A device and method for testing the bending mechanics of a bolted spherical joint after corrosion

Abstract

A kind of bolt ball node bending mechanics test device and method after corrosion, belong to structural engineering test technical field.The present application includes base, clamp, node test piece, adapter steel pipe and force arm rod, node test piece is installed on base by clamp, and force arm rod is installed on the top of node test piece by adapter steel pipe.The purpose of the present application is to provide a kind of test device and scheme for bending mechanics loading of corroded bolt ball node.The present application solves the problem that node test piece can be corroded in smaller volume and mass state, and after corrosion is completed, reliable constraint and bending moment loading path can be conveniently provided to node without secondary processing such as welding, ensures that the mechanical properties measured in test truly reflect corrosion damage state.

Description

Technical Field

[0001] This invention relates to a test apparatus and method for the bending mechanics of a bolted ball joint after corrosion, belonging to the field of structural engineering test technology. Background Technology

[0002] Spatial structures are a type of structural system with large spans, widely used in public and industrial buildings. Since the 1960s and 70s, my country has begun constructing a large number of spatial structures. Over time, many of these in-service spatial structures have entered or are about to enter the middle to late stages of their design service life, and corrosion problems are becoming increasingly prominent. When corrosion is severe, the mechanical properties of structural components decline, posing safety hazards for continued service. As one of the most commonly used node types in spatial grid structures, the impact of corrosion on the bending mechanical properties of bolted ball joints is of significant research value.

[0003] Existing bending test schemes for bolted ball joints can be broadly classified into two categories: simply supported loading and cantilever loading. The former requires welding round steel pipes on both sides of the joint as levers, resulting in a large volume and weight; the latter can be based on the former by taking half of the structure, but still requires welding a round steel pipe on one side, and the joint itself needs to be welded to a base with high stiffness.

[0004] To reproduce the true state, the bolt ball joint needs to undergo accelerated salt spray corrosion in the assembled state. Due to space limitations, the quality and volume of the joint specimens need to be strictly controlled. At the same time, to prevent the rust expansion effect caused by corrosion from affecting the joint, it is not advisable to disassemble or weld or perform other secondary processing after the joint corrosion is completed.

[0005] Therefore, it is inconvenient to weld large or heavy auxiliary components onto the joint specimens, whether before or after corrosion. Conventional bending loading schemes are not suitable for mechanical testing of bolted ball joints after corrosion. Therefore, it is urgent to propose a mechanical testing device and method for bolted ball joints under bending after corrosion to solve the above-mentioned technical problems. Summary of the Invention

[0006] The purpose of this invention is to provide a test apparatus and scheme for applying bending mechanical loading to corroded bolt-ball joints. This invention addresses the problem that joint specimens can be corroded with relatively small volume and mass, and that after corrosion, reliable constraints and bending moment loading pathways can be conveniently provided to the joint without secondary processing such as welding. A brief overview of the invention is provided below to offer a basic understanding of certain aspects of it. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention.

[0007] The technical solution of this invention:

[0008] Option 1: A test device for bending mechanics of a bolt ball joint after corrosion, comprising a base, a clamp, a joint specimen, a connecting steel pipe, and a lever arm. The joint specimen is installed on the base via the clamp, and a lever arm is installed on the top of the joint specimen via the connecting steel pipe.

[0009] Preferably, the fixture includes a base plate, a C-shaped groove, and a cover plate. The C-shaped groove is fixedly installed on the base plate, and the cover plate is detachably installed on the opening side of the C-shaped groove. The C-shaped groove and the cover plate form a clamping space enclosed by four sides.

[0010] Preferably, the node specimen includes a bolt ball, a bolt hole cut-out plane, a cone head, and a circular flange. The top of the bolt ball is fitted with a cone head, the top of the cone head has a circular flange, and the bolt ball is machined with a bolt hole cut-out plane.

