Method for measuring hardness of electroceramic material, ultrasonic hardness meter and control system of ultrasonic hardness meter

Abstract

The invention provides an electroceramic material hardness determination method, an ultrasonic hardness tester and a control system thereof, the ultrasonic hardness tester is applied to electroceramic material hardness detection, and comprises a vibration rod, a pressure head and a resonance device, and the resonance device comprises a signal receiver, a signal emitter and a resonance controller; according to the ultrasonic hardness value, measured by the ultrasonic hardness meter, of the electroceramic material, the safety of the electroceramic material in the service state is accurately evaluated, so that the quality monitoring of the electroceramic material in the network access and operation inspection process is enhanced, and safe and stable operation of a power grid is practically and effectively guaranteed.

Description

Technical Field

[0001] The invention relates to the field of measuring the hardness of electric porcelain materials, and in particular to a method for measuring the hardness of electric porcelain materials, an ultrasonic hardness tester and a control system thereof. Background Art

[0002] Porcelain insulators are important components of power plant and substation equipment, and are an important component of mechanical connection and electrical insulation of power transmission lines; porcelain sleeves are mainly used for insulation support of power transmission and transformation equipment leads or as insulation containers. Porcelain insulators, porcelain sleeves and other electrical porcelain materials are required to have good mechanical and electrical properties.

[0003] The current methods for testing the hardness of inorganic non-metallic materials such as ceramics mainly include Vickers hardness, Knoop hardness and Mohs hardness. Both Vickers hardness and Knoop hardness use diamond indenters to load and form indentations on the surface of the sample, and then calculate the material hardness based on the test force and the indentation area. Both will not only cause plastic deformation on the material surface, but also easily produce microcracks. In addition, the detection method is suitable for laboratory testing, and has high requirements for sample preparation and surface. Mohs hardness uses the notch method to scratch a pyramid-shaped diamond drill into the material surface to measure the depth of the scratch. The depth of the scratch reflects the material hardness grade. This detection method is a qualitative method for judging the hardness grade and cannot be used to quantitatively determine the hardness of the material.

[0004] Based on the above, it is urgent to study the method for measuring the hardness of electrical porcelain to solve the above problems. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for determining the hardness of an insulator material, an ultrasonic hardness tester and a control system thereof, so as to solve the technical problem that the hardness detection equipment in the above-mentioned common technology is difficult to be applied on-site to quantitatively measure the hardness of insulator materials in substation equipment.

[0006] To achieve the above object, the present invention provides an ultrasonic hardness tester, which is used for testing the hardness of electrical porcelain materials, and includes a vibrating rod, a pressure head and a resonance device, wherein the resonance device includes a signal receiver, a signal transmitter and a resonance controller; The vibration rod is vertically arranged, and a pressure head is fixedly connected to the bottom of the vibration rod for abutting against the sample to be tested; The indenter is a regular quadrangular pyramid made of diamond material, the apex of the regular quadrangular pyramid is far away from the end of the vibration rod, and the angle between the two opposite surfaces is 136°±0.5°; The signal receiver and the signal transmitter are detachably connected to the vibration rod respectively, and the resonance controller is communicatively connected to the signal receiver and the signal transmitter, and is used to transmit a control signal to the signal transmitter, so that the signal transmitter applies longitudinal ultrasonic vibration to the vibration rod, dynamically presses the indenter into the surface of the sample to be tested with a test force, and receives the frequency change information transmitted by the signal receiver to calculate the hardness value; wherein the test force ranges from 1N to 98N, the allowable deviation is ±8%, and the repeatability is not more than 3%.

[0007] The present invention provides a method for measuring the hardness of an electric porcelain material, using the ultrasonic hardness tester as described above, comprising the steps of: S1. Using a Vickers hardness tester to measure the hardness averages of standard hardness blocks in different hardness ranges, the hardness values ​​measured by the ultrasonic hardness tester under different test forces are calibrated to the hardness averages to complete the parameter calibration of the ultrasonic hardness tester; the standard hardness block and the sample to be tested are made of the same material as the electrical ceramic material; S2. Set the test force and vibration frequency of the calibrated ultrasonic hardness tester, and establish a relationship model between the ultrasonic hardness and the change in resonant frequency based on the experimental data collected in step S1: ; In the formula, is the function symbol; S3. Measure the ultrasonic hardness value of the sample to be tested according to the relationship model between the ultrasonic hardness and the change in the resonant frequency in step S2.

[0008] Furthermore, the standard hardness block is made of electrical porcelain material, and the material of the standard hardness block includes silicon porcelain and aluminum porcelain.

