Schlieren analysis method for ablation resistance enhancement mechanism of graphene modified copper-tungsten contact

Abstract

The invention belongs to the field of circuit breaker contact material design, and particularly relates to a schlieren analysis method for an ablation resistance enhancement mechanism of a graphene modified copper-tungsten contact. Comprising the following steps: S1, establishing a schlieren system calibration curve, carrying out a contact arc ablation schlieren observation experiment to obtain a schlieren image, and carrying out noise reduction processing on the schlieren image; s2, the transient temperature of a contact arc gap airflow column is calculated through a formula; s3, establishing a dynamic cooling rate model to dynamically fit the temperature data to obtain the cooling rate of the contact arc gap surface layer temperature; and S4, analyzing the enhancement mechanism of graphene doping modification on the ablation resistance of the copper-tungsten contact. According to the method, by comparing and analyzing the surface temperature and the cooling rate of the arc gap of the contact after ablation, the enhancement mechanism of graphene doping modification on the ablation resistance of the copper-tungsten contact is disclosed from the perspective of transient experimental phenomena, and a direct technical basis can be provided for optimizing the doping proportion and the preparation process of the graphene modified copper-tungsten contact material; and reference is provided for research and development of high-performance ablation-resistant contact materials.

Description

Technical Field

[0001] This invention belongs to the field of circuit breaker contact material design, and particularly relates to a schlieren analysis method for enhancing the ablation resistance of graphene-modified copper-tungsten contacts. Background Technology

[0002] High-voltage circuit breakers are crucial for the safe operation of large power grids, and the main factor affecting their service life is the ablation resistance of the contact material. To improve the ablation resistance of copper-tungsten contacts, researchers have attempted to optimize their performance through doping modification. Graphene, as a novel nano-reinforcing phase, demonstrates unique advantages in the field of metal matrix composites due to its multi-dimensional superior properties.

[0003] In recent years, there has been considerable research on the preparation of graphene-modified copper-tungsten contact materials. However, research on the mechanism of enhancing the ablation resistance of materials has mostly focused on directly capturing the dynamic evolution of the arc with high-speed cameras. Arc ablation is a violent and complex physical process that occurs in a very small space on a millisecond timescale. It involves a variety of complex phase transitions, such as heat absorption, heat conduction, crystal evaporation and vaporization, melting and solidification, and is accompanied by a variety of dynamic changes, such as high-temperature melting of materials and droplet splashing. There is still a lack of support from actual transient experimental phenomena.

[0004] Schlieren technology is a temperature field distribution measuring instrument based on the knife-edge shadow method. By spatially filtering low-frequency components through a knife-edge component, it can intuitively display the details of the measured area, achieving a visualization effect and allowing the derivation of key parameters such as temperature distribution. It has been preliminarily applied to the observation and research of electric arc phenomena. However, current research has not comprehensively considered multiple angles and dimensions, such as the calibration accuracy of the schlieren system, schlieren image noise reduction processing, cooling processing, and the correlation between transient parameters and graphene modification mechanisms, to elucidate the mechanism by which graphene doping enhances the ablation resistance of copper-tungsten contacts. This has limited the optimized design and engineering application of modified copper-tungsten contact materials.

[0005] Therefore, developing a schlieren analysis method to accurately acquire the transient characteristics of contact arc erosion and scientifically reveal the enhancement mechanism of graphene modification is of great theoretical significance for promoting the research and application of high-performance modified contact materials. Summary of the Invention

[0006] In view of this, this application provides a schlieren analysis method for enhancing the ablation resistance of graphene-modified copper-tungsten contacts. By calculating the transient temperature of the axial center of the airflow column in the contact arc gap and establishing a dynamic cooling rate model to fit the temperature data, the enhancement mechanism of graphene doping modification on the ablation resistance of copper-tungsten contacts can be analyzed based on transient experimental phenomena. This provides a reference for the preparation and improvement of graphene-modified electrical contact materials with higher ablation resistance.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A schlieren analysis method for enhancing the ablation resistance of graphene-modified copper-tungsten contacts includes the following steps:

