JP2001264026A - Measuring method of dynamic strain under influence of welding arc light, and measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a measuring instrument, capable of measuring dynamic strain occurring in an object to be welded in the course of welding at desired position, except a molten pool and at a desired time, even under the influence of arc light. SOLUTION: In this method of measuring dynamic strain, a strain measuring point under the influence of arc light is irradiated with a laser beam, and the change and movement of a speckle pattern caused by mutual interference of irregular reflected laser beams are detected on surface of sensors. When the irregularly reflected laser beams are detected on the surface of the sensor, the arc light is shaded by shade tubes, each having a pin hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic strain measuring method and a dynamic strain measuring apparatus. More specifically, the invention of this application is to measure a dynamic strain generated in an object to be welded during welding at a desired place and at a desired time except for a weld pool, even under the influence of arc light. And a measuring device therefor.

[0002]

2. Description of the Related Art In general welding, a heat source for heating is used, and heating and cooling by a welding heat source are often performed locally. Since local heating generates thermal stress and easily causes plastic deformation, plastic strain and residual stress exist in the weld after cooling. Welding deformation and residual stress existing in the welded portion cause welding cracks and brittle fracture, etc., and greatly affect the performance of the product. Therefore, the measurement of the strain generated in the weld is
It is important to improve product reliability. In particular,
Immediately after the welding position during welding or immediately after solidification of the weld metal,
If it becomes possible to detect the strain behavior at that position, it is possible to obtain mechanical information for evaluating weld defects such as hot cracks and for estimating residual stress, and improve product reliability. Can be contributed to.

However, conventionally, it has been impossible to measure strain in situ under the influence of arc light such as welding. For this reason, various measures have been taken, such as measuring the strain generated on the back side of the workpiece not affected by the welding arc light by a non-contact high-temperature strain measurement method using a laser.

Therefore, the invention of this application has been made in view of the circumstances described above, and solves the problems of the prior art to reduce the dynamic strain generated in the workpiece during welding.
It is an object of the present invention to provide a method capable of performing measurement at a desired place except a molten pool and at a desired time even under the influence of arc light.

[0005]

Accordingly, the invention of this application provides the following invention to solve the above problems.

That is, first of all, the invention of this application irradiates a laser to a strain measuring point under the influence of welding arc light, and changes and moves a speckle pattern caused by mutual interference of irregularly reflected lasers. A dynamic strain measurement method that detects arc on a sensor surface, wherein the arc light is shielded by a pinhole and a light shielding tube, and irregularly reflected laser is detected on the sensor surface. I do.

Secondly, the invention of the present application provides a dynamic strain measuring method according to the first aspect, further comprising cutting a wavelength component different from that of the laser of the arc light with a band-pass filter. provide.

Thirdly, the invention of this application is characterized in that, in the above second invention, the intensity of the laser is increased to increase the intensity ratio with respect to the arc light. The present invention also provides a dynamic strain measurement method characterized by reducing the amount of light.

On the other hand, fifthly, the invention of this application is a dynamic strain measuring apparatus, which comprises a laser source for irradiating a laser to a strain measuring point, a detecting unit for detecting a laser that has been irregularly reflected, and a detected signal. A dynamic strain measuring device, comprising: a light-shielding cylinder; and two pinholes and a sensor provided sequentially inside the light-shielding cylinder.

Sixth, the invention of this application is characterized in that, in the fifth invention, a band-pass filter is provided in the detecting section, and seventh, an ND filter is provided in the detecting section. A dynamic strain measuring device is provided.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The invention of this application has the features as described above, and embodiments thereof will be described below.

First, a dynamic strain measuring method provided by the first invention of this application irradiates a laser to a strain measuring point under the influence of welding arc light, and generates speckle caused by mutual interference of irregularly reflected lasers. A dynamic strain measuring method for detecting a change and movement of a pattern on a sensor surface, wherein the arc light is shielded by a pinhole and a light shielding tube, and irregularly reflected laser is detected on the sensor surface.

The speckle pattern is formed by interference of light scattered from the rough surface when the roughness of the rough surface is several wavelengths or more larger than the wavelength of the irradiation light. The laser is
Irradiation is performed to obtain information from the strain measurement point. For example, coherent light such as an Ar ion laser can be used.

