Anti-eccentric loading tool device for stiffened plate axial loading test

Abstract

The invention discloses an anti-eccentric loading tool device for an axial loading test of a stiffened plate. The device belongs to the technical field of ship and ocean engineering structure tests and is composed of a stiffened plate test piece, a steel head assembly, an end loading clamp, a side clamp and a supporting base. The steel head is welded to the end of the stiffened plate according to the neutralizing shaft, the loading clamp is adopted for clamping, it is ensured that loading force acts along the neutralizing shaft of the stiffened plate, and end face bending moment is avoided; meanwhile, adjustable clamps are arranged on the two sides of the stiffened plate, flexible adjustment and clamping are conducted according to the position of the test piece, accurate simulation of the four-side simple support boundary conditions is achieved, and the loading precision and the test reliability are improved; according to the invention, high-precision loading path control and real boundary condition reproduction are realized through a fixed loading end, centering steel head welding, an adjustable side clamp and a rigid base; the device can prevent loading eccentricity, eliminate end face bending moment and improve loading precision and repeatability; and meanwhile, the device is suitable for buckling and ultimate bearing capacity tests of different types of stiffened plates.

Description

Technical Field

[0001] This invention belongs to the field of ship and marine engineering structural testing technology, and relates to an anti-eccentric loading fixture for axial loading tests of stiffened plates. Background Technology

[0002] Stiffened plate structures are widely used in pressure-bearing structures such as ship hulls, tanks, decks, and shells, and their mechanical properties directly affect the overall strength and reliability of the entire ship or equipment. To study the buckling mode, ultimate bearing capacity, and instability mechanism of stiffened plates under axial compression, axial loading tests are typically conducted. However, in actual tests, due to the complex geometry of the stiffened plates, uneven end faces caused by welding processes, assembly errors in the specimens, and inaccurate positioning of the loading device, a deviation often occurs between the loading axis and the neutral axis of the stiffened plate, resulting in loading eccentricity.

[0003] Eccentric loading causes uneven stress distribution at both ends of the specimen, resulting in additional bending moments at the stiffened plate ends. This alters the actual stress state of the structure, significantly affecting the location of buckling modes and the magnitude of critical loads, causing test results to deviate from the true stress characteristics. Furthermore, eccentric loading may induce asymmetric deformation, exacerbating premature buckling on the stiffener side, leading to poor test repeatability, large dispersion in ultimate bearing capacity, and in severe cases, even test failure.

[0004] Existing loading fixtures are mostly rigid clamping structures with fixed clamping positions and low centering accuracy, making it difficult to accurately adjust for stiffened plates of different shapes or sizes. When the neutral axis of the specimen does not coincide with the loading axis, existing fixtures cannot effectively correct this, resulting in end face bending moments during the test. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide an anti-eccentric loading fixture for axial loading tests of stiffened plates that can achieve precise alignment during the experimental installation phase, ensure that the load force is transmitted through the neutral axis, and avoid eccentricity effects.

[0006] Technical solution: The anti-eccentric loading fixture for axial loading test of stiffened plate described in this invention includes four support bases (4) with mounting grooves and positioning holes. A lower end constraint clamp (2) is installed on the support base (4) on the bottom side and between the two supporting bases (4) standing on the bottom side. The bottom end of the lower end constraint clamp (2) is movably installed on the support base (4) on the bottom side by the installed bolts, and its two sides are movably installed on the two supporting bases (4) standing on the two sides by the installed bolts.

[0007] Furthermore, a hydraulic cylinder (5) and an upper loading clamp (1) are installed inside the upper side of the two standing support bases (4).

[0008] Furthermore, the upper loading fixture (1) is connected to the loading head of the hydraulic cylinder (5); the hydraulic cylinder (5) is wirelessly controlled by the monitoring host.

[0009] Furthermore, a stiffening plate (7) is installed between the upper loading clamp (1) and the lower constraint clamp (2), and between the two standing support bases (4).

[0010] Furthermore, the stiffening plate (7) is composed of a base plate and longitudinal or transverse reinforcing ribs, and different types of stiffening plates (7) correspond to different neutral axis positions.

[0011] Furthermore, a steel head (6) is welded to the loading end of the stiffening plate (7) according to the neutral axis position of the stiffening plate (7).

[0012] Furthermore, the steel head (6) is made of the same material as the stiffening plate (7), and its size matches the clamp at the loading end of the stiffening plate (7). Its end face is machined to ensure flatness and parallelism.

