Ultrasonic radial detection calibration test block and detection method for wheel hub part of railway wagon

Abstract

The invention relates to the technical field of railway wagon wheel ultrasonic nondestructive testing, in particular to a railway wagon wheel hub ultrasonic radial detection calibration test block and a detection method.The railway wagon wheel hub ultrasonic radial detection calibration test block comprises a single test block integrating seven kinds of convex arc detection faces with the diameter phi ranging from 160 mm to 220 mm, radial flat-bottom holes with the diameter phi being 3 mm and the depth being 5 / 35 / 55 mm are formed in the lower portions of all the detection faces, and the material of the radial flat-bottom holes is consistent with that of wheels; according to the matched detection method, a distance amplitude curve is made by matching a probe, and scanning parameters and defect judgment rules are standardized. According to the invention, accurate calibration of the detection sensitivity and consistent transmission of the defect equivalent under multi-specification hub apertures can be realized, and the detection accuracy and efficiency are improved.

Description

Technical Field

[0001] This invention belongs to the field of nondestructive testing technology, and relates to an ultrasonic radial detection calibration block and testing method for the hub of a railway freight car wheel. Background Technology

[0002] As a critical load-bearing component in the rolling stock system, the structural integrity and internal quality of railway freight car wheels directly affect the safety and reliability of train operation. To prevent sudden failures caused by fatigue cracks or internal defects, ultrasonic non-destructive testing has been widely applied in the factory inspection and maintenance of wheels. According to the current industry standard TB / T2817-2018, the wheel hub must undergo both axial and radial ultrasonic testing, with radial testing conducted through the inner wall of the hub bore. Due to the geometric limitations of the hub bore, a convex arc-shaped probe matching the bore diameter must be used to ensure good acoustic coupling and effective sound energy transmission. However, the inner diameter of the hub bore in railway freight car wheels currently used varies, covering seven sizes from φ160mm to φ220mm. Different bore diameters correspond to different sound beam incident angles, propagation paths, and focusing characteristics. If a uniform calibration block is used for sensitivity calibration, it will lead to distortion of the artificial defect echo equivalent, thus affecting the accuracy of the detection sensitivity setting and the consistency of defect judgment.

[0003] In the existing technology, the "calibration sample wheel for ultrasonic testing" with publication number CN216117473U integrates artificial defects (artificial flat-bottom holes) in the rim, tread, spokes, and hub areas, and can be used for overall sensitivity verification and blind zone coverage assessment. However, it adopts a fixed-size integral structure and does not have a modular or replaceable design for different hub bore diameters, making it only suitable for single-specification wheels. Especially in radial testing at the hub, this sample wheel cannot simulate the actual acoustic response conditions of convex arc probes under different bore diameters, causing the calibration results to deviate from the actual testing conditions, making it difficult to meet the accurate equivalent calibration requirements for multiple hub bore diameters. Another patent, CN205157499U, entitled "A Sample Wheel for Ultrasonic Testing of Wheels," features flat-bottomed holes of varying depths in the wheel hub area to improve calibration efficiency. However, it remains a monolithic cast structure with fixed hub hole dimensions, making it unsuitable for various hole diameters ranging from φ160mm to φ220mm. Furthermore, this approach fails to consider the impact of probe curvature matching with the wheel hub hole on the sound field distribution, and the arrangement of artificial defects is not optimized based on the beam focusing characteristics under different hole diameters, resulting in a systematic deviation in calibration sensitivity. Moreover, none of the aforementioned patents propose standardized testing methods compatible with multiple wheel hub hole diameters, lacking standardized guidance on key parameters such as gain compensation and scanning path, making it difficult to support the implementation of highly consistent or automated testing processes.

[0004] In summary, although existing calibration wheel samples have made some progress in functional integration, significant shortcomings remain in the specialization, multi-specification adaptability, and synergy of testing methods for ultrasonic radial testing of the wheel hub. Therefore, there is an urgent need to develop a series of calibration test blocks capable of achieving accurate acoustic simulation for different wheel hub bore diameters, and to establish standardized testing methods to ensure accurate transfer of defect equivalents and high consistency of test results, thereby effectively supporting the safe service and quality control of railway freight car wheels. Summary of the Invention

[0005] This invention addresses the technical shortcomings of existing calibration blocks used in ultrasonic radial testing of railway freight car wheel hubs. These shortcomings include incompatibility with various hub bore diameters, discrepancies between the artificial defect arrangement and actual acoustic field characteristics, and a disconnect between the calibration process and the testing procedure. The invention provides a series of integrated calibration blocks with high acoustic simulation and standardized testing methods. This solution constructs multiple convex arc testing surfaces with matched curvature on a single block substrate, and sets artificial flat-bottomed holes of standard equivalent value arranged radially below each testing surface. This achieves accurate calibration of ultrasonic testing sensitivity and consistent transfer of defect equivalent values ​​for seven hub bore diameters ranging from φ160 mm to φ220 mm.

