JP2024068259A - Crack repair device - Google Patents

Abstract

The present invention provides a device that can easily repair cracks. The device includes an injection unit that injects granular filler into the cracks, and an irradiation unit that irradiates the filler with laser light to melt it. [Selected Figure] Figure 1

Description

Application for application of Article 30, Paragraph 2 of the Patent Act has been filed. (1) Academic paper. Disclosure date: November 9, 2021. Disclosed publication: DVD collection of the 65th Space Sciences and Technology Conference. (2) Academic paper. Disclosure date: August 1, 2022. Disclosed publication: Abstracts of the 77th Annual Academic Conference of the Japan Society of Civil Engineers (3) Academic paper. Disclosure date: November 1, 2022. Disclosed publication: DVD collection of the 66th Space Sciences and Technology Conference.

The present invention relates to a device for repairing cracks.

Conventionally, a method has been known for repairing cracks that have occurred in tunnels or rock formations using a filler such as water glass (for example, Patent Document 1).

JP 2012-092186 A

With conventional methods, it takes time for the filler to penetrate the cracks and it is costly to prepare the filler.

In one embodiment, the present invention provides a device that includes an injection unit that injects granular filler into a crack, and an irradiation unit that irradiates the filler with laser light to melt it.

The present invention provides a device that can easily repair cracks.

Schematic diagram of a lava tube. 1A and 1B are a side view and a bottom view showing an apparatus 1 according to an embodiment. FIG. 1 is a diagram illustrating the configuration of the device 1. 1A to 1C are diagrams illustrating a situation in which a bead is formed using the device 1. FIG. 1A is a diagram showing the dimensions of the test specimen, FIG. 1B is a diagram showing the shape of the test specimen after repair, and FIG. 1C is a diagram showing the loading conditions of the strength test of the test specimen. 1 is a table showing conditions used in groove repair of test specimens.

The present invention will be described below with reference to one embodiment of the invention.

〔composition〕
2 shows an apparatus 1 according to an embodiment of the present invention. The apparatus 1 is an apparatus that uses directed energy deposition (DED) to repair cracks in rocks and concretes, cracks in fired materials obtained by firing inorganic compound materials such as sand or clay, or cracks in sintered materials obtained by sintering inorganic compound materials such as sand or clay, particularly cracks in lunar lava tubes L. Note that concretes refer to hardened materials that contain cement, such as concrete, mortar, or grout.

As shown in Figure 1, lava tube L is a tubular object formed after lava flows about 100 m below the surface of the moon, and has a cavity inside.

Lava tubes are formed when lava cools and hardens, so there are cracks C on the surface caused by contraction during hardening.

Lava Tube L is about 100 meters in diameter and several to several tens of kilometers long. Due to its size and structure, Lava Tube L has been named as a possible site for building a lunar base.

When building a living facility such as a base inside the lava tube L, it is necessary to fill the inside with air and maintain a pressure of 1 atmosphere. For this reason, the lava tube L must be airtight.

To maintain the airtightness of the lava tube L, it is necessary to seal the crack C, and the device 1 is used to prevent this crack C.

As shown in FIG. 2(a), the device 1 has an irradiation head 11, a laser irradiation unit 12, and an ejection unit 13. In the following, the up, down, left, and right directions are defined as shown in FIG. 2, and the following description will be based on these directions.

The irradiation head 11 is a member formed in a roughly disk shape that extends horizontally, and has the function of holding the laser irradiation unit 12 and the injection unit 13.

The laser irradiation unit 12 includes a laser oscillator 121 that performs high-power laser oscillation, and an optical system 122 that is composed of one or more lenses (Figs. 2 and 3). The laser light emitted from the laser oscillator 121 is irradiated downward through the optical system 122, as shown by the dotted line in Fig. 3.

As shown in Figures 2 and 3, the injection unit 13 includes a storage unit 131 that stores the filler 30, an injection port 132 that is an opening that injects the filler 30 downward, a tube unit 133 that connects the storage unit 131 and the injection port 132, and a pressurizing unit 134 that applies pressure to the filler 30 using gas.

