Method for measuring leeb hardness and shore hardness based on double coil electromagnetic induction

Abstract

The application provides a method for measuring Leeb hardness and Shore hardness based on double-coil electromagnetic induction, which comprises the following steps: placing a to-be-measured object and a magnetized impact body on two sides of two closed coils respectively; the magnetized impact body impacts the surface of the to-be-measured object after passing through the two closed coils at a certain speed; the time interval and the speed of the magnetized impact body when passing through the two closed coils are recorded; and the Leeb hardness or the Shore hardness of the to-be-measured object is calculated. The method for measuring Leeb hardness and Shore hardness based on double-coil electromagnetic induction greatly reduces the error of detection data, and the calculated Leeb hardness and Shore hardness have high accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of measurement, in particular to a method for measuring Leeb hardness and Shore hardness based on double-coil electromagnetic induction. BACKGROUND

[0002] Leeb hardness is a new hardness measurement method proposed by Dr. LEEB of Switzerland in 1978. It is defined as follows: a specified mass impact body is impacted on the surface of a test sample under the action of elastic force at a certain speed, and the ratio of the rebound speed of the impact head at a distance of 1mm from the surface of the test sample to the impact speed is calculated to obtain a value. It is named Leeb hardness because it is named after Dr. LEEB. The impact body is impacted on the surface of a test sample under the action of elastic force at a certain speed, and the ratio of the rebound speed of the impact head at a distance of 1mm from the surface of the test sample to the impact speed is calculated to obtain a value. It is named Leeb hardness because it is named after Dr. LEEB.

[0003] At present, the method for measuring Leeb hardness of domestic manufacturers is that when the impact body approaches the closed coil, an induced voltage is generated, the voltage value U=B×L×v, according to the electromagnetic principle, when the magnetized impact body approaches the closed coil, reaches a certain position, the induced voltage reaches the maximum value, in the ideal state, at this time, the impact body is 1mm away from the material, after impacting the surface of the material, the impact body rebounds, when it is 1mm away from the surface of the material, a reverse induced voltage is generated. The ratio of the two voltages can replace the speed ratio. However, this method has disadvantages. 1. It is difficult to ensure that the voltage extreme position is exactly 1mm away from the surface of the material; 2. Due to the influence of noise, the voltage extreme measurement will deviate; 3. The circuit zero point is not easy to determine, and deviation will also occur; 4. During measurement, the voltage peak and valley will appear at different speeds, but the voltage is the same, which makes the speed measurement not accurate enough.

[0004]

[0005] In the formula: v R is the rebound speed of the impact body at a distance of 1mm from the surface of the material; v I is the impact speed of the impact body at a distance of 1mm from the surface of the material; U R is the voltage value induced when the impact body rebounds at a distance of 1mm from the surface of the material; U I is the voltage value induced when the impact body impacts at a distance of 1mm from the surface of the material; β is the inclination angle of the impact body at the 1mm position when impacting; α is the inclination angle of the impact body at the 1mm position when rebounding; n is the number of turns of the coil; L is the length of a single turn of the coil. The induced voltage is shown in FIG. 1. Figure 6

[0006] Shore hardness is a test and representation method of material hardness. The test principle is that a specified diamond impact head is dropped on the surface of a test sample from a fixed height, the impact head rebounds to a certain height, and the ratio of the rebound height to the falling height is used to calculate the Shore hardness. The height ratio is equivalent to the energy ratio.

[0007] ​The commonly used method for measuring the Shore hardness is:

[0008] The formula is transformed as

[0009] T-rebound time, ms;

[0010] g-gravitational acceleration, m / s 2 ;

[0011] H-initial height of the punch falling.

[0012] Inside the test table below the Shore hardness tester, a piezoelectric sensor made of ceramic material is installed, and the time for the Shore punch to hit the test table for the first time and hit the test table after rebounding is measured by the piezoelectric ceramic. Substituting the formula, the Shore hardness value can be obtained. This method is not a direct measurement of the energy ratio, but an indirect one. Especially for Shore hardness measurement of different hardness, the indentation depth will be different, so although the measurement error can be corrected, the random error is difficult to eliminate. For high-precision measurement, the uncertainty is relatively large.

