Fixed support frame for cast steel joint fatigue test and test method

Abstract

The invention relates to the technical field of material fatigue characteristic testing, and discloses a fixed supporting frame for a cast steel joint fatigue experiment and a testing method, the fixed supporting frame is used for fixing a cast steel joint, and the fixed supporting frame comprises two vertical frames, a plurality of connecting devices and a plurality of clamping devices; the two vertical frames are parallel and arranged in the transverse direction, the multiple connecting devices are fixedly connected between the two vertical frames, one ends of the multiple clamping devices are detachably connected with the vertical frames, the other ends of the multiple clamping devices are provided with clamping pieces, and the clamping pieces are used for clamping the pipe wall of the cast steel joint and fixing the cast steel joint between the two vertical frames. The fixed supporting frame is connected with the vertical frame through the detachable clamping device, the pipe wall of the cast steel joint is directly clamped through the clamping pieces to complete fixation, a special welding transition structure does not need to be designed, and the supporting frame can adapt to cast steel joints of different specifications through the structural design; and repeated investment cost caused by disposable use loss of a special structure is reduced.

Description

Technical Field

[0001] This application relates to the technical field of testing the fatigue properties of materials, and in particular to a fixed support frame and testing method for fatigue testing of cast steel nodes. Background Technology

[0002] As a critical junction in offshore wind turbine structures, the analysis of the weak points and stress concentration conditions of cast steel nodes is crucial for assessing the reliability of these components. Accurately understanding this information provides a strong guarantee for the safe and stable operation of offshore wind turbine structures.

[0003] However, existing experimental equipment for analyzing cast steel joints has several problems. The equipment uses a welded fixing method, which requires a specially designed weld transition structure. On the one hand, this dedicated weld transition structure prevents the equipment from being reused, significantly increasing experimental costs; on the other hand, the heat generated during welding affects the local mechanical properties of the cast steel joint, thus interfering with the accuracy of experimental data and hindering a precise assessment of the reliability of the cast steel joint.

[0004] Therefore, the actual technical problem to be solved is: how to experimentally reduce costs and minimize the impact on the local mechanical properties of cast steel nodes. This has become an urgent technical problem to be solved. Summary of the Invention

[0005] The technical problem this application aims to solve is: how to experimentally reduce costs and minimize the impact on the local mechanical properties of cast steel joints.

[0006] To address the aforementioned technical problems, this application provides a fixed support frame and testing method for fatigue testing of cast steel nodes.

[0007] A first aspect of this application provides a fixed support frame for fatigue testing of cast steel nodes. The fixed support frame is used to fix the cast steel node and includes: two vertical frames that are parallel and arranged laterally; a plurality of connecting devices that are fixedly connected between the two vertical frames; and a plurality of clamping devices, one end of which is detachably connected to the vertical frame, and the other end of which is provided with a clamping plate for clamping the pipe wall of the cast steel node and fixing the cast steel node between the two vertical frames.

[0008] In one embodiment, the connecting device includes two first connecting rods, one second connecting rod, and at least two pins. The first connecting rod has a square cross-section and a plurality of pin holes arranged along its length in the radial direction. The second connecting rod has a hollow square cross-section and fixing holes are respectively provided in the radial direction at both ends. The second connecting rod is sleeved on the two first connecting rods. When the fixing holes correspond to different pin holes, the length of the first connecting rod extending beyond the second connecting rod is different, making the length of the entire connecting device different. The pins correspond one-to-one with the fixing holes and are used to limit the axial relative displacement of the first connecting rod and the second connecting rod.

[0009] In one embodiment, one end of several clamping devices is provided with a U-shaped slot. The clamping devices are detachably connected to the vertical frame through the U-shaped slot. Fastening bolts are provided on the U-shaped slot. The fastening bolts are used to adjust the assembly force between the U-shaped slot and the vertical frame, so that the clamping devices and the vertical frame can switch between an assembled state and a disassembled state. Fastening bolts are provided on the clamping plates. The fastening bolts are used to adjust the spacing of the clamping plates.

