Method and apparatus for residual stress relief of epoxy composite insulation

Abstract

This invention discloses a method and apparatus for residual stress release in epoxy composite insulation components. The method involves preparing an epoxy sample with bidirectional strain gauges, subjecting it to multi-stage thermal cycling treatment, recording strain data to determine the optimal combination of treatment parameters (temperature, holding time, cooling rate, and number of cycles), and then applying this optimal parameter combination to the epoxy composite insulation component for stress reduction. The apparatus includes a programmable oven, a strain gauge, and a host computer. This invention is simple to operate, low in cost, and through multi-scale collaborative optimization, can significantly reduce the residual stress in currently commercially available epoxy composite insulation components, significantly improving the reliability of epoxy composite insulation components used in ultra-high voltage / extra-high voltage power equipment, and has broad engineering application prospects.

Description

Technical Field

[0001] This invention relates to the field of power transmission and transformation insulation equipment manufacturing, and more specifically, to a method and apparatus for releasing residual stress in epoxy composite insulation components. Background Technology

[0002] In power systems, GIL / GIS equipment is widely used due to its compact structure and high reliability. Epoxy resin insulation components, as key parts, perform the dual functions of electrical insulation and mechanical support. However, with the increase in voltage levels and the scaling up of equipment, the size of epoxy insulation components is constantly increasing, and the problem of internal residual stress is becoming increasingly prominent.

[0003] Currently, epoxy composite insulation components are mainly cast from epoxy resin and inorganic fillers such as alumina in a certain doping ratio. These components inevitably contain residual stress before being put into operation, primarily due to the casting and curing process during manufacturing. In existing technologies, uneven heat dissipation or improper temperature control during the production of epoxy composite insulation components can easily lead to residual stress. During long-term operation, epoxy composite insulation components continuously face complex conditions such as strong electric fields, high air pressure, mechanical stress, and uneven temperature distribution. The presence of residual stress under these complex conditions significantly increases the risk of insulation breakdown and mechanical failure, leading to frequent bursting and breakdown failures, seriously threatening the safe and stable operation of the power system. Currently, manufacturers have not implemented relevant factory inspection standards, which greatly restricts the operational reliability of epoxy composite insulation components.

[0004] Therefore, given the residual stress present in epoxy composite insulation components after casting, there is an urgent need for a practical and effective method to reduce this residual stress, improve the manufacturing level of high-voltage electrical equipment, thereby reducing the accident rate of epoxy composite insulation components and improving the reliability of power system operation. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies and address issues such as performance degradation and increased breakdown risk caused by residual stress in insulation components, this invention proposes a method and apparatus for releasing residual stress in epoxy composite insulation components. Through multi-scale collaborative optimization combined with thermal aging treatment, a "unit-to-whole" stress transfer relationship is established by simulating large-size insulation components with small-size samples. The optimal combination of four-dimensional parameters, including temperature, time, rate, and number of cycles, is determined. Finally, this process is applied to the actual treatment of insulation components, which can significantly reduce the residual stress in epoxy composite insulation components and improve their mechanical strength and electrical insulation performance.

[0006] The objective of this invention can be achieved through the following technical solutions.

[0007] A method for relieving residual stress in epoxy composite insulation components includes the following steps:

[0008] S1 Prepares epoxy specimens with bidirectional strain gauges;

[0009] S2 performs multi-stage thermal cycling treatment on epoxy samples. Each cycle includes heating, isothermal and cooling stages. The strain data of biaxial strain gauges are monitored and recorded in real time during each cycle. The optimal combination of treatment parameters to reduce the residual stress of epoxy composite materials is determined based on the strain data of biaxial strain gauges during each cycle.

[0010] S3 employs the optimal combination of processing parameters and follows the same multi-stage thermal cycling process as step S2 to perform stress reduction treatment on the epoxy composite insulation component; wherein, the epoxy composite insulation component and the epoxy sample are made of epoxy composite material with the same mass ratio.

[0011] Further, the preparation process of the epoxy sample in step S1 is as follows: the epoxy composite material for preparing the epoxy composite insulation part is mixed in a specific ratio, heated to a molten state, degassed under vacuum and poured into a mold, cured and demolded to obtain the epoxy sample corresponding to the epoxy composite insulation part; wherein, a bidirectional strain gauge is suspended at the center of the mold.