[0013] Both Shore and Leeb hardness belong to dynamic hardness testing method, Shore examines the vertical height of the rebound of the impact body, so the Shore hardness tester must be used vertically downward, which causes great limitation in actual use; Leeb examines the rebound and impact speed of the impact body, which depends on the accuracy of speed measurement, and is prone to the defect of low Leeb and Shore hardness measurement accuracy caused by inaccurate speed detection. SUMMARY

[0014] In view of the technical problems of inconvenient use and low measurement accuracy in the Shore and Leeb hardness measurement process in the prior art, the present application provides a method for measuring Leeb hardness and Shore hardness based on double-coil electromagnetic induction,

[0015] The method for measuring Leeb hardness and Shore hardness places the material to be measured on the workbench below the impact guide pipe, the magnetized impact body is in the guide pipe, two closed coils are placed on the outer wall of the guide pipe, the magnetized impact body impacts the surface of the material to be measured after passing through the two closed coils at a certain speed, the time interval of the magnetized impact body passing through the two closed coils is recorded, the speed of the impact body is calculated, and the Leeb hardness or Shore hardness of the material to be measured is obtained;

[0016] Further, the method for measuring Leeb hardness specifically comprises the following steps:

[0017] Step 1-1, place the material to be measured below the Leeb impact guide pipe, there is a magnetized impact body in the guide pipe, and two closed coils are sleeved on the outer wall of the guide pipe; the distance between the center points of the two closed coils is s; when the center of the permanent magnet in the impact body coincides with the middle position of the two closed coils, the distance between the top ball head of the impact body and the surface of the material to be measured is 1mm;

[0018] Step 1-2, the magnetized impact body impacts the surface of the material to be measured after passing through the two closed coils at a certain speed, and the time interval of the magnetized impact body passing through the center position of the two closed coils is obtained, denoted as t1;

[0019] Step 1-3, after the magnetized impact body impacts the surface of the material to be measured, a rebound is generated, and the rebound again passes through the two closed coils, and the time interval of the rebound passing through the center position of the two closed coils is obtained, denoted as t2;

[0020] Step 1-4, the Leeb hardness of the material to be measured is calculated by formula 1;

[0021]

[0022] In formula 1,

[0023] v R is the rebound speed of the impact body at a distance of 1mm from the material surface;

[0024] v I is the impact speed of the impact body at a distance of 1mm from the material surface;

[0025] S is the distance between the center positions of the two closed coils;

[0026] t1 is the time interval of the impact passing through the center positions of the two closed coils;

[0027] t2 is the time interval of the rebound passing through the center positions of the two closed coils;

[0028] Further, the method for measuring the Shore hardness specifically comprises the following steps:

[0029] Step 2-1, the material to be measured is placed below the Shore impact guide pipe, the guide pipe has a magnetized impact body inside, and the outer wall of the guide pipe is sleeved with two closed coils; the distance between the center points of the two closed coils is s; when the center of the permanent magnet inside the impact body coincides with the middle position of the two closed coils, the distance between the top ball head of the impact body and the surface of the material to be measured is h0;

[0030] Step 2-2, the magnetized impact body impacts the surface of the material to be measured after passing through the two closed coils from top to bottom at a certain speed;

[0031] Step 2-3, after the magnetized impact body impacts the surface of the material to be measured, a rebound is generated, and the rebound again passes through the two closed coils, and the time interval of the rebound process impact body passing through the two closed coils is obtained, denoted as t2;

[0032] Step 2-4, the Shore hardness of the material to be measured is calculated by formula 2;

[0033]

[0034] In formula 2,

[0035] m is the mass of the magnetized impact body;

[0036] g is the acceleration of gravity, g = 9.80665 m / s 2 ;

[0037] h0 is the height between the two closed coil center positions and the object to be measured;

[0038] v is the speed of the magnetized impact body passing through the two closed coils;

[0039] H is the initial height between the magnetized impact body and the object to be measured;

[0040] In formula 2, v is calculated by formula 3;

[0041]

[0042] In formula 3,

[0043] s is the distance between the two closed coil center points;

[0044] t2 is the time interval for the impact body to rebound through the two closed coil center positions.

[0045] Further, the magnetized impact body is a moving object added with magnetic material; or the impact body is magnetized;

[0046] Further, the two ends of the closed coil are connected to a signal acquisition circuit;

[0047] Further, the signal acquisition circuit includes a voltage signal collector and a time timer;

[0048] Further, the two closed coils include a large coil and a small coil; the large coil is nested on the small coil, and the two coil center points are very close; or two closed coils of the same diameter are nested on the outer wall of the impact guide pipe.

