Weather resistance evaluation method of cable material in stress state, application of weather resistance evaluation method and clamp

Abstract

The invention provides a weather resistance evaluation method of a cable material in a stress state, application of the weather resistance evaluation method and a clamp. The weather resistance evaluation method comprises the following steps: (1) calculating the stretch rate of an outer sheath of a cable; (2) preparing an outer sheath material to be tested into a dumbbell-shaped test piece; (3) the dumbbell-shaped test piece is placed in a clamp, the dumbbell-shaped test piece is stretched, and the stretching rate is P; (4) dividing the dumbbell-shaped test pieces into three groups, placing one group in a dry and dark place, placing the other two groups in an ultraviolet weather-proof test box, and carrying out an artificial accelerated aging test; (5) taking out one group of dumbbell-shaped test pieces placed in the ultraviolet light weather-proof test box after T1 time, and taking out the other group of dumbbell-shaped test pieces placed in the ultraviolet light weather-proof test box after T2 time; and (6) respectively carrying out performance test on the three groups of dumbbell-shaped test pieces. By adopting the evaluation method provided by the invention, the risk of misjudgment on the material can be greatly reduced.

Description

Technical Field

[0001] This invention belongs to the technical field of weather resistance performance evaluation methods, and relates to a method for evaluating the weather resistance performance of cable materials under stress, its application, and a fixture. Background Technology

[0002] As power systems expand into more complex environments, the weather resistance of cables has become a core issue in ensuring power grid reliability. The cable outer sheath is the core barrier protecting cables from environmental corrosion (such as ultraviolet radiation, temperature changes, and mechanical stress), and its performance directly affects the cable's lifespan and the reliability of the power system.

[0003] When cables are laid outdoors for extended periods, their outer sheaths are susceptible to severe damage due to the combined effects of various environmental factors. The main reasons can be summarized as follows:

[0004] 1. Continuous ultraviolet (UV) radiation in outdoor environments can trigger photodegradation of the sheath material. Under UV light, the molecular chains of polymer materials break, leading to material embrittlement, surface cracking, and accelerated oxidation; the conjugated double bonds of organic dyes undergo photolytic breakage, causing the sheath to fade.

[0005] 2. Diurnal or seasonal temperature differences cause repeated thermal expansion and contraction of the sheath material, which can easily lead to stress cracking.

[0006] 3. During cable laying, the bending of the cable causes tensile deformation on the outer side of the sheath, resulting in stress concentration on the bent outer side. When the stress concentration point is subjected to the combined effects of various environmental factors, it is more prone to embrittlement, cracking and other damage.

[0007] Current testing methods for evaluating the weather resistance of cable outer sheaths mainly include laboratory accelerated aging simulation, natural exposure testing, and comprehensive performance evaluation. Specific methods are categorized as follows: 1. Artificial accelerated aging test: Using xenon lamps or ultraviolet lamps to simulate solar radiation, the performance degradation of the outer sheath material under long-term ultraviolet light is tested. The weather resistance of the cable outer sheath is evaluated by comparing the changes in tensile strength and elongation at break before and after the test; 2. Outdoor long-term exposure test: The outer sheath sample is placed in a real-world environment (such as coastal or industrial areas), and its surface aging phenomena (such as cracking and powdering) and mechanical property degradation are monitored periodically.

[0008] However, the existing testing methods described above have the following defects and shortcomings:

[0009] 1. Traditional accelerated aging tests typically ignore stress conditions and focus only on a single environmental factor. However, in real-world applications, materials are often under stress (such as the installation stress of cable sheaths), leading to discrepancies between laboratory data and actual aging behavior. Furthermore, due to differences in cable outer diameter and laying environment, the magnitude of stress on the cable varies. Current technology cannot account for the magnitude of stress experienced by the cable in the test, potentially underestimating the risk of material failure.

