JP4731358B2 - Ultrasonic spot weld evaluation method and apparatus - Google Patents

Description

  The present invention relates to a method and an apparatus for inspecting the diameter of a melted portion (nugget) formed by spot welding with nondestructive means using ultrasonic waves.

  2. Description of the Related Art In recent years, for example, in an automobile body manufacturing factory, a spot welding inspection method that can be easily implemented is desired in order to perform inspection of a spot welded portion with high efficiency on site.

  The body of an automobile is assembled by thousands of spot welds, and the quality of spot welds directly affects the strength and durability of the car body. It is extremely important to do. Conventionally, as a method for inspecting such spot welds, a ladle inspection for determining pass / fail is performed by inserting a chisel between spot-welded metal plates and confirming whether or not the spot weld is peeled off. However, since spot welding may break when performing a chisel inspection, it is difficult to accurately determine whether or not spot welding is good depending on the chisel inspection. Further, since it is impossible to use the spot welded portion destroyed by the chisel inspection for the product, there is a problem that the cost is high.

  In recent years, various apparatuses and methods for inspecting the quality of spot welds using ultrasonic waves in a nondestructive manner have been proposed.

  For example, Patent Documents 1 to 4 disclose a method and an apparatus for detecting reflected waves by allowing ultrasonic waves to be incident perpendicularly to a plate surface in order to evaluate the quality of a spot welded portion that is manufactured by overlapping two plates. Is disclosed. Further, in Patent Document 5, a pair of local water immersion probes are arranged on the upper and lower sides of a subject so as to face each other and the subject is moved in the horizontal direction, whereby a transmission-side local water immersion probe is obtained. An ultrasonic flaw detector is disclosed that scans a spot welded portion of an object with an ultrasonic beam transmitted from the receiver and determines the presence or absence of a flaw in the spot welded portion from a signal received by a receiving-side local water immersion probe. ing.

JP 2000-146828 A JP 2002-131297 A Japanese Patent Laid-Open No. 11-2627 JP-A-6-265529 JP-A-62-52456 JP 2004-163210 A

  However, in these prior arts, ultrasonic waves are transmitted and received in a vertical direction with respect to a flat subject. Therefore, since the ultrasonic beam cannot efficiently enter the subject on the inclined surface 102c formed around the recess 102b formed in the spot welded portion 102 of the subject illustrated in FIG. 22, spot welding is performed. There is a problem that it is difficult to detect the size of the nugget 102a formed in the portion 102 with high accuracy.

  That is, as shown in FIG. 22, when the upper plate 101a and the lower plate 101b are overlapped and spot welded, the spot welded portion 102 has a melt-solidified structure 102a called “nugget” at the joint between the upper plate 101a and the lower plate 101b. Is formed. In spot welding, since the upper plate 101a and the lower plate 101b are strongly pressed by electrode tips (not shown), a recess 102b corresponding to the shape of the tip of the electrode tip is formed on the surfaces of the upper plate 101a and the lower plate 101b. Is done. Further, a conical inclined surface 102c is formed between the bottom surface of the recess 102b and the surfaces of the upper plate 101a and the lower plate 101b. When welding is performed normally, the diameter of the nugget 102a is slightly larger than or equal to the diameter of the electrode tip used for welding, and the inner diameter of the recess 102b is chamfered because the shape of the tip of the electrode tip is chamfered. Since it is formed in the column shape which has, it becomes a little smaller than the diameter of the column part of an electrode tip. Therefore, the inner diameter of the recess 102b is usually slightly smaller than the diameter of the nugget 102a. When welding is not performed normally, the nugget diameter is smaller than when welding is performed normally, and abnormalities such as insufficient strength occur. In addition, the code | symbol S in a figure has shown the toe of the nugget 102a.

  Thus, since the conical inclined surface 102c is formed between the bottom surface of the recess 102b and the surfaces of the upper plate 101a and the lower plate 101b in the spot welded portion 102, the ultrasonic inspection apparatus according to the prior art described above. When the ultrasonic beam is transmitted / received in the direction perpendicular to the surfaces of the upper plate 101a and the lower plate 101b, which are subjects, as described above, the ultrasonic wave is reflected on the inclined surface 102c and almost propagates inside the subject. Therefore, almost no signal is obtained from the examination site. As described above, since the size of the nugget 102a is slightly larger than or equal to the diameter of the electrode tip, the toe S of the nugget 102a and the inclined surface 102c formed on the subject almost overlap each other. ing. Therefore, when the ultrasonic wave is reflected on the inclined surface 102c, it is difficult to obtain an accurate signal from the vicinity of the nugget toe S, and it is difficult to accurately determine the nugget diameter and the presence / absence of a defect. .

  Part of the inventors of the present application already disclosed in Patent Document 6 an ultrasonic evaluation method of a spot welded portion formed by superposing and welding a plurality of metal plates, and welding the spot welded portion to a metal plate outside the spot welded portion Exciting Lamb waves toward the metal, transmitting the Lamb waves to the weld metal, and receiving the Lamb waves after transmission, the soundness of the spot welds is evaluated. An evaluation method was proposed. By this technique, the spot welded portion was successfully evaluated without being affected by the inclined surface formed around the recess generated in the spot welded portion. However, in Patent Document 6, when two Lamb wave probes are arranged facing each other across the spot welded portion, the positional relationship between the two Lamb wave probes and the spot welded portion deviates from a predetermined positional relationship. The Lamb wave propagation path deviates from the center of the spot weld, and it has been found that the soundness of the spot weld cannot be evaluated correctly. The above problem is due to the fact that the positional relationship between the two Lamb wave probes and the spot welded part can only be confirmed visually.

  The Lamb wave here is also called a plate wave, and an ultrasonic wave is incident obliquely on a thin plate (either a metal plate or a non-metal plate) at a specific incident angle. Occurs. Obliquely traveling longitudinal and transverse waves generated in the thin plate by refraction of the incident wave propagate and interfere with repeated reflection with mode conversion on the front and back surfaces of the thin plate. As a result, the thin plate is symmetric or asymmetric with respect to the thickness center. A traveling wave is generated that displaces to. This traveling wave is a Lamb wave (see Joseph L. Rose, Ultrasonic waves in solid media, pp. 101-126, Cambridge Univ Press, Cambridge, 1999). The Lamb wave probe is an ultrasonic probe that can cause an ultrasonic wave to be incident on a thin plate at a specific incident angle in order to excite a Lamb wave on the thin plate. Further, this probe can be used for receiving a Lamb wave.

