JP6874781B2 - Laser peening device - Google Patents

Description

The present invention relates to a laser peening device that reduces residual tensile stress on the surface of steel structures and metal machine parts or converts it into compressive stress, and is particularly suitable for on-site laser peening construction such as a steel bridge repair site. Regarding the optimum laser peening device.

In steel structures and metal machine parts, metal fatigue occurs due to repeatedly applied stress or repeatedly applied heat, and therefore there has been concern about damage accidents due to metal fatigue. In recent years, attempts have been made to use steel structures and metal machine parts for a long period of time, and there are concerns about damage accidents due to metal fatigue. In particular, in the vicinity of the welded portion of the steel structure, tensile stress remains due to welding heat input, and there is a risk of potential cracking.

Under such circumstances, various techniques for improving the surface of metal materials are being developed as preventive maintenance measures for metal materials. As part of this, measures to prevent breakage accidents by actively changing the residual stress on the surface of metal materials from tensile stress to compressive stress are being studied, and methods such as shot peening, hammer peening, and laser peening have been developed. Has been done. Among them, the laser peening technology has been attracting attention in recent years because it has an excellent effect on high-strength steel materials.

As described in Patent Document 1, for example, the laser peening technique irradiates a surface of a metal material covered with a liquid with pulsed laser light, and irradiates the surface of the metal material with pulsed laser light to generate high-pressure plasma. It is a technique in which the surface of a metal material is hit with a laser, and the strong shock wave generated at that time propagates inside the metal material to cause plastic deformation, and the tensile residual stress of the metal material is reduced or converted into compressive stress. This is because the circumference of the plasma is covered with liquid, so the expansion of the plasma is hindered, the internal pressure of the generated plasma reaches about several GPa, and this plasma hits the surface of the metal material, and at that time, it is powerful. This is a technology that utilizes the phenomenon that shock waves are induced.

Japanese Unexamined Patent Publication No. 2008-49637

Laser peening technology makes it possible to efficiently apply compressive residual stress to steel structures and metal machine parts, and extends the life of steel structures and metal machine parts.

By the way, the irradiation range of the laser beam of the laser peening device is ^{a very small area of less than 1 mm 2} , and in order to improve the fatigue strength of steel structures and metal machine parts, the range is at least about 50 mm × 20 mm. Irradiation is necessary, and it is necessary to accurately determine the irradiation position of the laser beam and move the laser beam quickly and accurately.

In addition, steel structures that require improved fatigue strength are steel bridges, etc., and it is necessary to quickly and accurately irradiate a plurality of predetermined positions of the steel structure with laser light at a site such as a steel bridge repair site. .. Furthermore, since the local conditions and the shape of the target steel material vary, it is even more indispensable to accurately control the irradiation position of the laser beam.

When Patent Document 1 is verified from this viewpoint, Patent Document 1 does not consider transporting the laser peening device to various places and performing laser peening on various steel structures. That is, it can be said that it is impossible for the laser peening device disclosed in Patent Document 1 to quickly and accurately irradiate a plurality of predetermined positions of a steel structure at a site such as a repair site of a steel bridge.

The present invention has been made in view of the above circumstances, and an object of the present invention is that it can be easily transported to various places and installed, and the laser beam can be accurately delivered to a plurality of predetermined positions of a steel structure. It is to provide a laser peening apparatus capable of irradiating well and quickly.