[0009] Furthermore, the standard hardness block includes four hardness ranges, and the hardness ranges are as follows: ≤250HV; 250HV~500HV; 500HV~800HV; 800HV~1200HV.

[0010] Furthermore, the step S1 of using a Vickers hardness tester to measure the hardness average values ​​of standard hardness blocks in different hardness ranges, and correcting the hardness values ​​displayed by the ultrasonic hardness tester under different test forces to the hardness average values ​​includes the following steps: S11. Using a Vickers hardness tester to measure the hardness value of a first standard hardness block, the number of measuring points on the first standard hardness block is not less than 5, and the arithmetic mean of the hardness values ​​measured at all the measuring points is calculated as the hardness average value; S12. Using an ultrasonic hardness tester to measure the hardness value of a second standard hardness block, the second standard hardness block has no less than 5 measuring points, and the average ultrasonic hardness value measured by the ultrasonic hardness tester is adjusted to the hardness average value in step S11; the first standard hardness block and the second standard hardness block are made of the same material and have the same hardness; S13. Calibrate the standard hardness blocks of different hardness ranges under each test force of the ultrasonic hardness tester, collect data and complete the parameter calibration of the ultrasonic hardness tester.

[0011] Furthermore, the resonance controller includes a calculation mechanism for processing ultrasonic hardness and resonant frequency change, and the step S3 includes the steps of: S31. Fixing the test sample; S32. Contacting the pressure head with the surface of the test sample and applying a test force perpendicular to the test surface; S33. The test sample needs to be measured repeatedly at least three times, and the arithmetic mean of all measured values ​​is taken as the ultrasonic hardness value of the test sample.

[0012] Furthermore, the distance from the center of any indentation made by the indenter of the ultrasonic hardness tester or the probe of the Vickers hardness tester to the edge of the test sample or the standard hardness block should be at least 2.5 times the diagonal length of the indentation, and the distance between the centers of two adjacent indentations should be at least 3 times the diagonal length of the indentation.

[0013] Furthermore, the surface of the test sample is clean and smooth, the thickness of the test sample is not less than 5 mm, and the weight is not less than 300 g.

[0014] Furthermore, the calculation formula of the ultrasonic hardness value in step S3 is: ; In the formula, For measurement results; It is the arithmetic mean of the ultrasonic hardness values ​​during measurement; To expand uncertainty; The expanded uncertainty The calculation formula is: ; In the formula, is the coverage factor, which is a coefficient that takes into account the systematic errors that may exist in the measurement; , , , is the source of uncertainty; The uncertainty sources include: standard uncertainty of the limit deviation of the ultrasonic hardness tester ;Standard uncertainty of calibration standard hardness block ; Standard uncertainty of ultrasonic hardness tester when measuring with standard hardness block ; Standard uncertainty of sample measurement ; Based on the standard uncertainty caused by the resolution of the display used by the ultrasonic hardness tester to indicate the hardness value .

[0015] The present invention provides a control system of an ultrasonic hardness tester, which is applied to the method for measuring the hardness of an electric porcelain material as described in any one of the above, and the control system comprises: A parameter calibration module, for measuring the hardness average values ​​of standard hardness blocks in different hardness ranges using a Vickers hardness tester, correcting the hardness values ​​measured by the ultrasonic hardness tester under different test forces to the hardness average values, and completing the parameter calibration of the ultrasonic hardness tester; The data processing module is connected to the parameter calibration module in communication, and includes a relationship model between ultrasonic hardness and resonant frequency variation: , so as to measure the ultrasonic hardness according to the change of the resonant frequency of the sample to be tested; In the formula, is the Vickers hardness value of the sample measured by an ultrasonic hardness tester; is the frequency change of the sample; is the function symbol; The hardness measuring module is connected to the data processing module for measuring the ultrasonic hardness value of the sample to be tested according to the relationship model between the ultrasonic hardness and the change of the resonant frequency established by the data processing module.

[0016] The beneficial effects of the present invention are as follows: The present invention studies an ultrasonic hardness tester, the main principle of which is to use the ultrasonic contact impedance method, which is a dynamic indentation method that does not directly measure the indentation. When a vibrating rod with a specific indenter (such as a diamond regular tetrahedral pyramid indenter) embedded at the end is stimulated to perform longitudinal ultrasonic vibration, this vibration is usually generated by mechanisms such as the piezoelectric effect, and its frequency and amplitude are controlled by a signal transmitter. The indenter is pressed into the surface of the test object with a certain test force, and the longitudinal vibration of the vibrating rod will be subject to impedance, and the resonant frequency will change. The change in the resonant frequency has a certain functional relationship with the indentation surface area and the effective elastic modulus of the test system, and then the hardness value of the material can be determined by measuring the frequency change, and the obtained ultrasonic hardness value is accurate and has strong reference.

