CN119164529B - A method for detecting thermal stress of high-voltage porcelain bushing based on nanoindentation technology - Google Patents
A method for detecting thermal stress of high-voltage porcelain bushing based on nanoindentation technology Download PDFInfo
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Abstract
本发明属于热应力检测技术领域，特别是指一种基于纳米压痕技术对高压电瓷套管热应力的检测方法，步骤包括对纳米压痕测试仪进行性能测试，确定其误差位于正常误差范围内；将已炸裂损坏的高压电瓷套管切割成适合进行纳米压痕测试的多个待筛选样品，筛选适合进行纳米压痕测试的测试样品；进行压痕实验，记录压头的载荷‑位移曲线；对载荷‑位移曲线进行分析；代入Suresh模型公式计算瓷套管的残余热应力；通过对比不同区域的残余热应力，分析瓷套管内部的应力分布情况；评估瓷套管的损坏模式。本发明利用纳米压痕技术和Suresh模型，能够在微观尺度上准确评估瓷套管的残余热应力状态，方法操作简便。
The present invention belongs to the field of thermal stress detection technology, and in particular refers to a method for detecting thermal stress of high-voltage electric porcelain bushings based on nanoindentation technology, the steps of which include performing a performance test on a nanoindentation tester to determine that its error is within a normal error range; cutting the high-voltage electric porcelain bushings that have been cracked and damaged into a plurality of samples to be screened suitable for nanoindentation testing, and screening test samples suitable for nanoindentation testing; performing an indentation experiment, and recording the load-displacement curve of the indenter; analyzing the load-displacement curve; substituting the Suresh model formula to calculate the residual thermal stress of the porcelain bushing; analyzing the stress distribution inside the porcelain bushing by comparing the residual thermal stress in different regions; and evaluating the damage mode of the porcelain bushing. The present invention utilizes nanoindentation technology and the Suresh model to accurately evaluate the residual thermal stress state of the porcelain bushing at a microscopic scale, and the method is simple to operate.
Description
Technical Field
The invention belongs to the technical field of thermal stress detection, and particularly relates to a method for detecting thermal stress of a high-voltage electric porcelain bushing based on a nano indentation technology.
Background
In the field of bioenergy, in particular to the power generation and transmission process of biomass energy, the safe operation of high-voltage electric equipment is critical to the stability and efficiency of the whole system. The reliability of the high-voltage porcelain bushing, which is used as a key insulating component in power equipment, is directly related to the safe and stable operation of the system. However, the porcelain bushing has two main problems in practical application, namely that the porcelain bushing has higher brittleness, low fracture toughness, smaller damage tolerance and extremely sensitivity to cracks, and the porcelain bushing lacks an effective mechanical strength (especially crack) state detection means in the running process, so that the capability of preventing explosion accidents is insufficient.
Residual thermal stress is stress that remains inside the object due to non-uniform temperature changes, plastic deformation, or phase changes in the manufacturing process of the workpiece. Such stresses, when present in equilibrium inside the object without external factors, have a very important impact on the shape, size and performance of the component. In high voltage porcelain bushings, the presence of residual thermal stresses is prone to sudden damage and the consequences are often very serious, especially when they are present on the load bearing and rotating parts, which can lead to serious accidents.
During operation, the ceramic sleeve is subject to thermal stresses due to internal and external temperature differentials. This thermal stress creates a tensile and compressive stress that balances each other between the surface and the interior of the porcelain bushing. At room temperature, the skin is typically under compressive stress, while the interior is under tensile stress, which is also known as thermal stress. In addition, stresses generated during phase transformation, such as eutectic crystals and eutectoid transformation in cast iron, also lead to the generation of residual thermal stresses.
Conventional residual thermal stress detection methods include mechanical measurements and non-destructive measurements. Mechanical measurements, such as blind hole methods, calculate the magnitude of residual stress by drilling holes in the workpiece to relieve local residual stress. Nondestructive measurement rules include X-ray diffraction, magnetic, ultrasonic, etc., which indirectly calculate residual stress by measuring changes in physical constants inside the material. However, these methods have limitations in detecting the porcelain bushing, such as high requirements for the surface state, or inability to accurately measure the internal stress distribution. The nano indentation technology is used as an emerging mechanical property testing means of materials, and is widely applied to detection of metals, alloys, semiconductors, glass, minerals, organic materials and the like due to the advantages of high precision, high resolution and the like. The nano indentation instrument applies a tiny load on the surface of a material by using a diamond probe, gives an indentation to the test material, measures the formation and deformation of the indentation, and deduces the residual thermal stress state inside the material by analyzing the change of a load-displacement curve. The method can reveal the mechanical response of the material due to residual thermal stress in the stressing process, thereby providing important data for evaluating the safety and reliability of the material.
Therefore, the development of the method for detecting the residual thermal stress of the high-voltage ceramic sleeve based on the nanoindentation technology has important significance for analyzing the residual thermal stress of the sleeve which is already burst and damaged.
Disclosure of Invention
The invention aims to provide a method for detecting the thermal stress of a high-voltage electric porcelain bushing based on a nano indentation technology, which is used for analyzing the residual thermal stress of the bushing which is damaged by explosion, and can evaluate the residual thermal stress state of the damaged bushing and provide scientific basis for accident analysis and prevention.
The technical scheme adopted for solving the technical problems is that the method for detecting the thermal stress of the high-voltage electric porcelain bushing based on the nanoindentation technology comprises the following steps:
Step 1, performing performance test on a nano indentation tester to determine that the error is within a normal error range;
Step 2, under the condition that the error of the nano indentation tester is within the normal error range, cutting the high-voltage ceramic sleeve which is subjected to cracking damage into a plurality of samples to be screened which are suitable for nano indentation testing, polishing the samples to be screened, acquiring sample surface data of each sample, and screening test samples which are suitable for nano indentation testing based on the sample surface data, wherein the sample surface data comprise surface roughness, surface glossiness, surface crack quantity and surface stain quantity;
Step 3, using a nano indentation instrument positioned in a normal error range to carry out indentation experiments on the test sample, and recording a load-displacement curve of the pressure head;
Step 4, analyzing the load-displacement curve, and calculating and extracting a contact area A 0 when the contact area A and the maximum load P max are extracted from the load-displacement curve;
Step 5, substituting the contact areas A and A 0 determined in the experiment and the hardness H of the material into a Suresh model formula to calculate the residual thermal stress of the porcelain bushing;
step 6, analyzing stress distribution conditions in the porcelain bushing by comparing residual thermal stresses in different areas;
And 7, evaluating the damage mode of the porcelain bushing according to the distribution and the magnitude of the residual heat stress.
