JP2017015668A - Plate weld inspection method and inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize precise evaluation of quality of spot welding.SOLUTION: According to the invention, an inspection method for inspecting a junction state of a weld formed by stacking and welding multiple plates includes: a transmission step of transmitting a guide wave to be propagated across the plate from multiple transmission positions outside the weld, at a first position on the plate; a receiving step of receiving the guide wave propagated across the plate at multiple receiving positions outside the weld, at a second position on the plates; and a determination step of determining quality of junction at the weld on the basis of a result of a time frequency analysis to be obtained by applying wavelet transform to a guide wave signal received in the receiving step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ultrasonic flaw detection method which is a kind of non-destructive inspection technique, and relates to a method and apparatus for inspecting the welding state of a welded portion of a metal plate using a guide wave which is a kind of ultrasonic wave.

  Many automobiles and home appliances use metal plate materials joined by many spot weldings. For example, in an automobile manufacturing factory, it is necessary to accurately inspect spot welds on site in a short time. In particular, a portion where a melted and solidified portion (nugget) is generated (hereinafter referred to as a welded portion) and a portion where the interface of the metal plate is locally welded but no nugget is generated (hereinafter referred to as a poorly welded portion). There is a need for a spot welding inspection method that can easily determine whether or not. The body of an automobile is assembled by thousands of spot welds, and the quality of the weld affects the strength and durability of the car. Therefore, it is necessary to inspect whether spot welding is being performed properly. Very important.

  In an automobile factory, the quality of spot welding is judged by whether or not the nugget diameter (hereinafter referred to as nugget diameter) exceeds a standard. Therefore, it is necessary to actually break and measure the nugget diameter, but since it is not possible to break the actual product and measure the nugget diameter, prepare a product for quality confirmation in advance and break the spot weld Welding conditions when good quality is confirmed through testing are applied to the product. By maintaining this welding condition, the quality of spot welding is assured. In addition, the actual product is periodically extracted and a chisel test is performed. The chisel test is a method in which chisel is driven in the vicinity of the weld to check the nugget joining state, but in order to perform the chisel test, it is necessary to stop the production line for the test work. There was a problem from the viewpoint of production cost.

  Therefore, in recent years, various apparatuses and methods for non-destructively inspecting the soundness of spot welds using ultrasonic waves have been proposed.

For example, in Patent Documents 1 and 2, in order to inspect the welded state of a spot welded portion that is produced by superimposing and welding two plates, an ultrasonic probe is brought into contact with the plate surface perpendicularly, A method and an apparatus for detecting a reflected wave with the incident light is disclosed.
In Patent Documents 1 and 2, a bottom surface multiple reflection echo is observed in which longitudinal wave ultrasonic waves perpendicularly incident on a spot weld are reflected multiple times between the front and back surfaces of the weld and return to the ultrasonic probe. This method utilizes the fact that the phenomenon in which the echo height of the bottom surface multiple reflection echo attenuates with propagation differs between the welded portion and the poorly welded portion. The metal structure of the nugget is a collection of coarse crystals extending in one direction, so the attenuation of ultrasonic waves is larger than that of the steel sheet, whereas the metal structure of the poorly welded part has a small crystal grain, so the attenuation of ultrasonic waves is small. It is known. Therefore, the amplitude of the bottom echo at the welded portion is rapidly attenuated as the number of reflections on the bottom surface increases. Using this difference, the welded portion and the poorly welded portion are identified.

  However, in Patent Documents 1 and 2, since ultrasonic waves are transmitted and received in a vertical direction with respect to a subject on a flat plate, the amplitude of the bottom multi-reflection echo that returns to the ultrasonic probe after multiple reflection between the front and back surfaces of the welded portion. However, it is difficult to accurately identify the welded portion and the poorly welded portion due to the influence of the inclined surface around the depression formed in the spot welded portion and the fine irregularities on the surface of the spot welded portion.