The gist of the present invention for solving the above problems is as follows.
[1] A laser transmitter, a laser irradiation head that irradiates the surface of a metal material to be irradiated with pulsed laser light emitted from the laser transmitter, and a laser transmission cable that connects the laser transmitter and the laser irradiation head. A liquid injection nozzle for injecting a liquid for keeping the surface of the metal material to be irradiated in an atmosphere wet with the liquid, a liquid supply unit for supplying the liquid to the liquid injection nozzle, the liquid injection nozzle and the liquid supply unit. A tube for supplying liquid, a position measuring device for measuring the irradiation position of the pulsed laser beam on the irradiated metal material, an articulated robot arm to which the laser irradiation head is attached, and the position measuring device. It has an operation control device that inputs information on the irradiation position of the pulsed laser beam on the irradiated metal material and controls the operation of the articulated robot arm based on the input information on the irradiation position. A laser peening device, the motion control device controls the motion of the articulated robot arm so that the pulsed laser beam irradiates the entire region of the laser peening set in advance in the motion control device. A laser peening device characterized by being configured in.
[2] The laser peening device according to the above [1], wherein the liquid injection nozzle and the position measuring device are attached to the articulated robot arm.
[3] The articulated robot arm has a fixed structure portion made of any one of a clamp, a magnetic, a suction cup, and an adhesive or a combination thereof at a base thereof, and laser peening is performed by the fixed structure portion. The laser peening device according to the above [1] or the above [2], which is configured to be fixed to a target steel structure.
[4] The motion control device is characterized in that it has a function of setting position information for determining a laser peening region by setting the planar shape of the laser peening region to a rectangle or an ellipse. The laser peening device according to any one of 1] to [3] above.
[5] Further, it has a liquid recovery system that collects the liquid ejected from the liquid injection nozzle onto the surface of the metal material to be irradiated to the liquid supply unit, and has an atmosphere in which the surface of the metal material to be irradiated is wet with the liquid. The laser peening apparatus according to any one of the above [1] to the above [4], which is configured to circulate and use the liquid for keeping the liquid.
[6] The ejection port of the liquid injection nozzle is installed at a position 1 cm or more away from the laser irradiation position (focus of the laser beam) on the surface of the metal material to be irradiated, and the liquid ejected from the liquid injection nozzle is a laser. The angle and position of the ejection port of the liquid injection nozzle and the hydraulic pressure of the liquid ejected from the ejection port of the liquid injection nozzle are configured to be adjustable so as to hang on the irradiation position. The laser peening device according to any one of the above [1] to [5].
[7] The laser peening apparatus according to any one of the above [1] to [6], wherein the liquid ejected from the liquid injection nozzle is ejected at a hydraulic pressure of 0.2 MPa or less.

According to the present invention, it is possible to transport and install a laser peening device on a steel structure to be laser peened, such as a repair site of a steel bridge, and easily perform laser peening. Fatigue strength improvement effect can be expected. In addition, since laser peening can be applied to any material, it can be applied to high-strength steel materials, which have been increasing in recent years, and to objects such as conventional hammer peening, which have been difficult to apply. Furthermore, if the initial adjustment is set, the construction can be performed semi-automatically, there is no variation depending on the builder, and stable construction quality can be ensured.

It is the schematic which shows an example of the laser peening apparatus which concerns on this invention. It is a schematic view which shows the laser peening position of the welded joint end part of a steel bridge, FIG. 2A is a plan view seen from the direction facing the area of laser peening, and FIG. 2B is FIG. 2A. It is a side view.

Hereinafter, the laser peening apparatus according to the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a schematic view showing an example of a laser peening device according to the present invention.

The laser peening device 1 according to the present invention includes an articulated robot arm 2, a laser irradiation head 3 attached to the tip of the articulated robot arm 2, a liquid injection nozzle 4, a position measuring device 5, and an articulated robot arm 2. It has a laser transmitter 6, a liquid supply unit 7, and an operation control device 8 installed at different positions from the above. The laser irradiation head 3, the liquid injection nozzle 4, and the position measuring device 5 each have an irradiation direction of the laser irradiation head 3, an injection direction of the liquid injection nozzle 4, and a measurement direction of the position measurement device 5 at one point in a certain space. They are arranged so as to overlap each other, and these three overlapping positions are the laser peening construction positions. By electrically operating one or more joints of the articulated robot arm 2, the laser peening construction position moves up, down, left and right. As the articulated robot arm 2 to be used, a small device having a mass of about 10 kg is sufficient.

In the laser peening device 1 of FIG. 1, the laser irradiation head 3, the liquid injection nozzle 4, and the position measuring device 5 are attached to the tip of the articulated robot arm 2, but the liquid injection nozzle 4 and the position measuring device 5 are many. It may be installed at a position different from that of the joint robot arm 2. However, also in this case, the liquid injection nozzle 4 and the position so that the irradiation direction of the laser irradiation head 3, the injection direction of the liquid injection nozzle 4, and the measurement direction of the position measuring device 5 overlap at one point in a certain space. It is necessary to arrange the measuring device 5.

