restricting the safe service life of structural components, and related research and evaluation have attracted widespread attention from the industry.

[0003] Welding is a non-equilibrium solidification and solid-state phase transformation process, inevitably producing discontinuities or abrupt changes at the macroscopic or microscopic level. Under alternating loads, these often develop into initial fatigue crack initiations, especially microscopic defects at the weld toe, which can directly enter the propagation stage without crack initiation. Simultaneously, residual tensile stress generated during welding, weld toe geometry, and stress concentrations from microscopic defects during service promote the propagation of initial fatigue cracks, leading to a reduction in the fatigue strength and fatigue life of the welded structure. For evaluating the fatigue behavior of welded joints or structures, GB / T 3075-2008, "Methods for Axial Force Control in Fatigue Testing of Metallic Materials," is a commonly used industry standard, but it has significant limitations. First, this standard primarily targets uniform base metals. If fatigue performance evaluations of joints are conducted based on this standard while retaining weld reinforcement, the evaluation results will be overly conservative and may not accurately reflect the actual fatigue behavior of high-strength steel welded structures. Secondly, high-strength steel welded structures operating under dynamic loads often include multiple weld types that intersect, including common butt welds, as well as fillet welds and lap welds. The nonlinear superposition of residual stress fields from different joint types creates a complex residual stress state within the structure, which promotes early fatigue failure of dynamically loaded structures. However, currently published standards do not address the evaluation of fatigue behavior of welded structures under the interaction of different weld types.

[0004] Currently, there are existing technologies for evaluating the fatigue performance of high-strength steel welded structures. For example, application number CN201710025468.X discloses a fatigue testing method for welded structures of rail transit vehicle bodies. This method involves rigidly and elastically fixing both ends of the actual vehicle body structure onto a fatigue testing machine to form a test assembly. The actual stress centerline of the welded structure is aligned with the fatigue loading stress axis, and the load is applied using numerical simulation values. While this method of using actual structural components for fatigue evaluation can accurately determine the fatigue performance of the actual structure under simulated service conditions, it is complex, costly, and relatively time-consuming. Application number CN201510963648.3 discloses a fatigue specimen for a cross-welded joint, which involves welding a fillet weld on a machined, integrally formed substrate and monitoring fatigue cracking after fatigue loading. However, it does not address the fatigue behavior evaluation after cross-coupling with a positive load-bearing butt joint. Application No. CN201611035960.7 discloses a method for measuring the intrinsic fatigue crack propagation rate of welded plates perpendicular to the weld direction. This technique applies solid mechanics theory, calculates the residual stress intensity factor and the superposition of residual stress fields to obtain the external load required for different crack lengths, thereby determining the intrinsic fatigue crack propagation rate of the weld material under given conditions. However, it does not address high-cycle fatigue evaluation based on the cumulative damage principle. Application No. CN201611076258.5 discloses a method for preparing and applying fatigue specimens of plate-shaped welded components. By attaching strain gauges to the welded component and cutting it strip by strip to observe the changes in welding residual stress, it obtains the minimum width of the fatigue specimen retaining residual stress and the maximum width completely releasing residual stress. This method can reflect the influence of welding residual stress on joint fatigue; however, it does not consider the overall structural fatigue problem caused by the interaction of different weld types.

[0005] Therefore, there is an urgent need to develop a simple, convenient, and low-cost evaluation method for the fatigue behavior of cross-welded joints of high-strength steel. This method should be able to accurately and objectively reflect the influence of the complex residual stress state of butt and fillet welds on the fatigue behavior of the overall structure, and should be easy and quick to implement, indirectly evaluating the fatigue behavior of cross-welded joints of high-strength steel box structures under dynamic loads. Summary of the Invention

[0006] To address the aforementioned deficiencies in existing technologies, the purpose of this invention is to provide a method for evaluating the fatigue behavior of dynamic high-strength steel cross-welded structures. This method considers the complex residual stress state caused by the interaction between butt welds and fillet welds in high-strength steel under dynamic loads, and the actual situation that this interaction significantly affects the overall fatigue behavior of the structure during service. Through fatigue specimen model and size design, cross-welded joint design and fabrication, and fatigue behavior evaluation test process control, this method can accurately simulate the complex residual stress state in actual cross-welded structures, thereby achieving an indirect evaluation of the fatigue behavior of high-strength steel box structures under dynamic loads.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides a method for evaluating the fatigue behavior of dynamically loaded high-strength steel cross-welded structures, comprising the following steps:

[0009] S1, Fatigue Specimen Design: A high-strength steel cross-welded structure fatigue specimen has mutually perpendicular butt welds and overlay welds. The width W and thickness B of the fatigue specimen satisfy the following formula: W = (8~12) × B + 2 × F d In the formula, W is the width of the fatigue specimen in mm, B is the thickness of the fatigue specimen in mm, and F... d The width of the weld seam on the fatigue specimen is in mm; the length L of the fatigue specimen satisfies the following formula: L=(2.5~3)×W, where L is the length of the fatigue specimen in mm and W is the width of the fatigue specimen in mm.

[0010] S2, Smoothing treatment: The cross-welding area of ​​the butt weld and the overlay weld on the fatigue specimen is smoothed to obtain a smoothed area.

[0011] S3, Fatigue behavior evaluation test: The fatigue specimens treated in step S2 are subjected to fatigue behavior evaluation test by loading a sinusoidal load, and the conditional fatigue life of the high-strength steel cross-welded structure is obtained, thus completing the fatigue behavior evaluation of the high-strength steel cross-welded structure.

[0012] Preferably, in step S1, the size of the fatigue specimen is obtained through finite element simulation calculation.

[0013] Preferably, in step S1, the fatigue specimen has a test area and a clamping area, and the length L of the test area is... v The width W of the test area is 200-300 mm. v The radius of the positioning hole in the clamping area is 6-10 mm, and the radius of the positioning hole is 70-130 mm.

[0014] Preferably, in step S1, the weld width F of the fatigue specimen weld seam is... d The difference in weld width between the weld and the fatigue test specimen shall not exceed 10 mm.

[0015] Preferably, in step S1, the fabrication of the cross-welded structure on the fatigue specimen includes the fabrication of butt welds, the fabrication of overlay welds, and welding quality inspection.

[0016] During the fabrication of the weld overlay, after the butt weld is fabricated, an arc-shaped groove is machined at the weld overlay location on the fatigue specimen. The depth d of the arc-shaped groove is 1–5 mm, and the width W of the arc-shaped groove is… d It is 8-15mm;

[0017] The roughness R of the two sides of the fatigue specimen to be fatigue tested a Not exceeding 12.5.

[0018] Preferably, in step S2,

[0019] The smoothed region is rectangular, and the relative distance between the boundary of the smoothed region and the boundaries of the butt weld and the overlay weld satisfies the following formula:

[0020] g1 = g2 = (0.6 ~ 0.8) × B

[0021] In the formula, g1 is the relative distance between the vertical boundary of the smoothed region and the boundary of the butt weld, in mm;

[0022] g2 is the relative distance between the horizontal boundary of the smoothed region and the boundary of the weld seam, in mm;

[0023] B represents the thickness of the fatigue specimen, in mm;

[0024] The surface roughness R of the smoothed region a Not exceeding 12.5.

[0025] Preferably, in step S3, the stress ratio of the sinusoidal load is 0.1, and the loading frequency is 5-15Hz.

[0026] Preferably, in step S3, during the fatigue behavior evaluation test, the maximum displacement during loading is used as the failure judgment parameter. When the maximum displacement increases by 20%, the fatigue specimen fails, and the corresponding number of cycles is the conditional fatigue life of the high-strength steel cross-welded structure.

[0027] Preferably, in step S3, the fatigue behavior evaluation of the high-strength steel cross-welded structure follows the following principles:

[0028] If fatigue fracture occurs in areas other than the butt weld and overlay weld of the fatigue specimen, the fatigue behavior evaluation test results are considered invalid, and a new fatigue specimen needs to be prepared for a fatigue behavior evaluation test under the same load level.

[0029] Perform no fewer than three fatigue behavior evaluation tests under the same load level, and introduce the conditional fatigue life deviation rate d. R To determine whether the fatigue behavior evaluation test results are valid, if the conditional fatigue life deviation rate d R If the result is ≤30%, the fatigue behavior evaluation test result is valid; otherwise, it is necessary to analyze the causes of the dispersion and re-prepare fatigue specimens for replication until d R ≤30%.