[0009] S1. Establish the schlieren system calibration curve, conduct schlieren observation experiments on contact arc ablation, obtain schlieren images, and perform noise reduction processing on the schlieren images;

[0010] S2. Using schlieren images, calculate the transient temperature of the airflow column in the contact arc gap through formula derivation;

[0011] S3. Establish a dynamic cooling rate model to dynamically fit the temperature data and obtain the cooling rate of the surface temperature of the contact arc gap;

[0012] S4. Analyze the mechanism by which graphene doping modification enhances the ablation resistance of copper-tungsten contacts.

[0013] Preferably, the calibration curve in step S1 includes the correspondence between pixel grayscale values ​​and cutting depth.

[0014] The observation experiment used a schlieren system to observe the arc ablation of the contact material and used a two-dimensional adaptive Wiener filter to process the noise in the schlieren image.

[0015] Preferably, the calculation of the transient temperature of the airflow column in the contact arc gap in step S2 includes the following steps:

[0016] a) Extract the gray values ​​of pixels on a horizontal cross section of the schlieren image described in step S1, and convert the gray values ​​of the cross section into the corresponding cutting amount by interpolation function according to the calibration curve in step S1. This value is equivalent to the light offset Δa in the schlieren optical path. Then, calculate the distribution of the light deflection angle α according to the properties of the focal plane. Finally, fit the obtained distribution of the light deflection angle using cubic spline interpolation to obtain the fitting curve between the light deflection angle α and its radial coordinate.

[0017] Preferably, the relationship between the light deflection angle α and the light offset at the knife edge is as follows:

[0018] Δa=f2tanα≈f2α

[0019] In the formula: f2 is the focal length of the schlieren system lens.

[0020] b) Determine the axisymmetry center of the arc gap airflow column, use it as the origin of the coordinate system, retain the data on one side, and correct the radial coordinates. Based on the relationship between the light deflection angle α obtained in step a) and its radial position, use the inverse Abel transform to calculate the refractive index at the corresponding position of the arc gap airflow column;

[0021] Preferably, the formula for calculating the refractive index based on the inverse Abel transform is:

[0022]

[0023] In the formula: r is the radial coordinate, R is the outermost radius of the axisymmetric temperature field section, α(y) is the light deflection angle distribution curve, and n0 is the refractive index of the ambient gas.

[0024] c) The radial distribution of temperature T in the arc gap gas column is derived from the Gladstone-Dale law, the ideal gas equation of state, and the definition of gas density.

[0025] The expression for the radial temperature distribution is as follows:

[0026]

[0027] In the formula: T(r) is the radial temperature distribution of the axisymmetric temperature field, and T0 is the ambient temperature during the experiment.

[0028] It should be noted that: after the above-mentioned graphene / copper-tungsten contact material is ablated by electric arc, the high-temperature gas flow is rapidly ejected from the arc gap hole and diffuses to both sides to form a high-temperature gas flow column. The structure of this gas flow column approximately satisfies axisymmetry; while the schlieren system is a temperature field distribution measuring instrument designed based on the knife-edge shadow method. It uses the knife-edge component to perform spatial filtering on the low-frequency components, displaying the details of the area to be measured, thereby achieving a visualization effect.

[0029] Preferably, the dynamic cooling rate model in step S3 dynamically fits the temperature data, including the following steps:

[0030] First, the cooling rate k(t) is determined by the dynamic fitting function: k(t)=k0+k1t, where k0 and k1 are the parameters to be fitted, representing the initial cooling rate and the rate of change of the cooling rate, respectively.