[0049] Further, the distance S between the two coil center points is measured by using a vernier caliper or a Doppler laser speed measuring device;

[0050] Further, the voltage signal collector is a voltage sensor, which is used to obtain two zero voltage values generated on the signal acquisition circuit when the magnetized impact body passes through the two closed coils;

[0051] Further, the time timer is used to record the interval time between the two zero voltage values generated on the signal acquisition circuit;

[0052] In a specific embodiment of the present application, the magnetized impact body is a steel material with a permanent magnet embedded therein.

[0053] The method for measuring Leeb hardness and Shore hardness based on double-coil electromagnetic induction provided by the present application measures the time interval between the zero voltages of two adjacent closed coils with a center point close to each other, the distance between the center points of the adjacent closed coils with a center point close to each other, and the distance between the closed coil with a center point close to each other and the object to be measured, and calculates the Leeb hardness and Shore hardness of the object to be measured; by shortening the distance between the center points of the two adjacent closed coils, the error of the detection data is greatly reduced, and the calculated Leeb hardness and Shore hardness are highly accurate.

[0054] The method for measuring Leeb hardness and Shore hardness based on double-coil electromagnetic induction provided by the present application is not subject to many limitations in the use process of the existing Shore hardness tester, and has good applicability. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 is a schematic diagram of Leeb hardness measurement of a metal material of embodiment 1 of the present application;

[0056] Figure 2 is a schematic diagram of coil measurement of embodiment 1 of the present application;

[0057] Figure 3 is a coordinate diagram of the change of induced voltage with time of embodiment 1 of the present application;

[0058] Figure 4 is a schematic diagram of Shore hardness measurement of a metal material of embodiment 2 of the present application;

[0059] Figure 5 is a schematic diagram of the connection of a closed coil and a detection module of the present application;

[0060] Figure 6 is an induced voltage diagram of Leeb hardness measurement of the prior art;

[0061] In the figure:

[0062] 1, impact body; 2, impact tube; 3, closed coil; 4, metal material; 5, permanent magnet; 8, timing module; 10, displacement measurement module; 12, calculation module; 14, display module. DETAILED DESCRIPTION

[0063] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The terms "first," "second," etc., used in the specification, claims, and drawings of this invention are used to distinguish similar objects and are not intended to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, product, or apparatus comprising a series of steps S or units is not necessarily limited to those steps S or units explicitly listed, but may include other steps S and units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0064] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0065] Example 1: Leeb hardness measurement of metallic materials

[0066] like Figure 1 As shown, a permanent magnet 5 is embedded inside the impactor 1 to obtain the magnetized impactor 1 of this embodiment;

[0067] The magnetized impactor 1 and the material to be tested 4 are placed on both sides of the two closed coils 3 respectively; the two closed coils 3 are two closed coils of the same diameter that are sequentially wrapped around the outer wall of the impact guide tube; the distance between the center points of the two closed coils 3 is measured to be s = 1.6 mm by using a vernier caliper; the distance between the middle position of the two closed coils 3 and the metal material 4 is 1 mm;

[0068] like Figure 2 As shown,

[0069] The two ends of the two closed coils 3 are respectively connected to a signal acquisition circuit; the signal acquisition circuit includes a voltage sensor, which measures the voltages U1 and U2 on the connected large and small coils;

[0070] The signal acquisition circuit includes a timer to acquire and record the time interval between two zero voltage values ​​generated on the signal acquisition circuit.

[0071] The magnetized impactor 1 passes through two closed coils 3 at a speed of approximately 2 m / s and then impacts the surface of the material to be tested 4. When the magnetized impactor 1 passes through the two closed coils 3, two zero-value voltage values ​​are generated on the signal acquisition circuit. The voltage sensor measures two zero-value voltages U1 = 0 and U2 = 0. The timer records the time when the two zero-value voltages U1 = 0 and U2 = 0 respectively, and obtains the interval time t1 = 0.8 ms between the two zero-value voltage values.