[0010] 2. Long-term outdoor exposure testing usually takes several years (e.g., 3-5 years) to obtain valid data, which is difficult to meet the needs of rapid research and development; natural environmental conditions (such as ultraviolet intensity, temperature and humidity fluctuations) cannot be precisely controlled, resulting in poor data repeatability and possible differences in results due to different years or geographical locations.

[0011] 3. Whether it is traditional accelerated aging test or long-term outdoor exposure test, the current evaluation method compares the tensile strength and elongation at break of the specimens before and after the test. More subtle changes (such as color changes or fine cracks) are not effectively detected.

[0012] Therefore, it is desirable in this field to develop a method for evaluating the weather resistance of cable materials under stress. Summary of the Invention

[0013] To address the shortcomings of existing technologies, the present invention aims to provide a method for evaluating the weather resistance performance of cable materials under stress, its application, and a fixture. The present invention stretches test pieces to different lengths based on the varying bending radii of different cables during actual installation, thus simulating performance degradation of the material under stress conditions, including under ultraviolet radiation and temperature and humidity changes.

[0014] To achieve this objective, the present invention adopts the following technical solution:

[0015] In a first aspect, the present invention provides a method for evaluating the weather resistance performance of cable materials under stress, the weather resistance evaluation method comprising the following steps:

[0016] (1) Confirm the cable outer diameter D, the cable minimum bending radius R, and the actual bending radius R0 of the cable outer sheath under the cable minimum bending radius. Calculate the elongation P of the cable outer sheath according to the following formula.

[0017]

[0018] (2) Make the outer sheath material to be tested into a dumbbell-shaped specimen, and mark two marking lines with a distance L between them on the middle test part of the dumbbell-shaped specimen;

[0019] (3) Place the dumbbell-shaped specimen in the fixture and stretch the dumbbell-shaped specimen to a stretching rate of P;

[0020] (4) Divide the dumbbell-shaped specimens in a stretched state into three groups along with the fixtures. Place one group in a dry, dark place and place the other two groups in an ultraviolet light weathering test chamber and conduct an artificial accelerated aging test on the dumbbell-shaped specimens.

[0021] (5) After time T1, take out a set of dumbbell-shaped test pieces placed in the UV weathering test chamber, and after time T2, take out another set of dumbbell-shaped test pieces placed in the UV weathering test chamber.

[0022] (6) The performance of the three groups of dumbbell-shaped test pieces was tested and the weather resistance of the cable material was evaluated.

[0023] The weather resistance evaluation method for cable materials provided by this invention takes the stress factors of the cable into account during the test. Combining the cable's outer diameter and the degree of bending during actual installation, the tensile length of the specimen is calculated using a formula to simulate the stress on the cable's outer sheath. Compared with traditional methods, the simulation conditions are more comprehensive, greatly reducing the risk of misjudging the material properties.

[0024] In the method for evaluating the weather resistance of cable materials under stress provided by the present invention, step (1) is to determine the elongation of the outer sheath of the cable material caused by cable bending under actual working conditions.

[0025] When actually installing and laying cables, the following conditions must be met: the bending radius of the cable after installation cannot be less than the cable's minimum bending radius. The cable bending radius is generally specified in product standards or provided by the cable manufacturer, typically 20 times, 15 times, or 10 times the cable's outer diameter, etc. Therefore, given the cable's outer diameter and minimum bending radius, the degree of stretching (i.e., elongation) of the outer sheath caused by bending after cable installation can be calculated using the aforementioned theoretical formula.

[0026] Preferably, step (2) of preparing the outer sheath material for the test into dumbbell-shaped test pieces specifically includes: preparing at least 15 (e.g., 15, 16, 17, 18, 19, 20, 21, etc.) dumbbell-shaped test pieces for each type of outer sheath material for the test. It should be noted that dumbbell-shaped test pieces can be prepared in accordance with GB / T2951.11.

[0027] Preferably, L in step (2) is 18 to 22 mm, such as 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, etc.

