A hardened layer depth ultrasonic scattering imaging method, device, electronic equipment and storage medium

Abstract

This invention relates to the field of detection technology, and in particular to a method, apparatus, electronic device, and storage medium for ultrasonic scattering imaging of hardened layer depth. The method effectively suppresses random noise interference and significantly improves the signal-to-noise ratio by introducing a common scattering point set construction method based on the Huygens-Fresnel principle. Through velocity scanning analysis technology based on common scattering point sets, the difference in sound velocity between the hardened layer and the substrate material is accurately inverted, fundamentally solving the measurement error caused by inaccurate sound velocity assumptions in traditional methods. Furthermore, by combining a specified offset algorithm, high-resolution imaging of the boundary of complex-shaped hardened layers is achieved, significantly improving the accuracy of hardened layer depth assessment and the clarity of interface identification, providing a more reliable solution for non-destructive testing and evaluation of the quality of heat-treated workpieces.

Description

Technical Field

[0001] This invention relates to the field of detection technology, and in particular to a method, apparatus, electronic device, and storage medium for ultrasonic scattering imaging of hardened layer depth. Background Technology

[0002] The depth and uniformity of hardened layers (such as hardened layers and carburized layers) are key parameters determining the fatigue strength, wear resistance, and service life of mechanical parts. Ultrasonic testing technology, due to its non-destructive and efficient characteristics, is widely used in such tests. Among these, ultrasonic backscattering is one of the most commonly used techniques in industrial testing. Its basic principle is to utilize the scattering of high-frequency ultrasonic waves at the interface between the dense-grained hardened layer and the coarse-grained matrix material. By calculating the round-trip time of the ultrasonic waves and combining it with the sound velocity, the depth of the hardened layer can be estimated.

[0003] However, existing technologies have significant drawbacks: The sound velocity assumption is inaccurate: It is commonly assumed that ultrasonic waves propagate at the same speed in the hardened layer and the substrate, which does not match the actual acoustic properties of the material and introduces a large measurement error.

[0004] Poor adaptability to complex interfaces: For inclined or irregular hardened layer boundaries formed by processes such as laser hardening and carburizing quenching, traditional single-point detection or B-scanning methods based on A-scan combination suffer from blurred imaging, difficulty in interface identification, and inaccurate depth extraction due to echo path errors and sound velocity non-uniformity.

[0005] The method of obtaining velocity is crude: traditional methods estimate the average velocity by dividing the total thickness by the total duration, ignoring the difference in sound velocity between layers, and thus have limited accuracy.

[0006] Imaging method limitations: Traditional B-scan or total focusing (TFM) methods are limited by wavelength and aperture, resulting in insufficient resolution. They are also susceptible to noise interference and artifacts, making it difficult to clearly characterize sub-millimeter morphology and complex interfaces.

[0007] Therefore, there is an urgent need for a hardened layer depth detection method that can accurately invert interlayer sound velocity, adapt to complex interface morphology, and achieve high-resolution imaging. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a method, apparatus, electronic device, and storage medium for ultrasonic scattering imaging of hardened layer depth.

[0009] In a first aspect, embodiments of the present invention provide a method for ultrasonic scattering imaging of hardened layer depth, the method comprising: An ultrasonic phased array probe is used to perform full matrix data acquisition on the workpiece under test, and to obtain ultrasonic echo signals under all combinations of transmitting and receiving array elements. For the scattering points to be imaged within the preset imaging area, based on the Huygens-Fresnel principle and the time-distance curve equation of the scattered wave, the wave field values ​​of each receiving channel are mapped onto the equivalent offset grid centered on the scattering point to be imaged, thus constructing a common scattering point set. Based on the common scattering point set, velocity scanning analysis is performed to retrieve the root mean square velocity at the scattering point to be imaged; Based on the root mean square velocity and combined with a specified integral migration algorithm, the signal of the common scattering point set is processed by migration imaging to reconstruct the depth image of the hardened layer interface.

[0010] In conjunction with the first aspect, the step of mapping the wavefield values ​​of each receiving channel onto an equivalent offset grid centered on the scattering point to be imaged, and constructing a common scattering point set, includes: Based on the time-distance curve equation of the scattered wave, an equivalent offset distance is introduced to transform the double square root time-distance relationship characterizing the sound wave propagation path into a single square root time-distance relationship. With the scattering point to be imaged as the center, multiple equivalent offset distances are divided to both sides; For each equivalent offset, the time is incremented by a set step size, and the wave field values ​​of each receiving channel that satisfy the double square root time distance relationship are superimposed according to the single square root time distance relationship, thereby forming the signal record of the common scattering point set.

