Photovoltaic carbon fiber cable small cable clamp design and transverse stress inversion type test method

Abstract

The invention relates to the technical field of photovoltaic cable clamps, and provides a photovoltaic carbon fiber cable small cable clamp design and transverse stress inverted test method, which comprises the following steps: S1, test piece installation; s2, pre-tightening an inhaul cable; s3, test loading is carried out; in a flexible photovoltaic support project, transverse force is conducted downwards to a photovoltaic pressing block through a photovoltaic panel, the pressing block is conducted downwards to a small cable clamp, a cable clamp clamping seat presses a carbon fiber cable body downwards, a height-adjustable test platform is additionally arranged in the middle of the test stroke of a horizontal tension tester, and the test precision is improved. By changing the bending angle and the axial tension of the carbon fiber cable body, loading of given transverse force can be achieved, according to the scheme, original vertical downward transverse force application is changed into vertical upward jacking, meanwhile, the opening of the cable clamp clamping base is installed upwards, the carbon fiber cable body is still pressed by the arc-shaped notch of the cable clamp clamping base, real engineering stress is not changed, and the carbon fiber cable body can be firmly fixed through the arc-shaped notch of the cable clamp clamping base. And meanwhile, additional arrangement of a jack and a counter-force frame is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of photovoltaic cable clamps, in particular to a design of a small-sized cable clamp for a photovoltaic carbon fiber cable and a transverse force inverted test method. Background Art

[0002] Photovoltaic construction is an important part of the national new energy strategy. Flexible photovoltaic brackets are favored by more and more projects due to their strong adaptability, convenient installation and high cost-effectiveness. Such brackets can better adapt to complex terrain and improve the power generation efficiency of photovoltaic panels. Their main load-bearing components are mostly large-span steel cables; but large-span steel cables require additional anti-corrosion measures and are sensitive to temperature changes. Carbon fiber composites have shown broad application prospects in many fields with their advantages of light weight, high strength, corrosion resistance and good thermal stability. In the construction field, carbon fiber cables have excellent performance in structures with large spans and heavy loads due to their excellent specific strength and specific modulus. They have been used in large-span bridge construction and are very promising for application in large-span buildings and new energy facilities.

[0003] In the connection between photovoltaic panels and cable bodies, steel cable bodies and cable clamps are usually fastened with U-bolts and other methods. However, this cable clamp is still far from the use of carbon fiber cables:

[0004] 1. The lateral force performance of the carbon fiber cable body is poor. When using carbon fiber cables, special attention should be paid to the extrusion problem between the cable body and the cable clamp. The existing photovoltaic steel cable clamp has no additional protective structure for the carbon fiber cable. Although forced pressing can achieve fastening, it is very likely to damage the carbon fiber cable body and affect the structural force safety. In order to reduce the potential damage of this lateral force to the carbon fiber cable, additional protective sheaths are often added at the connection nodes in engineering practice, and the sheath becomes the main source of increasing the overall size of the cable clamp. However, the additional sheath will be used in conjunction with the cable clamp at the connection between each photovoltaic panel and the carbon fiber cable, and the number of cables used is large. Under this background, the miniaturization of the cable clamp size is particularly important for the construction of photovoltaic brackets. Miniaturized cable clamps can not only reduce material consumption and reduce costs, but also improve the convenience and flexibility of installation, especially in places where space is limited or lightweight design is pursued. Therefore, the development of new cable clamps that can effectively protect the carbon fiber cable from damage and achieve miniaturization of the cable clamp size has become the key to promoting the advancement of photovoltaic bracket technology.

