CN113552218B - Array ultrasonic signal amplitude and phase characteristic weighting-based defect qualitative detection method - Google Patents
Array ultrasonic signal amplitude and phase characteristic weighting-based defect qualitative detection method Download PDFInfo
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Abstract
A defect qualitative detection method based on array ultrasonic signal amplitude and phase characteristic weighting belongs to the technical field of nondestructive testing. The method adopts a detection system consisting of a phased array ultrasonic detector, a phased array ultrasonic probe and a wedge block, and acquires full matrix data of 21 mode waves including direct, half-span and full-span modes; according to each reconstruction point of the area to be detected, amplitude and phase characteristics of each mode wave in the array ultrasonic signal are considered at the same time, time delay superposition processing is carried out on 21 mode waves respectively, and strongest energy is screened; on the basis, phase information is extracted for weighted imaging, and the profile characteristics of the defect to be detected are given, so that the qualitative identification of the defect in the elastic anisotropic material and the isotropic material is realized. The method can carry out contour reconstruction on unknown area type defects and unknown volume type defects, the defect interpretation is visual, the qualitative and quantitative detection results are accurate, and the method has wide engineering application prospect.
Description
Technical Field
The invention relates to a defect qualitative detection method based on array ultrasonic signal amplitude and phase characteristic weighting, and belongs to the technical field of nondestructive detection.
Background
Qualitative defect detection is a major concern in the field of non-destructive inspection. For surface defects, visual inspection or penetration inspection can be used to distinguish types; for internal defects, radiographic inspection or ultrasonic inspection may be employed. The ray detection can intuitively present the morphological characteristics of the defects, but cannot give the depth information of the defects, and is limited when the thick-wall structure is detected. Compared with the prior art, the ultrasonic detection has higher detection sensitivity and penetrating power and wide application range, and realizes accurate quantification and positioning of the defects while identifying the property information of the defects.
The conventional ultrasonic detection is mainly based on the information such as waveform, amplitude and the like of an A scanning signal to comprehensively judge the defect property, and is greatly influenced by the coupling condition, human factors and structural noise caused by materials (Zhengzhongxing et al. qualitative of defects in the third special ultrasonic detection. nondestructive detection. 1994,16(1): 24-27). Subsequently, phased array ultrasonic inspection technology was developed, and based on the quantitative relationship between the amplitude ratio of the signals at the upper and lower end points of the defect and the aspect ratio of the defect in the scanned image, it could be determined whether the defect approaches an area type defect or a volume type defect (Nardoni G, et al. Experimental determination of characterization of defect between volume and plane defects by means of mediums of ultrasonic pulse-echo/phase-echo detection of substrate-echo on the ratio of defect between diffusion and amplification, instrument-Non-depletion Testing and conditioning Monitoring 2012,54(4): 221-. However, phased array ultrasonic inspection often only gives area type defect endpoint information, and is easily misjudged as a plurality of volume type defects. On the basis, various signal post-processing methods are developed, and the defect type is accurately judged by presenting the area type defect outline characteristics. The reverse time migration method has a good reconstruction effect on volume type defects and area type defects, but the imaging effect is easily influenced by noise, and the calculation efficiency is low (creep cutting points and the like, reverse time migration ultrasonic imaging of longitudinal banded fissure morphology, physics report 2014,63(15): 239-. The full focus method can characterize the area type defect profile features with the orientation approximately perpendicular to the main sound beam direction. Considering the orientation change of the area-type defect, a multimode full focusing method can be applied, and mode waves under different sound beam paths are utilized to reconstruct the defect profile and qualitatively distinguish the defect, but the mode wave selection depends on certain defect prior information (JinS J, et al. summary of morphology characteristics for regular cracks with multi-mode total focusing method. far East NDT New Technology & Application form 2019.Qingdao, China). In order to solve the problem, the full-mode full-focusing method realizes the profile reconstruction of the cracks with different orientations by selecting the strongest energy signals in 21 mode waves including 3 direct modes, 8 half-spans and 10 full-spans modes point by point and carrying out time-delay superposition (Kinshige, and the like, crack ultrasonic imaging quantitative detection based on the full-mode full-focusing method, instrumental science, 2021,42(1): 183-190). It should be noted that this method only utilizes the amplitude characteristics of the array ultrasonic signals, resulting in limited applicability by the material and difficulty in achieving qualitative detection of defects in elastic anisotropic materials.
