JP4084755B2 - Eddy current flaw detector - Google Patents

Description

  The present invention relates to an eddy current flaw detector that detects a defect generated in a conductive subject such as a metal material using electromagnetic induction, and more particularly to an eddy current flaw detector that detects a surface defect of a welded structure.

  Defects such as scratches present in the subject by inducing an eddy current in the subject by applying an alternating magnetic field using a coil to the surface of a conductive subject such as metal and detecting a change in the impedance of the coil due to this. There is known an eddy current flaw detection device for detecting the above. The eddy current flaw detection apparatus is used for flaw detection work of structures such as lines for manufacturing coils of steelworks, vehicles, ships, bridges, plants, and the like (see Patent Documents 1 and 2).

  For example, in a steelworks line, a number of sensors are arranged along the width direction of a coil that runs at high speed to detect scratches on the coil and the like, and the signals detected by each sensor are automatically recorded on a chart. In addition, the position corresponding to the scratch is marked. In such a line, the positional relationship between the coil as the subject and the sensor is fixed in advance, and a plurality of sensors are arranged, so that the position of the wound can be easily found. Further, since the coil is flat with almost no irregularities, it is easy to automatically detect a signal corresponding to a scratch.

On the other hand, in the flaw detection work for a structure, the shape of the flaw is complicated and diverse. Therefore, the operator needs to hold and operate the sensor unit. Therefore, it is difficult to scan the sensor while keeping the positional relationship between the sensor and the subject constant, and there is a problem that the flaw detection conditions are not constant due to the tilt or lift-off of the sensor. In the conventional flaw detection apparatus, an operator visually checks a Lissajous waveform with respect to a change in impedance and an axis sweep display to determine the presence or absence of a defect. Therefore, especially when inspecting a test subject with irregularities on its surface, such as a welded part, the presence of noise due to welding ripples or laps, or the detection of defective parts due to changes in flaw detection conditions due to sensor tilt or lift-off. Requires skill. In addition, such an eddy current flaw detector can determine the presence or absence of a defect, but cannot measure the length of the flaw or automatically record the position.
Japanese Patent Laid-Open No. 10-068715 Japanese Patent Laid-Open No. 08-101169

  The present invention provides a jig that can maintain the positional relationship of the probe with respect to the subject with a simple configuration in an eddy current flaw detector using a portable probe that inspects a subject having various irregularities such as a welded portion. The purpose is to do. Still another object of the present invention is to make it possible to detect the positional relationship between the probe and the subject in such a jig.

  The jig for an eddy current flaw detector according to the present invention is a jig used in an eddy current flaw detector that generates an eddy current by applying a magnetic field to a subject and thereby searches for a flaw existing in the subject. And a portable means for detecting the eddy current of the subject, a fixing means for fixing the angle of the probe with respect to the subject, and a movable mechanism capable of moving the probe in a predetermined direction while maintaining this angle It is characterized by having.

  For example, the fixing means includes a grip portion that grips the probe from both sides thereof, and the grip force can be adjusted. The probe is rotatable with respect to the grip portion when the grip force is equal to or greater than a predetermined value. The rotation angle is fixed with respect to the grip portion when it is equal to or greater than a predetermined value.

  The movable mechanism includes, for example, a roller, and the rotation axis of the roller is arranged so as to be orthogonal to the rotation axis of the probe. Thus, the probe can be scanned along a certain direction with respect to a subject such as a welded portion while maintaining a certain angle.

  At this time, in order to grasp the positional relationship of the probe with respect to the subject, it is preferable to provide an encoder for detecting the rotation amount of the roller on the rotation shaft of the roller.

  Further, for example, the fixing means includes a grip portion for gripping the probe and a measure tape, and the grip portion is fixed at a predetermined angle to the tip of a blade curved in the width direction of the measure tape. At this time, it is preferable to provide an encoder for detecting the feed amount of the blade on the take-up shaft of the major tape.