[0011] In conjunction with the first aspect, the steps of performing velocity scanning analysis based on the common scattering point set to deduce the root mean square velocity at the scattering point to be imaged include: For each preset test speed, based on the theoretical hyperbolic trajectory corresponding to the test speed, the signals of all channels within the common scattering point set are coherently superimposed, and the superposition energy is calculated. Based on the superimposed energy generation rate-energy distribution spectrum corresponding to all experimental velocities; Identify the energy peak in the velocity-energy distribution spectrum and determine the energy peak as the root mean square velocity at the scattering point to be imaged.

[0012] In conjunction with the first aspect, the theoretical hyperbolic trajectory is determined by the relationship between the vertical two-way travel time of the common scattering point set and the equivalent offset distance and the experimental velocity.

[0013] In conjunction with the first aspect, the inverse root mean square velocity is used to distinguish the hardened layer region from the substrate material region.

[0014] In conjunction with the first aspect, the specified integral offset algorithm is the Kirchhoff integral offset algorithm; The steps for reconstructing a depth image of the hardened layer interface by performing migration imaging processing on the signal of the common scattering point set based on the root mean square velocity and combined with a specified integral migration algorithm include: Based on the root mean square velocity, calculate the wave field propagation delay from each location in the common scattering point set to the imaging point; Based on the wave field propagation delay, the wave field values ​​of each channel in the common scattering point are phase-corrected and coherently superimposed. By coherently superimposing, the energy of the scattered wave is focused to the corresponding spatial location, forming a depth image of the hardened layer interface.

[0015] In conjunction with the first aspect, during the coherent superposition process, an amplitude weighting factor based on the wave field propagation geometry is introduced. The amplitude weighting factor includes at least one of propagation distance attenuation compensation and interface tilt correction.

[0016] Secondly, embodiments of this application also provide a hardened layer depth ultrasonic scattering imaging device, the device comprising: The acquisition module is used to perform full-matrix data acquisition on the workpiece under test using an ultrasonic phased array probe, and to acquire ultrasonic echo signals under all combinations of transmitting and receiving array elements. The module is used to map the wave field values ​​of each receiving channel onto an equivalent offset grid centered on the scattering point to be imaged within a preset imaging area, based on the Huygens-Fresnel principle and the time-distance curve equation of the scattered wave, to construct a common scattering point set. The inversion module is used to perform velocity scan analysis based on the common scattering point set to invert the root mean square velocity at the scattering point to be imaged; The imaging module is used to perform migration imaging processing on the signal of the common scattering point set based on the root mean square velocity and combined with a specified integral migration algorithm, so as to reconstruct the depth image of the hardened layer interface.

[0017] Thirdly, this application provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor runs the computer program to cause the electronic device to perform the methods described above.

[0018] Fourthly, this application provides a storage medium storing computer program instructions, which are read and executed by a processor to perform the above-described method.

[0019] The embodiments of this invention bring the following beneficial effects: The ultrasonic scattering imaging method, device, electronic device, and storage medium for hardened layer depth provided in this application effectively suppress random noise interference and significantly improve the signal-to-noise ratio by introducing a common scattering point set construction method based on the Huygens-Fresnel principle; through velocity scanning analysis technology based on common scattering point sets, the difference in sound velocity between the hardened layer and the substrate material is accurately inverted, fundamentally solving the measurement error caused by inaccurate sound velocity assumptions in traditional methods; and further combined with a specified offset algorithm, high-resolution imaging of the boundary of complex-shaped hardened layers is achieved, significantly improving the accuracy of hardened layer depth assessment and the clarity of interface identification, providing a more reliable solution for non-destructive testing and evaluation of the quality of heat-treated workpieces.

[0020] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0022] 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.

[0023] Figure 1 A schematic flowchart of a hardened layer depth ultrasonic scattering imaging method provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the acoustic response physical model of a single scattering point according to an embodiment of the present invention; Figure 3 For the purposes of this invention, Figure 2 A schematic diagram illustrating the transformation of the physical model shown; Figure 4 This is a schematic diagram of a physical model describing the propagation path of ultrasound according to an embodiment of the present invention; Figure 5 Embodiments of the present invention Figure 4 The diagram shows a physical model reflecting echoes at different speeds. Figure 6 This is a schematic diagram of a common scattering point set obtained by a hardened layer depth ultrasonic scattering imaging method according to an embodiment of the present invention; Figure 7 This is a schematic diagram of a velocity spectrum obtained by a hardened layer depth ultrasonic scattering imaging method provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of an imaging method for hardened layer depth ultrasonic scattering imaging provided in an embodiment of the present invention; Figure 9 A schematic diagram of an apparatus for a hardened layer depth ultrasonic scattering imaging method provided in an embodiment of the present invention; Figure 10 This is a schematic diagram of the electronic device structure provided in an embodiment of the present invention.

[0024] Figure label: 10 - Acquisition module, 20 - Construction module, 30 - Inversion module, 40 - Imaging module; 130 - Processor, 131 - Memory, 132 - Bus, 133 - Communication interface. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions 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.

[0026] To facilitate understanding of this embodiment, the application scenarios and design concepts of this application embodiment will be briefly introduced below.

