A low temperature bending test device for electrical wires

Abstract

The application provides a kind of electric wire low temperature bending test equipment, belongs to electric wire production equipment technical field.The equipment includes machine body, machine body is provided with test box and is provided with refrigeration equipment on test box, refrigeration equipment provides low temperature air for test box, image collector for obtaining sample state is provided in test box.It also includes bending structure, bending structure includes rotating shaft, first driving structure and chuck, rotating shaft is rotatably arranged in test box, first driving structure is arranged on the outer wall of test box to drive rotating shaft to rotate;Chuck is movably arranged in test box, and the restriction site for the sample to pass through is arranged in chuck;During the test, one end of the sample is fixed on the rotating shaft, and the opposite end passes through the restriction site and is fixedly connected with the weight.The equipment can realize automatic bending and angle control of cable test process, improve the standardization level of test, and also can monitor the sample state in real time through image collector, realize nondestructive intelligent judgment.

Description

Technical Field

[0001] This invention relates to the field of wire production equipment technology, and in particular to a low-temperature bending test device for wires. Background Technology

[0002] Cables (including power cables, communication cables, optical fibers, and various electronic wire harnesses) face the long-term challenge of operating in low-temperature environments in applications such as aerospace, polar scientific research, wind power generation, new energy vehicles, and infrastructure construction in frigid regions. Under low-temperature conditions, the insulation and sheathing materials of cables become brittle, and their flexibility significantly decreases. If subjected to bending stress during laying or use, they are highly susceptible to cracking, insulation failure, or even short-circuit faults, seriously threatening equipment operation safety and personnel safety. Therefore, low-temperature testing is necessary during the production process to evaluate cable performance.

[0003] The current low-temperature testing process is as follows: First, one end of the sample is fixed to a test bar with an iron clamp, while the other end hangs naturally with a weight suspended from it. Then, the test bar is mounted on a rotating shaft, which is driven to rotate and bend the cable. The sample is kept at a predetermined temperature for a certain period of time before being removed to test the product's performance. However, in this testing method, the sample rotation angle is usually oriented in a fixed direction, which is not conducive to comprehensive testing of the sample. In addition, testing can only be performed after the sample is removed, making it difficult to effectively capture and record microscopic changes during the testing process (such as the generation of microcracks and transient changes in material properties).

[0004] Therefore, it is necessary to improve the low-temperature bending test equipment for the wire to overcome the shortcomings of the existing technology. Summary of the Invention

[0005] To overcome the problems existing in related technologies, the purpose of this invention is to provide a low-temperature bending test device for electrical wires. This device can realize automatic bending and angle control during the cable testing process, improve the level of test standardization, and can also monitor the sample status in real time through an image acquisition device to achieve non-destructive intelligent judgment.

[0006] A low-temperature bending test device for electrical wires includes: The machine body includes a test chamber and a refrigeration device mounted on the test chamber. The refrigeration equipment provides low-temperature air to the test chamber. An image acquisition device for obtaining sample status is installed in the test chamber. The image acquisition device is electrically connected to an image processing unit, which is used to identify cracks in the images acquired by the image acquisition device. The test chamber also includes a bending structure, comprising a rotating shaft, a first driving structure, and a clamp. The rotating shaft is rotatably disposed within the test chamber, and the first driving structure is disposed on the outer wall of the test chamber to drive the rotating shaft to rotate. The clamp is movably disposed within the test chamber and has a limiting position for the sample to pass through. During the test, one end of the sample is fixed on the rotating shaft, and the other end passes through the limiting position and is fixedly connected to the weight.

[0007] In a preferred embodiment of the present invention, a plurality of slots are provided on the rotating shaft, and the plurality of slots are arranged on the surface of the rotating shaft along the axial direction of the rotating shaft; The rotating shaft is also provided with a pressure strip, which is disposed on the slot. One end of the pressure strip is hinged to the rotating shaft, and the other end is detachably locked to the rotating shaft.

[0008] In a preferred embodiment of the present invention, several rotating shafts are arranged in the test chamber, and the several rotating shafts are arranged in parallel in the vertical or horizontal direction within the test chamber.

[0009] In a preferred embodiment of the present invention, multiple clamps are provided in the test box, and each clamp is movably disposed in the test box; The test chamber is provided with a second driving structure, which drives the chuck to move in a straight line within the test chamber. The second driving structure includes a guide rail and a linear actuator. The guide rail is disposed on one side of the rotating shaft, and a slider is disposed on the guide rail. The linear actuator drives the slider to move on the guide rail, and the chuck is fixed on the slider.

[0010] In a preferred embodiment of the present invention, the clamp includes a fixing block and an adjusting block. The fixing block is provided with a first groove, and the adjusting block is provided with a second groove, the second groove corresponding to the first groove. The bottom of the adjusting block is connected to the fixed block via a connecting shaft, and the fixed block is provided with a locking element for locking the adjusting block.

[0011] In a preferred embodiment of the present invention, the test box is provided with a third driving structure, the third driving structure including a fixed plate and a movable base, the fixed plate is provided with a screw and a first motor, the output end of the first motor is fixedly connected to the screw, the screw is provided with a movable block, and one side of the movable block is fixedly connected to the movable base; The movable base is provided with a second motor and a connecting shaft. The connecting shaft is rotatably mounted on the movable base. The output end of the second motor is connected to the connecting shaft to drive the connecting shaft to rotate. One end of the connecting shaft is provided with a chuck. The chuck is provided with a plurality of limiting positions, and the plurality of limiting positions are evenly distributed on the chuck along the circumference of the chuck.