Preferably, in the step 1, performance test is performed on the nanoindentation tester, and the error is determined to be within the normal error range, including the following steps:
Carrying out indentation experiments on the standard material by using a nano indentation tester to obtain standard material test data, wherein the standard material test data comprises a test indentation recovery rate, a test unloading curve slope, a test depth drift rate and a test elastic modulus;
Obtaining actual data of a standard material, wherein the actual data of the standard material comprises an actual indentation recovery rate, an actual unloading curve slope, an actual depth drift rate and an actual elastic modulus;
Processing standard material test data and standard material actual data to obtain standard material test deviation data, wherein the standard material test deviation data comprises indentation recovery rate deviation, unloading curve slope deviation, depth drift rate deviation and elastic modulus deviation;
analyzing based on standard material test deviation data and material test deviation allowable data stored in a database to obtain a test deviation matching value, wherein the material test deviation allowable data comprises indentation recovery rate allowable deviation, unloading curve slope allowable deviation, depth drift rate allowable deviation and elastic modulus allowable deviation;
Comparing the test deviation matching value with a test deviation matching value threshold stored in a database, and if the test deviation matching value is smaller than the test deviation matching value threshold, positioning the error of the nano indentation tester in a normal error range;
If the test deviation matching value is not smaller than the test deviation matching value threshold, the error of the nanoindentation tester is out of the normal error range, and the standard material test deviation data is compared with the standard material test deviation matching data stored in the database to determine the closest standard material test deviation matching data;
Based on the closest standard material test deviation matching data, the stored nano indentation tester fault reasons corresponding to the closest standard material test deviation matching data are obtained from a database.
Preferably, the determining the closest standard material test deviation matching data includes the steps of:
Comprehensively analyzing standard material test deviation data and standard material test deviation matching data stored in a database to obtain a test comparison value, wherein the standard material test deviation matching data comprises indentation recovery rate matching deviation, unloading curve slope matching deviation, depth drift rate matching deviation and elastic modulus matching deviation;
and the standard material test deviation matching data stored in the database corresponding to the maximum test comparison value is the closest standard material test deviation matching data.
Preferably, in the step 2, the damaged high-voltage ceramic sleeve is cut into a sample with a diameter smaller than phi 50mm and a height smaller than 10mm, the surface of the sample is polished and polished, the roughness of the loading surface is ensured to reach the nano level and smaller than 1/5 of the average indentation depth, and the upper end face and the lower end face of the sample are parallel to each other, so that the uniform distribution of the load in the indentation process is ensured.
Preferably, in the step 2, a test sample suitable for performing a nanoindentation test is screened based on the sample surface data, and the method comprises the following steps:
Judging whether one of the number of surface cracks and the number of surface stains is not zero, if any one of the number of surface cracks and the number of surface stains is not zero, performing surface treatment disqualification, and marking the sample as unsuitable for nano indentation test;
if the surface roughness and the surface glossiness are zero, acquiring sample surface definition data, wherein the sample surface definition data comprises surface definition roughness and surface definition glossiness;
Acquiring sample surface allowable deviation data, wherein the sample surface allowable deviation data comprises a roughness allowable deviation value and a glossiness allowable deviation value;
Comprehensively analyzing the sample surface data, the sample surface definition data and the sample surface allowable deviation data to obtain a surface treatment comparison value;
comparing the surface treatment comparison value with a surface treatment comparison threshold value stored in a database, and if the surface treatment comparison value is smaller than or equal to the surface treatment comparison threshold value, marking the surface treatment of the sample to be tested as a test sample capable of carrying out nano indentation test;
if the surface treatment comparison value is larger than the surface treatment comparison threshold value, the size of the sample to be tested is unqualified, the nano indentation test cannot be performed, and the polishing treatment is performed again after replacement.
Preferably, the acquiring sample surface allowable deviation data includes the steps of:
Acquiring an allowable deviation data matching set stored in a database, wherein the allowable deviation data matching set comprises allowable deviation matching data, and the allowable deviation matching data comprises environment comparison brightness and indoor dust content comparison values;
acquiring detection environment data when a sample to be screened acquires sample surface data, wherein the detection environment data comprises environment brightness and indoor dust content;
comparing the detection environment data with the allowable deviation matching data to obtain a comparison coefficient;
And the sample surface allowable deviation data corresponding to the maximum comparison coefficient and corresponding to the stored sample surface allowable deviation data in the database is the sample surface allowable deviation data corresponding to the detection environment data.
Preferably, in the step 3, when the nano indentation test is performed on the sample, the indenter randomly selects a region on the loading surface of the sample, and performs multiple indentation by using a dot matrix method to form an indentation point array, and a load-displacement curve of the indenter during each indentation is collected;
the pressure head is a diamond Berkovich pressure head;
the row spacing and the column spacing of the press-in point array are 300 mu m, and the press-in load of the press-in head is 10mN;
In step 3, in the elastic region of the curve, namely the linear part of the curve, the contact area A and the contact area A 0 when the maximum load P max are extracted;
in step 4, the contact area A is calculated, and for the Berkovich indenter, the formula is used Calculating;
Wherein h is the pressing depth of the pressing head, S is the contact stiffness, Is the elastic modulus of the pressure head, P is the load applied by the ram;
in step 5, the Suresh model calculates residual heat stress The formula of (2) is:
。
preferably, in the step 6, the analyzing the stress distribution condition inside the porcelain bushing includes the following steps:
Calculating the residual thermal stress mean value and the residual thermal stress standard deviation of all the pressed points;
normalizing the residual thermal stress values and determining stress concentration areas based on the normalized residual thermal stress values, the stress concentration areas including a high stress concentration area, a medium stress concentration area and a low stress concentration area:
Defining a region with the normalized residual thermal stress value greater than a first threshold as a high stress concentration region;
Defining a region with a normalized residual thermal stress value not greater than a first threshold but greater than a second threshold as a medium stress concentration region;
a region where the normalized residual thermal stress value is not greater than the second threshold but is greater than the third threshold is defined as a low stress concentration region.
Preferably, in the step 7, the damage mode of the porcelain bushing is evaluated according to the distribution and the magnitude of the residual heat stress, and the method specifically comprises the following steps of;
Acquiring proportion data of stress areas, wherein the proportion data of the stress areas comprises proportion of high stress areas, proportion of medium stress areas and proportion of low stress areas;
Acquiring stress region residual thermal stress standard deviation data, wherein the stress region residual thermal stress standard deviation data comprises a high stress concentration region residual thermal stress standard deviation, a medium stress concentration region residual thermal stress standard deviation and a low stress concentration region residual thermal stress standard deviation;
The method comprises the steps that a damage mode stress condition set is stored in a database, the damage mode stress condition set comprises a plurality of damage mode stress condition data, the damage mode stress condition data comprises proportion reference data of a stress area, a residual heat stress reference standard deviation of a high stress concentration area, a residual heat stress reference standard deviation of a medium stress concentration area and a residual heat stress reference standard deviation of a low stress concentration area, the proportion reference data of the stress area comprises proportion reference values of the high stress area, and proportion reference values of the medium stress area and the low stress area;
Combining the proportion data of the stress area and the residual thermal stress standard deviation data of the stress area, and recording the combined data as actual condition data of the stress area;
comparing the actual condition data of the stress area with the stress condition data of the damage mode to obtain a stress condition comparison value;
the damage pattern corresponding to the minimum stress situation comparison value stored in the database is recorded as the damage pattern of the high-voltage porcelain bushing which is broken and damaged.