[0027] Current ultrasonic backscattering methods for measuring hardened layer depth generally assume that sound waves travel at the same speed in the hardened layer and the substrate, which is inconsistent with reality and leads to measurement errors. Furthermore, traditional methods have poor adaptability to inclined or irregular interfaces, B-scan imaging is greatly affected by noise interference and has low resolution, and the velocity acquisition method is coarse, impacting the accuracy of thickness assessment.

[0028] Based on this, embodiments of this application provide a method, apparatus, electronic device, and storage medium for ultrasonic scattering imaging of hardened layer depth.

[0029] Example 1 This application provides an embodiment of the invention that offers a method for ultrasonic scattering imaging of hardened layer depth, combined with... Figure 1 As shown, the method includes: The S110 uses an ultrasonic phased array probe to perform full matrix data acquisition on the workpiece under test, acquiring ultrasonic echo signals under all combinations of transmitting and receiving array elements.

[0030] S120, for the scattering points to be imaged within the preset imaging area, based on the Huygens-Fresnel principle and the time-distance curve equation of the scattered wave, maps the wave field values ​​of each receiving channel onto an equivalent offset grid centered on the scattering point to be imaged, and constructs a common scattering point set.

[0031] S130, based on the common scattering point set, performs velocity scanning analysis to inversely derive the root mean square velocity at the scattering point to be imaged.

[0032] S140, based on the root mean square velocity and combined with a specified integral migration algorithm, performs migration imaging processing on the signal of the common scattering point set to reconstruct the depth image of the hardened layer interface.

[0033] In step S110, the ultrasonic phased array probe is an ultrasonic probe composed of multiple independent piezoelectric crystals (array elements) arranged in a certain pattern. By controlling the time delay (phase) of each array element emitting or receiving ultrasonic waves, the deflection, focusing, and scanning of the sound beam can be achieved.

[0034] Full-matrix data acquisition is a data acquisition mode. It requires sequentially exciting each element in the array as a transmitter, while all elements (including the transmitting element itself) simultaneously receive the returned echo signals. For a probe containing N elements, N×N sets of independent A-scan signal data will be obtained.

[0035] Step S110 obtains the most comprehensive and richest raw wavefield information of the detection area, and the full matrix data contains information on the propagation of sound waves from all possible paths, which enables the use of software algorithms to achieve focusing at any point and multiple imaging modes in post-processing without the need for repeated hardware scanning.

[0036] In conjunction with the first aspect, step S120 maps the wavefield values ​​of each receiving channel onto an equivalent offset grid centered on the scattering point to be imaged, constructing a common scattering point set, specifically including: S121, based on the time-distance curve equation of the scattered wave, introduces an equivalent offset distance to transform the double square root time-distance relationship characterizing the sound wave propagation path into a single square root time-distance relationship.

[0037] This step is the spatial planning stage for imaging. First, based on the detection requirements, a desired imaging region is defined within the workpiece (e.g., a depth range from 0 mm to 5 mm below the surface). Then, within this region, several scattering points to be imaged are selected at certain lateral and longitudinal intervals (i.e., imaging grid density). These points constitute the potential locations of the hardened layer interface that we ultimately want to reconstruct, serving as the target centers for all subsequent signal processing. In step S121, the continuous physical interface is discretized into a series of specific imaging targets, laying the foundation for the organized mapping of the full matrix data to these specific spatial locations. Understandably, the density of the imaging grid directly determines the spatial resolution of the final image.

[0038] S122, with the scattering point to be imaged as the center, divides into multiple equivalent offset distances to both sides.

[0039] After determining the projection of a series of scattering points onto the x-axis, this step constructs a dedicated data processing coordinate system for each scattering point to be imaged. Centered on the projection point P of the scattering point on the horizontal plane, a series of densely spaced, equally spaced equivalent offset distances are delineated on both sides. These values ​​form a virtual array of receiving points. The grid defines the horizontal coordinates for reconstructing and displaying the signal from the scattering point. Understandably, a denser grid allows for more precise mapping and reconstruction of the signal, thus improving the accuracy of subsequent processing.

[0040] S123, for each equivalent offset, the time domain is incremented by a set step size, and the wave field values ​​of each receiving channel that satisfy the double square root time distance relationship are superimposed according to the single square root time distance relationship, thereby forming the signal record of the common scattering point set.

[0041] Specifically, iterate through each equivalent offset divided in S122. For the current In the time domain, starting from zero and proceeding in steps Δ Increment until the maximum collection time is reached. For each pair ( , Using a predefined formula to define the time interval relationship, all transmit-receive channels satisfying this relationship are found in the full matrix data. Then, these channels are time-separated... All measured wavefield values ​​(signal amplitudes) are summed (coherently superimposed), and the summation result is used as the location of the CSP set. ,time The final signal value.