[0030] Preferably, in step S3, the conditional fatigue life deviation rate d R Calculated using the following formula:

[0031]

[0032] In the formula, d R The conditional fatigue life deviation rate is expressed in %;

[0033] N min This represents the minimum conditional fatigue life among the fatigue specimens in the same group, in tens of thousands of cycles.

[0034] N max The maximum conditional fatigue life among the fatigue specimens in the same group, in tens of thousands of cycles;

[0035] The average fatigue life of the fatigue specimens in the same group under the same conditions, in 10,000 cycles;

[0036] in, n is the number of fatigue specimens in the same group, n≥3.

[0037] The fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures provided by this invention has the following advantages:

[0038] 1. The fatigue behavior evaluation method of dynamic load high-strength steel cross-welded structure of the present invention considers the complex residual stress state caused by the interaction between butt welds and fillet welds in general dynamic load box structure and its influence on the overall fatigue behavior of the structure during service. The indirect evaluation results are close to the actual dynamic load service of box structure and have good applicability.

[0039] 2. The fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures of the present invention can quickly evaluate the fatigue performance of typical welded structures in dynamic load conditions at a low cost without the need for fatigue evaluation of large structural components, providing technical guidance for the safe service of structures. It has the advantages of high reliability of evaluation results, high efficiency and low cost.

[0040] 3. The fatigue behavior evaluation method for cross-welded structures of high-strength steel under dynamic load of the present invention is applicable to the fatigue behavior evaluation of butt joints and corner joints (including T-joints and cross joints) of high-strength steel of various strength grades obtained by different welding methods and processes. By optimizing the cross weld arrangement, the residual stress state and fatigue behavior characteristics of the cross weld part of the box structure in actual dynamic load service are simulated. It can conveniently and quickly conduct indirect evaluation of fatigue behavior of box structures in dynamic load service, which has important guiding significance for the application of high-strength steel in dynamic load situations.

[0041] 4. The fatigue behavior evaluation method for cross-welded high-strength steel structures under dynamic load of the present invention takes into account the complex residual stress state caused by the interaction between butt welds and fillet welds in actual box structures subjected to dynamic loads and its influence on the overall fatigue behavior of the structure during service. It can simulate the complex residual stress state in actual box structures with cross welds, thus eliminating the need for actual fatigue behavior evaluation of large structural components. It can ensure that the evaluation results are close to the actual box structure and can provide important guidance and safety assurance for the welding construction and application of high-strength steel in dynamic fatigue situations.

[0042] 5. The fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures of the present invention is a common technology for evaluating the fatigue behavior of welded joints. It has good universal applicability in various industrial products that are subjected to dynamic load fatigue service, with a wide coverage and broad prospects for promotion and application. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the fatigue specimen with cross welds used in the fatigue behavior evaluation method of dynamic load high-strength steel cross-welded structure of the present invention.

[0044] Figure 2 In the figure, (a) is a schematic diagram of the width of the weld groove in the fatigue specimen with cross welds, and (b) is a schematic diagram of the depth of the weld groove in the fatigue specimen with cross welds.

[0045] Figure 3 This is a schematic diagram of the smoothed cross-weld area in the fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures of the present invention.

[0046] Figure 4 This is a schematic diagram of fatigue behavior evaluation in the fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures of the present invention; Figure 4In the diagram, 1 is the indenter, 2 is the base, and 3 is the fatigue specimen. Detailed Implementation

[0047] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0048] The present invention provides a fatigue behavior evaluation method for cross-welded high-strength steel structures under dynamic loads. This method primarily considers the complex residual stress state caused by the interaction between butt welds and fillet welds in typical high-strength steel box-type structures operating under dynamic loads, which significantly impacts the overall fatigue behavior of the structure during service. An indirect fatigue behavior evaluation method based on large-size cross-welded specimens is designed. Through specimen type and size design, cross-welded joint design and fabrication, fatigue behavior evaluation test process control, and the formulation of fatigue behavior evaluation principles, this method can accurately simulate the complex residual stress state actually present in cross-welded box-type structures, thereby enabling indirect evaluation of the fatigue behavior of box-type structures operating under dynamic loads.