[0028] Preferably, step (4) involves dividing the dumbbell-shaped specimen in a stretched state, along with the clamps, into three groups, specifically including:

[0029] Divide the dumbbell-shaped test pieces in a stretched state into three groups along with the fixtures, and ensure that each group contains no fewer than 5 dumbbell-shaped test pieces (e.g., 5, 6, 7, etc.).

[0030] The time for placing the item in a dry, dark place in step (4) is 600 to 840 hours, for example, 600 hours, 624 hours, 648 hours, 672 hours, 696 hours, 720 hours, 744 hours, 768 hours, 792 hours, 816 hours, 840 hours, etc.

[0031] Preferably, the UV weathering test chamber described in step (4) is equipped with fluorescent UV lamps (selected as two sets of type 2 (UVB-313)). To better simulate the ultraviolet band of sunlight, the UV weathering test chamber (model ZN-P) is selected as the aging device for the evaluation method provided by this invention. Fluorescent UV lamps are artificial light sources that can simulate the ultraviolet band of sunlight, thereby verifying the environmental aging resistance of polymer materials.

[0032] Preferably, the accelerated aging test in step (4) includes two stages: illumination and condensation. The illumination stage is used to simulate daytime in the natural environment, and the light intensity can be controlled during illumination. The condensation stage is used to simulate the phenomenon of condensation on the sample surface at night. During the condensation stage, the fluorescent ultraviolet lamp is turned off (dark state), and only the test temperature and humidity are controlled.

[0033] Preferably, the illumination in step (4) is performed using a fluorescent ultraviolet lamp, wherein the wavelength of the fluorescent ultraviolet lamp is 250–350 nm (e.g., 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, etc.), and the intensity of the illumination is 0.5–1 W·m. -2 ·nm -1 (e.g., 0.5 W·m) -2 ·nm -1 0.6 W·m -2 ·nm -1 0.7 W·m -2 ·nm -1 0.76 W·m -2 ·nm -1 0.8 W·m -2 ·nm -1 0.9 W·m -2 ·nm -1 1W·m -2 ·nm -1 (etc.), the test temperature during illumination is 70℃±3℃, for example 67℃, 68℃, 69℃, 70℃, 71℃, 72℃, 73℃, etc.

[0034] Preferably, the test temperature during condensation is 50℃±3℃, such as 47℃, 48℃, 49℃, 50℃, 51℃, 52℃, 53℃, etc.

[0035] Preferably, the artificial accelerated aging test of the dumbbell-shaped test piece in step (4) specifically includes: irradiating the dumbbell-shaped test piece with light for 8 hours, then condensing it for 4 hours, and repeating this cycle every 12 hours until the dumbbell-shaped test piece is removed from the UV weathering test chamber.

[0036] Preferably, the T1 time in step (5) is 240 to 360 hours, such as 240 hours, 252 hours, 264 hours, 276 hours, 288 hours, 300 hours, 312 hours, 324 hours, 336 hours, 348 hours, 360 hours, etc.

[0037] Preferably, the T2 time in step (5) is 600 to 840 hours, such as 600 hours, 624 hours, 648 hours, 672 hours, 696 hours, 720 hours, 744 hours, 768 hours, 792 hours, 816 hours, 840 hours, etc.

[0038] Preferably, the performance test in step (6) includes: visually observing the appearance of the dumbbell-shaped test piece, observing the appearance of the dumbbell-shaped test piece using a microscope, and performing mechanical property testing on the dumbbell-shaped test piece.

[0039] Specifically, the visual inspection of the dumbbell-shaped test piece includes: visually inspecting the appearance of the test piece for defects such as cracks and fading. If defects such as cracks and fading are present, the test piece is deemed unqualified.

[0040] The observation of the appearance of the dumbbell-shaped test piece using a microscope includes: inspecting the sample with a microscope of at least 50x magnification to observe whether there are any abnormal cracks. If there are abnormal cracks, the sample is deemed unqualified.