[0012] Furthermore, the specific preparation process of the epoxy sample described in step S1 is as follows:

[0013] S1.1 Pour the molten epoxy composite material into a mold with bidirectional strain gauges and begin curing;

[0014] The epoxy composite material for preparing epoxy composite insulation parts is mixed in a specific ratio, heated to a molten state, and degassed under vacuum. At the same time, a bidirectional strain gauge is suspended at the center of the mold. The mold is placed in a programmable oven. After preheating the mold with the bidirectional strain gauge, the molten epoxy composite material after vacuum degassed is poured into the mold. The leads of the bidirectional strain gauge are connected to the strain gauge. The value measured by the strain gauge is transmitted to the host computer. The door of the programmable oven is closed, and curing begins.

[0015] S1.2 Reset and record the bidirectional strain gauge values ​​during the curing process. Stop recording after curing is complete and the temperature drops to room temperature. Remove the epoxy sample from the mold.

[0016] After setting the curing program in the programmable oven 1, the strain gauge values ​​are simultaneously cleared and reset on the host computer. The values ​​of the bidirectional strain gauge change over time during the curing process are recorded until the curing is complete and the temperature drops to room temperature. The data acquisition is then stopped. The epoxy sample is then demolded from the mold. After demolding, the epoxy sample is free from fixed constraints, which eliminates the interference of fixed constraints on the bidirectional strain gauge data acquisition.

[0017] Furthermore, the bidirectional strain gauge described in step S1 consists of two strain gauges that are perpendicular to each other and have the same length.

[0018] Furthermore, the multi-stage thermal cycling process in step S2 includes:

[0019] Heating stage: The epoxy sample is heated from room temperature to the set temperature T at a constant rate;

[0020] Isothermal stage: The epoxy sample after heating treatment is held at a set temperature T for a set time t;

[0021] Cooling stage: The epoxy sample after isothermal treatment is cooled to room temperature at a set cooling rate v;

[0022] After completing one cycle of the above heating, constant temperature, and cooling stages, the cycle is repeated n times.

[0023] Furthermore, in step S2, the epoxy sample undergoes a multi-stage thermal cycling treatment. Each cycle includes heating, isothermal, and cooling stages. The strain data of the biaxial strain gauges are monitored and recorded in real time during each cycle. Based on the strain data of the biaxial strain gauges during each cycle, the optimal combination of treatment parameters for reducing the residual stress of the epoxy composite material is determined. The specific process is as follows:

[0024] S2.1 Reset the biaxial strain gauge at room temperature and start recording values. Use a programmable oven to heat the epoxy sample to the set temperature T.

[0025] S2.2 After heating the epoxy sample to the set temperature T, it is kept at a constant temperature for the set holding time t.

[0026] After the S2.3 isothermal treatment is completed, the epoxy sample is cooled to room temperature at the set cooling rate v.

[0027] After the S2.4 epoxy sample cools to room temperature, the programmable oven stops working, the bidirectional strain gauge recording ends, and one heating process is completed.

[0028] S2.5 Calculate the strain difference value of the biaxial strain gauge in this heating process and determine whether the strain difference value reaches the strain tolerance range. If yes, then the temperature T, holding time t, cooling rate v, and number of cycles n corresponding to this cycle are taken as the optimal processing parameter combination. If no, then adjust the temperature T, holding time t, cooling rate v, and number of cycles n, and repeat the above steps S2.1 to S2.5. In addition, if the number of heating process cycles n has reached the set maximum value but the strain difference value still does not meet the strain tolerance range requirement, then take the temperature T, holding time t, cooling rate v, and number of cycles n corresponding to the minimum strain difference value as the optimal processing parameter combination.

[0029] Furthermore, the epoxy composite insulation component is an insulator for power equipment, including but not limited to three-post insulators, basin insulators, or cylindrical insulators.

[0030] The objective of this invention can also be achieved through the following technical solutions.

[0031] A residual stress relief device for epoxy composite insulation includes a programmable oven, a strain gauge, and a host computer. The programmable oven is used to set and adjust the temperature T, holding time t, cooling rate v, and number of cycles n, and to perform multi-stage thermal cycling treatment on an epoxy sample with a built-in bidirectional strain gauge according to the above-set parameters. The strain gauge is connected to the leads of the bidirectional strain gauge and is used to upload the measured values ​​of each stage to the host computer in real time. The host computer is used to record the strain values ​​of the bidirectional strain gauge over time in each stage in real time, and to determine the optimal combination of processing parameters based on the strain data of the bidirectional strain gauge in each heating cycle.