[0042] In step S120, the Huygens-Fresnel principle is a fundamental principle of wave optics and acoustics. Huygens' principle states that every point on the wavefront can be considered a new secondary wave source; Fresnel adds the idea of ​​coherent superposition of secondary waves. Here, it is used to describe how each grain scattering point on the hardened layer interface can be considered a secondary wave source, and the scattered waves generated are superimposed at the probe array.

[0043] The time-distance curve equation of the scattered wave is a mathematical formula that describes the relationship between the propagation time t of an ultrasonic wave from the emission point S to the scattering point P and then to the receiving point R and the geometric distance between them.

[0044] Equivalent offset is a key mathematical transformation concept. It introduces a virtual "EPE" path (i.e., emitted from a virtual point E, scattered at point P, and returned to the same point E) to the complex "SPR" path, which simplifies the double square root equation of propagation time into a standard hyperbolic form single square root equation, greatly simplifying the calculation.

[0045] The common scattering point set is obtained by remapping the full matrix data. It reorganizes and maps the received channel signals whose sound wave propagation paths pass through the same scattering point P according to the equivalent offset, forming a new dataset dedicated to that scattering point P. Each scattering point to be imaged corresponds to an independent common scattering point set.

[0046] After data acquisition in step S110, the propagation paths of sound waves differ due to the different transmitting or receiving array elements. The core of step S120 lies in applying the Huygens-Fresnel principle, treating the complex interface between the hardened layer and the substrate as composed of countless independent scattering points (such as rough grains). Each scattering point can be considered a source of secondary waves. When the incident ultrasonic wave reaches this interface, these secondary wave sources are excited and emit scattered waves in all directions (including the direction returning to the probe array). Ultimately, the signal received by the probe is the result of the coherent superposition of scattered waves generated by each grain scattering point on the hardened layer interface at the array position. Through the above operations, signals originally belonging to different physical array elements (S, R) but originating from the same scattering point are all extracted and recombined into a CSP dataset centered on that point. The coherent superposition process enhances the effective signal in phase with the theoretical time-distance curve, while random noise is canceled out due to incoherence, thus significantly improving the signal-to-noise ratio. The final generated CSP set has a signal energy of ( , Within the domain, it will exhibit a standard hyperbolic shape, a clear characteristic that is a prerequisite for subsequent high-precision velocity inversion.

[0047] To describe the acoustic response at a single scattering point, we established, as follows: Figure 2The physical model is shown. Ultrasonic waves originate from the transmitting element S, pass through a scattering point P at depth Z, and are finally captured by the receiving element R, where their propagation time is recorded. The calculation formula is:

[0048] However, this equation is a double square root equation, which mathematically corresponds to an irregular hyperboloid. When faced with a large number of scattering points on the interface, these complex hyperboloids are intertwined in the data space, making them difficult to separate. Furthermore, direct solution is computationally expensive and inefficient, posing a major obstacle to subsequent accurate imaging.

[0049] To address the aforementioned challenges, this invention introduces an equivalent offset distance. This is a key mathematical transformation concept. Its core idea is to find a virtual equivalent path, the "EPE," for the real complex propagation path of "SPR" (i.e., emitted from a virtual point E, scattered at point P, and returning to the same point E), such as... Figure 3 As shown, to make the propagation time of the two paths equal, the expression is: .

[0050] Through this transformation, the originally complex double-square-root time-distance equation is simplified into a standard, single-square-root hyperbolic equation, namely:

[0051] in, .

[0052] In this way, one was successfully placed in ( x , In space, it is an irregular hyperboloid, which is transformed into ( , The standard hyperbola problem on the plane achieves dimensionality reduction and standardization of the computational model.

[0053] equivalent offset The trajectory itself is also a hyperbola, calculated directly from the equation shown in the following formula:

[0054] To eliminate the initial preset speed By combining the above formulas to consider the potential impact of dataset construction, a more accurate formula for time interval relationships can be derived (i.e., the preset formula provided in step S123 above): .

[0055] By considering the hardened layer interface as a combination of scattering points, and selecting several scattering point locations to be imaged, their respective common scattering point sets can be obtained, such as... Figure 6 As shown.

[0056] In conjunction with the first aspect, step S130 includes: S131, for each preset test speed, based on the theoretical hyperbolic trajectory corresponding to the test speed, coherently superimpose the signals of all channels within the common scattering point set, and calculate the superposition energy.

[0057] S132, based on the superimposed energy generation rate-energy distribution spectrum corresponding to all test rates.

[0058] S133 identifies the energy peak in the velocity-energy distribution spectrum and determines the energy peak as the root mean square velocity at the scattering point to be imaged.

[0059] In conjunction with the first aspect, the theoretical hyperbolic trajectory is determined by the relationship between the vertical two-way travel time of the common scattering point set and the equivalent offset distance and the experimental velocity.