[0005] 2. In addition to the axial force of the cable body, the carbon fiber cable is also subjected to lateral forces such as the weight of the photovoltaic panel and wind load at the cable clamp. It is necessary to conduct supporting test analysis in combination with the structural force. However, the conventional test design of the stress performance of such specimens often adds a reaction frame and combines longitudinal and transverse jacks and other power devices for loading, which is relatively cumbersome and fails to effectively apply conventional test equipment such as horizontal tensile machines; in addition, the cable clamps used in the field of construction engineering are complex in structure and large in size, which cannot meet the characteristics of light and quick installation of flexible photovoltaic brackets. Summary of the invention

[0006] The present invention provides a design of a small cable clamp for photovoltaic carbon fiber cables and an inverted lateral force test method. The small cable clamp can disperse the extrusion effect caused by the cable clamp and protect the carbon fiber cable body. The matching test method is combined with an optimized test device to realize the testing of the bending angle, axial tension and lateral force performance of the cable clamp node, so as to solve the problems raised in the background technology.

[0007] The technical solution of the present invention is as follows:

[0008] A method for testing a small-sized photovoltaic carbon fiber cable clip under lateral force inversion comprises the following steps:

[0009] S1. Specimen installation: Both ends of the carbon fiber cable body are connected to the horizontal tensile testing machine through conventional hinged anchors. A small cable clamp is provided in the middle of the carbon fiber cable, which is fixed on a height-adjustable test platform. The fastening method of the carbon fiber cable and the small cable clamp is consistent with engineering applications. The U-shaped stud clamps the split sheath downward, passes through the cable clamp seat, and is fastened with a nut on the back of the slider top plate;

[0010] S2. Cable pretensioning: Operate the horizontal tensile testing machine, tension the carbon fiber cable to 30% of the designed pretension (the ratio is adjustable), and check the status of each component in the test system;

[0011] S3. Test loading: operate the horizontal tensile testing machine, and load the carbon fiber cable in stages to 30%, 50%, 70%, 80%, 90%, and 100% of the designed pre-tension of the carbon fiber cable. Observe and record the status of the carbon fiber cable, small cable clamp, and various components in the test system in each loading stage: ① Whether the carbon fiber cable and small cable clamp are damaged; ② Whether the working status of various components in the loading system is normal; and obtain the force-displacement curve of the whole process of the horizontal tensile testing machine.

[0012] Furthermore, the carbon fiber cable body in S1 is composed of a carbon fiber composite core material and an outer sheath.

[0013] As a technical solution of the present invention, the small cable clamp consists of a cable clamp holder, a U-shaped stud, a split protective sleeve and a fastening nut, which can effectively disperse the lateral force of the carbon fiber cable and reduce the damage to the carbon fiber cable; the structure is simple and compact, and it is easy to operate.

[0014] Furthermore, a slider is provided on the top of the height-adjustable test platform in S1, and the slider is restricted by blocking plates on both sides. A cable clamp mounting hole is provided on the top of the slider, and a small cable clamp is connected to the cable clamp mounting hole and locked by a fastening nut.

[0015] A design method for a small cable clamp of a photovoltaic carbon fiber cable, the use steps of which are as follows:

[0016] T1. Based on the lateral force of the small cable clamp and the diameter of the carbon fiber cable, a preliminary design of a segmented protective cover is made. In this preliminary design, the segmented protective cover is a regular semi-cylinder.

[0017] T2. Based on the stress condition of the sliced ​​protective sleeve, the topology optimization method is used, with the minimum strain energy as the objective function and the volume reduction as the constraint condition to update the shape of the original sliced ​​protective sleeve;

[0018] T3. Perform stress analysis on the updated piece-type protective cover through finite element analysis. If the requirements are not met, adjust the constraints and repeat T2 until they are met and a piece-type protective cover that meets the requirements is obtained.

[0019] Furthermore, the constraint conditions in T2 may also include chamfering the edge of the sliced ​​protective cover to avoid scratching the outer cover.

[0020] Furthermore, the sliced ​​protective cover is made of stainless steel.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention adds a split-piece protective cover in the small cable clamp, so that the U-shaped stud and the cable clamp seat are no longer in direct contact with the carbon fiber cable, but are first inserted into the stainless steel casing outside the carbon fiber cable, so that the contact between the small cable clamp and the carbon fiber cable is changed from the original point contact to a surface contact within a certain range, thereby increasing the force-bearing area of ​​the lateral force of the carbon fiber cable, effectively alleviating the adverse effect of the lateral force on the carbon fiber cable, and helping to ensure the safety of the structure; and the miniaturized cable clamp can save material consumption, reduce construction work intensity, and increase construction speed.

