阅读说明：本技术 一种高效率激光超声扫描成像检测和超声数据处理的方法 (High-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing method ) 是由 戴挺 贾晓健 顾栩涵 郭魏 张涛 童蔚苹 于 2019-10-16 设计创作，主要内容包括：本发明涉及一种高效率激光超声扫描成像检测和超声数据处理的方法,该方法包括由激光器、扫描振镜和振镜控制卡组成的激光超声检测器；由超声波探测器、信号放大器和数据采集卡组成的数据采集器；由计算机组成的信息处理器；主要步骤为：通过计算机生成工件待检测区域的快速扫描路径并计算出激光器重复频率和数据采集频率；由激光器发射激光,并通过扫描振镜完成激光在带检测区域的扫描；由超声波探测器采集超声信号并传送至计算机中；计算机根据采集到的超声信号,经过可视化处理,还原超声波与材料表面缺陷相互作用的动态过程。(The invention relates to a high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing method, which comprises a laser ultrasonic detector consisting of a laser, a scanning galvanometer and a galvanometer control card; the data acquisition unit consists of an ultrasonic detector, a signal amplifier and a data acquisition card; an information processor composed of a computer; the method mainly comprises the following steps: generating a rapid scanning path of a region to be detected of a workpiece through a computer and calculating the repetition frequency of a laser and the data acquisition frequency; laser is emitted by a laser device, and the scanning of the laser in a detection area is completed through a scanning galvanometer; collecting ultrasonic signals by an ultrasonic detector and transmitting the ultrasonic signals to a computer; and the computer performs visual treatment according to the acquired ultrasonic signals to restore the dynamic process of interaction between the ultrasonic waves and the material surface defects.)

1. The utility model provides a realize high efficiency laser ultrasonic scanning formation of image detection and processing apparatus of ultrasonic data to shallow top layer of metal, includes to detect the work piece, its characterized in that: the processing device comprises a laser ultrasonic detector, a data acquisition unit and an information processor; the laser ultrasonic detector is arranged above a workpiece to be detected, a data acquisition unit is arranged on the workpiece to be detected, and the laser ultrasonic detector and the data acquisition unit are both connected with the information processor; the information processor is a computer.

2. The device for realizing high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing on the metal superficial layer according to claim 1, is characterized in that: the laser ultrasonic detector comprises a laser and a scanning galvanometer; the laser and the scanning galvanometer are connected with a computer, and the scanning galvanometer is arranged above a workpiece to be detected; the data acquisition unit comprises an ultrasonic detector and a signal amplifier; the ultrasonic detector is arranged on the workpiece to be detected and is connected with the computer through the signal amplifier.

3. The device for realizing high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing on the metal superficial layer according to claim 2, is characterized in that: the laser ultrasonic detector also comprises a galvanometer control card, and the galvanometer control card is installed in a computer.

4. The device for realizing high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing on the metal superficial layer according to claim 2, is characterized in that: the data acquisition unit also comprises a data acquisition card which is arranged in the computer.

5. The device for realizing high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing on the metal superficial layer according to claim 4, is characterized in that: the data acquisition card is a high-speed digital A/D acquisition card.

6. The device for realizing high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing on the metal superficial layer according to claim 2, is characterized in that: the scanning visual angle of the scanning galvanometer is +/-18 degrees; the laser is a pulse laser.

7. The device for realizing high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing on the metal superficial layer according to claim 2, is characterized in that: the laser ultrasonic detector generates pulse laser by a laser, the laser beam enters a scanning galvanometer, the angle of a reflecting mirror of the galvanometer is adjusted by a galvanometer control card, the scanning of the pulse laser on a part to be detected is realized, and signals of longitudinal waves, transverse waves and surface waves are generated on the surface of the part and spread to four sides on the surface of the part under the action of a thermo-elastic mechanism.

8. The device for realizing high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing on the metal superficial layer according to claim 2, is characterized in that: the information processor detects echo signals of interaction of ultrasonic waves and surface defects on the metal surface through an ultrasonic detector, the signals are amplified through a signal amplifier and transmitted to a computer, and ultrasonic signals of a certain time are collected at a high speed through a collection card and converted into quantitative data.

