A device for steel pipe drawing test

Abstract

The application relates to the field of drawing test devices, in particular to a device for steel pipe drawing test. The device comprises a mounting seat, outer side plates, inner side plates, drawing test assemblies and double-head drawing force applying assemblies. Two groups of outer side plates are arranged on two rotating driving frames respectively; two groups of inner side plates are rotationally arranged on the two groups of outer side plates; a plurality of groups of drawing test assemblies are transversely arranged between the two groups of inner side plates; the end of a drawing test channel is provided with a spraying section, and the middle part is provided with an imaging monitoring section; and a plurality of groups of double-head drawing force applying assemblies are transversely arranged on the two groups of outer side plates. The device is characterized in that the work stations are switched through the rotation of the outer side plates and the inner side plates, the environment control and online monitoring of the drawing test assemblies and the synchronous and accurate loading of the double-head drawing force applying assemblies are closely linked, the batch automatic operation of the steel pipe drawing test is realized, and remarkable progress is achieved in the aspects of clamping precision, stress state control and deformation measurement accuracy.

Description

Technical Field

[0001] This invention relates to the field of pull-out testing apparatus, and more particularly to an apparatus for pull-out testing of steel pipes. Background Technology

[0002] During the drilling of slope anchor piles and mortar anchors, problems such as stuck drills, hole collapse, and inability to form holes frequently occur. Workers also encountered stuck drills when attempting self-drilling anchor installation. To ensure slope stability, workers replaced the slope anchors and anchor piles with steel conduits. The installed steel conduits were not pulled out, thus creating a situation where the steel conduits replaced the anchors. At the initial stage of anchor installation, pull-out tests should be conducted on 3% of the working anchors using the steel conduits.

[0003] Traditional steel pipe pull-out testing devices suffer from several drawbacks. The clamping methods used are ill-suited to the varying internal and external thread structures at both ends of the steel pipe, easily introducing additional stress and causing data distortion. Manual single-pipe serial testing is inefficient and cannot meet the timeliness requirements of batch sampling in engineering projects. Deformation acquisition methods relying on local point measurements (such as extensometers) struggle to capture the complex strain distribution across the threaded area and the entire pipe body. The low level of automation in the testing process, with manual intervention in sample preparation, clamping, loading, and measurement, leads to poor data consistency and comparability. Furthermore, the lack of coordinated control over sample surface pretreatment quality and the testing imaging environment limits the application effectiveness of high-precision full-field optical measurement methods (such as digital image correlation). Therefore, there is an urgent need for a device capable of efficient, accurate, and automated batch testing of steel pipes for pull-out testing. Summary of the Invention

[0004] To address the problems existing in the background technology, a device for steel pipe pull-out testing is proposed. The device achieves station switching through the rotation of the outer and inner side plates, close linkage between environmental control and online monitoring of the pull-out test components, and synchronous and precise loading of the double-headed pull-out force application components. This not only realizes the batch automated operation of steel pipe pull-out testing, but also achieves significant progress in clamping accuracy, stress state control, and deformation measurement accuracy.

[0005] This invention proposes a device for a steel pipe pull-out test, comprising a mounting base, outer side plates, inner side plates, pull-out test components, and a double-headed pull-out force application component. The mounting base has opposite loading and unloading ports on both sides, and a rotating drive frame located below the loading and unloading ports. Two sets of outer side plates are arranged parallel to each other on the rotating ends of the rotating drive frames, and multiple sets of corresponding through slots are arranged around the rotating ends. Each set of through slots has a loading / unloading station and a pull-out station. Two sets of inner side plates are rotatably mounted on opposite ends of the two sets of outer side plates, and each set of inner side plates has a ring of through holes corresponding to the through slots. By rotating the inner side plates from their origin, the multiple sets of inner through holes can be switched to simultaneously connect with the loading / unloading station or the pull-out station. Multiple sets of pull-out test components are arranged laterally between the two sets of inner side plates, and each set of pull-out test components has a pull-out test channel. The two ends of the pull-out test channel are respectively connected to the through holes on both sides, and the end of the pull-out test channel has a spraying section for spraying a layer of random black and white powder onto the steel pipe to be tested. The system generates digital fingerprints from speckled patterns. An imaging monitoring section is located in the middle of the pull-out test channel to capture the image deformation process during the pull-out test and collect deformation data. Multiple sets of dual-head pull-out force application components are horizontally installed across two sets of outer plates. Each set of dual-head pull-out force application components extends from both ends of the outer plate and has a pull-out end corresponding to each pull-out station. One pull-out end has a connector I connected to the internal thread end of the steel pipe, and the other pull-out end has a connector II connected to the external thread end of the steel pipe. During the pull-out test, connector I and connector II connect to both ends of the steel pipe, and the pull-out ends at both ends are synchronously controlled to apply an increasing axial tensile force to both ends of the steel pipe at a preset loading rate. When the tensile force reaches a predetermined threshold, the system switches to a force-holding mode to stabilize the tensile force applied to the steel pipe, while the imaging monitoring section collects deformation data.

