An instrument and method for measuring the ultrasonic longitudinal wave attenuation coefficient

Abstract

This invention provides a device and method for measuring the ultrasonic longitudinal wave attenuation coefficient. The device includes: an ultrasonic detector for exciting an ultrasonic longitudinal wave probe to generate ultrasonic longitudinal waves, recording the echo amplitudes of the longitudinal waves on the reflective surfaces of a test block and a workpiece under test, and sequentially calculating the absorption attenuation coefficient, scattering attenuation coefficient, and diffusion attenuation coefficient of the workpiece under test based on the amplitudes; an ultrasonic longitudinal wave probe for fixing to the coupling surface of the test block or the workpiece under test, emitting and receiving ultrasonic longitudinal waves; and a test block designed according to the material properties of the workpiece under test and the attenuation characteristics of the ultrasonic longitudinal waves, used to receive the ultrasonic longitudinal waves and form an echo on the reflective surface. This invention eliminates the influence of diffusion attenuation in the attenuation coefficient measurement by using a pre-designed test block, sequentially calculating the absorption attenuation coefficient, scattering attenuation coefficient, and diffusion attenuation coefficient of the workpiece under test, obtaining a diffusion attenuation coefficient that matches the shape and size of the workpiece under test, and improving the accuracy of ultrasonic longitudinal wave attenuation coefficient measurement.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic longitudinal wave attenuation coefficient measurement technology, specifically to an ultrasonic longitudinal wave attenuation coefficient measurement device and its working method. Background Technology

[0002] The attenuation coefficient of ultrasound generally consists of three parts: diffusion attenuation, scattering attenuation, and absorption attenuation. Existing methods and devices generally measure the sum of these three parts, but cannot measure the attenuation coefficients of diffusion attenuation, scattering attenuation, and absorption attenuation separately.

[0003] Generally, since the diffusion attenuation coefficient is closely related to the shape and size of the workpiece being tested, the attenuation coefficient measured on the test block using existing methods is often different from the attenuation coefficient in the workpiece being tested due to the influence of changes in the diffusion attenuation coefficient. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of inaccurate measurement of ultrasonic longitudinal wave attenuation coefficient in the prior art, thereby providing a device and working method for measuring ultrasonic longitudinal wave attenuation coefficient, which can measure the diffusion attenuation coefficient, scattering attenuation coefficient and absorption attenuation coefficient of workpieces of different shapes and sizes, thereby improving the accuracy of attenuation coefficient measurement of the workpiece being tested.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] In a first aspect, the present invention provides a measuring device for the ultrasonic longitudinal wave attenuation coefficient, the system comprising: an ultrasonic detector, an ultrasonic longitudinal wave probe, and a preset number of test blocks;

[0007] The ultrasonic testing instrument is used to excite the ultrasonic longitudinal wave probe to generate an ultrasonic longitudinal wave of a preset frequency, and record the amplitude of the ultrasonic longitudinal wave echoes formed on the reflective surfaces of the test block and the workpiece under test a preset number of times. Based on the amplitude, the absorption attenuation coefficient, scattering attenuation coefficient and diffusion attenuation coefficient of the workpiece under test are calculated.

[0008] The ultrasonic longitudinal wave probe is used to be fixed on the coupling surface of the test block or the workpiece to be tested, to emit the ultrasonic longitudinal wave generated by the ultrasonic detector, and to receive the echo of the ultrasonic longitudinal wave and return it to the ultrasonic detector.

[0009] The test block is designed based on the material properties of the workpiece under test and the attenuation characteristics of ultrasonic longitudinal waves. It is used to receive the ultrasonic longitudinal waves and form an echo on the reflecting surface. The echo is used to calculate the absorption attenuation coefficient, scattering attenuation coefficient and diffusion attenuation coefficient of the workpiece under test.

[0010] The test block includes: a preset number of hemispherical test blocks or a preset number of large flat-bottomed test blocks, wherein the surface roughness, acoustic impedance, and material of the hemispherical test blocks or large flat-bottomed test blocks are the same as those of the workpiece to be tested.

[0011] The spherical radii of each hemispherical test block are the same and are set to be greater than a preset multiple of the near field area of ​​the ultrasonic longitudinal wave probe. The surface roughness is set to be less than a first preset proportion of the longitudinal wave wavelength. The average grain size of each hemispherical test block is different and is set to be less than a second preset proportion of the longitudinal wave wavelength.

[0012] The thickness of each of the large flat-bottomed test blocks is the same and is set to be greater than a preset multiple of the near-field region of the ultrasonic longitudinal wave probe. The surface roughness is set to be less than a first preset proportion of the longitudinal wave wavelength. The average grain size of each of the large flat-bottomed test blocks is different and is set to be less than a second preset proportion of the longitudinal wave wavelength.

[0013] The ultrasonic longitudinal wave attenuation coefficient measuring device provided in this invention uses pre-designed hemispherical and flat-bottomed test blocks, based on the material properties of the workpiece and the attenuation characteristics of the ultrasonic longitudinal wave, as test blocks. An ultrasonic testing instrument generates ultrasonic longitudinal waves of a preset frequency, which are then emitted to corresponding reflecting surfaces by ultrasonic longitudinal wave probes fixed to the coupling surfaces of each test block or workpiece. Echoes are formed between the coupling and reflecting surfaces, and the amplitude of the echoes is recorded a preset number of times by the ultrasonic testing instrument. The absorption attenuation coefficient, scattering attenuation coefficient, and diffusion attenuation coefficient of the workpiece are calculated based on the amplitude. This invention eliminates the influence of diffusion attenuation in attenuation coefficient measurement by using pre-designed test blocks, sequentially calculating the absorption attenuation coefficient, scattering attenuation coefficient, and diffusion attenuation coefficient of the workpiece, and obtaining a diffusion attenuation coefficient that matches the shape and size of the workpiece, thereby improving the accuracy of ultrasonic longitudinal wave attenuation coefficient measurement.

[0014] Optionally, the ultrasonic longitudinal wave probe is equipped with a magnetic attraction or clamping device to ensure that the coupling force of the ultrasonic longitudinal wave probe remains consistent when measuring different test blocks or workpieces.