[0032] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0033] (1) In this invention, epoxy composite material samples are prepared by mixing epoxy composite materials with the same epoxy composite insulation components in a specific ratio, and bidirectional strain gauges are embedded during the curing process to monitor the changes in transverse and longitudinal strains in real time. Through strain data recording and analysis, the optimal combination of treatment parameters for reducing the residual stress of epoxy composite materials is determined, namely temperature (T), heat preservation time (t), cooling rate (v) and number of cycles (n).

[0034] (2) This invention involves multi-cycle thermal aging treatment of cured epoxy samples, including three stages: heating, holding, and cooling. Optimal process parameters are explored by adjusting the temperature (T), holding time (t), cooling rate (v), and number of cycles (n). A difference in bidirectional strain gauge values ​​≤1% is used as the criterion for negligible residual stress, where strain is mainly caused by thermal expansion and contraction, and the stress contribution is lower than the engineering error range. Balancing process economy with stress relief effect, a maximum number of cycles is set. During the treatment, the epoxy composite insulation component remains in a free state to avoid mechanical constraints introducing additional stress, ensuring consistency with the experimental conditions of the epoxy sample.

[0035] (3) This invention directly applies the optimized thermal aging process to actual epoxy composite insulation components (such as three-post insulators) to effectively reduce residual stress. Experimental results show that this method can reduce the maximum residual stress by about 50%, and the stress distribution is more uniform, significantly improving the long-term operational reliability of the insulation components.

[0036] (4) The residual stress release method for epoxy composite insulation components proposed in this invention is scientifically sound. It uses bidirectional strain gauges to monitor stress changes in real time and combines this with quantitative analysis based on the generalized Hooke's law to ensure precise optimization of process parameters. It has wide applicability, suitable for epoxy composite insulation components of different shapes and sizes, and is particularly suitable for key insulation components in ultra-high voltage / extra-high voltage power equipment. The process is simple, cost-controllable, and easy to promote and apply in existing production lines, resulting in significant economic and social benefits. This invention provides an efficient and reliable solution for residual stress control in epoxy composite insulation components, which is of great significance for improving the operational safety of power equipment. Attached Figure Description

[0037] Figure 1 This is a flowchart of the residual stress relief method for the epoxy composite insulation component of the present invention;

[0038] Figure 2 This is a schematic diagram of the residual stress relief device for the epoxy composite insulation component of the present invention;

[0039] Figure 3 These are the strain values ​​of the biaxial strain gauges of the epoxy sample in this invention under different cycles.

[0040] Figure 4 This is a comparison diagram of the residual stress on the front side of the epoxy composite insulation component before and after treatment, as exemplified by this invention.

[0041] Figure 5 This is a comparison diagram of the residual stress on the back side of the epoxy composite insulation component before and after treatment, as exemplified by this invention.

[0042] Figure reference numerals: 1-Programmable oven; 2-Epoxy sample; 3-Bidirectional strain gauge;

[0043] 4-Strain gauge; 5-Host computer; 6-Epoxy composite insulation component. Detailed Implementation

[0044] The present invention will now be further described with reference to the accompanying drawings.

[0045] This invention proposes a method for releasing residual stress in epoxy composite insulation components. First, an epoxy sample 2 with a bidirectional strain gauge 3 is prepared. Since the epoxy sample 2 is smaller in size than the epoxy composite insulation component 6 made of the same material, the unconstrained epoxy sample 2 can be considered as a structural unit of the epoxy composite insulation component 6. By subjecting the epoxy sample 2 to multi-stage thermal cycling treatment, the optimal parameter combination for reducing the residual stress of the epoxy composite material is analyzed and obtained. Finally, the unconstrained epoxy composite insulation component 6 is treated to achieve the goal of reducing the residual stress of the epoxy composite insulation component 6. The specific implementation process is as follows:

[0046] S1: Prepare epoxy specimens with bidirectional strain gauges.

[0047] The epoxy composite material for preparing the epoxy composite insulation component is mixed in a specific ratio, heated to a molten state, degassed under vacuum, poured into a mold, cured, and demolded to obtain the epoxy sample corresponding to the epoxy composite insulation component; a bidirectional strain gauge is suspended at the center of the mold. The specific steps include:

[0048] S1.1 Pour the molten epoxy composite material into a mold with bidirectional strain gauges and begin curing.

