Ultrasonic angle probe center frequency measuring method and device based on double-reflector measuring test block

Abstract

The invention discloses an ultrasonic angle probe center frequency measurement method and device based on a double-reflector measurement test block, and belongs to the technical field of ultrasonic detection. According to the method, a ship-shaped test block containing a ball hole and a short transverse hole is designed, and sound velocity self-calibration and consistency of reflection characteristics of the ball hole and the short transverse hole to sound beams at different angles are combined, so that the problems of measurement errors and adaptability caused by changes of sound velocity, machining precision, temperature, tissue, sound beam angles and the like in a traditional method are solved. The test block comprises a quarter arc surface, an equal-depth ball hole and a short transverse hole, material sound velocity self-calibration is achieved by measuring the one-way sound time (tc) of the arc surface, the echo height (Hb) of the ball hole and the echo height (Hs) of the short transverse hole are collected, and the center frequency is calculated based on a formula. The measuring process is simplified, and the problems that in the prior art, the measuring precision is greatly influenced by the environment, the equipment cost is high, the operation is complex, and the applicability is limited are solved.

Description

Technical Field

[0001] The invention belongs to the field of ultrasonic nondestructive testing, and in particular relates to a method and a device for measuring the center frequency of an ultrasonic angle probe based on a double-reflector measuring test block. Background Art

[0002] Ultrasonic angle probes are core components in nondestructive testing. Accurately measuring their center frequency is directly related to defect detection sensitivity, resolution, positioning accuracy, and reliability. Traditional measurement methods, such as spectrum analysis and echo pulse period analysis, extract the frequency by collecting the probe pulse echo signal, performing a Fourier transform, or measuring the echo pulse period within the instrument. However, all of the above methods have significant limitations: First, the probe's acoustic field characteristics are affected by interface reflection and material attenuation, and spectrum analysis is easily interfered by clutter, making it difficult to identify some high-frequency components; second, the measurement accuracy of the center frequency is highly dependent on the machining accuracy of the test block reflector, and the manufacturing process has high requirements; third, the directional characteristics of conventional reflectors (such as flat-bottom holes) do not match the sound beam diffusion characteristics of the angle probe. A single test block cannot adapt to the center frequency measurement of angle probes with different refraction angles, and corresponding test blocks need to be processed for angle probes with different refraction angles, which is time-consuming and labor-intensive; fourth, the measurement process requires prior knowledge of the material sound velocity parameters, and in actual working conditions, material temperature changes and tissue differences will cause sound velocity deviations, which in turn affect the frequency calculation accuracy; fifth, the spectrum analysis method relies on high-precision spectrum analysis equipment and professional debugging, which is complicated to operate and easily affected by signal noise and probe damping characteristics, resulting in poor repeatability; sixth, although the echo pulse period analysis method is simple to operate, it requires an ultrasonic flaw detector with a function to measure the probe echo period, which places high demands on the equipment.

[0003] In response to the above technical bottlenecks, there is an urgent need to develop an ultrasonic oblique probe frequency detection method that integrates collaborative measurement of multiple types of reflectors, full adaptation of refraction angles, and self-calibration of sound velocity, so as to reduce equipment costs, simplify operating procedures, and achieve high-precision and high-robustness rapid evaluation of frequency parameters. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and device for measuring the center frequency of an ultrasonic oblique probe based on a double-reflector measurement block. The method aims to overcome the problems of existing ultrasonic probe center frequency measurement technology, such as difficulty in identifying high-frequency components, high reflector processing precision requirements, inability of a single test block to adapt to oblique probes with different refraction angles, and the need to know the sound velocity of the material in advance. By integrating collaborative measurement of multiple types of reflectors, full adaptation of refraction angles, and self-calibration of sound velocity, the method reduces equipment costs, simplifies the operating process, and significantly reduces dependence on equipment and environment while ensuring measurement accuracy, thereby achieving high-precision and high-robustness rapid evaluation of frequency parameters.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The method for measuring the center frequency of an ultrasonic angle probe based on a double-reflector measurement block includes the following steps:

[0007] (1) Make a test block;

[0008] The upper and lower surfaces of the test block are parallel. A quarter arc surface with a radius of R is machined on the right side of the test block, and a diameter of d is machined inside the test block. b The spherical hole and a length of l s , diameter d s The depths of the ball hole and the short horizontal hole centers from the upper surface of the test block are the same;