[0041] Preferably, the mechanical property testing includes the testing of tensile strength and elongation at break. It is required that the rate of change of tensile strength and elongation at break of the specimen after 300 hours be ≤ ±15%; and the rate of change of tensile strength and elongation at break of the specimen after 720 hours be ≤ ±20%.

[0042] Secondly, the present invention provides an application of the weather resistance evaluation method as described in the first aspect in testing the weather resistance of cable sheath materials.

[0043] Thirdly, the present invention provides a clamp for clamping and stretching the dumbbell-shaped specimen described in step (3) of the first aspect.

[0044] In existing testing methods, dumbbell-shaped specimens made of sheathing material are placed in an artificial accelerated aging chamber in a non-stretched state. To ensure the dumbbell-shaped specimens are placed under tension before entering the aging chamber, this invention designs a clamp that can be placed in the artificial accelerated aging chamber (i.e., the aforementioned UV weathering test chamber) and can stretch the dumbbell-shaped specimens to a specific length, thereby placing the specimens under stress before entering the aging chamber.

[0045] Preferably, the clamp includes:

[0046] Fixture base;

[0047] Protective plates are installed on both sides of the fixture base;

[0048] A rectangular clamping block with a threaded hole in the middle is welded to the fixture base at the bottom.

[0049] The "L"-shaped clamping block has a threaded hole in the middle.

[0050] Screws, in conjunction with rectangular clamps and "L"-shaped clamps, can tighten dumbbell-shaped test pieces;

[0051] The threaded rod is welded to the "L"-shaped clamping block;

[0052] The threaded knob can rotate on the threaded rod and generate displacement, thereby moving the "L"-shaped clamping block.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] (1) This invention incorporates the stress factors of the cable into the experiment, and calculates the tensile length of the specimen using a formula based on the cable's outer diameter and the degree of bending during actual installation to simulate the stress on the cable's outer sheath. Simulations also consider conditions such as day-night cycles and temperature changes. Compared to traditional methods, the simulation conditions are more comprehensive, greatly reducing the risk of misjudging the material properties.

[0055] (2) The present invention has a short testing time, and effective data can be obtained in 30 days, which can meet the needs of rapid research and development. Compared with traditional methods, natural environmental conditions (such as ultraviolet intensity, temperature and humidity fluctuations) can be precisely controlled, the data repeatability is high, and the results will not be affected by different years or geographical locations.

[0056] (3) The present invention provides a more detailed and specific evaluation of the weather resistance of cable materials. Compared with traditional methods, it can not only compare the tensile strength and elongation at break of the samples before and after the test, but also effectively detect subtle changes such as color changes and fine cracks. Attached Figure Description

[0057] Figure 1This is a schematic diagram of the cable structure when bent, as provided in Example 1.

[0058] Figure 2 This is a schematic diagram of the structure of the dumbbell-shaped specimen provided in Example 1;

[0059] Figure 3 This is a top view of the structural schematic diagram of the dumbbell-shaped specimen held by the clamp in Example 1;

[0060] Figure 4 This is a side view of the structural schematic diagram of the dumbbell-shaped specimen held by a clamp in Example 1;

[0061] Figure 5 This is a schematic diagram of the structure of the UV weathering test chamber used in Example 1;

[0062] Figure 6 A flowchart of the method for evaluating the weather resistance performance of cable materials under stress state provided in Example 1;

[0063] Figure 7A , Figure 7B , Figure 7C The images show the original appearance of Material 1 under a microscope, and its appearance under a microscope after being placed in an ultraviolet light weathering chamber for 300 hours and 720 hours, respectively.

[0064] Figure 8A , Figure 8B , Figure 8C The images show the original appearance of Material 2 under a microscope, and its appearance under a microscope after being placed in an ultraviolet light weathering chamber for 300 hours and 720 hours, respectively.