[0011] Preferably, the bolt ball of the node specimen is provided with multiple screw holes, wherein the cutting plane of at least three screw hole openings is machined as a positioning plane; when the node specimen is clamped in the clamping space, the positioning plane is in contact with the inner wall of the back plate of the C-shaped groove, the upper surface of the bottom plate and the inner surface of the cover plate respectively.

[0012] Preferably, the top of the adapter steel pipe is connected to the bottom of the lever arm via a connecting plate, and the bottom of the adapter steel pipe is connected to the bottom of the lever arm via a connecting flange.

[0013] Preferably, it further includes a reaction frame, a jack, and a force sensor. The reaction frame has a horizontal portion and a vertical portion that are perpendicular to each other. The base is fixed on the horizontal portion of the reaction frame. The jack is installed on the vertical portion of the reaction frame through the force sensor, so that the arc-shaped push head of the jack is set horizontally and the lever arm is set vertically. During the loading process, the arc-shaped push head of the jack gradually extends and applies a horizontal thrust to the lever arm.

[0014] Option 2, a method for testing the bending mechanics of a bolted ball joint after corrosion, is based on the testing device for testing the bending mechanics of a bolted ball joint after corrosion described in Option 1, and includes the following steps:

[0015] S1: Assembly and specimen installation: Fix the base to the loading platform; install the fixture on the base; place the bolt ball of the corroded node specimen into the clamping space of the fixture, adjust its position so that at least three bolt hole tangential planes are respectively in contact with the inner wall of the fixture, and then tighten the fixture to clamp the node specimen.

[0016] S2: Loading path connection: Connect the connecting flange at the bottom of the transfer steel pipe to the circular flange at the top of the node specimen with bolts; then connect the lever arm to the square connecting plate at the top of the transfer steel pipe with bolts to form a cantilever structure;

[0017] S3: Apply load and acquire data: Operate the jack so that its arc-shaped push head applies a horizontal thrust to the vertically set lever arm; Simultaneously record the thrust value measured by the force sensor, and monitor or calculate the change in the tilt angle of the lever arm;

[0018] S4: Data processing: Calculate the bending moment acting on the node specimen based on the recorded thrust value and the effective length of the lever arm, and obtain the bending moment-rotation angle mechanical performance curve of the bolt ball joint after corrosion by combining the corresponding tilt angle change data.

[0019] The present invention has the following beneficial effects:

[0020] 1. This invention addresses the core contradiction of bolted ball joints requiring accelerated salt spray corrosion in an assembled state, and the inability to undergo secondary processing after corrosion. It proposes a solution of "pre-welded small flange + bolted connection after corrosion." Before corrosion, the joint specimen only requires a small, lightweight circular flange pre-welded, greatly satisfying the stringent limitations of corrosion equipment on specimen size and weight. After corrosion, high-strength bolts are used to assemble the joint with the adapter pipe and lever arm, completely avoiding disturbances caused by secondary hot working processes such as welding and cutting to the internal rust expansion effect of the joint. This ensures that the mechanical properties measured in the experiment truly reflect the corrosion damage state.

[0021] 2. This invention ingeniously utilizes the geometric characteristics of the bolt ball joint itself. By using the three orthogonal bolt hole tangent planes on the joint as positioning references, they are precisely fitted and tightened against the inner surfaces of the back plate, bottom plate, and cover plate of the C-groove of the fixture. High-strength bolts are then used to apply preload, forming a robust multi-directional constraint. Finite element simulation verification shows that this constraint method results in a very small rotation angle when the joint reaches its ultimate bending moment, approaching ideal fixed-end boundary conditions. This ensures that the applied bending moment is effectively transferred and used to evaluate joint performance, and the test results are accurate and reliable.

[0022] 3. This invention employs a modular design from the base and fixtures to the force transmission components (adapter pipes, lever arms), with each part connected by standardized high-strength bolts. This gives the device high flexibility and versatility: by replacing different specifications of C-grooves or adapter pipes, it can be quickly adapted to bolt ball joints of different sizes; the entire device can be easily disassembled and reused. This feature is particularly advantageous when conducting extensive statistical studies on the performance of corrosion-affected joints, significantly reducing the auxiliary processing costs and test preparation time for individual specimens.