[0023] 2. The present invention can effectively reduce the size of the small cable clamp and its connection nodes with the photovoltaic panel and the carbon fiber cable through the miniaturized design of the split-piece protective cover, thereby reducing the material usage by nearly 50%, reducing the weight of a single part, facilitating transportation and construction.

[0024] 3. In the flexible photovoltaic bracket project, the present invention transmits the lateral force downward to the photovoltaic pressure block through the photovoltaic panel, and the pressure block transmits the force downward to the small cable clamp. The cable clamp holder presses the carbon fiber cable downward (the arc-shaped groove of the cable clamp holder is downward). The laboratory horizontal tensile testing machine can only stretch the carbon fiber cable in the horizontal direction. The vertical downward loading needs to be combined with the reaction frame to increase the jack loading. The vertical upward loading space is limited and it is difficult to add a jack. For this reason, a height-adjustable test platform is added in the middle of the test stroke of the horizontal tensile testing machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a three-dimensional diagram of the carbon fiber rope and the sliced ​​protective cover in the present invention;

[0026] Figure 2 is a cross-sectional view of the carbon fiber rope and the sliced ​​protective cover in the present invention;

[0027] Figure 3 It is a front view of the installation of the small and medium-sized cable clamp of the present invention;

[0028] Figure 4 It is a detailed diagram of the sliced ​​protective cover in the present invention;

[0029] Figure 5 It is a side view of the installation of the small and medium-sized cable clamp of the present invention;

[0030] Figure 6 It is a schematic diagram of the inverted experimental arrangement scheme of the small cable clamp for carbon fiber cable under lateral force in the present invention;

[0031] Figure 7 is a stereogram of a height-adjustable test platform of the present invention;

[0032] Figure 8 It is a partial schematic diagram of the lateral force inverted experimental arrangement scheme of the small cable clamp of the carbon fiber cable in the present invention;

[0033] Fig. 9 It is a flow chart of the topological optimization design method of the small cable clamp segmented protective cover of the present invention;

[0034] Fig.10 It is a diagram showing the stress condition of the original sheath of the present invention;

[0035] Fig.11 This is a diagram showing the stress conditions of the sheath after optimization of the present invention.

[0036] In the figure

[0037] 1. Carbon fiber cable; 11. Carbon fiber composite core material; 12. Outer sheath; 2. Small cable clamp; 21. Split protective cover; 22. Cable clamp holder; 23. Fastening nut; 24. U-shaped stud; 3. Height-adjustable test platform; 31. Column panel; 311. Column upright plate; 32. Stud; 33. Upper and lower nut groups; 34. Limit baffle; 341. Position baffle; 35. Stiffening rib; 36. Slider; 37. Cable clamp mounting hole. DETAILED DESCRIPTION

[0038] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0039] like Figure 1-11 As shown, the present invention provides a lateral force inverted test method for a small-sized carbon fiber cable clamp for photovoltaic use, comprising the following steps:

[0040] S1. Specimen installation: Both ends of the carbon fiber cable 1 are connected to the horizontal tensile testing machine through conventional hinged anchors. A small cable clamp 2 is provided in the middle of the carbon fiber cable 1. The small cable clamp 2 is fixed on a height-adjustable test platform 3. The fastening method of the carbon fiber cable 1 and the small cable clamp 2 is consistent with engineering applications. The U-shaped studs 24 pass through the cable clamp holder 22 downward in sequence.

[0041] S2. Cable pretensioning: operate the horizontal tensile testing machine, tension the carbon fiber cable 1 to 30% of the designed pretension (the ratio is adjustable), and check the status of each component of the test system;

[0042] S3. Test loading: operate the horizontal tensile testing machine, and load the carbon fiber cable 1 in stages to 30%, 50%, 70%, 80%, 90%, and 100% of the designed pre-tension of the carbon fiber cable 1. Observe and record the status of the carbon fiber cable 1, the small cable clamp 2, and the components in the test system in each loading stage: ① whether the carbon fiber cable 1 and the small cable clamp 2 are damaged; ② whether the working status of the components in the loading system is normal; ③ and obtain the force-displacement curve of the whole process of the horizontal tensile testing machine.