  The present invention has been made to solve such deficiencies of the prior art, and the problem is that even if measurement is limited to a short time (for example, within 5 seconds per point), It is to evaluate the soundness (presence / absence of nugget, nugget diameter, weld crack) of the spot welded portion with high reliability without being influenced by the deviation between the position of the acoustic probe and the position of the spot welded portion. Another object of the present invention is to make it easy to determine the size of the nugget by displaying the size of the nugget of the spot welded portion so that it can be easily grasped visually.

The present invention relates to an ultrasonic evaluation method for a spot welded portion formed by superposing and welding a plurality of metal plates, and a cross section formed by a direction along the surface of the metal plate or spot welded portion and a thickness direction. When the propagating ultrasonic waves are referred to as ultrasonic waves propagating along the surface of the subject, they propagate along the surface of the subject from a plurality of transmission positions on the metal plate outside the spot welded portion in a plurality of directions. the ultrasound, and transmitting the ultrasonic probe having a transducer array, a plurality of wave receiving positions outside the metal plate of the spot welds, the surface of the subject to the propagation path does not include a spot weld The ultrasonic wave propagating along the surface and the ultrasonic wave propagating along the surface of the subject including the spot weld in the propagation path are received by the ultrasonic probe including the transducer array, and the plurality of transmissions are received. Wave position and the above In each of the propagation path connecting the reception position, compared to a reference transmission time transmission time of reception it has been received wave ultrasound, (| reception ultrasonic propagation time - reference transmission time | / reference transmission time ) Is equal to or less than the threshold value, it is determined that the received ultrasonic wave does not include a nugget in the propagation path, a propagation path in which no nugget exists is extracted from the propagation path, and the extracted nugget is extracted. and calculate the nugget diameter on the basis of a region surrounded by the propagation path but does not exist, is obtained by solving the above problems.

The present invention also provides an ultrasonic evaluation method of a spot welded portion formed by superposing and welding a plurality of metal plates, and a cross section formed by a direction along the surface of the metal plate or spot welded portion and a thickness direction. When the ultrasonic wave propagating in the interior is referred to as the ultrasonic wave propagating along the surface of the subject, it is directed along the surface of the subject from a plurality of transmission positions of the metal plate on the outer side of the spot welded portion toward a plurality of directions. subject propagating ultrasonic waves, and transmit the ultrasonic probe having a transducer array, which does not include the plurality of wave reception position of the outer metal plate of the spot weld, spot weld the propagation path The ultrasonic wave propagating along the surface of the object and the ultrasonic wave propagating along the surface of the subject including the spot weld in the propagation path are received by an ultrasonic probe having a transducer array, Wave transmission position and front In each of the propagation path connecting the plurality of reception locations, and compared with a reference transmission time transmission time of reception has been received wave ultrasound, (| reception ultrasonic propagation time - reference transmission time | / reference transmitted Time) is equal to or greater than the threshold value, it is determined that the received ultrasonic wave includes a nugget in the propagation path, a propagation path in which the nugget exists is extracted from the propagation path, and the extracted nugget is extracted. The above problem is solved by calculating the nugget diameter based on the existence range of the propagation path in which there is.

The present invention also provides an ultrasonic evaluation apparatus for a spot welded portion formed by superposing and welding a plurality of metal plates, and a cross section formed by the direction along the surface of the metal plate or spot welded portion and the thickness direction. When the ultrasonic wave propagating in the interior is referred to as the ultrasonic wave propagating along the surface of the subject, it is directed along the surface of the subject from a plurality of transmission positions of the metal plate on the outer side of the spot welded portion toward a plurality of directions. An object that does not include a spot weld in the propagation path at an ultrasonic probe having an transducer array that transmits an ultrasonic wave propagating to the surface and a plurality of receiving positions of a metal plate outside the spot weld An ultrasonic probe having a transducer array for receiving ultrasonic waves propagating along the surface of the object and ultrasonic waves propagating along the surface of the subject including a spot weld in the propagation path; The transmission position of the In each of the propagation path connecting the reception position, and the comparison reference transmission time transmission time of reception it has been received wave ultrasound, (| reception ultrasonic propagation time - reference transmission time | / reference transmitted If (time) is less than or equal to a threshold value, it is determined that the received ultrasonic wave does not include a nugget in the propagation path, and a propagation path in which no nugget exists is extracted from the propagation path. means for calculating a nugget diameter on the basis of a region surrounded by the propagation path nugget is not present, by providing, at same that solves the above problems.

The present invention also provides an ultrasonic evaluation apparatus for a spot welded portion formed by superposing and welding a plurality of metal plates, and a cross section formed by the direction along the surface of the metal plate or spot welded portion and the thickness direction. When the ultrasonic wave propagating in the interior is referred to as the ultrasonic wave propagating along the surface of the subject, it is directed along the surface of the subject from a plurality of transmission positions of the metal plate on the outer side of the spot welded portion toward a plurality of directions. An object that does not include a spot weld in the propagation path at an ultrasonic probe having an transducer array that transmits an ultrasonic wave propagating to the surface and a plurality of receiving positions of a metal plate outside the spot weld An ultrasonic probe having a transducer array for receiving ultrasonic waves propagating along the surface of the object and ultrasonic waves propagating along the surface of the subject including a spot weld in the propagation path; The transmission position of the In each of the propagation path connecting the reception position, compared to a reference transmission time transmission time of reception it has been received wave ultrasound, (| reception ultrasonic propagation time - reference transmission time | / reference transmission time ) Is equal to or greater than the threshold value, it is determined that the received ultrasonic wave includes a nugget in the propagation path, a propagation path in which the nugget exists is extracted from the propagation path, and the extracted nugget is Means for calculating the nugget diameter based on the existence range of the existing propagation paths, thereby solving the above-mentioned problem.