[0023] 4. This invention securely mounts the device onto the reaction frame and uses a hydraulic jack with a force sensor to apply a controllable horizontal thrust to the lever arm. It can simultaneously and accurately collect thrust and rotation angle data. The process is standardized and safe to operate, providing a standardized means for systematically evaluating the bending performance and rotational stiffness of corroded bolt ball joints. Attached Figure Description

[0024] Figure 1 This is a three-dimensional diagram of a test apparatus for the bending mechanics of a bolted ball joint after corrosion.

[0025] Figure 2 This is a diagram showing the assembly of a testing device for the bending mechanics of a bolted ball joint after corrosion.

[0026] Figure 3 This is a diagram showing the installation of the adapter steel pipe and the node specimen according to the present invention;

[0027] Figure 4 This is a schematic diagram of the structure of the adapter steel pipe of the present invention;

[0028] Figure 5 This is a schematic diagram of the structure of the node specimen of the present invention;

[0029] Figure 6 This is a diagram showing the assembly of the node specimen and the fixture according to the present invention.

[0030] In the figure: 1-base, 2-clamp, 3-node specimen, 4-transfer steel pipe, 5-lever arm, 6-reaction frame, 7-jack, 8-force sensor, 21-base plate, 22-C-groove, 23-cover plate, 31-bolt ball, 32-screw hole cut plane, 33-cone head, 34-circular flange, 41-connecting plate, 42-connecting flange. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0032] The connections mentioned in this invention are divided into fixed connections and detachable connections. Fixed connections (i.e., non-detachable connections) include, but are not limited to, conventional fixed connection methods such as folded connections, riveted connections, adhesive connections, and welded connections. Detachable connections include, but are not limited to, conventional disassembly methods such as threaded connections, snap-fit ​​connections, pin connections, and hinged connections. When a specific connection method is not explicitly defined, it is assumed that at least one existing connection method can always be found to achieve the function, and those skilled in the art can choose according to their needs. For example, a welded connection can be chosen for fixed connections, and a hinged connection can be chosen for detachable connections.

[0033] Example 1: Combination Figures 1-6This embodiment describes a bolt ball joint bending mechanics testing device after corrosion, comprising a base 1, a clamp 2, a joint specimen 3, a connecting steel pipe 4, a lever arm 5, a reaction frame 6, a jack 7, and a force sensor 8. The clamp 2 is mounted on the upper surface of the base 1. The joint specimen 3 is clamped and fixed by the clamp 2, and its top is connected to the lever arm 5 through the connecting steel pipe 4, thereby forming a complete cantilever loading structure.

[0034] The reaction frame 6 has a horizontal part and a vertical part that are perpendicular to each other; the base 1 is fixed on the horizontal part of the reaction frame 6; the jack 7 is installed on the vertical part of the reaction frame 6 through the force sensor 8, so that the arc-shaped push head of the jack 7 is set horizontally and the lever arm 5 is set vertically. During the loading process, the arc-shaped push head of the jack 7 gradually extends and applies a horizontal thrust to the lever arm 5.

[0035] The base 1 serves as the load-bearing and installation foundation for the device. It is welded from 10mm thick Q235 steel plates, providing significant overall rigidity. Specifically, the base 1 includes upper and lower panels and orthogonal trapezoidal ribs connecting them. Multiple sets of bolt holes are provided on both the upper and lower panels. The lower panel is used to securely connect to the loading platform, such as the test reaction frame, using 10.9 grade high-strength bolts, while the upper panel is used to install the clamp 2.

[0036] The clamp 2 is the core component that holds and constrains the node specimen 3, and it adopts a detachable design. The clamp 2 includes a base plate 21, a C-shaped groove 22, and a cover plate 23.