[0017] The technical solution adopted in the present invention is to apply the principle of ultrasonic contact impedance method to determine the hardness of insulator materials. The hardness and strength of insulator materials are positively correlated. The strength and rigidity of insulator materials are evaluated by testing the hardness, and their safety in service is accurately assessed, so as to strengthen the quality monitoring of insulator materials during grid access and operation and inspection, and effectively ensure the safe and stable operation of the power grid.

[0018] Compared with the prior art, the ultrasonic hardness tester provided by the present invention can be directly applied to on-site detection of electrical porcelain materials, is flexible and easy to control, has strong practicality, and measures precise and accurate values, and has certain economic benefits and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0020] Figure 1 The figure is a schematic diagram of the structure of a diamond indenter of an ultrasonic hardness tester in one embodiment of the present invention.

[0021] Figure 2 It is a working schematic diagram of the ultrasonic contact impedance method for measuring hardness in one embodiment of the present invention, wherein 1 is a vibration rod, 2 is a signal receiver, 3 is a signal transmitter, 4 is a resonance controller, 5 is a pressure head, and 6 is a sample to be tested.

[0022] Figure 3 This is a physical picture of Sample 1# and Sample 2# in Example 1 of the present invention after ultrasonic hardness testing.

[0023] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that all directional indications (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0026] In addition, in the present invention, the descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0027] Furthermore, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in the field. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0028] In order to solve the technical problems that the strength test of electrical porcelain materials in common technologies has high requirements on sample preparation and surface, can only be applied to laboratory testing, has poor practicability and cannot achieve quantitative hardness measurement, the present invention provides an ultrasonic hardness tester, including a vibrating rod, an indenter and a resonance device, wherein the resonance device includes a signal receiver, a signal transmitter and a resonance controller; like Figure 2 As shown, 1 is a vibration rod, 2 is a signal receiver, 3 is a signal transmitter, 4 is a resonance controller, 5 is a pressure head, and 6 is a sample to be tested.

[0029] The vibration rod is vertically arranged, and a pressure head is fixedly connected to the bottom of the vibration rod, and the pressure head is arranged at an end away from the vibration rod to abut against the sample to be tested; The indenter is a regular quadrangular pyramid made of diamond, and the angle between the two opposite faces of the cone top is 136°±0.5°; The signal receiver and the signal transmitter are detachably connected to the vibration rod respectively, and the resonance controller is communicatively connected to the signal receiver and the signal transmitter, and is used to transmit a control signal to the signal transmitter, so that the signal transmitter applies longitudinal ultrasonic vibration to the vibration rod, dynamically presses the indenter into the surface of the sample to be tested with a test force, and receives the frequency change information transmitted by the signal receiver to calculate the hardness value; wherein, the test force ranges from 1N to 98N, the allowable deviation is ±8%, and the repeatability is not more than 3%.

[0030] Exemplarily, the test force may range from 1N to 50N; in some specific embodiments, the test force may range from 10N to 98N; in some more specific embodiments, the test force may range from 10N to 50N.

[0031] The ultrasonic hardness tester can be equipped with a display as an output device. In addition to displaying the hardness value, it can also display the control signal transmitted by the signal transmitter and the information transmitted by the signal receiver. It can also be equipped with no display, and the resonance controller can be connected to an external display, such as a wireless connection to a mobile phone or other device, so that the hardness value can be displayed on the external display.

[0032] Exemplarily, the structural diagram of the ultrasonic hardness tester is as follows: Figure 1 shown.

[0033] The present invention provides a method for measuring the hardness of an insulator material, using the ultrasonic hardness tester as described above, and the main technical steps are as follows: first, selecting a standard hardness block, second, calibrating parameters, third, measuring the hardness of the insulator material, fourth, establishing a relationship model between ultrasonic hardness and resonant frequency variation, and fifth, evaluating the measurement uncertainty of the test result. Specifically, the steps include: S1. Use a Vickers hardness tester to measure the hardness average of a standard hardness block, and calibrate the hardness value displayed by the ultrasonic hardness tester to the hardness average; the standard hardness block and the sample to be tested are made of the same material as the electrical porcelain material; In some embodiments, the standard hardness block is made with reference to the process flow used in the production of electrical porcelain materials. The types of electrical porcelain materials such as porcelain insulators and porcelain sleeves used in power systems are mainly divided into two types: siliceous porcelain and aluminum porcelain. The standard hardness block has excellent homogeneity, structural stability and uniformity of surface hardness.