[0009] (2) Measure the echo time of the ultrasonic angle probe;

[0010] Use an ultrasonic oblique probe to couple to the upper surface of the test block, aim the probe at the right arc surface of the test block, move the probe left and right to find the highest echo on the arc surface, and record the echo time t at this time. c ;

[0011] (3) Collect the echo height of the spherical hole and short transverse hole;

[0012] Use an ultrasonic angle probe to couple to the upper surface of the test block, move the probe and find the highest echo of the spherical hole and the short transverse hole respectively, and record the spherical hole echo height H at the same gain. b and the short transverse hole echo height H s ;

[0013] (4) Calculate the central wavelength λ of the ultrasonic angle probe;

[0014] The central wavelength of the ultrasonic angle probe is calculated by formula (1):

[0015]

[0016] Where, d b is the diameter of the spherical hole, d s is the short horizontal hole diameter, l s is the length of the short horizontal hole, H b is the spherical hole echo height, H s is the echo height of the short transverse hole;

[0017] (5) Calculate the center frequency f of the ultrasonic angle probe;

[0018] The center frequency of the ultrasonic angle probe is calculated by formula (2):

[0019]

[0020] Where R is the radius of the arc surface, t c It is the single-trip echo time of the arc surface of the test block.

[0021] A further improvement of the present invention is that the measuring test block is made of an isotropic metal material in step (1).

[0022] A further improvement of the present invention is that the measurement test block produced in step (1) is a ship-shaped measurement test block.

[0023] A further improvement of the present invention is that the diameter d of the spherical hole of the measuring block is b Not less than 10mm.

[0024] A further improvement of the present invention is that the diameter d of the transverse through hole of the measuring block is s Not less than 4mm.

[0025] A further improvement of the present invention is that the depth a from the center of the spherical hole and the transverse through hole to the upper surface of the test block satisfies:

[0026] a>3N·cosβ(3)

[0027] Where N is the near-field length of the ultrasonic angle probe, and β is the incident angle of the ultrasonic angle probe on the test block.

[0028] A further improvement of the present invention is that the length of the short transverse hole of the measuring test block is smaller than the beam cross-sectional size of the ultrasonic angle probe at that position.

[0029] A further improvement of the present invention is that the coupling mode of the ultrasonic angle probe is direct coupling.

[0030] A further improvement of the present invention is that the ultrasonic oblique probe coupling method uses a probe pressing block to maintain stable and uniform coupling at all positions.

[0031] An ultrasonic angle probe center frequency measuring device based on a double-reflector measuring block comprises:

[0032] Make the measuring test block unit: the upper and lower surfaces of the test block are parallel, a quarter arc surface with a radius of R is machined on the right side of the test block, and a diameter of d is machined inside the test block. b The spherical hole and a length of l s , diameter d s The depths of the ball hole and the short horizontal hole centers from the upper surface of the test block are the same;

[0033] Measuring the echo time unit of the ultrasonic oblique probe: Use an ultrasonic oblique probe to couple to the upper surface of the test block, align the probe with the arc surface on the right side of the test block, move the probe left and right to find the highest echo on the arc surface, and record the echo time t at this time c ;

[0034] Collect the echo height of the spherical hole and short transverse hole: Use an ultrasonic angle probe to couple to the upper surface of the test block, move the probe and find the highest echo of the spherical hole and short transverse hole respectively, and record the spherical hole echo height H at the same gain. b and the short transverse hole echo height H s ;

[0035] Calculate the central wavelength λ of the ultrasonic angle probe: The central wavelength of the ultrasonic angle probe is calculated by formula (1):

[0036]

[0037] Where, d b is the diameter of the spherical hole, d s is the short horizontal hole diameter, l s is the length of the short horizontal hole, H b is the spherical hole echo height, H s is the echo height of the short transverse hole;

[0038] Calculate the center frequency f of the ultrasonic angle probe: The center frequency of the ultrasonic angle probe is calculated by formula (2):

[0039]

[0040] Where R is the radius of the arc surface, t c It is the single-trip echo time of the arc surface of the test block.