9. The device for realizing high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing on the metal superficial layer according to claim 2, is characterized in that: the information processor processes the ultrasonic data through a computer, obtains information about the defects according to different detection requirements, and performs visual imaging on the defects according to the ultrasonic information.

10. The method for processing data by using the device for realizing high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing on the metal superficial layer as claimed in claims 1-9 is characterized by comprising the following steps:

(1) dispersing the area to be scanned and covered with the defects into a uniform dot matrix, wherein the scanning of adjacent rows or adjacent columns of scanning tracks adopts a zigzag shape;

(2) calculating a laser repetition frequency f1 and a data acquisition frequency f2, wherein f1 is not less than k V1000/A, f2 is not less than N V1000/A, A is the width of a scanning area, V is the sound velocity of ultrasonic waves, N is the data volume acquired by each scanning point, and k is less than 0.75;

(3) defining acquisition points as a two-dimensional array P_i，jWherein I belongs to [ 0, I ], I = A/dx, J belongs to [ 0, J ], J = A/dy, and the array corresponds to scanning points in a two-dimensional space one by one; after data acquisition, the N data acquired by each scanning point are divided into an array dⁿ _i,jCorresponding to acquisition Point P_i，jPerforming the following steps; d isⁿ _i,jWherein N belongs to [ 0, N-1 ];

(4) converting the acquired original data format into a three-dimensional array (i, j, t) respectively containing the space position information and the time dimension of a sample surface scanning point, wherein the stored data value is a sound field intensity value at a corresponding moment at a corresponding space position;

(5) defining a mapping table of sound field intensity values and colors, and mapping the maximum value and the minimum value of data in the three-dimensional array (i, j, t) with color values respectively to obtain corresponding colors; taking the position of the point (I, j) as a pixel point in the generated image to obtain N images of I; and replaying the N images in a video form to obtain a process visual video of the interaction of the laser ultrasonic sound field and the sample near-surface defects.

Technical Field

The invention relates to the field of nondestructive testing, in particular to a high-efficiency laser ultrasonic scanning imaging testing and ultrasonic data processing method.

Background

With the development of scientific technology and social production, the performance requirements of the industry on materials are higher and higher. Because the metallurgy technology at the present stage can not produce perfect materials, and meanwhile, the materials often have a plurality of defects in the processing process. Such as cracks, holes, etc. during casting, pores, inclusions, etc. during welding. These defects can lead to failure of the part during use, a result which is often unthinkable if applied to large structural members. Nondestructive testing is one of the direct and effective means for finding such a potential safety hazard.

Ultrasonic detection is the most important means of nondestructive testing, and laser ultrasonic detection belongs to a novel ultrasonic detection method. Compared with the traditional piezoelectric ceramic transducer, the laser ultrasonic transducer has the characteristics of non-contact, long distance and the like. For example, patent document No. 201310669619.7 discloses a non-contact visualization method and device for an ultrasonic field used for nondestructive inspection, which scans a region to be inspected by a pulse laser, generates ultrasonic waves based on a thermoelastic effect, receives ultrasonic signals by a laser interferometer, and processes acoustic signals by a computer to achieve a defect detection visualization effect. However, the method disclosed in the patent document has the disadvantages of slow scanning speed, huge data acquisition, low detection efficiency, and incapability of quantitatively detecting the size of the defect.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing method, which aims to solve the problems in the prior art.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing device comprises a workpiece to be detected, wherein the processing device comprises a laser ultrasonic detector, a data acquisition unit and an information processor; the laser ultrasonic detector is arranged above a workpiece to be detected, a data acquisition unit is arranged on the workpiece to be detected, and the laser ultrasonic detector and the data acquisition unit are both connected with the information processor; the information processor is a computer.

The laser ultrasonic detector comprises a laser and a scanning galvanometer; the laser and the scanning galvanometer are connected with a computer, and the scanning galvanometer is arranged above a workpiece to be detected;

the data acquisition unit comprises an ultrasonic detector and a signal amplifier; the ultrasonic detector is arranged on the workpiece to be detected and is connected with the computer through the signal amplifier.