[0006] Preferably, the through groove is arc-shaped, and the loading / unloading station and the drawing station are respectively located at both ends of the arc-shaped section of the through groove; the arc-shaped structure of the through groove matches the rotation trajectory of the through hole.

[0007] Preferably, the inner side plate is annular; a toothed ring is provided on the outer wall of the ring; a gear is rotatably provided on one side of the inner side plate and meshes with the toothed ring; a through hole is provided along the ring body, and a moving part that acts on the steel pipe is provided in the through hole.

[0008] Preferably, the first movable component includes a mounting cylinder located inside the through hole; a ring of electrically controlled telescopic lifting platforms is provided on the inner wall of the mounting cylinder; a first movable head and a second movable head are alternately arranged on multiple sets of lifting platforms; the first movable head and the second movable head are provided with electric movable wheels with alternating rotation directions, the former driving the steel pipe to rotate along the length direction, and the latter driving the steel pipe to rotate along the circumference direction; the loading and unloading ports are set on the rotation trajectory of the through hole, and the second movable component with the same structure as the first movable component is provided inside the loading and unloading ports.

[0009] Preferably, the pull-out test assembly includes a pull-out test tube with corresponding side through holes at both ends; a pull-out test channel is set inside the pull-out test tube; a spraying component is set at the spraying section corresponding to the pull-out test tube, and an imaging monitoring component is set at the imaging monitoring section corresponding to the pull-out test tube.

[0010] Preferably, the sprayed component includes a spraying frame located at the opening of the pull-out test tube; the spraying frame is connected to an external paint storage device via a tube; the spraying frame is configured as a ring, with the spray nozzles arranged along its circumference.

[0011] Preferably, multiple sets of imaging monitoring components are provided, and each set of imaging monitoring components includes an imaging monitoring sleeve that moves horizontally within the pull-out test channel along the length of the pull-out test tube; the inner wall of the imaging monitoring sleeve is provided with a ring track in the middle and brightness adjustment areas on both sides of the ring track; the imaging device moves in a circular trajectory by sliding along the ring track; LED lights are arranged in the brightness adjustment areas along the ring track.

[0012] Preferably, the dual-head pulling force application assembly includes multiple sets of dual-head force applicators disposed between two sets of outer side plates and a pulling force application frame disposed on the outside of the two sets of outer side plates; the multiple sets of dual-head force applicators are divided into inner and outer rings, and the dual-head force applicators of the inner and outer rings are paired and cooperate. The dual-head force applicators of the inner ring are disposed along the inner hole of the inner side plate, and the dual-head force applicators of the outer ring are disposed along the outer periphery of the inner side plate; the pulling force application frame is the pulling end, including the frame body; the position of the frame body corresponds one-to-one with the pulling station, and the two ends are respectively connected to the force application ends of the paired inner and outer ring dual-head force applicators through fixing frames. The middle of the frame body is provided with a mounting platform connected to connector one or connector two.

[0013] Preferably, the connecting component one includes a rotating seat one for rotating connection mounting platform; the center of the rotating seat one is provided with a threaded post that is threaded to the internal thread end of the steel pipe, and the outer periphery of the rotating seat one is provided with a limiting sleeve that is threaded to the outer wall of the steel pipe; an annular steel pipe connecting cavity one is formed between the limiting sleeve and the threaded post; a secondary limiting cylinder one is sleeved on the outside of the limiting sleeve; the secondary limiting cylinder one is threaded to the limiting sleeve, and an anti-slip ring one that is threaded to the outer wall of the steel pipe is provided on the opening of the secondary limiting cylinder one.

[0014] Preferably, the second connector includes a rotating seat second for rotating the mounting platform; the center of the rotating seat second is provided with a limiting post that mates with the inner wall of the steel pipe, and the outer periphery of the rotating seat second is provided with a threaded sleeve that mates with the external thread end of the steel pipe; an annular steel pipe connecting cavity second is formed between the threaded sleeve and the limiting post; a secondary limiting cylinder second is provided outside the threaded sleeve; the secondary limiting cylinder second is threaded with the threaded sleeve, and an anti-slip ring second that mates with the outer wall of the steel pipe is provided on the opening of the secondary limiting cylinder second.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects:

[0016] The arc-shaped through-slot design on the outer side plate, combined with the annular through-holes on the inner side plate, allows multiple steel pipes to be switched synchronously and precisely between the loading / unloading station and the drawing station through their coordinated rotation. This linkage design enables a production line operation in which multiple steel pipes are loaded, prepared, tested, and unloaded sequentially or simultaneously, significantly improving testing efficiency and overcoming the problem of low efficiency in traditional single-pipe testing.

[0017] The pull-out test assembly is directly connected to the through-hole of the inner plate, forming a controlled, sealed test channel. During the linkage process, the steel pipe is precisely positioned, horizontally conveyed, and surface speckle spraying is completed within the moving parts of the inner plate and the test channel. Subsequently, through the coordinated rotation of the inner and outer plates, both ends of the steel pipe are accurately delivered to the pull-out station, where they are automatically aligned and securely connected with the connectors of the double-headed pull-out force application assembly. This multi-component linkage ensures a high degree of consistency and repeatability in the pre-test treatment, clamping, and stress state of each steel pipe, laying the foundation for obtaining reliable comparative data.