[0060] First, based on the acoustic properties of the material being tested (e.g., steel), set a reasonable velocity scanning range. For example, start with an initial velocity of 6000 m / s, and gradually increase to 7000 m / s in increments of 50 m / s. Each velocity value (e.g., 6000, 6050, 6100... m / s) represents a test velocity. Then, for each test velocity, based on the vertical two-way travel time of the common scattering point set... and equivalent offset Calculate the theoretical hyperbolic locus:

[0061] in, Indicates in The root mean square velocity at that location.

[0062] Subsequently, the wave field values ​​of all channels in the co-scattering point set are aligned along this theoretical hyperbolic trajectory and coherent superposition is performed, and the total superposition energy corresponding to this velocity is recorded.

[0063] In step S132, each test velocity is correlated with its corresponding superimposed energy value to construct a two-dimensional or three-dimensional distribution map with the test velocity as the horizontal axis, the vertical two-way travel time t0 (or corresponding depth) as the vertical axis, and the superimposed energy as the intensity (usually represented by color or grayscale). This is the velocity-energy distribution spectrum, which transforms discrete velocity-energy data pairs into a comprehensive spectrum, making it clear which velocity at different depths elicits the strongest signal response. On this distribution spectrum, scattering points at the interface between the hardened layer and the matrix will form concentrated high-energy clusters at their corresponding sound velocities. These energy clusters directly reflect the sound velocity characteristics of the hardened layer at the interface, thus clearly revealing the layered structure and sound velocity differences of the material.

[0064] Finally, in step S133, the energy maxima at each depth (t0) or within each energy cluster are identified on the velocity-energy distribution spectrum generated in S132 using algorithms (such as global maximum search, edge detection, etc.) or manual interpretation. The specific velocity value corresponding to this energy peak is determined as the root mean square velocity of the medium at the location of the scattering point to be imaged. Understandably, by identifying different velocity values, the hardened layer (high velocity) and the substrate (low velocity) can be clearly distinguished. The depth of the hardened layer interface can then be determined by the location of the scattering point belonging to the high-velocity region, thus achieving a precise and quantitative assessment of the hardened layer thickness.

[0065] Understandably, in existing technologies, the sound velocity used for ultrasonic testing of hardened layer depth is often obtained through a simplified method of "total thickness divided by total duration." This method is based on a fundamental assumption that contradicts reality: that ultrasonic waves propagate at the same speed in the hardened layer and the parent substrate, which have vastly different properties. This assumption ignores the significant impact of changes in the material's microstructure caused by heat treatment on acoustic properties, resulting in a calculated sound velocity that is a "mixed average" that does not reflect the true characteristics of any layer. When this inaccurate velocity value is used for depth calculation, it introduces a non-negligible systematic error, severely limiting the accuracy of hardened layer thickness assessment.

[0066] To address this fundamental deficiency, this invention utilizes the physical nature of sound wave propagation: reflected waves from the same scattering point have a time-distance relationship at the common scattering point set that follows a standard hyperbola, the curvature of which is uniquely determined by the actual velocity of the medium layer at that point.

[0067] Specifically, the hyperbolic time-distance relationship of traditional common-center gathers can be described by the following formula:

[0068]

[0069] in, For reflection time, When traveling on a round trip under the self-motivation and self-reliant framework, It is half the distance between the excitation element and the receiving element. That is, the velocity of the horizontal medium layer. This is the normal time difference.

[0070] It is evident that traditional methods attempt to directly read the reflection time. Or calculate time difference To solve for the velocity of the horizontal medium layer However, this is extremely difficult in practice because the starting point of the reflected wave is easily affected by noise and attenuation, making it difficult to identify accurately.

[0071] This application cleverly circumvents this challenge. It does not rely on precise picking of individual reflection times, but rather utilizes the statistical characteristics of the entire waveform. For a fixed set of common scattering points (its... and (Given) an arbitrary test speed This uniquely establishes a theoretical hyperbolic locus. For example... Figure 4 As shown, the ultrasonic phased array received three sets of data: element 1 transmitting and element 5 receiving; element 2 transmitting and element 4 receiving; and element 3 self-excited and self-received. Because the centers of the three sets of data (transmit / receive) are aligned, they form a common-center dataset, as shown by the hyperbola. Figure 5 As shown in N, and by Figure 5 It can be seen that once the (transmit / receive) array elements are determined, the formula becomes... In addition to speed value All other parameters have been determined.

[0072] By substituting different speeds into the above equation, when... When less than the actual speed (e.g.) Overcorrection causes the hyperbola to curve upwards; when When the speed is greater than the actual speed (e.g.) Insufficient correction causes the hyperbola to sag; only when When equal to the actual speed (e.g.) Only when the correction is just right can all signals be superimposed in phase.