[0006] This invention provides an ultrasonic radial detection calibration block for the hub portion of a railway freight car wheel. The calibration block is an integral metal structure comprising seven independent convex arc detection surfaces arranged in a ring or sector array along the end face of the block. The diameters of each convex arc detection surface are φ160 mm, φ170 mm, φ180 mm, φ190 mm, φ200 mm, φ210 mm, and φ220 mm, corresponding to seven standard inner diameter specifications of the hub bore of a railway freight car wheel, respectively. A convex arc detection surface with a specific radius of curvature is machined on the circumferential side or designated end face of the block. The calibration block is cylindrical in shape, with its outer cylindrical surface serving as a reference surface. Each convex arc detection surface is recessed radially inward from this reference surface by 3 mm. The surface is machined to a diameter of φ3mm, with a radius of curvature equal to half the inner diameter of the corresponding wheel hub bore to simulate the geometry of the inner wall of the wheel hub bore. The radius of curvature of this convex arc surface is consistent with the inner wall of the corresponding wheel hub bore, used to achieve full acoustic coupling contact with a convex arc probe of the same curvature diameter. Directly below each convex arc detection surface, three artificial flat-bottomed holes are set along the thickness direction of the test block, i.e., axially. The diameters of these flat-bottomed holes are all φ3mm, with depths of 5mm, 35mm, and 55mm respectively, covering the typical wall thickness range of the wheel hub. The axial direction of these flat-bottomed holes is perpendicular to the tangent direction of the corresponding convex arc detection surface at the hole position, i.e., radially arranged along the radius direction of the wheel hub, to simulate the reflection path and echo characteristics of actual defects under radially incident sound beams. The material, heat treatment state, and surface roughness of all flat-bottomed holes and detection surfaces are consistent with the wheel product being tested. The material is CL60 or ER8 grade wheel steel, the heat treatment state is normalizing and tempering, and the surface roughness Ra ≤ 1.6. μm; the machining depth tolerance of the flat-bottomed hole is controlled within ±0.1 mm, the bottom of the hole is a flat plane, without taper, chamfer or other geometric deviations; an isolation groove is provided between adjacent convex arc detection surfaces, which runs through the test block along the axial direction, with a groove width of not less than 5 mm and a groove depth of not less than 60 mm, to ensure that the ultrasonic propagation path between adjacent detection areas is completely cut off, so as to block ultrasonic crosstalk between adjacent detection areas; each group of flat-bottomed holes is arranged in a staggered manner in the circumferential direction or is equipped with mechanical marking, laser marking or other positioning marks, so as to facilitate the operator to quickly identify the target detection surface and its corresponding defect location.

[0007] Furthermore, the seven convex arc detection surfaces are integrated on the same metal substrate to form a single-unit combined calibration block, which avoids the problems of complex management and frequent replacement of traditional multi-block calibration, while ensuring that the relative positional relationship between each detection surface is fixed, which is conducive to improving the efficiency and repeatability of on-site calibration.

[0008] The present invention also provides an ultrasonic radial detection method for the hub portion of a railway freight car wheel based on the above-mentioned calibration test block, the detection method comprising the following steps:

[0009] S1. Test block matching and calibration preparation: Based on the actual inner diameter of the wheel hub hole of the wheel to be inspected, select a convex arc detection surface on the calibration test block that matches its hole diameter; select a convex arc probe with the same curvature diameter, and uniformly coat the detection surface with a coupling agent of the same type, viscosity and thickness as that used in the subsequent formal test before calibration;

[0010] S2. Place the convex arc probe on the target convex arc detection surface and sequentially probe the three artificial flat-bottomed holes of corresponding depths on the detection surface; adjust the gain of the ultrasonic testing instrument so that the maximum reflected echo height of each flat-bottomed hole reaches 50% of the full width of the fluorescent screen, and record the corresponding sound path value and amplitude value; based on the material's sound velocity and attenuation coefficient, adopt the exponential attenuation model: Fitting data at three points: 5 mm, 35 mm, and 55 mm. Let A(d) be the longitudinal wave attenuation coefficient in steel, A0 be the initial sound pressure amplitude of the ultrasonic wave after propagation distance d, and e be the initial sound pressure amplitude of the ultrasonic wave. -ad The exponential decay factor is extrapolated to generate distance amplitude curves in the range of 0–80 mm;