The filler 30 stored in the storage unit 131 can be a variety of materials, but it is preferable that it is a material that melts and vitrifies at high temperatures, such as a material that contains silicon. In the following explanation, sand from the moon or the earth will be used as the filler 30.

FIG. 2B is a view of the irradiation head 11 viewed from below. The injection ports 132 are formed at three locations on the lower part of the irradiation head 11, equally spaced in the circumferential direction and at the same distance from the optical system 122.
The pressurizing unit 134 holds a high-pressure gas. The pressurizing unit 134 has a function of supplying the gas to the filler 30 stored in the storage unit 131 and pressurizing the filler 30 using the gas. The pressurizing unit 134 and the storage unit 131 have internal spaces connected to each other. The filler 30 in the storage unit 131 moves through the tube unit 133 together with the gas supplied from the pressurizing unit 134 and is sprayed from the spray nozzle 132.

The filler material 30 irradiated from the three injection ports 132 is injected so as to converge at a focal point F, as shown by the dotted lines in FIG. 3. The focal point F is located directly below the optical system 122. The filler material 30 injected at the focal point F can be irradiated with the laser light emitted from the optical system 122.

<Crack repair work>
The following describes the repair work for the crack C that has occurred in the lava tube L. First, the worker focuses F on the position of the crack C to be repaired.

Next, the worker operates the device 1 to perform thermal spraying. During thermal spraying, the device 1 simultaneously irradiates the laser light and sprays the filler material 30. The filler material 30 sprayed at the focal point F fills the inside of the crack C, and is melted and vitrified by the laser light.

As the operator moves the focal point F along the crack C, the thermal spraying process is performed continuously along the crack C, and the filler material 30 is melted and filled along the crack C.

The filler 30 filled into the crack C cools and hardens over time. The filler 30 melts into the surrounding base material and hardens as one with it. In this way, the repair of the crack C is completed.

When the crack C has a large width, as shown in FIG. 4, the device 1 moves (sweeps) the irradiation head 11 along the surface of the crack C and the lava tube L, spraying to form multiple beads. By stacking the beads, the filler material 30 seals the crack C and hardens to become integrated with the surroundings.

<Experiment>
A test was carried out to confirm the strength of the repaired portion formed as described above.

The experiment was conducted using a test specimen S having a wedge-shaped groove, as shown in Figure 5(a). Specifically, filler 30 was sprayed into the groove of the test specimen S using device 1 and melted by a laser. In addition, the focal point F was swept along the groove at a speed of 7.5 millimeters per second to deposit multiple beads. The laser output was 300 W. Other test conditions are shown in Figure 6. In this way, the groove was joined, and the test specimen S was shaped like an approximately rectangular parallelepiped. The dimensions of the test specimen S before and after groove joining are as shown in Figures 5(a) and (b).

Lunar simulant sand was used for the filler 30. Specifically, lunar soil simulant FJS-1, made from volcanic lava rock, was used as the filler 30. The main chemical composition of simulant FJS-1 is 49.8% SiO2, 19.9% Al2O3, and 10.2% CaO. This falls within the upper and lower limits of the particle size distribution of lunar soil collected during the Apollo program, with the 50% particle size being 0.067 mm.

The test specimen S was formed by sintering simulated sand to simulate the surface of the lava tube L.

After groove welding, a bending load was applied to the test specimen S to measure its strength. The strength was measured by simply supporting the test specimen S and applying a concentrated load to the center between the supports, as shown in Figure 5 (c).

As a result of the test, a bending strength of 1 to ² N/mm2 was measured, and it was found to have a certain level of strength. The fracture during the test occurred not at the boundary between the filler 30 and the base material (test piece S before repair), but through the center of the filler 30 (Figure 5 (c)). It can be seen that the base material and the filler 30 are bonded with sufficient strength.