[0049] In this step, the epoxy composite material for preparing the epoxy composite insulation is mixed in a specific ratio, heated to a molten state, and then degassed under vacuum. For example, epoxy composites used in engineering are generally made of epoxy resin / alumina. In this example, the epoxy composite material is made by mixing epoxy resin (CT-5531) / alumina (particle size 10 micrometers) / curing agent (HY-5533-1) in a mass ratio of 100:320:38. The composite material is heated to 130°C to a molten state, thoroughly stirred and mixed, and then degassed under vacuum.

[0050] In this step, the bidirectional strain gauge 3 is placed at the center of the mold by suspension. The bidirectional strain gauge consists of two strain gauges, which are perpendicular to each other and of equal length. The strain gauge parallel to the bottom surface of the mold is in the horizontal direction, and the strain gauge perpendicular to the bottom surface of the mold is in the vertical direction. The sensitive grid of the bidirectional strain gauge 3 (one sensitive grid corresponds to two leads) can be 2 mm long. For example, the mold is a cylindrical vessel with a diameter of 2.5 cm and a height of 3 cm.

[0051] In this step, to ensure the curing temperature of the mold with the bidirectional strain gauge 3 is consistent with that of the epoxy composite material before curing, the mold is placed in a programmable oven 1 (temperature control accuracy can be ±1℃). The mold with the bidirectional strain gauge is preheated to 130℃. Then, the degassed molten epoxy composite material is poured into the mold. The leads of the bidirectional strain gauge 3 are connected to the strain gauge 4. The values ​​measured by the strain gauge 4 are transmitted to the host computer 5 in real time. The door of the programmable oven 1 is closed, and curing begins. For example, the curing temperature is set to 130℃ (130℃ throughout the curing process), and the curing time is set to 10.5 hours.

[0052] S1.2 Reset and record the bidirectional strain gauge values ​​during the curing process. Stop recording after curing is complete and the temperature drops to room temperature. Remove the epoxy sample from the mold.

[0053] In this step, after setting the curing program in the programmable oven 1, the strain gauge values ​​are cleared and reset on the host computer 5. The strain values ​​of the bidirectional strain gauge 3 as a function of time during the curing process are collected and recorded (i.e., real-time monitoring of transverse and longitudinal strain changes). The recording sampling frequency can be set to collect once every 1 minute until the curing is completed and the temperature drops to room temperature, at which point the collection stops. The epoxy sample 2 is then demolded from the mold. After demolding, the epoxy sample 2 is free from fixed constraints, which eliminates the interference of fixed constraints on the collected values ​​of the bidirectional strain gauge 3.

[0054] S2: The epoxy samples undergo multi-stage thermal cycling treatment, with each cycle including three stages: heating, isothermal treatment, and cooling. The strain data from biaxial strain gauges are monitored and recorded in real time during each cycle. Based on the strain data from the biaxial strain gauges during each cycle, the optimal combination of treatment parameters for reducing residual stress in the epoxy composite material is determined. Specific process:

[0055] S2.1 Heating Stage: Reset the biaxial strain gauge 3 at room temperature and start recording values. Heat the epoxy sample from room temperature to the set temperature T at a constant rate.

[0056] In this step, the epoxy sample 2 is placed in a programmable oven 1 at room temperature. A bidirectional strain gauge 3 is connected to a strain meter 4, and the strain meter 4 is connected to a host computer 5. The strain gauge values ​​are zeroed and reset on the host computer 5. The temperature T is set in the programmable oven 1, and the time required to heat from room temperature to temperature T can be set to 30 minutes. For example, if the glass transition temperature of the epoxy composite material used in this invention is 117°C, the heating temperature T can be set to 55°C (low temperature range), 85°C (medium-low temperature range), 115°C (close to the glass transition temperature), 145°C (above the glass transition temperature), or 175°C (high temperature range), etc., covering the actual operating temperature range and heat treatment sensitive area of ​​the epoxy composite insulation component.

[0057] S2.2 Constant Temperature Stage: After the epoxy sample is heated to the set temperature T, it is kept at a constant temperature for the set holding time t.

[0058] In this step, after setting the heating temperature T, the holding time t of the heating temperature is set in the programmable oven 1. The epoxy sample 2 is held at temperature T for a holding time t. More specifically, the holding time t is set according to the time and economic requirements in actual engineering applications, such as 4h or 8h, to balance engineering efficiency and stress relaxation.