[0037] The base plate 21 is made of 10mm thick steel plate and is fixed to the base 1 by bolts.

[0038] The C-shaped groove 22 is welded to the base plate 21 from a 10mm thick steel plate, forming a three-sided enclosed "C"-shaped space. The internal width and height of the C-shaped groove 22 are designed to be slightly larger than the diameter of the bolt ball 31 to be tested, and the depth is approximately 0.7 times the diameter of the ball. On both sides of the outer side of the opening of the C-shaped groove 22, a connecting lug with a circular screw hole is welded.

[0039] The cover plate 23 is made of 20mm thick steel plate, with stiffening ribs on one side to improve rigidity. Elongated screw holes are located at the four corners of the cover plate 23. During installation, the cover plate 23 covers the opening side of the C-shaped groove 22. Four 12.9 grade high-strength long bolts are passed sequentially through the elongated holes of the cover plate 23 and the round holes on the connecting ear plate of the C-shaped groove 22, and the internal node specimen 3 is clamped by tightening the nuts. The C-shaped groove 22 and the cover plate 23 together form a four-sided enclosed clamping space.

[0040] The node specimen 3 is a standard bolt ball joint that has undergone accelerated salt spray corrosion testing. It includes a bolt ball 31, a cone head 33, and a circular flange 34.

[0041] The bolt ball 31 is of standard specification and has six orthogonal screw holes. A key design feature is that, to provide reliable positioning for the fixture, the tangential planes 32 of the openings of the three screw holes located on the same vertical plane are machined into smooth positioning planes (the diameter of the tangential plane of each screw hole opening is not less than 0.6 times the diameter of the ball). These three planes are pairwise orthogonal in space.

[0042] Prior to the corrosion test at the node, a circular flange 34 was pre-welded to the tail of one of the cones 33. The flange's specifications match the connecting flange 42 at the bottom of the transition steel pipe 4. This pre-welding is the only necessary initial processing to ensure the specimen's lightweight during the corrosion stage.

[0043] The transition steel pipe 4 is a force-transmitting component connecting the node specimen 3 and the lever arm 5. Its length is approximately 200mm, and its diameter and wall thickness are not less than the specifications of the round steel pipe suitable for the node cone head 33. A circular flange (i.e., connecting flange 42) is welded to the bottom of the transition steel pipe 4, and it is connected to the circular flange 34 of the node specimen 3 by six 12.9 grade high-strength bolts. A square connecting plate 41 is welded to the top of the transition steel pipe 4, and it is connected to the bottom of the lever arm 5 by eight 10.9 grade high-strength bolts.

[0044] The lever arm 5 is a lever used to apply torque. It is a hollow rectangular cross-section bar with closed ends, welded from a 10mm thick Q235 steel plate, with a side length of approximately 100mm. The length of the lever arm can be flexibly adjusted according to the torque required for the test. A square flange, identical to the square connecting plate 41 on the top of the adapter steel pipe 4, is welded to its lower end for bolt connection between the two.

[0045] The reaction frame 6 is an L-shaped rigid structure with mutually perpendicular horizontal and vertical parts.

[0046] A hydraulic jack 7 is horizontally mounted on the vertical part of the reaction frame 6 via a force sensor 8. The front end of the jack 7 is equipped with an arc-shaped push head for smoothly applying force to the lever arm 5. The force sensor 8 is used to monitor the applied thrust value in real time. The base 1 is vertically fixed to the horizontal part of the reaction frame 6 by high-strength bolts, ensuring that the installed lever arm 5 is in a vertical position. The axis of the jack 7 is horizontally aligned with the lever arm 5.

[0047] The reaction frame 6 is made of structural steel with a strength grade of not less than Q235. The welds are made of E43 type welding rods, and the weld leg size is not less than 5mm. The specifications of all connecting bolts (such as 10.9 grade and 12.9 grade) must be calculated and selected based on the maximum bending moment estimated by the test to ensure reliable connection.