[0012] In a preferred embodiment of the present invention, a position sensor is further provided on the side of the movable block that is away from the movable base.

[0013] In a preferred embodiment of the present invention, the movable base is provided with a first mounting plate and a second mounting plate arranged in parallel, and the connecting shaft is disposed between the first mounting plate and the second mounting plate; The second mounting plate is provided with a mounting frame, and the mounting frame is provided with a limit joint. The limit joint is provided with a limit groove. One end of the connecting shaft extends to the limit groove. The connecting shaft is provided with a limit rotating block, and the limit rotating block is disposed in the limit groove.

[0014] In a preferred embodiment of the present invention, a driving cylinder is provided on the mounting frame, and the output end of the driving cylinder is fixedly connected to the limiting joint.

[0015] In a preferred embodiment of the present invention, the image acquisition device is electrically connected to the image processing unit, and the image processing unit is configured to identify cracks in the images acquired by the image acquisition device, and automatically record the current number of bends and the test temperature when a crack is identified.

[0016] The beneficial effects of this invention are as follows: This invention provides a low-temperature bending test device for electrical wires. The device includes a main body, a test chamber mounted on the main body, and a cooling device mounted on the test chamber. The cooling device provides low-temperature air to the test chamber. An image acquisition device for capturing the sample's state is installed inside the test chamber. It also includes a bending structure, comprising a rotating shaft, a first driving structure, and a clamp. The rotating shaft is rotatably mounted inside the test chamber, and the first driving structure is located on the outer wall of the test chamber to drive the rotating shaft to rotate. The clamp is movably mounted inside the test chamber and has a limiting position for the sample to pass through. During the test, one end of the sample is fixed to the rotating shaft, and the other end passes through the limiting position and is fixedly connected to a weight. In use, the device drives the rotating shaft to rotate automatically according to a preset program, achieving precise control over the bending angle, speed, and number of turns of the sample. This avoids angle deviations caused by traditional manual or mechanical limiting methods, improving the repeatability and comparability of test results. Furthermore, when the cable sample is bent, the movement of the clamp can adjust the sample's posture, thereby changing the bending angle and enabling tests at multiple angles. This simulates the sample's real-world usage scenarios, making the test results more reliable. On the other hand, the chuck is movable within the test chamber, and its limiting position guides the sample's trajectory and constrains its lateral sway. By adjusting the relative position of the chuck and the rotating shaft, it can accommodate cable samples of different diameters, lengths, and hardnesses, and can also change the bending angle or winding path, eliminating the need for frequent clamp changes and greatly expanding the equipment's applicability. Furthermore, the system continuously acquires image information of the sample surface during low-temperature bending. It can automatically identify failure phenomena such as cracks, fissures, and fractures, and record the corresponding number of bends or time, replacing subjective judgment based on manual visual inspection outside the low-temperature chamber, avoiding interference with the temperature field when the chamber is opened, and simultaneously improving testing efficiency and data traceability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the low-temperature bending test equipment for electrical wires provided in an embodiment of the present invention; Figure 2 This is a perspective view of the third driving structure provided in an embodiment of the present invention; Figure 3 This is a top view of the third driving structure provided in an embodiment of the present invention.

[0018] Figure label: 1. Body; 2. Test chamber; 3. Rotating shaft; 31. Slot; 4. Pressure bar; 5. Refrigeration equipment; 6. Clamp; 61. Limiting position; 7. Weight; 8. Second drive structure; 81. Guide rail; 811. Slider; 82. Linear actuator; 9. First drive structure; 10. Third drive structure; 101. Fixing plate; 102. Screw; 103. First motor; 104. Moving seat; 105. Connecting shaft; 106. Second motor; 107. Mounting frame; 1071. Limiting joint; 11. Position sensor. Detailed Implementation

[0019] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0020] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0021] It should be understood that although the terms "first," "second," "third," etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0022] The current low-temperature testing process for cables is as follows: First, one end of the sample is fixed to a test bar with an iron clamp, while the other end hangs naturally with a weight suspended from it. Then, the test bar is mounted on a rotating shaft, which is driven to rotate and bend the cable. The cable is kept at a predetermined temperature for a certain period of time, and then the sample is removed to test its performance. However, in this testing method, the rotation angle of the sample is usually in a fixed direction, which is not conducive to comprehensive testing of the sample. In addition, testing can only be performed after the sample is removed, making it difficult to effectively capture and record microscopic changes during the testing process (such as the generation of micro-cracks and transient changes in material properties).

[0023] Therefore, this application provides a low-temperature bending test device for electrical wires to overcome the deficiencies of the prior art.

[0024] Example like Figure 1As shown in this embodiment, a low-temperature bending test device for electrical wires is provided, including a body 1. A test chamber 2 is mounted on the body 1, and a cooling device 5 is mounted on the test chamber 2. The cooling device 5 supplies low-temperature air into the test chamber 2 to create and maintain a set low-temperature environment within the test chamber 2. An image acquisition device is installed inside the test chamber 2 to acquire real-time images of the sample's state. Specifically, the image acquisition device is electrically connected to an image processing unit, enabling it to send the acquired images to the image processing unit. The image processing unit processes the acquired images to determine the state of the electrical wire.

