A method and device for testing the ultimate strength of reinforced plates under combined loads

Abstract

The present invention discloses a method and device for testing the ultimate strength of a stiffened plate under a combined load, obtaining a similarity relationship between a prototype model and a test model; determining a scaled relationship between the prototype model and the test model, and designing a scaled model according to the similarity relationship; designing a test model according to the scaled relationship and the similarity relationship, calculating the ultimate stress of the test model by finite element, and ensuring the relative ultimate stress of the test model and the prototype model under the same failure mode; biaxially loading the test model, and recording the test model change data; using the initial deformation and stress-strain curve of the stiffened plate, and calculating the dimensionless relative ultimate stress of the model by finite element; and determining the ultimate strength of the prototype model under the load according to the similarity relationship between the prototype model and the test model. The method solves the problem of a scaled model test method for a stiffened plate under a combined load based on a failure mode, and ensures that the displacement of the structure is not affected by mutually perpendicular biaxial compression loads.

Description

Technical Field

[0001] The invention relates to the field of ship engineering structure strength, and in particular to a method and a device for testing the ultimate strength of a stiffened plate under combined loads. Background Art

[0002] When a container ship is sailing in still water, it is usually in a mid-arch state, which will generate longitudinal compressive loads on the bottom plate. In addition, the draft will generate lateral pressure on the bottom plate. The lateral pressure will cause the bottom plate to bend and deform, which will generate additional longitudinal and lateral compressive loads. Therefore, the bottom plate structure is often subjected to the combined effects of biaxial compression and lateral pressure at the same time. The stiffened plate structure is the basic unit of the hull plate structure, so it is crucial to evaluate the ultimate strength of the stiffened plate under the combined effects of biaxial compression and lateral pressure for the safety of the hull structure.

[0003] Model testing is the most effective means of verifying theoretical analysis and numerical calculation methods. Model testing can reveal the failure mechanism of the structure, promote the further development and improvement of numerical calculation and theoretical analysis, and is an important part of structural safety design and strength assessment at this stage.

[0004] Considering the test cost and the space conditions of the laboratory, scaled models are often used for testing, but the scaled model test is required to reflect the failure mechanism of the prototype. In the existing technology, the scaled model test of the ultimate strength of the stiffened plate under the action of combined loads has many problems and challenges in the equivalent design and load application. The conventional existing technology of the ultimate strength similarity theory of stiffened plates is often only applicable to the ultimate strength test of stiffened plates under uniaxial compression, while ignoring the design method of lateral loads in scaled models, so it may not be guaranteed that the failure mode of the scaled model after the application of the combined load is consistent with the failure mode of the prototype under the combined load; when the biaxial load acts jointly, it is necessary to ensure that the biaxial loading displacement of the structure does not affect each other. In addition, it is necessary to ensure that the hydraulic cylinder always bears the axial load to avoid structural damage due to eccentric loading. Summary of the invention

[0005] The purpose of the present invention is to provide a method and a test device for the ultimate strength of a stiffened plate under a combined load to solve the above-mentioned problem, solve the scaled model test method of a stiffened plate under a combined load based on a failure mode, ensure that the displacement of the structure is not affected by mutually perpendicular biaxial compression loads, thereby realizing the ultimate strength analysis of the hull plate under the combined load, and providing strong technical support for structural design.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A method for testing the ultimate strength of a stiffened plate under combined loads comprises the following steps:

[0008] Step 1: Obtain the similarity relationship between the prototype model and the test model;

[0009] Step 2: determining the scaling relationship between the prototype model and the test model, and designing the scaled model according to the similarity relationship;

[0010] Step 3, designing the size parameters of the prototype model, and calculating the dimensionless limit stress under the prototype size parameters;

[0011] Step 4: designing a test model according to the scale relationship and similarity relationship between the prototype model and the test model, calculating the ultimate stress of the test model by finite element method, and ensuring the relative ultimate stress of the test model and the prototype model under the same failure mode;

[0012] Step 5: Compare the relative limit stress of the test model and the prototype model, and adjust the test model so that the test model meets the conditions;

[0013] Step 6: making the test model and scanning the initial deformation of the stiffened plate;

[0014] Step 7: Perform a tensile test on the material of the test model to obtain a stress-strain curve of the material;

[0015] Step 8, biaxially loading the test model and recording the change data of the test model;

[0016] Step nine, using the initial deformation of the stiffened plate in step six and the stress-strain curve in step seven to calculate the dimensionless relative limit stress of the test model using finite element method;

[0017] Step 10: Determine the ultimate strength of the prototype model under load based on the similarity relationship between the prototype model and the test model.