[0031] Secondly, substituting the dynamic fitting function into Newton's law of cooling yields the following formula:

[0032]

[0033] In the formula: T(t) is the data temperature, T env Ambient temperature;

[0034] Furthermore, simplifying the above formula, and setting the initial time of the experimental data as the model time t0 = 0, the derived formula for the temperature change over time in this model is:

[0035] T(t) = T env +(T0-T env )exp(-k0t-0.5k1t 2 )

[0036] In the formula: T0 is the initial temperature value;

[0037] Finally, the model parameters are optimized using the nonlinear least squares method. By iteratively adjusting the parameter values, the sum of squared residuals S between the calculated temperature and the actual measured temperature is minimized. This optimization is achieved when both the parameter change Δk and the reduction in the sum of squared residuals ΔS are below a preset tolerance threshold of 10. -12 The iteration stops when convergence is reached, indicating that the final fitted parameters are obtained. The coefficient of determination R0 is then used. 2 The fitting effect is evaluated.

[0038] Preferably, the formula for the residual sum of squares S is:

[0039]

[0040] In the formula: N is the number of data points, T(t) i (T) is the temperature value predicted by the model. exp (t i () is the measured temperature value;

[0041] The determination coefficient R 2 The expression is:

[0042]

[0043] In the formula: It is the average value of the measured temperature.

[0044] It is important to note that the heat dissipation performance of graphene / copper-tungsten contact materials is a key factor in their resistance to arc erosion. To quantitatively describe the temperature drop rate of the contact after arc erosion, a dynamic cooling rate model needs to be established to fit the temperature data, thereby comparing the heat dissipation performance of graphene / copper-tungsten contact materials. Simultaneously, the coefficient of determination R0 is used. 2 As an evaluation metric for model fit: when R² ≥ 0.95, it indicates that the model has excellent fitting accuracy and strong explanatory power; when the R² value is between 0.90 and 0.95, it indicates that the model fit is at an acceptable level; when R² is less than 0.95, it indicates that the model fit is at an acceptable level. 2 If the value is less than 0.90, it indicates that the model needs further optimization and adjustment.

[0045] Preferably, step S4 is based on the results obtained in steps S2 and S3, and analyzes the enhancement mechanism of graphene doping modification on the ablation resistance of copper-tungsten contacts.

[0046] Preferably, the schlieren observation experiment in step S1 is conducted using a schlieren system, which consists of a high-speed camera, a knife edge, a light source system, a collimating lens, and a converging lens arranged coaxially.

[0047] Compared with the prior art, the beneficial effects of the present invention are:

[0048] This application, by analyzing the transient temperature calculation results of the arc gap airflow column and the dynamic fitting results of the temperature data with the dynamic cooling rate, can systematically obtain the temperature change law of the copper-tungsten contact arc ablation process under the influence of graphene doping modification. Specifically:

[0049] 1) A calibration curve was established between pixel grayscale values ​​and blade cutting amount, achieving accurate calibration of the schlieren system. Two-dimensional adaptive Wiener filtering technology was introduced into the schlieren observation experiment to process noise in the schlieren image, ensuring the accuracy of subsequent grayscale values ​​and other data.

[0050] 2) Based on the combination of the axisymmetry center correction and Abel inverse transformation of the arc gap airflow column, the refractive index distribution of the arc gap airflow column is accurately solved. Combined with the derivation logic of Glaston-Dale law, ideal gas equation of state and gas density definition, the accurate calculation of the transient temperature radial distribution of the arc gap airflow column is realized.

[0051] 3) To address the dynamic change of cooling rate over time during the actual heat dissipation process of the contacts, a dynamic fitting function was used to optimize the Newton's law of cooling model, making the model more consistent with the actual heat dissipation physical process and significantly improving the adaptability of temperature data fitting. At the same time, to ensure the reliability of the fitting results, the fitting effect was evaluated.