[0065] Among them, 1-clamp base, 2-rectangular clamping block, 3-"L" shaped clamping block, 4-4mm outer diameter screw, 5-4mm outer diameter threaded rod, 6-4mm inner diameter threaded knob, 7-dumbbell-shaped test piece, 8-two sets of type 2 (UVB-313) fluorescent ultraviolet lamps, 9-control panel. Detailed Implementation

[0066] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0067] Example 1

[0068] This embodiment provides a method for evaluating the weather resistance performance of cable materials under stress. Taking YJY33-0.6 / 1kV 4*50 as an example, the cable outer diameter is 37.0mm, and the minimum allowable bending radius is 370mm. Two materials are used as the outer sheath materials for YJY33-0.6 / 1kV 4*50: Material 1 (no customer feedback on cracking) and Material 2 (customer feedback on cracking). The weather resistance performance evaluation described in this embodiment is performed on these two materials.

[0069] The weather resistance evaluation method includes the following steps:

[0070] (1) Based on the cable outer diameter D, the cable's minimum allowable bending radius R, and the actual bending radius R0 of the cable's outer sheath at the minimum allowable bending radius, calculate the length ratio (i.e., elongation ratio) of the sheath when the cable is installed at its minimum allowable bending radius. The structural diagram of the cable during bending is shown below. Figure 1 As shown, the elongation P is calculated as follows:

[0071]

[0072] Calculations show that the tensile strength of YJY33-0.6 / 1kV 4*50 is (370+37 / 2) / 370=1.05.

[0073] (2) Referring to GB / T2951.11, the outer sheath material to be tested is prepared into dumbbell-shaped test pieces after open milling, pressing, and slicing. Two marking lines 20 mm apart are marked on the middle test part of the dumbbell-shaped test piece. The structural schematic diagram of the dumbbell-shaped test piece is shown below. Figure 2 As shown, 15 dumbbell-shaped test pieces are required for each test material. Five dumbbell-shaped test pieces are retained as original samples, and the other 10 dumbbell-shaped test pieces are used for ultraviolet light weathering performance testing.

[0074] (3) Place the dumbbell-shaped specimen in the fixture and clamp it in parallel.

[0075] The top and side views of the structural diagram of the clamp holding the dumbbell-shaped specimen are shown below. Figure 3 and Figure 4 As shown, it includes:

[0076] The clamp base 1 is 300mm long and 150mm wide, with side guard plates 20mm high.

[0077] Rectangular clamping block 2, 30mm long, 15mm wide, 4mm high, with a 4mm threaded hole in the middle, and welded to the clamping base at the bottom;

[0078] The "L" shaped clamping block 3 is 35mm long, 15mm wide, and 18mm high, with a 4mm threaded hole in the middle.

[0079] Four screws with an outer diameter of 4mm and a length of 12mm can be used with rectangular clamps and "L" shaped clamps to tighten dumbbell-shaped test pieces.

[0080] 5 threaded rods with an outer diameter of 4mm are welded onto an "L"-shaped clamping block;

[0081] The 4mm inner diameter threaded knob 6 can rotate on the threaded rod and generate displacement, thereby moving the "L" shaped clamping block.

[0082] The dumbbell-shaped test piece 7 is held by the rectangular clamp 2 and the "L"-shaped clamp 3.

[0083] Based on the bending radius of the cable, the elongation rate P of the dumbbell-shaped test piece can be calculated. The length L1 of the dumbbell-shaped test piece after stretching can be calculated as 20mm × 1.05 = 21mm. By using the number 6 knob and the marking line on the dumbbell-shaped test piece, the length of the dumbbell-shaped test piece can be stretched to 21mm.

[0084] (4) Three sets of fixtures are required for each material. After the sample is installed, one set of fixtures should be stored in the dark for 720 hours. The other two sets of fixtures should be installed in the UV weathering test chamber (model ZN-P). The dumbbell-shaped specimen should be in a stretched state in the fixture. The structural diagram of the UV weathering test chamber is shown below. Figure 5 As shown.