[0015] The test blocks designed in this invention have the same material properties as the workpiece under test, and their shapes are regular and their sizes are relatively large. This ensures that the absorption attenuation constant and scattering attenuation constant of the test blocks and the workpiece under test are the same, and the diffusion attenuation coefficient conforms to the attenuation formula. By performing ultrasonic longitudinal wave tests on test blocks with different grain sizes, the absorption attenuation constant and scattering attenuation constant of the test blocks can be calculated, thereby obtaining the absorption attenuation coefficient and scattering attenuation coefficient of the workpiece under test. In order to obtain different equations for solving different attenuation coefficients, ultrasonic longitudinal wave measurements need to be performed on different test blocks and workpieces under test. By configuring magnetic suction or clamping devices, it is possible to ensure that the coupling force of the ultrasonic longitudinal wave probe is the same when it is fixed on different test blocks or workpieces under test, which makes the measured echo amplitude more accurate, thereby further improving the accuracy of the calculated various attenuation coefficients.

[0016] Optionally, if the workpiece to be tested does not have a reflective surface that is approximately parallel to the coupling surface, a test block with the same beam diffusion cross-sectional area as the ultrasonic longitudinal wave probe is fabricated, and the thickness, material, and surface roughness of the test block are the same as those of the workpiece to be tested.

[0017] If the workpiece tested by this invention does not have a reflective surface that is approximately parallel to the coupling surface, it cannot form the conditions for multiple reflections. Directly performing ultrasonic longitudinal wave measurement will affect the formation of echoes, resulting in inaccurate calculation of the attenuation coefficient. Therefore, a test block with the same material properties as the workpiece to be tested can be processed to replace the workpiece to be tested for measurement, which can ensure the accuracy of the attenuation coefficient measurement.

[0018] Secondly, embodiments of the present invention provide a method for operating a device for measuring the ultrasonic longitudinal wave attenuation coefficient, comprising the following steps:

[0019] Determine the coupling surface and reflecting surface of the test block. Select the plane of the hemispherical test block as the coupling surface and the curved surface of the hemispherical test block as the reflecting surface, or select the upper and lower relatively parallel surfaces of the large flat-bottomed test block as its coupling surface and reflecting surface, respectively.

[0020] An ultrasonic longitudinal wave probe of a preset frequency is fixed on the coupling surface of a preset number of test blocks. An ultrasonic detector is used to excite ultrasonic longitudinal waves and transmit them to the corresponding reflection surface of each test block through the ultrasonic longitudinal wave probe.

[0021] The ultrasonic longitudinal wave forms an echo between the coupling surface and the reflecting surface of each test block. The amplitude of the echo formed by the ultrasonic longitudinal wave on the corresponding reflecting surface of each test block for a preset number of times is recorded by the ultrasonic detector. The absorption attenuation constant and the scattering attenuation constant are obtained based on the amplitude of the echo. The absorption attenuation coefficient and the scattering attenuation coefficient of the workpiece under test are calculated based on the absorption attenuation constant and the scattering attenuation constant.

[0022] Two relatively parallel surfaces of the workpiece to be tested are selected as its coupling surface and reflecting surface, respectively. An ultrasonic longitudinal wave probe of a preset frequency is fixed on the coupling surface of the workpiece to be tested. An ultrasonic detector is used to excite ultrasonic longitudinal waves and transmit them to the reflecting surface of the workpiece to be tested through the ultrasonic longitudinal wave probe.

[0023] The ultrasonic longitudinal wave forms an echo between the coupling surface and the reflecting surface of the workpiece under test. The amplitude of the echo formed by the ultrasonic longitudinal wave on the corresponding reflecting surface of the workpiece under test for a preset number of times is recorded by the ultrasonic detector. The diffusion attenuation coefficient of the workpiece under test is calculated based on the amplitude of the echo and the absorption attenuation coefficient and the scattering attenuation coefficient.

[0024] The working method of the ultrasonic longitudinal wave attenuation coefficient measuring device provided in this invention involves designing hemispherical and flat-bottomed test blocks as test blocks based on the material properties of the workpiece under test and the attenuation characteristics of ultrasonic longitudinal waves. An ultrasonic detector generates ultrasonic longitudinal waves of a preset frequency, and an ultrasonic longitudinal wave probe fixed to the coupling surface of the test block or the workpiece under test emits the ultrasonic longitudinal waves to the corresponding reflecting surface. The ultrasonic longitudinal waves form echoes between the coupling surface and the reflecting surface, and the amplitude of the echoes is recorded by the ultrasonic detector for a preset number of times. The absorption attenuation constant and the scattering attenuation constant are obtained based on the echo amplitude of the test block, and the absorption attenuation coefficient and scattering attenuation coefficient of the workpiece under test for ultrasonic longitudinal waves are calculated based on the absorption attenuation constant and the scattering attenuation constant. Finally, the diffusion attenuation coefficient of the workpiece under test for ultrasonic longitudinal waves is calculated based on the absorption attenuation coefficient, the scattering attenuation coefficient, and the echo amplitude of the workpiece under test. This invention eliminates the influence of diffusion attenuation in attenuation coefficient measurement by using a pre-designed test block, and sequentially calculates the absorption attenuation coefficient, scattering attenuation coefficient, and diffusion attenuation coefficient of the workpiece under test, thereby obtaining a diffusion attenuation coefficient that matches the shape and size of the workpiece under test, and improving the accuracy of ultrasonic longitudinal wave attenuation coefficient measurement.

[0025] Optionally, the incident point of the ultrasonic longitudinal wave is the center of the coupling surface of the test block or the workpiece to be tested; the ultrasonic longitudinal wave passes through the center of the hemispherical test block and is emitted along the radial direction of the hemispherical test block, or is emitted perpendicular to the reflective surface of the large flat-bottomed test block.

[0026] This invention pre-designs test blocks with different average grain sizes. Ultrasonic longitudinal waves form echoes on the coupling and reflecting surfaces of the test blocks. Based on the theory of ultrasonic reflection at curved interfaces, a hemispherical test block matching the ultrasonic longitudinal wave probe is designed. The plane of the hemispherical test block serves as the coupling surface, and the curved surface serves as the reflecting surface. This ensures that multiple echoes received by the ultrasonic longitudinal wave probe are not affected by diffusion attenuation. The amplitude reduction of multiple echoes reflected from the curved surface is solely due to absorption and scattering attenuation, thus eliminating the influence of diffusion attenuation on the amplitude of multiple echoes. This provides the technical basis for obtaining the absorption and scattering attenuation coefficients. The designed large flat-bottomed test block, due to its regular shape and large size, satisfies the attenuation formula. Therefore, selecting a set of parallel opposing surfaces as the coupling and reflecting surfaces not only forms regular echoes but also provides the technical basis for obtaining the absorption and scattering attenuation coefficients.

