JP2000111530A - Method and apparatus for crack flaw detection of welded part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method and an apparatus in which the crack of a welding beam is inspected stably and with high accuracy by using an eddy-current sensor and in which a crack part is judged with good accuracy even when the permeability of a material for an object to be inspected is different. SOLUTION: An eddy-current sensor probe 20 which is directed to a welding bead is provided. In addition, a bead copying mechanism which keeps a set height with reference to the welding beam with the attached sensor probe 20 and which can follow the uneven part of a bead wire is provided. A computing means 48 to which a movement signal by a flaw detection robot 10 movable along the bead wire and a detection signal by the eddy-current sensor are input, in which sampling data by the sensor is differentiated and processed and in which welded part crack data is output on the basis of its leak value is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for detecting a crack in a weld, and more particularly to a method and apparatus for detecting a crack in a weld, which is suitable for use in a crack inspection of a building constructed by welding metal plates.

[0002]

2. Description of the Related Art In a building such as a ship constructed by welding metal plates, crack inspection of a welded portion is required in order to use the building safely for a long period of time. Conventionally, magnetic particle flaw detection, liquid permeation, and the like have been known for such welding inspections.
The record of the crack has to be written or photographed. Therefore, eddy current flaw detection has recently attracted attention.

The basic principle of the conventional eddy current flaw detection method is as follows. An alternating current is passed through the eddy current sensor coil,
When one end of the coil is brought close to a metal to be inspected such as a weld seam, a circular eddy current is generated on the surface of the metal plate by electromagnetic induction. Further, the magnetic flux generated due to the eddy current acts in a direction to reduce the magnetic flux by the coil. If the inspection target has a crack defect, the direction of the eddy current on the surface of the inspection target changes, and the magnetic flux generated by the eddy current changes, thereby changing the electromotive force induced in the sensor coil. By detecting the change in the electromotive force, a crack defect can be inspected.

[0004]

However, the conventional eddy current flaw detection method has a problem in that the detection voltage differs even when the sensor coil is lifted off or the center of the sensor coil is displaced from the crack. Further, in the eddy current flaw detection method, a detection voltage differs for each material having different magnetic permeability of the target material such as a weld metal, a heat affected zone, and a base material. In particular, in a portion where three types of materials are complicated and complicated, such as monitoring of a heat-affected zone, there is a problem that a crack cannot be identified only by the peak value of the detection voltage of the crack.

The present invention pays attention to the above-mentioned conventional problems, and when performing a crack inspection of a welded portion, the relative position between the toe end of the bead and the eddy current sensor is kept constant so that the accuracy is stable. An object of the present invention is to provide a method and an apparatus for detecting a crack in a welded portion, which can perform an inspection. In addition, even when the magnetic permeability of the material to be inspected is different, even when a complicatedly different material such as a heat affected zone is involved,
It is an object of the present invention to provide a method and apparatus for detecting a crack in a welded portion, which can accurately determine a cracked portion.

[0006]

In order to achieve the above object, a method for detecting a crack in a welded portion according to the present invention samples a signal obtained by scanning an eddy current sensor along a weld bead and samples the sampled data. The peak value is obtained by performing a differentiation process, and the presence or absence of a crack in the weld is detected based on the magnitude of the peak value.

In addition, the present invention provides a weld crack detecting device for an eddy current sensor directed to a weld bead, the sensor having the eddy current sensor attached thereto and having a constant height with respect to the weld bead. A bead copying mechanism capable of following and a flaw detection robot equipped with the bead copying mechanism and movable along a bead line, and a movement signal from the flaw detection robot and a detection signal of the eddy current sensor are input, and the sensor And a calculation unit for outputting a weld crack data from the peak value of the differential data of the sampling data. In this case, the copying mechanism includes a swing arm attached to a robot arm, and a slider having a copying roller that can be extended and contracted along a straight line passing through a rotation support shaft of the swing arm and that rolls along a bead line. And the slider may hold the eddy current sensor.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of a method and apparatus for detecting a crack in a weld according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a weld crack detection device according to an embodiment, and FIG. 2 is a side view and a front view showing a configuration of a sensor copying mechanism attached to the device. As shown in these drawings, the weld crack detection device enables the articulated robot 10 to travel along a weld bead to be inspected. For this purpose, a guide rail 12 that follows the welding bead wire is arranged, and the robot 10 runs on the guide rail 12. The robot 10 has a traveling pedestal 14
The robot controller 1 is configured to perform an arbitrary operation by an articulated robot arm 16 erected on the robot controller 1.
The travel control and the arm operation control are performed in accordance with the command specified by 8.