  According to the present invention, the spot welded portion can be accurately evaluated in a nondestructive manner without being affected by the inclined surface formed around the recess formed in the spot welded portion, and the measurement time However, even if the measurement is limited to a short time, it is possible to evaluate the soundness of the spot weld with high reliability without being affected by the displacement of the position of the ultrasonic probe and the position of the spot weld. Become. Further, since the size of the nugget at the spot welded portion is easily grasped visually, it is easy to determine the size of the nugget.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  Hereinafter, the evaluation of a spot welded portion formed by joining two metal plates will be described as an example. The upper plate of the two metal plates is called the upper plate, and the lower plate is called the lower plate. In the present invention, as shown in FIG. 1, the ultrasonic probe 10 having the transducer array 11 and the ultrasonic probe 20 having the transducer array 21 are connected to the spot welded portion 2 on the upper plate 1a. Abut against the pinched position. An appropriate contact medium is interposed between the ultrasonic probe 10 and the ultrasonic probe 20 and the upper plate 1a.

  Using the ultrasonic probe 10 having the transducer array 11, ultrasonic waves are transmitted from a plurality of positions to the upper plate 1a. The ultrasonic probe 10 has a structure in which a transducer array 11 is attached to a resin wedge 12, and ultrasonic waves transmitted from the transducer array 11 are obliquely incident on the upper plate 1a. As shown in FIG. 2, the ultrasonic waves traveling obliquely with respect to the surface of the upper plate 1a are transmitted into the upper plate 1a by the obliquely incident ultrasonic waves. The obliquely traveling ultrasonic waves include longitudinal waves and transverse waves, and propagate through the upper plate 1a while repeating reflection and mode conversion on the bottom surface and surface of the upper plate 1a. In FIG. 2, a solid line is a transverse wave, and a broken line is a longitudinal wave. When the incident angle of the ultrasonic wave on the upper plate 1a is an appropriate value, the ultrasonic wave that propagates by repeating the reflection becomes a wave called a Lamb wave. The propagating ultrasonic wave is received by the ultrasonic probe 20 including the transducer array 21. The ultrasonic probe 20 has a structure in which a transducer array 21 is attached to a resin wedge 22.

The ultrasonic wave propagating along the plane path (path seen from the upper surface of the metal plate) shown in FIG. 3 by the ultrasonic probe 10 including the transducer array 11 and the ultrasonic probe 20 including the transducer array 21. Can be received. The individual transducers of the transducer array 11 of the ultrasonic probe 10 are represented as 11 _{1 to} 11 _N, and the individual transducers of the transducer array 21 of the ultrasonic probe 20 are represented as 21 _{1 to} 21 _N. To. As N, for example, the number of 4, 8, 16, 32 or the like is used. FIG. 3 shows a case where N is 16. Since the ultrasonic waves transmitted from the transducers 11 _{1 to} 11 _N of the transducer array have a spatial spread, the ultrasonic waves taking the planar path shown in FIG. 3 are transmitted from the transducers 11 _{1 to} 11 _N. can do.

The ultrasonic wave transmitted from the transducer 11 ₁ of the ultrasonic probe 10 and reception by the ultrasound probe 20 of the vibrator ₂₁ 1 through 21 _N. Then, the ultrasonic wave transmitted from the transducer 11 _{and second} ultrasonic probe 10, for reception by the ultrasound probe 20 of the vibrator ₂₁ 1 through 21 _N. This process, the ultrasonic wave transmitted from the transducer 11 _N of the ultrasonic probe 10, until the reception by the ultrasound probe 20 of the vibrator 21 ₁ through 21 _N, oscillator performs transmitting 11 _n (n = 1, 2,..., N) are sequentially changed. As a result, ultrasonic waves transmitted from a plurality of positions and propagating in a plurality of directions can be received by the transducers 21 _{1 to} 21 _N of the ultrasonic probe 20.

  As shown in FIG. 4, the nugget 2a generated in the spot welded portion 2 is a molten and solidified structure 2b having a directionality substantially parallel to the plate thickness direction. The melt-solidified structure 2b is also called a dendrite structure, and is a collection of coarse crystals extending in one direction, and therefore has a property that ultrasonic transmission is poor (attenuation is large) compared to the metal structure of a metal plate. Therefore, when the ultrasonic wave propagating in the path shown in FIG. 3 includes the molten solidified structure 2b in the path, the ultrasonic wave is attenuated according to the length of the molten solidified structure 2b existing in the propagation path. It is lowered and received by the ultrasonic probe 20.

  Further, the melt-solidified structure 2b has a property that the speed of propagation of ultrasonic waves therein is slightly different from that of the metal structure of the metal plate. In the melt-solidified structure 2b, as shown in the schematic diagram of the micro metal structure shown in FIG. 4, the specific orientation of the metal crystal (shown using a broken arrow in FIG. 4) is almost aligned in the plate thickness (z) direction. The tissue has elastic anisotropy. Therefore, the propagation speed of the ultrasonic wave changes depending on the propagation direction. On the other hand, since the metal crystal is oriented in a random direction in the metal structure of the metal plate, the propagation speed of the ultrasonic wave does not depend on the propagation direction and becomes a constant value. As described above, the propagation speed of the ultrasonic wave propagating along the surface of the subject is determined when the propagation path includes the molten solidified structure 2b and when the propagation path does not include the molten solidified structure 2b (the metal structure of the metal plate). Is generally different). Therefore, when the molten solidified tissue 2b is present in the propagation path of the ultrasonic wave propagating along the surface of the subject, the time required for transmission varies depending on the length parallel to the plate surface of the molten solidified tissue 2b. Therefore, when the ultrasonic wave propagating through the path shown in FIG. 3 includes the molten and solidified tissue 2b, the time required for transmission according to the length of the molten and solidified tissue 2b existing in the propagation path (hereinafter referred to as transmission). Is received by the ultrasonic probe 20. The transmission time is also called transmission time.

Hereinafter, first, a description will be given of a first reference example.