[0018] The dual-headed pull-out force application assembly operates in tandem with the signal indicating the switching of the inner and outer plates to the pull-out position. The pull-out force application frames at both ends move synchronously towards each other, achieving rapid and secure double locking with the internal and external threaded ends of the steel pipe through specially designed connectors (connectors one and two). During the force application process, the imaging monitoring section (imaging monitoring component) within the pull-out test assembly is activated simultaneously to dynamically track and capture the speckle pattern on the steel pipe surface. The precise force control provided by the force application assembly and the full-field deformation data acquired by the imaging component are synchronized through the system, enabling digital image correlation algorithms to accurately calculate the stress-strain relationship of the steel pipe. This achieves a high degree of coordination between loading and measurement, significantly improving the accuracy and completeness of the test data. Attached Figure Description

[0019] Figure 1 This is a structural diagram of the apparatus used for steel pipe pull-out tests;

[0020] Figure 2 An exploded view of the apparatus used for steel pipe pull-out tests;

[0021] Figure 3 Structural diagram of the outer side plate, inner side plate, pull-out test assembly, and double-headed pull-out force application assembly (viewpoint 1);

[0022] Figure 4 Structural diagram of the outer side plate, inner side plate, pull-out test assembly, and double-headed pull-out force application assembly (perspective 2).

[0023] Figure 5 This is a structural diagram of the outer and inner side plates;

[0024] Figure 6 for Figure 5 Enlarged view of point A in the middle;

[0025] Figure 7 This is a cross-sectional view of the pull-out test assembly;

[0026] Figure 8 for Figure 7 Enlarged view at point B in the middle;

[0027] Figure 9 Here is a structural diagram of connector one;

[0028] Figure 10 Here is a structural diagram of connector two;

[0029] Reference numerals: 1. Mounting base; 101. Loading / unloading port; 2. Rotary drive frame; 3. Outer side plate; 301. Through slot; 4. Inner side plate; 401. Through hole; 402. Moving part one; 40201. Mounting cylinder; 40202. Lifting platform; 40203. Moving head one; 40204. Moving head two; 403. Gear ring; 404. Gear; 5. Pull-out test assembly; 501. Pull-out test tube; 502. Spraying frame; 503. Tube; 504. Imaging monitoring component; 50401. Imaging monitoring sleeve; 50402. Brightness adjustment area 50403, Circular track; 50404, Imaging equipment; 6, Double-headed pulling force application assembly; 601, Double-headed force applicator; 602, Pulling force application frame; 60201, Frame body; 60202, Fixing frame; 60203, Mounting platform; 7, Connector 1; 701, Limiting sleeve; 702, Rotating seat 1; 703, Secondary limiting cylinder 1; 704, Anti-slip ring 1; 705, Threaded post; 8, Connector 2; 801, Threaded sleeve; 802, Rotating seat 2; 803, Secondary limiting cylinder 2; 804, Anti-slip ring 2; 805, Limiting post. Detailed Implementation

[0030] Example 1, as Figures 1-4As shown, this invention proposes a device for a steel pipe pull-out test, including a mounting base 1, outer side plates 3, inner side plates 4, pull-out test components 5, and a double-headed pull-out force application component 6. The mounting base 1 has opposite loading / unloading ports 101 on both sides, and a rotating drive frame 2 located below the loading / unloading ports 101. Two sets of outer side plates 3 are arranged parallel to each other on the rotating ends of the rotating drive frames 2, and multiple sets of corresponding through slots 301 are arranged around the rotating ends. Each set of through slots 301 has a loading / unloading station and a pull-out station. Two sets of inner side plates 4 are rotatably mounted on opposite ends of the two sets of outer side plates 3, and each set of inner side plates 4 has a ring of through holes 401 corresponding to the through slots 301. By rotating the inner side plates 4 at their origin, multiple sets of inner through holes 401 are simultaneously connected to the loading / unloading station or the pull-out station. Multiple sets of pull-out test components 5 are arranged laterally between the two sets of inner side plates 4. Each component 5 is equipped with a pull-out test channel; both ends of the pull-out test channel are connected to the through holes 401 on both sides respectively; the end of the pull-out test channel is equipped with a spraying section to spray a layer of random black and white speckle pattern onto the steel pipe to be tested to generate a digital fingerprint; the middle of the pull-out test channel is equipped with an imaging monitoring section to capture the image deformation process during the pull-out test and collect deformation data; multiple sets of double-headed pull-out force application components 6 are all horizontally installed on the two sets of outer plates 3, and each set of double-headed pull-out force application components 6 extends out of the outer plate 3 at both ends and has a pull-out end that corresponds to the pull-out station; among them, one pull-out end is equipped with a connector 7 connected to the internal thread end of the steel pipe, and the other pull-out end is equipped with a connector 8 connected to the external thread end of the steel pipe.