An eddy current sensor probe 20 is provided at the tip of the articulated arm 16. The sensor copying mechanism 22 holds the tip of the sensor against the weld bead to be inspected while maintaining a constant height from the bead surface. It is possible to follow the unevenness of the line. Specifically, as shown in FIG. 2, a fixing bracket 24 having a T-shaped cross section is attached to the tip of the articulated robot arm 16, and a mounting plate 26 extending forward is fixed to a vertical plate portion of the fixing bracket 24. This mounting plate 2
6, a copying mechanism 22 is attached. It has a swing arm 28 attached to the mounting plate 26 so as to be swingable about a horizontal axis, and a linear bush 30 is attached to a lower side of the swing arm 28. The linear bush 30 includes a shaft slider 32.
Is mounted, and projects downward from the bush in a state where the elastic pressure is applied via the coil spring 34.
A copying roller 36 is attached to the tip of the slider 32 so that it can roll along a welding bead 38. Therefore, when the copying roller 36 is moved along the welding bead 38, the coil spring 34
The shaft slider 32 follows the unevenness of the bead by the action of
Move up and down, and it is possible to absorb unevenness changes.

The shaft slider 32 is a swing arm 2
The movement center line is set so as to be moved up and down along a straight line passing through the eight rotation support shafts 40 (FIG. 2A). Then, the eddy current sensor probe 20 is attached to the slider 32.
Is held, so that the shaft slider 32 and the shaft slider 32 behave together. As shown in FIG. 2B, the eddy current sensor probe 20 is set parallel to the shaft slider 32, and its center line is offset laterally from the shaft slider 32. The control operability is simplified by following a straight line passing through the rotation support shaft 40 of the swing arm 28, but particularly matching the center of the mounting end of the robot arm 16. Further, the sensor surface of the eddy current sensor probe 20 is located slightly above the lower surface of the copying roller 36 so as to maintain a constant height with respect to the welding bead 38. The height (lift-off amount) from the surface of the weld bead 38 to the sensor surface is desirably as small as possible, and desirably 2 mm or less in view of the eddy current detection capability.

The swing arm 28 rotates about a horizontal axis, that is, a rotation support shaft 40. In this embodiment, a damper 42 is provided so that the rotation operation becomes smooth.
Are attached to the rotating shaft 40. As a result, the running line of the copying roller 36 can be made coincident with the toe of the weld bead 38.

The flaw detector having the above-described structure is further provided with a calculation means for determining the presence or absence of a crack based on data detected by the eddy current sensor probe 20. This samples the signal obtained by scanning the eddy current sensor probe 20 along the weld bead 38,
The peak value is obtained by differentiating the sampling data, and the peak value is compared with the set threshold value to detect the presence or absence of a crack in the weld.

That is, as shown in FIG. 1, the eddy current sensor probe 2 is
A data detection unit 46 is provided which inputs a scanning position signal of 0 as a trigger signal and inputs a detection voltage from the eddy current sensor probe 20 via an eddy current sensor amplifier 44. The data detection unit 46 performs A / D conversion of the collected data on the scanning position signal and the detection voltage, and outputs the data to the crack determination calculation unit 48. The crack determination calculating means 48 includes a smoothing processing unit 50, a differentiation processing unit 52, and a pulse search processing unit 54,
Each of them removes noise from the input data, then converts the data into data corresponding to the steepness of the gradient change of the detected voltage, matches this with the scanning position data, and arranges and outputs differential processing values of the data. In eddy current testing,
If the magnetic permeability differs depending on the target material, such as a weld metal, a heat-affected zone, or a base material, the detected voltage differs for each material. In particular, in a part where three types of materials are intricately complicated, such as monitoring of a heat-affected zone, a crack cannot be determined only by the peak value of the detection voltage of the crack. For this reason, in the embodiment, a steep part of the waveform of the detected voltage is found, and the differential processing of the detected waveform is performed, thereby making it unnecessary to set a threshold value for each material having different magnetic permeability. . As for the processing result, the number and position of the detected cracks may be displayed in a table and a graph, and may be output to the monitor 56 and displayed.

In the weld crack detection device having such a configuration, the eddy current sensor probe 20 attached to the arm 16 of the articulated robot 10 is scanned by the robot controller 18 along the welding bead 38 and input to the robot 10. The copying mechanism 22 calculates the error between the sensor position and the target welding position.
And the flaw detection data is input to the data detection unit 46. The analog voltage signal output from the eddy current sensor probe 20 is sent to the data detection unit 46, where it is subjected to A / D conversion, converted into a digital signal, and stored. The collected data is sent to the crack determination calculating means 48, where a smoothing process and a differentiation process are performed. The differential processing value indicates the magnitude of the gradient of the waveform. Even if the magnetic permeability differs for each material, the data is independent of the magnetic permeability, so that the crack can be determined even in the heat-affected zone.

The copying mechanism 22 can ensure that the sensor probe 20 mechanically follows the unevenness of the welding bead 38, and the copying roller 36, which is a contact at the tip, detects a flaw by the coil spring 34. Irregularities can be absorbed and noise caused by chatter due to irregularities of the weld bead can be prevented. The eddy current sensor probe 20 absorbs the bead irregularities together with the copying roller 36, so that the lift-off amount can be kept constant, and the swing arm 28 swings in accordance with the movement of the copying roller 36. Can be accurately traced.