[0025] The device also includes a bending structure, which comprises a rotating shaft 3, a first drive structure 9, and a clamp 6. The rotating shaft 3 is rotatably disposed inside the test chamber 2. The first drive structure 9 is mounted on the outer wall of the test chamber 2, and its output end passes through the wall of the test chamber 2 and is connected to the rotating shaft 3 to drive the rotating shaft 3 to rotate automatically according to a preset program. The clamp 6 is movably disposed in the test chamber 2, and a limiting position 61 for the sample to pass through is provided in the clamp 6. During the test, one end of the sample is fixed to the rotating shaft 3, and the other end passes through the limiting position 61 on the clamp 6 and extends downward, and is fixedly connected to the weight 7. The weight 7 applies a constant axial tensile force to the sample by its own weight.

[0026] In use, the aforementioned low-temperature bending test equipment for electrical wires utilizes a first drive structure 9 to drive the rotating shaft 3 to rotate automatically according to a preset program. This allows for precise control of the bending angle, speed, and number of turns of the sample, avoiding angle deviations caused by traditional manual or mechanical limiting methods and significantly improving the repeatability and comparability of test results. Simultaneously, the movement of the clamp 6 adjusts the sample's posture, thereby changing the bending angle and enabling tests at multiple angles. This simulates the sample's real-world usage scenarios, making the test results more reliable. The clamp 6 is movable within the test chamber 2, and its limiting position guides the sample's direction and constrains its lateral sway, preventing deviation or twisting during bending. By adjusting the relative position of the clamp 6 and the rotating shaft 3, the equipment can accommodate cable samples of different diameters, lengths, and hardnesses, and can also change the bending angle or winding path without frequent clamp replacements, greatly expanding its applicability. In addition, the image acquisition device continuously acquires image information of the sample surface during the low-temperature bending process. The control system can automatically identify failure phenomena such as cracks, fissures, and fractures and record the corresponding number of bends or time. This replaces the subjective judgment of manual visual inspection outside the low-temperature chamber, avoids interference with the temperature field when the chamber is opened, and improves detection efficiency and data traceability.

[0027] Furthermore, the rotating shaft 3 has multiple slots 31, which are spaced apart along the axial direction of the rotating shaft 3. A pressure strip 4 is also provided on the rotating shaft 3, installed at the slots 31. One end of the pressure strip 4 is hinged to the rotating shaft 3, and the other end is secured to the rotating shaft 3 with a detachable locking structure (e.g., a latch or screw). When clamping the sample, the end of the sample is placed into the slot 31, and the pressure strip 4 is flipped to press and lock the sample, thus reliably fixing the end of the sample. This structure makes sample fixing simple and quick. The slots 31 prevent the sample from slipping on the surface of the rotating shaft 3, ensuring that the bending action is synchronized with the rotating shaft 3. The multiple slots 31 are distributed axially, allowing the sample to be fixed in different axial positions to accommodate samples of different lengths or adjust the starting position of the bending segment, improving clamping flexibility.

[0028] Furthermore, several rotating shafts 3 are arranged in parallel within the test chamber 2, either vertically or horizontally. Using multiple parallel rotating shafts 3 allows for simultaneous bending tests on multiple samples, significantly improving testing efficiency. Alternatively, identical samples can be installed on different rotating shafts 3, enabling comparative testing to verify the repeatability of results. Furthermore, samples of different specifications can be installed on different rotating shafts 3, achieving parallel testing of multiple varieties and further expanding the application range of the equipment.

[0029] In one embodiment, multiple chucks 6 are arranged in the test chamber 2, each chuck 6 being movably positioned within the test chamber 2. A second drive structure 8 is provided in the test chamber 2 to drive the chucks 6 to move in a linear direction. The second drive structure 8 includes a guide rail 81 and a linear actuator 82. The guide rail 81 is arranged on one side of the rotating shaft 3, and a slider 811 is mounted on the guide rail 81. The linear actuator 82 (e.g., a linear motor, cylinder, or lead screw motor) drives the slider 811 to reciprocate on the guide rail 81. The chuck 6 is fixed to the slider 811 and moves along with it. The second drive structure 8 enables automatic and precise adjustment of the chuck 6 position, eliminating the need for manual movement and improving the automation level and positioning accuracy of the test. When different bending angles need to be tested, the control system can automatically drive the chuck 6 to the target position according to preset parameters, changing the trajectory and wrap angle of the sample after passing through the limit position, thereby flexibly adjusting the bending amplitude to adapt to various test standards or complex working conditions.

[0030] Furthermore, the chuck 6 includes a fixed block and an adjusting block. The fixed block has a first groove, and the adjusting block has a second groove corresponding to the first groove. The bottom of the adjusting block is connected to the fixed block via a connecting shaft 105, and the fixed block has a locking element for locking the adjusting block. In use, the sample is placed between the first and second grooves, the adjusting block is rotated to close the two grooves to form a limiting position, and then the adjusting block is fixed by the locking element. This structure allows the size of the limiting position to be adjusted according to the actual diameter of the sample, ensuring that the limiting position can both restrain the lateral swing of the sample and prevent excessive compression that could cause damage; the locking element ensures that the adjusting block will not loosen during testing, improving the stability and safety of the test.