[0052] The above precise positioning of the heat dissipation process in the ablation resistance of graphene / copper-tungsten contacts and the quantification of the temperature drop rate solve the technical pain point of traditional methods being unable to quantify the relationship between modification mechanisms and ablation resistance performance. This provides direct technical basis for optimizing the doping ratio and preparation process of graphene-modified copper-tungsten contact materials, and offers a reference for the development of high-performance ablation-resistant contact materials. Attached Figure Description

[0053] Figure 1 This is a flowchart of the present invention;

[0054] Figure 2 This refers to the schlieren system calibration curve and the blade reference position in this embodiment of the invention.

[0055] Figure 3 These are schlieren images of arc ablation of two types of contacts, CuW80 and CuW80Gr0.15wt%, in embodiments of the present invention.

[0056] Figure 4 This is a fitted curve between the CuW80 contact light deflection angle α and its radial coordinate at a certain moment in an embodiment of the present invention;

[0057] Figure 5This is a radial temperature distribution diagram of the high-temperature airflow column in the arc gap of two types of contacts, CuW80 and CuW80Gr0.15wt%, in the embodiments of the present invention;

[0058] Figure 6 This is a graph showing the change in the core temperature of the airflow column of CuW80 and CuW80Gr0.15wt% as a function of time in an embodiment of the present invention.

[0059] Figure 7 The results are the fitting results of the dynamic cooling rate model for the surface temperature of the contact arc gap of CuW80 and CuW80Gr0.15wt% in the embodiments of the present invention. Detailed Implementation

[0060] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.

[0061] In the embodiments of this application, two types of contacts were used to compare and demonstrate the effectiveness of the schlieren analysis method of this application during the contact arc ablation schlieren observation experiment. The two types of contacts were a CuW80 alloy and a CuW80Gr composite material containing 0.15wt% graphene. The contact material samples were Φ30*20mm cylinders. The two contacts were fixed parallel to each other on a copper base of the ablation platform with a fixed gap of 70μm. The current waveform was selected as a pulse waveform, and the capacitor charging voltage was 1kV. Figure 1 The flowchart shown below details the specific steps:

[0062] S1. Establish a calibration curve, i.e., calibrate the schlieren system to ensure the entire optical path is undisturbed. Starting from the position where the blade does not obstruct the light spot, cut the light spot with a constant step size while simultaneously acquiring images to obtain a grayscale distribution image with a uniform brightness gradient. A calibration curve is established by averaging the grayscale values ​​of the effective region pixels. During the ablation experiment, the blade cuts at the center of the light spot to maximize the system's dynamic range and maintain the quasi-linear characteristics of grayscale changes. The results are as follows: Figure 2 As shown in the figure, the reference position of the blade edge is marked. Two-dimensional adaptive Wiener filtering is used to process the noise in the schlieren image, and the resulting image is shown below. Figure 3 The images shown are schlieren images of the ablation of the two contact materials.

[0063] Furthermore, observation of the schlieren images revealed that during the arcing process, the contact gap emitted a strong glow for approximately 1.60 ms. The images clearly captured the splashing of high-temperature molten metal droplets caused by the high-temperature arcing. The phenomenon of droplets colliding with and rebounding from the bottom of the ablation platform base at 17.12 ms was particularly evident, and it was found that after 20.00 ms, the contact material essentially ceased generating new molten metal droplets. During the ablation process, high-temperature gas flow rapidly ejected from the arc gap orifice and diffused to both sides, forming a high-temperature gas flow column. The structure of this gas flow column approximately satisfies axisymmetry, exhibiting significant changes within the time frame from 0 to 68 ms. After 68 ms, the evolution rate of this gas flow column gradually slowed down.

[0064] S2. Calculate the transient temperature of the airflow column in the contact arc gap.