[0048] Example 2: Combination Figures 1-6 This embodiment describes a method for testing the bending mechanics of a bolted ball joint after corrosion, based on the bending mechanics testing apparatus described in Example 1. The method includes the following steps:

[0049] S1: Assembly of the device and installation of the specimen after corrosion.

[0050] First, the base 1 is securely installed on the horizontal platform of the reaction frame 6 using high-strength bolts. Next, the base plate 21 of the clamp 2 is bolted onto the base 1.

[0051] Then, install the node specimen 3, which has undergone salt spray accelerated corrosion.

[0052] Specifically, the bolt ball 31 of the node specimen 3 is vertically placed into the C-groove 22 of the fixture 2. By manually adjusting the angle of the node specimen 3, it is ensured that the three orthogonal bolt hole tangent planes 32 pre-machined on its bolt ball 31 are precisely fitted and tightened against the inner wall of the back plate of the C-groove 22, the upper surface of the bottom plate 21, and the inner surface of the cover plate 23 to be covered. This step utilizes the node's own geometric features to achieve natural positioning.

[0053] Finally, cover plate 23 is placed on top, and four 12.9 grade high-strength long bolts are passed sequentially through the elongated holes at the four corners of cover plate 23 and the ear plate holes on the outside of C-shaped groove 22. The nuts are then tightened evenly using a torque wrench. Through the bolt preload, node specimen 3 is firmly clamped between C-shaped groove 22 and cover plate 23, forming a near-ideal fixed end constraint.

[0054] S2: Load path connection.

[0055] After the specimen is reliably clamped, the loading force transmission path is established. First, using six 12.9 grade high-strength bolts, the circular connecting flange 42 at the bottom of the transition steel pipe 4 is fastened to the circular flange 34 pre-welded to the cone head of the node specimen 3. Then, using eight 10.9 grade high-strength bolts, the square flange at the lower end of the lever arm 5 is fastened to the square connecting plate 41 at the top of the transition steel pipe 4. At this point, the rigid cantilever structure from the node specimen 3 to the top of the lever arm 5 is assembled.

[0056] S3: Apply load and synchronously acquire data.

[0057] Start the control system of hydraulic jack 7. This causes the piston rod of jack 7 to extend slowly and at a constant speed, with the arc-shaped push head extending horizontally to push the vertically positioned lever arm 5.

[0058] During this process, two key data collections are performed simultaneously:

[0059] The force sensor 8 connected in series with the jack 7 continuously records the horizontal thrust F applied to the lever arm 5 in real time.

[0060] The change in the angle θ of the lever arm 5 relative to the vertical baseline is monitored in real time using a displacement gauge or inclinometer (or converted by measuring the horizontal displacement at the end of the lever arm).

[0061] S4: Data processing and performance analysis.

[0062] After the experiment, the collected data was processed:

[0063] Bending moment calculation: According to the lever principle, the bending moment M at the root of the node is M = F × L, where F is the thrust and L is the effective length of the lever arm from the jack application point to the center of the node, which needs to be measured and calibrated in advance.

[0064] Plotting the relationship curve: By matching the calculated bending moment M with the synchronously recorded rotation angle θ (radians), the bending moment-rotation angle (M-θ) relationship curve of the corroded bolt ball joint can be plotted.

[0065] Performance evaluation: Based on the obtained M-θ curve, key mechanical performance parameters such as the initial rotational stiffness, yield moment, and ultimate moment of the node can be analyzed, thereby quantitatively evaluating the impact of corrosion on its bending performance.

[0066] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be permuted and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutation and combination. Therefore, the present invention will not describe the technical solutions after permutation and combination one by one, but it should be understood that the technical solutions after permutation and combination have been disclosed by the present invention.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A test apparatus for the bending mechanics of a bolted ball joint after corrosion, characterized in that: It includes a base (1), a clamp (2), a node specimen (3), a transfer steel pipe (4) and a lever arm (5). The node specimen (3) is installed on the base (1) through the clamp (2), and the lever arm (5) is installed on the top of the node specimen (3) through the transfer steel pipe (4).