FIG. 3 is an explanatory view of an experiment using the flaw detector according to the embodiment, and FIG. 4 shows a result of data processing. The artificial cracks L2, L3,
L5 and H2 were applied. The size of this artificial defect is as shown in the following table.

[Table 1]

The sensor probe 20 is caused to scan by moving the robot along the toe of the weld bead 38 of the test piece 58 having the artificial crack formed as described above, and the detection signal from the sensor probe 20 is detected. Each time a flaw detection start trigger signal input from the robot controller 18 is received, the data is captured, detection data is input, data sampling, smoothing processing, differentiation processing, and pulse search processing are performed. The horizontal axis indicates the flaw detection position, and the vertical axis indicates the detection voltage. Is displayed as a result. This is shown in FIG. In FIG. 4, the determined crack locations are indicated by ▼. According to this, the position of any artificial defect, that is, a crack parallel to a weld line having a fillet weld length of 10 mm and a depth of 2, 3, or 5 mm, or a crack perpendicular to a weld line having a depth of 2 mm, is determined to be a crack. are doing.

As described above, according to the method and apparatus for detecting a crack in a weld portion according to the embodiment, it is possible to detect a surface crack at a toe portion of a fillet weld portion or a butt weld portion, which is likely to cause a crack, At this time, the data processing is performed so that the influence of the magnetic permeability does not appear on the flaw detection of the welding member portion having different magnetic permeability, so that the eddy current flaw detection can be performed while avoiding the influence of the base material and the like. Also, in order for the sensor copying mechanism 20 to correct and correct the error between the position input to the articulated robot and the actual welding position, a constant height is always accurately set at the welding toe during scanning of the eddy current sensor probe. Can be opposed at an inclination angle,
Detection accuracy can be improved.

[0019]

As described above, according to the present invention, an eddy current sensor directed to a welding bead, and the sensor is attached to follow the unevenness of the bead wire while maintaining a constant height with respect to the welding bead. A possible bead copying mechanism and a flaw detection robot equipped with the bead copying mechanism and movable along a bead line are provided, and a movement signal by the flaw detection robot and a detection signal of the eddy current sensor are input, and the Stable accuracy by maintaining the relative position between the toe of the bead and the eddy current sensor by means comprising a differential processing unit for sampling data and an arithmetic unit for outputting weld crack data from its peak value. Inspection can be performed, and even if the materials to be inspected have different magnetic permeability, complicated materials such as heat-affected zone are complicated. Even if they are, the effect that can be accurately determined cracking unit can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a welding crack detection device according to an embodiment.

FIG. 2 is a side view and a front view showing a configuration of a sensor copying mechanism attached to the apparatus.

FIG. 3 is an explanatory diagram of an artificial defect applied to a weld bead to be inspected and a measurement state.

FIG. 4 is a graph showing a data processing result of an inspection result.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Articulated robot 12 Guide rail 14 Travel base 16 Articulated robot arm 18 Robot controller 20 Eddy current sensor probe 22 Sensor copying mechanism 24 Fixed bracket 26 Mounting plate 28 Swing arm 30 Linear bush 32 Shaft slider 34 Coil spring 36 Copying roller 38 Welding Bead 40 Rotating support shaft 42 Damper 44 Eddy current sensor amplifier 46 Data detection unit 48 Crack judgment calculation means 50 Smoothing processing unit 52 Differentiation processing unit 54 Pulse search processing unit 56 Monitor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G053 AA11 AB07 AB21 BA21 BA30 BB01 BB05 BC02 BC14 CA03 CB13 CB21 DA01 DB14 DB20 DB23 DB25 DB26

Claims (3)

[Claims] A signal obtained by scanning an eddy current sensor along a weld bead is sampled, a differential value of the sampled data is obtained, a peak value is obtained, and the presence or absence of a crack in a weld is determined based on the magnitude of the peak value. A flaw detection method for a welded part, characterized by detecting a crack. 2. An eddy current sensor directed to a welding bead, a bead scanning mechanism to which the sensor is attached and which can follow irregularities of a bead line while maintaining a constant height with respect to the welding bead, and the bead scanning. A flaw detection robot having a mechanism and movable along a bead line is provided, and a movement signal by the flaw detection robot and a detection signal of the eddy current sensor are input, and a differential processing unit of sampling data by the sensor is formed. A welding unit for outputting crack data of the weld from the peak value. 3. The copying mechanism has a swing arm attached to a robot arm, and a copying roller that can be extended and contracted along a straight line passing through a rotation support shaft of the swing arm and that rolls along a bead line. 3. The flaw detector for welds according to claim 2, further comprising a slider, wherein the slider holds the eddy current sensor.