  In order to solve this, in Patent Documents 3 to 5, a plurality of ultrasonic probes for transmission and a plurality of ultrasonic probes for reception are installed outside the spot welded portion so as to sandwich the spot weld, A method using a Lamb wave signal propagating along the path of the above is disclosed. Thereby, the soundness of spot welding can be evaluated without being affected by the unevenness of the surface of the spot welded portion or the inclined surface around the welded portion. Waves propagating on the surface of an elastic body are generally called guide waves, and those having a vertical displacement with respect to the propagation direction are particularly called lamb waves or plate waves, but here they are called guide waves without distinction. .

  In Patent Document 4, the invention of Patent Document 3 is improved, and a cross-correlation operation between a guide wave signal that has propagated a path that does not include a spot weld and a guide wave signal that has propagated a path that includes a spot weld, Frequency analysis is performed by Fourier transform, and improvements are made so that the quality of spot welding can be judged in a short time.

  Further, in Patent Document 5, when the guide wave passes through the welded portion, the frequency component of the waveform changes due to the influence of the metal structure of the nugget, and the influence that adversely affects the discrimination between the welded portion and the poorly welded portion is avoided. A method is disclosed. In Patent Document 5, it is determined using wavelet transform how much the received signal contains the component of the basic signal, and this is used to identify the welded portion and the unwelded portion.

Japanese Patent Laid-Open No. 2-87060 JP-A-4-265854 JP 2006-71422 A JP 2008-109230 A JP 2011-196862 A

  However, in the techniques of Patent Documents 3 to 5, a plurality of vibration modes included in the guide wave are not distinguished, and a guide wave signal in a state where the vibration modes are mixed is used for evaluation. It may not be possible to accurately evaluate the effect of attenuation. Since ultrasonic waves are generally scattered in the metal structure depending on the vibration mode, the signal attenuation method is also different. The guide wave is composed of a plurality of vibration modes, and has a characteristic of dispersibility in which sound speed is a function of frequency. Since these modes propagate independently, for example, even when a single pulse waveform is incident on a metal plate as an input ultrasonic wave, it is converted into a plurality of pulse waveforms with different speeds corresponding to each vibration mode. I will separate. Since these plural pulse waveforms include overlapping frequency components, the vibration mode cannot be separated only by Fourier transforming the received waveform signal as in the method disclosed in Patent Document 4.

  Therefore, the present invention separates the vibration mode included in the received guide wave signal by time-frequency analysis by continuous wavelet transform, and selectively uses information on a single or a plurality of selected vibration modes, This makes it possible to accurately evaluate the quality of welding. In addition, by performing time-frequency analysis on the guide wave signal propagating through multiple paths, extracting waveforms of single or multiple selected vibration modes and using images synthesized from those waveforms for visual evaluation Therefore, it is possible to judge the quality of spot welding efficiently and easily.

  Note that the wavelet transform is also used in the method disclosed in Patent Document 5, but as described in Patent Document 5, the frequency component for each time of the ultrasonic signal is calculated, that is, the time frequency. It is used not for analysis but for calculating how much the component of the basic signal is contained in the received ultrasonic signal, and its usage is greatly different from the present invention.

  In order to achieve the above object, the present invention provides an inspection method for inspecting a joining state of a welded portion formed by superposing and welding a plurality of plate members, wherein the welding is performed at a first position on the plate member. A transmission step of transmitting a guide wave propagating through the plate material from a plurality of transmission positions outside the part, and a guide wave propagating through the plate material at a plurality of reception positions outside the welded portion at the second position on the plate material. A reception step of receiving, and a determination step of determining whether or not the welded portion is joined based on a result of time-frequency analysis obtained by wavelet transform of the guide wave signal received in the reception step. .

  ADVANTAGE OF THE INVENTION According to this invention, the welding state of the spot weld part which piles up and welds a some metal plate can be test | inspected correctly.