The laser ultrasonic detector also comprises a galvanometer control card, and the galvanometer control card is installed in a computer.

The data acquisition unit also comprises a data acquisition card which is arranged in the computer; the data acquisition card is a high-speed digital A/D acquisition card.

The laser ultrasonic detector generates pulse laser by a laser, the laser beam enters a scanning galvanometer, the angle of a reflecting mirror of the galvanometer is adjusted by a galvanometer control card, the scanning of the pulse laser on a part to be detected is realized, and signals such as longitudinal waves, transverse waves, surface waves and the like are generated on the surface of the part and are transmitted to four sides on the surface of the part under the action of a thermo-elastic mechanism.

The information processor detects echo signals of interaction of ultrasonic waves and surface defects on the metal surface through an ultrasonic detector, the signals are amplified through a signal amplifier and transmitted to a computer, and an acquisition card acquires ultrasonic signals for a certain time at a high speed and converts the ultrasonic signals into quantitative data.

The information processor processes the ultrasonic data through a computer, obtains information about the defects according to different detection requirements, and performs visual imaging on the defects according to the ultrasonic information.

The scanning angle of view of the scanning galvanometer is +/-18 degrees.

The laser is a pulse laser.

The data acquisition card is a high-speed digital A/D acquisition card.

The data acquisition card and the galvanometer control card are installed on a computer.

The control software and the visualization software are developed by labview.

The maximum scanning area can be determined by the height of the field lens and the workpiece under the galvanometer.

The invention further discloses a method for high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing, which comprises the following steps:

s1 planning of scanning path

And dispersing the area needing to be scanned and covered with the defects into a uniform dot matrix, wherein the horizontal interval between each dot and the corresponding dot is dx, and the longitudinal interval is dy. In order to increase the laser scanning efficiency, the scanning between the adjacent lines (or rows) of the scanning track adopts a zigzag shape. When the scanning method is adopted for ultrasonic detection, the smaller the lattice intervals dx and dy, the higher the detection resolution is, but the larger the data amount to be processed is.

S2 calculation of laser repetition frequency and data acquisition frequency

Because the number of laser scanning points is large, in order to ensure the detection efficiency, a laser with high repetition frequency is generally selected to be excited, so that the scanning time is shortened. However, in order to make the excited ultrasonic information distinguishable, the ultrasonic information excited by two adjacent scanning points cannot generate the phenomenon of ultrasonic field superposition at the position of the receiving sensor, so the time interval of laser excitation cannot be too short. Therefore, assuming a width of a scanning region of a (mm) and a sound velocity of an ultrasonic wave of V (m/s), it is required that a repetition frequency of the laser should not exceed k V1000/a (k < 0.75).

To ensure that the data acquisition can obtain sufficient ultrasound-defect interaction information, the data acquisition time must be sufficient, which also limits the use of too high a laser scan repetition rate. Still taking the above parameters as an example, the time required for the laser-excited ultrasound to travel from one end through the entire scan area is: A/(V1000), the shortest acquisition time of the data acquisition equipment is not shorter than the laser ultrasonic propagation time on the premise of synchronous acquisition triggering and laser light emitting, and the information of interaction between the ultrasonic waves and the defects is effectively distinguished. Assume that the data volume collected for each scan point is N. The performance requirement for the acquisition device is that the acquisition frequency is greater than N x V1000/a when the fastest scans are achieved.

S3, defining the collected original data as an array

Suppose the scan area is A x A (mm)²) And the scanning interval is dx and dy (mm), assuming that the data quantity collected at each scanning point is N, each collected data is represented by M bytes, and when each row and column comprises head and tail points, one scanning comprises the data quantity of (A/dx + 1) × (A/dy + 1) × N × M bytes. Defining acquisition points as a two-dimensional array P_i，j(where I ∈ [ 0, I ], I = a/dx, J ∈ [ 0, J ], J = a/dy), which is in one-to-one correspondence with the scan points in the two-dimensional space. After data acquisition, the N data acquired by each scanning point are divided into an array dⁿ _i,j(where N ∈ [ 0, N-1 ]) corresponds to the acquisition Point P_i，jIn (1). The physical meaning is N pieces of collected data which are distributed orderly according to sampling time intervals by taking initial data as a time zero point; a two-dimensional array of raw data can be viewed as a combination of data sequences acquired from all points arranged in scan path order.