[0031] During the pull-out test of the steel pipe, connector 7 and connector 8 are connected to the two ends of the steel pipe respectively. Then, the pull-out ends at both ends are synchronously controlled to apply an increasing axial tensile force to the two ends of the steel pipe at a preset loading rate. When the tensile force reaches the predetermined threshold, the system switches to the force holding mode to keep the tensile force applied to the steel pipe stable, and the imaging monitoring section collects deformation data.

[0032] like Figure 5 As shown, the through-slot 301 is arc-shaped, with the loading / unloading station and the drawing station located at opposite ends of the arc-shaped section of the through-slot 301. The arc-shaped structure of the through-slot 301 matches the rotation trajectory of the through-hole 401. During loading / unloading, the rotation of the inner side plate 4 aligns the through-slot 301 with the loading / unloading station, and the loading / unloading station is then aligned with and connected to the loading / unloading port 101, allowing steel pipes to be fed into the drawing test channel from the loading / unloading port 101. During the drawing test, the rotation of the inner side plate 4 aligns the through-slot 301 with the drawing station, and the two ends of the steel pipe are connected using connectors 7 and 8, enabling the drawing test. The working mode switching is convenient and quick, enabling batch loading / unloading and synchronous drawing tests.

[0033] like Figures 5-6 As shown, the inner side plate 4 is annular; a toothed ring 403 is provided on the outer wall of the ring. A gear 404 driven by a motor is rotatably disposed on one side of the inner side plate 4 and meshes with the toothed ring 403. A through hole 401 is provided along the ring body, and a moving part 402 acting on the steel pipe is provided in the through hole 401. Through the cooperation of the gear 404 and the toothed ring 403, the inner side plate 4 rotates at its origin, thereby driving the through hole 401 to move synchronously, so as to switch its connection with the loading / unloading station or the drawing station.

[0034] like Figures 5-6 As shown, the movable component 402 includes a mounting cylinder 40201 located within the through hole 401; a ring of electrically controlled telescopic lifting platforms 40202 is provided on the inner wall of the mounting cylinder 40201; multiple sets of lifting platforms 40202 are alternately equipped with a first movable head 40203 and a second movable head 40204; the first movable head 40203 and the second movable head 40204 are equipped with electrically driven moving wheels with alternating rotation directions, the former driving the steel pipe to rotate along its length, and the latter driving the steel pipe to rotate along its circumference; the loading and unloading port 101 is located on the rotation trajectory of the through hole 401, and the second movable component, with the same structure as the first movable component 402, is provided inside the loading and unloading port 101. During loading and unloading, the through hole 401 is adjusted to be opposite to the loading and unloading port 101 on the same side by rotating the inner side plate 4. Then, one end of the steel pipe is inserted into the loading and unloading port 101, extending through the loading and unloading station and the through hole 401 until it enters the pull-out test channel. The first movable component 402 extends and retracts via the lifting platform 40202, and is pushed by the first movable head 40203 and the second movable head 40204, thereby driving the steel pipe to rotate and move. The second movable component operates in the same way as the first movable component 402. This provides support and adjustment for both sections of the steel pipe, ensuring it passes through the pull-out test channel in a horizontal state to guarantee the accuracy of the coating. Finally, the steel pipe extends from the other end of the pull-out test channel. The first movable components 402 on both sides further maintain the horizontal state of the steel pipe during the pull-out test to ensure the accuracy of the force applied and the photographic results.

[0035] like Figures 7-8 As shown, the pull-out test assembly 5 includes a pull-out test tube 501 with corresponding side through holes 401 at both ends; a pull-out test channel is set inside the pull-out test tube 501; a spraying element is set at the spraying section corresponding to the pull-out test tube 501, and an imaging monitoring element 504 is set at the imaging monitoring section corresponding to the pull-out test tube 501; a sealed pull-out test channel is formed by setting the pull-out test tube 501 to control the test environment and ensure the accuracy of the test.

[0036] It should be further explained that the sprayed component includes a spray frame 502 located at the opening of the pull-out test tube 501; the spray frame 502 is connected to an external paint storage device via a pipe 503; the spray frame 502 is annular, with the spray nozzles arranged along its circumference. After the steel pipe enters the pull-out test tube 501, the annular spray frame 502 sprays the outer wall of the steel pipe from all directions through the rotation and movement of the steel pipe. The sprayed steel pipe moves forward suspended in the sealed pull-out test channel until its end extends out of the other opening of the pull-out test tube 501. The entire process has a low probability of contamination, making the spraying precise and efficient.

[0037] It should be further explained that the imaging monitoring components 504 are arranged in multiple sets. Each set of imaging monitoring components 504 includes an imaging monitoring sleeve 50401 that moves horizontally within the pull-out test channel along the length of the pull-out test tube 501. The inner wall of the imaging monitoring sleeve 50401 is provided with a centrally located annular track 50403 and brightness adjustment areas 50402 located on both sides of the annular track 50403. The imaging device 50404 moves in a circular trajectory by sliding along the annular track 50403. LED lights are arranged in the brightness adjustment areas 50402 along the annular trajectory. A lead screw driven by a motor is installed inside the pull-out test tube 501; the imaging monitoring sleeve 50401 achieves horizontal movement through a threaded connection with the lead screw, providing comprehensive monitoring.