[0027] Optionally, the diffusion attenuation of the hemispherical test block has zero effect on the attenuation coefficient measurement, and the diffusion attenuation coefficient of the large flat-bottomed test block satisfies the attenuation formula.

[0028] The pre-designed test block of this invention, due to its special shape or relatively large sound beam propagation cross section, can eliminate the influence of the diffusion attenuation coefficient in the attenuation coefficient measurement or ensure that the diffusion attenuation coefficient of the test block satisfies the attenuation formula. Specifically, the hemispherical test block, due to its hemispherical shape, ensures that the amplitude reduction of multiple echoes is only caused by absorption attenuation and scattering attenuation, simplifying the calculation process. The diffusion attenuation coefficient of the large flat-bottomed test block satisfies the attenuation formula and can be calculated using the attenuation formula; therefore, in the process of measuring the ultrasonic longitudinal wave attenuation coefficient, its diffusion attenuation coefficient can also be used as a known quantity, simplifying the calculation process.

[0029] Optionally, the number of hemispherical test blocks or large flat-bottomed test blocks is at least two.

[0030] This invention obtains the absorption attenuation constant and scattering attenuation constant by testing test blocks. Since there are two unknowns, at least one set of two linear equations must be generated during the measurement of the ultrasonic longitudinal wave attenuation coefficient to ensure that the absorption attenuation constant and scattering attenuation constant can be calculated. Therefore, during the testing process, two hemispherical test blocks or large flat-bottomed test blocks are selected. The two test blocks are identical in material properties except for the average grain size. This allows two sets of two linear equations to be generated during the measurement process. By solving the equations simultaneously, a set of two linear equations is generated, which ensures that the equations have a solution, that is, the absorption attenuation constant and scattering attenuation constant can be calculated.

[0031] Optionally, the process of recording the amplitude of the ultrasonic longitudinal wave echoes formed by the ultrasonic testing instrument at a predetermined number of times on the corresponding reflecting surfaces of each test block, obtaining the absorption attenuation constant and scattering attenuation constant based on the echo amplitude, and calculating the absorption attenuation coefficient and scattering attenuation coefficient of the workpiece under test based on the absorption attenuation constant and scattering attenuation constant includes: the ultrasonic longitudinal wave forming echoes on the reflecting surfaces of the first test block and the second test block; recording the first amplitude of the m-th echo and the second amplitude of the n-th echo formed by the ultrasonic longitudinal wave on the reflecting surface of the first test block; calculating the first attenuation coefficient of the first test block based on the first amplitude and the second amplitude, and constructing the first attenuation coefficient. The first equation relating the attenuation coefficient to the absorption attenuation constant and the scattering attenuation constant is established, wherein the attenuation coefficient is the sum of the absorption attenuation coefficient, the scattering attenuation coefficient, and the diffusion attenuation coefficient. The third amplitude of the m-th echo and the fourth amplitude of the n-th echo formed by the ultrasonic longitudinal wave on the reflecting surface of the second test block are recorded. The second attenuation coefficient of the second test block is calculated based on the third and fourth amplitudes, and a second equation relating the second attenuation coefficient to the absorption attenuation constant and the scattering attenuation constant is constructed. The first and second equations are combined to calculate the absorption attenuation constant and the scattering attenuation constant. The absorption attenuation coefficient and the scattering attenuation coefficient of the workpiece under test are calculated based on the absorption attenuation constant and the scattering attenuation constant.

[0032] This invention employs two identical ultrasonic longitudinal wave measurements, with ultrasonic longitudinal waves of the same frequency generating echoes at both the coupling and reflecting surfaces of different test blocks. By selecting a preset number of echoes, the attenuation coefficients of the two test blocks can be obtained through the echo amplitude. The attenuation coefficient is the sum of the absorption attenuation coefficient, the scattering attenuation coefficient, and the diffusion attenuation coefficient. The absorption and scattering attenuation coefficients have fixed relationships with their corresponding absorption and scattering attenuation constants, respectively. The diffusion attenuation coefficient is known or can be calculated using the attenuation formula. Therefore, two sets of relationships between the attenuation coefficient and the absorption and scattering attenuation constants can be obtained. Solving these two linear equations in two variables yields a system of linear equations in two variables. Therefore, the two constants can be solved using this system of linear equations. Substituting these constants into the fixed relationships corresponding to the workpiece under test allows for the calculation of the absorption and scattering attenuation coefficients of the workpiece under test.

[0033] Optionally, the process of recording the amplitude of the preset number of echoes formed by the ultrasonic longitudinal wave on the corresponding reflecting surface of the workpiece under test using the ultrasonic testing instrument, and calculating the diffusion attenuation coefficient of the workpiece under test based on the amplitude of the echoes and the absorption attenuation coefficient and scattering attenuation coefficient, includes: the ultrasonic longitudinal wave forming an echo on the reflecting surface of the workpiece under test; recording the fifth amplitude of the m-th echo and the sixth amplitude of the n-th echo formed by the ultrasonic longitudinal wave on the reflecting surface of the workpiece under test; calculating the third attenuation coefficient of the workpiece under test based on the fifth amplitude and the sixth amplitude; and calculating the diffusion attenuation coefficient based on the third attenuation coefficient, absorption attenuation coefficient and scattering attenuation coefficient of the workpiece under test.

[0034] This invention applies ultrasonic longitudinal waves of the same frequency to the workpiece under test. The ultrasonic longitudinal waves generate echoes at the coupling and reflecting surfaces of the workpiece. By selecting echoes of the same preset number, the total attenuation coefficient of the workpiece can be obtained from the echo amplitude. Subtracting the previously calculated absorption and scattering attenuation coefficients yields the diffusion attenuation coefficient of the workpiece. For workpieces of different shapes and sizes, since absorption and scattering attenuation are independent of the workpiece's shape and size, but diffusion attenuation is affected, the actual workpiece is used to measure its diffusion attenuation, thereby obtaining the diffusion attenuation coefficient for workpieces of different shapes and sizes and improving the accuracy of attenuation coefficient measurement. Attached Figure Description

[0035] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 A schematic diagram of the structure of an ultrasonic longitudinal wave attenuation coefficient measuring device provided in an embodiment of the present invention;

[0037] Figure 2 A schematic flowchart illustrating the working method of an ultrasonic longitudinal wave attenuation coefficient measuring device provided in an embodiment of the present invention;

[0038] Figure 3 A schematic diagram of a hemispherical test block structure for a device for measuring the ultrasonic longitudinal wave attenuation coefficient provided in an embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of a large flat-bottomed test block structure for a device for measuring the ultrasonic longitudinal wave attenuation coefficient, provided in an embodiment of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] Example 1

[0043] This invention provides a device for measuring the ultrasonic longitudinal wave attenuation coefficient, such as... Figure 1 As shown, the system includes: an ultrasonic testing instrument, an ultrasonic longitudinal wave probe, and a preset number of test blocks;

[0044] The ultrasonic testing instrument is used to excite the ultrasonic longitudinal wave probe to generate an ultrasonic longitudinal wave of a preset frequency, and record the amplitude of the echo formed by the ultrasonic longitudinal wave on the reflective surfaces of the test block and the workpiece under test for a preset number of times. Based on the amplitude, the absorption attenuation coefficient, scattering attenuation coefficient and diffusion attenuation coefficient of the workpiece under test are calculated in sequence.