[0041] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0042] The present invention provides an ultrasonic angle probe center frequency measurement method and device based on a double-reflector measurement block, which solves many bottleneck technical problems of traditional ultrasonic angle probe center frequency measurement technology through collaborative measurement of multiple types of reflectors, full adaptation of refraction angles, and self-calibration of sound speed. Based on the consistency of the reflection characteristics of the spherical hole and the short transverse hole for sound beams at different refraction angles, a combination of the spherical hole and the short transverse hole is designed to achieve adaptability to probes at any refraction angle, eliminating the need to customize multiple sets of test blocks for specific refraction angles. By processing different reflectors on the same test block, the influence of echo amplitude changes caused by processing accuracy on measurement accuracy is offset, reducing measurement errors. The ultrasonic sound velocity is simultaneously measured on the same test block, avoiding sound velocity deviation caused by material temperature changes, tissue differences, etc. The wavelength is calculated by the echo height ratio of the spherical hole and the short transverse hole, offsetting common-mode interference such as uneven coupling agent thickness and changes in test block surface roughness, reducing system errors. Only a conventional ultrasonic detector is required (no spectrum analyzer or high-precision time measurement equipment is required), and the same test block can be adapted to probes of different frequencies, eliminating the need to customize multiple sets of test blocks for specific frequencies, saving equipment and processing costs. The echo data of the spherical hole and the short transverse hole can be obtained simultaneously through a single coupling and scanning, and it is suitable for on-site testing environments, simplifying the operation process and enhancing on-site applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 The present invention is a flow chart of a method for measuring the center frequency of an ultrasonic angle probe based on a double-reflector measurement block.

[0045] Figure 2 This is a schematic diagram of the structure of a center frequency double-reflector measurement test block for an ultrasonic angle probe of the present invention.

[0046] Figure 3 for Figure 2 Top view of .

[0047] Figure 4 This is a schematic diagram of the dimensions and relative position markings of a center frequency double-reflector measurement test block of an ultrasonic angle probe of the present invention.

[0048] Figure 5 for Figure 4 Top view of .

[0049] Figure 6 This is a structural block diagram of the ultrasonic angle probe center frequency measurement device based on a double-reflector measurement block of the present invention.

[0050] Among them, d b is the diameter of the spherical hole, d s is the short horizontal hole diameter, l s is the length of the short horizontal hole, R is the radius of the arc surface, and a is the distance between the center of the spherical hole and the horizontal through hole and the upper surface of the test block. DETAILED DESCRIPTION

[0051] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0052] In the description of the present invention, it is to be understood that when used in this specification and the appended claims, the terms “include” and “comprise” indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0053] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0054] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0055] The accompanying drawings illustrate various schematic diagrams of structures according to embodiments disclosed herein. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0056] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0057] Example 1

[0058] like Figures 1 to 5 As shown, the method for measuring the center frequency of an ultrasonic angle probe based on a double-reflector measurement block provided by the present invention includes the following steps:

[0059] (1) Make a test block

[0060] The ship-shaped test block is made of isotropic metal material. The upper and lower surfaces of the test block are parallel. A quarter-circular arc surface with a radius of R is machined on the right side of the test block. A diameter of d is machined inside the test block. b The spherical hole and a length of l s , diameter d s The depths of the centers of the ball hole and the short horizontal hole from the upper surface of the test block are the same.

[0061] (2) Measure the echo time of the ultrasonic angle probe

[0062] Use an ultrasonic oblique probe to couple to the upper surface of the test block, aim the probe at the right arc surface of the test block, move the probe left and right to find the highest echo on the arc surface, and record the echo time t at this time. c .

[0063] (3) Collecting echo height of spherical hole and short transverse hole

[0064] Use an ultrasonic angle probe to couple to the upper surface of the test block, move the probe and find the highest echo of the spherical hole and the short transverse hole respectively, and record the spherical hole echo height H at the same gain. b and the short transverse hole echo height H s .

[0065] (4) Calculate the central wavelength λ of the ultrasonic angle probe

[0066] The central wavelength of the ultrasonic angle probe is calculated by formula (1):

[0067]

[0068] Where, d b is the diameter of the spherical hole, d s is the short horizontal hole diameter, l s is the length of the short horizontal hole, H b is the spherical hole echo height, H s is the echo height of the short transverse hole.

[0069] (5) Calculate the center frequency f of the ultrasonic angle probe

[0070] The center frequency of the ultrasonic angle probe is calculated by formula (2):

[0071]

[0072] Where R is the radius of the arc surface, t c It is the single-trip echo time of the arc surface of the test block.