[0031] In another implementation, such as Figures 2-3 As shown. A third drive structure 10 is provided in the test chamber 2. The third drive structure 10 includes a fixed plate 101 and a movable base 104. A screw 102 and a first motor 103 are provided on the fixed plate 101. The output end of the first motor 103 is fixedly connected to the screw 102. A movable block is sleeved on the screw 102, and one side of the movable block is fixedly connected to the movable base 104. When the first motor 103 drives the screw 102 to rotate, the movable block drives the movable base 104 to move along the axis of the screw 102. A second motor 106 and a connecting shaft 105 are provided on the movable base 104. The connecting shaft 105 is rotatably mounted on the movable base 104. The output end of the second motor 106 is connected to the connecting shaft 105 to drive the connecting shaft 105 to rotate. A chuck 6 is provided at one end of the connecting shaft 105. Multiple limiting positions are provided on the chuck 6, and these limiting positions are evenly distributed along the circumference of the chuck 6. The third drive structure 10 achieves automatic control of two degrees of freedom for the chuck 6: translation (driven by the first motor 103) and rotation (driven by the second motor 106) within the plane. The first motor 103 adjusts the distance and relative angle between the chuck 6 and the rotating shaft 3, while the second motor 106 rotates the chuck 6 to align the limiting positions of different sizes or shapes with the sample, thereby quickly switching bending paths or adapting to different cable specifications. Compared to manually changing fixtures, this structure significantly shortens changeover time, improves testing efficiency, and enables dynamic adjustments during testing, providing a hardware foundation for complex procedural testing.

[0032] Furthermore, a position sensor 11 is also provided on the side of the moving block away from the moving seat 104. The position sensor 11 detects the position of the moving seat 104 in real time and feeds it back to the control system, forming a closed-loop control, thereby achieving precise positioning of the moving seat 104, avoiding positioning errors caused by stepper motor step loss or mechanical backlash, ensuring that the chuck 6 can reach the preset accurate position in each test, and further improving the repeatability and reliability of the test results. In a more specific embodiment, the position sensor 11 is used to detect the actual position of the moving block and the moving seat 104 fixedly connected to it in real time along the axis of the screw 102, and feeds the position signal back to the controller of the device. Preferably, the position sensor 11 is a non-contact position sensor, such as a magnetostrictive displacement sensor, a laser displacement sensor, a Hall effect position sensor, or a photoelectric position sensor. Using a non-contact method can avoid wear and measurement errors caused by mechanical contact in low-temperature environments, and improve the reliability and service life of the detection. In one embodiment, the position sensor 11 is a linear Hall sensor, which includes a sensing magnetic strip and a Hall sensing element. The inductive magnetic strip is fixedly mounted on the fixed plate 101 along the axial direction of the screw 102, and the Hall sensor is fixedly mounted on the movable block, moving together with the movable block. When the movable block moves along the screw 102, the Hall sensor is displaced relative to the inductive magnetic strip, thereby outputting an electrical signal proportional to the displacement. This electrical signal is amplified and filtered by the signal conditioning circuit before being transmitted to the controller of the device.

[0033] Furthermore, the movable base 104 is provided with a first mounting plate and a second mounting plate arranged in parallel, and the connecting shaft 105 is installed between the first mounting plate and the second mounting plate. A mounting frame 107 is fixed on the second mounting plate, and a limit joint 1071 is provided on the mounting frame 107, with a limit groove formed on the limit joint 1071. One end of the connecting shaft 105 extends to the limit groove, and a limit rotating block is fixed on the connecting shaft 105, which is located within the limit groove. The size and shape of the limit groove restrict the rotation angle range of the limit rotating block, thereby mechanically limiting the rotation angle of the connecting shaft 105. This mechanical limiting structure, as a supplement to the software limiting, can prevent the connecting shaft 105 from exceeding the safe rotation range even if the motor malfunctions or the control signal is abnormal, thereby avoiding accidental breakage of the sample due to excessive bending or collision inside the equipment, improving the safety and reliability of the equipment operation.

[0034] Furthermore, a drive cylinder is installed on the mounting frame 107, and the output end of the drive cylinder is fixedly connected to the limit joint 1071. The drive cylinder can move the limit joint 1071, thereby dynamically changing the effective range of the limit groove and achieving online adjustment of the bending angle. This design makes the mechanical limit angle threshold no longer a fixed value, but can be adjusted in real time according to the test procedure, increasing the flexibility of the bending angle without sacrificing safety. For example, different maximum bending angles can be set at different stages of the test, or different limit angles can be set for different samples, further expanding the equipment's ability to handle complex test schemes.