[0085] Irradiation was performed using two sets of Type 2 (UVB-313) fluorescent ultraviolet lamps (8), with a wavelength of 310 nm and an irradiation intensity of 0.76 W·m. -2 ·nm -1 The test chamber control panel 9 allows adjustment of test parameters such as temperature, irradiation time, and condensation time. In the test method described in this embodiment, the test chamber needs to maintain an 8-hour drying time at a test temperature of 70℃±3℃, while continuously irradiating light. After the drying time, a 4-hour condensation time is maintained at a test temperature of 50℃±3℃, without irradiation. This process is repeated every 12 hours, for a total of 720 hours.

[0086] (5) Five dumbbell-shaped specimens were taken out for each material at 300 hours and 720 hours, and the surface of the specimens was gently wiped clean with soft cotton paper soaked in distilled water. The original specimens, 300-hour specimens, and 720-hour specimens were inspected in the following order:

[0087] ① Visually inspect the sample for defects such as cracks and fading;

[0088] ② Use a 50x microscope to examine the sample and observe whether any abnormal cracks appear;

[0089] ③ Perform tensile strength and elongation at break tests on all specimens and record the data.

[0090] The flowchart of the method for evaluating the weather resistance performance of cable materials under stress state provided in this embodiment is as follows: Figure 6 As shown.

[0091] Comparative Example 1

[0092] Existing materials 1 and 2 from Example 1 were commissioned to an external testing agency to conduct artificial climate aging tests in accordance with Appendix C of GB / T14049, as a comparison of the test methods.

[0093] The experimental data for Example 1 and Comparative Example 1 are shown in Table 1.

[0094] Table 1

[0095]

[0096] As shown in Table 1, both Materials 1 and 2 passed the artificial climate aging test conducted by an external testing agency according to Appendix C of GB / T14049. However, the cable produced by Material 2 clearly cracked after being bent and installed at the customer's site, indicating that this test method is insufficient for detecting the weather resistance of materials under stress.

[0097] Using the weathering performance test method provided in Example 1, Material 1 and Material 2 showed significant differences in their post-test data. After 300 hours and 720 hours, the mechanical properties of the materials decreased significantly. Simultaneously, the original appearance of Material 1 and Material 2, as well as their appearance after 300 hours and 720 hours in the UV weathering chamber, were observed under a microscope. The original appearance of Material 1 under the microscope, and its appearance after 300 hours and 720 hours in the UV weathering chamber, are shown below. Figure 7A , Figure 7B , Figure 7C As shown, the original appearance of Material 2 under a microscope, and its appearance under a microscope after being placed in an ultraviolet weathering chamber for 300 hours and 720 hours are respectively as follows. Figure 8A , Figure 8B , Figure 8C As shown.

[0098] It can be seen that material 2 showed slight cracking after 300 hours. Figure 8B After 720 hours, obvious cracks appeared. Figure 8CMaterial 1 showed no significant difference in mechanical properties or microscopic appearance after 300 hours and 720 hours.

[0099] Using the weathering performance test method provided in Example 1, the results of the tests on Material 1 (where no customer reported cracking) and Material 2 (where customer reported cracking) were consistent with the actual situation, indicating that the evaluation method provided by this invention is scientific and effective. It can be used to predict the weathering performance of cables of different models and specifications under bending conditions, increase the accuracy of material evaluation, and shorten the test time.