1 is a diagram for explaining an overview of an inspection apparatus according to Embodiment 1. FIG. The top view of an array type ultrasonic sensor. 1 is a side view of an array type ultrasonic sensor in Embodiment 1. FIG. The top view of other array type ultrasonic sensors. The enlarged view of the piezoelectric vibration element of an array type ultrasonic sensor. The graph which shows the dispersibility of a vibration mode. The figure which shows an example of the time-frequency analysis figure which time-frequency-analyzed by continuous wavelet transform. The flowchart of the process which identifies the vibration mode and evaluates the magnitude | size of a nugget. The figure explaining creation of the image data which shows distribution of a welding state. The figure which shows an example of the image data which shows distribution of a welding state. The figure which shows distribution of the welding state contained in the area | region below a threshold value. The figure explaining the outline | summary of the test | inspection apparatus in Example 2. FIG. The top view of a 2nd array type ultrasonic sensor. The side view of the type | mold ultrasonic sensor in Example 2. FIG. The figure which shows an example of the image data which shows distribution of a welding state.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the following is only an Example, and it cannot be overemphasized that the content of invention is not limited to the following aspect.

  FIG. 1 shows an array type ultrasonic sensor 101 for transmitting or receiving a guide wave to the spot welded portion 100 in Example 1, and a voltage signal of the guide wave received by the array type ultrasonic sensor 101 by amplifying the digital signal. A transmission / reception unit 102 for converting the received signal and a display unit 103 for displaying the received signal and the inspection result as an image. The transmission / reception unit 102 also has a calculation function by a computer or the like, and also has a function of performing time-frequency analysis of the guide wave signal converted into a digital signal. Of course, a computer other than the transmission / reception unit 102 may be used for the calculation. The spot welded portion is obtained by joining a plurality of metal plates. Although the number of metal plates is not particularly limited, in this embodiment, a case where two metal plates are joined will be described as an example.

  2 and 3 are a top view and a side view of the vicinity of the array-type ultrasonic sensor 101 in FIG. 1, respectively. As shown in FIG. 2, an array type ultrasonic sensor 101 includes a plurality of piezoelectric vibration elements 201 in a ring shape, and the upper metal plate 104 is interposed via a wedge 202 made of a material that transmits ultrasonic waves. Ultrasound is incident on The piezoelectric vibration element 201 is not necessarily arranged in an annular shape, and may be arranged so as to surround the spot welded portion 100. It may be arranged in a polygonal shape. However, the area surrounded by the piezoelectric vibration element 201 needs to be larger than the spot welded portion 100. Usually, 8 to 64 piezoelectric vibration elements 201 are used, but a number outside this range may be used. However, since the spot welded part 100 can be measured from various directions when the number of the piezoelectric vibration elements 201 is large, a highly accurate result can be obtained. The number and arrangement of the piezoelectric vibration elements may be appropriately selected according to the required inspection accuracy. Further, the wedge is not limited to the integral annular shape, and may be divided into a plurality of pieces as shown in FIG. Furthermore, the central portion does not necessarily have to be hollow. For example, a cavity may be provided only in the upper portion of the spot welded portion 100, and the structure may be a columnar shape as a whole.

  FIG. 5 is an enlarged view of the vicinity of the piezoelectric vibration element 201, and longitudinal wave ultrasonic waves 501 are generated from the piezoelectric vibration element 201. The generated longitudinal wave ultrasonic waves 501 pass through the resin wedge 202 that transmits ultrasonic waves and reach the surface of the upper metal plate 104. The frequency of the longitudinal ultrasonic wave 501 generated by the piezoelectric vibration element 201 is usually in the range of several MHz to several tens of MHz. The thickness of the upper metal plate 104 is usually about 0.5 mm to several mm. When the wavelength of the ultrasonic wave incident on the upper metal plate 104 is approximately equal to or longer than the plate thickness of the upper metal plate 104, the longitudinal wave ultrasonic wave 501 propagating through the wedge becomes a guide wave 502. It propagates through the upper metal plate 104.

  Although not shown, when the piezoelectric vibration elements included in the piezoelectric vibration element 201 are referred to as 201-1, 201-2, 201-3,... 201-n (n is the total number of piezoelectric vibration elements), The guide wave transmitted from the element 201-1 is received by all the piezoelectric vibration elements including the piezoelectric vibration element 201-1. Since the guide wave 502 spreads along the upper metal plate 104 and is scattered or reflected by the spot welded part 100, the guide wave 104 transmitted from the piezoelectric vibration element 201-1 includes all of itself. Can be received by the piezoelectric vibration elements (that is, the piezoelectric vibration elements 201-1 to 201-n). It is desirable to receive the data at a time and record it by the transmission / reception unit 102 from the viewpoint of shortening the inspection time, but of course, the data may be received individually. That is, the piezoelectric vibration element 201-1 is transmitted and the piezoelectric vibration element 201-1 is received, the piezoelectric vibration element 201-1 is transmitted, the piezoelectric vibration element 201-2 is received, and the piezoelectric vibration element 201-1 is transmitted. The waveform may be recorded in a plurality of times, such as received in 201-3.