[0043] As a technical solution of the present invention, the cable body of the carbon fiber cable 1 in S1 is composed of a carbon fiber composite core material 11 and an outer sheath 12 .

[0044] As a technical solution of the present invention, the small cable clamp 2 is composed of a cable clamp seat 22, a U-shaped stud 24, a split protective cover 21 and a fastening nut 23, which can effectively disperse the lateral force of the carbon fiber cable 1 and reduce the damage to the carbon fiber cable 1; the structure is simple and compact, and it is easy to operate.

[0045] As a technical solution of the present invention, a slider 36 is provided on the top of the height-adjustable test platform 3 in S1, and the slider 36 is limited by the stop baffles 341 on both sides. A cable clamp mounting hole 37 is provided on the top of the slider 36, and the small cable clamp 2 is connected to the cable clamp mounting hole 37 and locked by the fastening nut 23. It should be noted that since the horizontal tensile testing machine mostly adopts unidirectional tension, the middle part of the carbon fiber cable 1 may slip along the tensile direction during the loading process. Sufficient sliding distance Ls is reserved on both sides of the slider 36 of the height-adjustable test platform 3, and the slider 36 does not contact the limit baffle 34 during the whole loading process. The stiffening ribs 35 are used to improve the stability of the limit baffle 34 and the positioning baffle 341 so as not to affect the stress of the carbon fiber cable 1. The height-adjustable test platform 3 is composed of two pairs of upper and lower column panels 31, totaling four column panels, and each pair of column panels 31 is fixed by a column upright 311, and the spacing between the two middle column panels 31 is adjusted by the high-strength bolts in the middle and the upper and lower nut groups 33: the test platform and the corresponding high-strength bolt pair specifications and dimensions have been calculated and verified to ensure safety and stability under the test lateral force loading, so as to avoid damage such as tilting and instability. The height-adjustable test platform 3 can meet the requirements of different bending angles.

[0046] A design method for a small cable clamp of a photovoltaic carbon fiber cable, the use steps of which are as follows:

[0047] T1. Based on the lateral force of the small cable clamp 2 and the diameter of the carbon fiber cable 1, a preliminarily designed sliced ​​protective cover 21 is provided. In the preliminarily designed sliced ​​protective cover 21, a regular semi-cylinder is provided;

[0048] T2. Based on the stress condition of the protective sleeve, a finite element model is established, and a topology optimization method is used to update the shape of the original sliced ​​protective sleeve 21 with the minimum strain energy as the objective function and the volume reduction as the constraint condition;

[0049] T3. Perform a stress analysis on the updated slice-type protective cover 21 through finite element analysis. If the requirements are not met, adjust the constraint conditions and repeat T2 until the requirements are met, and obtain a slice-type protective cover 21 that meets the requirements.

[0050] As a technical solution of the present invention, the constraint condition in T2 may also include chamfering the edge of the stainless steel sheet of the sliced ​​protective cover 21 to avoid scratching the outer cover 12 .

[0051] As a technical solution of the present invention, the sliced ​​protective cover 21 is made of stainless steel.

[0052] Embodiment 1:

[0053] like Figure 1-11 As shown, the steps of using a small cable clamp for photovoltaic carbon fiber cables and a transverse force test method are as follows:

[0054] Step 1: Calculation and analysis: Based on the actual project needs, the finite element software such as 3D3S is used to determine the lateral force value F and the maximum inclination angle θ of the small cable clamp 2; combined with the test cable length, the middle pad height H2 ( Figure 4 :H2=si nθ·L / 2); A height-adjustable test platform 3 is installed in the center of the cable body ( Figure 7 ), adjust the height to the specified elevation (H1+H2) by adjusting the length of the bolt group stud 32 ( Figure 6 ); U-bolt clamps the sliced ​​protective sleeve 21, passes through the cable clamp seat 22, is inserted into the reserved hole of the slider 36, and is fastened to the top plate of the slider 36 by a nut. The sliced ​​protective sleeve 21 is clamped with the cable body by the U-bolt ( Figure 8 );

[0055] Step 2: Install and pre-tighten the carbon fiber cable 1. Connect the two ends of the carbon fiber cable 1 to the loading end and the fixed end of the horizontal tensile testing machine through anchors. Preliminarily tension the carbon fiber cable 1. The cable force is 30% of the given tension. Check the operation of the test equipment.