Preferably, the stress situation comparison value is calculated as follows:
;
Wherein: The stress situation comparison value is obtained by comparing the actual situation data of the stress area with the stress situation data of the a-th damage mode, Stress area comparison coefficients for the a-th failure mode stress case data,The standard deviation comparison coefficient of the stress area for the stress situation data of the a-th damage mode,For storage in a databaseIs used as a weight factor of (1),For storage in a databaseA is the number of the damage mode stress condition data;
The calculation formula of the stress area comparison coefficient is as follows:
;
Wherein: For the proportion of the high stress region, For the proportion of the medium stress region,For the proportion of the low stress region,The proportion of the high stress area of the data of the stress situation of the a-th damage mode is a reference value,The proportion of the middle stress area of the stress situation data of the a-th damage mode is a reference value,A proportion reference value of a low stress area of the stress condition data of the a-th damage mode is adopted;
the calculation formula of the standard deviation comparison coefficient of the stress area is as follows:
;
Wherein: is the residual heat stress standard deviation of the high stress concentration area, Residual heat stress standard deviation is used for the middle stress concentration area,Is the residual heat stress standard deviation of the low stress concentration area,Standard deviation is determined for residual thermal stress in the high stress concentration area of the data of the stress situation of the a-th damage mode,The standard deviation is determined for residual heat stress in the middle stress concentration area of the stress situation data of the a-th damage mode,And (5) determining standard deviation for residual heat stress of the low stress concentration area of the stress condition data of the a-th damage mode.
The invention has the beneficial effects that:
the method can accurately evaluate the residual thermal stress state of the porcelain bushing on a microscopic scale by utilizing the nanoindentation technology and the Suresh model, is simple and convenient to operate, has lower requirements on sample preparation, is suitable for damaged porcelain bushing samples with various shapes and sizes, provides an effective method for residual thermal stress analysis of the high-voltage porcelain bushing which is damaged by explosion, provides scientific basis for accident analysis and prevention of the high-voltage porcelain bushing, and is beneficial to improving the safety and reliability of an electric power system related to biological energy.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
Detailed Description
The invention will now be described in further detail with reference to the drawings and to specific embodiments.
A method for detecting thermal stress of a high-voltage electric porcelain bushing based on nano indentation technology is shown in figure 1, and comprises the following steps:
And step 1, performing performance test on the nano indentation tester to determine that the error is within a normal error range.
The method comprises the steps of carrying out an indentation experiment on a standard material by using a nano indentation tester to obtain standard material test data, wherein the standard material test data comprise a test indentation recovery rate, a test unloading curve slope, a test depth drift rate and a test elastic modulus, obtaining standard material actual data, wherein the standard material actual data comprise an actual indentation recovery rate, an actual unloading curve slope, an actual depth drift rate and an actual elastic modulus, processing the standard material test data and the standard material actual data to obtain standard material test deviation data, wherein the standard material test deviation data comprise an indentation recovery rate deviation, an unloading curve slope deviation, a depth drift rate deviation and an elastic modulus deviation, and analyzing the standard material test deviation data and material test deviation allowable data stored in a database to obtain a test deviation matching value.
The test deviation matching value is obtained as follows:
;
Wherein Bp is a test deviation matching value, In order for the indentation recovery rate to deviate,In order to unload the slope deviation of the curve,In order to be a depth drift rate deviation,In order for the elastic modulus to deviate,In order for the indentation recovery rate to allow for deviation,To allow for deviations in the slope of the unloading curve,In order to allow for a deviation in the depth drift rate,In order for the modulus of elasticity to allow for variation,For storage in a databaseAnd (3) withThe weight factor of the ratio,For storage in a databaseAnd (3) withThe weight factor of the ratio,For storage in a databaseAnd (3) withThe weight factor of the ratio,For storage in a databaseAnd (3) withA weighting factor for the ratio.
The material test deviation allowable data comprises an indentation recovery rate allowable deviation, an unloading curve slope allowable deviation, a depth drift rate allowable deviation and an elastic modulus allowable deviation, wherein the test deviation matched value is compared with a test deviation matched value threshold stored in a database, if the test deviation matched value is smaller than the test deviation matched value threshold, the error of the nano indentation tester is in a normal error range, and if the test deviation matched value is not smaller than the test deviation matched value threshold, the error of the nano indentation tester is out of the normal error range.
The test indentation recovery rate is the ratio of the recovery amount of the material due to elastic deformation to the irreversible deformation generated during unloading, reflects the elasticity and plasticity behaviors of the material, can calculate the ratio of the recovery depth of an elastic part to the total indentation depth by measuring the change of the indentation depth during unloading, the slope of a test unloading curve represents the change rate of the relation between the indentation depth and the load during unloading, is related to the hardness and the rigidity of the material, and is calculated by drawing a relation curve of the depth (y axis) and the load (x axis) during unloading, the test depth drift rate is the change rate of the indentation depth of the material after loading, reflects the stability of the material after loading and unloading, records the change of the indentation depth along with time, calculates the rate of the change of the depth, and the test elastic modulus is a measure of the deformation resistance of the material, represents the rigidity of the material under the load, is a key index of the capacity of the material to bear periodical load, and the elastic modulus is calculated by combining the indentation loading and unloading curve with the relaxation ratio and other material characteristics.
The indentation recovery rate deviation refers to the absolute value of the difference between the test indentation recovery rate and the actual indentation recovery rate, the unloading curve slope deviation refers to the absolute value of the difference between the test unloading curve slope and the actual unloading curve slope, the depth drift rate deviation refers to the absolute value of the difference between the test depth drift rate and the actual depth drift rate, and the elastic modulus deviation refers to the absolute value of the difference between the test elastic modulus and the actual elastic modulus.
The standard material test is carried out on the nano indentation tester to know whether the error of the current nano indentation tester is in a normal error range or not, so that whether the current nano indentation tester is in a usable state or not is judged, whether calibration is needed or not is judged, the accuracy and the usability of data acquired in the subsequent use process are ensured, whether the nano indentation tester is in a normal working range or not can be definitely judged by detecting the standard sample by using the nano indentation tester, the potential problem of the nano indentation tester can be found and corrected in time, the guarantee can be provided for the research and development of the subsequent nano indentation tester and the safety of application, and more accurate and scientific decisions are made.