Disclosure of Invention
The invention provides a defect qualitative detection method based on array ultrasonic signal amplitude and phase characteristic weighting, and aims to solve the problem of difficulty in qualitative detection of defects in elastic anisotropic materials.
The technical scheme adopted by the invention is as follows: a detection system consisting of a phased array ultrasonic detector, a phased array ultrasonic probe and a wedge block is adopted to acquire full matrix data of 21 mode waves including 3 direct modes, 8 half-span modes and 10 full-span modes; aiming at each reconstruction point of the area to be detected, simultaneously considering the amplitude and phase characteristics of each mode wave in the array ultrasonic signal, respectively carrying out delay superposition processing on 21 mode waves and screening the strongest energy; on the basis, phase information is extracted for weighted imaging, and the outline characteristics of the defect to be detected are given, so that the qualitative identification of the defect in the elastic anisotropic material and the isotropic material is realized; the method comprises the following steps:
(a) phased array ultrasonic inspection parameter selection
Selecting the frequency and array elements of the phased array ultrasonic probe and a matched wedge block according to the material, shape and size information of a sample to be detected;
(b) full matrix data acquisition
Connecting the phased array ultrasonic probe, wedge and phased array ultrasonic detector selected in step (a), the acquisition comprising n 2 The full matrix data of the A scanning signals, wherein n is the number of array elements of the phased array ultrasonic probe;
wherein, the signal transmitted by the ith array element and received by the jth array element is defined as S ij () Wherein i is more than or equal to 1 and less than or equal to n; j is more than or equal to 1 and less than or equal to n;
(c) reconstruction region meshing
The reconstruction area of the sample to be detected is meshed, each mesh node is an image reconstruction point, and the coordinate of the image reconstruction point P is defined as (a, b);
(d) delayed superposition processing of mode waves
In the imaging, a direct mode, a half-span mode and a full-span mode are utilized to count 21 mode waves with different propagation paths; extracting signal amplitude characteristics, and regarding the k-th mode wave, the time delay superposition imaging amplitude I at the P point k (a, b) is given by formula (1), wherein 1. ltoreq. k.ltoreq.21
In the formula, t ij-k (a, b) represents the time used by the ith array element excitation signal after propagating to the point P (a, b) and being received by the jth array element under the kth mode wave, and can be obtained by calculation according to Fermat's theorem;
time-delay superposition imaging amplitude I from 21 mode waves k The strongest energy is screened from (a, b), namely the reconstruction amplitude I of the point P A (a,b)
(e) Weighting processing based on phase characteristics
For each signal S in the full matrix data in step (b) ij () Hilbert transformation is performed by using Euler's formula to obtain phase information
Where H () is the Hilbert transform, | H | is the signal magnitude,
is the signal phase angle;
constructing a weighting factor C of the kth mode wave at the P point by using the extracted signal phase angle k (a, b) as shown in formula (4)
Wherein var is the standard deviation;
subsequently, the reconstructed amplitude I in step (d) is applied with equation (5) in combination with the weighting factor A (a, b) weighting to obtain a new amplitude I (a, b) of the point, thereby realizing noise suppression;
(f) qualitative and quantitative defect detection
Repeating the processes of the steps (d) - (e), and performing delay superposition and weighting processing on the reconstruction area point by point to obtain a reconstruction image; judging whether the defect contour features in the image are volume type defects or area type defects according to the defect contour features in the image, and realizing qualitative detection; and finally, determining the depth of the defect, and the size and the inclination angle of the area type defect according to the contour presenting result.