[0013] Furthermore, adjustable side clamps (3) are installed on the left and right sides of the stiffening plate (7) and on the inner walls of the two supporting bases (4) that stand upright. The side clamps (3) on both sides are movably mounted on the two standing support bases (4) by the installation bolts.

[0014] Furthermore, the side clamp (3) adopts a long strip groove and through hole structure, which is adjusted and locked according to the moving position of the stiffening plate (7).

[0015] Furthermore, the tooling device is mounted entirely on a rigid loading frame.

[0016] The structural design of this device can accurately simulate the simply supported boundary conditions on all four sides during the experiment, and ensure that the loading force acts strictly along the neutral axis of the stiffening plate, thereby avoiding the end face bending moment caused by loading eccentricity. By welding steel heads to the ends of the stiffening plate according to the neutral axis and using loading fixtures to hold them, it is ensured that the loading force acts along the neutral axis of the stiffening plate, avoiding the generation of end face bending moment. At the same time, adjustable fixtures are set on both sides of the stiffening plate, which can be flexibly adjusted and clamped according to the position of the specimen, thereby realizing the accurate simulation of the simply supported boundary conditions on all four sides, improving the loading accuracy and experimental reliability.

[0017] Beneficial Effects: Compared with the prior art, the present invention has the following significant advantages: 1. Prevents eccentric loading and eliminates end-face bending moment: By welding the steel head and cooperating with the loading end clamp, the loading force acts along the neutral axis of the stiffening plate, effectively avoiding eccentric loading and eliminating the interference of the additional end-face bending moment on buckling behavior; 2. Realizes simulation of realistic boundary conditions: Through the combined design of fixed loading end, adjustable sides, and four-sided clamping, high-precision reproduction of simply supported boundary conditions on four sides is achieved, making the experimental results closer to the actual stress state of the structure; 3. Flexible adjustable clamp structure design: The structure with long strip grooves and through holes allows the clamp to be flexibly adjusted according to the change of the neutral axis of the specimen. After adjustment, it can be firmly locked to ensure stable and reliable boundary conditions; 4. Significantly improved loading accuracy and repeatability: The fixed loading end position and the adjustable steel head welding position ensure that different specimens are subjected to consistent forces under the same loading path, improving test repeatability and data comparability; 5. Simple structure, strong versatility, and convenient adjustment: The fixture consists of standardized clamps, slides, and bolt structures, which are simple to manufacture and easy to assemble. It can be adapted to stiffened plates of different forms and sizes and has strong engineering application and promotion value. This invention achieves high-precision loading path control and reproduction of real boundary conditions through the design of "fixed loading end + centering steel head welding + adjustable side clamp + rigid base". This fixture can effectively prevent loading eccentricity, eliminate end face bending moment, and improve loading accuracy and repeatability; at the same time, it is suitable for buckling and ultimate bearing capacity tests of different types of stiffened plates, and has the advantages of simple structure, convenient installation, and strong versatility. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the upper loading fixture in this invention; Figure 3 This is a schematic diagram of the lower end constraint fixture in this invention; Figure 4 This is a schematic diagram of the structure in this invention where the steel head is welded to the loading end of the stiffening plate according to the neutral axis position; Figure 5 This is a side view of the welded steel head of the stiffening plate in this invention; Figure 6 This is a schematic diagram of the side clamp in this invention; In the diagram, 1 is the upper loading fixture, 2 is the lower constraint fixture, 3 is the side fixture, 4 is the support base, 5 is the hydraulic cylinder, 6 is the steel head, and 7 is the stiffening plate. Detailed Implementation

[0019] The specific technical solution of the present invention will be further described in detail below with reference to specific examples.

[0020] As shown in the figure, the anti-eccentric loading fixture for axial loading test of stiffened plate according to the present invention mainly includes stiffened plate 7, steel head 6, loading end clamp, adjustable side clamp 3 and support base 4; this fixture can realize the axial loading force neutralizing the axial action through stiffened plate 7 in the test, and simulate simply supported boundary conditions through four-sided clamp, thereby ensuring the loading accuracy and consistency with the test.