[0049] The present invention provides a method for evaluating the fatigue behavior of a dynamic load high-strength steel cross-welded structure, comprising the following steps:

[0050] S1, Fatigue Specimen Design: High-strength steel cross-welded structure fatigue specimens have mutually perpendicular butt welds and overlay welds. The width W of the fatigue specimen and the thickness B of the fatigue specimen satisfy the following formula: W=(8~12)×B+2×F d In the formula, W is the width of the fatigue specimen in mm, B is the thickness of the fatigue specimen in mm, and F... d The width of the weld overlay on the fatigue specimen is in mm;

[0051] Specifically, residual tensile stress is prevalent in high-strength steel structural components. During dynamic load service, this residual tensile stress, combined with external loads, increases the tendency for fatigue failure in welded structures. In the commonly used box-type design for dynamic load structures, numerous butt joints bearing principal stresses intersect with corner joints, T-joints, and cross joints serving as connections. Repeated welding thermal cycles at these locations create complex residual stress states, significantly impacting the overall fatigue behavior of the structure during service. Therefore, optimized design is crucial. Figure 1The diagram shows a fatigue specimen with intersecting welds simulating a dynamic load box structure. The butt welds and the simulated fillet welds are perpendicular to each other. Specifically, the butt weld is located at the center perpendicular to the specimen's length, while the simulated fillet weld is positioned at the center of the width parallel to the specimen's length. This simulates the influence of the intersecting welds (butt and fillet) on the overall residual stress state of the box structure. Considering the correlation between the residual stress state in the welded structure and the plate thickness and width, and through finite element simulation calculations, the fatigue specimen width W (mm) and length L (mm) that accurately reflect the residual stress state of the intersecting joints in the actual box structure are determined. The following relationship is established between these two values ​​and the fatigue specimen thickness (original plate thickness, mm):

[0052] The width W and thickness B of the fatigue specimen satisfy the following formula:

[0053] W = (8~12) × B + 2 × F d ………………………………………………(1)

[0054] In the formula, W is the width of the fatigue specimen in mm, B is the thickness of the fatigue specimen in mm, and F... d The width of the weld overlay on the fatigue specimen is in mm;

[0055] The length L of the fatigue specimen satisfies the following formula:

[0056] L=(2.5~3)×W……………………………………………………(2)

[0057] In the formula, L is the length of the fatigue specimen in mm, and W is the width of the fatigue specimen in mm.

[0058] Combination Figure 1 As shown, the fatigue specimen has a test area and a clamping area, and the length L of the test area is... v The width W of the test area is 200-300 mm. v The radius R of the positioning hole in the clamping area is 6-10 mm. In the clamping area, the nearest distances a and b between the center of the inner positioning hole and the boundary of the fatigue specimen, as well as the nearest distance c between the centers of two adjacent inner positioning holes, are equal, i.e., a = b = c.

[0059] The fabrication of cross-welded structures on fatigue specimens includes the fabrication of butt welds, the fabrication of overlay welds, and welding quality inspection.

[0060] (1) Fabrication of butt welds: According to actual needs, the welding groove is processed, including but not limited to single-sided and double-sided V-groove, Y-groove or U-groove. In combination with the actual application scenario of the specific industrial field, representative welding process methods are selected, including but not limited to manual shielded metal arc welding (SMAW), gas metal arc welding (GMAW), tungsten inert gas welding (TIG), submerged arc welding (SAW), plasma arc welding (PAW), laser welding (LW), etc., to ensure the surface and internal welding quality.

