JPS61142408A - Weld bead shape measuring apparatus - Google Patents

Abstract

PURPOSE:To judge the acceptance of weld, by analyzing the shape of the section of a weld bead based on data from a detector section which observes a weld bead being irradiated with a laser light to computer the stress concentration coefficient of toe of weld at the section. CONSTITUTION:A laser light is irradiated along a weld beam 11 which a measuring apparatus 13 with a detector section 12 having a camera is provided. In the measuring apparatus 13, a beam 15 is linked between two legs 14 arranged along the direction of the weld beam 11 and the detector 12 thereof is provided along the beam 15 in such a manner as to free to reciprocate with a travelling unit 16. Data for the shape of the section of the weld beam 11 while the detector section 12 is travelling from the start to end point thereof is memorized into a media 19 of a bubble cassette and the shape of the section is analyzed at each weld position with an analysis computing unit 20 from the media 19 to determine the height (h) of the bead, right and left flank angles thetaL and thetaR, radii of toe of weld rhoL and rhoR and width 2hP of the bead. A stress concentration coefficient kt is computed from these values to judge on the acceptance of weld.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device for measuring the shape of a weld bead in a welded part of an independent rectangular tank of a liquefied gas tanker, which requires analysis of fatigue strength. The present invention relates to a weld bead shape measuring device that can determine the quality of welding based on the weld bead shape.

[Prior Art] As shown in Fig. 10, a liquefied gas tanker has an independent rectangular tank 2 in a hull 1, a rolling chock 3 and a support 4.
It is supported with a gap between it and the inner surface of the shell 1, so that when LNG, LPG, etc. are loaded into the independent rectangular tank 2, contraction and movement due to low temperatures can be tolerated. The independent rectangular tank 2 containing the low-temperature liquid has a structure that has sufficient strength against deformation stress during contraction.

This independent rectangular tank 2 is made of aluminum alloy or low-temperature steel. For example, as shown in FIG. It is constructed by welding the seams. Incidentally, this type of liquefied gas tanker belonging to Type B in the IMO Code is required to perform a detailed fatigue strength analysis in accordance with the IMO Code. The definition of this B type tank is that the safety of the tank has been confirmed through accurate analysis and experiments, and it is a link that does not cause major destruction of the tank at once.
Therefore, emphasis is placed on fatigue analysis and fracture analysis. An independent rectangular tank has a bone structure with many welded tank parts inside, and has a high unsteady constant order, so it was difficult to completely analyze it, but recently it has become relatively easy to analyze it with computers. . However, fillet welds and the like are inevitably used frequently in bone structures, and the welded shapes are irregular, so it is necessary to conduct fatigue tests on each welded part individually. This fatigue strength analysis of welded parts is performed based on the nominal stress of the members, and for each type of welded joint,
An S-N curve showing the relationship between stress and the number of times of fatigue and fracture when stress is repeatedly applied is determined through experiments, and based on this, the fatigue strength of the welded joint against nominal stress is determined. However, since the fatigue strength differs depending on the shape of the member, the shape of the joint, or the shape of the weld bead, various S-N curves are required, which requires many tests. In fact, it is impossible to cover all the joints appearing in an independent rectangular tank with the S-N curve determined for each test.

In Japanese Patent Application No. 58-191037, the present applicant has proposed that the stress concentration coefficient at the upper end of the weld can be measured, and the fatigue analysis of the weld can be easily performed based on this stress concentration coefficient [independent of liquefied gas]. proposed a square tank.

In this prior invention, in order to determine the stress concentration factor, it is necessary to measure the bead shape such as the flank angle, toe radius, and bead height of the weld, but currently, the bead shape is measured using a meter. There is no equipment.

Conventionally, to measure the bead shape, a replica of the weld bead was made using modeling compound, cut with a saw at right angles to the weld line, and the cut surface was photographed at a 10x magnification, and this enlarged photograph was used to measure the weld bead using a ruler. , flank angle, toe radius, bead height and leg length were measured.

[Problems to be Solved by the Invention] However, this measuring method requires time for preparatory and post-processing for making copies, and one person can only measure about 30 points in a day. In addition, there are problems such as distortions in the reproduction due to the processing method, which may cause the shape to differ from the actual shape, and individual differences due to measurements taken using enlarged photographs taken with a ruler.