  Similarly, the guide wave transmitted from the piezoelectric vibration element 201-2 is received by all the piezoelectric vibration elements including the piezoelectric vibration element 201-2. In this way, waveform data corresponding to all combinations of the piezoelectric vibration elements 201 is recorded.

  Since the piezoelectric vibration element 201 is installed so as to surround the spot welded portion 100, the recorded waveform data does not include the case where the propagation path 203 and the propagation path 204 always include the spot welded portion 100 in the propagation path. Things exist. Here, it is not always necessary to record waveform data corresponding to all combinations, and only a part of the waveform data may be recorded as necessary. What is necessary is just to determine suitably considering the processing capability of the transmission / reception part 102, etc. FIG. However, in the combination, it is desirable that the propagation path includes or does not include spot welding.

  The nugget 301 generated in the spot weld 100 is a melt-solidified structure. Since this melt-solidified structure is a collection of rough columnar structures extending substantially in the plate thickness direction, transmission of ultrasonic waves is worse and attenuation is larger than that of a metal plate structure having no spot welds. Therefore, the guide wave 502 passing through the nugget 301 is affected by attenuation according to the distance passing through the nugget 301 along the propagation path. On the other hand, the guide wave 502 that does not include the nugget 301 in the propagation path is received by the piezoelectric vibration element 201 with almost no attenuation. Therefore, the size of the nugget 301 can be estimated by analyzing the attenuation of the guide wave 502.

  The guide wave has two types of vibration modes, S (symmetric) mode and A (asymmetric) mode, based on the vibration geometry. Each of the S mode and the A mode is further finely classified, and is named S0, S1, S2,..., A0, A1, A2,. Each of these vibration modes propagates independently, but has a characteristic of dispersibility in which the propagation speed is a function of frequency. FIG. 6 is a graph showing the dispersibility of these vibration modes. The horizontal axis represents frequency, and the vertical axis represents sound velocity (group velocity). The sound velocity includes a phase velocity and a group velocity. Since the present invention uses a pulsed guide wave, the velocity is described as a group velocity. As shown in the figure, since there are a plurality of vibration modes even at the same frequency, the vibration mode of the guide wave cannot be distinguished only by Fourier transforming the waveform data as in a normal frequency analysis.

  These vibration modes are not the same in how they are affected by the melt-solidified structure of the nugget 301. For example, FIG. 7 is an example of a time-frequency analysis diagram in which waveform data is recorded by the method according to the present invention, and a waveform including a waveform not including the nugget 301 in the propagation path is subjected to time-frequency analysis by continuous wavelet transform. The time frequency analysis is to analyze the time change of the frequency component included in the waveform data. Since the result of the continuous wavelet transform is a complex number and has a real part and an imaginary part, it is preferable to use a power spectrum. In addition, the time-frequency analysis diagram is usually represented by two axes of frequency and time, but when the propagation path is known in advance, it is represented by two axes of frequency and sound speed by dividing the propagation path by time. You can also. Here, the frequency and the speed of sound are used for easy comparison with the dispersion relation shown in FIG.

  In FIG. 7, the black part is small and the white part is large. As is apparent from the figure, not all frequency components are attenuated in the same way. Some of the nuggets 301 have a large influence while others have a small influence. If the amount of attenuation is evaluated using waveform data in which vibration modes are mixed, the size of the nugget 301 is accurately determined due to the influence of a region where the vibration mode that is hardly affected by the nugget 301 is dominant (for example, a region 701 in FIG. Cannot be evaluated. Therefore, it is important to select a region (for example, region 702 in FIG. 7) in which the vibration mode that is easily affected by the melt-solidified structure of the nugget 301 is dominant.