[0038] The specific monitoring methods are as follows:

[0039] Step 1: Digital "fingerprint" preparation and high-definition imaging – this is the foundation of the measurement, ensuring the system has traceable markings. A high-contrast, random black-and-white speckle pattern is sprayed (or brushed) onto the surface of the steel pipe. This pattern is the sample's unique "digital fingerprint," with each local area having a unique speckle distribution. The system uses an imaging device 50404, a high-resolution digital camera, in conjunction with a telecentric lens for imaging. The telecentric lens is crucial; it ensures that within a certain depth of field, even with minute object movements, the image size remains unchanged, eliminating perspective errors and guaranteeing the geometric accuracy of the measurement.

[0040] The second step involves the core algorithm (DIC) for tracking and calculation, which is based on digital image correlation algorithms. The software divides the first image before deformation into many virtual "computational sub-regions" (each sub-region contains a unique speckle cluster). As the steel pipe deforms, the algorithm automatically and with high precision searches for the new position of each sub-region in subsequent images. To achieve micrometer (μm) level displacement measurement accuracy, the algorithm does not simply match pixels, but calculates a finer displacement than a single physical pixel—i.e., "sub-pixel" accuracy—through mathematical interpolation of grayscale value distribution (such as quadratic surface fitting).

[0041] Step 3: Data generation from displacement to strain. After the algorithm calculates the displacement vector (including X and Y directions) at each calculation point, it performs further mathematical processing (such as differentiating the displacement field) to obtain the strain distribution (such as longitudinal strain and transverse strain) at all points in the entire field. The results can generate a color strain contour map in real time, visually showing where the specimen deforms greatly and where it deforms little. Users can define one or more virtual "gauge length segments" in the software (for example, selecting two points on the specimen). The system will automatically calculate the average strain within the gauge length and output a stress-strain curve synchronized with the force value of the test device in real time. Based on this stress-strain curve, the pull-out test results of the steel pipe can be obtained.

[0042] like Figures 3-4 As shown, the double-headed pulling force assembly 6 includes multiple sets of double-headed force applicators 601 disposed between two sets of outer side plates 3 and a pulling force frame 602 disposed on the outside of the two sets of outer side plates 3; the multiple sets of double-headed force applicators 601 are divided into inner and outer rings, and the double-headed force applicators 601 of the inner and outer rings are paired and cooperated. The double-headed force applicators 601 of the inner ring are disposed along the inner hole of the inner side plate 4, and the double-headed force applicators 601 of the outer ring are disposed along the outer periphery of the inner side plate 4; the pulling force frame 602 is the pulling end, including a frame body 60201; the position of the frame body 60201 corresponds one-to-one with the pulling station, and the two ends are respectively connected to the force application ends of the paired inner and outer ring double-headed force applicators 601 through the fixing frame 60202; the middle of the frame body 60201 is provided with a mounting platform 60203 connected to the connector 7 or the connector 8.

[0043] It should be further explained that the double-headed force applicator 601 can be configured as a double-acting hydraulic cylinder. By applying force to both ends through the double-headed force applicator 601, the force applicator frame 602 is pulled to both sides, thereby achieving the purpose of pulling the steel pipe at both ends to meet the test requirements.

[0044] like Figure 9 As shown, connector 7 includes a rotating seat 702 that is rotatably connected to mounting platform 60203 via a motor drive; a threaded post 705 is provided at the center of the rotating seat 702, which is threaded to the internal thread end of the steel pipe; a limiting sleeve 701 is provided on the outer periphery of the rotating seat 702, which is threaded to the outer wall of the steel pipe; an annular steel pipe connecting cavity is formed between the limiting sleeve 701 and the threaded post 705; a secondary limiting cylinder 703 is fitted on the outside of the limiting sleeve 701; the secondary limiting cylinder 703 is threaded to the limiting sleeve 701, and an anti-slip ring 704 is provided on the opening of the secondary limiting cylinder 703, which is threaded to the outer wall of the steel pipe.

[0045] like Figure 10As shown, connector 2 8 includes a rotating seat 2 802 that is rotatably connected to mounting platform 60203 via a motor drive; a limiting post 805 that mates with the inner wall of the steel pipe is provided at the center of the rotating seat 2 802, and a threaded sleeve 801 that mates with the external thread end of the steel pipe is provided on the outer periphery of the rotating seat 2 802; an annular steel pipe connecting cavity 2 is formed between the threaded sleeve 801 and the limiting post 805; a secondary limiting cylinder 2 803 is provided outside the threaded sleeve 801; the secondary limiting cylinder 2 803 is threadedly engaged with the threaded sleeve 801, and an anti-slip ring 2 804 that mates with the outer wall of the steel pipe is provided on the opening of the secondary limiting cylinder 2 803.