2. The test apparatus for bending mechanics of a bolt ball joint after corrosion according to claim 1, characterized in that: The clamp (2) includes a base plate (21), a C-shaped groove (22) and a cover plate (23). The C-shaped groove (22) is fixedly installed on the base plate (21), and the cover plate (23) is detachably installed on the opening side of the C-shaped groove (22). The C-shaped groove (22) and the cover plate (23) form a clamping space enclosed by four sides.

3. The test apparatus for bending mechanics of a bolted ball joint after corrosion according to claim 1, characterized in that: The node specimen (3) includes a bolt ball (31), a bolt hole cutting plane (32), a cone (33) and a circular flange (34). The top of the bolt ball (31) is equipped with a cone (33), the top of the cone (33) has a circular flange (34), and the bolt ball (31) is machined with a bolt hole cutting plane (32).

4. The bending mechanical testing device for a bolt ball joint after corrosion according to claim 1, characterized in that: The bolt ball of the node specimen (3) is provided with multiple screw holes, and the cutting plane (32) of at least three screw hole openings is machined into positioning planes; when the node specimen (3) is clamped in the clamping space, the positioning planes are in contact with the inner wall of the back plate of the C-shaped groove (22), the upper surface of the bottom plate (21) and the inner surface of the cover plate (23), respectively.

5. The bending mechanical testing device for a bolt ball joint after corrosion according to claim 1, characterized in that: The top of the transfer steel pipe (4) is connected to the bottom of the lever arm (5) via a connecting plate (41), and the bottom of the transfer steel pipe (4) is connected to the bottom of the lever arm (5) via a connecting flange (42).

6. The bending mechanical testing device for a bolted ball joint after corrosion according to claim 1, characterized in that: It also includes a reaction frame (6), a jack (7) and a force sensor (8). The reaction frame (6) has a horizontal part and a vertical part that are perpendicular to each other. The base (1) is fixed on the horizontal part of the reaction frame (6). The jack (7) is installed on the vertical part of the reaction frame (6) through the force sensor (8), so that the arc-shaped push head of the jack (7) is set horizontally and the lever arm (5) is set vertically. During the loading process, the arc-shaped push head of the jack (7) gradually extends and applies a horizontal thrust to the lever arm (5) from the arc-shaped push head.

7. A method for testing the bending mechanics of a bolted ball joint after corrosion, which is based on the testing apparatus for testing the bending mechanics of a bolted ball joint after corrosion as described in claim 1, characterized in that, Includes the following steps: S1: Assembly and specimen installation: Fix the base (1) to the loading platform; install the clamp (2) on the base (1); place the bolt ball of the node specimen (3) that has been corroded into the clamping space of the clamp (2), adjust its position so that at least three bolt hole tangential planes (32) are respectively in contact with the inner wall of the clamp, and then tighten the clamp (2) to clamp the node specimen (3); S2: Loading path connection: Connect the connecting flange (42) at the bottom of the transfer steel pipe (4) to the circular flange (34) at the top of the node specimen (3) by bolts; then connect the lever arm (5) to the square connecting plate (41) at the top of the transfer steel pipe (4) by bolts to form a cantilever structure; S3: Apply load and collect data: Operate the jack (7) so that its arc-shaped push head applies a horizontal thrust to the vertically set lever arm (5); Simultaneously record the thrust value measured by the force sensor (8), and monitor or calculate the change in the tilt angle of the lever arm (5); S4: Data processing: Based on the recorded thrust value and the effective length of the lever arm (5), calculate the bending moment acting on the node specimen (3), and combine it with the corresponding tilt angle change data to obtain the bending moment-rotation angle mechanical performance curve of the bolt ball node after corrosion.

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