The formula can simultaneously consider various types of deviations (including indentation recovery rate, unloading curve slope, depth drift rate and elastic modulus) and corresponding allowable deviations thereof, can comprehensively reflect the measurement performance of equipment, and quantizes the deviations into a digital form, so that the result is more scientific and reliable, the risk of misjudgment is reduced, the problem of a nano indentation tester is facilitated to be found in time, accurate parameter measurement can help to evaluate the performance of materials under different conditions, the calibration and the setting of a testing instrument are improved, and the accuracy and the repeatability of the test are improved.
Of the above-mentioned settings、、、Is obtained from a database, and a history measurement is established based on history dataAnd (3) withRatio of,And (3) withRatio of,And (3) withRatio of,And (3) withRatio and test deviation matching value, establishAnd (3) withRatio of,And (3) withRatio of,And (3) withRatio of,And (3) withThe ratio and the mapping set of the weight factors corresponding to the ratio are obtained、、、。
Hereinafter, it is described that、The corresponding weight factors are obtained through the mapping set of the historical data and the weight factors established in the database, namely, the corresponding weight factors are obtained according to the current data.
The method comprises the steps of comparing standard material test deviation data with standard material test deviation matching data stored in a database to determine the closest standard material test deviation matching data, and acquiring the stored nano indentation tester fault reasons corresponding to the closest standard material test deviation matching data from the database based on the closest standard material test deviation matching data.
And comprehensively analyzing the standard material test deviation data and standard material test deviation matching data stored in the database to obtain a test comparison value, wherein the standard material test deviation matching data comprises indentation recovery rate matching deviation, unloading curve slope matching deviation, depth drift rate matching deviation and elastic modulus matching deviation, and the standard material test deviation matching data stored in the database corresponding to the maximum test comparison value is the closest standard material test deviation matching data.
The test comparison value is obtained as follows:
;
Wherein Cb is a test comparison value, In order for the indentation recovery rate to deviate,In order to unload the slope deviation of the curve,In order to be a depth drift rate deviation,In order for the elastic modulus to deviate,For the indentation recovery rate to match the deviation,In order to unload the slope of the curve to match the bias,For the depth-drift rate matching deviation,The deviations are matched for the modulus of elasticity.
According to the method, the difference between the standard material test deviation and the related deviation in the database is quantified through calculating the test comparison value, the finally obtained matching data corresponding to the maximum test comparison value is regarded as the closest standard material deviation data, the fault reason behind the matching data is combined with the current test data, the possible problem of the nano indentation tester can be clearly pointed out, and the quantified output can be directly used for evaluating the state of the nano indentation tester, so that quick response and effective management are promoted.
And 2, cutting the high-voltage ceramic sleeve which is subjected to cracking damage into a plurality of samples to be screened which are suitable for nano-indentation test under the condition that the error of the nano-indentation tester is within a normal error range, polishing the samples to be screened, acquiring sample surface data of each sample, and screening test samples which are suitable for nano-indentation test based on the sample surface data, wherein the sample surface data comprises surface roughness, surface glossiness, surface crack quantity and surface stain quantity.
In the step 2, the damaged high-voltage electric porcelain bushing is cut into a sample with the diameter smaller than phi 50mm and the height smaller than 10mm, the surface of the sample is polished and polished, the roughness of a loading surface is ensured to reach the nano level and smaller than 1/5 of the average indentation depth, and the upper end surface and the lower end surface of the sample are parallel to each other, so that the uniform distribution of the load in the indentation process is ensured.
The diameter of the test porcelain sleeve sample is smaller than phi 50mm, the height of the test porcelain sleeve sample is smaller than 10mm, the surface of the porcelain sleeve sample is polished and polished, the roughness of the loading surface is polished to the nanometer level (the roughness is smaller than 1/5 of the average indentation depth), the surface of the sample is required to be thoroughly cleaned by using a proper solvent or cleaning liquid (including deionized water, ethanol, acetone, isopropanol, detergent and the like) so as to ensure that no foreign substances interfere with the result in the test process, and the upper end face and the lower end face of the test porcelain sleeve sample are parallel to each other so as to ensure uniform distribution of load in the indentation process.
Judging whether the number of surface cracks and the number of surface stains is not zero, if any one of the number of surface cracks and the number of surface stains is not zero, performing surface treatment disqualification, marking that the sample is unsuitable for nano indentation test, if the number of surface cracks and the number of surface stains is zero, acquiring sample surface definition data, wherein the sample surface definition data comprises surface definition roughness and surface definition glossiness, acquiring sample surface allowable deviation data, wherein the sample surface allowable deviation data comprises a roughness allowable deviation value and a glossiness allowable deviation value, performing comprehensive analysis on the sample surface data and the sample surface definition data to obtain a surface treatment comparison value, performing comparison between the surface treatment comparison value and a surface treatment comparison threshold stored in a database, if the surface treatment comparison value is smaller than or equal to the surface treatment comparison threshold, performing surface treatment qualification on a sample to be tested, marking the sample to be tested as a test sample capable of nano indentation test, and if the surface treatment comparison value is larger than the surface treatment comparison threshold, performing nano indentation test on the sample to be tested, and performing polishing again after replacement.
The surface treatment comparison value is obtained as follows:
;
Wherein Bm is a surface treatment comparison value, For the surface roughness of the substrate, the surface roughness,In order to achieve a surface gloss level,A roughness is defined for the surface and,The gloss level is defined for the surface and,The deviation value is allowed for the roughness and,The deviation value is allowed for the glossiness.
The surface roughness refers to the degree of change of the microstructure of the sample surface, usually expressed as Ra (arithmetic average roughness) or Rz (ten-point height), reflects the smoothness of the sample surface, is detected by an optical roughness meter, and has another contact type, if the contact type detector is adopted, preset permissible deviation data of the sample surface is directly obtained from a database, the detection environment is not needed to be considered, and only the detection environment is considered when the optical roughness meter is adopted, the surface glossiness refers to the light reflection capability of the surface of the material, the smoothness and the smoothness of the surface are usually reflected by quantitative measurement through a gloss meter, the glossiness value is calculated by measuring the intensity of the reflected light of the surface, the high glossiness usually corresponds to smaller surface roughness, the light scattering and errors in experiments are reduced, and the uniform glossiness is beneficial to stable measurement results in nano indentation test.
The number of surface cracks refers to the total number of visible cracks on the surface of a sample, the cracks possibly affect the mechanical properties of the material, the cracks can seriously affect the strength and hardness of the material through visual inspection, microscopic inspection (optical microscope or scanning electron microscope) or image analysis technology, the number of cracks is identified to help judge the integrity and adaptability of the sample before nano indentation test, the number of surface stains refers to the number of pollutants or irregular objects on the surface, and the number of the surface stains also needs to be visually or microscopically inspected and counted, so that the stains not only affect the physical properties of the sample, but also affect the contact condition during indentation test, and increase noise or errors.