[0059] S2.3 Cooling Stage: After the isothermal treatment is completed, the epoxy sample is cooled to room temperature at the set cooling rate v.

[0060] In this step, after setting the heat preservation time t, the cooling rate v of the epoxy sample 2 after heat preservation is set in the programmable oven 1. The epoxy sample is cooled to room temperature according to the set cooling rate v. More specifically, in combination with engineering practice, the cooling rate v is set to 10℃ / h or 3℃ / h, etc.

[0061] After the S2.4 epoxy sample cools to room temperature, the programmable oven stops working, the bidirectional strain gauge 3 stops recording values, and the heating process is completed.

[0062] In this step, the trigger condition for the programmable oven 1 to stop working is set to the epoxy sample 2 cooling to room temperature. After the programmable oven 1 stops heating, the recording and export of the bidirectional strain gauge 3 values ​​are terminated on the host computer 5. One heating process cycle consists of steps S2.1 to S2.4.

[0063] S2.5 Calculate the strain difference value of the biaxial strain gauge in this heating process and determine whether the strain difference value reaches the strain tolerance range. If yes, then the temperature T, holding time t, cooling rate v, and number of cycles n corresponding to this cycle are taken as the optimal processing parameter combination. If no, then adjust the temperature T, holding time t, cooling rate v, and number of cycles n, and repeat the above steps S2.1 to S2.5. In addition, if the number of heating process cycles n has reached the set maximum value but the strain difference value still does not meet the strain tolerance range requirement, then take the temperature T, holding time t, cooling rate v, and number of cycles n corresponding to the minimum strain difference value as the optimal processing parameter combination.

[0064] In this step, the strain difference of the bidirectional strain gauge 3 in each cycle is calculated, that is, the difference in strain data between the transverse and longitudinal strain gauges in the same heating cycle. Based on the strain difference, it is determined whether each parameter (T, t, v, n) has reached the optimal solution. According to the generalized Hooke's law, for linear elastic and isotropic materials, the relationship between stress (σ) and strain (σ) is as follows:

[0065]

[0066] In the formula, E is the elastic modulus, v is Poisson's ratio, ∈ 11 ,∈ 22 ,∈ 11 These represent the strains in the three orthogonal directions of the stress field, σ. 11 σ 22 σ 33These represent the stresses in three orthogonal directions within the stress field. If the strain in a certain direction is forcibly constrained, i.e., when the epoxy sample 2 or the epoxy composite insulation component 6 is constrained, stress will be generated in that direction through the Poisson effect (even without direct loading). For the demolded epoxy sample 2, the direction of the bidirectional strain gauge 3 can be considered orthogonal and perpendicular in any direction. Therefore, when the strain difference of the unconstrained epoxy sample 2 reaches the tolerance range, it indicates that the contribution of stress to strain is small, and the strain mainly comes from the thermal expansion and contraction of the epoxy composite material. More specifically, for example, the strain tolerance can be specified as 1%. In addition, considering the practical engineering requirements for time and economy, a maximum value for the number of heating process cycles needs to be set, for example, a maximum value of 6 cycles. If the strain difference is ≤1%, it is determined that the optimal treatment effect has been achieved, and the T, t, v, and n corresponding to this cycle are taken as the optimal treatment parameter combination; if the number of heating process cycles n has reached the set maximum value but the strain difference still does not meet the strain tolerance range requirement, then the temperature T, holding time t, cooling rate v, and number of cycles n corresponding to the minimum strain difference are taken as the optimal treatment parameter combination. Figure 3 The difference between the biaxial strain gauge 3 and the epoxy sample 2 under different cycles in this embodiment of the invention can be seen. It can be seen that the difference between the biaxial strain gauges is smaller in the third cycle than in the second cycle. In particular, the strain curves in the latter part almost overlap, indicating that the strain is mainly caused by the thermal expansion and contraction of the epoxy sample 2, while the residual stress is small. At this time, the number of cycles can be increased and the combination of T, t, and v can be adjusted until the difference between the strain curves at any stage of the heating process reaches the tolerance range.