[0021] Specifically: 1. Stiffened plate specimen (stiffened plate 7) The stiffened plate specimen is the core component of the test, consisting of a base plate and longitudinal or transverse stiffeners, which can be flat steel bars, angle steel bars, or T-shaped bars, etc. Different forms (such as flat steel bars, angle steel bars, and T-shaped bars) correspond to different neutral axis positions. The neutral axis position also varies depending on the length, width, height and stiffening form of the specimen. In the test, the stiffened plate 7 bears axial compressive load, and its four sides are constrained by clamps to simulate the simply supported boundary conditions on four sides. Steel head assembly (steel head 6) At the loading end of stiffening plate 7, a steel head assembly (steel head 6) is welded according to the neutral axis position of the specimen (stiffening plate 7). The steel head 6 is made of the same material as stiffening plate 7, and its thickness and width match the loading end fixture. The end face of steel head 6 is machined to ensure flatness and perpendicularity, ensuring that the loading force does not shift during transmission. By welding steel head 6 to stiffening plate 7, the loading force can be accurately applied along the neutral axis direction and transmitted to the neutral axis position of stiffening plate, thereby avoiding the additional bending moment caused by loading eccentricity. For different stiffening plates 7, the neutral axis position is different, so the welding position of steel head 6 is also adjusted accordingly to ensure that the loading force line of each specimen coincides with the neutral axis. 3. End loading fixture The end loading fixture includes an upper loading fixture 1 and a lower constraint fixture 2, collectively referred to as the end loading fixture; it is installed as a whole in a rigid loading frame; the upper loading fixture 1 is connected to the loading head of the hydraulic cylinder 5 through a connecting seat, and its position remains fixed, used to apply axial loading force to the specimen; the fixture structure has sufficient rigidity to withstand axial compressive force and prevent deformation; during the test, the end of the stiffening plate 7 is welded with a steel head 6 according to its neutral axis position, and the steel head 6 is inserted into the upper loading fixture 1 and clamped, so as to realize the uniform transmission of loading force along the neutral axis of the stiffening plate 7; The lower constraint fixture 2 is fixedly installed on the loading frame base to provide symmetrical support and simulate simply supported boundary conditions and reaction force transmission; the hydraulic cylinder (cylinder 5) serves as the loading power source and can provide stable axial compressive force; during the test loading, the piston rod of the cylinder 5 presses down in the vertical direction, driving the loading head to drive the upper loading fixture 1 to apply axial load to the specimen; since the neutral axis positions of different specimens are different, the welding position of the steel head 6 can be adjusted according to the specimen structure, while the positions of the end loading fixture and the loading head of the cylinder 6 remain fixed, ensuring that different stiffening plates 7 are subjected to consistent forces under the same loading path, thus achieving the unification of loading conditions; During the loading process, the upper loading clamp 1 is axially loaded under the push of the hydraulic cylinder 5, and the lower constraint clamp 2 provides reaction force support. Together, they form a stable loading system. Unlike traditional rigid loading devices, the end loading clamp of this invention does not need to move with the position of the stiffening plate 7. Instead, the loading is aligned by adjusting the welding position of the steel head 6, thereby ensuring that the loading end position is fixed and the loading path is uniform, which significantly improves the symmetry, repeatability and consistency of the test loading. 4. Adjustable side clamps 3 To achieve true boundary constraints for the simply supported four sides of the stiffening plate 7, this invention provides adjustable side clamps 3 on both sides of the stiffening plate 7. The side clamps 3 are mounted on the support base 4 via a sliding guide structure and can move laterally along the stiffening plate 7. A long, narrow through-hole is provided in the sliding groove, and the clamps are connected to the base by bolts. The bolts pass through the through-hole and are then locked by nuts. When the overall position of the stiffening plate 7 changes due to different neutral axis positions of different specimens, the operator can adjust the position of the clamps in the sliding groove to re-fit the sides of the specimen, and then tighten the bolts to secure it. This design ensures that the stiffening plate 7 at different neutral axis positions can be reliably... The clamping mechanism maintains the same simply supported boundary conditions. This structure achieves a functional balance of "adjustable-locking-stable," meaning that the clamp can slide flexibly during the adjustment phase and forms a high-rigidity constraint after locking, ensuring that no relative slippage occurs during the test. Specifically, when the overall installation position of the stiffening plate 7 shifts due to changes in the neutral axis position, the side clamp 3 can be finely adjusted along the transverse guide rail to ensure reliable clamping of the side of the stiffening plate 7, maintaining the consistency of the simply supported boundary conditions and the stability of the stress. The adjustable side clamp 3 adopts a long strip-shaped sliding groove and through-hole structure, which can be flexibly adjusted and locked in place according to the moving position of the stiffening plate 7. 5. Support base 4 The tooling is installed on a rigid loading frame. The support base 4 is provided with fixture mounting slots and positioning holes to ensure the positional accuracy and symmetry of each fixture in the loading direction (geometric position). The support base 4 is used to install each fixture and provide overall rigid support. The support base 4 is made of thick steel plate welded or integrally machined, and has high bending stiffness to ensure that the whole does not deform during loading.