[0011] S3. Formal Testing Implementation: After cleaning the inner wall of the wheel hub hole of the wheel to be tested, apply the same coupling agent as during calibration; place the convex arc probe with matching curvature tightly against the inner wall of the hub hole, keeping the center line of the probe's sound beam along the radial direction of the hub hole, and aligning the center of the probe's curvature with the axis of the hub hole; perform a spiral scan by moving the probe in a combined circumferential and axial motion along the hub hole at a speed not exceeding 150 mm / s, with the overlap area between adjacent scan trajectories not less than 10% of the effective size of the probe chip, ensuring full coverage of the hub area without any blind spots;

[0012] S4. Defect Judgment and Recording: When a defect echo is detected during the inspection process, move the probe to locate the position of its highest amplitude, and read the corresponding depth value and amplitude height (%FSH) of the defect; compare the defect amplitude with the distance amplitude curve value at the same depth: if the defect amplitude is higher than the curve value, it is judged as an out-of-standard defect and the wheel is unqualified; if the defect amplitude is not higher than the curve value, it is judged as a qualified defect and the wheel is acceptable; record the defect location information (including depth and circumferential angle), amplitude value, waveform characteristics and final judgment conclusion, and generate a complete inspection report for archiving and future reference.

[0013] The distance amplitude curve is established strictly in accordance with the requirements for radial detection sensitivity of the hub area in the TB / T 2817-2018 standard. A φ3 mm flat-bottomed hole is used as the reference reflector to ensure that the calibration results have industry universality and regulatory compliance. The setting of the probe scanning speed and trajectory overlap rate is calculated based on the physical parameters of the sound beam diffusion angle and the crystal size, which not only meets the detection coverage requirements, but also prevents missed detections or signal distortion due to excessive scanning speed.

[0014] Specifically, the arrangement of the flat-bottomed holes in the calibration block is not arbitrary, but optimized based on the influence of changes in the hub aperture on the focusing characteristics of the sound beam. Since the incident angle and focal point of the sound beam differ for convex arc probes with different aperture diameters, if the artificial defects are still arranged parallel to the axial direction, the echo amplitude will deviate from the actual defect response. Therefore, this invention sets the axial direction of the flat-bottomed holes to be perpendicular to the tangent direction of the corresponding arc surface at the hole position, i.e., arranged along the hub radius. This ensures that, regardless of the aperture condition, the sound beam irradiates the bottom surface of the flat-bottomed hole in an approximately perpendicular manner, obtaining the maximum reflected echo and truly reflecting the acoustic behavior of the actual defect in radial detection.

[0015] Furthermore, the material and heat treatment state of the calibration test block are completely identical to those of the wheel being tested, in order to eliminate the influence of factors such as material sound velocity, attenuation coefficient, and grain structure on ultrasonic propagation characteristics. If a test block is made of dissimilar materials, even if the geometric dimensions are the same, the difference in acoustic impedance will cause deviations in echo amplitude, thus affecting the accuracy of sensitivity calibration. Therefore, this invention explicitly limits the test block material to CL60 or ER8 grade wheel steel, and subjectes it to the same normalizing and tempering treatment as the wheel, ensuring uniform microstructure, fine grains, and stable acoustic performance.

[0016] Furthermore, the recess depth of the convex arc detection surface is uniformly set at 3 mm, which is the optimal parameter after comprehensively considering probe contact stability, acoustic coupling effect, and manufacturing feasibility. If the recess is too shallow, it will be difficult to accommodate a convex arc surface with sufficient curvature, affecting probe fit; if the recess is too deep, it may weaken the structural strength of the test block or increase manufacturing difficulty. Experimental verification shows that a depth of 3 mm can maintain the overall rigidity of the test block while ensuring good acoustic coupling, making it suitable for repeated use in the field.

[0017] The beneficial effects of this invention are reflected in the following aspects:

[0018] First, by integrating seven convex arc detection surfaces of different diameters onto the same test block, a precise one-to-one match between the calibration test block and the geometric parameters of the hub hole is achieved. This structural design fundamentally solves the problems of beam deflection, focusing failure, and echo equivalent distortion caused by the mismatch between the probe and the workpiece curvature, ensuring that the calibration sensitivity truly reflects the acoustic response under actual testing conditions.

[0019] Secondly, the artificial flat-bottomed holes employ a uniform φ3 mm diameter, a three-level depth gradient of 5 / 35 / 55 mm, and are strictly arranged radially. Combined with a uniform 3 mm arc depth and consistent material design, this ensures that the sound propagation path, reflection mechanism, and attenuation law are highly consistent with the actual wheel hub. This arrangement overcomes the sound beam incident angle deviation caused by the axial parallel setting of flat-bottomed holes in existing technologies, significantly improving the representativeness and reliability of the distance amplitude curve.