[0045] Specifically, in this embodiment of the invention, the ultrasonic testing instrument has the function of accurately measuring the amplitude of each echo and has the function of gain compensation. The ultrasonic testing instrument generates and emits ultrasonic longitudinal waves by exciting an ultrasonic longitudinal wave probe fixed on the coupling surface of the test block or the workpiece under test. The emitted ultrasonic longitudinal waves form echoes through multiple reflections between the coupling surface and the reflecting surface of the test block or the workpiece under test and are received by the ultrasonic longitudinal wave probe. The ultrasonic testing instrument obtains the amplitude of the echoes of a preset number of times through the ultrasonic longitudinal wave probe, and calculates the absorption attenuation coefficient, scattering attenuation coefficient, and diffusion attenuation coefficient of the workpiece under test in sequence according to the amplitude.

[0046] The ultrasonic longitudinal wave probe is used to be fixed on the coupling surface of the test block or the workpiece to be tested, to emit the ultrasonic longitudinal wave generated by the ultrasonic detector, and to receive the echo of the ultrasonic longitudinal wave and return it to the ultrasonic detector.

[0047] Specifically, in this embodiment of the invention, a magnetic attraction or clamping device is provided around the ultrasonic longitudinal wave probe to ensure that the coupling force of the ultrasonic longitudinal wave probe remains consistent when measuring different test blocks or workpieces.

[0048] The test block is designed based on the material properties of the workpiece under test and the attenuation characteristics of ultrasonic longitudinal waves. It is used to receive the ultrasonic longitudinal waves and form an echo on the reflecting surface. The echo is used to calculate the absorption attenuation coefficient, scattering attenuation coefficient, and diffusion attenuation coefficient of the workpiece under test. The test block includes: a preset number of hemispherical test blocks or a preset number of large flat-bottomed test blocks. The surface roughness, acoustic impedance, and material of the hemispherical test blocks or large flat-bottomed test blocks are the same as those of the workpiece under test. The spherical radius of each hemispherical test block is the same and is set to be greater than a preset multiple of the near-field region of the ultrasonic longitudinal wave probe. The surface roughness is set to be less than a first preset proportion of the longitudinal wave wavelength. The average grain size of each hemispherical test block is different and is set to be less than a second preset proportion of the longitudinal wave wavelength. The thickness of each large flat-bottomed test block is the same and is set to be greater than a preset multiple of the near-field region of the ultrasonic longitudinal wave probe. The surface roughness is set to be less than a first preset proportion of the longitudinal wave wavelength. The average grain size of each large flat-bottomed test block is different and is set to be less than a second preset proportion of the longitudinal wave wavelength.

[0049] Specifically, in this embodiment of the invention, the test blocks are designed based on the material properties of the workpiece under test and the attenuation characteristics of ultrasonic longitudinal waves. The ultrasonic longitudinal waves are located within approximately twice the near-field region of the probe. The attenuation of the ultrasonic longitudinal waves emitted by the probe is mainly composed of absorption attenuation and scattering attenuation. Therefore, the spherical radius of each hemispherical test block or the thickness of the large flat-bottomed test block is set to be greater than three times the near-field region of the ultrasonic longitudinal wave probe, but this is not a limitation. Furthermore, the surface roughness is set to be less than 1 / 3 of the longitudinal wave wavelength, and the average grain size varies but is all set to be less than 1 / 10 of the longitudinal wave wavelength, but this is not a limitation.

[0050] In this embodiment of the invention, not every workpiece under test can have exactly two parallel coupling surfaces and a reflecting surface, thus creating the conditions for multiple reflections. If the workpiece under test does not have a reflecting surface that is approximately parallel to the coupling surface, a test block with the same beam diffusion cross-sectional area as the ultrasonic longitudinal wave probe is fabricated. The thickness, material, and surface roughness of the test block are the same as those of the workpiece under test. The test block is used to replace the workpiece under test for measuring the attenuation coefficient.

[0051] The ultrasonic longitudinal wave attenuation coefficient measuring device provided in this invention uses pre-designed hemispherical and flat-bottomed test blocks as test blocks, based on the material properties of the workpiece under test and the attenuation characteristics of the ultrasonic longitudinal wave. An ultrasonic detector generates ultrasonic longitudinal waves of a preset frequency, which are then emitted to corresponding reflecting surfaces by ultrasonic longitudinal wave probes fixed to the coupling surfaces of each test block or the workpiece under test. Echoes are formed between the coupling and reflecting surfaces, and the amplitude of the echoes is recorded a preset number of times by the ultrasonic detector. The absorption attenuation coefficient, scattering attenuation coefficient, and diffusion attenuation coefficient of the workpiece under test are calculated based on the amplitude. This invention eliminates the influence of diffusion attenuation in attenuation coefficient measurement by using pre-designed test blocks, sequentially calculating the absorption attenuation coefficient, scattering attenuation coefficient, and diffusion attenuation coefficient of the workpiece under test, and obtaining a diffusion attenuation coefficient that matches the shape and size of the workpiece under test, thereby improving the accuracy of ultrasonic longitudinal wave attenuation coefficient measurement.

[0052] Example 2

[0053] This invention provides a method for operating a device for measuring the ultrasonic longitudinal wave attenuation coefficient, such as... Figure 2 As shown, this method measures the attenuation coefficient based on the device provided in Example 1. Taking a hemispherical test block as an example, the steps include:

[0054] Step S1: Determine the coupling surface and reflecting surface of the test block. Select the plane of the hemispherical test block as the coupling surface and the curved surface of the hemispherical test block as the reflecting surface, or select two relatively parallel surfaces of the flat-bottomed test block as its coupling surface and reflecting surface, respectively.