[0010] In one embodiment, the inner surface of the clamping piece is provided with staggered anti-slip textures.

[0011] In one embodiment, the vertical frame includes a cross beam, two vertical fixed columns, a horizontal fixed column, and at least two fixed discs. The fixed discs are placed horizontally, the horizontal fixed columns span across the fixed discs, the two vertical fixed columns are fixed at both ends of the horizontal fixed columns, the cross beam is fixed between the two vertical fixed columns, the uprights of the cross beam are fixed in the middle of the horizontal fixed columns, and a number of clamping devices are distributed on the cross beam around the center of the cross beam.

[0012] In one embodiment, the U-shaped slot has a first locking tooth inside, and the cross beam has a second locking tooth. The first locking tooth and the second locking tooth have the same texture direction, so that when the U-shaped slot is assembled on the cross beam, the first locking tooth and the second locking tooth mesh.

[0013] In one embodiment, the fixed disc is fixed to the mounting surface by anchor bolts.

[0014] A second aspect of this application provides a test method for fatigue testing of cast steel nodes. The test method is used for cast steel nodes fixed on a fixed support frame as provided in the first aspect of this application. The test method includes: S11, applying test loads to the cast steel node multiple times and measuring the structural stress response of the cast steel node to obtain the maximum stress within a set number of cycles; S12, selecting the stress-life curve corresponding to the maximum stress in the fatigue specification, correcting the maximum stress, and calculating the predicted fatigue life value of the cast steel node based on the corrected stress value.

[0015] In one embodiment, before step S11, the test method further includes: S21, at the offshore wind farm, continuously collecting several sets of sample data of wave height and period according to a preset sampling time interval; S22, using a probability density distribution function to fit the distribution function parameter values ​​at the offshore wind farm, and determining the corresponding probability distribution model based on the distribution function parameter values; S23, performing random sampling based on the probability distribution model to generate simulated samples that conform to the statistical laws of the probability distribution model; S24, based on the simulated samples, establishing a three-dimensional finite element model for static calculation, extracting the internal force values ​​of each component in the cast steel node, and the stress values ​​corresponding to the test load.

[0016] In one embodiment, after step S12, the test method further includes: S31, repeating steps S22 to S12 multiple times to calculate the reliability index, stopping the calculation and outputting the reliability result when the error meets the set threshold.

[0017] Compared with the prior art, the fixed support frame and test method for fatigue testing of cast steel nodes according to the embodiments of this application have the following advantages:

[0018] The fixed support frame in this embodiment is connected to the vertical frame via a detachable clamping device. The clamping plates directly clamp and fix the pipe wall, eliminating the need for a dedicated welding transition structure. This allows it to adapt to cast steel nodes of different specifications, enabling repeated use and reducing repetitive investment. Using mechanical clamping instead of welding avoids altering the local material mechanical properties of the node due to welding heat, ensuring accurate experimental data and laying the foundation for reliability analysis.

[0019] Meanwhile, the clamping device can be flexibly arranged to adapt to nodes with different pipe diameters and structures; the detachable structure facilitates quick loading and unloading, shortens preparation time, improves experimental efficiency, and the vertical frame and connecting device form a stable support. The clamping plates provide reliable fixing force to prevent node displacement and loosening, ensure stable loading, and reduce errors and operational risks. Attached Figure Description

[0020] Figure 1 This is an example illustration of a fixed support frame for fatigue testing of cast steel nodes, with an overall view showing the cast steel nodes.

[0021] Figure 2 This is an overall view of a fixed support frame for fatigue testing of cast steel nodes, as exemplarily shown in an embodiment of this application.

[0022] Figure 3 This is an exploded view of a fixed support frame used for fatigue testing of cast steel nodes, as exemplarily shown in an embodiment of this application.

[0023] Figure 4 This is a schematic diagram of a clamping device for a fixed support frame used in fatigue testing of cast steel nodes, as exemplarily shown in an embodiment of this application.