[0046] During the drilling of slope anchor piles and mortar anchors, problems such as stuck drills, hole collapse, and inability to form holes frequently occur. Workers also encountered stuck drills when attempting self-drilling anchor installation. To ensure slope stability, workers replaced the slope anchors and anchor piles with steel pipes. The installed steel pipes were not pulled out, thus creating a situation where the steel pipes replaced the anchors. At the initial stage of anchor installation, pull-out tests should be conducted on 3% of the working anchors using the steel pipes. Since the steel pipes are connected by threads, the aforementioned device for the steel pipe pull-out test is proposed to facilitate rapid checking of the pull-out force.

[0047] To address the structural characteristics of the steel perforated pipe, connector 7 and connector 8 are installed. After the steel perforated pipe is positioned and sprayed, the two side frames 60201 move relative to each other under the action of the double-headed force applicator 601, approaching the two ends of the steel perforated pipe. As rotating seats 702 and 802 rotate, the steel perforated pipe rotates into steel pipe connection chambers 1 and 2, achieving initial fixation through threaded connections at both ends. Then, the operator tightens secondary limiting sleeves 703 and 803 respectively for secondary fixation of the connection. Further reinforcement can be achieved using screws and bolts on top of this, ensuring stable connection of the steel perforated pipe during the pull-out test.

[0048] Example 2: Based on the apparatus for steel pipe pull-out testing described in the above examples, this example proposes a method for steel pipe pull-out testing, with the following steps:

[0049] Phase 1: System Initialization and Steel Pipe Loading

[0050] The start-up device controls the synchronous rotation of the rotating drive frames 2 on both sides, driving the outer side plate 3 and its arc-shaped through slots 301 to rotate until the loading and unloading ports of all through slots 301 are precisely aligned with the loading and unloading ports 101 on the side of the mounting base 1. At the same time, the drive gear 404 drives the gear ring 403, causing the inner ring plate 4 to rotate, so that its upper ring of through holes 401 is also aligned with and connected to the loading and unloading ports. At this time, the pulling test channels of all pull-out test components 5 form a continuous tube-passing path with the external loading and unloading ports 101 through the through holes 401 on both sides.

[0051] One end of the steel tube to be tested is fed into the feed port 101 on one side. The second moving part (with the same structure as the first moving part 402) inside the feed port 101 and the first moving part 402 inside the through hole 401 on the inner side plate 4 work together. Specifically, the lifting platform 40202 extends, causing the electric moving wheels on the first moving head 40203 and the second moving head 40204 to contact the surface of the steel tube. By controlling the rotation of the moving wheels, the steel tube is driven to move along its axial direction (length direction) and rotate around its own axis, ensuring that the steel tube smoothly passes through the through hole 401 in a horizontal posture, enters the pull-out test channel in the corresponding pull-out test tube 501, and finally extends out from the symmetrical through hole 401 and feed port 101 on the other side. The moving parts on both sides together provide support and adjust the posture of the steel tube.

[0052] Phase Two: Preparation for Spraying and Monitoring

[0053] When the steel pipe moves to the predetermined position (spraying section) within the pull-out test channel, axial movement is paused, but uniform rotation is maintained. Spraying is then initiated: an external paint storage device supplies paint to the annular spraying frame 502 through pipe 503. The spray nozzles arranged circumferentially on the spraying frame 502 uniformly and comprehensively spray the outer wall of the uniformly rotating steel pipe, forming a high-contrast, random black-and-white speckle pattern, i.e., the "digital fingerprint" of the sample. After spraying, the steel pipe continues to move axially, allowing the sprayed section to enter the imaging monitoring section, while the unsprayed section continues to be sprayed until the entire test section is sprayed. The spraying process is conducted within the sealed pull-out test tube 501 to minimize contamination.

[0054] After all the steel pipes to be tested have been loaded and coated, the inner side plate 4 is driven to rotate at its origin again. This causes all the through holes 401 to simultaneously disengage from their alignment with the loading and unloading stations and instead align with and connect to the pulling station ports of the through slots 301 on the outer side plate 3. At the same time, each pulling force frame 602 (i.e., the pulling end) of the double-headed pulling force assembly 6 is ready in its initial position.

[0055] Phase 3: Connection Fixing and Pull-out Test

[0056] The double-headed force applicator 601 (such as a double-acting hydraulic cylinder) on one side of the connecting piece 7 is driven to push the pulling force frame 602 and its rotating seat 702 closer to the end of the steel pipe. The drive motor of the rotating seat 702 is started to rotate it, causing the threaded post 705 to screw into the internal thread end of the steel pipe, while the outer wall of the steel pipe end enters the limiting sleeve 701 until the end face of the steel pipe abuts against the rotating seat 702. Subsequently, the secondary limiting cylinder 703 is manually or automatically tightened, allowing it to advance along the thread of the limiting sleeve 701. The anti-slip ring 704 on the cylinder mouth presses against the outer wall of the steel pipe, achieving secondary locking. Simultaneously, the double-headed force applicator 601 and the pulling force frame 602 on the other side of the connecting piece 8 are driven to bring the rotating seat 802 closer to the other end of the steel pipe. The rotating seat 802 is started to rotate, causing the threaded sleeve 801 to screw into the external thread end of the steel pipe, while the inner wall of that end of the steel pipe is fitted into the limiting post 805. Similarly, tighten the secondary limiting cylinder 803, and use the anti-slip ring 804 to press the outer wall of the steel pipe to strengthen the fixation.