FIG. 5 shows a sample in which two steel plates having a thickness of 2.6 mm are overlapped and spot-welded, and the ultrasonic probe 10 and the ultrasonic probe 20 are sandwiched between the spot welds 2 as described above. After receiving the ultrasonic waves transmitted from the transducers 11 _{1 to} 11 _N of the ultrasonic probe 10 by the transducers 21 _{1 to} 21 _N of the ultrasonic probe 20, It is the result which showed the propagation path of the received ultrasonic wave by which the form of a received ultrasonic wave is compared with a reference | standard, and the said received ultrasonic wave form is not different from a reference | standard using the continuous line. Here, N is 16 and the amplitude is used as the form of the received ultrasonic wave. In addition, the ultrasonic probe 10 and the ultrasonic probe 20 are brought into contact with each other on a flat steel plate having a thickness of 2.6 mm that does not have a spot weld, and the transducers 11 ₁ to 11 of the ultrasonic probe 10 are brought into contact with each other. The amplitude of the received ultrasonic waves when the ultrasonic waves transmitted from 11 _N were received by the transducers 21 _{1 to} 21 _N of the ultrasonic probe 20 was used as a reference. Since the solid line shown in FIG. 5 is an ultrasonic wave propagation path that does not include the melted and solidified structure 2b, the melted and solidified structure 2b exists in the inner region surrounded by the intersecting solid lines. Further, the length in the array arrangement direction of the inner region surrounded by the intersecting solid lines is proportional to the size of the melt-solidified structure 2b when viewed from the direction perpendicular to the plate surface, that is, the nugget diameter.

Next, a first embodiment of the present invention will be described.

FIG. 6 shows a sample in which two steel plates having a thickness of 2.6 mm are overlapped and spot-welded, and the ultrasonic probe 10 and the ultrasonic probe 20 face each other with the spot welded portion 2 interposed therebetween as described above. The ultrasonic waves transmitted from the transducers 11 _{1 to} 11 _N of the ultrasonic probe 10 are received by the transducers 21 _{1 to} 21 _N of the ultrasonic probe 20 and then received. It is the result which showed the propagation path of the received ultrasonic wave in which the form of the wave ultrasonic wave was compared with the reference | standard, and the form of the said received ultrasonic wave was not different from a reference | standard using the continuous line. Here, N is 16, and the transmission time is used as the form of received ultrasonic waves. In addition, the ultrasonic probe 10 and the ultrasonic probe 20 are brought into contact with each other on a flat steel plate having a thickness of 2.6 mm that does not have a spot weld, and the transducers 11 ₁ to 11 of the ultrasonic probe 10 are brought into contact with each other. The transmission time of the received ultrasonic waves when the ultrasonic waves transmitted from 11 _N were received by the transducers 21 _{1 to} 21 _N of the ultrasonic probe 20 was used as a reference. Since the solid line shown in FIG. 6 is an ultrasonic wave propagation path that does not include the melted and solidified structure 2b, the melted and solidified structure 2b exists in the inner region surrounded by the intersecting solid lines. Further, the length in the array arrangement direction of the inner region surrounded by the intersecting solid lines is proportional to the size of the melt-solidified structure 2b when viewed from the direction perpendicular to the plate surface, that is, the nugget diameter.

FIG. 7 shows an example of an apparatus for carrying out the first embodiment. This apparatus includes an ultrasonic probe 10 including transducer arrays 11 _{1 to} 11 ₁₆ used for transmitting ultrasonic waves and an ultrasonic device including transducer arrays 21 _{1 to} 21 ₁₆ used for receiving ultrasonic waves. An electric pulse used to transmit ultrasonic waves from the transducer 20 and the transducers of the transducer arrays 11 _{1 to} 11 ₁₆ is supplied, and the transducer arrays 21 _{1 to} 21 ₁₆ receive the waves. An ultrasonic transmitter / receiver 30 for amplifying an ultrasonic signal, and interposed between the ultrasonic transmitter / receiver 30 and the transducer arrays 11 _{1 to} 11 ₁₆ , the transducers of the transducer arrays 11 _{1 to} 11 ₁₆ The switch circuit 25 for switching the connection with the acoustic wave transmitter / receiver 30 is interposed between the ultrasonic wave transmitter / receiver 30 and the transducer arrays 21 _{1 to} 21 _16, and the transducers of the transducer arrays 21 _{1 to} 21 ₁₆ Connection with sound wave transmitter / receiver 30 Switch circuit 26 for switching, a gate means 31 for extracting a signal by an ultrasonic wave propagating along the surface of the subject among signals amplified by the ultrasonic transmitter / receiver 30, and a received ultrasonic wave extracted by the gate means 31 It is comprised by the time measurement means 32 which detects the transmission time of an ultrasonic wave from a signal. It should be noted that the signal amplified by the ultrasonic transmitter / receiver 30 is A / D converted, and the gate means 31 and the software are used to detect the transmission time of the ultrasonic wave propagating along the surface of the subject from the digitized signal. The time measuring means 32 can also be configured.

In the apparatus according to the first embodiment shown in FIG. 7, the wedge members 12 and 22 of the ultrasonic probes 10 and 20 are made of polystyrene, and the array directions of the transducer arrays 11 _{1 to} 11 ₁₆ and 21 _{1 to} 21 ₁₆ are arranged. The spot welded portion 2 was measured so that the width of the vibrator was 0.8 mm and the incident angle of the ultrasonic wave on the upper plate surface was 34.7 °. Thirty samples prepared by stacking two steel plates having a thickness of 2.6 mm and spot welding were used as measurement targets. Further, the ultrasonic probe 10 and the ultrasonic probe 20 are brought into contact with each other on a flat steel plate having a thickness of 2.6 mm without a spot welded portion, and the transducer array 11 _{1 of the} ultrasonic probe 10 is contacted. the ultrasonic wave transmitted from to 11 _16, with transmission time of the reception ultrasonic wave in the case of reception by the transducer array 21 ₁ to 21 ₁₆ of the ultrasonic probe 20 as a reference (reference transmission time) . Compare the transmission time of the received ultrasonic wave with the reference transmission time, and (| received ultrasonic wave transmission time-reference transmission time | / reference transmission time) is less than the threshold value (0.5% in this example) In some cases, it is determined that the received ultrasonic wave does not include the molten and solidified structure 2b in its propagation path. In the measurement of the nugget diameter, in the same way as in FIG. 5, among the ultrasonic propagation paths of the transducer arrays 11 _{1 to} 11 ₁₆ and the transducer arrays 21 _{1 to} 21 ₁₆ , the propagation path of the ultrasonic waves that do not include the molten solidified tissue 2 b. And the length in the array arrangement direction of the inner region surrounded by the intersecting solid lines was obtained. An example is shown in FIG. Further, in order to display the presence of the melt-solidified structure 2b in an easy-to-understand manner, the two-dimensional display shown in FIG. 9 was performed. In FIG. 9, the two-dimensional region between the ultrasonic probe 10 and the ultrasonic probe 20 is divided into predetermined microelements (size of 0.2 mm × 0.2 mm in FIG. 9) and melted and solidified. The elements on the path determined not to include the tissue 2b are displayed in white. FIG. 9 is a two-dimensional display of the example shown in FIG.