[0024] Figure 5 This is a schematic diagram of a vertical frame of a fixed support frame for fatigue testing of cast steel nodes, as exemplarily shown in an embodiment of this application.

[0025] Figure 6 This is a schematic diagram of a connection device for a fixed support frame used in fatigue testing of cast steel nodes, as exemplarily shown in an embodiment of this application.

[0026] Figure 7 The flowchart illustrates an experimental method for fatigue testing of cast steel nodes, as exemplified in an embodiment of this application.

[0027] Figure 8 This is another flowchart illustrating an experimental method for fatigue testing of cast steel nodes, as exemplarily shown in an embodiment of this application.

[0028] Figure 9 This is another flowchart illustrating an experimental method for fatigue testing of cast steel nodes, as exemplarily shown in an embodiment of this application.

[0029] Figure label:

[0030] 1. Clamping device; 2. Vertical frame; 3. Connecting device; 4. Cast steel node; 101. Clamping piece; 102. Connecting device body; 103. U-shaped slot; 104. First clamping tooth; 105. Fastening bolt; 201. Cross beam; 202. Vertical fixing column; 203. Horizontal fixing column; 204. Fixing disc; 205. Anchor bolt; 206. Connecting hole; 207. Second clamping tooth; 301. First connecting rod; 302. Fixing hole; 303. Second connecting rod; 304. Pin. Detailed Implementation

[0031] The specific embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this application, but are not intended to limit the scope of this application.

[0032] In the description of this application, it should be understood that the terms "first," "second," etc., in the specification, claims, and accompanying drawings are intended to distinguish similar objects and are not used to describe a specific structure. It should be understood that such terms are interchangeable where appropriate so that embodiments of this application can be implemented in structures other than those illustrated or described. In this application, "lateral" refers to the extending direction of the connecting device in the accompanying drawings, which is the length direction of the entire fixed support frame. Furthermore, "comprising," "having," and any variations thereof are intended to cover non-exclusive inclusions. For example, a product or device comprising a series of components or units is not necessarily limited to those explicitly listed components or units, but may also include other components or units not explicitly listed but inherent to these products or devices.

[0033] With the surge in global demand for clean energy, offshore wind power, with its abundant resources and lack of land occupation, has become an important development direction in the new energy field. However, offshore wind turbine structures operate in a complex marine environment, enduring dynamic loads such as strong winds, giant waves, and tides, placing extremely high demands on structural reliability. As a critical junction in offshore wind turbine structures, the analysis of the weak points and stress concentration conditions of cast steel nodes is crucial for assessing the reliability of these areas. Accurately understanding this information can provide strong guarantees for the safe and stable operation of offshore wind turbine structures.

[0034] However, existing experimental equipment for analyzing cast steel joints has several problems. The equipment uses a welded fixing method, which requires a specially designed weld transition structure. On the one hand, this dedicated weld transition structure prevents the equipment from being reused, significantly increasing experimental costs; on the other hand, the heat generated during welding affects the local mechanical properties of the cast steel joint, thus interfering with the accuracy of experimental data and hindering a precise assessment of the reliability of the cast steel joint.

[0035] Based on this, such as Figure 1 and Figure 2 As shown in the preferred embodiment of this application, a fixed support frame for fatigue testing of cast steel node 4 is provided. The fixed support frame is used to fix the cast steel node 4 and includes two vertical frames 2, several connecting devices 3, and several clamping devices 1.

[0036] Two vertical frames 2 are parallel and arranged laterally. Several connecting devices 3 are fixedly connected between the two vertical frames 2. Several clamping devices 1 are detachably connected at one end to the vertical frames 2, and the other end of the clamping devices 1 is provided with a clamping piece 101. The clamping piece 101 is used to clamp the pipe wall of the cast steel node 4, fixing the cast steel node 4 between the two vertical frames 2. Figure 3 or Figure 5 As shown, the connecting device 3 can be fixed by the connecting hole 206 and the pin 304 provided on the vertical frame 2.