[0057] All paired (inner and outer ring) double-headed force applicators 601 work synchronously, applying opposing tensile forces to the pull-out force-applying frames 602 on both sides, thereby axially pulling the connected and fixed steel pipe specimen. Force data is collected in real time by sensors integrated into the force application system.

[0058] During the drawing process, the imaging monitoring device 504 is activated. Driven by a screw inside the drawing test tube 501, the imaging monitoring sleeve 50401 moves horizontally along the length of the steel tube. The imaging device 50404 (a high-resolution digital camera with a telecentric lens) inside moves in a circular motion along the annular track 50403. Combined with LED illumination in the brightness adjustment area 50402, it continuously and in high definition captures the speckle pattern already sprayed on the surface of the steel tube from different angles, obtaining an image sequence of the entire drawing process.

[0059] Phase 4: Data Processing and System Reset

[0060] The acquisition system synchronizes the pull-out force data with the image sequence. A digital image correlation algorithm is used to process the images. First, the image before deformation is divided into calculation sub-regions; then, the sub-pixel displacement of each sub-region is tracked in the image sequence after deformation; finally, the strain distribution across the entire steel pipe is calculated through displacement field, generating a color strain cloud map. The stress-strain curve for a specific virtual gauge length segment can also be extracted to comprehensively evaluate the mechanical properties of the steel pipe.

[0061] After the test, the double-headed force applicator 601 is unloaded, and the rotating seats 702 and 802 are rotated in the opposite direction to release the secondary limiting cylinders 703 and 803, thus disconnecting the connections at both ends of the steel pipe. The inner plate 4 is rotated back to realign the through hole 401 with the loading and unloading positions. The tested steel pipe is then removed from the pull-out test channel using the moving parts 402 and 402, completing the unloading process. The system returns to its initial state, ready for the next batch of steel pipe cyclic tests.

[0062] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. An apparatus for a steel pipe pull-out test, characterized in that, include: Mounting base (1), with loading and unloading ports (101) positioned opposite each other on both sides of the mounting base (1) and a rotating drive frame (2) located below the loading and unloading ports (101) on both sides. The outer side plate (3) is arranged in parallel on the rotating end of the rotating drive frame (2) on both sides, and multiple sets of corresponding through slots (301) are arranged around the rotating end; each set of through slots (301) is provided with loading and unloading stations and drawing stations. The inner side plate (4) is rotated one by one on the opposite ends of the two sets of outer side plates (3). Each set of inner side plates (4) is provided with a ring of through holes (401) that correspond one by one with the through groove (301). By rotating the inner side plate (4) at the origin, multiple sets of inner through holes (401) can be switched to connect with the loading and unloading station or the drawing station synchronously. Pull-out test assembly (5), multiple pull-out test assemblies (5) are arranged laterally between two sets of inner side plates (4), and each set of pull-out test assembly (5) is provided with a pull-out test channel; the two ends of the pull-out test channel are respectively connected to the through holes (401) on both sides, and the end of the pull-out test channel is provided with a spraying section, on which a layer of random black and white speckle pattern is sprayed onto the steel pipe to be tested to generate a digital fingerprint, and the middle of the pull-out test channel is provided with an imaging monitoring section, which takes pictures of the image deformation process during the pull-out test and collects deformation data; And a double-headed pulling force application component (6), multiple sets of double-headed pulling force application components (6) are horizontally arranged on two sets of outer side plates (3), each set of double-headed pulling force application components (6) extends out of the outer side plate (3) at both ends and has a pulling end that corresponds to the pulling station; among them, a connecting piece 1 (7) that connects to the internal thread end of the steel pipe is provided on one side of the pulling end, and a connecting piece 2 (8) that connects to the external thread end of the steel pipe is provided on the other side of the pulling end. When the steel pipe is pulled out, connector 1 (7) and connector 2 (8) are connected to the two ends of the steel pipe respectively. Then, the pull-out ends at both ends are controlled to apply an increasing axial tensile force to the two ends of the steel pipe at a preset loading rate. When the tensile force reaches the predetermined threshold, the force holding mode is switched to keep the tensile force applied to the steel pipe stable, and the imaging monitoring section collects deformation data. The pull-out test assembly (5) includes a pull-out test tube (501) with two ends connected to corresponding side through holes (401); the pull-out test channel is set inside the pull-out test tube (501); a spraying component is set at the spraying section of the pull-out test tube (501), and an imaging monitoring component (504) is set at the imaging monitoring section of the pull-out test tube (501).