[0055] Specifically, in this embodiment of the invention, a hemispherical test block is designed in advance based on the attenuation characteristics of ultrasonic longitudinal waves, so that after the ultrasonic longitudinal wave probe is coupled to the upper surface of the hemispherical test block, the emitted longitudinal waves can be reflected back and forth on the hemispherical surface. Therefore, by determining the coupling surface and the reflecting surface of the hemispherical test block, the fixed position of the ultrasonic longitudinal wave probe is determined.

[0056] Step S2: Fix the ultrasonic longitudinal wave probe of the preset frequency to the coupling surface of the preset number of test blocks respectively, and use an ultrasonic detector to excite ultrasonic longitudinal waves and transmit them to the corresponding reflection surface of each test block through the ultrasonic longitudinal wave probe.

[0057] Specifically, in this embodiment of the invention, the absorption attenuation constant and scattering attenuation constant are calculated based on the echo amplitude formed in the test block. This involves two unknowns. During the measurement of the ultrasonic longitudinal wave attenuation coefficient, at least one set of two linear equations in two variables is required to ensure the calculation of the absorption attenuation constant and scattering attenuation constant. Therefore, the number of hemispherical test blocks is set to two, but this is not a limitation; in practical applications, multiple numbers can be used, but at least two are required for subsequent attenuation constant calculations. The average grain sizes of the two hemispherical test blocks are d1 and d2, respectively, and both hemispheres are R. In this embodiment of the invention, as... Figure 3 As shown, an ultrasonic longitudinal wave probe with a frequency of f is fixed at the center of the coupling surface of a hemispherical test block 1 with an average grain size of d1 and a spherical radius of R. An ultrasonic detector is used to excite the ultrasonic longitudinal wave probe, which emits ultrasonic longitudinal waves. The ultrasonic longitudinal waves pass through the center of the hemispherical test block and are emitted along the radial direction of the hemispherical test block.

[0058] Step S3: The ultrasonic longitudinal wave forms an echo between the coupling surface and the reflecting surface of each test block. The amplitude of the echo formed by the ultrasonic longitudinal wave on the corresponding reflecting surface of each test block for a preset number of times is recorded by the ultrasonic detector. The absorption attenuation constant and the scattering attenuation constant are obtained based on the amplitude of the echo. The absorption attenuation coefficient and the scattering attenuation coefficient of the workpiece under test are calculated based on the absorption attenuation constant and the scattering attenuation constant.

[0059] Specifically, in this embodiment of the invention, the ultrasonic longitudinal wave forms echoes at the coupling surface and the reflecting surface of the hemispherical test block 1. The first amplitude A of the m echoes of the ultrasonic longitudinal wave on the hemispherical curved surface is recorded by an ultrasonic testing instrument. m The second amplitude A of the nth echo n (n>m). Based on the relationship between the attenuation coefficient and the echo amplitude, the first attenuation coefficient α1 of the hemispherical test block 1 is calculated. Simultaneously, the first attenuation coefficient and the absorption attenuation constant C are constructed. a and scattering attenuation constant C s The equation between them is given, where the attenuation coefficient is the sum of the absorption attenuation coefficient, the scattering attenuation coefficient, and the diffusion attenuation coefficient. Since the hemispherical design eliminates the effect of diffusion attenuation, the diffusion attenuation coefficient α of the hemispherical specimen... d =0, therefore the attenuation coefficient of hemispherical block 1 is: α1 = α a +α s1 The resulting equation is shown below:

[0060]

[0061] Where α1 is the first attenuation coefficient of the ultrasonic longitudinal wave on the hemispherical test block 1, α a α is the absorption attenuation coefficient. s1 C is the scattering attenuation coefficient of hemispherical specimen 1.a C is the absorption attenuation constant. s denoted as the scattering attenuation constant, f as the ultrasonic longitudinal wave frequency, d1 as the average grain size of hemispherical specimen 1, R as the spherical radius of hemispherical specimen 1, and δ as the single bottom wave reflection loss of hemispherical specimen 1.

[0062] Repeat steps S2 and S3, fixing an ultrasonic longitudinal wave probe with frequency f at the center of the coupling surface of a hemispherical specimen 2 with an average grain size of d2 and a spherical radius of R. An ultrasonic transducer is used to generate ultrasonic longitudinal waves, which are then emitted by the probe. The ultrasonic longitudinal waves form echoes at the coupling and reflecting surfaces of the hemispherical specimen 2. The amplitude B of the third echo of the m-th wave on the hemispherical surface is recorded using an ultrasonic transducer. m The fourth amplitude B of the nth echo n (n>m). Based on the relationship between the attenuation coefficient and the echo amplitude, the second attenuation coefficient α2 of the hemispherical test block 2 is calculated, and the relationship between the second attenuation coefficient and the absorption attenuation constant C is constructed. a and scattering attenuation constant C s The equations between them are as follows:

[0063]

[0064] Where α2 is the second attenuation coefficient of the ultrasonic longitudinal wave on the hemispherical test block 2, α a α is the absorption attenuation coefficient. s2 C is the scattering attenuation coefficient of hemispherical specimen 2. a C is the absorption attenuation constant. s denoted as the scattering attenuation constant, f as the ultrasonic longitudinal wave frequency, d2 as the average grain size of hemispherical specimen 2, R as the spherical radius of hemispherical specimen 2, and δ as the single bottom wave reflection loss of hemispherical specimen 2.

[0065] Combining equations (1) and (2) above, we obtain the absorption attenuation constant C. a and scattering attenuation constant C s :

[0066]

[0067]

[0068] According to α a =C a f and α s =C s f 4 d 3 Using the fixed relationship, the absorption attenuation coefficient and scattering attenuation coefficient of the workpiece under test are calculated:

[0069]

[0070]

[0071] Where, d c The average grain size of the workpiece under test.

[0072] Step S4: Select two relatively parallel surfaces of the workpiece to be tested as its coupling surface and reflecting surface, respectively, and fix the ultrasonic longitudinal wave probe of the preset frequency on the coupling surface of the workpiece to be tested. Use an ultrasonic detector to excite ultrasonic longitudinal waves and transmit them to the reflecting surface of the workpiece to be tested through the ultrasonic longitudinal wave probe.

[0073] Specifically, in this embodiment of the invention, two relatively parallel surfaces of the workpiece to be tested are selected as the coupling surface and the reflecting surface. If the workpiece to be tested does not have a reflecting surface that is approximately parallel to the coupling surface, a test workpiece with the same material properties as the workpiece to be tested is designed. An ultrasonic longitudinal wave probe with a frequency of f is fixed at the center of the coupling surface of the workpiece to be tested or the test workpiece. An ultrasonic detector is used to excite the ultrasonic longitudinal wave probe to generate ultrasonic longitudinal waves, which are then emitted and received by the ultrasonic longitudinal wave probe.

