CN114755300B - A defect location and quantitative detection method based on ultrasonic nondestructive testing - Google Patents
A defect location and quantitative detection method based on ultrasonic nondestructive testing Download PDFInfo
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- G01N29/4409—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by comparison
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Abstract
The invention discloses a defect positioning quantitative detection method based on ultrasonic nondestructive detection, which comprises the following steps of performing linear B scanning on a block to be detected to obtain B scanning signals comprising n A scanning signals, normalizing defect-free reference signals and B scanning signals to obtain defect echo signals, respectively extracting defect longitudinal wave echo moments in each A scanning signal from the defect echo signals, establishing a coordinate system by taking a first scanning position as an origin, taking a scanning direction as an x forward direction, taking a direction vertical to the surface of the block to be detected inside the block to be detected as a y forward direction, and obtaining defect positions and sizes according to scanning point coordinates, defect longitudinal wave echo moments and longitudinal wave velocities. The result of the invention can directly output the position and the size of the defect, the shape of the defect is drawn in a coordinate system, and the output result is visual. The invention can obtain the defect size based on the data of the straight line B scanning, and compared with the method for detecting the defect by the C scanning, the detection efficiency is obviously improved.
Description
Technical Field
The invention belongs to a defect detection technology of a metal material-increasing workpiece, and particularly relates to a defect positioning quantitative detection method based on ultrasonic nondestructive detection.
Background
Under the traction of manufacturing requirements such as large-scale, light-weight, integration and reliability of parts in the aerospace field, metal additive manufacturing technology and equipment are continuously mature, trial application is performed in the aerospace field at present, and compared with the traditional manufacturing process, the manufacturing size and the manufacturing efficiency are obviously improved. The metal additive manufacturing is used for manufacturing solid parts by melting and accumulating metal powder or wires layer by layer, so that the restriction of the complexity of the part structure on the manufacturing process, time and cost is greatly reduced, even parts which cannot be processed by the conventional manufacturing technology can be manufactured, and the metal additive manufacturing method has strategic positions in the aerospace field and has very wide application prospects. However, the metal additive manufacturing process is a very complex multi-physical field coupling strong unbalanced metallurgical process which simultaneously generates the interaction of high-energy beams and materials, crystal growth under the ultrahigh rapid solidification condition of a micro molten pool, tissue evolution under the repeated cyclic heating and cooling conditions and the like, and has the advantages of large temperature gradient, high solidification speed of the molten pool in the forming process, easiness in occurrence of metallurgical defects such as air holes, cracks and the like in the workpiece and serious influence on the mechanical properties of the workpiece. There is a need to develop a defect detection technology research for metal additive products.
Ultrasonic inspection refers to a nondestructive inspection method for inspecting internal defects of a metal member by using ultrasonic waves. The ultrasonic wave is transmitted to the surface of the component through the couplant by the transmitting probe, and different echo signals exist when the ultrasonic wave encounters different interfaces during the propagation of the inside of the component. Using the time difference between the transmission of the different reflected signals to the probe and the signal attenuation, defects inside the component can be inspected. The size, position and general nature of the defect can be determined based on the amplitude, propagation time, etc. of the echo signal. Because the metal material is repeatedly and circularly heated and cooled in the additive manufacturing process, air holes are easily generated in the part, and therefore, the research of ultrasonic quantitative detection technology of the air hole defects in the additive part is required to be carried out.
Chinese patent publication No. CN105973992a discloses an ultrasonic wavelet detection method for micro air hole defect of epoxy cast insulator, which realizes quantitative detection of bottom defect of the workpiece, and obtains defect size by difference of bottom position and air hole. However, the method has a good detection effect on the bottom surface defects and detection precision, and can realize defect positioning and cannot realize defect size measurement for the internal defects.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention aims to provide the defect positioning quantitative detection method based on ultrasonic nondestructive detection, which can effectively improve the defect detection precision and the detection efficiency.