[0018] Preferably, the similarity relationship in step 1 includes that the flexibility coefficient of the scaled model is consistent with the flexibility coefficient of the prototype, and the dimensionless amount of the lateral pressure applied to the scaled model is consistent with the dimensionless amount of the lateral pressure applied to the prototype.

[0019] Preferably, the prototype model size parameters in step three include beam-column buckling, overall buckling, roll buckling, and web buckling.

[0020] Preferably, the test model in step 5 satisfies the condition that if the result differs by more than 10%, the size of the scaled model is readjusted until the relative limit stress error between the test model and the scaled model is less than 10%.

[0021] Preferably, the test model change data in step eight include: stress change law, displacement change law of central deformation, and axis deformation law of the specimen.

[0022] A test device for implementing the method for testing the ultimate strength of a stiffened plate under a combined load as described in the above technical solution, comprises a bracket, wherein the bracket is a right-angled quadrilateral structure, a test platform is provided in the bracket, a first bearing block is fixedly connected to one of the inner side walls of the bracket, a second bearing block is provided on the side perpendicular to the first bearing block, the second bearing block is fixedly connected to the inner side wall of the bracket, a first loading block and a second loading block are slidably connected to the top surface of the test platform, a line connecting the first loading block and the first bearing block is perpendicular to a line connecting the second loading block and the second bearing block, a longitudinal loading part is provided on the side of the first loading block away from the first bearing block, a transverse loading part is provided on the side of the second bearing block away from the second loading block, and the transverse loading part and the longitudinal loading part are respectively fixedly connected to the inner wall of the bracket.

[0023] Preferably, the test platform is fixedly connected with a first fixed plate, a second fixed plate, and a third fixed plate, the opposite inner sides of the first fixed plate and the third fixed plate are respectively fixedly connected with longitudinal slide rails, the two sides of the first loading block are slidably matched with the longitudinal slide rails, the opposite inner sides of the second fixed plate and the third fixed plate are respectively fixedly connected with transverse slide rails, and the second loading block is slidably matched with the transverse slide rails.

[0024] Preferably, a sample support bracket is fixedly connected to the inner sides of the first loading block and the first bearing block or the inner sides of the second bearing block and the second loading block, and the sample support bracket is two symmetrically arranged angle steels.

[0025] Preferably, the bracket includes a first transverse bracket, a second transverse bracket, a first longitudinal bracket, and a second longitudinal bracket. The first longitudinal bracket and the second longitudinal bracket are arranged in parallel. The first transverse bracket is fixedly connected to one end of the inner side of the first longitudinal bracket and the second longitudinal bracket. The second transverse bracket is fixedly connected to the other end of the inner side of the first longitudinal bracket and the second longitudinal bracket. The first transverse bracket and the second transverse bracket are perpendicular to the first longitudinal bracket.

[0026] The present invention has the following technical effects:

[0027] The present invention has a compact structure and a reasonable layout, and can effectively implement the application of biaxial compression loads and lateral pressure. A concentrated load is applied to the loading block through two mutually perpendicular axial loads to uniformly transmit the biaxial load. Uniform loading lateral pressure is achieved by covering the sandbag and applying weights. Combined with displacement and deformation sensors, the ultimate strength test of the scaled model of the stiffened plate under the combined action of three-dimensional loads is achieved, and the ultimate strength of the prototype under the combined action of the three-dimensional loads is obtained, providing technical support for the structural design of the stiffened plate. The test device can be widely used for the ultimate strength test of stiffened plates under the combined action of three-dimensional loads.