  The present invention discloses a method for accurately identifying the size of the nugget 301 by identifying the vibration mode, and a method for identifying the vibration mode will be specifically described below.

  FIG. 8 is a flowchart of processing for identifying the vibration mode and evaluating the size of the nugget 301 in the present invention.

  Step 1: The array type ultrasonic sensor 101 is installed at a position on the upper metal plate 104 where the spot weld 100 does not exist. As long as the material characteristics such as material and thickness are the same as those of the upper metal plate 104, the upper metal plate 104 may be on a different metal plate.

  Step 2: Record waveform data corresponding to all of the piezoelectric vibration elements 201 or a part of the combinations as necessary.

  Step 3: Create a time-frequency analysis diagram by continuously wavelet transforming the recorded waveform data. At this time, it is not necessary to perform time-frequency analysis on all waveform data recorded in step 1, and only one representative waveform data may be selected. Preferably, waveform data corresponding to a propagation path (for example, propagation path 203) passing through the vicinity of the center of the region surrounded by the piezoelectric vibration element 201 is selected.

  Step 4: The array type ultrasonic sensor 101 is installed on the upper metal plate 104 at the position where the spot weld 100 exists.

  Step 5: Record waveforms corresponding to all of the piezoelectric vibrating elements 201 or some combinations as necessary.

  Step 6: Select waveform data corresponding to the same propagation path as the propagation path selected in Step 3, and create a time-frequency analysis diagram by continuous wavelet transform.

Step 7: The time frequency analysis diagrams obtained in Step 3 and Step 6 are compared, and a point on the time frequency analysis diagram used for evaluation of the welded state is selected (for example, point 703 in FIG. 7). That is, the frequency f ₀ and the sound velocity V ₀ are selected. Now, if this point is called the point Q, it is preferable to select a point that is on the theoretical curve of the vibration mode and that has a large difference between the case where it passes through the nugget 301 and the case where it does not. However, the point Q is not necessarily on the theoretical curve.

  Step 8: Perform continuous wavelet transform on all waveform data recorded in Step 5.

Step 9: For each waveform data subjected to the continuous wavelet transform in Step 8, the power spectrum value P at the point Q (frequency f ₀ , sound velocity V ₀ ) selected in Step 7 is extracted from the time frequency analysis result.

  Step 10: In order to generate image data indicating the distribution of the welding state, as shown in FIG. 9, in the image lattice 901 corresponding to the inspection region (the region including the region surrounded by the piezoelectric vibration element 201), the waveform data P is added to the pixels along the propagation path 902 (for example, the pixel 903 in FIG. 9). This is performed for all propagation paths. When the image grid point and the propagation path do not exactly match, it is preferable to calculate a value to be added to each pixel by using an appropriate interpolation process for adjacent propagation paths.

  Step 11: There are pixels through which many propagation paths pass and pixels that do not pass, and the number of times P is added differs depending on the pixel. Therefore, each pixel is divided by the number of times P is added and averaged. FIG. 10 shows an example of an image representing the welding state of the spot welded portion 100 obtained by the processing up to step 11. Here, the distribution of the welded state is represented by black and white shading, but the pixel values may be allocated in a favorite color tone table so as to be adjusted so as to be most easily viewed by the user. Color display is also possible by selecting an appropriate color tone table. For example, in FIG. 10, a region 1001 substantially corresponds to the nugget 301, and a dark black portion is a portion with a good welded state.

  Step 12: In the image obtained in Step 11, a portion below a certain threshold is determined to be a welding region, the area of the region below the threshold is calculated, and the welding area is calculated. For example, in the image of FIG. 10, the area equal to or greater than the threshold value is the area 1101 shown in FIG. 11. Therefore, if the number of pixels included in this area is counted, a numerical value proportional to the area can be easily obtained. If the threshold value is about 50% of the pixel value at the position where the nugget 301 does not exist, good results are obtained empirically, but it is not always necessary to set this value. You may set suitably using the test piece etc. which become a reference | standard.

  Steps 1 to 4 and Steps 6 to 7 need not be performed every time the spot weld to be inspected is changed, but is first performed once to determine the point Q. It is only necessary to repeat steps 8 to 12. If point Q is designated, step 5 and steps 8 to 12 can all be automatically processed.