[0022] Through the above structural design, the present invention achieves the following functional characteristics during the test: the welding of the steel head 6 ensures that the loading force is aligned with the neutral axis of the stiffening plate 7, eliminating eccentric loading; the clamping of the four-sided clamps achieves the simple-supported boundary constraint when the stiffening plate 7 is under pressure; the adjustable design of the side clamps 3 compensates for the positional changes caused by the difference in the neutral axis of the specimen, ensuring the installation accuracy of the specimen; and it ensures that the loading conditions remain consistent in multiple sets of tests, improving the comparability and repeatability of the test results.

[0023] The working process of this device is as follows: Before the test, the position of the neutral axis is determined according to the geometric characteristics of the stiffening plate 7, and the steel head 6 is welded at the corresponding position; then the specimen is placed in the fixture, and the steel head 6 is clamped with the end loading fixture. At the same time, the two side fixtures are adjusted to move along the slide to the appropriate position and bolted to achieve four-sided simply supported constraint; during the loading process, the loading head of the hydraulic cylinder 6 applies a load downward, and the force is transmitted to the neutral axis of the stiffening plate 7 through the steel head 6. The plate edge is constrained by the fixture to form a simply supported boundary, thereby realizing the axial loading test under real stress state; throughout the loading process, each fixture remains stable and does not shift or rotate, ensuring the reliability of the test data.

[0024] In summary, the anti-eccentric loading fixture of this invention achieves high-precision loading path control and reproduction of real boundary conditions through a comprehensive design of "steel head centering welding + fixed loading end clamp + adjustable side clamp". This fixture effectively prevents loading eccentricity, eliminates end face bending moment, and improves loading accuracy and repeatability; it is also suitable for buckling and ultimate bearing capacity tests of different types of stiffened plates, and has the advantages of simple structure, convenient installation, and strong versatility.

Claims

1. An anti-eccentric loading fixture for axial loading tests of stiffened plates, characterized in that, It includes four support bases (4) with mounting grooves and positioning holes. A lower end constraint clamp (2) is installed on the support base (4) on the bottom side and between the two standing support bases (4). The bottom end of the lower end constraint clamp (2) is movably installed on the support base (4) on the bottom side by installation bolts, and its two sides are movably installed on the two standing support bases (4) on both sides by installation bolts.

2. The anti-eccentric loading fixture for axial loading tests of stiffened plates according to claim 1, characterized in that, A hydraulic cylinder (5) and an upper loading clamp (1) are installed inside the upper side of the two standing support bases (4).

3. The anti-eccentric loading fixture for axial loading tests of stiffened plates according to claim 2, characterized in that, The upper loading clamp (1) is connected to the loading head of the hydraulic cylinder (5); the hydraulic cylinder (5) is wirelessly controlled by the monitoring host.

4. The anti-eccentric loading fixture for axial loading tests of stiffened plates according to claim 2, characterized in that, A stiffening plate (7) is also installed between the upper loading clamp (1) and the lower constraint clamp (2) and between the two standing support bases (4).

5. The anti-eccentric loading fixture for axial loading tests of stiffened plates according to claim 4, characterized in that, The stiffening plate (7) is composed of a base plate and longitudinal or transverse stiffeners, and different types of stiffening plates (7) correspond to different neutral axis positions.

6. The anti-eccentric loading fixture for axial loading tests of stiffened plates according to claim 5, characterized in that, A steel head (6) is welded to the loading end of the stiffening plate (7) according to the neutral axis position of the stiffening plate (7).

7. The anti-eccentric loading fixture for axial loading tests of stiffened plates according to claim 6, characterized in that, The steel head (6) is made of the same material as the stiffening plate (7), and its size matches the clamp at the loading end of the stiffening plate (7). Its end face is machined to ensure flatness and parallelism.

8. The anti-eccentric loading fixture for axial loading tests of stiffened plates according to claim 4, characterized in that, Adjustable side clamps (3) are also installed on the inner walls of the two supporting bases (4) on the left and right sides of the stiffening plate (7); the side clamps (3) on both sides are movably installed on the two supporting bases (4) by bolts.

9. The anti-eccentric loading fixture for axial loading tests of stiffened plates according to claim 8, characterized in that, The side clamp (3) adopts a long strip groove and through hole structure, which is adjusted and locked according to the moving position of the stiffening plate (7).

10. The anti-eccentric loading fixture for axial loading tests of stiffened plates according to claim 1, characterized in that, The tooling device is mounted as a whole on a rigid loading frame.

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