[0037] The fixed support frame is connected to the vertical frame 2 by a detachable clamping device 1. The cast steel node 4 is directly clamped and fixed by the clamping plate 101, eliminating the need for a special welding transition structure. This structural design allows the support frame to be adapted to cast steel nodes 4 of different specifications (achieved by replacing or adjusting the clamping device 1), avoiding the one-time use wear and tear of special structures, significantly reducing the repeated investment cost of experimental equipment, and realizing the recycling of equipment.

[0038] The proposed solution abandons the traditional welding method and achieves fixation through mechanical clamping (physical contact between clamping plate 101 and the pipe wall), completely avoiding the impact of heat input during welding on the local material mechanical properties of the cast steel node 4. This design ensures that the cast steel node 4 maintains its original mechanical properties during the experiment, thereby improving the accuracy of the experimental data and providing a reliable basis for subsequent fatigue life assessment and reliability analysis.

[0039] Several clamping devices 1 can be flexibly arranged according to the structural characteristics of the cast steel node 4. The clamping plate 101 directly acts on the pipe wall for fixing, which can adapt to cast steel nodes 4 with different pipe diameters and structural forms, thus enhancing the equipment's adaptability to diverse experimental needs. At the same time, the detachable connection structure facilitates quick installation and disassembly, shortening the experimental preparation time and improving the overall experimental efficiency.

[0040] The two vertical frames 2 form a stable support structure through the connecting device 3. The clamping action of the clamping plate 101 on the pipe wall can provide a reliable fixing force, which avoids displacement or loosening of the cast steel node 4 due to load during the experiment, ensuring the stability of the loading process, reducing experimental errors, and also improving the safety of the experimental operation.

[0041] In this application, the clamping piece 101 can be an additional part fixed to the clamping device 1, or it can be a structure integrally formed on the connecting device body 102. In comparison, this application does not impose any restrictions, and both implementation methods fall within the protection scope of this application.

[0042] Furthermore, in one embodiment of this application, the connecting device 3 may employ a telescopic structure to adapt to cast steel nodes 4 of different lengths.

[0043] This application also provides an innovative retractable connection device 3, such as... Figure 6 As shown, the connecting device 3 includes two first connecting rods 301, one second connecting rod 303, and at least two pins 304.

[0044] The first connecting rod 301 has a square cross-section, and the first connecting rod 301 has a number of pin holes arranged along its length in the radial direction.

[0045] The cross-section of the second connecting rod 303 is a hollow square. Fixing holes 302 are respectively opened radially at both ends of the second connecting rod 303. The second connecting rod 303 is sleeved on the two first connecting rods 301. When the fixing holes 302 correspond to different pin holes, the length of the first connecting rod 301 extending out of the second connecting rod 303 is different, so that the length of the entire connecting device 3 is different.

[0046] The pins 304 and the fixing holes 302 correspond one-to-one and are used to limit the axial relative displacement of the first connecting rod 301 and the second connecting rod 303.

[0047] The telescopic connection device 3, through the cooperation of the first connecting rod 301, the second connecting rod 303, and the pin 304, can flexibly adjust its length to adapt to cast steel nodes 4 of different specifications. This eliminates the need for custom-designed connection structures for nodes of specific lengths, reducing customization costs and inventory requirements, and improving versatility. Its square cross-section design and pin 304 fixing method ensure convenient telescopic adjustment while achieving precise length positioning through the correspondence between different pin holes and fixing holes 302. This limits axial displacement to ensure connection stability and reliable load transfer during experiments, while also simplifying installation and adjustment procedures and improving experimental preparation efficiency.

[0048] In one embodiment, such as Figure 3 and Figure 4 As shown, one end of several clamping devices 1 is provided with a U-shaped slot 103. The clamping device 1 is detachably connected to the vertical frame 2 through the U-shaped slot 103. The U-shaped slot 103 is provided with a fastening bolt 105. The fastening bolt 105 is used to adjust the assembly force between the U-shaped slot 103 and the vertical frame 2, so that the clamping device 1 and the vertical frame 2 can switch between the assembly state and the disassembly state. The clamping piece 101 is provided with a fastening bolt 105. The fastening bolt 105 is used to adjust the spacing of the clamping piece 101.