[0074] Step S5: The ultrasonic longitudinal wave forms an echo between the coupling surface and the reflecting surface of the workpiece under test. The amplitude of the echo formed by the ultrasonic longitudinal wave on the corresponding reflecting surface of the workpiece under test for a preset number of times is recorded by the ultrasonic detector. The diffusion attenuation coefficient of the workpiece under test is calculated based on the amplitude of the echo and the absorption attenuation coefficient and the scattering attenuation coefficient.

[0075] Specifically, in this embodiment of the invention, the ultrasonic longitudinal wave forms echoes at the coupling surface and the reflecting surface of the workpiece under test. The fifth amplitude C of the m-th echo of the ultrasonic longitudinal wave at the reflecting surface is recorded using an ultrasonic testing instrument. m The sixth amplitude C of the nth echo n (n>m). The third attenuation coefficient α3 of the workpiece under test is calculated based on the echo amplitude, and the diffusion attenuation coefficient is calculated based on the obtained absorption attenuation coefficient and scattering attenuation coefficient of the workpiece under test. The calculation formulas are as follows:

[0076]

[0077] α dc =α3-α ac -α sc (8)

[0078] Where H is the thickness of the workpiece to be measured, δ c This represents the single bottom wave reflection loss of the workpiece under test.

[0079] The working method of the ultrasonic longitudinal wave attenuation coefficient measuring device provided in this invention involves pre-designing a hemispherical test block based on the attenuation characteristics of ultrasonic longitudinal waves. An ultrasonic detector generates ultrasonic longitudinal waves of a preset frequency, and an ultrasonic longitudinal wave probe fixed to the coupling surface of the test block or the workpiece under test emits the ultrasonic longitudinal waves to the corresponding reflecting surface. The ultrasonic longitudinal waves form echoes between the coupling surface and the reflecting surface, and the ultrasonic detector records the amplitude of the echoes a preset number of times. Based on the echo amplitude of the test block, the absorption attenuation constant and scattering attenuation constant for the ultrasonic longitudinal waves are obtained. Then, the absorption attenuation coefficient and scattering attenuation coefficient of the workpiece under test are calculated. Finally, based on the absorption attenuation coefficient, scattering attenuation coefficient, and echo amplitude of the workpiece under test, its diffusion attenuation coefficient for the ultrasonic longitudinal waves is calculated. This invention eliminates the influence of diffusion attenuation in attenuation coefficient measurement by using a pre-designed test block, sequentially calculating the absorption attenuation coefficient, scattering attenuation coefficient, and diffusion attenuation coefficient of the workpiece under test, obtaining a diffusion attenuation coefficient that matches the shape and size of the workpiece under test, thus improving the accuracy of ultrasonic longitudinal wave attenuation coefficient measurement.

[0080] Example 3

[0081] This invention provides a method for operating a device for measuring the ultrasonic longitudinal wave attenuation coefficient. This method measures the attenuation coefficient based on the device provided in Embodiment 1. Taking a large flat-bottomed test block as an example, the steps include:

[0082] Step S1: Determine the coupling surface and reflecting surface of the test block. Select the plane of the hemispherical test block as the coupling surface and the curved surface of the hemispherical test block as the reflecting surface, or select the upper and lower relatively parallel surfaces of the large flat-bottomed test block as its coupling surface and reflecting surface, respectively.

[0083] Specifically, in this embodiment of the invention, a large flat-bottomed test block is designed in advance based on the material properties of the workpiece to be tested and the attenuation characteristics of ultrasonic longitudinal waves. This allows the emitted longitudinal waves to be reflected back and forth between the upper and lower surfaces of the large flat-bottomed test block after the ultrasonic longitudinal wave probe is coupled to the upper surface of the test block. Therefore, by determining the coupling surface and the reflecting surface of the large flat-bottomed test block, the fixed position of the ultrasonic longitudinal wave probe is determined.

[0084] Step S2: Fix the ultrasonic longitudinal wave probe of the preset frequency to the coupling surface of the preset number of test blocks respectively, and use an ultrasonic detector to excite ultrasonic longitudinal waves and transmit them to the corresponding reflection surface of each test block through the ultrasonic longitudinal wave probe.

[0085] Specifically, in this embodiment of the invention, the number of large flat-bottomed test blocks is set to two, but is not limited to this. The average grain sizes of the two large flat-bottomed test blocks are d1 and d2, respectively, and their thicknesses are both h. Two opposite sides of the large flat-bottomed test blocks are selected as their coupling surface and reflecting surface, respectively. In this embodiment of the invention, as... Figure 4As shown, an ultrasonic longitudinal wave probe with frequency f is fixed at the center of the coupling surface of a large flat-bottomed test block 1 with an average grain size of d1 and a thickness of h. An ultrasonic detector is used to excite the ultrasonic longitudinal wave probe to generate ultrasonic longitudinal waves and emit them perpendicular to the reflecting surface of the large flat-bottomed test block.

[0086] Step S3: The ultrasonic longitudinal wave forms an echo between the coupling surface and the reflecting surface of each test block. The amplitude of the echo formed by the ultrasonic longitudinal wave on the corresponding reflecting surface of each test block for a preset number of times is recorded by the ultrasonic detector. The absorption attenuation constant and the scattering attenuation constant are obtained based on the amplitude of the echo. The absorption attenuation coefficient and the scattering attenuation coefficient of the workpiece under test are calculated based on the absorption attenuation constant and the scattering attenuation constant.