And if the sample passes the preliminary screening, then obtaining surface definition data and allowable deviation data of the sample, analyzing to obtain a surface treatment comparison value, and comparing the surface treatment comparison value with a surface treatment comparison threshold value to obtain a final judgment result so as to confirm whether the sample can perform nano indentation test or not, effectively performing quality control, ensuring that the nano indentation test is performed only on the sample meeting the conditions, timely removing the potential defect sample, ensuring the strictness of the whole test flow, avoiding the false entry of the unqualified sample and improving the reliability of the test.
The method comprises the steps of obtaining an allowable deviation data matching set stored in a database, wherein the allowable deviation data matching set comprises allowable deviation matching data, the allowable deviation matching data comprises environment comparison brightness and indoor dust content comparison values, obtaining detection environment data when samples to be screened collect sample surface data, wherein the detection environment data comprises environment brightness and indoor dust content, comparing the detection environment data with the allowable deviation matching data to obtain a comparison coefficient, and the allowable deviation matching data corresponding to the maximum comparison coefficient is the sample surface allowable deviation data corresponding to the detection environment data, wherein the allowable deviation data corresponding to the sample surface allowable deviation data stored in the database.
The comparison coefficient is obtained as follows:
;
wherein Bd is a comparison coefficient, For the brightness of the environment,For the dust content in the room,For the purpose of ambient contrast brightness,Is the indoor dust content comparison value.
The method ensures the high consistency of the test environment and the data of the sample surface, enhances the effectiveness and the systematicness of the nano indentation test, can better understand the influence of external factors on the test result by acquiring and analyzing the test environment data, and further ensures the controllability of the test condition, for example, the environment brightness can influence the observation and the optical characteristics of the sample surface, the indoor dust content can influence the accuracy of the indentation test, and the environment factors are combined with the allowable deviation data in the database, so that the optimal sample state can be obtained under the changeable environment, and the test error caused by the environment factors is reduced.
Ambient brightness refers to the intensity of the light source in the test environment, while indoor dust content refers to the amount of dust contained per cubic meter of the test environment, which is typically obtained instantaneously during sample collection by a sensor or detection instrument.
And 3, carrying out indentation experiments on the test sample by using a nano indentation instrument positioned in a normal error range, and recording a load-displacement curve of the pressure head.
And 4, analyzing the load-displacement curve, and calculating the contact area A 0 when the contact area A and the maximum load P max are extracted.
And 5, substituting the contact areas A and A 0 and the hardness H of the material determined in the experiment into a Suresh model formula to calculate the residual thermal stress of the porcelain bushing.
In the step 3, when a nanoindentation test is carried out on a sample, a region of a pressure head is randomly selected on a loading surface of the sample, a dot matrix method is adopted to carry out multiple pressing in to form a pressing-in dot array, a load-displacement curve of the pressure head during each pressing in is collected, the pressure head is a diamond Berkovich pressure head, the row spacing and the column spacing of the pressing-in dot array are 300 mu m, the pressing-in load of the pressure head is 10mN, a contact point in the load-displacement curve, namely a point with suddenly increased load, marks that the pressure head is firstly contacted with the surface of the sample, the contact area A 0 when the contact area A and the maximum load P max are extracted in an elastic region of the curve, the pressing-in dot matrix layout is 4 multiplied by 4, and the pressing-in load of the pressure head is 10mN.
In step 4, the contact area A is calculated, and for the Berkovich indenter, the formula is usedCalculating;
Wherein h is the pressing depth of the pressing head, S is the contact stiffness, Is the elastic modulus of the pressure head, P is the load applied by the ram;
in step 5, the Suresh model calculates residual heat stress The formula of (2) is:
。
wherein H can be predetermined by experimental data and material properties.
For example, the hardness H may be calculated by the following formula:
;
Substituting the expression of the contact area A to obtain:
;
And 6, analyzing the stress distribution condition inside the porcelain bushing by comparing the residual thermal stresses of different areas.
The method comprises the steps of calculating a residual thermal stress mean value and a residual thermal stress standard deviation of all pressed-in points, normalizing residual thermal stress values, determining stress concentration areas based on the normalized residual thermal stress values, wherein the stress concentration areas comprise a high stress concentration area, a medium stress concentration area and a low stress concentration area, the area with the normalized residual thermal stress value larger than a first threshold value is defined as the high stress concentration area, the area with the normalized residual thermal stress value not larger than the first threshold value but larger than a second threshold value is defined as the medium stress concentration area, and the area with the normalized residual thermal stress value not larger than the second threshold value but larger than a third threshold value is defined as the low stress concentration area.
The calculation formula of the residual thermal stress mean value is as follows:
;
Wherein: N is the total number of the pressed-in points, i is the number of the pressed-in points, ,The residual thermal stress value of the ith pressed-in point;
the calculation formula of the standard deviation of the residual thermal stress is as follows:
;
Wherein: Is the standard deviation of residual thermal stress;
the standard deviation of the residual thermal stress is a statistic for measuring the dispersion degree of a group of residual thermal stress values relative to the mean value, if the standard deviation is smaller, the residual thermal stress values of all the measuring points are relatively close to the mean value, which indicates that the stress distribution of the material in the area is relatively uniform, and if the standard deviation is larger, the residual thermal stress values of the measuring points are larger, which indicates that the stress state of the material may be uneven, which may lead to unstable performance of the material in practical application.
The distribution of stress in the porcelain bushing can be effectively evaluated through the value of the standard deviation, and if the standard deviation is large, the potential stress concentration exists in certain areas of the pipeline, which can lead to fatigue or rupture of materials.
The residual thermal stress value of each pressed point is normalized to obtain a normalized residual thermal stress value, and the calculation formula is as follows:
;
Wherein: To normalize the residual thermal stress values.
The normalized residual thermal stress value is a result of converting the residual thermal stress value of each pressed point relative to the whole average value and the standard deviation, the deviation of the residual thermal stress value of each pressed point relative to the average value is described, the normalized values have uniform dimensions, the residual thermal stress values of different measured points can be compared under the same standard, the values far from the average level, namely the extreme value or the abnormal value, can be conveniently identified, the normalized residual thermal stress value is regular, the residual thermal stress of the point is higher than the average value, the residual thermal stress of the point is lower than the average value, and the larger the absolute value is, the more obvious the deviation of the residual thermal stress of the point and the average value is.
The high stress concentration region is a set of indentation points having normalized residual thermal stress values greater than a first threshold, the medium stress concentration region is a set of indentation points having normalized residual thermal stress values not greater than the first threshold but greater than a second threshold, and the low stress concentration region is a set of indentation points having normalized residual thermal stress values not greater than the second threshold but greater than a third threshold.