[0073] Therefore, step S130 of this invention systematically selects a series of test speeds and calculates the coherent superposition energy of all signals on their corresponding hyperbolic trajectories. The superposition energy reaches its maximum value only when the test speed equals the true velocity of the medium. By identifying this energy peak, the root mean square velocity at the current scattering point can be accurately retrieved. This speed solution shifts from relying on "precise reading of a single time point" to utilizing "consistent matching of the overall waveform," which not only greatly improves the anti-interference capability but, more importantly, can accurately reveal the sound velocity difference between the hardened layer and the substrate material, providing the most critical accurate acoustic parameters for subsequent sub-millimeter-level accuracy assessment of the hardened layer thickness.

[0074] In conjunction with the first aspect, the theoretical hyperbolic trajectory is determined by the relationship between the vertical two-way travel time of the common scattering point set and the equivalent offset distance and the experimental velocity.

[0075] The theoretical hyperbolic trajectory used for velocity scanning is not a fixed path, but a dynamically defined functional relationship based on three key parameters. These three parameters are directly derived from the preprocessing steps of this invention, ensuring the accuracy and consistency of the velocity analysis.

[0076] In conjunction with the first aspect, the inverse root mean square velocity is used to distinguish the hardened layer region from the substrate material region.

[0077] The root mean square velocity derived by this invention has one of its core applications: providing a direct and reliable physical criterion for accurately distinguishing between the hardened layer and the substrate material. This capability is rooted in a fundamental principle of materials science: there is an inherent and measurable correlation between the heat treatment state of a material and its acoustic properties. For example... Figure 7 The velocity spectrum shown and Figure 8 As shown in the depth spectrum, this invention, through velocity scanning analysis in step S130, can clearly visualize and quantify this difference in sound velocity. In the velocity spectrum, scattering points at the interface between the hardened layer and the substrate form concentrated energy clusters in both the higher and lower sound velocity ranges. By identifying these two separate energy clusters, the system can automatically and accurately classify each scattering point to its corresponding material region. Thus, by directly identifying the transition boundary from the high-speed to the low-speed region, the interface position between the hardened layer and the substrate can be determined with extreme precision. Based on the accurately inverted sound velocity and clearly distinguished material interfaces, the thickness assessment results provided by this invention are no longer affected by errors in velocity assumptions, fundamentally improving their reliability and accuracy.

[0078] In conjunction with the first aspect, the integral offset algorithm is specified as the Kirchhoff integral offset algorithm. Step S140 includes: S141, based on the root mean square velocity, calculate the wave field propagation delay from each location in the common scattering point set to the imaging point.

[0079] S142, based on the wave field propagation delay, the wave field values ​​of each channel in the common scattering point are phase corrected and coherently superimposed.

[0080] S143, through coherent superposition, focuses the energy of the scattered wave to the corresponding spatial location, forming a depth image of the hardened layer interface.

[0081] This application uses the Kirchhoff integral migration algorithm as the final imaging method to achieve high-resolution imaging. The algorithm is based on a rigorous solution to the wave equation. Its core idea is wave field backtracking: the wave field received by the probe on the surface, which has been extended over time, is "reverse-propagated" back into the medium through mathematical calculation, so that it is refocused at the original interface position where scattering occurred, thereby restoring the true spatial shape of the interface.

[0082] The Kirchhoff integral solution of the wave equation is expressed as follows:

[0083] in, This represents the direction of the outward normal to surface S. For a certain point In time Wave field value at that location, The distance from the input point to the output point. The root mean square velocity is represented by []. [] represents the delay symbol, such as [ This represents a point. exist A delay in time.

[0084] To apply the theory to full-matrix data, the formula was adaptively simplified and transformed, resulting in an imaging formula suitable for this invention:

[0085] in, For the imaging results, The location of the common scattering point set. The input wavefield representing the common scattering point set, This is the equivalent offset interval. For the actual measured wave field The result obtained by differentiating with respect to time, The tilt factor is determined in this paper by the angle between the location of the common scattering point set and the location of each equivalent offset.

[0086] In the formula The physical significance of this term lies in highlighting the transient characteristics of the wave field, and combining it with... and The (propagation distance) implicitly represents the propagation path, which together achieves the understanding of... Accurate delay calculation of the input wave field. This step ensures that signals from the same scattering point are corrected to the same phase before superposition.

[0087] The results are obtained by superimposing all the signals after the above corrections and weighting. This represents the energy of the scattered wave at the imaging point. When the calculated point is exactly located at the actual scattering point, all signals are superimposed in phase, and the energy... The maximum value is obtained; otherwise, the energy is weak. By traversing all preset imaging points and mapping the energy values ​​to their corresponding spatial locations, a well-focused hardened layer depth image is finally formed.

[0088] In conjunction with the first aspect, during the coherent superposition process, an amplitude weighting factor based on the wave field propagation geometry is introduced. The amplitude weighting factor includes at least one of propagation distance attenuation compensation and interface tilt correction.