[0072] After the magnetized impactor 1 impacts the surface of the object under test, it rebounds. During the rebound, it passes through two closed coils again, and the signal acquisition circuit generates two zero-value voltage values ​​at the time of rebound. The timer records the time when the zero-value voltages U1 = 0 and U2 = 0 respectively, and obtains the interval time t2 = 0.62ms between the two zero-value voltage values ​​of rebound.

[0073] Substitute the measured values ​​obtained above into the following formula 1 to calculate the Leeb hardness of the metal material 4 to be tested;

[0074]

[0075] The Leeb hardness of the tested metal material 4 was found to be 775 HLD.

[0076] In this embodiment, the voltage sensor senses voltage changes as follows: Figure 3 As shown in the diagram, the curve of the induced voltage U changing with time t resembles a sine curve.

[0077] Specifically, as the magnetized impactor 1 enters the induction range of the first closed coil from time zero to the center point of the first closed coil, the induced voltage increases from zero, reaches a sudden peak, and then decreases. When it is located at t... a At a certain moment, the voltage value drops to zero, and the time point at that moment is obtained; when the object being measured leaves the sensing range from the center point, the induced voltage decreases from zero, passes through a trough, and then rises back to zero, and the time point t at this moment is obtained. b After a period of time, it reaches t c At a certain moment, the object being measured enters the induction range of the second closed coil. Similar to the change in induced voltage when entering the first closed coil, the induced voltage drops to zero after a sudden peak. The time point t at this moment is then recorded. d The induced voltage rises to zero again after passing through a trough and a sudden change point. The time point t at this moment is then obtained. e Therefore, in this embodiment of the invention, the time node signal t obtained by the test object passing through the center point of the at least two closed coils is based on the change law of the induced voltage. a and t d Calculate the time interval t between adjacent closed loops. x :tx = t d -t a .

[0078] Example 2, Measurement of Shore Hardness of Metal Material

[0079] As Figure 4 shown,

[0080] The magnetized impact body 1 (mass 36.2g) and the metal material 4 to be measured are respectively placed on the upper and lower sides of the two closed coils 3; the two closed coils 3 include a large coil and a small coil, the large coil is sleeved on the small coil, and the center points of the two coils are very close to each other, the distance between the center points of the two closed coils 3 is measured by using a vernier caliper laser device, and the distance is s = 1.6mm; the height between the center positions of the two closed coils 3 and the metal material 4 is h0 = 1mm; the initial height H between the magnetized impact body 1 and the metal material 4 to be measured is 19mm;

[0081] The two ends of the two closed coils 3 are respectively connected to the signal acquisition circuit; the signal acquisition circuit includes a voltage sensor; the voltage sensor measures the voltages U1, U2 on the connected large and small coils;

[0082] The signal acquisition circuit includes a time timer for recording the interval time between the two zero voltage values generated on the signal acquisition circuit;

[0083] The magnetized impact body 1 passes through the two closed coils 3 at a speed of 0.6m / s from top to bottom and then impacts the surface of the metal material 4 to be measured; after the magnetized impact body 1 impacts the surface of the metal material to be measured, it rebounds, and when the magnetized impact body 1 rebounds through the two closed coils 3 from bottom to top, the signal acquisition circuit generates two zero voltage values, and the voltage sensor measures the two zero voltages U1 = 0 and U2 = 0; The time timer records the time when the two zero voltages U1 = 0 and U2 = 0, respectively, and obtains the interval time t2 = 66.7ms between the two zero voltages during rebounding;

[0084] According to formula 3, the speed of the magnetized impact body 1 during rebounding through the closed coil 3 is v = 0.245m / s;

[0085]

[0086] The measured values obtained above are substituted into formula 2 as follows to calculate the Shore hardness of the metal material 4 to be measured;

[0087]

[0088] The calculated Shore hardness of the metal material 4 to be measured is 30HSD;

[0089] The measuring steps of Example 1 and Example 2 are repeated for 10 measurement operations in parallel, and the repeatability of the calculated Leeb hardness is 3HLD, and the repeatability of the calculated Shore hardness is 1.5HSD;

[0090] Comparing the Leeb hardness tester and the Shore hardness tester produced by the companies producing Leeb hardness testers and Shore hardness testers in China at present, the method used by us is to directly measure the speed value according to the definition of Leeb hardness, and to directly measure the energy value according to the definition of Shore hardness. As shown in Comparative Example 3:

[0091] Comparative Example 3

[0092] The above-to-be-measured metal material 4 is measured for Leeb hardness and Shore hardness by using the existing method;

[0093] (1) Leeb hardness, a 5.45g impact body is impacted on the to-be-measured metal material 4 at a speed of 2.05m / s; then the impact body rebounds after contacting the to-be-measured metal material 4, and the corresponding rebound speed is 1.6m / s. At a position of 1mm on the surface of the to-be-measured metal material 4, the induced voltage values at the impact speed of 2.05m / s and the rebound speed of 1.6m / s are measured by using the measuring moving magnetic field to generate an induced voltage in the closed coil, and then the Leeb hardness value is calculated. The above operation is repeated for 10 measurement operations;

[0094] Due to the influence of noise, 1mm distance, and flat top, the measurement accuracy and measurement repeatability of the existing method are (4-8)HLD, and sometimes the measurement repeatability can even exceed 12HLD.

[0095] The method for measuring Leeb hardness in the technical scheme of the present application eliminates the errors introduced by the 1mm position, circuit noise, and flat top, and greatly improves the measurement repeatability and measurement accuracy. The measurement accuracy and measurement repeatability are less than 4HLD.

[0096] (2) Shore hardness, the Shore hardness tester currently in use does not measure the ratio of the maximum energy in the impact and rebound process, but uses an approximate formula

[0097] HSD=k×(1 / H)×(g / 8)×T^2.

[0098] The Shore hardness value is obtained. 1. The indirect method has errors, and it is not derived from the original definition of Shore hardness; 2. The measurement of time T is different due to the different hardness values of the tested piece, so the indentation depth of the punch into the material is also different, and the corresponding time is also different. When the accuracy requirement is very high, even if the correction is made, it will also bring a large error. Through actual repeatability measurement, the repeatability of the Shore hardness experimental data is generally 2.5HSD, or even higher.

[0099] The method for measuring the Shore hardness of the technical solution of the application will not affect the measurement accuracy regardless of the different indentation depths caused by the different hardness values; and the workpiece can be directly measured because the piezoelectric ceramic does not need to be placed in the test table. The measurement error and measurement repeatability are not more than 1.5HSD.

[0100] As shown above, by comparing Example 1, Example 2 and Comparative Example 3, it can be known that the measurement repeatability of the Leeb hardness of the prior art Comparative Example 3 is (4-8)HLD, and even more than 12HLD; the measurement repeatability of the Shore hardness of Comparative Example 3 is 2.5HSD; the measurement repeatability of the Leeb hardness of the measurement method of the Leeb hardness and the Shore hardness of the application Examples 1 and 2 is not higher than 3HLD, and the measurement repeatability of the Shore hardness is not more than 1.5HSD, which is much lower than the repeatability value in the measurement method of the prior art.

[0101] It is shown that the measurement method of the Leeb hardness and the Shore hardness of the application Examples greatly reduces the error of the detection data compared with the prior art, and makes the accuracy of the calculated Leeb hardness and Shore hardness high.

[0102] In other specific embodiments of the application, the magnetized impact body 1 is a magnetic core inside the impact body for magnetization treatment.

[0103] The magnetic core is a cylinder, and the magnetized magnetic core is installed in the hollow groove at the end of the impact body, so that when the center position of the magnetic core coincides with the middle position of the two closed coils, the distance between the front end ball of the impact body and the material surface is 1mm.

[0104] In the specific implementation process, the magnetic core is placed in the magnetic field formed by the coil with direct current passing through for magnetization treatment, wherein the magnetic core is a magnetizable object such as iron, cobalt, nickel and other metal objects.

[0105] In other specific embodiments of the application, the closed coil is a hollow and closed planar coil formed by conductive wires, and the shape and size enable the impact body to pass through in a predetermined direction. The closed coils are arranged in parallel and the projections of the center points in the parallel planes coincide. The closed coil is connected with a timing module, a calculation module, a displacement measurement module and a display module. Figure 5 As shown,

[0106] The timing module 8 is connected with the closed coil, and is used to obtain the time node of the measured object passing through the center point of the closed coil according to the electromagnetic induction principle. In the specific embodiments of the application, the timing module is a time timer.

[0107] The displacement measurement module 10 is used to measure the distance between the adjacent coils of the at least two closed coils.