In order to achieve the above purpose, the invention adopts the following technical scheme:
A defect positioning quantitative detection method based on ultrasonic nondestructive detection comprises the following steps:
Performing linear B scanning on a region to be detected of the block to be detected to obtain B scanning signals S comprising n A scanning signals;
Normalizing the defect-free reference signal S R and the B-scan signal S to obtain a defect echo signal S';
Extracting the defect longitudinal wave echo time t i in each A-scan signal from the defect echo signal S', wherein i represents the mark of the scan point;
Taking the first scanning position as an origin, taking the scanning direction as an x forward direction, taking the direction perpendicular to the surface of the block to be tested as a y forward direction, and establishing a coordinate system;
And obtaining the position and the size of the defect according to the coordinates of the scanning points, the echo time of the defect longitudinal wave and the wave speed of the longitudinal wave.
The invention is further improved in that the longitudinal wave velocity V is determined on a standard test block of the same material as the test block to be tested.
The invention further improves that an A-scan experiment is carried out on the surface of a standard test block, arrival time T 2、T4 of the echo signals of the secondary longitudinal wave and the fourth longitudinal wave is extracted from the signals, and the longitudinal wave velocity is determined according to the arrival time T 2、T4 of the echo signals of the secondary longitudinal wave and the fourth longitudinal wave.
The invention is further improved in that the longitudinal wave velocity is calculated by the following formula:
wherein H is the standard test block thickness.
A further improvement of the present invention is that the defect-free reference signal S R is obtained by A-scanning at the defect-free location of the block to be tested.
The invention further improves that the defect-free reference signal S R and the B-scan signal S are normalized, and the specific process of obtaining the defect echo signal S 'is to subtract the defect-free reference signal S R from the B-scan signal S to obtain the defect echo signal S'.
The invention is further improved in that the center of the circle of the defect position is calculated by the following formula:
Wherein i is 1 to n, and D (x D,yD) is the center of the defect position.
The invention is further improved in that the defect size r D is calculated by the following formula:
compared with the prior art, the invention has the following technical effects:
The result of the invention can directly output the position and the size of the defect, the shape of the defect is drawn in a coordinate system, and the output result is visual. The invention can obtain the defect size based on the data of the straight line B scanning, and compared with the method for detecting the defect by the C scanning, the detection efficiency is obviously improved. The detection method is simple, and on the basis of B-scan detection, the method can be simplified to select at least 3 representative positions and defect echo moments for calculation under extreme conditions. The invention has simple data processing process, does not need a signal processing method to carry out characteristic enhancement on the defect echo signal, and only needs to adopt a reference signal in a defect-free area and subtract the reference signal from the B-scanning original signal.
Drawings
FIG. 1 is a flow chart of an implementation of an embodiment of the present invention;
FIG. 2 is a block diagram of a detection system in an embodiment of the invention;
FIG. 3 is an ultrasonic B-scan signal after normalization in an embodiment of the present invention;
FIG. 4 shows the results of the treatment according to the method of the present invention.
FIG. 5 is a graph of the geometric relationship between two scan points and defects.
Detailed Description
The method of the present invention will be further described with reference to the accompanying drawings and examples.
Referring to fig. 2, the detection system adopted by the invention comprises an industrial personal computer 1, a scanning device 2, a PLC 3, an ultrasonic transmitting device 4, a signal acquisition card 5 and an ultrasonic probe 6, wherein the scanning device 2, the PLC 3, the ultrasonic transmitting device 4 and the signal acquisition card 5 are all connected with the industrial personal computer 1, the scanning device 2 is connected with the ultrasonic probe 6, the ultrasonic transmitting device 4 is also connected with the ultrasonic probe 6, and the ultrasonic probe 6 is used for testing a block 7 to be tested.