[0035] Example 2 This embodiment provides another way to use the low-temperature bending test equipment for electrical wires, as follows: The image acquisition unit is electrically connected to the image processing unit, which is configured to identify cracks in the images acquired by the image acquisition unit and automatically record the current number of bends and the test temperature when a crack is identified. More preferably, the image processing unit is located in a controller, which also includes a crack evolution analysis unit. The crack evolution analysis unit records the time of the first crack appearance and the number of bends, calculates the crack propagation rate, and performs material toughness assessment in conjunction with mechanical parameters (tensile force). In a more preferred embodiment, the image acquisition unit can also be driven to move via a drive structure. In this design, the image acquisition unit moves with the clamp 6, thereby dynamically acquiring images of the wire bending. More preferably, in practical applications, the camera lens of the image acquisition unit should be equipped with a heating window or air blowing device to prevent frost or fogging on the lens surface due to temperature differences. An industrial camera and light source with an operating temperature range covering the test requirements (e.g., -60℃ to +50℃) should be selected. The cables powering the image acquisition unit and other equipment should also be low-temperature resistant cables, and the test chamber should be sealed to prevent cold air leakage.

[0036] Specifically, the image acquisition device installed inside the test chamber 2 is a high-definition industrial camera, with its lens facing the bending area of ​​the sample, used to acquire images of the sample surface in real time during the low-temperature bending process. The image acquisition device is electrically connected to an image processing unit. This image processing unit can be integrated into the device's controller or it can be a stand-alone industrial control computer.

[0037] The image processing unit is configured to receive image data transmitted in real time from the image acquisition unit and perform online analysis of the images using a built-in, pre-trained crack recognition model (such as a semantic segmentation or object detection model based on deep learning). This model can automatically identify whether cracks or other failure phenomena have occurred on the surface of the sample. When the crack recognition model identifies a crack in a single frame or multiple consecutive frames of images, the image processing unit immediately determines that the sample has failed and automatically records the number of bends (i.e., the cumulative number of rotations or reciprocations of the shaft 3) and the real-time test temperature inside the test chamber 2.

[0038] One specific implementation of this embodiment is as follows: The image acquisition device consists of two high-resolution industrial cameras (e.g., 5-megapixel CMOS cameras, frame rate ≥30fps), installed at different angles within the test chamber 2: one facing the outer side of the bending area of ​​the sample (the tensile side), and the other installed at a 45° angle to capture side cracks. Both cameras are equipped with LED ring light sources, the color temperature and intensity of which are adjustable, and they are low-temperature adaptable (operating temperature range covering -60℃ to +50℃). The start and stop of the cameras and light sources are uniformly controlled by a controller, triggering acquisition only during the bending action or at set time intervals (e.g., every 0.5 seconds) to reduce the amount of data.

[0039] The image processing unit is an industrial control computer (IPC) with a built-in NVIDIA Jetson Orin or equivalent GPU module. The computer connects to the camera via a GigE interface and communicates with the equipment's main controller (PLC) via an EtherCAT bus to acquire real-time data on the current number of bends (cumulative rotations) of shaft 3 and the temperature value inside test chamber 2 (from a temperature sensor). The computer is internally equipped with a real-time operating system (such as Ubuntu + PREEMPT_RT) and a deep learning inference engine (such as TensorRT).

[0040] 2. Pre-training of the crack recognition model 2.1 Sample Collection and Labeling Under the same low-temperature testing environment (-40℃, -25℃, -10℃), a large number of wire samples were collected using the same equipment, capturing images of the bending process. The images covered different wire diameters (0.5mm² to 6mm²), different insulation materials (PVC, XLPE, TPE), and different crack morphologies (microcracks, single cracks, network cracks, splitting, and fracture). A total of 10,000 images were collected, including 5,000 images of various types of cracks and 5,000 images of intact wires without cracks.

[0041] Three materials testing experts used professional annotation tools (such as LabelMe) to perform pixel-level semantic segmentation annotation of the cracked areas in the image. The annotation categories included: background, crack area (thin line), and open crack area (opening width > 0.1 mm). After annotation, the corresponding mask image was generated.

[0042] Choose a deep learning-based semantic segmentation network, such as U-Net, DeepLabV3+, or the lightweight BiSeNetV2. Use ResNet-34 or MobileNetV3 as the backbone network to balance accuracy and inference speed. The training process employs transfer learning: first pre-train on a large general dataset (such as Cityscapes), and then fine-tune on a self-built cable crack image dataset.

[0043] Training parameters: Loss function: Cross-entropy loss + Dice loss (to address the problem of class imbalance in cracked pixels) Optimizer: AdamW, initial learning rate 1e-4, using cosine annealing decay.

[0044] Batch size: 8 Training rounds: 100 rounds, early stopping strategy (stop if the validation set loss does not decrease for 10 consecutive rounds). After training, the model achieved an average crossover ratio (mIoU) of 0.87 on an independent validation set (2,000 images) and an IoU of 0.79 for the crack category, meeting the requirements for real-time online detection.

[0045] The trained PyTorch model was converted to ONNX format and then FP16 quantization inference was performed using TensorRT. The single-frame inference time on Jetson Orin was less than 15ms, which meets the requirements for 30fps real-time analysis.