[0028] The length of the auxiliary tooling (square steel) connected to the longitudinal edge of the test specimen is required to exceed the width of the specimen after adding the auxiliary tooling to the transverse edge, so as to minimize the loading conflict of the loads in two mutually perpendicular directions. The additional loading blocks and slide rail blocks can effectively achieve uniform axial loading without eccentricity. The additional sandbags can effectively achieve uniform lateral pressure loading. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 It is a structural schematic diagram of the device of the present invention;

[0031] Figure 2 for Figure 1 The main view;

[0032] Figure 3 for Figure 1 Left view of

[0033] Figure 4 A partial schematic diagram of the connection between the specimen and the loading block.

[0034] Among them, 1. the first bearing block; 2. the first loading block; 3. the second bearing block; 4. the second loading block; 5. the first fixing plate; 6. the second fixing plate; 7. the third fixing plate; 8. the first transverse bracket; 9. the second transverse bracket; 10. the first longitudinal bracket; 11. the second longitudinal bracket; 12. the transverse loading part; 13. the longitudinal loading part; 14. the sample; 15. the test platform; 16. the sample support frame. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] Reference Figure 1-4 As shown, the present invention provides a method for testing the ultimate strength of a stiffened plate under a combined load, comprising the following steps:

[0038] Step 1. Based on the similarity principle of the same failure mode and the same relative ultimate stress, obtain the similarity relationship between the prototype model and the test model; the similarity relationship includes that the flexibility coefficient of the scaled model is consistent with that of the prototype, and the dimensionless quantity of the lateral pressure applied to the scaled model is consistent with that of the prototype. The similarity principle under combined load includes: the flexibility coefficient of the scaled model is consistent with that of the prototype, and the dimensionless quantity of the lateral pressure applied to the scaled model is consistent with that of the lateral pressure applied to the prototype; in the design of the scaled model, the flexibility coefficient related to the ultimate strength of the plate and the dimensionless quantity affecting the effect of the lateral pressure are considered at the same time, so that the ultimate strength of the scaled model under combined load is consistent with that of the prototype.

[0039] Step 2: Determine the scale relationship between the prototype model and the test model, and design the scale model based on the similarity relationship;

[0040] Step 3: Design the prototype model size parameters and calculate the dimensionless ultimate stress under the prototype size parameters; the prototype model size parameters include beam-column buckling, overall buckling, roll buckling, and web buckling. Design the prototype sizes for beam-column buckling, overall buckling, roll buckling, and web buckling respectively and use finite element method to calculate the corresponding dimensionless ultimate stress.

[0041] Step 4: Design the test model according to the scale relationship and similarity relationship between the prototype model and the test model, calculate the ultimate stress of the test model by finite element method, and ensure the relative ultimate stress of the test model and the prototype model under the same failure mode;

[0042] Step 5: Compare the relative ultimate stress of the test model and the prototype model. If the result differs by more than 10%, readjust the size of the scaled model until the relative ultimate stress error between the test model and the scaled model is less than 10%.

[0043] Step 6: Make a test model and scan the initial deformation of the stiffened plate;

[0044] Step 7: Perform a tensile test on the material of the test model to obtain a stress-strain curve of the material;

[0045] Step 8: Perform biaxial loading on the test model and record the test model change data; the test model change data includes: stress change law, displacement change law of central deformation, and axis deformation law of the specimen.

[0046] Step 9: Calculate the dimensionless relative limit stress of the test model using the finite element method based on the initial deformation of the stiffened plate in step 6 and the stress-strain curve in step 7;

[0047] Step 10: Based on the similarity relationship between the prototype model and the test model, determine the ultimate strength of the prototype model under load.

[0048] Based on the similarity principle of the same failure mode and the same ultimate strength, the prototype and the test model need to meet the following same flexibility coefficients:

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] Where: β p is the flexibility coefficient of the plate, b p is the panel width, t p is the strip thickness, λ ov is the overall buckling flexibility coefficient, σ ov is the overall elastic buckling stress, λ c is the beam-column buckling flexibility coefficient, σ ec is the beam-column buckling stress, β w is the web buckling flexibility coefficient, b w is the web width, t w is the web thickness, λ t is the roll buckling flexibility coefficient, σ et is the torsional buckling stress of the tendon, Q p is the dimensionless quantity of lateral pressure.