S4, processing the collected point data

According to the requirement of scanning imaging data processing, the acquired original data format is converted into a three-dimensional array (i, j, t) which respectively contains the spatial position information of the scanning point on the surface of the sample and the time dimension. The stored data values are sound field intensity values at corresponding time instants at the respective spatial positions. Let t be 1 st dimension, i be 2 nd dimension, and j be 3 rd dimension. According to the computer storage rule, the order of the frequency of the storage dimensions is low dimension → high dimension, t → i → j. Therefore, the three-dimensional array t-i surface data is stored in a continuous sequence, and the format and the sequence of the three-dimensional array t-i surface data are basically the same as those of original data. On the basis, for every i scanning points in the original data, the data of the scanning points are copied to a new three-dimensional array in a direct memory copy mode to form a new j-dimensional surface. The data conversion from the original data → the three-dimensional array is completed through j times of memory copy by the method. Due to the zigzag scanning strategy, the data between adjacent scanning lines are connected end to end, and the data need to be restored to be distributed according to the position of a space point. Namely, the i-dimensional data of the two-dimensional array of odd rows (the index of j is an odd number) is transposed, and the t-dimension is kept unchanged.

S5 visualization mapping processing

Defining a mapping table of the sound field intensity value and the color, and mapping the maximum value and the minimum value of the data in the three-dimensional array (i, j, t) with the color value respectively to obtain the corresponding color. And the position of the point (I, J) is used as a pixel point in the production image, so that N images with the size of I x J are obtained. Since the time interval of the laser scan is known. And replaying the N images in a video form to obtain a process visual video of the interaction between the laser ultrasonic sound field and the sample near-surface defect.

Compared with the prior art, the invention has the following beneficial effects because the technology is adopted:

firstly, detecting defects on a metal surface layer by adopting surface waves, wherein the surface waves are more sensitive to near-surface defects relative to longitudinal waves;

secondly, a scanning path is optimized, the repetition frequency of the laser and the signal acquisition frequency are fully considered, and the efficiency of laser ultrasonic detection and defect visualization imaging is effectively improved;

thirdly, the visual video can show the dynamic process of interaction of the ultrasonic waves and the defects in the transmission process, so that various defects of the metal surface layer can be better identified, and quantitative detection of the defects is realized;

fourthly, the ultrasonic detector is not limited to a contact probe, and can also adopt a non-contact detector such as a laser interferometer, and can be applied to the defect online detection in the high-temperature condition such as the welding or 3D printing process.

Drawings

FIG. 1 is a schematic view of a processing apparatus according to the present invention;

FIG. 2 is a schematic view of a scan path planning according to the present invention;

FIG. 3 is a first diagram of an array of samples according to the present invention;

FIG. 4 is a second schematic diagram of an array of samples according to the present invention;

FIG. 5 is a schematic view of an aluminum plate containing defects used in the experimental process of the method of the present invention;

FIG. 6 is a view of a sound field propagating imaging screen frame obtained from an experiment performed by the method of the present invention;

in the figure: 1. the device comprises a computer, 2, a laser, 3, a scanning galvanometer, 4, a workpiece to be detected, 5, an ultrasonic detector, 6 and a signal amplifier.

Detailed Description

The invention is further elucidated with reference to the drawings and the detailed description.

Embodiments of the present invention will be described in further detail below with reference to the accompanying drawings, as seen in the accompanying drawings. As shown in fig. 5, in this example, a surface layer containing holes with a diameter of 5mm is selected as the workpiece 4 to be detected, and the scanning area is 20mm by 20 mm.

1. Build laser ultrasonic detection device

Fig. 1 shows a high-efficiency laser ultrasonic scanning imaging detection and ultrasonic data processing device, which comprises a laser ultrasonic detector, a data acquisition unit and an information processor. The laser ultrasonic detector is arranged above the workpiece to be detected 4, the workpiece to be detected 4 is provided with a data acquisition unit, and the laser ultrasonic detector and the data acquisition unit are both connected with the information processor; the information processor is a computer 1.