  In general, since there are a plurality of candidates for the point Q, the steps 9 to 12 are repeated for the plurality of points Q, and the welding state is determined from a plurality of images, or the welding state is determined from an image obtained by adding these pixels. You can judge.

  By the above means, it is possible to judge the quality of the spot welding with high accuracy, visually intelligibly and efficiently.

  In the above description, the present invention is applied to spot welding inspection of a metal plate, but the application target of the present invention is not limited to this. It is also applicable to welding inspection of aluminum plates and other inorganic and organic materials. The welded portion can be applied not only to spot welding but also to a welded portion formed by a general welding method. Further, the number of welds is not limited to two, and the evaluation of the soundness of the spot welded part is not limited only to the identification of the nugget part.

  In the first embodiment, only one array type ultrasonic sensor 101 is installed on the upper metal plate 104, but the first array type ultrasonic sensor 101 is provided on the upper metal plate 104 as shown in FIG. The second array type ultrasonic sensor 1201 may be installed on the lower metal plate 105 at a symmetrical position with the first array type ultrasonic sensor 101 and the metal plate interposed therebetween. When the number of metal plates to be welded is three or more, the second array type ultrasonic sensor 1201 may be installed on the lowermost metal plate. As shown in FIG. 13, in the second array type ultrasonic sensor 1201, a plurality of piezoelectric vibrating elements 1301 are incorporated in a ring shape like the first array type ultrasonic sensor 101. Ultrasonic waves are incident on the lower metal plate 105 through a wedge 1302 made of a material that transmits light. The arrangement of the piezoelectric vibrators 1301 of the second array type ultrasonic sensor 1201 is not necessarily the same as that of the piezoelectric vibration elements 201 of the first array type ultrasonic sensor 101, but the arrangement of the piezoelectric vibration elements 1301 is also preferable. It is desirable that the target position is between the piezoelectric vibration element 201 and the metal plate.

  Here, each piezoelectric vibration element included in the piezoelectric vibration element 1301 built in the second array-type ultrasonic sensor 1201 is represented by 1301-1, 1301-2, 1301-3,. The total number of piezoelectric vibration elements 201 of the first array type ultrasonic sensor 101 or the total number of piezoelectric vibration elements 1301 of the second array type ultrasonic sensor 1201). Also, a piezoelectric vibration element 201-m built in the first array-type ultrasonic sensor 101 and a piezoelectric vibration element at a symmetrical position with the metal plate interposed therebetween are referred to as a piezoelectric vibration element 1301-m.

  The guide waves transmitted from the piezoelectric vibration element 201-1 of the first array type ultrasonic sensor 101 are received by the piezoelectric vibration elements 1301-1 to 1301-n. The guide wave transmitted from the piezoelectric vibration element 201-1 propagates on the upper metal plate 104, passes through the spot weld 100 while being attenuated, and propagates to the upper metal plate 104 and the lower metal plate 105. At this time, the component propagated to the lower metal plate can be received by the piezoelectric vibration element 1301. Only the welded portion propagates to the lower metal plate 105.

If the piezoelectric vibration element 201 is replaced with the piezoelectric vibration element 1301 and the processing flow of FIG. 8 of the first embodiment is performed, an image in which only the welded portion is colored as shown in FIG. 15 is obtained. Using this, it is also possible to calculate the area of the welded portion by the same method as in the first embodiment.
Since other processes are the same as those in the first embodiment, description thereof is omitted.

  By the above means, it is possible to judge the quality of the spot welding with high accuracy, visually intelligibly and efficiently.