[0065] Because the high-temperature gas flow rapidly ejects from the arc gap hole and diffuses to both sides after the contact material is ablated by electric arc, forming a high-temperature gas flow column, the structure of this gas flow column approximately satisfies axisymmetry; while the schlieren system is a temperature field distribution measuring instrument based on the knife-edge shadow method. Through the knife-edge component, it spatially filters the low-frequency components, enabling it to display the details of the measured area, thus achieving a visualization effect. The calculation of the transient temperature of the arc gap gas flow column includes the following sub-steps:

[0066] Step 1: Extract the grayscale values ​​of pixels on the horizontal cross-section of the airflow column in the schlieren image at a distance of 3mm from the bottom of the schlieren gap. Based on the obtained calibration curve, convert the cross-sectional grayscale values ​​into the corresponding cutting amount at the blade edge using an interpolation function. This value is equivalent to the light ray offset Δa in the schlieren optical path. Then, calculate the distribution of the light ray deflection angle α based on the properties of the focal plane. The relationship between the light ray deflection angle α and the light ray offset at the blade edge is: Δa=f2tanα≈f2α, where f2 is the focal length of the schlieren system lens. The obtained distribution of the light ray deflection angle is then fitted using cubic spline interpolation. The fitted curve between the light ray deflection angle α of the CuW80 contact at a certain moment and its radial coordinate is shown below. Figure 4 As shown.

[0067] Step 2: Determine the axisymmetry center of the airflow column in the arc gap, such as... Figure 4 Point O is marked as the center of the arc gap airflow column. It is used as the origin of the coordinate system, retaining data from one side and correcting the radial coordinates. Based on the relationship between the light deflection angle α obtained in step 1 and its radial position, the refractive index n(r) at the corresponding position of the arc gap airflow column is calculated using the inverse Abel transform. The formula for calculating the refractive index based on the inverse Abel transform is:

[0068]

[0069] In the formula: r is the radial coordinate, R is the outermost radius of the axisymmetric temperature field section, α(y) is the light deflection angle distribution curve, and n0 is the refractive index of the ambient gas.

[0070] Step 3: Derive the radial distribution of temperature T in the arc gap gas column using the Gladstone-Dale law, the ideal gas law, and the definition of gas density. The expression for the radial temperature distribution is:

[0071]

[0072] In the formula: T(r) is the radial temperature distribution of the axisymmetric temperature field, and T0 is the ambient temperature during the experiment.

[0073] like Figure 5 The figure shows the radial temperature distribution of the high-temperature gas flow column in the arc gap of two types of contacts: CuW80 and CuW80Gr (0.15 wt%). The radial temperature distribution shows that at the same moment, the temperature is highest at the center of the gas flow column in the arc gap, and gradually decreases with radial deviation. Furthermore, the temperature value also gradually decreases over time. Since the center of the gas flow column is located 3 mm directly below the arc gap, and the high-temperature gas is ejected rapidly, the temperature at this point more effectively reflects the temperature changes on the surface of the contact arc gap. The statistical changes in the temperature at the center of the gas flow column over time are shown below. Figure 6 As shown.

[0074] S3. Establish a dynamic cooling rate model to dynamically fit the temperature data.

[0075] The heat dissipation performance of graphene / copper-tungsten contact materials is a key factor in their resistance to arc ablation. To quantitatively describe the temperature drop rate of the contact after arc ablation, a dynamic cooling rate model is established and fitted to the temperature data to compare the heat dissipation performance of graphene / copper-tungsten contact materials. This involves the following sub-steps.

[0076] Step 1: Since the traditional Newton's law of cooling assumes that the cooling rate k is constant, however, in the actual heat dissipation process of the contact material, the cooling rate often changes with time, especially in high-temperature environments, where the heat dissipation mechanism may dynamically adjust due to temperature changes. Therefore, a dynamic fitting function is used:

[0077] k(t) = k0 + k1t

[0078] In the formula, k0 and k1 are the parameters to be fitted, representing the initial cooling rate and the rate of change of the cooling rate, respectively, which can more accurately describe the variation law of the experimental data.

[0079] Step 2: Substituting the dynamic fitting function from Step 1 into Newton's law of cooling, we obtain:

[0080]

[0081] In the formula: T(t) is the data temperature, and Tenv is the ambient temperature.