[0108] A calculating module 12, connected with the timing module 8 and the displacement measuring module 10 respectively, is used for calculating the average speed of the measured object through the two closed coils;

[0109] A display module 14, connected with the timing module 8, the displacement measuring module 10 and the calculating module 12 respectively, is used for displaying the measurement data and the calculation data;

[0110] The displacement measuring module 10 comprises an adjustable guide rail;

[0111] The adjustable guide rail is fixedly connected with the two closed coils respectively, so that the two closed coils are kept parallel and can be axially adjusted, and the distance between the centers of the two closed coils is obtained through the displacement measuring module 10.

[0112] The other technical schemes of the present application have similar intended effects as the above.

[0113] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, which is based on the content of the specification and drawings of the present application, is also included in the patent protection scope of the present application.

Claims

1. A method for measuring the hardness of a material based on the electromagnetic induction between two coils, characterized in that, The application relates to a method for measuring the hardness of a material. The magnetized impact body is embedded with magnetic material. The two ends of the closed coil are connected with a signal acquisition circuit. The signal acquisition circuit comprises a voltage signal collector and a time timer. The method for measuring the hardness of a material comprises the following steps: Step 1-1: placing the material to be measured below a Leeb impact guide pipe, embedding a magnetized impact body in the guide pipe, and sleeving two closed coils on the outer wall of the guide pipe; the distance between the center points of the two closed coils is S; when the center of the permanent magnet in the impact body coincides with the middle position of the two closed coils, the distance between the top ball head of the impact body and the surface of the material to be measured is 1mm; Step 1-2: the magnetized impact body impacts the surface of the material to be measured after passing through the two closed coils at a certain speed, and the time interval of the magnetized impact body passing through the center positions of the two closed coils is obtained and recorded as t1; Step 1-3: after the magnetized impact body impacts the surface of the material to be measured, rebound occurs, and the rebound again passes through the two closed coils, and the time interval of the rebound passing through the two closed coils is obtained and recorded as t2; Step 1-4: the Leeb hardness of the material to be measured is calculated through formula 1; In formula 1, v1 is the impact speed of the impact body at a distance of 1mm from the surface of the material to be measured; v R V is the rebound velocity of the impactor at 1 mm from the material surface; S is the distance between the center positions of the two closed coils; t1 is the time interval of the impact body passing through the center positions of the two closed coils; t2 is the time interval of the rebound passing through the center positions of the two closed coils; The two closed coils comprise a large coil and a small coil, the large coil is sleeved on the small coil, and the center points of the two coils are very close; or two closed coils with the same diameter are sequentially sleeved on the outer wall of the impact guide pipe, and the distance S between the center points of the two coils is measured by using a vernier caliper or a Doppler laser speed measuring device; the voltage signal collector is a voltage sensor, and the voltage sensor is used to obtain two zero voltage values generated on the signal acquisition circuit when the magnetized impact body passes through the two closed coils; The time timer is used to obtain the interval time between the two zero voltage values generated on the signal acquisition circuit; The method for measuring the hardness of a material comprises the following steps: Step 2-1: placing the material to be measured below a Leeb impact guide pipe, embedding a magnetized impact body in the guide pipe, and sleeving two closed coils on the outer wall of the guide pipe; the distance between the center points of the two closed coils is S; when the center of the permanent magnet in the impact body coincides with the middle position of the two closed coils, the distance between the top ball head of the impact body and the surface of the material to be measured is h0; Step 2-2: the magnetized impact body impacts the surface of the material to be measured after passing through the two closed coils from top to bottom at a certain speed; step 2-3: after the magnetized impact body impacts the surface of the material to be measured, rebound occurs, and the rebound again passes through the two closed coils, and the time interval of the rebound passing through the two closed coils is obtained and recorded as t2; Step 2-4: the Leeb hardness of the material to be measured is calculated through formula 2; ​ In formula 2, m is the mass of the magnetized impact body; g is the acceleration due to gravity, g = 9.80665 m / s 2 ; h0 is the height between the middle position of the two closed coils and the material to be measured; v is the velocity of the magnetized impact body rebounding through the middle position of the two closed coils; and H is the initial height between the magnetized impact body and the material to be measured; In formula 2, v is calculated by formula 3; In formula 3, S is the distance between the center points of the two closed coils; and t2 is the time interval of the impact body rebounding through the center positions of the two closed coils.

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