[0073] Among them, the ultrasonic oblique probe is one of the core components in ultrasonic testing technology. It transmits ultrasonic beams at an angle to achieve accurate detection of internal defects in workpieces. The structural components of the ultrasonic oblique probe include: Piezoelectric chip: It uses piezoelectric ceramic materials (such as PZT) to convert electrical energy into mechanical vibrations through the inverse piezoelectric effect to generate ultrasonic waves. The chip size directly affects the directionality of the sound beam and the detection range. Angle wedge: Usually made of organic glass or resin, its inclination angle determines the refraction angle (K value) of the ultrasonic beam to achieve waveform conversion (longitudinal wave → transverse wave). Damping block: Absorbs excess vibration on the back of the chip, reduces aftershocks, and improves resolution and signal-to-noise ratio. Protective film: Prevents chip wear and adapts to the needs of rough surface detection. Some probes can replace the protective film to adapt to different working conditions. Housing and cable: The housing protects the internal components, and the cable transmits electrical signals to the detection instrument.

[0074] Example 2

[0075] like Figure 6 As shown, the ultrasonic angle probe center frequency measuring device based on a double-reflector measuring test block provided by the present invention includes:

[0076] Make the measuring test block unit: the upper and lower surfaces of the test block are parallel, and a quarter-circular arc surface with a radius of R is machined on the right side of the test block, and a diameter of d is machined inside the test block. b The spherical hole and a length of l s , diameter d s The depths of the ball hole and the short horizontal hole centers from the upper surface of the test block are the same;

[0077] Measuring the echo time unit of the ultrasonic oblique probe: Use an ultrasonic oblique probe to couple to the upper surface of the test block, align the probe with the arc surface on the right side of the test block, move the probe left and right to find the highest echo on the arc surface, and record the echo time t at this time c ;

[0078] Collect the echo height of the spherical hole and short transverse hole: Use an ultrasonic angle probe to couple to the upper surface of the test block, move the probe and find the highest echo of the spherical hole and short transverse hole respectively, and record the spherical hole echo height H at the same gain. b and the short transverse hole echo height H s ;

[0079] Calculate the central wavelength λ of the ultrasonic angle probe: The central wavelength of the ultrasonic angle probe is calculated by formula (1):

[0080]

[0081] Where, d b is the diameter of the spherical hole, d s is the short horizontal hole diameter, l s is the length of the short horizontal hole, H bis the spherical hole echo height, H s is the echo height of the short transverse hole;

[0082] Calculate the center frequency f of the ultrasonic angle probe: The center frequency of the ultrasonic angle probe is calculated by formula (2):

[0083]

[0084] Where R is the radius of the arc surface, t c It is the single-trip echo time of the arc surface of the test block.

[0085] Example 3

[0086] Measuring center frequency of aviation aluminum alloy test block

[0087] like Figures 1 to 5 As shown, the present invention provides a method for measuring the center frequency of an ultrasonic oblique probe based on a double-reflector measuring block, comprising:

[0088] 1. Test Block Preparation

[0089] Material: 7075 aviation aluminum alloy; 7075 aviation aluminum alloy is a high-strength aluminum alloy with zinc as the primary alloying element. It belongs to the Al-Zn-Mg-Cu series of super-hard aluminum alloys and is widely used in aerospace, high-end equipment manufacturing, and other fields due to its excellent mechanical properties and corrosion resistance. 7075 aluminum alloy has a tensile strength exceeding 560 MPa and a yield strength exceeding 500 MPa, far exceeding that of ordinary aluminum alloys (such as 6061 aluminum alloy) and even exceeding that of some steels. Its strength primarily comes from the solid solution strengthening and aging hardening effects of elements such as zinc, magnesium, and copper. In particular, the precipitation of the MgZn2 phase significantly enhances the material's strength. In atmospheric conditions, a dense aluminum oxide film forms on the surface of 7075 aluminum alloy, effectively preventing further corrosion. However, it should be noted that in marine or industrial corrosive environments, surface treatment processes such as anodizing and spraying are required to further enhance corrosion resistance. 7075 aluminum alloy has good plasticity and toughness, and its plasticity is excellent after solution treatment, making it suitable for subsequent processing. Its fatigue strength and fracture toughness are also superior to many traditional materials and can withstand complex stress environments.