[0089] Understandably, in the coherent superposition process of step S142, this invention does not perform simple signal summation, but instead introduces an amplitude weighting factor based on the geometric relationship of wavefield propagation. This processing is a core component of Kirchhoff integral migration theory, and its purpose is to compensate for physical propagation effects, thereby obtaining amplitude information that more closely approximates the true scattering characteristics and improving imaging fidelity and resolution. This amplitude weighting factor mainly includes the following two types of compensation: propagation distance attenuation compensation and interface tilt correction.

[0090] The principle of propagation distance attenuation compensation is that when ultrasound propagates in a medium, its wavefront gradually expands, causing the sound wave energy to disperse as the propagation distance r increases. The energy per unit area (i.e., amplitude) will attenuate according to the law of 1 / r. If no compensation is made, the contribution of the receiving channel signal far from the imaging point in the superposition will be unreasonably weakened. By introducing the 1 / r term in formula (9), it is ensured that the amplitude of all signals from the same scattering point but with different propagation paths is normalized to the same reference before superposition, making the contribution of near and far channels to the final imaging result more balanced and avoiding distortion of imaging brightness.

[0091] The technical principle of interface tilt correction is that when the interface of the hardened layer is not perpendicular to the incident direction of the ultrasonic wave, i.e., when there is a tilt angle θ, the receiving efficiency of the probe will be affected. The tilt factor describes the geometric relationship between the direction of the scattering interface and the observation direction (i.e., the direction of wave field propagation). According to the acoustic principle, the amplitude of the reflected or scattered signal is proportional to cosθ, where θ is the angle between the normal of the imaging point and the observation direction. In formula (9), the interface tilt correction is achieved by introducing the cosθ term, which corrects the amplitude reduction caused by the interface tilt, making the brightness of the tilted interface in the imaging result comparable to that of the horizontal interface, and more realistically reflecting the reflection intensity of the interface; it helps to achieve better lateral focusing at the tilted interface, making the interface imaging sharper and clearer, and avoiding energy diffusion or artifacts caused by inaccurate amplitude.

[0092] Secondly, embodiments of this application also provide a hardened layer depth ultrasonic scattering imaging device, combined with Figure 9 As shown, the device includes: an acquisition module 10, a construction module 20, an inversion module 30, and an imaging module 40.

[0093] The acquisition module 10 is used to perform full matrix data acquisition on the workpiece under test using an ultrasonic phased array probe, and to acquire ultrasonic echo signals under all combinations of transmitting and receiving array elements; The construction module 20 is used to map the wave field values ​​of each receiving channel onto an equivalent offset grid centered on the scattering point to be imaged within a preset imaging area, based on the Huygens-Fresnel principle and the time-distance curve equation of the scattered wave, to construct a common scattering point set. The inversion module 30 is used to perform velocity scanning analysis based on the common scattering point set to invert the root mean square velocity at the scattering point to be imaged; The imaging module 40 is used to perform migration imaging processing on the signal of the common scattering point set based on the root mean square velocity and combined with a specified integral migration algorithm to reconstruct the depth image of the hardened layer interface.

[0094] By introducing a common scattering point set construction method based on the Huygens-Fresnel principle, random noise interference was effectively suppressed, significantly improving the signal-to-noise ratio. Through velocity scanning analysis based on common scattering point sets, the sound velocity difference between the hardened layer and the substrate material was accurately inverted, fundamentally solving the measurement error caused by inaccurate sound velocity assumptions in traditional methods. Furthermore, by combining the Kirchhoff integral migration algorithm, high-resolution imaging of the boundary of complex-shaped hardened layers was achieved, significantly improving the accuracy of hardened layer depth assessment and the clarity of interface identification, providing a more reliable solution for non-destructive testing and evaluation of heat-treated workpiece quality.

[0095] Thirdly, embodiments of this application provide an electronic device, combined with Figure 10As shown, the electronic device includes a memory 131 and a processor 130. The memory 131 stores a computer program, and the processor 130 runs the computer program to make the electronic device perform the above-described method.

[0096] Furthermore, combined Figure 10 The electronic device shown also includes a bus 132 and a communication interface 133, with the processor 130, the communication interface 133 and the memory 131 connected via the bus 132.

[0097] The memory 131 may include high-speed random access memory (RAM) and may also include non-volatile memory, such as at least one disk storage device. Communication between this system network element and at least one other network element is achieved through at least one communication interface 133 (which can be wired or wireless), such as the Internet, wide area network, local area network, metropolitan area network, etc. The bus 132 may be an ISA bus, PCI bus, or EISA bus, etc. The bus can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 10 The symbol is represented by a single double-headed arrow, but this does not mean that there is only one bus or one type of bus.

[0098] Processor 130 may be an integrated circuit chip with signal processing capabilities. In implementation, each step of the above method can be completed by the integrated logic circuitry in the hardware of processor 130 or by instructions in software form. Processor 130 may be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), etc.; it may also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this invention. The general-purpose processor may be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this invention can be directly manifested as execution by a hardware decoding processor, or execution by a combination of hardware and software modules in the decoding processor. The software module can reside in a mature storage medium in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, or registers. This storage medium is located in memory 131, and processor 130 reads the information in memory 131 and, in conjunction with its hardware, completes the steps of the method described in the foregoing embodiments.