[0100] The applicant declares that this invention illustrates the method for evaluating the weather resistance performance of cable materials under stress, its application, and the fixture through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials used, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A method for evaluating the weather resistance performance of cable materials under stress, characterized in that, The weather resistance evaluation method includes the following steps: (1) Confirm the cable outer diameter D, the cable minimum bending radius R, and the actual bending radius R0 of the cable outer sheath under the cable minimum bending radius. Calculate the elongation P of the cable outer sheath according to the following formula. (2) Make the outer sheath material to be tested into a dumbbell-shaped specimen, and mark two marking lines with a distance L between them on the middle test part of the dumbbell-shaped specimen; (3) Place the dumbbell-shaped specimen in the fixture and stretch the dumbbell-shaped specimen to a stretching rate of P; (4) Divide the dumbbell-shaped specimens in a stretched state into three groups along with the fixtures. Place one group in a dry, dark place and place the other two groups in an ultraviolet light weathering test chamber and conduct an artificial accelerated aging test on the dumbbell-shaped specimens. (5) After time T1, take out a set of dumbbell-shaped test pieces placed in the UV weathering test chamber, and after time T2, take out another set of dumbbell-shaped test pieces placed in the UV weathering test chamber. (6) The performance of the three groups of dumbbell-shaped test pieces was tested and the weather resistance of the cable material was evaluated.

2. The weather resistance performance evaluation method according to claim 1, characterized in that, Step (2) involves making dumbbell-shaped test pieces from the outer sheath material to be tested, specifically including making at least 15 dumbbell-shaped test pieces from each type of outer sheath material to be tested.

3. The weather resistance performance evaluation method according to claim 1 or 2, characterized in that, In step (2), L is 18-22 mm.

4. The weather resistance evaluation method according to any one of claims 1-3, characterized in that, Step (4) involves dividing the dumbbell-shaped specimen in a stretched state, along with the clamps, into three groups, specifically including: The dumbbell-shaped specimens in a stretched state, along with the fixtures, are divided into three groups, with each group containing no fewer than five dumbbell-shaped specimens.

5. The weathering resistance evaluation method according to any one of claims 1-4, characterized in that, The time for placing the item in a dry, dark place as described in step (4) is 600–840 hours; Preferably, the ultraviolet weathering test chamber described in step (4) is equipped with a fluorescent ultraviolet lamp; Preferably, the accelerated aging test in step (4) includes two stages: light exposure and condensation. Preferably, the illumination is provided by a fluorescent ultraviolet lamp, wherein the wavelength of the fluorescent ultraviolet lamp is 250–350 nm and the intensity of the illumination is 0.5–1 W·m. -2 ·nm -1 The test temperature under light exposure is 70℃±3℃; Preferably, the test temperature during condensation is 50℃±3℃.

6. The weathering resistance evaluation method according to any one of claims 1-5, characterized in that, Step (4) describes the artificial accelerated aging test of the dumbbell-shaped test piece, which specifically includes: irradiating the dumbbell-shaped test piece with light for 8 hours, then condensing it for 4 hours, and repeating this cycle every 12 hours until the dumbbell-shaped test piece is removed from the UV weathering test chamber.

7. The weather resistance evaluation method according to any one of claims 1-6, characterized in that, The T1 time mentioned in step (5) is 240 to 360 hours; Preferably, the T2 time in step (5) is 600 to 840 hours.

8. The weather resistance evaluation method according to any one of claims 1-7, characterized in that, The performance test described in step (6) includes: visually observing the appearance of the dumbbell-shaped test piece, observing the appearance of the dumbbell-shaped test piece using a microscope, and performing mechanical property testing on the dumbbell-shaped test piece; Preferably, the mechanical property testing includes the testing of tensile strength and elongation at break.

9. The application of the weathering performance evaluation method as described in any one of claims 1-8 in testing the weathering performance of cable sheath materials.

10. A clamp, characterized in that, The clamp is used to hold and stretch the dumbbell-shaped test piece described in step (3) of claim 1; Preferably, the clamp includes: Fixture base; Protective plates are installed on both sides of the fixture base; A rectangular clamping block with a threaded hole in the middle is welded to the fixture base at the bottom. The "L" shaped clamping block has a threaded hole in the middle; Screws, in conjunction with rectangular clamps and "L"-shaped clamps, can tighten dumbbell-shaped test pieces; The threaded rod is welded to the "L"-shaped clamping block; The threaded knob can rotate on the threaded rod and generate displacement, thereby moving the "L"-shaped clamping block.

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