[0061] (2) Fabrication of the overlay weld: On the welding plate where the butt weld has been completed, the overlay weld is welded perpendicular to the butt weld. The welding method is consistent with that of the butt weld, including but not limited to manual shielded metal arc welding (SMAW), gas metal arc welding (GMAW), tungsten inert gas welding (TIG), submerged arc welding (SAW), plasma arc welding (PAW), laser welding (LW), etc., to ensure surface and internal welding quality. No grinding or cleaning is required at the intersection of the butt weld and the overlay weld. To ensure that the overlay weld can accurately simulate the influence of fillet joints, T-joints, cross joints, etc., on the overall residual stress state of the actual box structure, the size of the overlay weld needs to be controlled to a certain extent. Combined with... Figure 2 As shown in (a) and (b), after the butt weld is fabricated, an arc-shaped groove is machined at the weld overlay position of the fatigue specimen. The depth d of the arc-shaped groove is 1-5 mm, and the width W of the arc-shaped groove is... d The weld width F of the fatigue specimen weld seam is 8-15 mm. d The difference in weld width between the weld and the fatigue test specimen should not exceed 10 mm.

[0062] (3) Welding quality inspection: For fatigue specimens that have completed butt welding and overlay welding, the surface macroscopic inspection and manual ultrasonic non-destructive testing are used to determine whether the welding quality meets the requirements of fatigue evaluation test. The acceptance standards for surface and internal welding defects vary depending on the specific requirements of different industrial fields.

[0063] (4) After passing quality inspection, according to Figure 1 The requirement is to fabricate fatigue test specimens of high-strength steel cross-welded structures, ensuring that the surface roughness R of the two sides of the specimens to be subjected to fatigue testing is maintained. a Not exceeding 12.5.

[0064] S2, Smoothing treatment: The cross-welding area of ​​the butt weld and the overlay weld on the fatigue specimen is smoothed to obtain a smoothed area.

[0065] Specifically, for the fatigue specimens that have undergone the aforementioned processing, mechanical methods are used to smooth the intersecting weld seams. This avoids stress concentration caused by the shape of the intersecting weld seams, especially geometric abrupt changes, which could lead to early low-cycle fatigue failure in this area. After this treatment, the notch stress concentration caused by geometric factors is significantly reduced, and the internal welding residual stress is essentially preserved, similar to the state of a box structure actually in dynamic load applications. Figure 3 As shown. The smoothed area is obtained by smoothing the intersecting welding areas of the butt weld and the surfacing weld. The relative distances between the boundaries of the smoothed area in each direction and the boundaries of the butt weld and the surfacing weld must satisfy the following formula:

[0066] g1 = g2 = (0.6 ~ 0.8) × B

[0067] In the formula, g1 is the relative distance between the vertical boundary of the smoothed region and the boundary of the butt weld, in mm;

[0068] g2 is the relative distance between the horizontal boundary of the smoothed region and the boundary of the weld overlay, in mm;

[0069] B represents the thickness of the fatigue specimen, in mm;

[0070] Combination Figure 3 As shown, the smoothed region is rectangular. Furthermore, the surface roughness R of the smoothed region is... a The angle should not exceed 12.5. The four ends of the butt weld and the overlay weld should transition smoothly without any obvious sharp angles.

[0071] S3, Fatigue behavior evaluation test: The fatigue specimens treated in step S2 are subjected to fatigue behavior evaluation test by loading a sinusoidal load, and the conditional fatigue life of the high-strength steel cross-welded structure is obtained, thus completing the fatigue behavior evaluation of the high-strength steel cross-welded structure.

[0072] Combination Figure 4 The bending compression-compression loading mode shown employs a sinusoidal load for fatigue behavior evaluation testing. The fatigue specimen 3 is placed between the indenter 1 and the base 2, and a load is applied through the indenter 1. In a specific embodiment, the side of the fatigue specimen with the butt weld and overlay weld, after being treated in step S2, is placed in a tension position. During loading, the stress ratio of the sinusoidal load is 0.1, and the loading frequency is 5–15 Hz. In the fatigue behavior evaluation test, the maximum displacement during loading is used as the failure criterion. When the maximum displacement increases by 20%, the fatigue specimen fails, and the corresponding number of cycles is the conditional fatigue life of the high-strength steel cross-welded structure.

[0073] The following principles should be followed in the fatigue behavior evaluation of high-strength steel cross-welded structures:

[0074] (1) If fatigue fracture occurs in areas other than the butt weld and the weld overlay of the fatigue specimen, the fatigue behavior evaluation test results are considered invalid and a new fatigue specimen needs to be prepared for a fatigue behavior evaluation test under the same load level.