[0034] Characteristics of standard hardness blocks: ① Size requirements: thickness should not be less than 16mm, diameter should not be less than 80mm; ② The flatness of the test surface and the supporting surface of the standard block is 0.005mm / 50mm, and the parallelism is 0.010mm / 50mm, where the test surface is the surface in contact with the indenter, and the supporting surface is the opposite surface of the test surface; ③ The test surface of the standard block should not have scratches and other defects that affect the indentation measurement, the surface roughness of the test surface Ra≤50nm, and the surface roughness of the supporting surface Ra≤0.8μm; ④ After the standard block is calibrated, its thickness and mass should be marked on the side of the standard block, accurate to 10μm and 1g, or an identification mark should be made on its test surface.

[0035] In some embodiments, the standard hardness blocks should be reasonably selected, and at least two standard hardness blocks should be made from each of the following four hardness ranges: (1) ≤250 HV; (2) 250 HV to 500 HV; (3) 500 HV to 800 HV; (4) 800 HV to 1200 HV.

[0036] The application environment of Vickers hardness test is limited mainly due to the following reasons. First, it has strict requirements on the roughness, flatness and cleanliness of the sample surface. The sample surface needs to be carefully prepared and processed to ensure the accuracy and reliability of the test results. This high-demand sample preparation process can usually only be carried out in a laboratory environment. Secondly, the Vickers hardness tester is a device specially used for Vickers hardness testing. It has a complex structure and high precision requirements. This equipment is usually equipped with a sophisticated measurement system and control system to ensure the stability and accuracy of the test process. Due to the professionalism and high cost of these devices, they can usually only be configured in laboratories.

[0037] Exemplarily, the Vickers hardness tester is a desktop Vickers hardness tester that has passed the inspection and calibration.

[0038] In some embodiments, the step S1 of using a Vickers hardness tester to measure the hardness average value of a standard hardness block, and correcting the hardness value displayed by the ultrasonic hardness tester to the hardness average value comprises the steps of: S11. Use a Vickers hardness tester to measure the hardness value of a first standard hardness block, where there are no less than 5 measuring points on the first standard hardness block, and calculate the arithmetic mean of the hardness values ​​measured at all the measuring points as the hardness average value.

[0039] S12. Use an ultrasonic hardness tester to measure the hardness value of the second standard hardness block, the number of measuring points on the second standard hardness block is no less than 5, and the average ultrasonic hardness value displayed by the ultrasonic hardness tester is adjusted to the hardness average value described in step S11; the first standard hardness block and the second standard hardness block are of the same material and hardness.

[0040] The second standard hardness block may be the same standard hardness block as the first standard hardness block.

[0041] Specifically, when the ultrasonic hardness tester is set to perform multiple measurements and calculate the average value, the hardness tester will record the current hardness value after each measurement, and automatically calculate and display the average value of these measurement points after reaching the set number of measurements. This average value will be output as the final measurement result, that is, the average ultrasonic hardness value in step S12.

[0042] Exemplarily, the resonance controller may include a calculation mechanism for processing the average ultrasonic hardness value.

[0043] S13. Calibrate the standard hardness blocks of different hardness ranges under each test force of the ultrasonic hardness tester, collect data and complete the parameter calibration of the ultrasonic hardness tester, that is, repeat the above steps S11 and S12 for the standard hardness blocks of different hardness ranges under each test force.

[0044] S2. Set the test force and vibration frequency of the calibrated ultrasonic hardness tester, and establish a relationship model between the ultrasonic hardness and the change in resonant frequency based on the experimental data collected in step S1: The ultrasonic hardness depends on the test force and the surface area of ​​the indentation formed by the indenter of the ultrasonic hardness tester, and the functional relationship is: ; Wherein, HV is the Vickers hardness value measured by ultrasonic hardness tester; C is a constant; F is the test force, unit is N; A is the indentation surface area, unit: mm 2 ; The indentation surface area depends on the test force, effective elastic modulus and frequency change, so the functional relationship between the ultrasonic hardness and the resonant frequency change can be established as follows: ; In the formula, is the Vickers hardness value measured by an ultrasonic hardness tester; is a constant; is the test force, unit is N; Is the effective elastic modulus, unit N / mm 2 ; is the frequency change, unit: Hz; is the function symbol; The effective elastic modulus of the same material under the same test force is the same, so the ultrasonic hardness calculation formula of the test sample can be converted to: ; In the formula, is the Vickers hardness value of the sample measured by an ultrasonic hardness tester; The Vickers hardness value measured by the ultrasonic hardness tester for calibrating the hardness block, in HV, is a known quantity; is the frequency change of the calibration hardness block, in Hz, which is a known quantity; is the frequency change of the sample; is the function symbol; because and The parameters of the hardness block are known. Therefore, as long as the frequency change of the sample is measured, The ultrasonic hardness value of the insulator material can be obtained through the ultrasonic hardness tester data processing unit, so the relationship model between ultrasonic hardness and resonant frequency change can be simplified as follows: ; In the formula, is the function symbol.