[0046] After the test begins, the main controller drives the rotating shaft 3 to rotate at a preset bending speed (e.g., 5 revolutions per minute). Simultaneously, the main controller sends a trigger signal to the image processing unit every 0.5 seconds, and the image processing unit controls the camera to synchronously acquire one frame of image (one from each of the left and right perspectives). The acquired raw images are first preprocessed: Cropping: Remove irrelevant areas at the edges, retaining the bent section of the sample (approximately 300×300 pixels). Normalization: Maps pixel values ​​from [0, 255] to [0, 1]. Enhancement: Crack contrast is enhanced using Adaptive Histogram Equalization (CLAHE). The preprocessed image is input into a deep learning model for inference. The model outputs a probability map of the same size as the input, showing the probability of each pixel belonging to one of three categories: "background," "crack," or "fracture." To reduce false positives, post-processing employs the following logic: Morphological filtering: Perform an opening operation (erosion followed by dilation) on the binary mask of the "crack" category to remove isolated noise points with an area of ​​less than 10 pixels.

[0047] Region connectivity analysis: Extract all connected components and calculate the aspect ratio and minimum bounding rectangle length of each component. If the aspect ratio of a connected component is greater than 5 and the rectangle length is greater than 20 pixels (corresponding to an actual physical size of approximately 0.5 mm), it is considered a valid crack.

[0048] Consecutive frame confirmation: To prevent false detections in a single frame (such as dust or light reflection), a true failure is confirmed only if "at least two out of three consecutive frames detect a crack at the same location". The crack location is correlated using optical flow tracing or feature matching.

[0049] When the above conditions are met, the image processing unit determines that the sample has failed.

[0050] Once a failure is detected, the image processing unit immediately sends a "failure event" signal to the main controller via EtherCAT, requesting the current number of bends and temperature. Upon the main controller's response, the image processing unit records the following information to its local SQLite database and a network shared folder: Expiration time: System timestamp accurate to milliseconds Bending count: The total number of rotations (or reciprocating cycles) of the shaft, unit: times. Test temperature: Current temperature sensor reading inside the test chamber, unit: °C Image evidence: The original image of the frame that triggered the failure and the superimposed image with the crack outline marked on it. Crack quantification parameters: maximum crack length (pixel to millimeter), crack area, crack orientation (specific coordinates on the sample).

[0051] Meanwhile, the main controller can choose, depending on the configuration, whether to immediately stop the bending test of the sample (to protect the equipment or prevent crack propagation from contaminating the data), or to continue running to observe the crack propagation process.

[0052] A detailed test example is as follows: Instance parameters: Sample: 1.5mm² PVC insulated wire, 300mm in length Temperature: -20℃ Bending speed: 10 revolutions per minute (180° each way). Weight: 500g Test Procedure: After the test began, the image processing unit continuously analyzed the image. During the 42nd bend (21 complete forward and reverse cycles), the model identified a microcrack 1.2 mm long and approximately 0.05 mm wide (98.7% confidence level) in the outer arc apex region of the bend. After confirmation over three consecutive frames, the system determined failure upon completion of the 42nd bend. The recorded data is as follows: Failure event triggered Number of bends: 42 Temperature: -20.1℃ Maximum crack length: 1.24 mm Crack area: 0.031 mm² Failed image save path: xx The test report is automatically generated and includes crack images, crack parameter evolution curves (if monitoring continues), and comparison charts with historical data.

[0053] More preferably, to further evaluate the material's resistance to low-temperature bending and its failure evolution, the controller also includes a crack evolution analysis unit. This unit is connected to the image processing unit and / or the device's storage module, and its functions include: Crack initiation record: Record the time point when the crack is first identified and the corresponding number of bends, which is used as the "crack initiation life" of the sample.

[0054] Crack propagation analysis: After a crack appears, the changes in the crack's length, width, or area are continuously tracked and analyzed in subsequent images. Through continuous monitoring, the crack propagation rate per unit number of bends or per unit time is calculated, thereby quantifying the material's resistance to crack propagation.

[0055] Multi-parameter coupled evaluation: This unit can also be coupled with a tensile sensor (e.g., for detecting the actual tensile force fluctuations applied to the sample by the weight 7) or a torque sensor (for detecting the bending torque of the shaft 3) on the equipment. By combining real-time mechanical parameters (such as tensile force decay and abnormal torque fluctuations) with the visually observed crack evolution state, the low-temperature toughness of the material is comprehensively evaluated, generating a more comprehensive material performance report.

[0056] This application provides a specific embodiment as follows: A PVC insulated wire with a nominal cross-sectional area of ​​2.5 mm² was subjected to a bending test in a test chamber 2 at -40℃. The rotating shaft 3 was bent back and forth at a speed of 5 revolutions per minute. The image processing unit analyzed the image in real time. At the 28th bend, the crack recognition model identified a microcrack with a length of 0.3 mm on the outer surface of the bent sample. The crack evolution analysis unit immediately recorded "Crack initiation bend count: 28". The test continued until the 45th bend, when the crack had expanded to 2.1 mm, and the calculated average propagation rate was approximately 0.12 mm / bend. Finally, the crack propagation rate was compared with other samples from the same batch in the test report, providing accurate and quantitative data for evaluating the service life and material toughness of the wire in extremely cold environments.

[0057] 1. Architecture and data interface of the crack evolution analysis unit The crack evolution analysis unit is integrated into the equipment's controller (or industrial control computer) as a software module. This unit communicates in real time with the image processing unit, the equipment's main controller, and the data storage module to acquire the following three types of data streams: The crack evolution analysis unit maintains a crack parameter evolution table, with the number of bends as the horizontal axis, recording the key crack parameters observed each time.