[0056] Step 3: Test loading, graded control of the horizontal tensile machine to tension to a given tension value N1 (N1 = F / 2s i nθ), check the carbon fiber cable 1 body and the small cable clamp 2, continue loading until the carbon fiber cable 1 body and the small cable clamp 2 are damaged, and the vertical component of the tension is equal to and opposite to the lateral force loaded to the node.

[0057] It should be noted that: 1) The loading scheme can be adjusted according to the required construction sequence. The above process is the sequence of bending in place first and then tensioning. If you need to simulate the process of tensioning first and then stressing, you can first tension to a given cable force and then adjust the height for bending; 2) The loading scheme can be adjusted on the height adjustable test platform 3 ( Figure 7 ) A planar pressure gauge is added under the bottom column panel 31 to more accurately evaluate the stress on the node in the vertical direction; 3) The design optimization method of the segmented protective cover 21 of the present invention can be customized and optimized for the corresponding cable clamp nodes according to specific projects.

[0058] The above method adds a split protective sleeve 21 to the carbon fiber cable 1 body, and the U-shaped stud 24 and the cable clamp holder 22 are no longer in direct contact with the carbon fiber cable 1 body, but are first inserted into the stainless steel casing outside the carbon fiber cable 1 body, so that the contact between the small cable clamp 2 and the carbon fiber cable 1 body is changed from the original point contact to a surface contact within a certain range, thereby increasing the force-bearing area of ​​the lateral force of the carbon fiber cable 1 body, which can effectively alleviate the adverse effects of the lateral force on the carbon fiber cable 1 body and help to ensure the safety of the structure; in the flexible photovoltaic bracket project, the lateral force is transmitted downward to the photovoltaic pressure block through the photovoltaic panel, and the pressure block is transmitted downward to the small cable clamp 2, and the cable clamp holder 22 presses the carbon fiber cable 1 body downward (the arc-shaped notch of the cable clamp holder 22 faces downward), and the horizontal tensile machine in the laboratory can only be horizontal. To stretch the carbon fiber cable 1, the vertical downward loading needs to be combined with the reaction frame to increase the jack loading. The vertical upward loading space is limited and it is difficult to add a jack. For this reason, a height-adjustable test platform is added in the middle of the test stroke of the horizontal tensile testing machine to meet the lateral force loading at different bending angles. It can provide a solution for the lateral mechanical property test of similar cables and small cable clamps 2. By changing the bending angle and axial tension of the carbon fiber cable 1, the loading of a given lateral force can be achieved. This solution changes the original vertical downward lateral force to vertical upward lifting, and at the same time, the cable clamp holder 22 is installed with the opening facing upward, and the carbon fiber cable 1 body is still pressed tightly by the arc-shaped groove of the cable clamp holder 22, which does not change the actual engineering force and avoids the additional installation of jacks and reaction frames.

[0059] Embodiment 2: The steps of designing a small-sized carbon fiber cable clip for photovoltaic use are as follows:

[0060] Step a, based on the lateral force of the small cable clamp 2 and the cable body diameter of the carbon fiber cable 1, a preliminarily designed sliced ​​protective cover 21, in which the sliced ​​protective cover 21 is a regular semi-cylinder;

[0061] Step b: Based on the stress condition of the sliced ​​protective cover 21, a finite element model is established, such as Fig. 9 As shown, it can be seen from the calculation results that the stress level in some areas is low and the material performance has not been fully utilized. The topology optimization method is adopted, with the minimum strain energy as the objective function and the volume reduction as the constraint condition, to update the shape of the original slice-type protective sleeve 21 and obtain a semi-cylindrical piece with an irregular curve at the end;