[0082] This equation describes the dynamic process of temperature change over time, where the cooling rate depends not only on the current temperature difference but also on the continuous change over time.

[0083] Step 3: To simplify the formula, the initial time of the experimental data is set to the model time t0 = 0. The derived formula for the temperature change over time in this model is:

[0084] T(t) = T env +(T0-T env )exp(-k0t-0.5k1t 2 )

[0085] In the formula: T0 is the initial data temperature value.

[0086] Step 4: During the fitting process, the nonlinear least squares method is used to optimize the model parameters. The parameter values ​​are adjusted iteratively to minimize the sum of squared residuals S between the calculated temperature and the actual measured temperature. When both the parameter change Δk and the decrease in the sum of squared residuals ΔS are lower than the preset tolerance threshold (10), the model is considered optimized. -12 The iteration stops when the condition is met, indicating that convergence has been achieved and the final fitted parameters are obtained. The coefficient of determination R0 is then used. 2 The fit was evaluated. The sum of squared residuals S and the coefficient of determination R were used. 2 The expressions are as follows:

[0087]

[0088] In the formula: N is the number of data points, T(t) i (T) is the temperature value predicted by the model. exp (t i () is the measured temperature value. It is the average value of the measured temperature.

[0089] Using the coefficient of determination R 2 As an evaluation metric for model fit: when R² ≥ 0.95, it indicates that the model has excellent fitting accuracy and strong explanatory power; when the R² value is between 0.90 and 0.95, it indicates that the model fit is at an acceptable level; when R² is less than 0.95, it indicates that the model fit is at an acceptable level. 2 If the value is less than 0.90, it indicates that the model needs further optimization and adjustment.

[0090] Furthermore, the fitting process in step 4 is as follows: When the contact material temperature is high, the heat radiation dissipation effect is significant, rapidly reducing the temperature. However, as the temperature decreases, the contribution of radiation dissipation weakens sharply, causing the material cooling rate to slow down. At the same time, the airflow-driven heat dissipation mechanism also changes accordingly. Figure 6In the first stage of the axial temperature decrease, high-temperature gas is ejected from the arc gap, forming strong natural convection that rapidly carries away heat. Therefore, the calculated gas temperature data effectively reflects the temperature change of the contact material surface. However, in the second stage, when the temperature drops to a certain value (644K for CuW80 and 710K for CuW80Gr), the thermal driving force weakens, the airflow velocity decreases, and the intensity of natural convection weakens. At this point, the inverted temperature values ​​are affected by the natural dissipation of temperature at the measurement location, making it difficult to effectively reflect the temperature change of the contact material, and reducing the representativeness of the data. Therefore, it was decided to fit only the axial temperature change over time data in stage one (20-60ms for CuW80 and 20-40ms for CuW80Gr) to ensure the representativeness of the data.

[0091] Furthermore, in this experiment, the ambient temperature Tenv = 288K was known. The initial time of the temperature data (20ms after arc ablation) is the initial time t0 = 0 in the model, corresponding to the temperature values ​​T0 as T0(CuW80) = 2292K and T0(CuW80Gr) = 1797K. The initial parameters were set as k0 = k1 = 0.1. The model fitting results are as follows: Figure 7 As shown, the coefficient of determination of the fitting result is R. 2 (CuW80)=0.9879, R 2 (CuW80Gr) = 0.9768, indicating that the model fit for both sets of data is very good and can accurately reflect the temperature change of the arc gap surface of the contact material. The fitting parameters are as follows:

[0092] k0(CuW80)=0.02ms -1 k1(CuW80) = 0.0012ms -2 ;

[0093] k0(CuW80Gr)=0.06ms -1 k1(CuW80Gr)=0.0005ms -2 .