[0099] Fourthly, embodiments of this application provide a readable storage medium storing computer program instructions, which are read and executed by a processor to perform the above-described method.

[0100] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and apparatus described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0101] Furthermore, in the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0102] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0103] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0104] Finally, it should be noted that the above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for ultrasonic scattering imaging of hardened layer depth, characterized in that, The method includes: An ultrasonic phased array probe is used to perform full matrix data acquisition on the workpiece under test, and to obtain ultrasonic echo signals under all combinations of transmitting and receiving array elements. For the scattering points to be imaged within the preset imaging area, based on the Huygens-Fresnel principle and the time-distance curve equation of the scattered wave, the wave field values ​​of each receiving channel are mapped onto an equivalent offset grid centered on the scattering point to be imaged, thus constructing a set of common scattering points. Based on the common scattering point set, a velocity scan analysis is performed to retrieve the root mean square velocity at the scattering point to be imaged; Based on the root mean square velocity and combined with a specified integral migration algorithm, the signal of the common scattering point set is processed by migration imaging to reconstruct the depth image of the hardened layer interface.

2. The method according to claim 1, characterized in that, The step of mapping the wavefield values ​​of each receiving channel onto an equivalent offset grid centered on the scattering point to be imaged, and constructing a common scattering point set, includes: Based on the aforementioned time-distance curve equation of the scattered wave, an equivalent offset distance is introduced to transform the double square root time-distance relationship characterizing the sound wave propagation path into a single square root time-distance relationship. With the scattering point to be imaged as the center, multiple equivalent offset distances are divided to both sides; For each equivalent offset distance, the time domain is incremented by a set step size, and the wave field values ​​of each receiving channel that satisfy the double square root time distance relationship are superimposed according to the single square root time distance relationship to form the signal record of the common scattering point set.

3. The method according to claim 1, characterized in that, The step of performing velocity scanning analysis based on the common scattering point set to deduce the root mean square velocity at the scattering point to be imaged includes: For each preset test speed, based on the theoretical hyperbolic trajectory corresponding to the test speed, the signals of all channels within the common scattering point set are coherently superimposed, and the superposition energy is calculated. Based on the superimposed energy generation rate-energy distribution spectrum corresponding to all experimental velocities; Identify the energy peak in the velocity-energy distribution spectrum and determine the energy peak as the root mean square velocity at the scattering point to be imaged.

4. The method according to claim 3, characterized in that, The theoretical hyperbolic trajectory is determined by the relationship between the vertical two-way travel time and equivalent offset of the common scattering point set and the experimental velocity.

5. The method according to claim 3, characterized in that, The inverse root mean square velocity is used to distinguish the hardened layer region from the substrate material region.

6. The method according to claim 1, characterized in that, The specified integral offset algorithm is the Kirchhoff integral offset algorithm; The steps of reconstructing a depth image of the hardened layer interface by performing migration imaging processing on the signal of the common scattering point set based on the root mean square velocity and in conjunction with a specified integral migration algorithm include: Based on the root mean square velocity, calculate the wave field propagation delay from each location of the common scattering point set to the imaging point; Based on the wave field propagation delay, the wave field values ​​of each channel in the common scattering point set are phase-corrected and coherently superimposed. Through coherent superposition, the scattered wave energy is focused to the corresponding spatial location, forming a depth image of the hardened layer interface.

7. The method according to claim 3 or 6, characterized in that, In the coherent superposition process, an amplitude weighting factor based on the wave field propagation geometry is introduced, which includes at least one of propagation distance attenuation compensation and interface tilt correction.

8. A hardened layer depth ultrasonic scattering imaging device, characterized in that, The device includes: The acquisition module is used to perform full-matrix data acquisition on the workpiece under test using an ultrasonic phased array probe, and to acquire ultrasonic echo signals under all combinations of transmitting and receiving array elements. The module is used to map the wave field values ​​of each receiving channel onto an equivalent offset grid centered on the scattering point to be imaged within a preset imaging area, based on the Huygens-Fresnel principle and the time-distance curve equation of the scattered wave, to construct a common scattering point set. The inversion module is used to perform velocity scanning analysis based on the common scattering point set to invert the root mean square velocity at the scattering point to be imaged; The imaging module is used to perform offset imaging processing on the signal of the common scattering point set based on the root mean square velocity and in combination with a specified integral offset algorithm, so as to reconstruct a depth image of the hardened layer interface.

9. An electronic device, characterized in that, The electronic device includes a memory and a processor, the memory storing a computer program and the processor running the computer program to cause the electronic device to perform the method of any one of claims 1 to 7.

10. A storage medium, characterized in that, The storage medium stores computer program instructions, which, when read and executed by a processor, perform the method described in any one of claims 1 to 7.

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