[0067] In step S2 above, by subjecting the cured epoxy sample 2 to a cycle of heating, isothermal treatment, and cooling, an optimal solution for reducing residual stress in the composite material used in the epoxy sample 2 was obtained. More specifically, since both the epoxy sample 2 and the epoxy composite insulation component 6 are unconstrained and the epoxy sample 2 has a smaller volume, it can be considered as a constituent unit of the epoxy composite insulation component 6. The epoxy sample 2 and the epoxy composite insulation component 6 use the same material system and are kept unconstrained during treatment, ensuring consistency in the strain-stress relationship and establishing a "unit-to-whole" stress transfer relationship. When the epoxy composite insulation component 6 uses the same composite material as the epoxy sample 2, the strain parameter variation law measured by the bidirectional strain gauge 3 in the epoxy sample 2 is applicable to the epoxy composite insulation component 6.

[0068] S3: Using the optimal combination of processing parameters, the epoxy composite insulation component 6 is subjected to stress reduction treatment through the same multi-stage thermal cycling process as step S2.

[0069] In this step, the epoxy composite insulation component 6 and the epoxy sample 2 are made of epoxy composite material with the same mass ratio. The epoxy composite insulation component 6 is an insulator for power equipment, including but not limited to insulators of any shape such as three-post insulators, basin insulators, or platform insulators, suitable for GIS / GIL insulation equipment. After the epoxy composite insulation component 6 is cured, it is subjected to cyclic treatment according to steps S2.1 to S2.4 using optimized temperature T, holding time t, cooling rate v, and number of cycles n, to achieve stress reduction treatment of the epoxy composite insulation component 6.

[0070] For example: Figure 2 The epoxy composite insulator 6 shown is a three-post insulator. The epoxy composite insulator 6 is placed in a programmable oven 1. The determined optimal processing parameter combination (i.e., optimized temperature T, holding time t, cooling rate v, and number of cycles n) is input into the programmable oven 1, and the epoxy composite insulator 6 is cyclically processed according to steps S2.1 to S2.4. More specifically, in this example, the optimal processing parameter combination is T = 145℃, t = 8h, v = 3℃ / h, and n = 6. The results before and after processing are as follows: Figure 4 and Figure 5 As shown in the figure, by comparing the stress distribution and stress value before and after treatment of the front and back sides of the three-post insulator (the front and back sides are relative and not specially distinguished), the maximum residual stress is reduced by about 50%, and the residual stress distribution after treatment is more uniform, indicating that the method provided by the present invention has a better effect on reducing the residual stress of epoxy composite insulators.

[0071] Based on the principle of the residual stress relief method for epoxy composite insulation components described above, this invention also proposes a residual stress relief device for epoxy composite insulation components, such as... Figure 2 As shown, the system mainly includes a programmable oven 1, a strain gauge 4, and a host computer 5. The programmable oven 1 is used to set and adjust the temperature T, holding time t, cooling rate v, and number of cycles n, and performs multi-stage thermal cycling treatment on the epoxy sample 2 with a built-in bidirectional strain gauge according to the above-set parameters. The strain gauge 4 is connected to the bidirectional strain gauge 3 via leads, and is used to upload the measured values ​​at each stage to the host computer 5 in real time. The host computer 5 is used to record the strain values ​​of the bidirectional strain gauge over time in each stage, and determines the optimal combination of processing parameters based on the strain data of the bidirectional strain gauge in each heating cycle.

[0072] Although the functions and working processes of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific functions and working processes described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these are within the protection scope of the present invention.

Claims

1. A method for relieving residual stress in epoxy composite insulation components, characterized in that, Includes the following steps: S1 Prepares epoxy specimens with bidirectional strain gauges; S2 subjected epoxy samples to multi-stage thermal cycling treatment, with each cycle including heating, isothermal, and cooling stages. The strain data from biaxial strain gauges were monitored and recorded in real time during each cycle. Based on the strain data from the biaxial strain gauges during each cycle, the optimal combination of treatment parameters for reducing residual stress in the epoxy composite material was determined. Specific process: S2.1 Reset the biaxial strain gauge at room temperature and start recording values. Use a programmable oven to heat the epoxy sample to the set temperature T. S2.2 After heating the epoxy sample to the set temperature T, it is kept at a constant temperature for the set holding time t. After the S2.3 isothermal treatment is completed, the epoxy sample is cooled to room temperature at the set cooling rate v. After the S2.4 epoxy sample cools to room temperature, the programmable oven stops working, the bidirectional strain gauge recording ends, and one heating process is completed. S2.5 Calculate the strain difference value of the biaxial strain gauge in this heating process and determine whether the strain difference value reaches the strain tolerance range. If yes, then the temperature T, holding time t, cooling rate v, and number of cycles n corresponding to this cycle are taken as the optimal processing parameter combination. If no, then adjust the temperature T, holding time t, cooling rate v, and number of cycles n, and repeat the above steps S2.1~S2.