FIG. 10 shows a measurement result (according to the present invention) by the apparatus of the first embodiment shown in FIG. In FIG. 10, the horizontal axis represents the nugget diameter obtained as a result of the cutting test, and the vertical axis represents the nugget diameter obtained by the method of the present invention to display a scatter diagram. According to FIG. 10, it can be seen that all the measured values are within ± 0.5 mm, and a highly reliable measurement result is obtained.

  For comparison with the prior art, the measurement time was compared between the method of the present invention and the method disclosed in Patent Document 6. In the method of the present invention, the measurement time per sample averaged 3.5 seconds, whereas in the method disclosed in Patent Document 6, measurement accuracy comparable to that of the apparatus according to the present invention was obtained. The required measurement time per sample averaged about 30 seconds. In the method disclosed in Patent Document 6, the measurement time is long because the ultrasonic probe and the welded solidified structure cannot be aligned in a short time. It has been clarified again that Patent Document 6 is difficult to apply to spot welded part soundness evaluation in the field where a short measurement time is required. By using the apparatus of this embodiment, it is possible to perform a spot welded portion soundness evaluation with good accuracy in a short time. Furthermore, according to the display of FIG. 9, since the positional relationship between the ultrasonic probe 10 and the ultrasonic probe 20 and the nugget can be clearly grasped, the operator can perform the measurement work with peace of mind.

FIG. 11 shows an example of an apparatus for carrying out the first reference example . Hereinafter, the description of the parts common to FIG. 7 will be omitted. This apparatus is different from the apparatus shown in FIG. 7 in that peak value detection means 33 for detecting the amplitude of the ultrasonic wave from the received ultrasonic wave signal extracted by the gate means 31 is used. The signal amplified by the ultrasonic transmitter / receiver 30 is A / D converted, and the gate means 31 and the peak are detected by software so that the amplitude of the ultrasonic wave propagating along the surface of the subject is detected from the digitized signal. The value detection means 33 can also be configured.

In the apparatus of the first reference example shown in FIG. 11, the wedge members 12 and 22 of the ultrasonic probes 10 and 20 are made of polystyrene, and the array arrangement directions of the transducer arrays 11 _{1 to} 11 ₁₆ and 21 _{1 to} 21 ₁₆ are arranged. The spot welded portion 2 was measured so that the width of the vibrator was 0.8 mm and the incident angle of the ultrasonic wave on the upper plate surface was 34.7 °. Thirty samples prepared by stacking two steel plates having a thickness of 2.6 mm and spot welding were used as measurement targets. Further, the ultrasonic probe 10 and the ultrasonic probe 20 are brought into contact with each other on a flat steel plate having a thickness of 2.6 mm without a spot welded portion, and the transducer array 11 _{1 of the} ultrasonic probe 10 is contacted. the ultrasonic wave transmitted from to 11 _16, with the amplitude of the reception ultrasonic wave in the case of reception by the transducer array ₂₁ 1 _{to 21 16} of the ultrasonic probe 20 as a reference (reference amplitude). The amplitude of the received ultrasonic wave is compared with the reference amplitude, and if (the amplitude of the received ultrasonic wave / reference amplitude) does not fall below the threshold value (−6 dB in this example), the received ultrasonic wave is propagated. It was determined that the molten solidified structure 2b was not included in the path. In the measurement of the nugget diameter, in the same way as in FIG. 5, among the ultrasonic propagation paths of the transducer arrays 11 _{1 to} 11 ₁₆ and the transducer arrays 21 _{1 to} 21 ₁₆ , the propagation path of the ultrasonic waves that do not include the molten solidified tissue 2 b. And the length in the array arrangement direction of the inner region surrounded by the intersecting solid lines was obtained. An example is shown in FIG. Further, in order to display the presence of the melt-solidified structure 2b in an easy-to-understand manner, the two-dimensional display shown in FIG. 13 was performed. The two-dimensional display method is the same as that described with reference to FIG. FIG. 13 is a two-dimensional display of the example shown in FIG. In the example shown in FIGS. 12 to 13, the nugget is located close to the transducer arrays 11 _{1 to} 11 ₁₆ that transmit the waves.

The first device by that measurement results of the reference example shown in FIG. 11 is shown in FIG. 14. In FIG. 14, the horizontal axis represents the nugget diameter obtained as a result of the cutting test, and the vertical axis represents the nugget diameter obtained by the method of the first reference example , and the scatter diagram is displayed. According to FIG. 14, all measured values are within ± 0.5 mm, and it can be seen that highly reliable measurement results can be obtained.

For comparison with the prior art, the measurement time was compared between the method of the first reference example and the method disclosed in Patent Document 6. In the method of the first reference example, the average measurement time per sample was 3.5 seconds, whereas in the method shown in Patent Document 6, the measurement accuracy was comparable to that of the apparatus according to the first reference example. The average measurement time per sample necessary to obtain the value was about 30 seconds. In the method disclosed in Patent Document 6, the measurement time is long because the ultrasonic probe and the welded solidified structure cannot be aligned in a short time. It has been clarified again that Patent Document 6 is difficult to apply to spot welded part soundness evaluation in the field where a short measurement time is required. By using the apparatus of the first reference example , it is possible to perform a spot welded portion soundness evaluation with high accuracy in a short time. Furthermore, according to the display of FIG. 13, since the positional relationship between the ultrasonic probe 10, the ultrasonic probe 20, and the nugget can be clearly grasped, the operator can perform measurement work with peace of mind.

Hereinafter, a second reference example and a second embodiment of the present invention will be described with reference to the drawings. The second embodiment corresponds to claims 2 and 4 . Descriptions of parts common to the first reference example and the first embodiment are omitted.