When the liquid injection nozzle 4 is installed at the tip of the articulated robot arm 2 or at a position different from that of the articulated robot arm 2, the laser light and liquid emitted from the laser irradiation head 3 In order to prevent the liquid ejected from the injection nozzle 4 from merging before colliding with the irradiated metal material, the ejection port 4a of the liquid injection nozzle 4 is located at the laser irradiation position (laser light) on the surface of the irradiated metal material. It is preferable to install the liquid injection nozzle 4 so as to be at a position separated from the focal point) by 1 cm or more. Further, the angle and position of the ejection port 4a and the hydraulic pressure of the liquid ejected from the ejection port 4a can be adjusted so that the liquid ejected from the liquid injection nozzle 4 is applied to the laser irradiation position. preferable.

Further, the hydraulic pressure of the liquid ejected from the liquid injection nozzle 4 is preferably about 0.2 MPa or less so that the liquid reaches the laser verification position, the generation of bubbles is suppressed, and the rebound is reduced. The liquid to be used is preferably a substance having high transparency, that is, substantially transparent, nonflammable, and having little chemical action on the irradiated metal material, specifically water or the like.

As shown in FIG. 1, by attaching the laser irradiation head 3, the liquid injection nozzle 4, and the position measuring device 5 to the tip of the articulated robot arm 2, the configuration of the laser peening device 1 can be simplified. It is preferable to attach the injection nozzle 4 and the position measuring device 5 to the tip of the articulated robot arm 2.

The laser irradiation head 3 is connected to the laser transmitter 6 via a laser transmission cable 9 made of an optical fiber cable or the like, and the pulsed laser light emitted from the laser transmitter 6 is transmitted to the laser irradiation head via the laser transmission cable 9. It is configured to be sent to 3 and irradiated from the tip of the laser irradiation head 3 toward the metal material to be irradiated. The liquid injection nozzle 4 is connected to the liquid supply unit 7 via a liquid supply pipe 10, and the liquid supplied from the liquid supply unit 7 is sent to the liquid injection nozzle 4 via the pipe 10 to inject liquid. It is configured to be ejected from the tip of the nozzle 4 toward the metal material to be irradiated. Here, the liquid supply pipe 10 may be a flexible hose-shaped pipe.

The motion control device 8 is connected to the articulated robot arm 2 via a communication-power cable 11, and the articulated robot arm 2 is configured so that its motion is controlled by a signal input from the motion control device 8. ing. Further, the motion control device 8 is connected to the position measuring device 5 via a communication-power cable 12, and the position information measured by the position measuring device 5 and transmitted from the position measuring device 5 is input to the motion control device 8. It is configured to be. FIG. 1 shows an example in which a commercially available personal computer is used as the operation control device 8.

When laser peening a predetermined position of the steel structure 20 using the laser peening device 1 configured in this manner, any one of clamp, magnetic, suction cup, and adhesive is attached to the base of the articulated robot arm 2. It is preferable to provide a fixed structure portion 13 made of one type or a combination thereof, and fix the articulated robot arm 2 to the steel structure 20 to be laser peened by the fixed structure portion 13. By fixing the articulated robot arm 2 to the steel structure 20, the laser beam emitted from the laser irradiation head 3 can be reliably and quickly irradiated to the target position of the steel structure 20.

A part of the steel structure 20 is composed of a steel material 21 and a steel material 22, and the steel material 21 and the steel material 22 are joined by a welded portion 23 made of a weld metal. In FIG. 1, the surface of the welded portion 23 between the steel material 21 and the steel material 22 forming a part of the steel structure 20 and the steel material 21 around the welded portion 23 is the irradiated metal material, that is, the laser peening target position 24. ..

In performing laser peening of the laser peening target position 24, first, the laser peening target position 24 is set and stored in the operation control device 8. Then, the motion control device 8 confirms that the position measured by the position measuring device 5 is the laser peening target position 24 based on the position information transmitted from the position measuring device 5. When the position measured by the position measuring device 5 is different from the laser peening target position 24, one or more joints of the articulated robot arm 2 are electrically operated by a signal from the motion control device 8 and measured by the position measuring device 5. The position to be formed is matched with the laser peening target position 24.

Next, power is supplied to the laser transmitter 6 to generate a pulsed laser beam, and this pulsed laser beam is sent to the laser irradiation head 3 via the laser transmission cable 9 to reach the laser peening target position 24 from the tip of the laser irradiation head 3. Aim and irradiate a pulsed laser beam. At the same time as or before and after the irradiation of the pulsed laser beam, the liquid supply unit 7 is operated to supply the liquid from the liquid supply unit 7 to the liquid injection nozzle 4 via the liquid supply pipe 10, and the liquid injection nozzle 4 A liquid is ejected from the tip toward the laser peening target position 24. The liquid ejected from the liquid injection nozzle 4 keeps the surface of the laser peening target position 24 in an atmosphere wet with the liquid. Water such as tap water is used as the liquid.