[0075] (2) Conduct no fewer than three fatigue behavior evaluation tests under the same load level, and introduce the conditional fatigue life deviation rate d. R To determine the validity of fatigue behavior evaluation test results, if the conditional fatigue life deviation rate d R If the result is ≤30%, the fatigue behavior evaluation test result is valid; otherwise, it is determined that the test result has too much dispersion under the same test conditions, and it is necessary to analyze the cause of the dispersion and re-prepare fatigue specimens for replication until d R ≤30%.

[0076] Among them, the conditional fatigue life deviation rate d R Calculated using the following formula:

[0077]

[0078] In the formula, d R The conditional fatigue life deviation rate is expressed in %;

[0079] N min This represents the minimum conditional fatigue life among the fatigue specimens in the same group, in tens of thousands of cycles.

[0080] N max The maximum conditional fatigue life among the fatigue specimens in the same group, in tens of thousands of cycles;

[0081] The average fatigue life of the fatigue specimens in the same group under the same conditions, in 10,000 cycles;

[0082] in, n is the number of fatigue specimens in the same group, n≥3.

[0083] The fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures of the present invention will be further introduced below with specific examples.

[0084] Example

[0085] Hot-rolled Q550E steel plates with wall thicknesses of 8mm, 12mm, and 16mm were selected respectively. Based on the mainstream solid wire gas shielded automatic welding (GMAW) process used in on-site structural component manufacturing, the technology of this invention was applied to complete butt welding and surfacing tests perpendicular to the butt weld seam to ensure the joint welding quality and prepare... Figure 1 The high-strength steel box-type structure cross-welded joint fatigue indirect evaluation specimen shown is simultaneously evaluated according to... Figure 3Smoothing treatment of the cross-weld area of ​​the fatigue test specimens is required. The main dimensions of the fatigue test specimens are shown in Table 1. A fixed maximum stress value of 0.5 to 0.6 times the specified minimum yield strength of Q550E steel plate is selected as the maximum stress value for conditional fatigue life evaluation; here, 300 MPa is taken, with a stress ratio of 0.1, for indirect evaluation of the fatigue behavior of the cross-welded joints of the high-strength steel box structure. The bending load is calculated based on the location of the maximum tensile stress during bending fatigue loading, i.e., the tensile stress at the butt weld in the middle of the specimen, which is 300 MPa. Considering the dispersion of fatigue performance data, tests were conducted on 3 samples for each set of examples. The results of the indirect fatigue evaluation are shown in Table 2.

[0086] Table 1 Design dimensions of fatigue specimens for high-strength steel butt joints

[0087]

[0088] Table 2. Fatigue performance evaluation results of high-strength steel butt joints

[0089] <![CDATA[σ max (MPa)]]> Conditional fatigue life (10,000 cycles) <![CDATA[d R (%)]]> Example 1 300 195 / 160 / 156 ≤30％ Example 2 300 122 / 109 / 149 ≤30％ Example 3 300 103 / 87 / 126 ≤30％

[0090] As shown in Tables 1 and 2, the fatigue test data of each group of specimens in the examples exhibit low dispersion and good consistency, as reflected in the conditional fatigue life deviation rate d. R All requirements were met, and the test evaluation results were valid. Furthermore, the conditional fatigue life gradually decreased with the increase of the wall thickness of the high-strength steel cross-welded structural plates, which is consistent with actual conditions.

[0091] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A method for evaluating the fatigue behavior of a dynamic load-bearing high-strength steel cross-welded structure, characterized in that... This includes the following steps: S1, Fatigue Specimen Design: A high-strength steel cross-welded structure fatigue specimen has mutually perpendicular butt welds and overlay welds. The width W and thickness B of the fatigue specimen satisfy the following formula: W = (8~12) × B + 2 × F d The length L of the fatigue specimen satisfies the following formula: L = (2.5~3) × W, where L is the length of the fatigue specimen, W is the width of the fatigue specimen, B is the thickness of the fatigue specimen, and F is the length of the fatigue specimen. d The width of the weld overlay on the fatigue specimen is in mm. S2, Smoothing treatment: The cross-welding area of ​​the butt weld and the overlay weld on the fatigue specimen is smoothed to obtain a smoothed area. S3, Fatigue behavior evaluation test: The fatigue specimens treated in step S2 are subjected to fatigue behavior evaluation test by loading a sinusoidal load, and the conditional fatigue life of the high-strength steel cross-welded structure is obtained, thus completing the fatigue behavior evaluation of the high-strength steel cross-welded structure.