These second reference example, in the second embodiment, by the ultrasonic probe 20 provided with an ultrasonic probe 10 having a transducer array 11 transducer array 21, planar path shown in FIG. 15 It receives the ultrasonic wave that has propagated through (the path seen from the top surface of the metal plate). In addition to each transducer of the transmitting transducer array that directly faces each transducer of the receiving transducer array, this propagation path includes ultrasonic waves transmitted from one of the adjacent transducers for transmitting. Is received. The ultrasonic waves transmitted by the transducers 11 _i (i = 1, 2,..., 8) of the transducer array 11 are converted into the transducers 21 _i and 21 _{i + 1} (i = 1, 2,..., 8) of the transducer array 21. , And the ultrasonic waves transmitted by the transducers 21 _i (i = 9, 10,..., 16) of the transducer array 11 are transducers 21 _i-1 and 21 _{i of the} transducer array 21. By receiving using (i = 9, 10,..., 16), the number of propagation paths that propagate obliquely increases, and at an intermediate position of the propagation path, ½ of the width of the transducer array in the array arrangement direction. Since the ultrasonic wave propagation paths are arranged every other time, it is apparently the same effect as arranging twice the number of transducers having a half width.

  If the molten solidified structure 2b is included in the propagation path shown in FIG. 15, the amplitude and transmission time of the received ultrasonic wave change as described above.

FIG. 16 shows that the ultrasonic probe 10 and the ultrasonic probe 20 are sandwiched between the spot welded portions 2 as described above on a sample obtained by spot welding with two steel plates having a thickness of 2.6 mm. Of the ultrasonic waves transmitted from the transducers 11 _{1 to} 11 ₁₆ of the ultrasonic probe 10 so as to face each other, the ultrasonic wave of the propagation path shown in FIG. After receiving by the sub-elements 21 _{1 to} 21 ₁₆ , the received ultrasonic wave form is compared with the reference, and the received ultrasonic wave whose form is different from the reference is selected and displayed (see FIG. 16 is displayed using □). Here, the amplitude was used as the form of the received ultrasonic wave. In addition, the ultrasonic probe 10 and the ultrasonic probe 20 are brought into contact with each other on a flat steel plate having a thickness of 2.6 mm that does not have a spot weld, and the transducers 11 ₁ to 11 of the ultrasonic probe 10 are brought into contact with each other. the ultrasonic wave transmitted from the 11 ₁₆ was used as a reference amplitude wave receiving ultrasound in the case of reception by the transducer ₂₁ 1 _{to 21 16} of the ultrasonic probe 20. Specifically, the codes P _{1 to} P ₃₁ are sequentially added to the path shown in FIG. 15 to obtain (the amplitude of the received ultrasonic wave / the reference amplitude) in the order of the codes, and the interpolation is performed as shown in FIG. An amplitude profile was created. The width Wa of the portion where the amplitude profile falls below a predetermined threshold value Ta (here, −6 dB with respect to the reference amplitude) is different from the reference, and the width Wa is obtained. Since the width Wa is an existing range of a path whose received ultrasonic wave form is different from the reference, the width Wa can be said to be a nugget diameter.

FIG. 17 shows an example of an apparatus for carrying out the second reference example . Hereinafter, the description of the parts common to the first reference example will be omitted.

In the apparatus of the second reference example shown in FIG. 17, the wedge members 12 and 22 of the ultrasonic probes 10 and 20 are made of polystyrene, and the array directions of the transducer arrays 11 _{1 to} 11 ₁₆ and 21 _{1 to} 21 ₁₆ are arranged. The spot welded portion 2 was measured so that the width of the vibrator was 0.8 mm and the incident angle of the ultrasonic wave on the upper plate surface was 34.7 °. The propagation path of the received ultrasonic wave is as shown in FIG. Thirty samples prepared by stacking two steel plates having a thickness of 2.6 mm and spot welding were used as measurement targets. Further, the ultrasonic probe 10 and the ultrasonic probe 20 are brought into contact with each other on a flat steel plate having a thickness of 2.6 mm without a spot welded portion, and the transducer array 11 _{1 of the} ultrasonic probe 10 is contacted. the ultrasonic wave transmitted from to 11 _16, with the amplitude of the reception ultrasonic wave in the case of reception by the transducer array ₂₁ 1 _{to 21 16} of the ultrasonic probe 20 as a reference (reference amplitude). When the amplitude of the received ultrasonic wave is compared with the reference amplitude, and (the amplitude of the received ultrasonic wave / reference amplitude) is lower than the threshold value (−6 dB in this example), the received ultrasonic wave has its propagation path. Is determined to contain the melt-solidified structure 2b. In the measurement of the nugget diameter, the method described with reference to FIG. 16 was used. Instead of calculating (the amplitude of the received ultrasonic wave / the reference amplitude), if the amplification degree in the ultrasonic transmitter / receiver 30 is changed for each propagation path so that the reference amplitude in each propagation path is constant, it is received. The amplitude of the wave ultrasonic wave itself can be compared with the threshold value Ta. The signal amplified by the ultrasonic transceiver 30 is A / D converted, and the gate means 31 and the peak are detected by software so that the amplitude of the ultrasonic wave propagating along the surface of the subject is detected from the digitized signal. In the case of configuring the value detection means 33, if the received ultrasonic wave digitized so that the reference amplitude in each propagation path is constant is multiplied by a predetermined coefficient, the amplitude of the received ultrasonic wave itself is obtained. The threshold value Ta can be compared.

The second reference example device by that measurement results of that shown in FIG. 17 is shown in FIG. 18. In FIG. 18, the horizontal axis represents the nugget diameter obtained as a result of the cutting test, and the vertical axis represents the nugget diameter obtained by the method of the second reference example , and the scatter diagram is displayed. As can be seen from FIG. 18, all the measured values are within ± 0.5 mm, and a highly reliable measurement result is obtained.