[0094] S4. Based on the results obtained in steps S2 and S3, the enhancement mechanism of graphene doping modification on the ablation resistance of copper-tungsten contacts was analyzed. Specifically, after arc ignition, the surface temperature of the arc gap of the CuW80Gr contact remained lower than that of the CuW80 material. At 20 ms after arc ablation, the axial temperatures of the gas flow column in the arc gap of CuW80 and CuW80Gr were 2292 K and 1797 K, respectively; at 120 ms, the temperatures dropped to 450 K and 378 K, respectively. From... Figure 5It can be seen that the temperature drop rate of CuW80Gr axial core is significantly faster than that of CuW80 in the high-temperature stage. CuW80Gr drops from 1797K in 20ms to 1076K in 30ms, a decrease of 721K; while CuW80 drops from 2291K in 20ms to 1856K in 30ms, a decrease of only 435K. Figure 6 The comparison curves further show that the axial temperature of the CuW80Gr arc gap airflow column is lower than that of CuW80 at all times after ablation. Calculations show that the overall average temperature of CuW80Gr is only 71% of that of CuW80. Compared to CuW80, CuW80Gr has a faster contact temperature cooling rate, with its maximum cooling rate being nearly three times higher than that of CuW80.

[0095] The above analysis results show that the cooling rate of the CuW80Gr0.15wt% contact material is significantly faster than that of CuW80, demonstrating superior thermal conductivity and energy dispersion. This is because graphene, due to its high thermal conductivity, effectively undertakes the function of heat transfer in the composite material, improving the thermal conductivity efficiency of the composite matrix. The introduction of graphene promotes the rapid diffusion of heat from the material surface to the interior, thereby reducing local high temperature peaks, making the temperature distribution more uniform, and effectively mitigating thermal erosion and damage to the material surface.

[0096] Through schlieren analysis of the enhanced ablation resistance mechanism of graphene-modified copper-tungsten contacts, it was found that compared with traditional simulation methods, this method can reveal the enhanced arc ablation resistance mechanism of graphene doping modification on copper-tungsten contacts based on transient experimental phenomena, which can provide a reference for designing graphene-modified electrical contact materials with higher ablation resistance.

[0097] The above description is merely an example of the embodiments of this application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A schlieren analysis method of the ablation resistance enhancement mechanism of graphene-modified copper tungsten contact, characterized by, The method comprises the following steps: S1. Establishing a schlieren system calibration curve, carrying out a contact arc ablation schlieren observation experiment, obtaining a schlieren image and carrying out noise reduction processing on the schlieren image; S2. Combining the schlieren image, calculating the transient temperature of the contact arc gap airflow column through formula derivation; S3. Establishing a dynamic cooling rate model to dynamically fit the temperature data, and obtaining the cooling rate of the surface temperature of the contact arc gap; S4. Analyzing the enhancement mechanism of graphene doping modification on the arc ablation resistance of copper-tungsten contacts.

2. The schlieren analysis method of the ablation resistance performance enhancement mechanism of graphene-modified copper tungsten contacts according to claim 1, characterized in that, The calibration curve in the step S1 includes the corresponding relationship between the pixel point gray value and the knife edge cutting amount. The observation experiment adopts a schlieren system to observe the arc ablation of the contact material and adopts a two-dimensional adaptive wiener filter to process the noise of the schlieren image.

3. The schlieren analysis method of the ablation resistance performance enhancement mechanism of graphene-modified copper tungsten contacts according to claim 1, characterized in that, The step S2 of calculating the transient temperature of the contact arc gap airflow column comprises the following steps: a) Extracting the pixel point gray value of a certain horizontal cross section of the schlieren image in the step S1, and converting the cross section gray value into the corresponding knife edge cutting amount through the interpolation function according to the calibration curve in the step S1, which is equivalent to the light ray offset amount Δa in the schlieren light path, then calculating the distribution of the light ray deflection angle α according to the properties of the focal plane, and finally fitting the obtained light ray deflection angle distribution by using the cubic spline interpolation method to obtain the fitting curve between the light ray deflection angle α and the radial coordinate; b) Determining the axisymmetric center of the arc gap airflow column as the coordinate origin, retaining the data on one side and correcting the radial coordinate. According to the relationship between the light ray deflection angle α and the radial position obtained in the step a), the refractive index of the corresponding position of the arc gap airflow column is calculated by using the Abel inverse transform; c) The radial distribution of the arc gap airflow column temperature T is derived from the Gladstone-Dale law, the ideal gas state equation and the definition of gas density.