[0020] Furthermore, the testing method clearly specifies key parameters such as coupling agent consistency, probe coaxiality, scanning speed, trajectory overlap rate, and defect judgment rules, forming a complete closed-loop control process from calibration to testing and judgment. This process effectively suppresses the impact of human operational differences on the test results, meets the requirements of automated testing systems for standardized input, and provides a reproducible technical basis for quality traceability.

[0021] Finally, the modular design significantly reduces the number of test blocks, lowering manufacturing costs and reducing warehousing management burdens. Operators only need to perform calibration preparation for multiple apertures with a single clamping operation, significantly improving on-site work efficiency. This design balances high precision and practicality, making it suitable for high-volume, multi-specification wheel inspection scenarios in railway maintenance bases, manufacturing plants, and third-party testing institutions.

[0022] In summary, this invention not only solves the problem of insufficient applicability of existing calibration sample wheels in radial detection of wheel hubs, but also establishes a new paradigm for the transfer of ultrasonic detection values ​​for multi-specification railway freight car wheels through structural innovation and methodological synergy. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the ultrasonic detection principle of the present invention;

[0024] Figure 2 This is a schematic diagram of the railway freight car wheel product structure targeted by the present invention;

[0025] Figure 3 This is a schematic diagram of the convex arc probe structure used in this invention;

[0026] Figure 4 This is a schematic diagram illustrating the working condition of the present invention in actual testing, where a convex arc probe is used to perform radial scanning of the hub area from the inner wall of the hub hole;

[0027] Figure 5 This is a schematic diagram of the distance amplitude curve (DAC) fabricated based on the calibration test block according to the present invention;

[0028] Figure 6 This is a schematic diagram illustrating the comparison between defect echo and distance amplitude curve in this invention to determine whether the defect exceeds the standard.

[0029] Figure 7 This is a schematic diagram of the ultrasonic radial detection calibration test block structure for the hub portion of a railway freight car wheel according to the present invention.

[0030] The attached figures are labeled as follows:

[0031] 11. Convex arc probe; 12. Artificial flat bottom hole; 21. Tread; 22. Wheel rim; 23. Spoke; 24. Wheel hub; 25. Wheel hub hole. Detailed Implementation

[0032] The specific embodiments of the present invention, in conjunction with the accompanying drawings, provide a detailed description of the ultrasonic radial detection calibration block and detection method for the hub portion of railway freight car wheels. For example... Figure 7As shown, the calibration block of this invention is an integral metal structure, made of the same CL60 or ER8 grade wheel steel as the railway freight car wheel being tested, and undergoes the same normalizing and tempering heat treatment process as the wheel product to ensure that its microstructure is uniform, grains are fine, and acoustic properties such as sound velocity, attenuation coefficient, and acoustic impedance are consistent with those of the actual wheel. The surface roughness of the block is controlled to Ra ≤ 1.6 μm to ensure stable and reliable ultrasonic coupling effect. The end face of the block integrates 7 independent convex arc detection surfaces, with diameters of φ160 mm, φ170 mm, φ180 mm, φ190 mm, φ200 mm, φ210 mm, and φ220 mm, respectively corresponding to the 25mm inner diameter specifications of the hub bore of the 7 types of railway freight car wheels specified in the TB / T 2817-2018 standard. Each convex arc detection surface is recessed 3 mm inward from the reference end face of the test block, forming an outwardly convex arc surface. Its radius of curvature is completely consistent with the inner wall of the corresponding hub hole 25, which is used to achieve full-contact acoustic coupling with the convex arc probe 11 with the same curvature diameter. An isolation groove with a width of not less than 5 mm is provided between adjacent convex arc detection surfaces to effectively block crosstalk between ultrasonic waves in different detection areas and ensure signal purity during calibration. Directly below each convex arc detection surface, three artificial flat-bottomed holes 12 are set along the thickness direction of the test block. The hole diameter is uniformly φ3 mm, and the depths are 5 mm, 35 mm, and 55 mm, respectively, covering the typical wall thickness range of the hub. The axial direction of all flat-bottomed holes 12 is perpendicular to the tangent direction of the corresponding convex arc detection surface at the hole position, that is, radially arranged along the hub radius direction to simulate the reflection path of actual defects under the action of radial incident sound beams. For example, in the area corresponding to the φ160 mm inspection surface, holes 1 (5 mm deep), 2 (35 mm deep), and 3 (55 mm deep) are all drilled along the normal direction of the arc at that location; similarly, holes 4, 5, and 6 correspond to the φ170 mm inspection surface, and so on up to holes 19, 20, and 21 corresponding to the φ220 mm inspection surface. The machining depth tolerance of all flat-bottomed holes 12 is controlled within ±0.1 mm, and the bottom of the holes is a flat plane without taper, chamfer, or other geometric deviations to ensure stable and repeatable reflection characteristics. Each set of flat-bottomed holes 12 is staggered in the circumferential direction. The angular distance between two adjacent sets of flat-bottomed holes in the circumferential direction is not less than 15°, and the projections of each hole in the axial direction do not overlap. Directly below each convex arc detection surface, three artificial flat-bottomed holes 12 are set along the thickness direction of the test block. The hole diameter is uniformly φ3 mm, and the depths are 5 mm, 35 mm and 55 mm respectively, covering the typical wall thickness range of the wheel hub. The axial direction of all flat-bottomed holes 12 is perpendicular to the tangent direction of the corresponding convex arc detection surface at the hole position, that is, radially arranged along the radius direction of the wheel hub, so as to simulate the reflection path of the actual defect under the action of the radial incident sound beam.