[Object of the Invention] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a weld bead shape measuring device that can measure the shape of a welded part in a short time and can determine whether the welded part is good or bad. shall be.

SUMMARY OF THE INVENTION] In order to achieve the above object, the present invention provides a detection unit that irradiates a weld bead with a laser beam and a camera that observes the same, and a traveling device that moves the detection unit along the weld bead. and an analysis calculation device that analyzes the cross-sectional shape of the weld and the weld using data from the detection unit and calculates the stress concentration coefficient at the upper end of the weld in the cross-sectional shape. The weld bead is irradiated and detected by a camera, and the cross-sectional shape of the weld bead is analyzed to determine the flank angle, toe radius, bead height, leg length, etc. of the weld bead, and the stress concentration factor is calculated. The quality of the weld can be determined based on whether the stress concentration factor is within a standard value.

[Embodiment] A preferred embodiment of the weld bead shape measuring device according to the present invention will be described below with reference to the accompanying drawings.

First, the stress concentration factor Kt will be explained using the cross-welded joint shown in FIG. 8 as an example.

In FIG. 8, it is assumed that 6 is a vertical plate and 7 is a horizontal plate, and a fillet weld 8 is made between the vertical plate 6 and the horizontal plate 7.

In this case, the reinforcement angle (hereinafter referred to as flank angle) of the weld 8 is θ, the bead height is h, the bead toe radius of the upper end 9 of the weld 8 is ρ, and the thickness of the horizontal plate 7 is t.

Assuming that a nominal stress σN is now applied to the horizontal plate 7, the stress distribution remains at the nominal stress σN in the unwelded horizontal plate 7, as shown at 10, but the stress concentration increases as it approaches the upper end 9. The maximum local stress σL is applied at the upper end 9. Therefore, if the stress concentration coefficient at this upper end portion 9 is Kt, )(1 is expressed by the following formula.

In addition, this Kt is the above-mentioned flank angle θ, toe radius ρ,
It is a function of bead height h and is expressed by the following formula.

K, = [1+f(θ+(c3(pner-1))C(a/
〆1) −・---(2) Here, f(θ
) is a function due to the influence of the flank angle, q(ρ) is a function due to the influence of the weld toe radius, and C(a/T) is a function due to the influence of the presence of an unwelded portion, and each is expressed by the following formula.

Flank angle: f (θ) Toe radius: 9 (ρ) OJ (ρ) = αt・9t (ρ) + αb・9b (ρ)
...(4) Here, gt (ρ) is given by the following formula in the case of a tensile load.

Here, βt takes the following value depending on the shape of the welded joint. Cross joint 22, butt joint 2.0°, T joint 1.0° Also, gb (ρ) in the case of bending load is given by the following equation, regardless of the joint shape.

Here, βb takes the following value depending on the shape of the welded joint. Butt joints - 1, 5, T joints 1, 9, other joints = 10
0 Unwelded part; C(a/Tl where (31, (W in formula 51 is used as follows depending on the type of welded joint.

However, (b ~ (in formula 8, θ is the flank angle, ρ is the toe radius,
t is the plate thickness of the member to be added, tp is the plate thickness of the member that does not receive the load, h is the bead height (leg length), hp is the weld leg length, a
is the length of the unwelded part, αt is the tensile stress coefficient at the upper end (for tensile load = 1, for bending load = 0), αb is the bending stress coefficient at the upper end (for bending load = 1, In case of tensile load -〇).

In the above, by determining the stress concentration coefficient Kt,
The local stress σ at the upper end portion 9 can be seen from the above-mentioned intermediate portion. That is, the local stress σL is determined from the following formula.

σL=KL ・σN Therefore, for example, when creating an S-N curve for the case where the nominal stress σN is repeatedly applied to the horizontal plate 7 of the cruciform joint shown in Fig. 8 until it breaks, instead of the nominal stress σ8, If the S-N curve is drawn using the local stress σ, a unified S-N curve can be obtained. This SN curve is shown in FIG. In the figure, the vertical axis indicates the local stress σL at the upper end in the stress range,
The points at which the butt joint, cruciform joint, and T7 joint break when each stress is repeatedly applied are plotted, and the straight line showing the graph shows the probability of survival among the number of test pieces.