A pulsed laser beam having a pulse width of ^{about 10 to 8} seconds or less is focused on a spot having a diameter of about 1 mm by a condenser lens (not shown) provided on the laser irradiation head 3 and irradiated on the surface of the metal material to be irradiated. Then, the surface of the irradiated metal material absorbs energy and turns into a plasma.

When the circumference of the generated plasma is covered with a liquid that is transparent to the wavelength of the pulsed laser light, the expansion of the plasma is hindered and the internal pressure of the plasma reaches about several GPa, hitting the surface of the metal material to be irradiated. .. At that time, a strong shock wave is generated, and this shock wave propagates inside the irradiated metal material to cause plastic deformation, and the tensile stress remaining in the irradiated metal material is converted into compressive stress. Stress improvement under normal construction conditions is possible up to a depth of about 1 mm from the surface of the metal material to be irradiated.

The area of the laser peening target position 24 is about 50 mm × 20 mm or more. Further, since the residual tensile stress changes to compressive stress as the number of times of irradiation of the pulsed laser light increases, it is preferable to irradiate the same portion on the surface of the metal material to be irradiated with the pulsed laser light at least twice. By controlling the pulse width of the pulsed laser light, the diameter of the pulsed laser light, and the moving speed of the pulsed laser light, the irradiation positions of the pulsed laser light overlap each other, and the same portion can be irradiated twice or more.

The motion control device 8 controls the motion of the articulated robot arm 2 so that the pulsed laser beam irradiates the entire region of the laser peening target position 24 set in advance in the motion control device 8.

At that time, when the plane shape of the laser peening target position 24 is rectangular or elliptical, the motion control device 8 preferably has a function of setting position information for determining the region of the laser peening target position 24. .. Specifically, when the plane shape of the laser peening target position 24 is rectangular, two diagonal points of the rectangle are specified in advance, and when it is elliptical, the center position, the minor axis end, and the major axis end are specified. Specify 3 points in advance. A control program is created and executed so that the designated position is stored in the motion control device 8 and the pulsed laser beam is uniformly irradiated to the region of the laser peening target position 24 under the control of the motion control device 8. By providing the motion control device 8 with such a function, the laser peening construction can be performed semi-automatically.

Further, the laser peening device 1 according to the present invention is a liquid composed of a liquid receiving container 14, a pipe 16, a tank (with a filter) 15, and a pipe 17 in order to circulate and use the liquid injected from the liquid injection nozzle 4. It is preferable to have a recovery system. The liquid injected from the liquid injection nozzle 4 is collected in the removable liquid receiving container 14, and the collected liquid is sent from the liquid receiving container 14 to the tank (with a filter) 15 via the pipe 16 and further, the tank (with a filter). It is collected from the (with filter) 15 to the liquid supply unit 7 via the pipe 17.

As described above, according to the present invention, it is possible to carry and install the laser peening device 1 on a steel structure to be laser peened, such as a repair site of a steel bridge, and easily perform laser peening. Therefore, the effect of improving the fatigue strength of the steel structure can be expected.

The present invention is not limited to the scope of the above description, and various modifications can be made. For example, in the above description, the laser irradiation head 3 and the laser transmitter 6 are connected via the laser transmission cable 9, but the laser irradiation head 3 and the laser transmitter 6 may be integrally configured. Although the liquid injection nozzle 4 and the liquid supply unit 7 are connected to each other via the pipe 10, the liquid injection nozzle 4 and the liquid supply unit 7 may be integrally configured.

Further, in the above description, the articulated robot arm 2 and the motion control device 8 are connected via the communication-power cable 11, and the position measuring device 5 and the motion control device 8 are connected via the communication-power cable 12. Although they are connected, they may be connected wirelessly without going through the communication-power cable 11 and the communication-power cable 12.