The normalized residual thermal stress values can help identify data points that deviate more from the mean, potential defects or stress concentration areas can be easily found, and the normalized values can be more clearly graphically displayed to more intuitively observe the stress distribution, e.g., a histogram or thermodynamic diagram of normalized residual thermal stress values can clearly show stress concentration areas.
The quantitative analysis of stress distribution is provided by calculating the average value and standard deviation of residual thermal stress of all pressed points, the uniformity and the discrete degree of internal stress of the porcelain bushing can be effectively judged, the numerical difference between different pressed points is eliminated in the process of normalizing the residual thermal stress value, the division of stress concentration areas is more objective and reasonable, and the stress concentration areas are divided into high, medium and low stress concentration areas by setting specific thresholds, so that potential weaknesses or defects can be conveniently and rapidly positioned, and the comprehensive evaluation of the internal stress distribution of the material is realized.
And 7, evaluating the damage mode of the porcelain bushing according to the distribution and the magnitude of the residual heat stress.
The method comprises the steps of acquiring proportion data of a stress area, wherein the proportion data of the stress area comprises proportion of a high stress area, proportion of a medium stress area and proportion of a low stress area, acquiring residual thermal stress standard deviation data of the stress area, wherein the residual thermal stress standard deviation data of the stress area comprises residual thermal stress standard deviation of the high stress concentration area, residual thermal stress standard deviation of the medium stress concentration area and residual thermal stress standard deviation of the low stress concentration area, storing a damage mode stress condition set in a database, wherein the damage mode stress condition set comprises a plurality of damage mode stress condition data, the damage mode stress condition data comprises proportion reference data of the stress area, residual thermal stress reference standard deviation of the high stress concentration area, residual thermal stress reference standard deviation of the medium stress concentration area and residual thermal stress reference standard deviation of the low stress concentration area, and the proportion reference data of the stress area comprises proportion reference values of the high stress area, the medium stress area and the low stress area;
The method comprises the steps of combining proportion data of a stress area with residual thermal stress standard deviation data of the stress area, recording the proportion data and the residual thermal stress standard deviation data of the stress area as actual condition data of the stress area, comparing the actual condition data of the stress area with stress condition data of a damage mode to obtain a stress condition comparison value, and recording a damage mode of the minimum stress condition comparison value correspondingly stored in a database as a damage mode of a high-voltage porcelain bushing which is damaged by explosion.
The stress condition data of each damage mode corresponds to a damage mode in the database, the proportion of the high stress area is the ratio of the total number of the pressing points with the normalized residual thermal stress value being larger than a first threshold to the number of all the pressing points, the proportion of the middle stress area is the ratio of the total number of the pressing points with the normalized residual thermal stress value being not larger than the first threshold but larger than a second threshold to the number of all the pressing points, and the proportion of the low stress area is the ratio of the total number of the pressing points with the normalized residual thermal stress value being not larger than the second threshold but larger than a third threshold to the number of all the pressing points.
The non-uniformity of the stress distribution of the sample can be specifically evaluated by quantifying the proportion of the stress area and the standard deviation of the residual thermal stress, so that the high-risk area on the sample can be more accurately identified, the damage mode of the sample can be judged, the stress condition of the damage mode can be systematically stored, the subsequent calling and comparison can be facilitated, and the possible burst damage mode can be identified.
The calculation formula of the stress situation comparison value is as follows:
;
Wherein: The stress situation comparison value is obtained by comparing the actual situation data of the stress area with the stress situation data of the a-th damage mode, Stress area comparison coefficients for the a-th failure mode stress case data,The standard deviation comparison coefficient of the stress area for the stress situation data of the a-th damage mode,For storage in a databaseIs used as a weight factor of (1),For storage in a databaseA is the number of the damage mode stress condition data;
The stress situation comparison value represents the matching degree between the actual stress area situation and the specific damage mode, and the lower the comparison value is, the higher the similarity between the actual situation and the damage mode is.
By considering two different coefficients (stress area comparison coefficient and standard deviation comparison coefficient), the formula can comprehensively reflect the stress distribution, namely, the quantity of stress is considered, and the distribution discreteness is also concerned, so that finer analysis is provided, potential damage modes can be accurately identified, timely reaction and maintenance are promoted, the method can be adjusted and applied to different types of materials and structures, certain universality is achieved, and the method is suitable for stress analysis and damage mode identification in various engineering scenes.
The calculation formula of the stress area comparison coefficient is as follows:
;
Wherein: For the proportion of the high stress region, For the proportion of the medium stress region,For the proportion of the low stress region,The proportion of the high stress area of the data of the stress situation of the a-th damage mode is a reference value,The proportion of the middle stress area of the stress situation data of the a-th damage mode is a reference value,A proportion reference value of a low stress area of the stress condition data of the a-th damage mode is adopted;
Formula (VI) By quantifying the relative proportion difference of the high, medium and low stress areas, clear comparison basis is provided for stress distribution of different damage modes, various stress areas are comprehensively considered, no deviation to a single factor is ensured, and therefore the accuracy and reliability of analysis results are improved.
The calculation formula of the standard deviation comparison coefficient of the stress area is as follows:
;
Wherein: is the residual heat stress standard deviation of the high stress concentration area, Residual heat stress standard deviation is used for the middle stress concentration area,Is the residual heat stress standard deviation of the low stress concentration area,Standard deviation is determined for residual thermal stress in the high stress concentration area of the data of the stress situation of the a-th damage mode,The standard deviation is determined for residual heat stress in the middle stress concentration area of the stress situation data of the a-th damage mode,And (5) determining standard deviation for residual heat stress of the low stress concentration area of the stress condition data of the a-th damage mode.
Formula (VI)The design of the system provides deep evaluation on the damage mode by incorporating the standard deviation of the residual thermal stress in the high, medium and low stress concentration areas into analysis, the mode of focusing on the fluctuation amplitude and uncertainty of the stress makes the evaluation result more sensitive and accurate, the influence caused by large-range data is effectively reduced by using a natural logarithmic function, the importance of relative change is highlighted, the comparison of complex data is simplified, the standard deviation of various stress areas is comprehensively considered, the formula can feed back the damage mode from multiple dimensions, and the comprehensive basis is provided for fault diagnosis and risk evaluation.
This example is specifically illustrated by the following description:
setting standard materials as aluminum blocks, and measuring standard materials in standard material test data of a nano indentation tester 2.8 Percent,1.87 Percent,0.49 Percent,4.9 Percent,3 Percent,Is 2 percent,0.5 Percent,Is 5 percent,The total number of the components is 0.3,The total number of the components is 0.2,The total number of the components is 0.2,And (3) calculating Bp to be 0.96, wherein the test deviation matching value threshold is 1, and the error of the nano indentation tester is in a normal error range because Bp is smaller than the test deviation matching value threshold.