[0045] S3. Measure the ultrasonic hardness value of the sample to be tested according to the relationship model between the ultrasonic hardness and the change in the resonant frequency in step S2.

[0046] In some embodiments, a reference standard hardness block should be used to check whether the measured value of the ultrasonic hardness tester is the calibration value. According to the type of insulator material, select a suitable probe and test force for measurement, make the indenter contact the surface of the sample, and apply the test force perpendicular to the test surface. The sample and probe should be prevented from being impacted and vibrated during the loading process.

[0047] In some embodiments, in step S3, the resonance controller includes a calculation mechanism for processing ultrasonic hardness and resonant frequency change, and the step S3 includes the steps of: S31. Fixing the test sample; S32. Contacting the pressure head with the surface of the test sample and applying a test force perpendicular to the test surface; S33. The test sample needs to be measured repeatedly at least three times, and the arithmetic mean of all measured values ​​is taken as the ultrasonic hardness value of the test sample.

[0048] Exemplarily, the detected ambient temperature may be 10-35° C., and the relative humidity should be no greater than 85%.

[0049] In some embodiments, the surface of the test sample is clean, flat and smooth and free of scale, grease, dust and other contaminants; the thickness of the test sample is not less than 5 mm and the mass is not less than 300 g.

[0050] In comparison, the Vickers hardness tester has strict requirements on the roughness, flatness and cleanliness of the sample surface. The sample surface of the Vickers hardness tester needs to be carefully prepared and processed to ensure the accuracy and reliability of the test results.

[0051] It can be seen that the effects of the present invention are as follows: On the one hand, the ultrasonic hardness tester in the present invention has low requirements for the test sample and does not require surface treatment. It can be used on-site for hardness detection of electrical porcelain materials in power plants and substation equipment. It is flexible, easy to control, and highly feasible.

[0052] On the other hand, for electrical porcelain materials, if Vickers hardness and Knoop hardness are used, most of them require a test force of 300N or more to measure. The present invention controls the test force used by the ultrasonic hardness tester to 1N~98N, and the indentation area generated on the sample surface is at least 3~100 times different, thereby avoiding damage to the sample surface as much as possible.

[0053] In addition, the main principle adopted in the present invention is to use the ultrasonic contact impedance method, which is a dynamic indentation method that does not directly measure the indentation. When the vibrating rod with a specific indenter (such as a diamond regular tetrahedral pyramid indenter) embedded at the end is stimulated to make longitudinal ultrasonic vibrations, this vibration is usually generated by mechanisms such as electrostriction, magnetostriction or piezoelectric effect, and its frequency and amplitude are controlled by a signal transmitter. The indenter is pressed into the surface of the test object with a certain test force, and the longitudinal vibration of the vibrating rod will be subject to impedance, and the resonant frequency will change. The change in resonant frequency has a certain functional relationship with the indentation surface area and the effective elastic modulus of the test system, and then the hardness value of the material can be determined by measuring the frequency change, and the obtained ultrasonic hardness value is accurate and has strong reference.

[0054] Portable hardness testers in common technology are usually designed to quickly and conveniently measure the hardness of common materials such as metals. However, insulators have unique physical and chemical properties, such as high hardness, high brittleness, and low fracture toughness. These characteristics require special testing methods and conditions for hardness testing of insulators.

[0055] Most portable hardness testers use the indentation method to measure the hardness of materials, that is, to evaluate the hardness by applying a certain pressure on the surface of the material and observing the size or shape of the indentation. However, for insulators, due to their high hardness and brittleness, cracks or damage caused during the indentation process may also have an irreversible effect on the performance of the material.

[0056] Secondly, insulators play a key role in power equipment such as substations, and their mechanical properties such as hardness are directly related to the operating safety and stability of the equipment. Therefore, the hardness test of insulators requires high accuracy and reliability. However, due to the limitations of portability and cost, portable hardness testers cannot meet the requirements of insulators in terms of test accuracy and stability.

[0057] In summary, the method for determining the hardness of insulator materials and the ultrasonic hardness tester provided in the present invention can meet the effect gaps of the existing technologies (Vickers hardness measurement method, Knoop hardness measurement method, Mohs hardness measurement method and portable hardness tester), and can be flexibly applied on-site to the precise quantitative hardness detection of insulator materials.