[0014] Such a speckle pattern is generated on a sensor, continuously detected by the sensor, and subjected to electronic processing. Thereby, the change and movement of the speckle can be obtained as the amount of change of the strain at the measurement point. The electronic processing of the signal is represented by, for example, converting data detected as laser light intensity or the like into a distortion change curve at a measurement point. As the sensor, for example, an electric linear image sensor such as a CCD camera or a vidicon camera can be used. By being able to continuously detect a planar image or a linear image, a strain result can be obtained in real time, and a strain behavior and a strain amount at a desired time can be obtained.

What is important in the method of the present invention is that even under the influence of welding arc light, which is extremely intense, the influence is eliminated and the above-described laser light can be detected.

That is, as a method, when the welding arc is at a position distant from the strain measurement point, the arc light is shielded by using a pinhole and a light shielding cylinder.

FIG. 1 is a side view showing an outline of strain measurement when a welding arc is located at a position distant from a strain measurement point. The light-shielding cylinders (16, 26) are installed so that the center line is on the radiation from the strain measurement point (5), that is, the laser (3) reflection point. In the figure, two pinholes (11, 12, 21, 22), band-pass filters (13, 23), and an ND filter (14) are sequentially arranged in the light-shielding tubes (16, 26) from the laser (3) reflection point side. , 24) and sensors (15, 25).

The pinholes (11, 12, 21, 2)
2) is open at the center of the cross section of the light-shielding tube (16, 26), and the first pinholes (11, 21) and the second pinholes (12, 22) are installed with an interval. ing.
Therefore, only the light that has entered the first pinhole (11, 21) perpendicularly to the cross section of the light-shielding cylinder (16, 26) can pass through the second pinhole (12, 22).

For example, a laser (3) emitted from a laser source (2) is applied to a strain measurement point (5) via a mirror (4) and the like. Part of the laser (17, 27) diffusely reflected at the strain measurement point (5) is
6) Two pinholes in (11, 12, 21, 22)
Can pass through. Arc light (18,) emitted from an arc (7) away from one strain measurement point (5)
28) cannot be perpendicularly incident on the cross-section of the light-shielding cylinder (16, 26), so that two pinholes (11, 12, 21, 2)
2) and the light shielding cylinders (16, 26) completely shut off the light. That is, the arc light (18, 28) is applied to the sensor (1).
5, 25) cannot be reached.

The fact that the welding arc (7) is located away from the strain measurement point (5) means that the arc light (18, 28) emitted from the welding arc (7) can be understood from the above description. Are two pinholes (11, 12, 2
1, 22).

Thus, when the welding arc is at a position distant from the strain measurement point, the strain can be measured without being affected by the arc light at all.

The dynamic strain measurement method provided by the second invention of this application is characterized in that, in the first invention, a wavelength component different from that of the laser of the arc light is further cut by a band-pass filter.

When the welding arc is located near the strain measurement point, that is, when the arc light emitted from the welding arc passes through two pinholes,
Further, an arc light having a wavelength other than the wavelength of the laser is cut by a bandpass filter. FIG. 2 is a side view showing an outline of strain measurement when the welding arc is located near the strain measurement point.

When the arc (7) is directly above and around the strain measuring point (5), the arc light (18, 28) takes almost the same optical path as the diffusely reflected laser (17, 27).
Then, a part of the arc light (18, 28) and the laser (18, 28) irregularly reflected enter the section of the light-shielding cylinder (16, 26) almost perpendicularly, and the pinhole (11, 12, 21, 2)
2) and the light shielding tube (16, 26).

However, the arc light (1) is applied by the band-pass filters (13, 23) set in the light shielding tubes (16, 26) and adapted to the wavelength of the laser (3).
Wavelength components outside the same wavelength band as the laser (3) of (8, 28) are cut. That is, the pinholes (11, 1
All of the lasers (17, 27) diffusely reflected among the light passing through (2, 21, 22) are sensors (15, 25).
Although reaching the surface, most of the arc light (18, 28) is blocked and does not reach the sensor (15, 25) surface.

Also, even if a minute arc light enters the sensor, it is simply added to the speckle waveform. If the light intensity distribution due to the arc light is flat on the arrangement of the sensor elements, the speckle waveform becomes Distortion can be calculated by assuming that there is no effect on the measurement itself because it is only base-up.

Thus, even when the welding arc is located near the strain measurement point, the strain can be measured without being affected by the arc light.