Samples of 40 mm diameter and 8 mm height were cut from a damaged high voltage ceramic sleeve. The sample surface was carefully sanded and polished to ensure that the roughness was on the order of nanometers (less than 10 nanometers) to meet the test requirements. The upper and lower end surfaces of the sample were machined parallel to each other to ensure even distribution of the load during indentation.
Detecting matching of environmental data and allowable deviationAt the level of 280lx,At the frequency of 6Hz,At a concentration of 300lx,5Hz, and the comparison coefficient is 0.74, and the comparison resultThe particle size of the particles is 0.1 μm,Is 5GU.
In the sample surface dataThe particle size of the particles was 0.25. Mu.m,Is in the form of 48GU,The particle size of the particles was 0.3. Mu.m,The number of the Chinese medicine is 50GU,The particle size of the particles is 0.1 μm,And (3) calculating Bm to be 0.64 and a surface treatment comparison threshold to be 1.1 for 5GU, wherein the Bm is smaller than the surface treatment comparison threshold, so that the surface treatment of the sample to be tested is qualified, and the sample is marked as a test sample capable of carrying out nano indentation test.
The nanoindenter of the diamond Berkovich indenter is used, the elastic modulus E tip=1140GPa=1140×109 Pa of the diamond Berkovich indenter is pressed in for a plurality of times on the loading surface of the sample by a dot matrix method to form a 4X 4 pressed-in dot array, each dot is applied with a load of 10 milli-newtons, the maximum pressed-in depth is 500nm, and a series of load-displacement data are collected.
;
Wherein P is the load (N) applied by the ram, h is the depth of penetration (m) of the ram, S is the contact stiffness (N/nm), and E tip is the ram elastic modulus (Pa). s=0.012N/nm, specific data table 1 shows:
Table 1 load-displacement data examples
The contact area of each of the 16 points was calculated according to the formula, and the average contact area was calculated to be 279.3nm 2. According to step 4, the hardness H can be calculated by the following formula:
;
The average hardness value of the material, namely 1.79GPa and the contact area under no load, which is determined by experiments in advance, is 300nm < 2 >, and the residual heat stress is calculated by applying a Suresh model 。
;
The average value of the residual thermal stress was 1.83X 10 7 Pa. By comparing the residual thermal stresses in the different areas, it was found that the residual thermal stresses inside the porcelain bushing were distributed relatively uniformly, but there was a slight stress concentration in some areas. In order to verify the accuracy and reliability of the method of this embodiment, the calculated residual thermal stress is compared with the results of other residual stress detection methods, such as X-ray diffraction. The comparison result shows that the residual thermal stress data obtained by the method is basically consistent with the results of other methods, thereby proving the effectiveness of the method.
Claims (6)
1. The method for detecting the thermal stress of the high-voltage electric porcelain bushing based on the nanoindentation technology is characterized by comprising the following steps of:
Step 1, performing performance test on a nano indentation tester to determine that the error is within a normal error range;
Step 2, under the condition that the error of the nano indentation tester is within the normal error range, cutting the high-voltage ceramic sleeve which is subjected to cracking damage into a plurality of samples to be screened which are suitable for nano indentation testing, polishing the samples to be screened, acquiring sample surface data of each sample, and screening test samples which are suitable for nano indentation testing based on the sample surface data, wherein the sample surface data comprise surface roughness, surface glossiness, surface crack quantity and surface stain quantity;
Step 3, using a nano indentation instrument positioned in a normal error range to carry out indentation experiments on the test sample, and recording a load-displacement curve of the pressure head;
Step 4, analyzing the load-displacement curve, and calculating and extracting a contact area A 0 when the contact area A and the maximum load P max are extracted from the load-displacement curve;
Step 5, substituting the contact areas A and A 0 determined in the experiment and the hardness H of the material into a Suresh model formula to calculate the residual thermal stress of the porcelain bushing;
step 6, analyzing stress distribution conditions in the porcelain bushing by comparing residual thermal stresses in different areas;
step 7, evaluating the damage mode of the porcelain bushing according to the distribution and the size of the residual heat stress;
In the step 3, when a nano indentation test is performed on a sample, a region of the pressure head is randomly selected on the loading surface of the sample, and is pressed in for a plurality of times by adopting a dot matrix method to form a pressed-in dot array, and a load-displacement curve of the pressure head during each pressing-in is acquired;
the pressure head is a diamond Berkovich pressure head;
the row spacing and the column spacing of the press-in point array are 300 mu m, and the press-in load of the press-in head is 10mN;
In step 3, in the elastic region of the curve, namely the linear part of the curve, the contact area A and the contact area A 0 when the maximum load P max are extracted;
in step 4, the contact area A is calculated, and for the Berkovich indenter, the formula is used Calculating;
Wherein h is the pressing depth of the pressing head, S is the contact stiffness, Is the elastic modulus of the pressure head, P is the load applied by the ram;
in step 5, the Suresh model calculates residual heat stress The formula of (2) is:
;
In the step 6, the stress distribution condition inside the porcelain bushing is analyzed, and the method comprises the following steps:
Calculating the residual thermal stress mean value and the residual thermal stress standard deviation of all the pressed points;
normalizing the residual thermal stress values and determining stress concentration areas based on the normalized residual thermal stress values, the stress concentration areas including a high stress concentration area, a medium stress concentration area and a low stress concentration area:
Defining a region with the normalized residual thermal stress value greater than a first threshold as a high stress concentration region;
Defining a region with a normalized residual thermal stress value not greater than a first threshold but greater than a second threshold as a medium stress concentration region;
Defining a region where the normalized residual thermal stress value is not greater than the second threshold but greater than the third threshold as a low stress concentration region;
in the step 7, according to the distribution and the magnitude of the residual heat stress, the damage mode of the porcelain bushing is evaluated, and the method specifically comprises the following steps of;
Acquiring proportion data of stress areas, wherein the proportion data of the stress areas comprises proportion of high stress areas, proportion of medium stress areas and proportion of low stress areas;
Acquiring stress region residual thermal stress standard deviation data, wherein the stress region residual thermal stress standard deviation data comprises a high stress concentration region residual thermal stress standard deviation, a medium stress concentration region residual thermal stress standard deviation and a low stress concentration region residual thermal stress standard deviation;
The method comprises the steps that a damage mode stress condition set is stored in a database, the damage mode stress condition set comprises a plurality of damage mode stress condition data, the damage mode stress condition data comprises proportion reference data of a stress area, a residual heat stress reference standard deviation of a high stress concentration area, a residual heat stress reference standard deviation of a medium stress concentration area and a residual heat stress reference standard deviation of a low stress concentration area, the proportion reference data of the stress area comprises proportion reference values of the high stress area, and proportion reference values of the medium stress area and the low stress area;
Combining the proportion data of the stress area and the residual thermal stress standard deviation data of the stress area, and recording the combined data as actual condition data of the stress area;
comparing the actual condition data of the stress area with the stress condition data of the damage mode to obtain a stress condition comparison value;
the damage mode of the minimum stress situation comparison value corresponding to the storage in the database is marked as the damage mode of the high-voltage porcelain bushing which is broken and damaged;
The calculation formula of the stress situation comparison value is as follows:
;
Wherein: The stress situation comparison value is obtained by comparing the actual situation data of the stress area with the stress situation data of the a-th damage mode, Stress area comparison coefficients for the a-th failure mode stress case data,The standard deviation comparison coefficient of the stress area for the stress situation data of the a-th damage mode,For storage in a databaseIs used as a weight factor of (1),For storage in a databaseA is the number of the damage mode stress condition data;
The calculation formula of the stress area comparison coefficient is as follows:
;
Wherein: For the proportion of the high stress region, For the proportion of the medium stress region,For the proportion of the low stress region,The proportion of the high stress area of the data of the stress situation of the a-th damage mode is a reference value,The proportion of the middle stress area of the stress situation data of the a-th damage mode is a reference value,A proportion reference value of a low stress area of the stress condition data of the a-th damage mode is adopted;
the calculation formula of the standard deviation comparison coefficient of the stress area is as follows:
;
Wherein: is the residual heat stress standard deviation of the high stress concentration area, Residual heat stress standard deviation is used for the middle stress concentration area,Is the residual heat stress standard deviation of the low stress concentration area,Standard deviation is determined for residual thermal stress in the high stress concentration area of the data of the stress situation of the a-th damage mode,The standard deviation is determined for residual heat stress in the middle stress concentration area of the stress situation data of the a-th damage mode,And (5) determining standard deviation for residual heat stress of the low stress concentration area of the stress condition data of the a-th damage mode.