[0049] The clamping device 1 is detachably connected to the vertical frame 2 via the U-shaped slot 103. The assembly force can be adjusted with the fastening bolt 105. This allows for quick switching between assembly and disassembly, simplifying the installation preparation before the experiment and the disassembly process after the experiment. It also ensures the stability of the connection between the clamping device 1 and the frame by tightening the bolts, preventing loosening caused by vibration during the experiment.

[0050] Meanwhile, the fastening bolts 105 on the clamping plate 101 can be flexibly adjusted in spacing, so that the clamping device 1 can be adapted to the pipe wall of the cast steel node 4 with different pipe diameters, which enhances the compatibility with diverse test pieces. There is no need to customize the clamping structure for specific specifications of nodes, which further reduces the experimental cost and improves the reusability of the equipment.

[0051] Furthermore, in one embodiment, the inner surface of the clamping piece 101 is provided with staggered anti-slip textures.

[0052] The staggered anti-slip texture on the inner surface of the clamping plate 101 increases the contact friction with the pipe wall of the cast steel node 4. The staggered design can form resistance in multiple directions, effectively suppressing the small displacement of the node caused by load vibration during the experiment, and avoiding stress measurement deviation caused by slippage. In conjunction with the adjustment function of the fastening bolt 105, it not only ensures the controllability of the clamping force, but also enhances the mechanical fixing effect through the physical texture.

[0053] In yet another embodiment of this application, such as Figure 5As shown, the vertical frame 2 includes a cross beam 201, two vertical fixed columns 202, a horizontal fixed column 203, and at least two fixed discs 204.

[0054] The fixed disc 204 is placed horizontally, the horizontal fixed column 203 spans across the fixed disc 204, the two vertical fixed columns 202 are fixed at both ends of the horizontal fixed column 203, the cross beam 201 is fixed between the two vertical fixed columns 202, the column of the cross beam 201 is fixed in the middle of the horizontal fixed column 203, and several clamping devices 1 are distributed around the center of the cross beam 201 on the cross beam 201.

[0055] The fixed disc 204 provides a stable bottom support, and the horizontal fixed column 203 and the vertical fixed column 202 form a three-dimensional load-bearing frame. Together with the cross beam 201, the horizontal beam and the vertical column construct a symmetrical force system, which can effectively disperse the load stress during the experiment and improve the deformation resistance of the overall structure.

[0056] The clamping device 1, which is distributed around the center of the cross beam 201, can accurately correspond to the multi-directional extension of the rod structure of the cast steel node 4, adapt to the connection requirements of different angles and numbers, and combined with the rigid support of the cross beam 201, ensures that the force is balanced in all directions during clamping, avoiding experimental errors caused by unstable fixing, and is especially suitable for fatigue testing scenarios of complex-configured cast steel nodes 4.

[0057] In one embodiment, the U-shaped slot 103 is provided with a first locking tooth 104 inside, and a second locking tooth 207 is provided on the cross beam 201. The first locking tooth 104 and the second locking tooth 207 have the same texture direction, so that when the U-shaped slot 103 is assembled on the cross beam 201, the first locking tooth 104 and the second locking tooth 207 engage.

[0058] The first tooth 104 inside the U-shaped slot 103 has the same texture direction as the second tooth 207 on the cross beam 201, forming an interlocking structure during assembly. This design can effectively enhance the stability of the connection between the clamping device 1 and the vertical frame 2.

[0059] The engaging teeth restrict relative sliding between the two components under load, especially in fatigue tests where repeated loads occur. This avoids the loosening problems that can occur with traditional bolt fixings, ensuring the precise positioning of the clamping device 1. Simultaneously, the engagement of the teeth and the fastening bolt 105 form a double fixation, maintaining the flexibility of disassembly while enhancing connection rigidity.