The invention discloses an ultrasonic quantitative detection method for internal air hole defects of a workpiece, which comprises the following steps:
Step 1, measuring the longitudinal wave velocity V on a standard test block with the same material as the block to be tested, wherein the method specifically comprises the following steps:
Step 1.1, performing an A-scan experiment on the surface of a standard test block with the thickness H through an ultrasonic probe 6, extracting arrival time T 2、T4 and the like of longitudinal wave echo signals such as secondary longitudinal waves, four-time longitudinal waves and the like from the signals, and measuring the thickness H of the standard test block;
step 1.2, determining the wave velocity of the longitudinal wave
Step 2, performing A-scanning on a defect-free part of a block to be tested to obtain a defect-free reference signal S R;
step 3, smearing a couplant (model is Hongda brand CG-98 ultrasonic couplant) on a region to be detected of a block to be detected, and performing straight line B scanning to obtain B scanning signals S comprising n A scanning signals;
Step 4, normalization processing, namely subtracting a defect-free reference signal S R from a B-scan signal S, enhancing a defect echo signal, and inhibiting the bottom echo of a longitudinal wave to obtain a defect echo signal S';
Step 5, respectively extracting the defect longitudinal wave echo time t i in each A scanning signal from the defect echo signal S';
Step 6, taking the first scanning position as an original point, taking the scanning direction as x positive direction, taking the direction inside the block to be tested and the direction vertical to the upper surface as y positive direction, establishing a coordinate system, and setting the coordinate of the ith scanning point as (x i,yi);
and 7, solving the position and the size of the defect according to the coordinates of the scanning point, the echo time of the defect longitudinal wave and the wave velocity of the longitudinal wave, wherein the specific steps are as follows:
step 7.1, constructing a System of equations Substituting the longitudinal wave velocity V, scanning the coordinates (x i,yi) of the point, obtaining the defect circle center position D (x D,yD) at the defect longitudinal wave echo time t i, wherein i is 1 to n.
Step 7.2, constructing an equationThe defect radius r D is determined.
The detection principle of the invention is as follows:
Assuming that the defect is a point (neglecting shape and size) of completely reflecting ultrasonic waves, when the ultrasonic waves propagate to the defect, because the probe has both excitation and receiving functions, the defect echo signals acquired by the probe are ultrasonic signals returned along the original path of the ultrasonic wave propagation path, and therefore the product of the propagation time t and the wave velocity V obtained from the ultrasonic signals is twice the distance from the probe to the defect. When the position of the defect is unknown, a circle is drawn by taking the position of the probe as the center and the distance from the probe to the defect as the radius, and the point on the circle is the position of the defect (reflection point) (the accurate defect position cannot be obtained from a single signal).
When the defect is an air hole, the cross section of the defect is a circle, and because ultrasonic waves propagate along the shortest path in the medium, a connecting line from the probe to the defect reflection point passes through the defect center (namely, three points of the probe-reflection point and the defect center are on the same straight line).
When there are 2 scan points (probe positions), as shown in FIG. 5, A, B is set as the scan point and "+.D as a broken line is a defect. As a circle drawn with the scan point A as the center and half of the product of the echo time and the wave velocity (AM length) as the radius, the defect reflection point was found on A. M is the reflection point corresponding to the A scanning point, so that M is on both the A and D points of AMD are on a straight line. Similarly, B is the second scanning point, N is the corresponding reflection point, and the three BND points are on a straight line.
AD-bd= |dm+ma-DN-nb|, since M and N are both on +.d, dm=dn, AD-bd= |ma-nb|. From the above derivation, it was found that, when the defect of the. Sup.D was unknown, from the relationship between A, B, M, N, A, B was the focus, and |MA-NB| was the real axis, a hyperbola may be drawn with the defect center D located above the hyperbola, as indicated by the dashed line segment in fig. 5.
In order to obtain the position of the center of the defect, only three scanning operations are needed, and two hyperbolas are drawn. However, in view of the accuracy of the detection, as many hyperbola drawings (corresponding to the equation set in step 7.1) as possible are required, the intersection is the defect center, and after the defect center is obtained, the defect radius r=ad-am=bd-BN.
Example 1
The embodiment provides a defect positioning quantitative detection method based on ultrasonic nondestructive detection, the specific implementation process is shown in fig. 1, and the method comprises the following steps:
1. Preparing a standard test block and a defect test block;
Two ER2319 aluminum alloy test blocks with the size of 100 multiplied by 10mm are prepared by an arc welding additive manufacturing technology, one non-defective test block is marked as a standard test block, the other test block is marked as a defective test block, the side machining radius is 1mm, and the transverse through hole with the depth of 5mm (the center position) is marked as a defect.