[0058] It should be noted that the distance from the center of any indentation made by the indenter of the ultrasonic hardness tester or the probe of the Vickers hardness tester to the edge of the test sample or the standard hardness block should be at least 2.5 times the diagonal length of the indentation, and the distance between the centers of two adjacent indentations should be at least 3 times the diagonal length of the indentation.

[0059] The edge of the test specimen may interfere with the indentation formation process, causing changes in the shape and size of the indentation. Therefore, it is stipulated that the distance from the center of any indentation to the edge of the specimen should be at least 2.5 times the length of the diagonal line of the indentation, which can ensure that the indentation formation process is not affected by the edge effect. In addition, if the distance between adjacent indentations is too close, residual stress or deformation may occur, thereby affecting the formation of subsequent indentations and the measurement of hardness values. Therefore, it is stipulated that the distance between the centers of two adjacent indentations should be at least 3 times the length of the diagonal line of the indentation, which can ensure that adjacent indentations do not interfere with each other.

[0060] There are usually two methods to evaluate the measurement uncertainty: based on the evaluation of all relevant uncertainty components that appear in direct calibration; based on indirect calibration with standard hardness blocks. These two methods cannot measure all uncertainty components. In this case, the type A standard uncertainty can be used to estimate the data analysis of the sample indentation. When combining the type A standard uncertainty and the type B standard uncertainty, it should be noted that the uncertainty components cannot be counted repeatedly. The factors affecting the measurement uncertainty of the ultrasonic hardness value test results include the calibration of the test equipment and the standard hardness block; the test conditions and operation.

[0061] Specifically, the calculation formula of the ultrasonic hardness value in step S3 is: ; In the formula, For measurement results; It is the arithmetic mean of the ultrasonic hardness values ​​during measurement; To expand uncertainty; The expanded uncertainty The calculation formula is: ; In the formula, is the coverage factor, which is a coefficient that takes into account the systematic errors that may exist in the measurement; , , , is the source of uncertainty; The uncertainty sources include: standard uncertainty of the limit deviation of the ultrasonic hardness tester ;Standard uncertainty of calibration standard hardness block ; Standard uncertainty of ultrasonic hardness tester when measuring with standard hardness block ; Standard uncertainty of sample measurement ; Standard uncertainty due to the resolution of the hardness value indicator .

[0062] The maximum allowable values ​​of the indication error and repeatability of the ultrasonic hardness tester in one embodiment of the present invention are shown in Table 1: Table 1 Maximum allowable values ​​of indication error and repeatability of ultrasonic hardness tester

[0063] The present invention also provides a control system of an ultrasonic hardness tester, which is applied to the method for measuring the hardness of an electric porcelain material as described in any one of the above, and the control system comprises: A parameter calibration module, for measuring the hardness average values ​​of standard hardness blocks in different hardness ranges using a Vickers hardness tester, correcting the hardness values ​​measured by the ultrasonic hardness tester under different test forces to the hardness average values, and completing the parameter calibration of the ultrasonic hardness tester; The data processing module is connected to the parameter calibration module in communication, and includes a relationship model between ultrasonic hardness and resonant frequency variation: , so as to measure the ultrasonic hardness according to the change of the resonant frequency of the sample to be tested; In the formula, is the Vickers hardness value of the sample measured by an ultrasonic hardness tester; is the frequency change of the sample; is the function symbol; The hardness measuring module is connected to the data processing module for measuring the ultrasonic hardness value of the sample to be tested according to the relationship model between the ultrasonic hardness and the change of the resonant frequency established by the data processing module.

[0064] For easier understanding, here is an example: Example 1 S1. Use a Vickers hardness tester to measure the hardness average value of the standard hardness block, and correct the hardness value displayed by the ultrasonic hardness tester to the hardness average value: S11. The hardness values ​​of eight standard hardness blocks were measured by a Vickers hardness tester. Each standard block was measured 6 times and the arithmetic mean was calculated as the hardness value of the standard block. The Vickers hardness values ​​of the eight standard hardness blocks were 167HV, 225HV, 354HV, 465HV, 582HV, 713HV, 852HV and 988HV.

[0065] S12. Use an ultrasonic hardness tester to measure the above eight standard hardness blocks for 6 times respectively, and adjust the average values ​​displayed by the ultrasonic hardness tester to 167HV, 225HV, 354HV, 465HV, 582HV, 713HV, 852HV and 988HV respectively.

[0066] S13. Calibrate the standard hardness blocks of different hardness ranges under each test force of the ultrasonic hardness tester, collect data and complete the parameter calibration of the ultrasonic hardness tester, that is, repeat the above steps S11 and S12 for the standard hardness blocks of different hardness ranges under each test force.