For comparison with the prior art, the measurement time was compared between the method of the second reference example and the method disclosed in Patent Document 6. In the method of the second reference example , the measurement time per sample was an average of 3.5 seconds, whereas in the method shown in Patent Document 6, the measurement accuracy was comparable to that of the apparatus according to the second reference example. The average measurement time per sample necessary to obtain the value was about 30 seconds. In the method disclosed in Patent Document 6, the measurement time is long because the ultrasonic probe and the welded solidified structure cannot be aligned in a short time. It has been clarified again that Patent Document 6 is difficult to apply to spot welded part soundness evaluation in the field where a short measurement time is required. By using the apparatus of the second reference example , it is possible to perform a spot welded portion soundness evaluation with high accuracy in a short time.

Next, the apparatus of 2nd Embodiment which is another example of a 2nd reference example is demonstrated. FIG. 19 shows the form of ultrasonic waves received in each of the propagation paths connecting the plurality of transmission positions and the plurality of reception positions, using transmission time as the form of the reception ultrasonic waves compared with the reference. Shows an example of a device that extracts a propagation path in which a nugget exists from the propagation paths and calculates a nugget diameter based on the existence range of the propagation path in which the extracted nugget exists. . Hereinafter, description of parts common to the first embodiment will be omitted.

In the apparatus of the second embodiment shown in FIG. 19, the wedge members 12 and 22 of the ultrasonic probes 10 and 20 are made of polystyrene, and the array arrangement directions of the transducer arrays 11 _{1 to} 11 ₁₆ and 21 _{1 to} 21 ₁₆ are arranged. The spot welded portion 2 was measured so that the width of the vibrator was 0.8 mm and the incident angle of the ultrasonic wave on the upper plate surface was 34.7 °. The propagation path of the received ultrasonic wave is as shown in FIG. Thirty samples prepared by stacking two steel plates having a thickness of 2.6 mm and spot welding were used as measurement targets. Further, the ultrasonic probe 10 and the ultrasonic probe 20 are brought into contact with each other on a flat steel plate having a thickness of 2.6 mm without a spot welded portion, and the transducer array 11 _{1 of the} ultrasonic probe 10 is contacted. the ultrasonic wave transmitted from to 11 _16, with transmission time of the reception ultrasonic wave in the case of reception by the transducer array 21 ₁ to 21 ₁₆ of the ultrasonic probe 20 as a reference (reference transmission time) . The transmission time of the received ultrasonic wave is compared with the reference transmission time, and (| received ultrasonic wave transmission time−reference transmission time | / reference transmission time) is equal to or greater than the threshold value Tt (0.5% in this example). In this case, it is determined that the received ultrasonic wave includes the molten and solidified structure 2b in the propagation path (indicated by a square in FIG. 20). In the measurement of the nugget diameter, as shown in FIG. 20, for example, the paths P _{1 to} P ₃₁ are sequentially added to the path shown in FIG. 15, and the received ultrasonic wave transmission time-reference transmission time | / Reference transmission time) was obtained, and the transmission time profile shown in FIG. 20 was created by performing interpolation. The width Wt of the portion where the transmission time profile exceeds the predetermined threshold value Tt was obtained.

FIG. 21 shows a measurement result (according to the present invention) by the apparatus of the second embodiment shown in FIG. In FIG. 21, the horizontal axis represents the nugget diameter obtained as a result of the cutting test, and the vertical axis represents the nugget diameter obtained by the method of the present invention to display a scatter diagram. According to FIG. 21, it can be seen that all the measured values are within ± 0.5 mm, and a highly reliable measurement result is obtained.

For comparison with the prior art, the measurement time was compared between the method of the present invention and the method disclosed in Patent Document 6. In the method of the present invention, the measurement time per sample averaged 3.5 seconds, whereas in the method disclosed in Patent Document 6, measurement accuracy comparable to that of the apparatus according to the present invention was obtained. The required measurement time per sample averaged about 30 seconds. In the method disclosed in Patent Document 6, the measurement time is long because the ultrasonic probe and the welded solidified structure cannot be aligned in a short time. It has been clarified again that Patent Document 6 is difficult to apply to spot welded part soundness evaluation in the field where a short measurement time is required. By using the apparatus of the second embodiment, it is possible to perform spot welded portion soundness evaluation with high accuracy in a short time.

In the description of the above embodiment and reference examples, an example in which the amplitude of ultrasonic waves is used as the form of received ultrasonic waves used for determining whether or not the melted solidified tissue 2b is included in the propagation path of the received ultrasonic waves, ultrasonic waves However, it is of course possible to determine whether or not the melted and solidified structure 2b is included by combining the two. In addition to the above, a pulse width, a frequency, a phase, and the like can be used as a form of received ultrasonic waves.

Note that the measurement accuracy can be further increased by reducing the width of the transducers in the array arrangement direction of the transducer arrays 11 _{1 to} 11 _N and 21 _{1 to} 21 _N. The width of the transducers in the array arrangement direction of the transducer arrays 11 _{1 to} 11 _N and 21 _{1 to} 21 _N may be determined according to the required measurement accuracy.

  In this embodiment, since the ultrasonic probe provided with the transducer array is used on both the transmission side and the reception side, the configuration is simple. In addition, it is also possible to use a plurality of probes juxtaposed on either one or both, or to scan and use a single probe.

  Furthermore, in the above description, the present invention is applied to the welding inspection of the metal plate, but the application target of the present invention is not limited to this. Further, the number of welds is not limited to two, and the evaluation of the soundness of the spot welded portion is not limited to the one that measures only the nugget diameter.

The perspective view which shows the basic composition of embodiment of this invention Sectional drawing which shows the propagation path of an ultrasonic wave for demonstrating the principle of 1st reference example and 1st Embodiment of this invention Same top view Cross section of spot weld Explanatory drawing which shows the relationship between the ultrasonic propagation path | route and the nugget which do not contain the melt solidification structure | tissue in a 1st reference example . Explanatory drawing which shows the relationship between the ultrasonic propagation path | route and the nugget which do not contain the melt solidification structure | tissue in 1st Embodiment of this invention. The perspective view including the partial block diagram which shows the example of the apparatus for implementing 1st Embodiment of this invention Explanatory drawing which shows an example of the measurement result by the apparatus of 1st Embodiment Explanatory drawing which similarly shows an example of a measurement result display Diagram showing the accuracy of measurement results according to the method of the present invention The perspective view including the partial block diagram which shows the example of the apparatus for implementing a 1st reference example Explanatory drawing which shows an example of the measurement result by the apparatus of the first reference example Explanatory drawing which similarly shows an example of a measurement result display Diagram showing the accuracy of measurement results A plan view showing a propagation path of ultrasonic waves for explaining the principle of the second reference example and the second embodiment of the present invention . Similarly, an illustration of the nugget diameter measurement method The perspective view including the partial block diagram which shows the example of the apparatus for implementing a 2nd reference example Diagram showing the accuracy of the measurement results by the device of the second reference example The perspective view including the partial block diagram which shows the example of the apparatus for implementing 2nd Embodiment of this invention Explanatory drawing of the nugget diameter measuring method in the apparatus of 2nd Embodiment Diagram showing the accuracy of measurement results Cross section for explaining spot welds