[0058] 2. Recording and threshold determination of crack initiation During the test, the image processing unit continuously runs the deep learning crack recognition model (see Example 3). When the model detects a crack in a frame that meets the following conditions, it is determined to be a "crack initiation event": Crack length ≥ 0.2mm (based on camera calibration results, converted from pixels to physical size) Crack width ≥ 0.02 mm The presence of the crack is confirmed in at least two out of three consecutive frames, and the crack is located at the apex of the bending arc on the outer surface of the specimen (tensile side). For example, a bending test was performed on a 2.5mm² XLPE insulated wire at a low temperature of -40℃. The shaft was bent back and forth at a speed of 5 revolutions per minute. When the bending was completed for the 28th time (i.e., the shaft had rotated a total of 28 times or 28 half cycles), the crack recognition model identified a microcrack located at the apex of the bending arc on the outside of the sample from the image. Its measured length was 0.3mm and its width was approximately 0.03mm.

[0059] The image processing unit immediately sends the crack location, length, corresponding image frame, and timestamp to the crack evolution analysis unit. This unit then creates a crack evolution record for the sample in the database. The record fields include: Sample ID: SAMPLE-02 Crack initiation and bending times: 28 times Temperature at germination time: -40.2℃ Initial crack length: 0.30 mm Generated image path: xxxxx At the same time, the unit can trigger the controller to attach a mark on the test channel and write "crack initiation life: 28 times" in the test report draft.

[0060] 3. Continuous tracking and parameter calculation of crack propagation After crack initiation, the test continues. The image processing unit tracks the same crack region in each subsequent image acquisition (e.g., every 0.5 seconds or every half-bend). The crack evolution analysis unit uses a feature point matching-based tracking algorithm to associate the crack detected in the current frame with the crack in the previous frame. Specifically: Starting from the geometric center of the crack in the crack initiation frame, extract the surrounding ORB feature points. The same crack is located in subsequent frames using optical flow or feature matching. Remeasure the crack length (accumulated pixels along the main crack skeleton line and converted to millimeters), maximum width, and area.

[0061] Whenever the crack length changes significantly (more than 0.05 mm), a new data point is recorded for each element.

[0062] Example continued: After the crack initiation, the test continued. When the number of bends reached 35, the crack extended to 0.8 mm; at the 40th bend, the crack extended to 1.5 mm; and at the 45th bend, the crack length reached 2.1 mm.

[0063] The crack evolution analysis unit automatically records the following data points: Based on the above data, the crack evolution analysis unit calculates the average crack propagation rate using the following formula: in The final crack length is 2.1 mm. The initial crack length is 0.3 mm. This represents the final number of bends (45). This represents the number of initial bends (28). The calculation yields: If the user chooses to calculate by time, the time unit will be converted based on the bending speed (5 revolutions per minute, or 12 seconds per revolution): Germination time = 28 times × 12 seconds / time = 336 seconds Final time = 45 times × 12 seconds / time = 540 seconds Extended time = 204 seconds Based on the time-spreading rate ≈ 1.8 mm / 204 s ≈ 0.0088 mm / s The report states: "During 28 to 45 bends, the average crack propagation rate was 0.11 mm / bend (approximately 0.0088 mm / s)," which is basically consistent with "0.12 mm / bend" in the title (the slight difference is due to measurement accuracy and step size).

[0064] 4. Multi-stage spread rate and nonlinear analysis To more precisely assess a material's resistance to crack propagation, the crack evolution analysis unit can further calculate segmented propagation rates. For example, the crack propagation process can be divided into initial (28-35 cycles), intermediate (35-40 cycles), and late (40-45 cycles): Initial velocity: (0.80-0.30) / (35-28)=0.50 / 7≈0.071mm / cycle Medium-term rate: (1.50-0.80) / (40-35)=0.70 / 5=0.14mm / cycle Later speed: (2.10-1.50) / (45-40)=0.60 / 5=0.12mm / cycle Analysis shows that the crack propagation rate accelerates with increasing number of bends. This phenomenon can be used to determine whether a material is undergoing a transition from ductile to brittle, or to predict its remaining life.

[0065] The unit automatically generates a crack propagation curve (bending number on the horizontal axis and crack length on the vertical axis), and fits it using an exponential or power function, outputting the propagation coefficients. For example, the fitted curve is... In terms of form, the larger the b value, the worse the material's resistance to cracking.

[0066] 5. Material toughness assessment integrating mechanical parameters To further improve the accuracy of the assessment, the crack evolution analysis unit can read the mechanical parameters at the same moment (if the equipment is equipped with force / torque sensors). Specifically: Tensile stress fluctuation: As the crack propagates, the effective cross-sectional area of ​​the specimen decreases, and the constant tensile force applied by the weights leads to an increase in the internal stress of the specimen. By detecting the dynamic fluctuations (which should be essentially constant under normal circumstances) on the tensile sensor, the effect of the crack on the specimen's load-bearing capacity can be verified.

[0067] Bending moment variation: The appearance and propagation of cracks reduce the bending stiffness of the specimen, leading to a decrease in the bending moment on the shaft. The element analyzes the superposition of the bending moment curve and the crack length curve to find the critical point where the moment begins to decrease significantly. This point often occurs earlier than the stage where the crack is visible to the naked eye, and can serve as a more sensitive failure early warning indicator.