2. The apparatus for steel pipe pull-out testing according to claim 1, characterized in that, The through groove (301) is set in an arc shape, and the loading and unloading station and the drawing station are respectively set at both ends of the arc section of the through groove (301); The arc-shaped structure of the through groove (301) matches the rotation trajectory of the through hole (401).

3. The apparatus for steel pipe pull-out testing according to claim 1, characterized in that, The inner side plate (4) is set as an annular ring; a toothed ring (403) is set on the outer wall of the ring; the gear (404) is rotatably set on one side of the inner side plate (4) and meshes with the toothed ring (403); A through hole (401) is provided along the ring body, and a movable part (402) that acts on the steel pipe is provided inside the through hole (401).

4. The apparatus for steel pipe pull-out testing according to claim 3, characterized in that, The first movable component (402) includes a mounting cylinder (40201) located in the through hole (401); a ring of electrically controlled telescopic lifting platforms (40202) is provided on the inner wall of the mounting cylinder (40201); and a first movable head (40203) and a second movable head (40204) are alternately arranged on multiple sets of lifting platforms (40202). The first moving head (40203) and the second moving head (40204) are equipped with electric moving wheels with alternating rotation directions. The first moving head (40203) drives the steel pipe to rotate along the length direction, and the second moving head (40204) drives the steel pipe to rotate along the circumference direction. The loading and unloading ports (101) are set on the rotation trajectory of the through hole (401), and the loading and unloading ports (101) are equipped with a second moving part with the same structure as the first moving part (402).

5. The apparatus for steel pipe pull-out testing according to claim 1, characterized in that, The sprayed part includes a spraying rack (502) located at the opening of the pull-out test tube (501); the spraying rack (502) is connected to an external paint storage device via a tube (503); The spray gun (502) is set in a ring shape, and the spray nozzle is set along its circumference.

6. The apparatus for steel pipe pull-out testing according to claim 1, characterized in that, Multiple imaging monitoring components (504) are provided. Each imaging monitoring component (504) includes an imaging monitoring sleeve (50401) that moves horizontally within the pull-out test channel along the length of the pull-out test tube (501). The inner wall of the imaging monitoring sleeve (50401) is provided with a circular track (50403) located in the middle and brightness adjustment areas (50402) located on both sides of the circular track (50403). The imaging device (50404) moves in a circular trajectory by sliding along the circular track (50403). LED lights are arranged in the brightness adjustment areas (50402) along the circular trajectory.

7. The apparatus for steel pipe pull-out testing according to claim 3, characterized in that, The double-headed pulling force assembly (6) includes multiple sets of double-headed force applicators (601) disposed between two sets of outer side plates (3) and a pulling force frame (602) disposed on the outside of the two sets of outer side plates (3). Multiple sets of double-headed force applicators (601) are divided into inner and outer rings, and the double-headed force applicators (601) of the inner and outer rings are paired and matched. The double-headed force applicators (601) of the inner ring are set along the inner hole of the inner side plate (4), and the double-headed force applicators (601) of the outer ring are set along the outer periphery of the inner side plate (4). The pulling force frame (602) is the pulling end, including the frame body (60201); the position of the frame body (60201) corresponds one-to-one with the pulling station, and the two ends are respectively connected to the force-applying ends of the inner and outer ring double-headed force applicators (601) through the fixing frame (60202). The middle part of the frame body (60201) is provided with an installation platform (60203) connected to the first connector (7) or the second connector (8).

8. The apparatus for steel pipe pull-out testing according to claim 7, characterized in that, The connector 1 (7) includes a rotating seat 1 (702) of the rotating connection mounting platform (60203); the center of the rotating seat 1 (702) is provided with a threaded post (705) that is threaded to the internal thread end of the steel pipe, and the outer periphery of the rotating seat 1 (702) is provided with a limiting sleeve (701) that is threaded to the outer wall of the steel pipe; an annular steel pipe connecting cavity 1 is formed between the limiting sleeve (701) and the threaded post (705); a secondary limiting sleeve 1 (703) is sleeved on the outside of the limiting sleeve (701); The secondary limiting cylinder (703) is threadedly engaged with the limiting sleeve (701), and the opening of the secondary limiting cylinder (703) is provided with an anti-slip ring (704) that engages with the outer wall of the steel pipe.

9. The apparatus for steel pipe pull-out testing according to claim 7, characterized in that, The second connector (8) includes a rotating seat (802) of the rotating connection mounting platform (60203); a limiting post (805) that mates with the inner wall of the steel pipe is provided at the center of the rotating seat (802); a threaded sleeve (801) that mates with the external thread end of the steel pipe is provided on the outer periphery of the rotating seat (802); an annular steel pipe connecting cavity is formed between the threaded sleeve (801) and the limiting post (805); a secondary limiting cylinder (803) is provided on the outside of the threaded sleeve (801). The secondary limiting cylinder (803) is threadedly engaged with the threaded sleeve (801), and the opening of the secondary limiting cylinder (803) is provided with an anti-slip ring (804) that engages with the outer wall of the steel pipe.

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