[0060] In one embodiment, the fixed disc 204 is fixed to the mounting surface by anchor bolts 205. The fixed disc 204 is fixed to the mounting surface by high-strength anchor bolts 205, which can offset the lateral or vertical forces generated by the load impact during the experiment by means of the high-strength locking force of the bolts, avoid the overall displacement or overturning of the support frame due to vibration, significantly improve the overall stability of the device, and reduce experimental errors caused by loose fixing.

[0061] The installation surface can be adapted to various scenarios such as the ground and experimental tables, which enhances the environmental adaptability of the equipment. It can be quickly deployed without the need for a special fixed foundation, further improving the flexibility and practicality of experimental operations.

[0062] Accordingly, this application also provides an assembly method for the fixed support frame: measuring the dimensions of the cast steel node 4, adjusting the length of the connecting device 3, extending the first connecting rod 301 to the appropriate length and fixing it with a pin 304, so that the longitudinal length of the fixed support frame matches the longitudinal length of the cast steel node 4; assembling the clamping device 1, pre-fitting the U-shaped slot 103 of each clamping device 1 onto the cross beam 201 of the vertical frame 2; hoisting the cast steel node 4 to the designated position of the fixed support frame, and adjusting the position of the clamping pieces 101 so that each clamping piece 101... Align the clamping plate 101 with the pipe wall of the cast steel node 4, tighten the fastening bolts 105 on the clamping plate 101 to fix the clamping plate 101 to the cast steel node 4; connect the two first connecting rods 301 of the connecting device 3 to the two vertical frames 2 respectively, and insert the pins 304 after aligning the fixing holes 302 at both ends of the second connecting rod 303 with the pin holes of the first connecting rod 301 to achieve the assembly and fixation of the overall frame; finally, connect the fixing disc 204 at the bottom of the vertical frame 2 to the mounting surface through the anchor bolts 205 to complete the overall installation of the fixed support frame.

[0063] Accordingly, this application also provides a test method for fatigue testing of cast steel node 4, the test method being used for cast steel node 4 fixed on a fixed support frame as shown in any embodiment of this application, such as... Figure 7 As shown, the test method may include:

[0064] S11. Apply test loads to cast steel node 4 multiple times and measure the structural stress response of cast steel node 4 to obtain the maximum stress within the set number of cycles.

[0065] S12. Select the stress-life curve corresponding to the maximum stress in the fatigue specification, and correct the maximum stress. Based on the corrected stress value, calculate the predicted fatigue life value of the cast steel node 4.

[0066] In one embodiment, such as Figure 8 As shown, prior to step S11, the test method may further include:

[0067] S21. At the offshore wind farm, collect several sets of wave height and period sample data continuously according to the preset sampling time interval.

[0068] S22. Using the probability density distribution function, fit the distribution function parameter values ​​at the offshore wind farm, and determine the corresponding probability distribution model based on the distribution function parameter values.

[0069] S23. Random sampling is performed based on the probability distribution model to generate simulated samples that conform to the statistical laws of the probability distribution model.

[0070] S24. Based on the simulation sample, establish a three-dimensional finite element model for static calculation, extract the internal force values ​​of each component in the cast steel node 4, and the stress values ​​correspond to the test load.

[0071] In one embodiment, such as Figure 9 As shown, after step S12, the test method may further include:

[0072] S31. Repeat steps S22 to S12 multiple times to calculate the reliability index. When the error meets the set threshold, stop the calculation and output the reliability result.

[0073] This experimental method, in conjunction with the fixed support frame of this application, has several beneficial effects:

[0074] From the perspective of the authenticity of the test load, the actual wave height and period data of the offshore wind farm were collected through steps S21-S24. Based on the probability distribution model, simulation samples were generated and internal force values ​​were calculated. This allowed the test load to be directly associated with the load characteristics of the real marine environment, avoiding the deviation between traditional empirical load assumptions and actual working conditions, and ensuring the engineering authenticity of the loading conditions.