At the repair site of a steel bridge, using the laser peening device 1 according to the present invention shown in FIG. 1, as shown in FIG. 2, the end of the welded joint between the steel material 21 and the steel material 22 constituting a part of the steel bridge. Laser peening was performed by designating the area of the weak point on fatigue. The plate thickness of the steel material 22 was 20 mm, the width of the weld bead was 10 mm, and the range of laser peening was set to 60 mm with the range of 10 mm on both sides from the weld toe. In FIG. 2, reference numeral 23 is a welded portion, and 24 is a laser peening target position (area; 60 mm × 30 mm). Since the tip of the rotary weld as shown in FIG. 2 is particularly susceptible to fatigue damage, laser peening was performed by designating a region covering the end. 2A and 2B are schematic views showing a laser peening position at the end of a welded joint of a steel bridge, FIG. 2A is a plan view seen from a direction facing the laser peening region, and FIG. 2B is a plan view. It is a side view of FIG. 2 (A).

The planar shape of the laser peening target position 24 is rectangular, two points P and Q on the diagonal of the rectangle are stored in advance in the motion control device 8, and the P point is set as the start point and the Q point under the control of the motion control device 8. The operation of the articulated robot arm 2 was controlled so that the area of the laser peening target position 24 was uniformly irradiated with the pulsed laser beam.

After the laser peening was performed, the residual stress in the area subjected to the laser peening was measured by an ultrasonic sound elastic residual stress device. As a result, only the compressive stress was measured as the residual stress.

1 Laser peening device 2 Articulated robot arm 3 Laser irradiation head 4 Liquid injection nozzle 5 Position measurement device 6 Laser transmitter 7 Liquid supply unit 8 Operation control device 9 Laser transmission cable 10 Tube 11 Communication-Power cable 12 Communication-Power cable 13 Fixed structure 14 Liquid receiving container 15 Tank (with filter)
16 Piping 17 Piping 20 Steel structure 21 Steel 22 Steel 23 Welded part 24 Laser peening target position

Claims (6)

Laser transmitter and
A laser irradiation head that irradiates the surface of the metal material to be irradiated with pulsed laser light emitted from the laser transmitter, and
A laser transmission cable connecting the laser transmitter and the laser irradiation head,
A liquid injection nozzle that injects a liquid to keep the surface of the metal material to be irradiated in an atmosphere wet with the liquid, and
A liquid supply unit that supplies liquid to the liquid injection nozzle,
A pipe for supplying a liquid, which connects the liquid injection nozzle and the liquid supply unit,
A position measuring device for measuring the irradiation position of the pulsed laser beam on the irradiated metal material, and
An articulated robot arm to which the laser irradiation head is attached and
An operation control device that inputs information on the irradiation position of the pulsed laser beam on the irradiated metal material transmitted from the position measuring device and controls the operation of the articulated robot arm based on the input irradiation position information. When,
It is a laser peening device with
The motion control device is configured to control the motion of the articulated robot arm so that the pulsed laser beam irradiates the entire area of laser peening set in advance in the motion control device .
The ejection port of the liquid injection nozzle is installed at a position 1 cm or more away from the laser irradiation position (focus of the laser beam) on the surface of the metal material to be irradiated, and the liquid ejected from the liquid injection nozzle is located at the laser irradiation position. A laser peening device characterized in that the angle and position of the ejection port of the liquid injection nozzle and the hydraulic pressure of the liquid ejected from the ejection port of the liquid injection nozzle are configured to be adjustable so as to hang. The laser peening device according to claim 1, wherein the liquid injection nozzle and the position measuring device are attached to the articulated robot arm. The articulated robot arm has a fixed structure portion formed of any one of a clamp, a magnetic, a suction cup, and an adhesive or a combination thereof at a base thereof, and is subject to laser peening by the fixed structure portion. The laser peening apparatus according to claim 1 or 2, wherein the laser peening apparatus is configured to be fixed to a steel structure. The motion control device according to claim 1, wherein the motion control device has a function of setting position information for determining a laser peening region by setting the planar shape of the laser peening region to a rectangle or an ellipse. Item 3. The laser peening device according to any one of Items 3. Further, in order to have a liquid recovery system for recovering the liquid ejected from the liquid injection nozzle onto the surface of the metal material to be irradiated to the liquid supply unit, and to keep the surface of the metal material to be irradiated in an atmosphere wet with the liquid. The laser peening apparatus according to any one of claims 1 to 4, wherein the liquid is configured to be used in a circulating manner. The laser peening apparatus according to any one of claims 1 to 5 , wherein the liquid ejected from the liquid injection nozzle is ejected at a hydraulic pressure of 0.2 MPa or less.

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