[0056] A test device for implementing the above-mentioned technical solution and a method for testing the ultimate strength of a reinforced plate under a combined load, comprises a bracket, the bracket being a right-angled quadrilateral structure, a test platform 15 being arranged inside the bracket, a first bearing block 1 being fixedly connected to one of the inner side walls of the bracket, a second bearing block 3 being arranged on a side perpendicular to the first bearing block 1, the second bearing block 3 being fixedly connected to the inner side wall of the bracket, a first loading block 2 and a second loading block 4 being slidably connected to the top surface of the test platform 15, a line connecting the first loading block 2 and the first bearing block 1 being perpendicular to a line connecting the second loading block 4 and the second bearing block 3, a longitudinal loading portion 13 being arranged on a side of the first loading block 2 away from the first bearing block 1, a transverse loading portion 12 being arranged on a side of the second bearing block 3 away from the second loading block 4, the transverse loading portion 12 and the longitudinal loading portion 13 being fixedly connected to the inner wall of the bracket, respectively.

[0057] To further optimize the solution, the test platform 15 is fixedly connected with a first fixed plate 5, a second fixed plate 6, and a third fixed plate 7, the opposite inner sides of the first fixed plate 5 and the third fixed plate 7 are respectively fixedly connected with longitudinal slide rails, the two sides of the first loading block 2 are slidably matched with the longitudinal slide rails, the opposite inner sides of the second fixed plate 6 and the third fixed plate 7 are respectively fixedly connected with transverse slide rails, and the second loading block 4 is slidably matched with the transverse slide rails.

[0058] According to a further optimization scheme, a sample support bracket 16 is fixedly connected to the inner sides of the first loading block 2 and the first bearing block 1 or the inner sides of the second bearing block 3 and the second loading block 4. The sample support bracket 16 is two symmetrically arranged angle steels.

[0059] A further optimized solution is that the bracket includes a first transverse bracket 8, a second transverse bracket 9, a first longitudinal bracket 10, and a second longitudinal bracket 11. The first longitudinal bracket 10 and the second longitudinal bracket 11 are arranged in parallel. The first transverse bracket 8 is fixedly connected to one end of the inner side of the first longitudinal bracket 10 and the second longitudinal bracket 11. The second transverse bracket 9 is fixedly connected to the other end of the inner side of the first longitudinal bracket 10 and the second longitudinal bracket 11. The first transverse bracket 8 and the second transverse bracket 9 are perpendicular to the first longitudinal bracket 10.

[0060] The specimen 14 is installed between the first bearing block 1, the first loading block 2, the second bearing block 3, and the second loading block 4. The transverse loading part 12 and the longitudinal loading part 13 can use hydraulic cylinders, and the specimen 14 is biaxially loaded through the transverse loading part 12 and the longitudinal loading part 13. The sandbag is arranged on the top surface of the specimen 14, and the weight that provides a considerable side load is arranged on the surface of the sandbag to realize the side pressure loading. By monitoring the strain of each measuring point of the test model, the stress change law under the biaxial loading state is obtained. The displacement sensor is fixed on the surface of the specimen 14 to monitor the displacement change law of the relatively large deformation position of the center of the bone material and the strip plate. By recording the axial loading load of the loading system and the axial deformation law of the specimen, the corresponding load displacement curve is drawn and the ultimate strength of the specimen is obtained. Finally, the ultimate strength of the specimen is converted into a dimensionless relative ultimate stress.

[0061] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0062] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for testing the ultimate strength of a stiffened plate under combined loads, characterized in that: The steps include: Step 1: Obtain the similarity relationship between the prototype model and the test model; Step 2: determining the scaling relationship between the prototype model and the test model, and designing the scaled model according to the similarity relationship; Step 3, designing the size parameters of the prototype model, and calculating the dimensionless limit stress under the prototype size parameters; Step 4: designing a test model according to the scale relationship and similarity relationship between the prototype model and the test model, calculating the ultimate stress of the test model by finite element method, and ensuring the relative ultimate stress of the test model and the prototype model under the same failure mode; Step 5: Compare the relative limit stress of the test model and the prototype model, and adjust the test model so that the test model meets the conditions; Step 6: making the test model and scanning the initial deformation of the stiffened plate; Step 7: Perform a tensile test on the material of the test model to obtain a stress-strain curve of the material; Step 8, biaxially loading the test model and recording the change data of the test model; Step nine, using the initial deformation of the stiffened plate in step six and the stress-strain curve in step seven to calculate the dimensionless relative limit stress of the test model using finite element method; Step 10: Determine the ultimate strength of the prototype model under load based on the similarity relationship between the prototype model and the test model.