[0062] Step c, performing a stress analysis on the updated slice-type protective cover 21 by finite element analysis. If the requirements are not met, adjusting the constraint conditions and repeating step b until the requirements are met, and obtaining a slice-type protective cover 21 that meets the requirements;

[0063] The piece-type protective cover 21 that satisfies the stress analysis is as follows Fig.11As shown, the above method can effectively improve the protective effect of the segmented protective cover 21, reduce the size of the segmented protective cover 21, and then reduce the size of the small cable clamp 2 and the node, thereby reducing the material usage by nearly 50%, reducing the weight of a single part, and facilitating transportation and construction.

[0064] The embodiments of the present invention are provided for the purpose of illustration and description. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations of the present invention. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A lateral force inverted test method for a small-sized carbon fiber cable clamp for photovoltaic use, characterized in that , including the following steps: S1. Specimen installation: Both ends of the carbon fiber cable (1) are connected to the horizontal tensile testing machine through conventional hinged anchors, a small cable clamp (2) is provided in the middle of the carbon fiber cable (1), and the small cable clamp (2) is fixed on a height-adjustable test platform (3); S2. Cable pretensioning: operate the horizontal tensile testing machine, tension the carbon fiber cable (1) to 30% of the designed pretensioning force, and check the status of each component in the test system; S3. Test loading: operate the horizontal tensile testing machine, load the carbon fiber cable (1) in stages to the designed pre-tension, observe and record the status of the carbon fiber cable (1), the small cable clamp (2) and the components of the test system in each loading stage: ① whether the test carbon fiber cable (1) and the small cable clamp (2) are damaged; ② whether the working status of the components in the test system is normal; ③ obtain the force-displacement curve of the whole process of the horizontal tensile testing machine.

2. A lateral force inverted test method for a small-sized carbon fiber cable clamp for photovoltaic use as claimed in claim 1, characterized in that: The carbon fiber rope (1) in S1 is composed of a carbon fiber composite core material (11) and an outer sheath (12).

3. A lateral force inverted test method for a small-sized carbon fiber cable clamp for photovoltaic use as claimed in claim 1, characterized in that: The S1 small and medium-sized cable clamp (2) is composed of a cable clamp holder (22), a U-shaped stud (24), a split-type protective sleeve (21) and a fastening nut (23).

4. A lateral force inverted test method for a small-sized carbon fiber cable clamp for photovoltaic use as claimed in claim 3, characterized in that: A slider (36) is arranged on the top of the height-adjustable test platform (3) in S1, a cable clamp installation hole (37) is opened on the top of the slider (36), and the small cable clamp (2) is connected to the cable clamp installation hole (37) and is locked by a fastening nut (23).

5. A design method for a small-sized carbon fiber cable clip for photovoltaic use, characterized in that: The lateral force inverted test method according to claims 1 to 4 is applicable, and the steps are as follows: T1. Based on the lateral force of the small cable clamp (2) and the diameter of the carbon fiber cable (1), a preliminarily designed sliced ​​protective sleeve (21) is provided. In the preliminarily designed sliced ​​protective sleeve (21) is a regular semi-cylinder; T2. Based on the stress condition of the slice-type protective sleeve (21), a finite element model is established, and a topology optimization method is used to update the shape of the original slice-type protective sleeve (21) with the minimum strain energy as the objective function and the volume reduction as the constraint condition; T3. Perform a stress analysis on the updated slice-type protective cover (21) by finite element analysis. If the requirements are not met, adjust the constraint conditions and repeat T2 until the requirements are met, and obtain a slice-type protective cover (21) that meets the requirements.

6. A method for designing a small-sized carbon fiber cable clip for photovoltaic use as claimed in claim 5, characterized in that: The constraint conditions within T2 may also include chamfering the edges of the split protective sleeve (21).

7. A method for designing a small-sized carbon fiber cable clip for photovoltaic use as claimed in claim 5, characterized in that: The sliced ​​protective sleeve (21) is made of stainless steel.

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