[0090] Test block size: Ship-shaped test block, upper surface size 200 (length) × 50mm (width), thickness 100mm, upper and lower surface parallelism error ≤ 0.02mm;

[0091] Arc surface: The right side is processed into a quarter arc surface with a radius of R = 100mm (the center of the circle is on the upper surface);

[0092] Ball hole parameters: diameter d b =15mm, depth a=70mm;

[0093] Short horizontal hole parameters: diameter d s =4mm, length l s =30mm, depth a=70mm.

[0094] Key design basis:

[0095] Assuming the ultrasonic angle probe has a nominal frequency of 5 MHz, a chip size of 6 × 8 mm, and an incident angle of β = 45°, the near-field length N is calculated to be 30 mm. According to the formula a > 3N·cosβ≈63.6 mm;

[0096] Short horizontal hole length limit: The beam cross-sectional width of the probe at a depth of 70 mm (calculated by the diffusion angle) is approximately 40 mm. s =30mm (less than the beam width) to avoid echo amplitude fluctuations.

[0097] 2. Measure arc surface echo time

[0098] The probe is coupled to position 1 on the upper surface of the test block and moved along the length of the upper surface to find the highest echo signal;

[0099] Record the one-way acoustic path time t after deducting the wedge delay from the echo time c =28μs;

[0100] Calculate the actual speed of sound v = R / t c =100mm / 28μs=3571m / s.

[0101] 3. Measurement steps

[0102] Coupling method: Direct coupling, using glycerin as a coupling agent, and applying a constant pressure of 20N to the probe clamp. The main function of the coupling agent is to eliminate the air gap between the probe and the material being tested, ensuring efficient transmission of ultrasonic or sound wave energy. The air gap will cause the sound wave reflectivity to exceed 99%, significantly reducing the detection sensitivity. The coupling agent fills the gap and matches the acoustic impedance (for example, the acoustic impedance of glycerin is 2.4×10 6 kg / (m2·s), which is close to that of human tissue and metal), which can greatly improve signal transmission efficiency.

[0103] Signal acquisition: Couple the probe to position 2 on the upper surface of the test block, adjust the probe to find the highest echo of the ball hole, set the gain to 50dB, and record the echo amplitude H b =10%; adjust the probe to find the highest echo of the short horizontal hole, set the gain to 50dB, and record the echo amplitude H s =95%.

[0104] 4. Frequency calculation

[0105] 1) Calculate the wavelength λ according to formula (1):

[0106]

[0107] 2) Calculate the center frequency f according to formula (2):

[0108]

[0109] In summary, the present invention addresses the problems of the existing technology, such as the measurement accuracy relying on the processing accuracy of the reflector, being greatly affected by temperature changes and tissue differences, the extremely poor adaptability of a single test block to oblique probes at different angles, and the difference between the sound velocity of known materials and the sound velocity of actual test blocks. The present invention discloses an ultrasonic oblique probe frequency detection method that integrates collaborative measurement of multiple types of reflectors, full adaptation of sound beam angles, and self-calibration of sound velocity. By designing a ship-shaped test block containing a spherical hole and a short transverse hole, combined with sound velocity self-calibration and the consistency of the reflection characteristics of the spherical hole and the short transverse hole for sound beams at different angles, the measurement error and adaptability problems caused by changes in sound velocity, processing accuracy, temperature and tissue, and sound beam angle in the traditional method are solved.

[0110] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from all points of view, the embodiments should be regarded as illustrative and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and range of equivalents of the claims are included in the present invention. Any reference signs in the claims should not be construed as limiting the claim to which they relate.

[0111] In addition, it should be understood that although this specification describes the embodiments, not every embodiment contains only one independent technical solution. This description is for clarity only. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for the purpose of illustrating the technical concept of the present invention and cannot be used to limit the scope of protection of the present invention. Any changes made based on the technical solution in accordance with the technical concept proposed by the present invention fall within the scope of protection of the claims of the present invention.