In the dynamic strain measuring method provided by the third invention of this application, in the second invention, the intensity of the laser is increased to increase the intensity ratio with respect to the arc light.

Since the arc light includes light covering almost the entire wavelength range, light having the same or a similar wavelength as the laser used exists. The arc light component having the same or near wavelength as that of the laser passes through a band-pass filter corresponding to the laser wavelength. When a large amount of the arc light that passes through the band-pass filter is large, it is desirable to increase the laser intensity. Thereby, the intensity ratio between the laser and the arc light can be increased.

In other words, this makes it possible to perform strain measurement with a good S / N ratio even when the welding arc is located near the strain measurement point.

The dynamic strain measuring method provided by the fourth invention of the present application is the method according to the second or third invention, wherein
The total light amount is reduced by the D filter.

When the intensity ratio of the laser and the arc light is increased by increasing the intensity of the laser, it is conceivable that the light amount is saturated in each element in the sensor. In such a case, as shown in FIG. 2, an ND filter (14,
By using the method 24), the entire light amount can be reduced while maintaining the S / N ratio.

As described above, the dynamic strain during welding can be measured at a desired location except for the molten pool and at a desired time even under the influence of arc light.

The dynamic strain measuring apparatus provided by the fifth, sixth and seventh inventions of the present application realizes the measuring method of the above invention, and includes a laser source for irradiating a laser to a strain measuring point. It comprises a detector for detecting the irregularly reflected laser and a means for processing the detected signal. The detector comprises a light-shielding cylinder and two pinholes and a sensor provided therein sequentially, and further includes a band-pass filter and an ND filter. It is characterized by having. Of course, other than this, a mirror or the like for controlling the direction of the laser may be provided.

As the laser source, the sensor, and the processing means of the detection signal, generally known ones can be used as long as they can continuously detect and process the reflected light speckle of the laser oscillated from the laser source. can do.

The type of laser is not particularly limited. For example, when the laser is applied to welding or the like, it is desirable to avoid using red light in order to avoid overlap with a red heat region. In addition, use of a visible light laser to simplify measurement position alignment is exemplified.

It is sufficient that the sensor can be driven at about 1 to 2 MHz in consideration of the capability of the data recording device. For example, if the number of elements is 1000 to 300
About 0 linear image sensors are exemplified.

The pinhole and the light-shielding cylinder can be appropriately set and selected from commonly known ones according to the laser and the sensor to be used. For example, the hole diameter of the pinhole can be determined by the laser spot diameter on the object to be measured, the distance from the measurement point to the sensor, the number of sensor elements, and the pitch thereof. Examples of the light-shielding cylinder also include a light-shielding cylinder coated with a non-reflective paint or an anodized aluminum.

There is no particular limitation on the bandpass filter, but in order to reduce the transmission of arc light as much as possible, it is exemplified to use a bandpass filter having a half width as narrow as possible in accordance with the wavelength of the laser to be used.

Although there is no particular limitation on the ND filter, for example, use of a combination of a plurality of filters is shown. Specifically, the use of an ND filter having a transmittance of 5% by stacking ND filters having a transmittance of 50% and 10% is exemplified.

What is important in the apparatus according to the present invention is the structure of the detection unit. FIG. 2 illustrates a schematic side view of a strain measuring device according to the present invention. The detection unit includes a light shielding tube (16,
26) and sensors (15, 25), between which, in order from the light incident side, two pinholes (11, 12, 21, 22) in the measuring device of the fifth invention.
However, the measuring device of the sixth invention further includes a band-pass filter (13, 23), and the measuring device of the seventh invention further includes an ND filter (14, 24).

Pinholes (11, 12, 21, 22)
Is located at the center of the cross section of the light-shielding cylinder (16, 26), and the two are arranged at an interval, so that the first pinhole (1
Only light vertically incident on (1, 12) can pass through the second pinholes (21, 22).

The band pass filters (13, 23)
In order to transmit only light in the same wavelength band as the laser (3) to be used, pass light having a different wavelength from the laser (3) to be used even if the light has passed through the second pinholes (21, 22). There is no.

The ND filters (14, 24) are S / N
The amount of light increased to increase the ratio can be reduced while maintaining the light intensity ratio.