  As described above, according to the present invention, in a eddy current flaw detection apparatus using a portable probe for inspecting a subject having various irregularities such as a welded portion, a treatment capable of maintaining a constant positional relationship of the probe with respect to the subject. The tool can be provided in a simple configuration. Furthermore, the positional relationship between the probe and the subject can be detected with such a jig.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view schematically showing an outline of eddy current exploration work using the eddy current exploration apparatus according to the embodiment of the present invention. Since FIG. 1 is a diagram for explaining the flaw detection work, only a part of the configuration of the eddy current flaw detection apparatus is schematically shown in the drawing.

  In FIG. 1, for example, a fillet weld W exists in a structure S that is a subject, and the entire surface of the structure S is coated with, for example, a rust inhibitor or a paint. The eddy current flaw detector 10 according to the first embodiment includes a probe 11 that applies an alternating magnetic field to the subject S and detects a change in eddy current generated in the subject S. The probe 11 is connected to the main body 13 of the eddy current flaw detector 10 via the cable 12, and the signal detected by the probe 11 is analyzed and processed in the main body 13. In addition, a coil (not shown) for generating an alternating magnetic field provided in the probe 11 is supplied with power from the main body 13 via the cable 12, and the alternating magnetic field controls the power supplied from the main body 13. Is done.

  The operator grasps the probe 11 and moves the probe 11 along the welded portion W (for example, in the direction of arrow A) while maintaining a certain angle and distance with respect to the subject S to scan the welded portion W. In addition, although the angle and distance of the probe 11 with respect to the test subject S are maintained by the mechanism demonstrated below, they are abbreviate | omitted in this figure. Further, as will be described later, a change in the impedance of the coil in the probe 11 due to the eddy current of the subject S is sent to the main body 13 and processed.

  2 is a perspective view of the probe operation unit 20 according to the first embodiment to which the probe 11 is attached. FIGS. 3 and 4 are a plan view and a side view of the probe operation unit 20, respectively. FIG. 1 is a perspective view when the probe operation unit 20 is viewed obliquely from below.

  The probe 11 has a substantially cylindrical shape, and a cable 12 is connected to the upper end thereof. The probe 11 is arranged inside a gripping part 21 in which a U-shaped depression is formed, and shafts 22 extend from both side walls of the probe 11 to shaft holes provided on the inner side surface of the U-shaped depression. Each is inserted. That is, the probe 11 can rotate around the shaft axis O. In addition, a collar 23 formed of, for example, a synthetic resin is provided around the shaft 22 between the inner side wall of the grip portion 21 into which the shaft 22 is inserted and the probe 11.

  On the other hand, a slit 24 is formed in a direction that is perpendicular to the shaft axis O at a portion that contacts the U-shaped bottom of the grip portion 21. A bolt 25 that is orthogonal to the slit 24 and penetrates from one side wall to the other side wall is attached to the grip portion 21, and a rotary lock nut 26 is screwed onto the tip of the bolt 25. That is, when the rotation lock nut 26 is tightened, both side walls of the grip portion 21 are pressed, and the grip portion 21 is bent due to the presence of the slit 24. Thereby, the space | interval of a U-shaped part is narrowed, the collar 23 is pinched | interposed by the holding part 21, and the rotation angle around the shaft axis O of the probe 11 is fixed by the frictional force.

  A roller holding portion 27 is disposed below the gripping portion 21, and a roller (for example, a rubber roller) 28, a momentary switch 29, and an encoder 30 are provided on the roller holding portion 27. The roller 28 guides the probe operation unit 20 in the scanning direction and detects the amount of movement thereof, and the rotation axis O ′ is orthogonal to the shaft axis O and is connected to the encoder 30. Therefore, when the operator holds the probe operation unit 20 and moves the probe 11 along the inspection site (welding portion W), the roller 28 rotates, and the amount of rotation is detected by the encoder 30 and passed through the signal cable 31. To the main body 13. The momentary switch 29 is for controlling the start and end of data acquisition in the probe 11 and the encoder 30, and is connected to the main body 13 by a signal line (not shown).