Claims

1. A method for measuring the center frequency of an ultrasonic angle probe based on a double-reflector measurement block, characterized in that: The following steps are involved: (1) Make a measurement test block; The upper and lower surfaces of the test block are parallel. A quarter arc surface with a radius of R is machined on the right side of the test block, and a diameter of d is machined inside the test block. b The spherical hole and a length of l s , diameter d s The depths of the ball hole and the short horizontal hole centers from the upper surface of the test block are the same; (2) Measure the echo time of the ultrasonic angle probe; Use an ultrasonic oblique probe to couple to the upper surface of the test block, aim the probe at the right arc surface of the test block, move the probe left and right to find the highest echo on the arc surface, and record the echo time t at this time. c ; (3) Collect the echo height of the spherical hole and short transverse hole; Use an ultrasonic angle probe to couple to the upper surface of the test block, move the probe and find the highest echo of the spherical hole and the short transverse hole respectively, and record the spherical hole echo height H at the same gain. b and the short transverse hole echo height H s ; (4) Calculate the central wavelength λ of the ultrasonic angle probe; The central wavelength of the ultrasonic angle probe is calculated by formula (1): Where, d b is the diameter of the spherical hole, d s is the short horizontal hole diameter, l s is the length of the short horizontal hole, H b is the spherical hole echo height, H s is the echo height of the short transverse hole; (5) Calculate the center frequency f of the ultrasonic angle probe; The center frequency of the ultrasonic angle probe is calculated by formula (2): Where R is the radius of the arc surface, t c It is the single-trip echo time of the arc surface of the test block.

2. The method for measuring the center frequency of an ultrasonic angle probe based on a double-reflector measurement block according to claim 1, characterized in that: Step (1) manufactures a measuring test block, wherein the test block is made of an isotropic metal material.

3. The method for measuring the center frequency of an ultrasonic angle probe based on a double-reflector measurement block according to claim 1, characterized in that: The measurement test block produced in step (1) is a ship-shaped measurement test block.

4. The method for measuring the center frequency of an ultrasonic angle probe based on a double-reflector measurement block according to claim 1, characterized in that: The diameter d of the spherical hole of the measuring block b Not less than 10mm.

5. The method for measuring the center frequency of an ultrasonic angle probe based on a double-reflector measurement block according to claim 1, characterized in that: The diameter d of the transverse through hole of the measuring block s Not less than 4mm.

6. The method for measuring the center frequency of an ultrasonic angle probe based on a double-reflector measurement block according to claim 1, characterized in that: The depth a of the center of the spherical hole and the transverse through hole from the upper surface of the test block satisfies: a>3N·cosβ(3) Where N is the near-field length of the ultrasonic angle probe, and β is the incident angle of the ultrasonic angle probe on the test block.

7. The method for measuring the center frequency of an ultrasonic angle probe based on a double-reflector measurement block according to claim 1, characterized in that: The length of the short transverse hole of the measuring test block is smaller than the beam cross-sectional size of the ultrasonic oblique probe at that position.

8. The method for measuring the center frequency of an ultrasonic angle probe based on a double-reflector measurement block according to claim 1, characterized in that: The coupling mode of the ultrasonic angle probe is direct coupling.

9. The method for measuring the center frequency of an ultrasonic angle probe based on a double-reflector measurement block according to claim 8, characterized in that: The ultrasonic oblique probe coupling method uses a probe pressing block to maintain stable and uniform coupling at all positions.

10. An ultrasonic angle probe center frequency measurement device based on a double-reflector measurement block, characterized in that: include: Make the measuring test block unit: the upper and lower surfaces of the test block are parallel, a quarter arc surface with a radius of R is machined on the right side of the test block, and a diameter of d is machined inside the test block. b The spherical hole and a length of l s , diameter d s The depths of the ball hole and the short horizontal hole centers from the upper surface of the test block are the same; Measuring the echo time unit of the ultrasonic oblique probe: Use an ultrasonic oblique probe to couple to the upper surface of the test block, align the probe with the arc surface on the right side of the test block, move the probe left and right to find the highest echo on the arc surface, and record the echo time t at this time c ; Collect the echo height of the spherical hole and short transverse hole: Use an ultrasonic angle probe to couple to the upper surface of the test block, move the probe and find the highest echo of the spherical hole and short transverse hole respectively, and record the spherical hole echo height H at the same gain. b and the short transverse hole echo height H s ; Calculate the central wavelength λ of the ultrasonic angle probe: The central wavelength of the ultrasonic angle probe is calculated by formula (1): Where, d b is the diameter of the spherical hole, d s is the short horizontal hole diameter, l s is the length of the short horizontal hole, H b is the spherical hole echo height, H s is the echo height of the short transverse hole; Calculate the center frequency f of the ultrasonic angle probe: The center frequency of the ultrasonic angle probe is calculated by formula (2): Where R is the radius of the arc surface, t c It is the single-trip echo time of the arc surface of the test block.

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