[0033] To prevent acoustic signal crosstalk between different detection surfaces or between artificial flat-bottomed holes 12 at different depths on the same detection surface during ultrasonic testing, which could affect the accuracy and repeatability of the calibration curve, this invention features a specially designed spatial arrangement for the flat-bottomed holes 12. Specifically:

[0034] Circumferential staggered arrangement: Each group of artificial flat-bottomed holes 12 is arranged in a staggered manner in the circumferential direction, with a circumferential angular spacing of no less than 15° between adjacent groups of flat-bottomed holes. This angle value is calculated based on the -6 dB diffusion angle of the ultrasonic beam in the direction of the main sound beam. Taking a typical convex arc probe with a frequency of 2.5 MHz and a wafer size of Φ10 mm as an example, its half-diffusion angle in the longitudinal wave sound field in steel is approximately 7.2°. To ensure that the main sound beams between adjacent holes do not overlap and interfere, while also considering the compactness of the circumferential dimensions of the test block, the safety factor is taken as twice the diffusion angle, i.e., the minimum circumferential angular spacing is set at 15°. This design ensures that when the probe is aligned with a certain detection surface for calibration, the artificial flat-bottomed holes 12 below the adjacent detection surface are outside the coverage area of ​​the main sound beam, thereby avoiding false triggering or interference echoes.

[0035] Axial projections do not overlap: The projections of each group of artificial flat-bottomed holes 12 in the axial direction (i.e., the thickness direction of the test block) do not overlap. In other words, the position coordinates of any two artificial flat-bottomed holes corresponding to different detection surfaces in the axial direction of the test block are strictly staggered, maintaining a distance of at least 5 mm. The purpose is that even if the probe moves along the thickness direction of the test block for scanning, it will not simultaneously receive reflected signals from two different detection surfaces corresponding to flat-bottomed holes, avoiding echo confusion or amplitude superposition due to spatial overlap.

[0036] Grouping and Positioning Identification: To further enhance ease of use, laser markings or mechanical markings are provided on the surface of each test surface in corresponding areas, clearly indicating the depth sequence and corresponding aperture specifications of the flat-bottomed holes 12 in that group. Operators can quickly locate the target test surface based on the markings, avoiding misuse or misaligned scanning.

[0037] The auxiliary function of the isolation groove: An isolation groove with a width of not less than 5 mm is provided between adjacent convex arc detection surfaces. This structure physically blocks the crosstalk path of ultrasonic waves propagating along the surface of the test block. Especially when using large-angle scanning or high-gain settings, it effectively suppresses the interference of reflected signals from non-target areas on the calibration process.

[0038] In summary, this invention systematically solves the acoustic interference problem between multiple sets of artificial defects by combining circumferential angular misalignment, axial projection separation, and physical isolation grooves. This ensures that the φ3 mm flat-bottomed hole under each convex arc detection surface can be accurately identified and calibrated in a pure signal background, thus providing a reliable data foundation for the construction of distance amplitude curves.

[0039] Before actual testing, the distance amplitude curve (DAC) generation step is first performed. Taking a wheel with a hub bore diameter of φ160 mm as an example, the operator positions the φ160 mm convex arc test surface on the calibration block (corresponding to...). Figure 7 The first detection surface on the left side of the middle section), using a convex arc probe 11 with a front working surface curvature of φ160 mm (see... Figure 3 Before calibration, apply a uniform coating of coupling agent (usually machine oil or special ultrasonic coupling grease) of the same type, viscosity and thickness as that used in subsequent formal testing to the test surface to ensure consistent acoustic coupling conditions.

[0040] Before generating the DAC curve, the sound velocity of the material being tested should be correctly set in the ultrasonic testing instrument. For CL60 or ER8 wheel steel, the longitudinal wave sound velocity is usually set to 5900 m / s (or based on the actual measured value) to ensure the accuracy of the depth reading.