2. The fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures according to claim 1, characterized in that: In step S1, the dimensions of the fatigue specimen are obtained through finite element simulation calculation.

3. The fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures according to claim 1, characterized in that: In step S1, the fatigue specimen is provided with a test area and a clamping area, and the length L of the test area is... v The width W of the test area is 200-300 mm. v The radius of the positioning hole in the clamping area is 6-10 mm, and the radius of the positioning hole is 70-130 mm.

4. The fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures according to claim 1, characterized in that: In step S1, the weld width F of the fatigue specimen weld seam d The difference in weld width between the weld and the fatigue test specimen shall not exceed 10 mm.

5. The fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures according to claim 4, characterized in that: In step S1, the fabrication of the cross-welded structure on the fatigue specimen includes the fabrication of butt welds, the fabrication of overlay welds, and welding quality inspection. During the fabrication of the weld overlay, after the butt weld is fabricated, an arc-shaped groove is machined at the weld overlay location on the fatigue specimen. The depth d of the arc-shaped groove is 1–5 mm, and the width W of the arc-shaped groove is… d It is 8-15mm; The roughness R of the two sides of the fatigue specimen to be fatigue tested a Not exceeding 12.

5.

6. The fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures according to claim 1, characterized in that, In step S2 The smoothed region is rectangular, and the relative distance between the boundary of the smoothed region and the boundaries of the butt weld and the overlay weld satisfies the following formula: g1 = g2 = (0.6 ~ 0.8) × B In the formula, g1 is the relative distance between the vertical boundary of the smoothed region and the boundary of the butt weld, in mm; g2 is the relative distance between the horizontal boundary of the smoothed region and the boundary of the weld seam, in mm; B represents the thickness of the fatigue specimen, in mm; The surface roughness R of the smoothed region a Not exceeding 12.

5.

7. The fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures according to claim 1, characterized in that: In step S3, the stress ratio of the sinusoidal load is 0.1, and the loading frequency is 5-15Hz.

8. The fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures according to claim 1, characterized in that: In step S3, during the fatigue behavior evaluation test, the maximum displacement during loading is used as the failure judgment parameter. When the maximum displacement increases by 20%, the fatigue specimen fails, and the corresponding number of cycles is the conditional fatigue life of the high-strength steel cross-welded structure.

9. The fatigue behavior evaluation method for dynamic load high-strength steel cross-welded structures according to claim 8, characterized in that, In step S3, the fatigue behavior evaluation of the high-strength steel cross-welded structure follows the following principles: If fatigue fracture occurs in areas other than the butt weld and overlay weld of the fatigue specimen, the fatigue behavior evaluation test results are considered invalid, and a new fatigue specimen needs to be prepared for a fatigue behavior evaluation test under the same load level. Complete no fewer than three fatigue behavior evaluation tests under the same load level, and introduce the conditional fatigue life deviation rate d. R To determine whether the fatigue behavior evaluation test results are valid, if the conditional fatigue life deviation rate d R If the result is ≤30%, the fatigue behavior evaluation test result is valid; otherwise, it is necessary to analyze the causes of the dispersion and re-prepare fatigue specimens for replication until d R ≤30%.

10. The method for evaluating the fatigue behavior of dynamically loaded high-strength steel cross-welded structures according to claim 9, characterized in that, In step S3, the conditional fatigue life deviation rate d R Calculated using the following formula: In the formula, d R The conditional fatigue life deviation rate is expressed in %; N min This is the minimum conditional fatigue life among the fatigue specimens in the same group, in tens of thousands of cycles; N max The maximum conditional fatigue life among the fatigue specimens in the same group, in tens of thousands of cycles; The average fatigue life of the fatigue specimens in the same group under the same conditions, in 10,000 cycles; in, n is the number of fatigue specimens in the same group, n≥3.

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