[0075] Regarding data accuracy, the mechanical clamping and fixing method of the fixed support frame avoids the interference of welding fixing on the local mechanical properties of the cast steel node 4, so that the structural stress response measured in S11 can truly reflect the original state of the node under load; at the same time, the correction of the maximum stress in S12 (such as considering environmental, size and other factors) further conforms to the actual service conditions and improves the accuracy of fatigue life prediction.

[0076] From the perspective of result reliability, S31 effectively reduced the impact of random factors on the results through repeated sampling, loading, and life calculation, combined with reliability index evaluation and error control, making the output reliability results more statistically significant. This closed-loop design of "environmental data-driven - precise loading - statistical verification" not only ensures the consistency between the test process and the actual service environment, but also improves the credibility of fatigue life assessment through quantitative analysis, providing reliable technical support for the safety design and life prediction of offshore wind turbine cast steel node 4.

[0077] In the above experimental steps, the following detailed steps, exemplified by this application, can be used:

[0078] 6.1 At the offshore wind power service site, continuously collect x sets of sample data of wave height H and period T at a preset sampling time interval Δt;

[0079] 6.2. Using the wave height-period joint probability density distribution function fN(H,T) based on the Wallops spectrum, fit the distribution function parameter values ​​of the service location;

[0080] 6.3. Random sampling is achieved by randomly generating the sampling results of wave height H and period T that conform to the joint probability density distribution function fN(H,T) in step 6.2 based on the Monte Carlo method.

[0081] 6.4 Input the extracted wave height H and period T samples into the marine engineering calculation software to perform static calculations on cast steel node 4; extract the internal force values ​​on each member of cast steel node 4;

[0082] 6.5 Apply the corresponding test load calculated in step 6.4 to the node specimen, and measure the stress of the structure by strain gauges. Select the maximum stress measurement result Smax (maximum stress) as the life assessment.

[0083] 6.6 Select the corresponding SN curve (stress-life curve) in the DNV specification (Det Norske Veritas specification), substitute it into Smax (maximum stress), and calculate the predicted fatigue life value.

[0084] 6.7 Repeat steps 6.3 to 6.6 a total of n times to obtain n sets of fatigue life prediction value samples. When performing the (n+1)th repetition, if the absolute error between the reliability obtained from the (n+1)th set of samples and the reliability obtained from the nth set of samples is less than 0.001, output the reliability analysis results.

[0085] This application focuses on the fixed support frame and test method for fatigue testing of cast steel node 4: The fixed support frame includes a vertical frame 2 with a cross beam 201, a telescopic connecting device 3, and a clamping device 1 with a U-shaped slot 103 (including clamping teeth) and anti-slip textured clamping plate 101, which is fixed to the mounting surface by anchor bolts 205. It can be flexibly adjusted to adapt to different nodes during assembly; The test method covers the complete process of marine environmental data acquisition, probabilistic modeling sampling, finite element calculation of internal forces, loading and stress measurement, calculation of life combined with SN curves, and repeated verification of reliability.

[0086] The beneficial effects of the embodiments of this application are significant: the fixed support frame, through its detachable and adjustable design, avoids welding losses and heat effects, reduces costs, is recyclable, adapts to various nodes, and ensures stable fixation. The experimental method combines real environmental load simulation and stress correction to improve data accuracy, and multiple sampling verifications enhance the reliability of the results, providing efficient and accurate technical support for node fatigue assessment.

[0087] The above are merely preferred embodiments of this application. It should be noted that, for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application.

Claims

1. A fixture support for cast steel node fatigue experiments, characterized by, The fixed support frame is used for fixing a cast steel node (4), and comprises: Two vertical frames (2) arranged in parallel along the transverse direction; A plurality of connecting devices (3) fixedly connected between the two vertical frames (2); A plurality of clamping devices (1), one end of each clamping device (1) being detachably connected with the vertical frame (2), the other end of each clamping device (1) being provided with a clamping piece (101) for clamping a pipe wall of the cast steel node (4) to fix the cast steel node (4) between the two vertical frames (2).