[0041] The convex arc probe 11 is tightly fitted onto the detection surface. The ultrasonic testing instrument is started, and the probe is moved to find the maximum reflected echo of hole 1 (5 mm deep, φ3 mm). When the echo signal reaches 50% of the full height of the fluorescent screen (i.e., 50% FSH), the corresponding sound path value d1=5 mm and the instrument gain value G1 are recorded. This gain value indirectly reflects the echo amplitude A(5) of the φ3 mm flat-bottomed hole at this depth. Then, holes 2 (35 mm deep) and 3 (55 mm deep) are detected in sequence. The gain is adjusted so that the maximum reflected echo of each hole reaches 50% FSH. The sound path values ​​d2=35 mm and d3=55 mm and the corresponding gain values ​​G2 and G3 are recorded respectively.

[0042] Based on the exponential attenuation law of ultrasound propagation in a medium, the change of sound pressure amplitude with propagation distance satisfies the following physical model:

[0043] ,

[0044] in The longitudinal wave attenuation coefficient is the measured value of the tested material (CL60 or ER8 wheel steel), expressed in Np / mm (neppers per millimeter) or dB / mm (decibels per millimeter). Its value depends on the material's grain size, heat treatment condition, and ultrasonic testing frequency.

[0045] A(d): Sound pressure amplitude of the ultrasonic wave after it has traveled a distance d.

[0046] A0: Initial sound pressure amplitude of the ultrasound wave.

[0047] e -ad The exponential decay factor describes the physical law that sound pressure decreases exponentially with increasing propagation distance;

[0048] In practical ultrasonic testing instruments, echo height (%FSH) is directly proportional to sound pressure amplitude, and the adjustment of instrument gain (in dB) is logarithmically related to the amplitude ratio. Therefore, the above exponential decay model can be converted into a form expressed in decibels:

[0049] ,

[0050] In other words, during the fabrication of the distance amplitude curve, the echo amplitude (in dB) of flat-bottomed holes at different depths is linearly related to the propagation distance d, and its slope is -8.686α.

[0051] Based on this physical principle, the operator inputs the three sets of recorded data (d1, G1), (d2, G2), and (d3, G3) into the ultrasonic testing instrument or processes them manually. Specifically:

[0052] Data conversion: Converting the gain G required to achieve 50% FSH echo at various depths. i Convert to relative dB values. Typically, the gain G1 of the shallowest aperture (5 mm) is used as a reference, and its relative gain is defined as 0 dB. Therefore, the relative gains of the 35 mm and 55 mm apertures are ΔG2 = G2 - G1 (dB) and ΔG3 = G3 - G1 (dB), respectively. These relative gain values ​​reflect the decrease in echo amplitude due to increased sound path and material attenuation.

[0053] Attenuation coefficient fitting: According to the exponential attenuation model, the relative gain ΔG and the path difference Δd satisfy a linear relationship: ΔG = -8.686α·Δd

[0054] Using the measured data from two points (Δd2=30 mm, ΔG2) and (Δd3=50 mm, ΔG3) (or three-point linear regression), the actual attenuation coefficient α of the material can be calculated: For example, if the measured gain of a 35 mm aperture is 6 dB higher than that of a 5 mm aperture to achieve 50% FSH, i.e., ΔG2 = -6 dB, then α = 6 / (8.686 × 30) ≈ 0.023 dB / mm. This calculated value is the actual attenuation coefficient of the test block at the current detection frequency.

[0055] DAC curve extrapolation: After obtaining the attenuation coefficient α, the theoretical echo amplitude of a φ3 mm flat-bottomed hole at any depth d within the entire detection depth range (0–80 mm) can be extrapolated according to the exponential attenuation model. For a flat-bottomed hole at depth d, the gain compensation ΔG(d) required to achieve 50% FSH is given by the following formula: ΔG(d) = -8.686α·(d-5), where a 5 mm hole is used as the reference point (i.e., ΔG = 0 dB when d = 5 mm). Based on this formula, a series of theoretical gain compensation values ​​for discrete depth points can be calculated. Smoothly connecting these points forms a complete range-amplitude curve, such as... Figure 5 As shown. This curve uses a φ3 mm flat-bottomed hole as the reference reflector and strictly follows the requirements of TB / T 2817-2018 standard regarding radial detection sensitivity of the wheel hub, ensuring that the calibration results have industry universality and regulatory compliance.

[0056] It is important to emphasize that the core of the above fitting and extrapolation process lies in accurately measuring the material's attenuation coefficient α. Since α is extremely sensitive to the material's grain size and heat treatment state, this invention ensures that the α value measured on the test block can be directly applied to actual wheel testing by requiring that the test block be completely identical to the material and heat treatment state of the wheel being tested (CL60 or ER8, normalizing and tempering), thereby eliminating the sensitivity deviation caused by differences in the acoustic properties of the materials.