The light shielding tubes (16, 26) are provided with band-pass filters (13, 23) and ND filters (1).
4, 24) can be attached and detached, and one selected according to the laser to be used, various conditions, and the like can be installed before measurement. Although not shown in the figure, a sufficient number of mounts can be provided so that a plurality of ND filters (14, 24) can be attached and detached. Unnecessary filters (13, 14, 23, 24) need not be attached. In this case, of course, light is prevented from entering from the filter mounting portion so that the function of the light shielding tube can be maintained.

In the apparatus according to the invention of the present application, a plurality of detectors can be installed in order to two-dimensionally measure the strain generated on the surface of the test piece. For example, it is possible to install a plurality of detectors on four sides of the strain measurement point and to perform strain measurement in two directions, that is, the direction in which the welding arc moves and the direction perpendicular thereto.

Further, since strain measurement can be performed without contact,
The laser source and the detection unit can be installed at a position away from the strain measurement point within a range where the laser reaches. For example, strain measurement can be performed without hindering movement of a device such as a torch.

As a result, a strain measuring device capable of measuring the dynamic strain during the welding process at a desired location except a molten pool and at a desired time even under the influence of arc light is realized.

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

[0050]

EXAMPLE (Example 1) 60 × 120 × as a test piece
Using a 3.8 mm SUS304 stainless steel plate, the center of the rectangular plate was heated with GTA (gas tungsten arc) over 60 mm, and the generated strain was continuously measured. FIG. 3 is a plan view showing the outline of the strain measurement.

The strain measurement point was at the center of the heating wire, and an Ar ion laser having a wavelength of 514.5 nm was used as a measurement laser. Detection of the laser reflected light was continuously performed at two points X and X '. GTA moved in the Y direction at the start of heating, and the moving speed was 240 mm / min. The arc current was set in two ways, (1) 100A and (2) 200A. (Example 2) The strain measurement point was set at a point 5 mm perpendicular to the center on the heating line of the test piece, and detection of laser reflected light was performed at four points X, X ', Y, and Y' in FIG. Was. The moving speed of the GTA was 120 mm / min, and the arc current was 70 A. Otherwise, the dynamic strain was measured in the same manner as in Example 1. (Example 3) The strain measurement point was a point 8.5 mm away from the center on the heating line of the test piece at right angles. Otherwise, the dynamic strain was measured under the same conditions as in Example 2.

FIG. 4 shows an example of the result of calculating the strain behavior of the test piece of Example 1 generated in the X direction at the measurement point from the start of heating.

The arc starts to move at the same time as the ignition, and 7.5
The measurement point was reached in seconds (indicated by the dotted line in the figure). The distortion for several seconds before and after this is zero because the GTA torch blocked the reflected light of the laser and the measurement could not be performed. Thereafter, it was observed that the strain gradually increased.

The arc currents were (1) 100 A and (2) 20
It was confirmed that a difference in strain behavior when changing to 0A can be observed.

Since the movement of the GTA torch is set in the Y direction by setting the strain measurement point on the heating line, the laser reflected light in the Y direction is always blocked by the GTA torch.
No strain measurement in the Y direction was performed.

FIGS. 5 and 6 show one example of the results of calculating the strain behavior of the test pieces of Examples 2 and 3 generated at the measurement points from the start of heating.

In both Examples 2 and 3, in the strain measurement in the X direction, measurement could not be performed for only a few seconds when the GTA torch blocked the reflected light of the laser. It was confirmed that the strain measurement in the Y direction was continuously performed without interruption. Of course, before passing through the heat source (GTA torch) and
The strain behavior immediately after the measurement location solidified after passing was also observed.

From the above, it was confirmed that the dynamic strain measurement under the influence of arc light can be performed by the dynamic strain measurement method of the present invention. It was also confirmed that when various conditions were changed, it was possible to observe distortion at desired locations and at desired times. (Example 4) The strain on the back side of the heated portion of the test piece without the influence of the arc light was measured in the same manner as in Example 1, and the waveform of the speckle detected by the linear image sensor was displayed at predetermined intervals for several thousand screens. The original waveform was recorded. FIG. 7 shows an example of the original waveform, the processed waveform, and the calculated distortion change curve.

FIG. 7A shows an example of one of the recorded original waveforms. 2 lined up on a linear image sensor
The light intensity: An detected by the middle 1000 elements of the 048 elements is shown.

(B) and (c) are examples in which the light intensity: An is doubled: Bn and quadrupled: Cn, respectively. When strain measurement is actually performed with the laser intensity doubled and quadrupled, the same waveform is obtained.