The laser ultrasonic detection module comprises a laser 2, a scanning galvanometer 3 and a galvanometer control card; wherein the scanning galvanometer 3 and the laser 2 are directly connected with the computer 1, and the scanning galvanometer 3 is arranged above a workpiece 4 to be detected;

the data acquisition unit comprises an ultrasonic detector 5, a signal amplifier 6 and a data acquisition card; the ultrasonic detector 5 is arranged on the workpiece 4 to be detected and is connected with the computer 1 through a signal amplifier 6.

The data acquisition card and the galvanometer control card are installed in the computer 1.

2. Planning a scan path

As shown in fig. 2, the area to be scanned to cover the defect is discretized into a uniform lattice, with lateral spacing between dots dx =0.1mm and longitudinal spacing dy =0.1 mm. In order to increase the laser scanning efficiency, the scanning between the adjacent lines (or rows) of the scanning track adopts a zigzag shape.

3. Calculating laser repetition frequency and data acquisition frequency

In this example, the detection material is aluminum, the scan area width a =20mm, the wave velocity of the surface wave in aluminum is about V =3000m/s, f ≈ k ≈ V × 1000/a, and k =0.5, the limiting repetition frequency is about: 75 kHz. As the scan area becomes larger, the available limit repetition frequency decreases. In this example, the data collection amount requires that N is not less than 500 data, and in combination with the comprehensive consideration of the data processing amount, N is generally required to be less than 1000 data. Thus, taking N =500 as an example, the lowest sampling frequency of the data acquisition device is not lower than 500 × 3000 × 1000/20=75 MHz.

4. Detecting start and collecting data

The laser 2 emits pulse laser according to the calculated frequency, and scans the workpiece to be detected according to the planned scanning path under the reflection of the galvanometer. The ultrasonic receiver receives the ultrasonic signal and is provided with an acquisition card for acquiring original data according to the acquisition frequency obtained by calculation. Scanning is 20mm by 20mm, dx = dy =0.1mm, and then the scanning area is discrete as 201x201=40401 points. The data volume collected by each scan point is N =500 data, each data is 8 bytes double precision, and one scan includes data volume 40401 × 500 × 8 ≈ 161 MB. As shown in FIGS. 3 and 4, the acquisition points are defined as a two-dimensional array P_i，j(where i ∈ [ 0, 200 ], j ∈ [ 0, 200 ]), which are in one-to-one correspondence with the scan points in the two-dimensional space. After data acquisition, 500 data acquired by each scanning point are divided into an array dⁿ _i,j(where n ∈ [ 0, 499 ]) corresponds to the acquisition Point P_i，jThe physical meaning is that the initial data is used as a time zero point, and 500 pieces of collected data are distributed in sequence according to sampling time intervals; a two-dimensional array of raw data can be viewed as a combination of data sequences acquired from all points arranged in scan path order.

5. Computer processing collection point data

And converting the acquired original data format into a three-dimensional array (i, j, t) respectively containing the spatial position information and the time dimension of the scanning point on the surface of the sample. The stored data values are sound field intensity values at corresponding time instants at the respective spatial positions.

6. Computer visualization process

Defining a mapping table of the sound field intensity value and the color, and mapping the maximum value and the minimum value of the data in the three-dimensional array (i, j, t) with the color value respectively to obtain the corresponding color. And the position of point (i, j) is used as a pixel point in the production image, thus obtaining 500 images with 200 x 200 size. Since the time interval of the laser scan is known. And replaying the 500 images in a video form to obtain a process visual video of the interaction between the laser ultrasonic sound field and the sample near-surface defect. The detection result of the example is shown in fig. 6, the whole process of interaction of the ultrasonic waves and the round hole defects can be visually seen, the round hole defects on the surface layer of the aluminum plate are detected and quantified, and the defect size can be seen to be 5 mm.

The above-mentioned embodiments are merely preferred embodiments of the present invention, and should not be construed as limiting the present invention, and the scope of the present invention should be defined by the claims, and equivalents including technical features of the claims, i.e., equivalent modifications within the scope of the present invention.