4. The schlieren analysis method of the ablation resistance performance enhancement mechanism of graphene-modified copper tungsten contacts according to claim 3, characterized in that, In the step a), the relationship between the light ray deflection angle α and the light ray offset amount Δa at the knife edge is: Δa = f2tanα ≈ f2α In the formula, f2 is the focal length of the schlieren system.

5. The schlieren analysis method of the ablation resistance enhancement mechanism of graphene-modified copper tungsten contacts according to claim 3, characterized in that, In the step b), the refractive index calculation formula based on the Abel inverse transform is: In the formula: r is the radial coordinate, R is the outermost circle radius of the axisymmetric temperature field cross section, α(y) is the light ray deflection angle distribution curve, and n0 is the refractive index of the ambient gas.

6. The schlieren analysis method of the ablation resistance performance enhancement mechanism of graphene-modified copper tungsten contacts according to claim 3, characterized in that, In the step c), the temperature radial distribution expression is: In the formula: T(r) is the temperature radial distribution of the axisymmetric temperature field, and T0 is the ambient temperature at the time of the experiment.

7. The schlieren analysis method of ablation resistance performance enhancement mechanism of graphene-modified copper tungsten contact according to claim 1, characterized in that, In the step S3, the dynamic cooling rate model dynamically fits the temperature data, comprising the following steps: Firstly, the cooling rate k(t) is determined through a dynamic fitting function: k(t) = k0 + k1t, wherein k0 and k1 are to-be-fitted parameters, respectively representing the initial cooling rate and the variation rate of the cooling rate; Secondly, the dynamic fitting function is brought into the Newton cooling law to obtain the formula: where: T(t) is the data temperature, T env is the ambient temperature; Then, the above formula expression is simplified, the initial time of the experimental data is set as the model time t0 = 0, and through derivation, the formula of the model temperature changing with time is: T(t) = T env + (T0-T env ) exp(-k0t-0.5k1t 2 ) In the formula: T0 is the initial data temperature value; Finally, the nonlinear least square method is used to optimize the model parameters, and the parameter values are adjusted iteratively to minimize the residual sum of squares S between the model calculated temperature and the actual measured temperature. When the parameter variation Δk and the residual sum of squares reduction ΔS are both lower than the preset tolerance threshold 10 -12 , the iteration is stopped, indicating that the convergence state has been reached to obtain the final fitting parameters, and the determination coefficient R 2 is used to evaluate the fitting effect.

8. The schlieren analysis method of the ablation resistance performance enhancement mechanism of graphene-modified copper tungsten contacts according to claim 7, characterized in that, The residual sum of squares S formula is: where: N is the number of data points, T(t i ) is the model predicted temperature value, T exp (t i ) is the measured temperature value; The determination coefficient R 2 is expressed by the formula: In the formulae: is the average value of the measured temperature.

9. The schlieren analysis method of ablation resistance performance enhancement mechanism of graphene-modified Cu-W contact according to claim 1, characterized in that, The step S4 is based on the results obtained in the step S2 and the step S3, and analyzes the enhancement mechanism of the ablation resistance of the copper-tungsten contact by graphene doping modification.

10. The schlieren analysis method of ablation resistance performance enhancement mechanism of graphene-modified copper tungsten contact according to claim 1, characterized in that, In the step S1, the schlieren observation experiment is observed by using a schlieren system, and the schlieren system is composed of a high-speed camera, a knife edge, a light source system, a collimating lens and a converging lens arranged in the same axis.

Images