Since this SN curve is drawn based on the local stress σL, the fatigue strength of each joint can be easily determined.

Normally, if welding is performed without limit, the stress concentration coefficient Kt will be distributed over a wide range at each position in the direction of the weld bead even in the same welded joint. Therefore, for example, in the case of a Kt value of 70, the local stress σL applied to the upper end is seven times the nominal stress σ, which increases and reduces fatigue strength.

Now, if the nominal stress σ8 in each joint is constant,
The local stress σ at the upper end changes depending on the KL value. Therefore, when welding each weld joint to determine the fatigue strength, it is necessary to determine whether the Kl value is within the standard value in order to prevent the maximum local stress a+aXσL from being exceeded. However, if welding is normally performed without limit, the Kt value will be distributed over a wide range at each position in the direction of the weld bead, even for the same welded joint, and the Kt value may exceed a set reference value.

In order to determine the quality of welding of a welded joint in this way, it is necessary to measure all Kt values along the bead welding direction of the welded joint, and to do so, the cross-sectional shape along the bead welding direction must be measured It is necessary to measure it.

Next, the bead weld shape measuring device of the present invention will be explained with reference to FIGS. 1 to 7.

In FIGS. 1 to 3, reference numeral 11 indicates a weld bead in butt welding, which indicates a portion where the tank member 5 of an independent rectangular tank is butt welded as explained in FIG. 11.

A measuring device 13 is provided along the weld bead 11, and includes a detection unit 12 that irradiates the weld bead with a laser beam and has a camera that observes the laser beam. Measuring device 13
A beam 15 is connected between two legs 14 extending in the direction of the weld bead 11, and a detection section 12 is provided along the beam 15 so as to be movable back and forth by a traveling device 16. The detection unit 12 uses a camera 12b to observe the optical cutting wave formed on the surface of the weld bead 11 by the thin laser beam from the light projecting unit 12a from an oblique direction, and shows the outline of the irradiated part of the weld bead 11. The image is formed on the position sensor, and the image signal is sent to the memory device 17 together with the traveling position signal of the traveling device 16 and stored therein. Further, the moving speed of the detection section 12 by the traveling device 16 and the laser power of the light projecting section 12a are controlled by the drive control device 18.

When the detection unit 12 travels from its starting point to its ending point,
Data on the cross-sectional shape of the weld bead 11 during that time is stored in the media 19 of the bubble cassette, and the media 19 is analyzed by the analysis calculation device 20 for the cross-sectional shape at each welding position. Bead height h1
Left and right flank angle θ5. The θc1 toe radii ρL, ρR, and the peed width 2hP are determined, and the Kt value is calculated from these values to determine the quality of welding.

This will be explained in more detail with reference to FIG.

The detection unit 12 has a light projection unit 12a that irradiates a welding beam, which is an object to be detected, with a laser beam, and observes the light cutting wave formed on the target with a camera 12b, and records it on the video of the memory device 17. The signal is input to the signal processing section 21. The adjustment of the laser beam of the light projector 12a and the output of the camera 12b are adjusted by each adjusting device @22, 23 of the drive control device 18, and the motor 24 of the traveling device 16 is also drive-controlled by the driver 25 of the drive control device 18. Ru. Further, the starting point position @16a, ending point position 16b, and position signals from the traveling device 16 are input and output to the control interface (1/F) section 26 of the memory device @17.

The memory device 17 has a panel operation section 27, and a panel I/F section 28. The traveling device 16 via the control I/F section 26
The speed of the weld bead can be controlled, and the signal of the weld bead cross-sectional shape and the position signal of the cross-section entered into the video signal processing section 21 are sent via the bubble I/F section 30 as appropriate according to instructions from the central processing unit 29. bubble cassette holder 31
is memorized. The medium 19 stored in this bubble cassette holder 31 is input to the analysis calculation unit f120.

The analysis/arithmetic unit @20 displays the cross-sectional shape of FIG. 5 at each memorized weld bead position on a CR7 display 32 for each position, and calculates the flank angle θ from the image.