  Next, FIG. 5 shows an example of a Lissajous waveform on the XY plane (vector display) corresponding to the impedance change in the coil of the probe 11 due to the eddy current generated in the subject S.

  The phase of the Lissajous waveform varies depending on the type of unevenness present in the subject S, and its amplitude depends on the depth. Also, for example, when the step forming the unevenness in the scanning direction transitions from a relatively high position to a low position, a waveform appears in the first quadrant, and when a transition occurs from a relatively low position to a high position, A waveform appears in the third quadrant. That is, if the unevenness is of the same type, a signal having a phase difference of approximately 180 ° is detected depending on whether the step changes from high to low or from low to high in the scanning direction.

  The purpose of the flaw detection work is to detect a specific type of unevenness corresponding to the flaw, and in this case, a waveform having an amplitude of a predetermined value or more in a specific phase is identified as a flaw in the flaw detection work. Conventionally, the presence or absence of a flaw has been determined by visually confirming a Lissajous waveform that appears instantaneously during probe scanning.

On the other hand, in the present embodiment, among the detected signals, a predetermined phase difference centered on a predetermined phase θ ₀ or phase (θ ₀ + 180 °) whose phase has the highest correlation with the scratch to be searched. By extracting only signals within a range of ± Δθ (for example, Δθ = 10 °) and extracting only signals having an amplitude equal to or larger than a predetermined value, noise is removed and a flaw that is a search target is detected.

  Hereinafter, with reference to FIG. 6 and FIG. 7, the scratch determination process in the present embodiment will be described in more detail. FIG. 6 is a flowchart of the determination process of the present embodiment, and FIG. 7 shows an example of the result of signal processing at this time.

  In step S100, it is determined whether or not the momentary switch 29 is turned on. That is, when the operator presses the operation button of the momentary switch 29 and the switch is turned on, the process of step S102 is executed. In step S102, signal data is acquired from the encoder 30 and the probe 11 and recorded in a recording medium (not shown) in association with each other. The capturing of the signal data is terminated when the momentary switch 29 is operated again and turned off.

In step S104, the signal acquired from the probe 11 is subjected to phase filter processing, and only signals in the range of ± Δθ centered on the predetermined phases θ ₀ and (θ ₀ + 180 °) are extracted. At this time, the phase of the input signal is advanced by (90 ° −θ ₀ ), and the signal of phase θ ₀ is converted into a signal having a phase of 90 ° (along the Y axis). Next, in step S106, amplitude filtering is performed, and only signals having a voltage value corresponding to the impedance component in the Y-axis direction that is greater than or equal to a predetermined value (eg, + 2V) or less than a predetermined value (eg, −2V) are extracted. (A signal whose absolute value is smaller than a predetermined value is removed).

  In step S108, the movement distance from the position where the momentary switch 29 is pressed is calculated from the rotation angle of the roller 28 detected in the encoder 30, and the signal extracted in steps S104 and S106 is calculated with this movement distance as the horizontal axis. A voltage value corresponding to the Y-axis direction is displayed in a graph on a screen provided in the main body 13, for example.

FIG. 7A is a graph showing the relationship between the signal voltage input from the probe 11 before the filtering process and the moving distance. However, the voltage on the vertical axis indicates the voltage corresponding to the Y-axis direction when the phase of the input signal is advanced by (90 ° −θ ₀ ). On the other hand, FIG. 7B is a signal waveform after the phase filter process and the amplitude filter process are performed on the signal of FIG. 7A, and corresponds to the graph displayed on the screen in step S108.

  In FIG. 7B, the signal waveform swayed to the + side corresponds to, for example, a step portion that transitions from a relatively high position to a low position, and the signal waveform swayed to the − side is a position from a relatively low position to a high position. Corresponds to the step transition to. Therefore, a pair of signal waveforms changing from the + side to the-side corresponds to one scratch. In FIG. 7 (b), the first + side peak S1 and the subsequent-side valley S2 form a pair and correspond to one scratch. Further, the peak S3 and the valley S4 form a pair and correspond to the next scratch, and the peak S5 and the valley S6 further form a pair and correspond to the third scratch.