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 101a ... Upper plate 1b, 101b ... Lower plate 2, 102 ... Spot welding part 2a, 102a ... Nugget 2b ... Melt-solidified structure 10, 20 ... Ultrasonic probe 11, 21 ... Vibrator array
DESCRIPTION OF SYMBOLS 25 ... Switch circuit 26 ... Switch circuit 30 ... Ultrasonic transmitter / receiver 31 ... Gate means 32 ... Time measuring means 33 ... Peak value detection means

Claims (4)

Ultrasonic wave propagating in the cross-section formed by the direction along the surface of the metal plate or spot weld and the thickness direction in the ultrasonic evaluation method for spot welds formed by superposing and welding a plurality of metal plates Is referred to as ultrasound propagating along the surface of the subject,
The ultrasonic wave propagating along the surface of the subject from multiple wave transmission positions of the metal plate outside the spot welded portion in multiple directions is transmitted by an ultrasonic probe equipped with a transducer array,
Ultrasound propagated along the surface of the subject not including the spot weld in the propagation path at the plurality of receiving positions of the metal plate outside the spot weld, and the surface of the subject including the spot weld in the propagation path The ultrasonic wave propagating along the surface is received by an ultrasonic probe equipped with a transducer array,
In each of the propagation paths connecting the plurality of transmission positions and the plurality of reception positions, the transmission time of the received ultrasonic waves received is compared with the reference transmission time, and the (| −reference transmission time | / reference transmission time) is equal to or less than a threshold value, it is determined that the received ultrasonic wave does not include a nugget in the propagation path, and a propagation path in which no nugget exists in the propagation path And the nugget diameter is calculated based on a region surrounded by a propagation path in which the extracted nugget does not exist. Ultrasonic wave propagating in the cross-section formed by the direction along the surface of the metal plate or spot weld and the thickness direction in the ultrasonic evaluation method for spot welds formed by superposing and welding a plurality of metal plates Is referred to as ultrasound propagating along the surface of the subject,
The ultrasonic wave propagating along the surface of the subject from multiple wave transmission positions of the metal plate outside the spot welded portion in multiple directions is transmitted by an ultrasonic probe equipped with a transducer array,
Ultrasound propagated along the surface of the subject not including the spot weld in the propagation path at the plurality of receiving positions of the metal plate outside the spot weld, and the surface of the subject including the spot weld in the propagation path The ultrasonic wave propagating along the surface is received by an ultrasonic probe equipped with a transducer array,
In each of the propagation paths connecting the plurality of transmission positions and the plurality of reception positions, the transmission time of the received ultrasonic waves received is compared with the reference transmission time, and the (| −reference transmission time | / reference transmission time) is equal to or greater than the threshold value, it is determined that the received ultrasonic wave includes a nugget in the propagation path, and a propagation path in which the nugget exists is selected from the propagation paths. A method for evaluating spot welds by ultrasonic waves, characterized in that the nugget diameter is calculated based on the existence range of the propagation path in which the extracted nugget exists. Ultrasonic wave propagating in a cross section formed by the direction along the surface and the thickness direction of a metal plate or spot welded part in an ultrasonic evaluation apparatus for spot welded parts formed by superimposing and welding a plurality of metal plates Is referred to as ultrasound propagating along the surface of the subject,
An ultrasonic probe including a transducer array for transmitting ultrasonic waves propagating along the surface of the subject in a plurality of directions from a plurality of transmission positions of a metal plate outside the spot weld,
Ultrasound propagated along the surface of the subject not including the spot weld in the propagation path at the plurality of receiving positions of the metal plate outside the spot weld, and the surface of the subject including the spot weld in the propagation path An ultrasonic probe with a transducer array that receives ultrasonic waves propagating along
In each of the propagation paths connecting the plurality of transmission positions and the plurality of reception positions, the transmission time of the received ultrasonic waves received is compared with the reference transmission time, and the (| −reference transmission time | / reference transmission time) is equal to or less than a threshold value, it is determined that the received ultrasonic wave does not include a nugget in the propagation path, and a propagation path in which no nugget exists in the propagation path Means for calculating a nugget diameter based on a region surrounded by a propagation path in which the extracted nugget does not exist;
An apparatus for evaluating spot welds using ultrasonic waves. Ultrasonic wave propagating in a cross section formed by the direction along the surface and the thickness direction of a metal plate or spot welded part in an ultrasonic evaluation apparatus for spot welded parts formed by superimposing and welding a plurality of metal plates Is referred to as ultrasound propagating along the surface of the subject,
An ultrasonic probe including a transducer array for transmitting ultrasonic waves propagating along the surface of the subject in a plurality of directions from a plurality of transmission positions of a metal plate outside the spot weld,
Ultrasound propagated along the surface of the subject not including the spot weld in the propagation path at the plurality of receiving positions of the metal plate outside the spot weld, and the surface of the subject including the spot weld in the propagation path An ultrasonic probe with a transducer array that receives ultrasonic waves propagating along
In each of the propagation paths connecting the plurality of transmission positions and the plurality of reception positions, the transmission time of the received ultrasonic waves received is compared with the reference transmission time, and the (| −reference transmission time | / reference transmission time) is equal to or greater than the threshold value, it is determined that the received ultrasonic wave includes a nugget in the propagation path, and a propagation path in which the nugget exists is selected from the propagation paths. Means for extracting and calculating the nugget diameter based on the existence range of the propagation path in which the extracted nugget exists;
An apparatus for evaluating spot welds using ultrasonic waves.

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