2. The method for testing the ultimate strength of a stiffened plate under combined loads according to claim 1, characterized in that: The similarity relationship in step 1 includes that the flexibility coefficient of the scaled model is consistent with the flexibility coefficient of the prototype, and the dimensionless amount of the lateral pressure applied to the scaled model is consistent with the dimensionless amount of the lateral pressure applied to the prototype.

3. The method for testing the ultimate strength of a stiffened plate under combined loads according to claim 1, characterized in that: The prototype model size parameters in step three include beam-column buckling, overall buckling, roll buckling, and web buckling.

4. The method for testing the ultimate strength of a stiffened plate under combined loads according to claim 1, characterized in that: The test model in step 5 satisfies the condition that if the result differs by more than 10%, the size of the scaled model is readjusted until the relative limit stress error between the test model and the scaled model is less than 10%.

5. The method for testing the ultimate strength of a stiffened plate under combined loads according to claim 1, characterized in that: The test model change data in step eight include: stress change law, displacement change law of central deformation, and axis deformation law of the specimen.

6. A test device for implementing the ultimate strength test method of a stiffened plate under combined load as claimed in any one of claims 1 to 5, characterized in that: The invention comprises a bracket, wherein the bracket is a right-angled quadrilateral structure, wherein a test platform (15) is arranged inside the bracket, wherein a first bearing block (1) is fixedly connected to one inner side wall of the bracket, and a second bearing block (3) is arranged on a side perpendicular to the first bearing block (1), wherein the second bearing block (3) is fixedly connected to the inner side wall of the bracket, and a first loading block (2) and a second loading block (4) are slidably connected to the top surface of the test platform (15), wherein a line connecting the first loading block (2) and the first bearing block (1) is perpendicular to a line connecting the second loading block (4) and the second bearing block (3), wherein a longitudinal loading portion (13) is arranged on a side of the first loading block (2) away from the first bearing block (1), and a transverse loading portion (12) is arranged on a side of the second bearing block (3) away from the second loading block (4), wherein the transverse loading portion (12) and the longitudinal loading portion (13) are respectively fixedly connected to the inner wall of the bracket.

7. The test device according to claim 6, characterized in that The test platform (15) is fixedly connected with a first fixing plate (5), a second fixing plate (6), and a third fixing plate (7); the first fixing plate (5) and the third fixing plate (7) are respectively fixedly connected with longitudinal slide rails on their opposite inner sides; the first loading block (2) is slidably matched with the longitudinal slide rails on both sides; the second fixing plate (6) and the third fixing plate (7) are respectively fixedly connected with transverse slide rails on their opposite inner sides; the second loading block (4) is slidably matched with the transverse slide rails.

8. The test device according to claim 6, characterized in that: A sample support bracket (16) is fixedly connected to the inner side of the first loading block (2) and the first bearing block (1) or the inner side of the second bearing block (3) and the second loading block (4), and the sample support bracket (16) is two symmetrically arranged angle steels.

9. The test device according to claim 6, characterized in that: The bracket comprises a first transverse bracket (8), a second transverse bracket (9), a first longitudinal bracket (10), and a second longitudinal bracket (11); the first longitudinal bracket (10) and the second longitudinal bracket (11) are arranged in parallel; the first transverse bracket (8) is fixedly connected to one end of the inner side of the first longitudinal bracket (10) and the second longitudinal bracket (11); the second transverse bracket (9) is fixedly connected to the other end of the inner side of the first longitudinal bracket (10) and the second longitudinal bracket (11); the first transverse bracket (8) and the second transverse bracket (9) are perpendicular to the first longitudinal bracket (10).

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