2. The fixed support bracket of claim 1, wherein The connecting device (3) comprises two first connecting rods (301), a second connecting rod (303), and at least two pins (304); The first connecting rod (301) has a square cross section, and a plurality of pin holes arranged in the length direction are formed in the radial direction of the first connecting rod (301); The second connecting rod (303) has a hollow square cross section, and a fixing hole (302) is formed in the radial direction of each end of the second connecting rod (303), the second connecting rod (303) being sleeved on the two first connecting rods (301), the lengths of the first connecting rods (301) extending out of the second connecting rod (303) being different when the fixing holes (302) correspond to different pin holes, so that the length of the entire connecting device (3) is different; The pin (304) corresponds to the fixing hole (302) one-to-one, and is used for limiting the axial relative displacement of the first connecting rod (301) and the second connecting rod (303).

3. The fixed support bracket of claim 1, wherein One end of each clamping device (1) is provided with a U-shaped clamping groove (103), the clamping device (1) being detachably connected with the vertical frame (2) through the U-shaped clamping groove (103), a fastening bolt (105) being arranged on the U-shaped clamping groove (103), the fastening bolt (105) being used for adjusting the assembly force of the U-shaped clamping groove (103) and the vertical frame (2) to switch the clamping device (1) and the vertical frame (2) between the assembly state and the disassembly state, the fastening bolt (105) being arranged on the clamping piece (101) and used for adjusting the spacing of the clamping piece (101).

4. The fixed support bracket of claim 3, wherein, The inner surface of the clamping piece (101) is provided with staggered anti-skid lines.

5. The fixed support bracket of claim 3, wherein The vertical frame (2) comprises a cross beam (201), two vertical fixed columns (202), a transverse fixed column (203) and at least two fixed discs (204), the fixed disc (204) is horizontally placed, the transverse fixed column (203) is transversely arranged on the fixed disc (204), the two vertical fixed columns (202) are fixed at two ends of the transverse fixed column (203), the cross beam (201) is fixed between the two vertical fixed columns (202), and the vertical column of the cross beam (201) is fixed at the middle of the transverse fixed column (203); a plurality of clamping devices (1) are distributed on the cross beam (201) around the center of the cross beam (201).

6. The fixed support bracket of claim 5, wherein, The inside of the U-shaped clamping groove (103) is provided with a first clamping tooth (104), and the cross beam (201) is provided with a second clamping tooth (207); the texture directions of the first clamping tooth (104) and the second clamping tooth (207) are the same, so that when the U-shaped clamping groove (103) is assembled on the cross beam (201), the first clamping tooth (104) and the second clamping tooth (207) are engaged.

7. The fixed support bracket of claim 5, wherein, The fixed disc (204) is fixed on the mounting surface through an anchor bolt (205).

8. A test method for cast steel node fatigue experiments, characterized by, The test method is used for the cast steel node (4) fixed on the fixing support frame as claimed in any one of claims 1-7, and the test method comprises: S11, repeatedly applying a test load to the cast steel node (4), measuring a structural stress response of the cast steel node (4), and obtaining a maximum stress within a set number of cycles; S12, selecting a stress-life curve corresponding to the maximum stress in a fatigue specification, correcting the maximum stress, and calculating a fatigue life prediction value of the cast steel node (4) based on the corrected stress value.

9. The test method of claim 8, wherein, Before step S11, the test method further comprises: S21, continuously collecting a plurality of groups of sample data of wave height and period at a preset sampling time interval at the offshore wind farm; S22, fitting a distribution function parameter value of the offshore wind farm using a probability density distribution function, and determining a corresponding probability distribution model based on the distribution function parameter value; S23, generating simulation samples conforming to the statistical law of the probability distribution model based on the probability distribution model; S24, establishing a three-dimensional finite element model for static force calculation according to the simulation samples, and extracting an internal force value of each component in the cast steel node (4), wherein the stress value corresponds to the test load.

10. The test method of claim 9, wherein, After step S12, the test method further comprises: S31, repeatedly performing steps S22 to S12 for multiple times, calculating a reliability index, and stopping calculation and outputting a reliability result when an error meets a set threshold.

Images