2. Measuring longitudinal wave velocity;
smearing a couplant on the surface of a standard test block, arranging an ultrasonic probe, detecting, and obtaining an A-scan signal. The primary longitudinal wave bottom echo appears at 3.4 mu s, the secondary longitudinal wave bottom echo appears at 6.9 mu s, and the thickness of the standard test block is combined with 10mm, so that the propagation speed of the longitudinal wave is 5840m/s.
3. Acquisition of defect-free reference signals
And (3) performing an A-scan experiment at the defect-free position of the defect test block, and performing time domain averaging on the signals after 16 repeated experiments to obtain a reference signal S R. In order to pursue the accuracy of the detection result, it is recommended to select as much scan data as possible.
4. Acquiring an original ultrasonic signal;
And placing the defect test block on a scanning device, smearing a couplant on a region to be detected, and fixing an ultrasonic probe on the scanning device. The scanning parameters are set in a computer, namely the scanning point number is 5, the scanning step length is 1mm, the sampling frequency is 20MHz, the time domain average time is 16 times, the signal length is 160 points (8 mu s), and the normalized signal is shown in figure 3. The occurrence position of the longitudinal wave echo of the defect is 58,52,47,42,37, and the corresponding longitudinal wave echo time is 2.9 mu s,2.6 mu s,2.3 mu s,2.1us and 1.85 mu s.
5. Substituting equation calculation, and solving defect positions;
substituting the coordinates of the scanning points, the echo time and the longitudinal wave velocity into an equation set
Where i=1, 2,3,4.
And (3) drawing hyperbolas according to the 4 equations by taking the first scanning position as a coordinate original snack, wherein 5 scanning point positions are marked on the x-axis as shown in fig. 4, and the intersection point of the four hyperbolas is the defect center position D (8.008,5.006).
6. Substituting equation calculation and solving defect radius
And 5 defect radius values are obtained, and the defect radius 1.0112mm is obtained after the average, so that the defect radius is consistent with the defect size.
Claims (3)
1. The defect positioning quantitative detection method based on ultrasonic nondestructive detection is characterized by comprising the following steps of:
Performing linear B scanning on a region to be detected of the block to be detected to obtain B scanning signals S comprising n A scanning signals;
Normalizing the defect-free reference signal S R and the B-scan signal S to obtain a defect echo signal S';
Extracting the defect longitudinal wave echo time t i in each A-scan signal from the defect echo signal S', wherein i represents the mark of the scan point;
Taking the first scanning position as an origin, taking the scanning direction as an x forward direction, taking the direction perpendicular to the surface of the block to be tested as a y forward direction, and establishing a coordinate system;
obtaining the position and the size of the defect according to the coordinates of the scanning points, the echo time of the defect longitudinal wave and the wave speed of the longitudinal wave;
the longitudinal wave velocity is calculated by the following formula:
Wherein H is the thickness of a standard test block, T 2 is the arrival time of a secondary longitudinal wave signal, and T 4 is the arrival time of a quaternary longitudinal wave signal;
the center of the defect position is calculated by the following formula:
Wherein i is 1 to n, D (x D,yD) is the center of a defect position, x D is the abscissa of the center of the defect, y D is the abscissa of the center of the defect, x i is the abscissa of a scanning point, y i is the ordinate of the scanning point, x i+1 is the abscissa of the next scanning point, y i+1 is the ordinate of the next scanning point, t i is the echo time of the defect longitudinal wave, t i+1 is the echo time of the next defect longitudinal wave, and V longitudinal wave speed;
the defect size r D is calculated by the following formula:
2. The method for quantitatively detecting defect localization based on ultrasonic non-destructive inspection according to claim 1, wherein the defect-free reference signal S R is obtained by a-scanning at a defect-free site of a block to be inspected.
3. The defect positioning quantitative detection method based on ultrasonic nondestructive detection according to claim 1 is characterized in that the defect-free reference signal S R and the B-scan signal S are normalized, and the defect echo signal S' is obtained by subtracting the defect-free reference signal S R from the B-scan signal S.
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