  The length of the wound is, for example, from the position where the signal reaches a predetermined value (for example, + 2V) at the rising edge (starting portion) of the mountain until the signal reaches the predetermined value (for example, −2V) at the rising edge (end portion) of the valley. Expressed by distance. For example, the length of the flaw represented by the pair (S1, S2) is D1, and the length of the flaw represented by the pair (S3, S4), (S5, S6) is D2, D3, respectively.

  As described above, according to the present embodiment, signals due to irregularities other than the scratch existing in the subject can be removed by the phase filter processing and the amplitude filter processing, and the determination operation of the scratch in the flaw detection operation is simple. It can be. In addition, the distance measurement means using a roller and an encoder can detect and record the positional relationship between the subject and the probe during the flaw detection operation, making it easy to mark the position of the scratch and measure dimensions such as length. Can be done.

  Moreover, in this embodiment, since the distance and inclination of the probe with respect to the subject are constant, the influence such as lift-off can be removed from the detection signal. Furthermore, in this embodiment, by providing a momentary switch in the probe operation unit, the operator can easily control the start and end of data acquisition, and waste of data acquisition can be eliminated.

  Next, a second embodiment of the present invention will be described with reference to FIGS. The basic configuration of the flaw detection apparatus of the second embodiment is the same as that of the first embodiment, and only the configuration of the probe operation unit is different from that of the first embodiment. Only the configuration different from that of the first embodiment will be described below.

  FIG. 8 is a plan view of the probe operation unit 40 of the flaw detector according to the second embodiment, and FIG. 9 is a front view thereof. The probe operation unit 40 is mainly composed of a grip part 41, a measure tape 42, and an encoder 30. The probe 11 is held at one end of the gripping portion 41 with its outer peripheral surface being sandwiched. Further, the other end of the grip portion 41 is connected to the tip 43 a of the blade 43 of the measure tape 42. The connection between the gripping part 41 and the blade 43 is fixed so that the gripping part 41 maintains a certain arrangement with respect to the surface of the blade 43. That is, the angle and distance of the gripping part 41 with respect to the blade surface are fixed.

  As is conventionally known, the blade 43 is accommodated in a state where it is wound around the axis Ob (see FIG. 10) in the housing 44 by, for example, a spring urging force, and is pulled out from the housing 44 by pulling the tip. The blade 43 is formed of a material having a predetermined rigidity such as metal, and the blade 43 is curved in the width direction. That is, the blade 43 is curved so that the outer surface becomes a convex surface during winding, and has a certain rigidity with respect to torsion with respect to the longitudinal axis. Therefore, the holding part 41 held at a constant angle with respect to the surface of the blade 43 holds the posture of the subject S with the rigidity of the blade 43 by fixing the housing 44 to the subject S. Is done. As a result, the posture of the probe 11 held by the gripper 41 with respect to the subject S can be stably held.

  The encoder 30 is connected to the winding shaft Ob of the measure tape 40, and the feed amount of the blade 43 is detected by the encoder 30 and sent to the main body 13. Further, the momentary switch 29 is provided in the housing 42 as in the first embodiment.

  As described above, also in the second embodiment, substantially the same effect as that of the first embodiment can be obtained.

In the present embodiment, the phase of the signal detected by the probe (90 ° -θ ₀₎ proceed, but subjected to amplitude filter processing on values corresponding to the Y-axis component, directly theta ₀ direction and ( A component in the (θ ₀ + 180 °) direction may be calculated, and an amplitude filter process may be performed on a voltage value corresponding to the calculated component.