[0067] S2. Set the test force and vibration frequency of the calibrated ultrasonic hardness tester, and establish the relationship model between the ultrasonic hardness and the change in resonant frequency based on the experimental data collected in step S1 ; In the formula, is the function symbol.

[0068] S3. Measure the ultrasonic hardness value of the sample to be tested according to the relationship model between the ultrasonic hardness and the change in the resonant frequency in step S2.

[0069] Step S3 includes the steps of: The ambient temperature for the test is generally 10-35°C, and the relative humidity should not exceed 85%.

[0070] The surface of the electric porcelain material sample should be clean, flat and smooth and free of scale, grease, dust and other contaminants. The sample thickness is generally not less than 5mm and the mass is not less than 300g.

[0071] The specimen should be placed firmly on the rigid test bench to ensure that the specimen does not move during the test. Otherwise, the specimen should be fixed or rigidly supported in an appropriate manner.

[0072] Before the test, the reference standard hardness block should be used to check whether the measured value of the ultrasonic hardness tester is the calibration value. According to the type of insulator material, select the appropriate probe and test force for measurement, make the indenter contact the surface of the sample, and apply the test force perpendicular to the test surface. The sample and the probe should be protected from impact and vibration during the loading process.

[0073] During the test, the distance from the center of any indentation to the edge of the specimen should be at least 2.5 times the length of the diagonal line of the indentation, and the distance between the centers of two adjacent indentations should be at least 3 times the length of the diagonal line of the indentation.

[0074] The sample needs to be measured repeatedly for at least 3 times, and the arithmetic mean of the measured values ​​is taken as the ultrasonic hardness value of the sample.

[0075] Two insulator samples were taken on site, numbered 1# and 2#. According to the above steps, the average ultrasonic hardness of the two samples was 578HV1 and 567HV1. After ultrasonic hardness testing, the actual pictures of sample 1# and sample 2# are as follows: Figure 3 As shown, there are no obvious indentations on the surfaces of Sample 1# and Sample 2#.

[0076] Among them, 578HV1 and 567HV1 mean that the ultrasonic hardness values ​​measured under a test force of 1kgf, i.e., 10N, are 578HV and 567HV.

[0077] Example 2 Compared with comparative example 1, other experimental conditions were not changed, only the test force was adjusted from 10N to 30N. According to the above steps, the average ultrasonic hardness of samples numbered 1# and 2# was measured to be 578HV3 and 567HV3, and no obvious indentation appeared on the surface.

[0078] Comparative Example 1 The other steps in step S3 of Example 1 remain unchanged, only the ultrasonic hardness tester is replaced by a Vickers hardness tester, and the hardness values ​​of sample 1# and sample 2# are measured to be 572HV30 and 559HV30, and obvious indentations with a diameter of about 0.310 mm appear on the surface of sample 1# and sample 2#.

[0079] The above technical solutions of the present invention are only preferred embodiments of the present invention, and the patent scope of the present invention is not limited thereto. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An ultrasonic hardness tester, characterized in that: Applied to the hardness test of electric porcelain materials, including a vibrating rod, a pressing head and a resonance device, wherein the resonance device includes a signal receiver, a signal transmitter and a resonance controller; The vibration rod is arranged vertically, and a pressure head is fixedly connected to the bottom of the vibration rod for being arranged against the sample to be tested; The pressure head is a regular quadrangular pyramid made of diamond material, the apex of the regular quadrangular pyramid is far away from the end of the vibration rod, and the angle between the two opposite surfaces is 136°±0.5°; The signal receiver and the signal transmitter are detachably connected to the vibration rod respectively, and the resonance controller is communicatively connected to the signal receiver and the signal transmitter, and is used to transmit a control signal to the signal transmitter, so that the signal transmitter applies longitudinal ultrasonic vibration to the vibration rod, dynamically presses the indenter into the surface of the sample to be tested with a test force, and receives the frequency change information transmitted by the signal receiver to calculate the hardness value; wherein the test force ranges from 1N to 98N, the allowable deviation is ±8%, and the repeatability is not more than 3%.

2. A method for determining the hardness of an electrical porcelain material, characterized in that: The ultrasonic hardness tester according to claim 1 comprises the following steps: S1. Using a Vickers hardness tester to measure the hardness averages of standard hardness blocks in different hardness ranges, the hardness values ​​measured by the ultrasonic hardness tester under different test forces are calibrated to the hardness averages to complete the parameter calibration of the ultrasonic hardness tester; the standard hardness block and the sample to be tested are made of the same material as the electrical ceramic material; S2. Set the test force and vibration frequency of the calibrated ultrasonic hardness tester, and establish the relationship model between the ultrasonic hardness and the change in resonant frequency according to the experimental data collected in step S1: ; In the formula, is the function symbol; is the Vickers hardness value of the sample measured by an ultrasonic hardness tester; is the frequency change of the sample; S3. Measure the ultrasonic hardness value of the sample to be tested according to the relationship model between the ultrasonic hardness and the change in the resonant frequency in step S2.