[0087] Specifically, in this embodiment of the invention, the ultrasonic longitudinal wave forms echoes at the coupling surface and the reflecting surface of the large flat-bottomed test block 1. The first amplitude A of the m echoes of the ultrasonic longitudinal wave at the reflecting surface is recorded by an ultrasonic testing instrument. m The second amplitude A of the nth echo n (n>m). Based on the relationship between the attenuation coefficient and the echo amplitude, the first attenuation coefficient α1 of the large flat-bottomed test block 1 is calculated. Simultaneously, the first attenuation coefficient and the absorption attenuation constant C are constructed. a and scattering attenuation constant C s The first equation between them is given, where the attenuation coefficient is the sum of the absorption attenuation coefficient, the scattering attenuation coefficient, and the diffusion attenuation coefficient. Due to the regular shape and large size of the large flat-bottomed specimen, its diffusion attenuation coefficient α... d It conforms to the attenuation formula, as shown below:

[0088]

[0089] Therefore, the attenuation coefficient of the large flat-bottomed test block 1 is: α1=α a +α s1 +α d The resulting equation is shown below:

[0090]

[0091] Where α1 is the first attenuation coefficient of the ultrasonic longitudinal wave on the large flat-bottomed test block 1, α a α is the absorption attenuation coefficient. s1 C is the scattering attenuation coefficient of the large flat-bottomed test block 1. a C is the absorption attenuation constant. s denoted as the scattering attenuation constant, f as the ultrasonic longitudinal wave frequency, d1 as the average grain size of the large flat-bottomed specimen 1, h as the thickness of the large flat-bottomed specimen 1, and δ as the single bottom wave reflection loss of the large flat-bottomed specimen 1.

[0092] Repeat steps S2 and S3, fixing an ultrasonic longitudinal wave probe with frequency f at the center of the coupling surface of a large flat-bottomed test block 2 with an average grain size of d2 and a thickness of h. Use an ultrasonic testing instrument to excite the ultrasonic longitudinal wave probe to generate ultrasonic longitudinal waves. The ultrasonic longitudinal waves form echoes at the coupling surface and the reflecting surface of the large flat-bottomed test block 2. Record the amplitude B of the third wave of the m echoes of the ultrasonic longitudinal waves at the reflecting surface using an ultrasonic testing instrument. m The fourth amplitude B of the nth echo n (n>m). Based on the relationship between the attenuation coefficient and the echo amplitude, the second attenuation coefficient α2 of the large flat-bottomed test block 2 is calculated. Simultaneously, the second attenuation coefficient and the absorption attenuation constant C are constructed. a and scattering attenuation constant C s The equations between them are as follows:

[0093]

[0094] Where α2 is the second attenuation coefficient of the ultrasonic longitudinal wave on the large flat-bottomed test block 2, α a α is the absorption attenuation coefficient. s2 C is the scattering attenuation coefficient of the large flat-bottomed test block 2. a C is the absorption attenuation constant. s denoted as the scattering attenuation constant, f as the ultrasonic longitudinal wave frequency, d2 as the average grain size of the large flat-bottomed specimen 2, h as the thickness of the large flat-bottomed specimen 2, and δ as the single bottom wave reflection loss of the large flat-bottomed specimen 2.

[0095] Combining equations (10) and (11) above, we obtain the absorption attenuation constant and the scattering attenuation constant:

[0096]

[0097]

[0098] According to α a =C a f and α s =C s f 4 d 3 The absorption attenuation coefficient and scattering attenuation coefficient of the workpiece under test were calculated:

[0099]

[0100]

[0101] Where, d c The average grain size of the workpiece under test.

[0102] Step S4: Select two relatively parallel surfaces of the workpiece to be tested as its coupling surface and reflecting surface, respectively, and fix the ultrasonic longitudinal wave probe of the preset frequency on the coupling surface of the workpiece to be tested. Use an ultrasonic detector to excite ultrasonic longitudinal waves and transmit them to the reflecting surface of the workpiece to be tested through the ultrasonic longitudinal wave probe.

[0103] Specifically, in this embodiment of the invention, an ultrasonic longitudinal wave probe with a frequency of f is fixed at the center of the coupling surface of the workpiece to be tested, and an ultrasonic testing instrument is used to excite the ultrasonic longitudinal wave probe to generate ultrasonic longitudinal waves. If the workpiece to be tested does not have a reflecting surface that is approximately parallel to the coupling surface, the ultrasonic longitudinal wave probe is fixed on the coupling surface of the fabricated test block.

[0104] Step S5: The ultrasonic longitudinal wave forms an echo between the coupling surface and the reflecting surface of the workpiece under test. The amplitude of the echo formed by the ultrasonic longitudinal wave on the corresponding reflecting surface of the workpiece under test for a preset number of times is recorded by the ultrasonic detector. The diffusion attenuation coefficient of the workpiece under test is calculated based on the amplitude of the echo and the absorption attenuation coefficient and the scattering attenuation coefficient.

[0105] Specifically, in this embodiment of the invention, the ultrasonic longitudinal wave forms echoes at the coupling surface and the reflecting surface of the workpiece under test. The fifth amplitude C of the m-th echo of the ultrasonic longitudinal wave at the reflecting surface is recorded using an ultrasonic testing instrument. m The sixth amplitude C of the nth echo n (n>m). The third attenuation coefficient α3 of the workpiece under test is calculated based on the echo amplitude, and the diffusion attenuation coefficient is calculated based on the obtained absorption attenuation coefficient and scattering attenuation coefficient of the workpiece under test. The calculation formulas are as follows:

[0106]

[0107] α dc =α3-α ac -α sc (17)

[0108] Where H is the thickness of the workpiece to be measured, δ c This represents the single bottom wave reflection loss of the workpiece under test.

[0109] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A device for measuring the ultrasonic longitudinal wave attenuation coefficient, characterized in that, include: An ultrasonic testing instrument, an ultrasonic longitudinal wave probe, and a preset number of test blocks; The ultrasonic testing instrument is used to excite the ultrasonic longitudinal wave probe to generate an ultrasonic longitudinal wave of a preset frequency, and record the amplitude of the echo formed by the ultrasonic longitudinal wave on the reflective surfaces of the test block and the workpiece under test for a preset number of times. Based on the amplitude, the absorption attenuation coefficient, scattering attenuation coefficient and diffusion attenuation coefficient of the workpiece under test are calculated in sequence. The ultrasonic longitudinal wave probe is used to be fixed on the coupling surface of the test block or the workpiece to be tested, to emit the ultrasonic longitudinal wave generated by the ultrasonic detector, and to receive the echo of the ultrasonic longitudinal wave and return it to the ultrasonic detector. The test block is designed based on the material properties of the workpiece under test and the attenuation characteristics of ultrasonic longitudinal waves. It is used to receive the ultrasonic longitudinal waves and form an echo on the reflecting surface. The echo is used to calculate the absorption attenuation coefficient, scattering attenuation coefficient and diffusion attenuation coefficient of the workpiece under test. The test block includes: a preset number of hemispherical test blocks or a preset number of large flat-bottomed test blocks, wherein the number of hemispherical test blocks or large flat-bottomed test blocks is at least two, and the surface roughness, acoustic impedance, and material of the hemispherical test blocks or large flat-bottomed test blocks are the same as those of the workpiece to be tested. The spherical radii of each hemispherical test block are the same and are set to be greater than a preset multiple of the near field area of ​​the ultrasonic longitudinal wave probe. The surface roughness is set to be less than a first preset proportion of the longitudinal wave wavelength. The average grain size of each hemispherical test block is different and is set to be less than a second preset proportion of the longitudinal wave wavelength. The thickness of each of the large flat-bottomed test blocks is the same and is set to be greater than a preset multiple of the near-field region of the ultrasonic longitudinal wave probe. The surface roughness is set to be less than a first preset proportion of the longitudinal wave wavelength. The average grain size of each of the large flat-bottomed test blocks is different and is set to be less than a second preset proportion of the longitudinal wave wavelength.