The invention has the beneficial effects that: the qualitative defect detection method based on the weighting of the amplitude and phase characteristics of the array ultrasonic signals utilizes a set of phased array probe wedge block combination, and simultaneously considers the amplitude and phase characteristics of the array ultrasonic signals, so that the qualitative identification of unknown area type defects and unknown volume type defects in elastic anisotropic and isotropic materials is realized. Meanwhile, the algorithm related to the method can be embedded into the phased array ultrasonic detector, the defect interpretation is visual, the qualitative and quantitative detection results are accurate, and the method has high engineering application and popularization values.
Drawings
The invention is further illustrated with reference to the figures and examples.
Fig. 1 is a schematic diagram of an ultrasonic inspection system employed.
Fig. 2A and 2B are schematic diagrams of a stainless steel test block in which a crack (fig. 2A) and an adjacent through hole (fig. 2B) are processed.
Fig. 3A and 3B are imaging results of a crack (fig. 3A) and a hole (fig. 3B) when only the amplitude features of each mode wave in the array signal are considered.
Fig. 4A and 4B are the results of weighted imaging processing of a crack (fig. 4A) and a hole (fig. 4B) while simultaneously considering the amplitude and phase characteristics of each mode wave in the array signal.
Detailed Description
The following further describes a specific embodiment of the present invention with reference to the drawings and technical solutions.
It is to be understood that the appended drawings are not to scale, but are merely drawn with appropriate simplifications to illustrate various features of the basic principles of the invention. Specific design features of the invention disclosed herein, including, for example, specific dimensions, orientations, locations, and configurations, will be determined in part by the particular intended application and use environment.
The qualitative defect detection method based on the weighted imaging processing adopts an ultrasonic detection system as shown in figure 1, wherein the ultrasonic detection system comprises a phased array ultrasonic detector, a phased array ultrasonic probe and an inclined organic glass wedge block. The specific detection and processing steps are as follows:
(a) the tested test block is a stainless steel test block with the thickness of 40mm, and cracks with the center depth of 24mm, the length of 4mm and the orientation angle of 45 degrees (the vertical direction is 0 degree, and the clockwise direction is positive) are processed in the test block 1; the test block 2 was processed with adjacent through holes having a diameter of 1mm, a center-to-center distance of 4mm, center depths of 22.6mm and 25.4mm, respectively, and a center orientation angle of 45 °, and the center depth of the connecting line thereof was 24.0mm, as shown in fig. 2.
(b) A phased array ultrasonic detector is utilized, a phased array probe with the center frequency of 5MHz and 64 array elements is matched with a 45-degree wedge block to detect a test block, wherein the height of a first array element of the probe is 18.82mm, the sampling frequency is 100MHz, the longitudinal wave sound velocity of the wedge block is 2330m/s, the transverse wave sound velocity of the test block is 3230m/s, and the longitudinal wave sound velocity is 5900 m/s.
(c) And acquiring signals of the tested block by using a full matrix capture function of the phased array ultrasonic detector, obtaining an A scanning signal matrix containing different mode waves, and exporting the A scanning signal matrix in a data text form.
(d) A rectangular coordinate system is established and the detection area is divided into 80 × 80 rectangular grids.
(e) FIG. 3 shows the results of the imaging of cracks and holes when only the amplitude features of the modes in the array signal are considered. Obviously, the stainless steel test block structure is noisy, and it is difficult to accurately identify the defect properties from the image and perform quantitative analysis.
(f) On the basis, phase information of each signal in the full matrix data is extracted, and a weighting factor is constructed. Subsequently, the weighted image processing is performed on the image shown in fig. 3, and the result of the weighted image processing for obtaining cracks and holes is shown in fig. 4. Obviously, the defect types can be clearly and intuitively identified, and the signal to noise ratio is higher. Quantitative analysis can obtain quantitative results of the crack length, the orientation angle and the center depth of 4.46mm, 45.9 degrees and 24.28mm respectively; quantitative results of the center-to-center spacing of the through holes, the center depth of the connecting line, and the center orientation angle were 3.96mm, 23.90mm, and 45.0 °, respectively. The method realizes the qualitative detection of the unknown area type defects and the unknown volume type defects of different orientations in the anisotropic material, has small quantitative and positioning errors, and meets the engineering requirements.