3. The measuring method according to claim 2, characterized in that The standard hardness block is made of electric porcelain material, and the material of the standard hardness block includes silicon porcelain and aluminum porcelain.

4. The measuring method according to claim 3, characterized in that The standard hardness block includes four hardness ranges, which are as follows: ≤250HV; 250HV~500HV; 500HV~800HV; 800HV~1200HV.

5. The measuring method according to claim 2, characterized in that The step S1 of using a Vickers hardness tester to measure the hardness average values ​​of standard hardness blocks in different hardness ranges, and correcting the hardness values ​​displayed by the ultrasonic hardness tester under different test forces to the hardness average values ​​comprises the following steps: S11. Using a Vickers hardness tester to measure the hardness value of a first standard hardness block, the number of measuring points on the first standard hardness block is not less than 5, and the arithmetic mean of the hardness values ​​measured at all the measuring points is calculated as the hardness average value; S12. Using an ultrasonic hardness tester to measure the hardness value of a second standard hardness block, the second standard hardness block has no less than 5 measuring points, and the average ultrasonic hardness value measured by the ultrasonic hardness tester is adjusted to the hardness average value in step S11; the first standard hardness block and the second standard hardness block are made of the same material and have the same hardness; S13. Calibrate the standard hardness blocks of different hardness ranges under each test force of the ultrasonic hardness tester, collect data and complete the parameter calibration of the ultrasonic hardness tester.

6. The measuring method according to claim 5, characterized in that The resonance controller includes a calculation mechanism for processing ultrasonic hardness and resonant frequency change, and the step S3 includes the steps of: S31. Fixing the test sample; S32. Contacting the pressure head with the surface of the test sample and applying a test force perpendicular to the test surface; S33. The test sample needs to be measured repeatedly at least three times, and the arithmetic mean of all measured values ​​is taken as the ultrasonic hardness value of the test sample.

7. The measuring method according to claim 6, characterized in that The distance from the center of any indentation made by the indenter of the ultrasonic hardness tester or the probe of the Vickers hardness tester to the edge of the test sample or the standard hardness block should be at least 2.5 times the diagonal length of the indentation, and the distance between the centers of two adjacent indentations should be at least 3 times the diagonal length of the indentation.

8. The measuring method according to claim 2, characterized in that The surface of the test sample is clean and smooth, the thickness of the test sample is not less than 5 mm, and the weight is not less than 300 g.

9. The measuring method according to claim 2, characterized in that The calculation formula of the ultrasonic hardness value in step S3 is: ； In the formula, For measurement results; It is the arithmetic mean of the ultrasonic hardness values ​​during measurement; To expand uncertainty; The expanded uncertainty The calculation formula is: ； In the formula, is the coverage factor, which is a coefficient that takes into account the systematic errors that may exist in the measurement; , , , is the source of uncertainty; The uncertainty sources include: standard uncertainty of the limit deviation of the ultrasonic hardness tester ;Standard uncertainty of calibration standard hardness block ; Standard uncertainty of ultrasonic hardness tester when measuring with standard hardness block ; Standard uncertainty of sample measurement ; Based on the standard uncertainty caused by the resolution of the display used by the ultrasonic hardness tester to indicate the hardness value .

10. A control system for an ultrasonic hardness tester, characterized in that: The method for measuring the hardness of an electric porcelain material according to any one of claims 2 to 9, wherein the control system comprises: A parameter calibration module, for measuring the hardness average values ​​of standard hardness blocks in different hardness ranges using a Vickers hardness tester, correcting the hardness values ​​measured by the ultrasonic hardness tester under different test forces to the hardness average values, and completing the parameter calibration of the ultrasonic hardness tester; The data processing module is connected to the parameter calibration module in communication, and includes a relationship model between ultrasonic hardness and resonant frequency variation: , so as to measure the ultrasonic hardness according to the change of the resonant frequency of the sample to be tested; In the formula, is the Vickers hardness value of the sample measured by an ultrasonic hardness tester; is the frequency change of the sample; is the function symbol; The hardness measuring module is connected to the data processing module for measuring the ultrasonic hardness value of the sample to be tested according to the relationship model between the ultrasonic hardness and the change of the resonant frequency established by the data processing module.

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