[0057] After calibration, the formal testing phase begins. This involves the railway freight car wheels to be inspected (structure such as...). Figure 2 As shown, the inner wall of the hub hole 25 (including tread 21, rim 22, spokes 23, hub 24, and hub hole 25) is cleaned to remove oil, rust, and burrs, and then coated with the same coupling agent used during calibration. A convex arc probe 11 with matching curvature (e.g., a φ160 mm probe for a φ160 mm hub hole) is placed tightly against the inner wall of the hub hole 25, ensuring that the probe axis is coaxial with the hub hole 25 axis to maintain radial incidence of the sound beam along the hub radius. Figure 4 As shown. The probe performs a spiral scan along the inner wall of the hub hole 25 at a speed not exceeding 150 mm / s, covering the entire hub area 24; approximately 15% overlap is maintained between adjacent scan trajectories (calculated based on the effective size of the probe chip) to ensure no blind spots. During the scan, if an abnormal echo appears on the ultrasonic testing instrument screen, the probe is slowly moved to precisely locate the position of the highest reflected wave of the defect, and the corresponding depth value (converted from the sound path) and amplitude height (%FSH) are read. Figure 6As shown, the defect amplitude is compared with the threshold on the distance-amplitude curve at the same depth: if the defect amplitude is higher than the curve value, it is judged as an excessive defect and the wheel is unqualified; if it is not higher than the curve value, it is judged as qualified and the wheel is acceptable. At the same time, the defect location information (including axial depth and circumferential angle), waveform characteristics, amplitude value and final judgment conclusion are recorded, and an inspection report is generated for archiving and future reference.

[0058] The key to this invention lies in the coordinated design of the calibration test block and the detection method. Because different inner diameters of the hub bore 25 cause variations in the incident angle and focusing characteristics of the acoustic beam of the convex arc probe 11, if the artificial flat-bottomed holes 12 are still arranged parallel to the axial direction (as in traditional sample wheels), the acoustic beam will be incident at an inclined angle on the bottom surface of the flat-bottomed hole, resulting in a significantly lower reflected echo amplitude than in the case of perpendicular incident, leading to lower calibration sensitivity and thus a risk of missed detection. Therefore, this invention sets the axial direction of each flat-bottomed hole 12 to be perpendicular to the tangent direction of the corresponding convex arc detection surface at the hole position, i.e., radially arranged along the hub radius direction. This ensures that, regardless of the hole diameter, the ultrasonic beam can be incident approximately perpendicularly to the bottom surface of the flat-bottomed hole 12, obtaining the maximum reflected echo and truly reflecting the acoustic response of the actual radial defect. Furthermore, the strict consistency of the test block material, heat treatment state, and surface state eliminates the sound velocity and attenuation deviations caused by material differences, ensuring the exponential decay model... The invention achieves accurate measurement and transmission of the attenuation coefficient α; a uniform 3 mm arc recess depth ensures good probe fit while considering structural strength and manufacturing feasibility; and a modular structure avoids the efficiency loss and management chaos caused by frequent replacement of multiple test blocks in traditional methods. In summary, this invention, through geometric matching, acoustic simulation, and process standardization, achieves high precision, high consistency, and high efficiency in ultrasonic radial testing of railway freight car wheel hubs. It is suitable for the large-scale testing needs of manufacturers, maintenance bases, and third-party testing institutions for wheels of various specifications from ф160 mm to ф220 mm.

Claims

1. A calibration block for ultrasonic radial detection of the hub portion of a railway freight car wheel, wherein the calibration block is an integral metal structure, characterized in that... The test block includes seven independent convex arc detection surfaces arranged in a ring or sector array along the end face of the test block; the diameters of each convex arc detection surface are φ160 mm, φ170 mm, φ180 mm, φ190 mm, φ200 mm, φ210 mm and φ220 mm respectively; convex arc detection surfaces with specific radii of curvature are machined on the circumferential side or designated end face of the test block, the calibration test block is cylindrical in shape, and its outer cylindrical surface serves as a reference surface; each convex arc detection surface is machined by recessing 3 mm radially inward from the reference surface, and its radius of curvature is equal to half of the inner diameter of the corresponding hub hole, so as to simulate the geometry of the inner wall of the hub hole; directly below each convex arc detection surface, three artificial flat-bottomed holes (12) are set along the thickness direction of the test block, the diameter of each artificial flat-bottomed hole (12) is φ3 mm, and the depths are 5 mm, 35 mm and 55 mm respectively. mm; At the geometric center of each convex arc detection surface, three artificial flat-bottomed holes (12) are drilled downward along the normal direction of the surface at that point, with the hole axis passing through the geometric center point to ensure that the sound beam is incident perpendicularly; An isolation groove is provided between adjacent convex arc detection surfaces, with a groove width of not less than 5 mm and a groove depth of not less than 60 mm, to ensure that the ultrasonic propagation path between adjacent detection areas is completely cut off.