The above description of exemplary embodiments has been presented only to illustrate the technical solution of the invention and is not intended to be exhaustive or to limit the invention to the precise form described. Obviously, many modifications and variations are possible in light of the above teaching to those skilled in the art. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to thereby enable others skilled in the art to understand, implement and utilize the invention in various exemplary embodiments and with various alternatives and modifications. It is intended that the scope of the invention be defined by the following claims and their equivalents.
Claims (1)
1. The defect qualitative detection method based on array ultrasonic signal amplitude and phase characteristic weighting adopts a detection system consisting of a phased array ultrasonic detector, a phased array ultrasonic probe and a wedge block to acquire full matrix data of 21 mode waves including direct, half-span and full-span modes; the method is characterized in that for each reconstruction point of a region to be detected, the amplitude and phase characteristics of each mode wave in an array ultrasonic signal are considered at the same time, and 21 mode waves are subjected to delay superposition processing and screened for strongest energy; extracting phase information to perform weighted imaging, and giving out the profile characteristics of the defect to be detected, thereby realizing the qualitative identification of the defect in the elastic anisotropic material and the isotropic material; the method comprises the following steps:
(a) phased array ultrasonic inspection parameter selection
Selecting the frequency and array elements of the phased array ultrasonic probe and a matched wedge block according to the material, shape and size information of a sample to be detected;
(b) full matrix data acquisition
Connecting the phased array ultrasonic probe, wedge and phased array ultrasonic detector selected in step (a), the acquisition comprising n 2 The full matrix data of the A scanning signals, wherein n is the number of array elements of the phased array ultrasonic probe;
wherein, the signal transmitted by the ith array element and received by the jth array element is defined as S ij () Wherein i is more than or equal to 1 and less than or equal to n; j is more than or equal to 1 and less than or equal to n;
(c) reconstruction region meshing
The reconstruction area of the sample to be detected is meshed, each mesh node is an image reconstruction point, and the coordinate of the image reconstruction point P is defined as (a, b);
(d) mode wave delay superposition processing
In the imaging, a direct mode, a half-span mode and a full-span mode are utilized to count 21 mode waves with different propagation paths; extracting signal amplitude characteristics, and regarding the k-th mode wave, the time delay superposition imaging amplitude I at the P point k (a, b) is given by formula (1), wherein 1. ltoreq. k.ltoreq.21
In the formula, t ij-k (a, b) represents the time used by the ith array element excitation signal after propagating to the point P (a, b) and being received by the jth array element under the kth mode wave, and can be obtained by calculation according to Fermat's theorem;
time-delay superposition imaging amplitude I from 21 mode waves k Screening the strongest energy in (a, b), namely the reconstruction amplitude I of the point P A (a,b)
(e) Weighting based on phase characteristics
For each signal S in the full matrix data in step (b) ij () Hilbert transformation is performed by using Euler's formula to obtain phase information
Where H () is the Hilbert transform, | H | is the signal magnitude,
is the signal phase angle;
constructing a weighting factor C of the kth mode wave at the P point by using the extracted signal phase angle k (a, b) as shown in formula (4)
Wherein var is the standard deviation;
subsequently, combining the weighting factor, using equation (5) to pair the reconstructed amplitude I in step (d) A (a, b) weighting to obtain a new amplitude I (a, b) of the point, thereby realizing noise suppression;
(f) qualitative and quantitative defect detection
Repeating the processes of the steps (d) to (e), and carrying out time-delay superposition and weighting processing on the reconstruction area point by point to obtain a reconstruction image; judging whether the defect contour characteristics in the image are volume type defects or area type defects according to the defect contour characteristics in the image, and realizing qualitative detection; and finally, determining the depth of the defect, and the size and the inclination angle of the area type defect according to the contour presenting result.
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