  In the above description, it has been applied to spot welding inspection of metal plates, but the application target of the present invention is not limited to this. It is also applicable to welding inspection of aluminum plates and other inorganic and organic materials. The welded portion can be applied not only to spot welding but also to a welded portion formed by a general welding method. Further, the number of welds is not limited to two, and the evaluation of the soundness of the spot welded part is not limited only to the identification of the nugget part.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 100 ... Spot welding part 101 ... Array type ultrasonic sensor 102 ... Transmission / reception part 103 ... Display part 104 ... Upper metal plate 105 ... Lower metal plate 201 ... Piezoelectric vibration element 202 ... Wedge 203 ... Propagation path 204 ... Propagation path 301 ... Nugget 501 ... Longitudinal ultrasonic wave 502 ... Guide wave 701 ... Area 702 ... Area 703 ... Point 901 ... Image lattice 902 ... Propagation path 903 ... Pixel 1201 ... Second array type ultrasonic sensor 1301 ... Piezoelectric vibration element 1302 ... Wedge

Claims (10)

An inspection method for inspecting a joining state of a welded portion formed by superposing and welding a plurality of plate materials,
A transmission step of transmitting a guide wave propagating through the plate material from a plurality of transmission positions outside the weld at the first position on the plate material;
A receiving step of receiving a guide wave propagating through the plate material at a plurality of receiving positions outside the welded portion at a second position on the plate material;
A plate material welded portion inspection method comprising a determination step of determining whether or not the welded portion is joined based on a result of time-frequency analysis obtained by wavelet transforming the guide wave signal received in the receiving step. The plate material welded portion inspection method according to claim 1,
The second position is on a second plate joined to the plate;
The plate material welded portion inspection method, wherein the receiving step receives a guide wave propagating through a second plate material joined to the plate material. In the plate material welded portion inspection method according to any one of claims 1 and 2,
The determination step includes a temporal change amount of spectral power obtained by wavelet transforming a guide wave signal including the welded portion in the propagation path of the guide wave, and a guide wave not including the welded portion in the guide wave propagation path. A plate material welded portion inspection method characterized in that an image is generated based on a temporal change amount of spectral power obtained by wavelet transform of a signal, and whether or not the welded portion is joined based on the image. In the plate material welded portion inspection method according to claim 3,
The determination step selects a point on the analysis diagram having a large difference in influence due to welding in the generated plurality of images, wavelet transforms the plurality of recorded waveform data, and the wavelet transform for each waveform data A method for inspecting a welded part of a plate material, comprising: extracting a power spectrum value at a selected point, assigning the power spectrum value along a propagation path, and creating image data indicating a distribution of a welding state. In the plate material welded portion inspection method according to any one of claims 1 to 4,
The plate material welded portion inspection method, wherein the determining step determines whether or not the welded portion is joined based on one or a plurality of vibration modes of the guide wave. An inspection device for inspecting a joining state of a welded portion formed by superposing and welding a plurality of plate materials,
A transmitter for transmitting a guide wave propagating through the plate material from a plurality of transmission positions outside the welded portion at a first position on the plate material;
A receiving unit that receives a guide wave propagating through the plate material at a plurality of receiving positions outside the welded portion at a second position on the plate material;
An apparatus for inspecting a welded part of plate material, comprising: a determination unit that determines whether or not the welded portion is joined based on a result of time-frequency analysis obtained by wavelet transforming the guide wave signal received by the receiving unit. In the board | plate material welding part inspection apparatus of Claim 6,
The second position is on a second plate joined to the plate;
The plate material welded portion inspection apparatus, wherein the receiving unit receives a guide wave propagating through a second plate material joined to the plate material. The plate material welded portion inspection apparatus according to any one of claims 6 and 7,
The determination unit is a temporal change amount of spectral power obtained by wavelet transforming a guide wave signal including the welding part in the propagation path of the guide wave, and a guide wave not including the welding part in the propagation path of the guide wave. An apparatus for inspecting a welded material for a plate material, comprising: generating an image based on a temporal change amount of spectrum power obtained by wavelet transform of a signal; The plate material welded portion inspection apparatus according to claim 8,
The determination unit selects a point on the analysis diagram having a large difference in influence due to welding in the generated plurality of images, wavelet transforms the plurality of recorded waveform data, and the wavelet transform for each waveform data A plate material welded portion inspection apparatus that extracts power spectrum values at selected points, assigns the power spectrum values along a propagation path, and creates image data indicating a distribution of welding states. In the plate material welded portion inspection apparatus according to any one of claims 6 to 9,
The plate member welded portion inspection apparatus, wherein the determining portion determines whether or not the welded portion is joined based on one or a plurality of vibration modes of the guide wave.

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