(D) shows the light intensity: D obtained by detecting virtual arc light with 1000 elements in the same manner as described above.

Then, (A) shows that among the recorded original waveforms, 7
The strain change curves calculated using 20 screens (A1 to A720) are shown.

(A) 'shows the original waveform 720 screen (A1 to A
720), the middle 320 (A201 to A52)
0) shows a strain change curve calculated by uniformly adding the arc light intensity: D. That is, it shows the calculation result of the strain change curve when the influence of the arc light is applied during the strain measurement.

(B) ′ shows the original waveform 7 with the light intensity doubled.
Of the 20 screens (B1 to B720), the strain change curve calculated by uniformly adding the arc light intensity: D is shown on the middle 320 (B201 to B520). In other words, it shows the result of calculating the change in strain when the laser beam is affected by the arc light during the strain measurement performed by doubling the laser intensity.

Similarly, (C) ′ of the original waveform 720 screen (C1 to C720) whose light intensity has been quadrupled has a middle 32
A strain change curve calculated by uniformly adding the arc light intensity: D to zero sheets (C201 to C520) is shown. That is,
It shows the result of calculating the change in strain when the laser beam is affected by the arc light during the strain measurement performed by quadrupling the laser intensity.

Comparing (A) and (A) ′ to (C) ′, it is understood that the strain change curve of (A) approaches from (A) ′ to (C) ′. This indicates that even if there is an effect of arc light, increasing the laser intensity does not affect the result of calculating the strain change curve.

Thus, it was shown that by increasing the laser intensity in the method of the present invention, the influence of arc light on dynamic strain measurement can be suppressed.

Of course, the present invention is not limited to the above-described example, and it goes without saying that various embodiments are possible in detail.

[0069]

As described above in detail, according to the present invention, even when under the influence of arc light, a dynamic strain generated in a workpiece during welding can be obtained at a desired position except a molten pool and at a desired position. It can be measured at the time.

[Brief description of the drawings]

FIG. 1 is a side view showing an outline of strain measurement when a welding arc is located at a position distant from a strain measurement point.

FIG. 2 is a side view showing an outline of strain measurement when a welding arc is located near a strain measurement point.

FIG. 3 is a plan view schematically illustrating strain measurement by the method of the present invention.

FIG. 4 is a diagram showing an example of a strain change curve generated in a X direction at a measurement point.

FIG. 5 is a diagram showing an example of a strain change curve generated in the X and Y directions at a measurement point.

FIG. 6 is a diagram showing an example of a strain change curve generated in the X and Y directions at a measurement point.

FIG. 7 is a diagram showing an example of an original waveform detected by the measurement method of the present invention, a processed waveform, and a calculated distortion change curve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Workpiece 2 Laser source 3 Laser 4 Mirror 5 Strain measuring point 6 Torch 7 Arc 8 Data logger 9 Computer 10 Strain change 11, 12, 21, 22 Pinhole 13, 23 Bandpass filter 14, 24 ND filter 15, 25 Sensor 16, 26 Light-shielding tube 17, 27 Diffusely reflected laser 18, 28 Arc light

Claims (7)

[Claims] A dynamic strain measuring method for irradiating a laser to a strain measuring point under the influence of a welding arc light and detecting a change and movement of a speckle pattern caused by mutual interference of irregularly reflected lasers on a sensor surface. And
A method for measuring dynamic strain, characterized in that arc light is shielded by a pinhole and a light-shielding cylinder, and irregularly reflected laser is detected on a sensor surface. 2. The dynamic strain measuring method according to claim 1, further comprising cutting a wavelength component different from that of the laser of the arc light by a band-pass filter. 3. The dynamic strain measuring method according to claim 2, wherein the intensity of the laser is increased to increase the intensity ratio with respect to the arc light. 4. The dynamic strain measuring method according to claim 2, wherein the entire amount of light is reduced by an ND filter. 5. A dynamic strain measuring apparatus, comprising: a laser source for irradiating a laser to a strain measuring point; a detecting unit for detecting a laser beam irregularly reflected; and a means for processing a detected signal, wherein the detecting unit is a light shielding tube. And the two provided inside it
A dynamic strain measuring device having two pinholes and a sensor. 6. The dynamic strain measuring apparatus according to claim 5, wherein the detecting section has a band-pass filter. 7. The dynamic strain measuring apparatus according to claim 5, wherein the detecting section has an ND filter.