It is a typical perspective view of the eddy current exploration work using the eddy current exploration apparatus which is embodiment of this invention. It is the perspective view which looked at the probe operation part of 1st Embodiment with which the probe was attached from diagonally downward. It is a top view of a probe operation part. It is a side view of a probe operation part. It is an example of a Lissajous waveform when the impedance change by the eddy current which generate | occur | produced in the test subject is displayed as a vector. It is a flowchart of the determination process of this embodiment. It is an example of the graph which shows the relationship between the distance and signal (Y-axis component) before and after signal processing. It is a top view of the probe operation part of the flaw detection apparatus in 2nd Embodiment. It is a front view of the probe operation part of the flaw detection apparatus in 2nd Embodiment. It is a figure which draws the mode inside the measure tape housing of a 2nd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Eddy current flaw detector 11 Probe 13 Eddy current flaw detector main body 20, 40 Probe operation part 29 Momentary switch 30 Encoder S Subject

Claims (11)

A jig used in an eddy current flaw detection device that generates an eddy current by applying a magnetic field to a subject, thereby exploring a wound existing in the subject,
A portable probe that generates an alternating magnetic field and detects eddy currents in the subject;
Fixing means for fixing an angle of the probe with respect to the subject;
A movable mechanism capable of moving the probe in a predetermined direction while maintaining the angle ;
The fixing means includes a grip portion that grips the probe from both sides thereof and the grip force of which is adjustable, and the probe is rotatable with respect to the handle portion when the grip force is a predetermined value or less. The jig for an eddy current flaw detector is characterized in that a rotation angle is fixed with respect to the grip portion when the grip force is equal to or greater than the predetermined value . The jig for an eddy current flaw detector according to claim 1 , wherein the movable mechanism includes a roller, and the rotation axis of the roller is arranged so as to be orthogonal to the rotation axis of the probe. The eddy current flaw detector jig according to claim 1 , wherein an encoder for detecting a rotation amount of the roller is provided on a rotation shaft of the roller. A jig used in an eddy current flaw detection apparatus that generates an eddy current by applying a magnetic field to a subject, thereby exploring a wound existing in the subject,
A portable probe that generates an alternating magnetic field and detects eddy currents in the subject;
Fixing means for fixing an angle of the probe with respect to the subject;
A movable mechanism that allows the probe to move in a predetermined direction while maintaining the angle;
Said fixing means comprise a gripping portion and a measuring tape for gripping said probe, said gripper you characterized in that it is fixed at a predetermined angle at the tip of the blade is curved in the width direction of the measuring tape vortex Nagaresagu wound apparatus jig. Eddy Current device jig according to claim 4, characterized in that the encoder for detecting the movement amount of the blade to the winding axis of the measuring tape is provided. A jig used in an eddy current flaw detection apparatus that generates an eddy current by applying a magnetic field to a subject, thereby exploring a wound existing in the subject,
A portable probe that generates an alternating magnetic field and detects eddy currents in the subject;
Fixing means for fixing an angle of the probe with respect to the subject;
A movable mechanism capable of moving the probe in a predetermined direction while maintaining the angle;
The movable mechanism includes a roller for guiding the jig in the scanning direction of the probe, the fixing means fixes a rotation angle of the probe with respect to the gripping portion, and a rotation axis of the probe is scanned. Parallel to direction
A jig for an eddy current flaw detector characterized by that. An eddy current flaw detector provided with the eddy current flaw detection tool according to any one of claims 1, 4, and 6,
Phase filter processing means for extracting, from the signal detected by the probe, only a signal having a phase in a predetermined range centered on a predetermined phase in the vector display of the impedance of the signal,
The predetermined phase corresponds to the scratch
An eddy current flaw detector characterized by that. 8. The eddy current flaw detector according to claim 7, further comprising an amplitude filter processing unit that extracts only a signal having an absolute value of a signal component with respect to the predetermined phase equal to or greater than a predetermined value. 9. The eddy current flaw detection apparatus according to claim 8, further comprising distance information detection means for detecting a movement amount of the probe relative to the subject corresponding to the scanning of the probe. The eddy current exploration according to claim 9, wherein a switch for controlling start and end of capturing of a signal detected by the probe and a signal detected by the distance information means is provided in the probe operation unit. apparatus. 10. The eddy current according to claim 9, further comprising display means for displaying a signal component corresponding to the predetermined phase of the signal subjected to the phase filter processing means and the amplitude filter processing means in a graph corresponding to the movement amount. Exploration device.

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