5. In addition, if the number of heating process cycles n has reached the set maximum value but the strain difference value still does not meet the strain tolerance range requirement, then take the temperature T, holding time t, cooling rate v, and number of cycles n corresponding to the minimum strain difference value as the optimal processing parameter combination. S3 employs the optimal combination of processing parameters and follows the same multi-stage thermal cycling process as step S2 to perform stress reduction treatment on the epoxy composite insulation component; wherein, the epoxy composite insulation component and the epoxy sample are made of epoxy composite material with the same mass ratio.

2. The method for relieving residual stress in epoxy composite insulation components according to claim 1, characterized in that, The preparation process of the epoxy sample in step S1 is as follows: the epoxy composite material for preparing the epoxy composite insulation part is mixed in a specific ratio, heated to a molten state, degassed under vacuum and poured into a mold, cured and demolded to obtain the epoxy sample corresponding to the epoxy composite insulation part; wherein, a bidirectional strain gauge is suspended at the center of the mold.

3. The method for releasing residual stress in epoxy composite insulation components according to claim 1, characterized in that, The specific preparation process of the epoxy sample described in step S1 is as follows: S1.1 Pour the molten epoxy composite material into a mold with bidirectional strain gauges and begin curing; The epoxy composite material for preparing epoxy composite insulation parts is mixed in a specific ratio, heated to a molten state, and degassed under vacuum. At the same time, a bidirectional strain gauge is suspended at the center of the mold. The mold is placed in a programmable oven. After preheating the mold with the bidirectional strain gauge, the molten epoxy composite material after vacuum degassed is poured into the mold. The leads of the bidirectional strain gauge are connected to the strain gauge. The value measured by the strain gauge is transmitted to the host computer. The door of the programmable oven is closed, and curing begins. S1.2 Reset and record the bidirectional strain gauge values ​​during the curing process. Stop recording after curing is complete and the temperature drops to room temperature. Remove the epoxy sample from the mold. After setting the curing program in the programmable oven, the strain gauge values ​​are cleared and reset on the host computer. The values ​​of the bidirectional strain gauge change over time during the curing process are recorded until the curing is complete and the temperature drops to room temperature. The epoxy sample is then demolded from the mold. After demolding, the epoxy sample is free from fixed constraints, which eliminates the interference of fixed constraints on the bidirectional strain gauge values.

4. The method for relieving residual stress in epoxy composite insulation components according to claim 1, characterized in that, The bidirectional strain gauge described in step S1 consists of two strain gauges that are perpendicular to each other and have the same length.

5. The method for relieving residual stress in epoxy composite insulation components according to claim 1, characterized in that, The multi-stage thermal cycling process in step S2 includes: Heating stage: The epoxy sample is heated from room temperature to the set temperature T at a constant rate; Isothermal stage: The epoxy sample after heating treatment is held at a set temperature T for a set time t; Cooling stage: The epoxy sample after isothermal treatment is cooled to room temperature at a set cooling rate v; After completing one cycle of the above heating, constant temperature, and cooling stages, the cycle is repeated n times.

6. The method for relieving residual stress in epoxy composite insulation components according to claim 1, characterized in that, The epoxy composite insulation component is an insulator for power equipment, including three-post insulators, basin insulators, or platform insulators.

7. An apparatus for releasing residual stress in epoxy composite insulation components based on the residual stress release method of any one of claims 1 to 6, characterized in that, The system includes a programmable oven, a strain gauge, and a host computer. The programmable oven is used to set parameters: temperature T, holding time t, cooling rate v, and number of cycles n. Based on these parameters, a multi-stage thermal cycling treatment is performed on an epoxy sample with a built-in bidirectional strain gauge. The strain gauge is connected to the bidirectional strain gauge via leads to upload the measured values ​​from each stage to the host computer in real time. The host computer records the strain values ​​of the bidirectional strain gauge over time in each stage and determines the optimal combination of processing parameters based on the strain data from the bidirectional strain gauge during each heating cycle.

Images