[0068] Example: In the above test, the torque sensor data showed that the bending torque had decreased by 2% at the 25th bend (the 3rd before crack initiation); the torque decreased by 5% at the 28th crack initiation; and the torque decreased by 18% when the crack extended to 2.1mm at the 45th bend. The unit correlated these data to generate a "Force-Crack Propagation Comprehensive Report".

[0069] 6. Output and Report Generation The crack evolution analysis unit generates the following data output after the test (or in real time): Crack initiation lifespan: 28 cycles (or corresponding time). Crack propagation rate: average 0.11 mm / crack, segmentation rate as above. Crack propagation fitting equation: (Example) Mechanics-Crack Correlation Curve: Comparison of Torque Decrease Curve and Crack Length Curve Material toughness rating: Based on a preset algorithm (e.g., the lower the propagation rate and the later the initiation, the higher the score), a toughness index of 0-100 is given. The above data is saved in JSON and PDF formats and can be exported as an attachment to a test report for use in material research and development comparison or quality control release.

[0070] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings. In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0071] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0072] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. 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 low-temperature bending test device for electrical wires, characterized in that, include: The machine body is equipped with a test chamber and a refrigeration device on the test chamber. The refrigeration device provides low-temperature air to the test chamber. An image acquisition device for acquiring the state of the sample is installed in the test chamber. The image acquisition device is electrically connected to an image processing unit. The image processing unit is used to identify cracks in the images acquired by the image acquisition device. It also includes a bending structure, which includes a rotating shaft, a first driving structure, and a clamp. The rotating shaft is rotatably disposed in the test chamber, and the first driving structure is disposed on the outer wall of the test chamber to drive the rotating shaft to rotate. The clamp is movably disposed in the test chamber, and the clamp is provided with a limiting position for the sample to pass through. During the test, one end of the sample is fixed on the rotating shaft, and the other end passes through the limiting position and is fixedly connected to the weight.

2. The low-temperature bending test equipment for electrical wires according to claim 1, characterized in that: The rotating shaft has multiple slots, which are arranged on the surface of the rotating shaft along the axial direction of the rotating shaft. The rotating shaft is also provided with a pressure strip, which is disposed on the slot. One end of the pressure strip is hinged to the rotating shaft, and the other end is detachably locked to the rotating shaft.

3. The low-temperature bending test equipment for electrical wires according to claim 2, characterized in that: Several shafts are arranged in the test chamber, and these shafts are arranged in parallel in the vertical or horizontal direction within the test chamber.

4. The low-temperature bending test equipment for electrical wires according to claim 3, characterized in that: Multiple clamps are provided in the test box, and each clamp is movable within the test box; The test chamber is provided with a second driving structure, which drives the chuck to move in a straight line within the test chamber. The second driving structure includes a guide rail and a linear actuator. The guide rail is disposed on one side of the rotating shaft, and a slider is disposed on the guide rail. The linear actuator drives the slider to move on the guide rail, and the chuck is fixed on the slider.

5. The low-temperature bending test equipment for electrical wires according to any one of claims 1-4, characterized in that: The clamp includes a fixing block and an adjusting block. The fixing block is provided with a first groove, and the adjusting block is provided with a second groove, the second groove corresponding to the first groove. The bottom of the adjusting block is connected to the fixed block via a connecting shaft, and the fixed block is provided with a locking element for locking the adjusting block.

6. The low-temperature bending test equipment for electrical wires according to claim 1, characterized in that: The test box is equipped with a third drive structure, which includes a fixed plate and a movable base. The fixed plate is equipped with a screw and a first motor. The output end of the first motor is fixedly connected to the screw. A movable block is provided on the screw, and one side of the movable block is fixedly connected to the movable base. The movable base is provided with a second motor and a connecting shaft. The connecting shaft is rotatably mounted on the movable base. The output end of the second motor is connected to the connecting shaft to drive the connecting shaft to rotate. One end of the connecting shaft is provided with a chuck. The chuck is provided with a plurality of limiting positions, and the plurality of limiting positions are evenly distributed on the chuck along the circumference of the chuck.

7. The low-temperature bending test equipment for electrical wires according to claim 6, characterized in that: A position sensor is also provided on the side of the movable block that is away from the movable base.

8. The low-temperature bending test equipment for electrical wires according to claim 6, characterized in that: The movable base is provided with a first mounting plate and a second mounting plate arranged in parallel, and the connecting shaft is disposed between the first mounting plate and the second mounting plate; The second mounting plate is provided with a mounting frame, and the mounting frame is provided with a limit joint. The limit joint is provided with a limit groove. One end of the connecting shaft extends to the limit groove. The connecting shaft is provided with a limit rotating block, and the limit rotating block is disposed in the limit groove.

9. The low-temperature bending test equipment for electrical wires according to claim 8, characterized in that: A drive cylinder is provided on the mounting frame, and the output end of the drive cylinder is fixedly connected to the limit joint.

10. The low-temperature bending test equipment for electrical wires according to claim 1, characterized in that: The image acquisition device is electrically connected to the image processing unit. The image processing unit is configured to identify cracks in the images acquired by the image acquisition device and automatically record the current number of bends and the test temperature when a crack is identified.

Images