The bead height, toe radius ρ, etc. are read by a reading device 33, and each read value is sent to a Kt value calculating device 34. The Kv value calculation device 34 calculates the above-mentioned Kt value (b~(8)
A formula is input, and the flank angle θ, bead height, and toe radius ρ are substituted into the formula to calculate the Kt value, which is output to the weld quality determination device 35. The weld quality determination device 35 determines whether the Kt value at each part of the weld bead is within a predetermined standard value (for example, the Kt value is 3.0 or less), and determines in which position of the weld bead 11 the weld is poor. Display. Further, each data from the reading device 33 and data from the discriminating device 35 are sent to a printer 36, and the printer 36 records each data.

Therefore, as shown in FIGS. 1 and 3, when looking at the hard copy 37 printed out by the printer 36,
The welding condition can be determined, and if there is an inappropriate welding point in the measured weld bead, the weld bead 11
Repair as appropriate.

The above explanation was based on determining the quality of the weld bead after welding, but it is also possible to measure the bead immediately after welding with the detection unit 12 at the same time as welding, calculate the KL value, and control the welding appropriately based on that value. It may be configured as follows.

Furthermore, in the example shown in Figs. 1 to 4, the cross-sectional shape of the weld bead 11 is analyzed at once using an optical cutting wave, but in the example shown in Figs.
As shown in the figure, the detection unit 12 is moved to cross the weld bead 11, sequentially scanned with a width H larger than the bead width as shown by arrow A, the distance at the scanning position is measured with a camera, and the value is The cross-sectional shape may also be measured.

In this case, as shown in FIG.
The beam irradiated onto the bead 11 passes through the image lens 38 and the half mirror 39 to the camera 12 consisting of a position sensor 40 and a photosensor 41.
b, and the cross-sectional shape can be analyzed from the change in distance when scanning from ■ to ■ as shown in FIG. In this case, since the scanning interval d can be directly read from the cross-sectional shape, the flank angle θ, toe radius ρ, etc. can be determined from the data, and the Kt value for each interval d can be calculated.

[Effects of the Invention] As is clear from the detailed description above, the present invention exhibits the following excellent effects.

(1) It is possible to measure the weld bead non-contact with a laser, analyze the measured cross-sectional shape, and calculate the stress concentration coefficient from the shape to determine whether the weld is good or bad.

(2) The cross-sectional shape data obtained by the laser can be stored in media and analyzed at a later time.

(3) Bead measurements can be performed automatically at each interval, the intervals can be made variable, and the measurement time can be extremely short.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the weld bead shape measuring device of the present invention, FIG. 2 is a perspective view showing a measuring section of the weld bead shape measuring device of the present invention, and FIG. 3 is a weld bead shape measuring device of the present invention. FIG. 4 is a circuit diagram of the weld bead shape measuring device of the present invention, FIG. 5 is a diagram showing the shape of the weld bead in the present invention, and FIG. 6 is a diagram showing the weld bead shape of the present invention. An explanatory diagram showing another example of measuring by irradiating a laser in a weld bead shape measuring device, FIG. 7 is a detailed diagram of the detection part used in FIG. 6, and FIG. 8 is a diagram explaining the stress concentration coefficient in a cross joint. , FIG. 9 is a diagram showing an S-N curve, FIG. 10 is a sectional view showing an independent rectangular tank, and FIG. 11 is a perspective view showing details of the tank shown in FIG. 9. In the figure, 11 is a welding bead, 12 is a detection section, 12a is a light projecting section, 12b is a camera, 16 is a traveling device, and 20 is an analysis calculation device. Patent applicant: Ishikawajima Harima Heavy Industries Co., Ltd. Representative Patent Attorney Nobuo Kinutani Figure 2 Figure 3 Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] A detection unit that irradiates a weld bead with a laser beam and a camera that observes it; a traveling device that moves the detection unit along the weld bead; and a cross-sectional shape of the weld bead based on data from the detection unit. A weld bead shape measuring device comprising: an analysis calculation device that analyzes and calculates a stress concentration coefficient at the upper end of the weld in the cross-sectional shape of the weld bead.