2. The measuring device for ultrasonic longitudinal wave attenuation coefficient according to claim 1, characterized in that, The ultrasonic longitudinal wave probe is equipped with a magnetic suction or clamping device to ensure that the coupling force of the ultrasonic longitudinal wave probe remains consistent when measuring different test blocks or workpieces.

3. The measuring device for the ultrasonic longitudinal wave attenuation coefficient according to claim 1, characterized in that, If the workpiece to be tested does not have a reflective surface parallel to the coupling surface, a test block with the same beam diffusion cross-sectional area as the ultrasonic longitudinal wave probe is fabricated. The thickness, material, and surface roughness of the test block are the same as those of the workpiece to be tested.

4. A method for operating a device for measuring the ultrasonic longitudinal wave attenuation coefficient, characterized in that, Measuring the ultrasonic longitudinal wave attenuation coefficient using the device according to any one of claims 1-3, the working method comprising: Determine the coupling surface and reflecting surface of the test block. Select the plane of the hemispherical test block as the coupling surface and the curved surface of the hemispherical test block as the reflecting surface, or select the upper and lower relatively parallel surfaces of the large flat-bottomed test block as its coupling surface and reflecting surface, respectively. The number of hemispherical test blocks or large flat-bottomed test blocks shall be at least 2. An ultrasonic longitudinal wave probe of a preset frequency is fixed on the coupling surface of a preset number of test blocks. An ultrasonic detector is used to excite ultrasonic longitudinal waves and transmit them to the corresponding reflection surface of each test block through the ultrasonic longitudinal wave probe. The ultrasonic longitudinal wave forms an echo between the coupling surface and the reflecting surface of each test block. The amplitude of the echo formed by the ultrasonic longitudinal wave on the corresponding reflecting surface of each test block for a preset number of times is recorded by the ultrasonic detector. The absorption attenuation constant and the scattering attenuation constant are obtained based on the amplitude of the echo. The absorption attenuation coefficient and the scattering attenuation coefficient of the workpiece under test are calculated based on the absorption attenuation constant and the scattering attenuation constant. The process of recording the amplitude of the ultrasonic longitudinal wave echoes formed on the corresponding reflecting surfaces of each test block by the ultrasonic testing instrument for a predetermined number of times, obtaining the absorption attenuation constant and scattering attenuation constant based on the echo amplitude, and calculating the absorption attenuation coefficient and scattering attenuation coefficient of the workpiece under test based on the absorption attenuation constant and scattering attenuation constant, includes: the ultrasonic longitudinal wave forming echoes on the reflecting surfaces of the first test block and the second test block; recording the first amplitude of the m-th echo and the second amplitude of the n-th echo formed by the ultrasonic longitudinal wave on the reflecting surface of the first test block; and calculating the first attenuation coefficient of the first test block based on the first amplitude and the second amplitude. The attenuation coefficient is reduced, and a first equation is constructed between the first attenuation coefficient and the absorption attenuation constant and the scattering attenuation constant; the third amplitude of the m-th echo and the fourth amplitude of the n-th echo formed by the ultrasonic longitudinal wave on the reflecting surface of the second test block are recorded; the second attenuation coefficient of the second test block is calculated based on the third amplitude and the fourth amplitude, and a second equation is constructed between the second attenuation coefficient and the absorption attenuation constant and the scattering attenuation constant; the absorption attenuation constant and the scattering attenuation constant are calculated simultaneously by combining the first equation and the second equation; the absorption attenuation constant and the scattering attenuation constant are calculated based on the absorption attenuation constant and the scattering attenuation constant. Two relatively parallel surfaces of the workpiece to be tested are selected as its coupling surface and reflecting surface, respectively. An ultrasonic longitudinal wave probe of a preset frequency is fixed on the coupling surface of the workpiece to be tested. An ultrasonic detector is used to excite ultrasonic longitudinal waves and transmit them to the reflecting surface of the workpiece to be tested through the ultrasonic longitudinal wave probe. The ultrasonic longitudinal wave forms an echo between the coupling surface and the reflecting surface of the workpiece under test. The amplitude of the echo formed by the ultrasonic longitudinal wave on the corresponding reflecting surface of the workpiece under test for a preset number of times is recorded by the ultrasonic detector. The diffusion attenuation coefficient of the workpiece under test is calculated based on the amplitude of the echo and the absorption attenuation coefficient and the scattering attenuation coefficient. The process of recording the amplitude of a preset number of echoes formed by the ultrasonic longitudinal wave on the corresponding reflecting surface of the workpiece under test using the ultrasonic testing instrument, and calculating the diffusion attenuation coefficient of the workpiece under test based on the echo amplitude and the absorption attenuation coefficient and scattering attenuation coefficient, includes: the ultrasonic longitudinal wave forming an echo on the reflecting surface of the workpiece under test; recording the fifth amplitude of the m-th echo and the sixth amplitude of the n-th echo formed by the ultrasonic longitudinal wave on the reflecting surface of the workpiece under test; calculating the third attenuation coefficient of the workpiece under test based on the fifth amplitude and the sixth amplitude; and calculating the diffusion attenuation coefficient based on the third attenuation coefficient, absorption attenuation coefficient and scattering attenuation coefficient of the workpiece under test.

5. The operating method of the ultrasonic longitudinal wave attenuation coefficient measuring device according to claim 4, characterized in that, The incident point of the ultrasonic longitudinal wave is the center position of the coupling surface of the test block or the workpiece to be tested. The ultrasonic longitudinal wave passes through the center of the hemispherical test block and is emitted along the radial direction of the hemispherical test block, or is emitted perpendicular to the reflective surface of the large flat-bottomed test block.

6. The operating method of the ultrasonic longitudinal wave attenuation coefficient measuring device according to claim 4, characterized in that, The diffusion attenuation of the hemispherical specimen has no effect on the attenuation coefficient measurement.

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