2. The ultrasonic radial detection calibration test block for the hub portion of a railway freight car wheel as described in claim 1, characterized in that... The calibration test block is made of CL60 or ER8 grade wheel steel, and the heat treatment state is normalizing and tempering, with a surface roughness Ra≤ 1.6 μm.

3. The ultrasonic radial detection calibration test block for the hub area of ​​railway freight car wheels as described in claim 2, characterized in that... The machining depth tolerance of the artificial flat-bottomed hole (12) is ±0.1 mm, and the bottom of the hole is a flat plane without taper, chamfer or other geometric deviations.

4. The ultrasonic radial detection calibration test block for the hub area of ​​railway freight car wheels as described in claim 1, characterized in that... Each group of artificial flat-bottomed holes (12) is arranged in a staggered manner in the circumferential direction, and a positioning mark is provided on the surface of the test block to identify the target detection surface and its corresponding artificial flat-bottomed hole (12).

5. The ultrasonic radial detection calibration test block for the hub portion of a railway freight car wheel as described in claim 4, characterized in that... The positioning mark is a mechanical engraving or a laser mark.

6. A method for ultrasonic radial detection of the hub portion of a railway freight car wheel based on a calibration test block as described in any one of claims 1 to 5, characterized in that... Includes the following steps: S1. Based on the actual inner diameter of the wheel hub hole (25) to be inspected, select a convex arc detection surface on the calibration test block that matches its hole diameter; select a convex arc probe (11) with the same curvature diameter, and uniformly coat the detection surface with a coupling agent of the same type, viscosity and thickness as that used in the formal test; S2. Place the convex arc probe (11) on the target convex arc detection surface, and sequentially detect the artificial flat-bottom holes (12) of the corresponding depths on the detection surface; adjust the gain of the ultrasonic detector so that the maximum reflected echo height of each flat-bottom hole (12) reaches 50% of the full width of the fluorescent screen, and record the corresponding sound path value and amplitude value; based on the material sound velocity and attenuation coefficient, adopt the exponential attenuation model: Fitting data at three points: 5mm, 35mm, and 55mm. Let A(d) be the longitudinal wave attenuation coefficient in steel, A0 be the initial sound pressure amplitude of the ultrasonic wave after propagation distance d, and e be the initial sound pressure amplitude of the ultrasonic wave. -ad The exponential attenuation factor is extrapolated to generate a distance amplitude curve in the range of 0–80 mm; S3. After cleaning the inner wall of the wheel hub hole (25) of the wheel to be inspected, apply the same coupling agent as during calibration; place the convex arc probe (11) with matching curvature close to the inner wall of the wheel hub hole (25), keep the center line of the probe beam along the radial direction of the wheel hub hole (25), and make the center of curvature of the probe coincide with the axis of the wheel hub hole; the probe performs a spiral scan along the circumferential and axial composite motion of the wheel hub hole (25) at a speed of no more than 150 mm / s, and the overlap area between adjacent scan trajectories is no less than 10% of the effective size of the probe wafer; S4. When a defect echo is detected during the inspection process, move the probe to locate the position of its highest amplitude, and read the depth value and amplitude height corresponding to the defect; compare the defect amplitude with the distance amplitude curve value at the same depth: if the defect amplitude is higher than the curve value, it is determined to be an out-of-standard defect; if the defect amplitude is not higher than the curve value, it is determined to be a qualified defect; record the defect location information, amplitude value, waveform characteristics and final judgment conclusion, and generate an inspection report for archiving and future reference.

7. The ultrasonic radial detection method for the hub portion of a railway freight car wheel as described in claim 6, characterized in that... The distance amplitude curve was established in accordance with the requirements for radial detection sensitivity of the hub in the TB / T 2817-2018 standard, and a φ3 mm flat-bottomed hole was used as the reference reflector.

8. The ultrasonic radial detection method for the hub portion of a railway freight car wheel as described in claim 6, characterized in that... The front working surface of the convex arc probe (11) is a convex arc surface that matches the curvature of the inner wall of the hub hole (25).

9. The ultrasonic radial detection method for the hub portion of a railway freight car wheel as described in claim 6, characterized in that... The axial direction of the artificial flat-bottom hole (12) is arranged radially along the hub radius so that the ultrasonic beam is incident approximately perpendicularly onto the bottom surface of the artificial flat-bottom hole (12).

10. The ultrasonic radial detection method for the hub portion of a railway freight car wheel as described in claim 6, characterized in that... The calibration test block is consistent with the material, heat treatment state and surface roughness of the wheel being tested.

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