2. The method for detecting thermal stress of high-voltage porcelain bushing based on nano indentation technology according to claim 1, wherein in the step 1, performance test is performed on a nano indentation tester, and the error is determined to be within a normal error range, comprising the following steps:
Carrying out indentation experiments on the standard material by using a nano indentation tester to obtain standard material test data, wherein the standard material test data comprises a test indentation recovery rate, a test unloading curve slope, a test depth drift rate and a test elastic modulus;
Obtaining actual data of a standard material, wherein the actual data of the standard material comprises an actual indentation recovery rate, an actual unloading curve slope, an actual depth drift rate and an actual elastic modulus;
Processing standard material test data and standard material actual data to obtain standard material test deviation data, wherein the standard material test deviation data comprises indentation recovery rate deviation, unloading curve slope deviation, depth drift rate deviation and elastic modulus deviation;
analyzing based on standard material test deviation data and material test deviation allowable data stored in a database to obtain a test deviation matching value, wherein the material test deviation allowable data comprises indentation recovery rate allowable deviation, unloading curve slope allowable deviation, depth drift rate allowable deviation and elastic modulus allowable deviation;
Comparing the test deviation matching value with a test deviation matching value threshold stored in a database, and if the test deviation matching value is smaller than the test deviation matching value threshold, positioning the error of the nano indentation tester in a normal error range;
If the test deviation matching value is not smaller than the test deviation matching value threshold, the error of the nanoindentation tester is out of the normal error range, and the standard material test deviation data is compared with the standard material test deviation matching data stored in the database to determine the closest standard material test deviation matching data;
Based on the closest standard material test deviation matching data, the stored nano indentation tester fault reasons corresponding to the closest standard material test deviation matching data are obtained from a database.
3. The method for detecting thermal stress of high-voltage porcelain bushing based on nano indentation technology according to claim 2, wherein the determining of the closest standard material test deviation matching data comprises the following steps:
Comprehensively analyzing standard material test deviation data and standard material test deviation matching data stored in a database to obtain a test comparison value, wherein the standard material test deviation matching data comprises indentation recovery rate matching deviation, unloading curve slope matching deviation, depth drift rate matching deviation and elastic modulus matching deviation;
and the standard material test deviation matching data stored in the database corresponding to the maximum test comparison value is the closest standard material test deviation matching data.
4. The method for detecting the thermal stress of the high-voltage ceramic bushing based on the nano indentation technology according to claim 1, wherein in the step 2, the damaged high-voltage ceramic bushing is cut into a sample with the diameter smaller than phi 50mm and the height smaller than 10mm, the surface of the sample is polished and polished, the roughness of a loading surface is ensured to reach the nano level and smaller than 1/5 of the average indentation depth, and the upper end face and the lower end face of the sample are parallel to each other so as to ensure the uniform distribution of the load in the indentation process.
5. The method for detecting thermal stress of high-voltage porcelain bushing based on nano indentation technology according to claim 1, wherein in the step 2, a test sample suitable for nano indentation test is screened based on sample surface data, and the method comprises the following steps:
Judging whether one of the number of surface cracks and the number of surface stains is not zero, if any one of the number of surface cracks and the number of surface stains is not zero, performing surface treatment disqualification, and marking the sample as unsuitable for nano indentation test;
if the surface roughness and the surface glossiness are zero, acquiring sample surface definition data, wherein the sample surface definition data comprises surface definition roughness and surface definition glossiness;
Acquiring sample surface allowable deviation data, wherein the sample surface allowable deviation data comprises a roughness allowable deviation value and a glossiness allowable deviation value;
Comprehensively analyzing the sample surface data, the sample surface definition data and the sample surface allowable deviation data to obtain a surface treatment comparison value;
comparing the surface treatment comparison value with a surface treatment comparison threshold value stored in a database, and if the surface treatment comparison value is smaller than or equal to the surface treatment comparison threshold value, marking the surface treatment of the sample to be tested as a test sample capable of carrying out nano indentation test;
if the surface treatment comparison value is larger than the surface treatment comparison threshold value, the size of the sample to be tested is unqualified, the nano indentation test cannot be performed, and the polishing treatment is performed again after replacement.
6. The method for detecting thermal stress of high-voltage porcelain bushing based on nano indentation technology according to claim 5, wherein the obtaining of sample surface allowable deviation data comprises the following steps:
Acquiring an allowable deviation data matching set stored in a database, wherein the allowable deviation data matching set comprises allowable deviation matching data, and the allowable deviation matching data comprises environment comparison brightness and indoor dust content comparison values;
acquiring detection environment data when a sample to be screened acquires sample surface data, wherein the detection environment data comprises environment brightness and indoor dust content;
comparing the detection environment data with the allowable deviation matching data to obtain a comparison coefficient;
And the sample surface allowable deviation data corresponding to the maximum comparison coefficient and corresponding to the stored sample surface allowable deviation data in the database is the sample surface allowable deviation data corresponding to the detection environment data.
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