<Modification>
The repair of the crack C by the above-mentioned device 1 can be widely applied not only to the lava tube L but also to objects and structures containing silicon, such as concrete structures and rocks. For example, the above-mentioned device 1 and repair method can be applied to repairing rock masses and cracks in tunnels. Since the filler 30 is vitrified and hardens integrally with the base material for such objects and structures, the device 1 can be used to perform the crack repair work in the same manner as described above.

The material for the filler 30 is not limited to lunar sand, and sand on the Earth may be used. Other materials, such as crushed lava, may also be used. It is considered preferable to use powder or granules containing silicon as the filler 30.

In the above embodiment, the work was performed by melting the filler material 30 within the crack. Alternatively, the repair work for the crack C may be performed by spraying the molten filler material 30.

＜Effects＞
(Aspect 1) In the above embodiment or variant example, an apparatus 1 is presented that includes an injection unit 13 that injects granular filler 30 into cracks C in concrete or rock, and a laser irradiation unit 12 that irradiates laser light onto the filler 30 to melt it.

In the above embodiment, the device 1 can repair cracks C that have occurred in rocks such as concrete and lava with sufficient strength. In addition, because the filler is heated by irradiating it with laser light, the device 1 can reliably carry out repair work even in an oxygen-free environment.

(Aspect 2) In aspect 1, the filler 30 is sand.

As described above, by using sand as the filler 30, it is possible to repair the crack C using an inexpensive material that is easily available.

(Aspect 3) In aspect 2, the filler 30 is moon sand.

By adopting the above-mentioned configuration, when carrying out crack repair work on the Moon, there is no need to transport the filler material 30 from the Earth to the Moon's surface. This makes it possible to easily repair cracks on the Moon, and to smoothly proceed with the construction of residential facilities such as bases.

(Aspect 4) In aspect 3, crack C is a crack that occurred in a lunar lava tube.

The embodiment and modified examples are suitable for repairing cracks C in a lava tube L using lunar sand. Since the composition of lunar sand and lava tube L is almost the same, sufficient strength can be expected. Repairs can be made that are sufficient to maintain the airtightness of the inside of the lava tube L.

(Aspect 5) In any of aspects 1 to 4, the injection unit 13 includes a storage unit 131 that stores the filler 30, an injection port 132 that injects the filler 30 toward the laser light, a tube unit 133 that connects the injection port 132 and the storage unit 131, and a pressurizing unit 134 that applies pressure to the filler 30 stored in the storage unit 131.

The above configuration allows the filler 30 to be efficiently filled inside the crack. In addition, the provision of the pressurizing section 134 makes it possible to spray the filler 30 even in an environment without air.

(Aspect 6) In any of aspects 1 to 5, the ejection unit 13 and the laser irradiation unit 12 move along the crack C and the material surface where the crack C has occurred to form a bead.

The above-mentioned aspect allows the device 1 to reliably perform repairs even on large cracks C.

(Aspect 7) In any of aspects 1 to 6, crack C is a crack that occurs in concrete, a fired material made by firing an inorganic compound material, a sintered material made by sintering an inorganic compound material, or rock.

As described above, the device 1 is widely applicable to concrete, sand, and stone materials.

Reference Signs List 1 Apparatus 11 Irradiation head 12 Laser irradiation unit 13 Injection unit 30 Filling material

Claims (7)

An injection unit that injects granular filler into the cracks;
An irradiation unit that irradiates the filler with laser light to melt it;
An apparatus comprising: The filler is sand.
2. The apparatus of claim 1. The filler is moon sand.
3. The apparatus of claim 2. The crack is a crack in a lunar lava tube.
The method according to claim 3. The injection unit is
A storage section for storing the filler;
an injection port that injects the filler toward the laser light;
A pipe portion connecting the injection port and the storage portion;
The device according to claim 1 or 2, further comprising: a pressurizing unit that applies pressure to the filler stored in the storage unit. The ejection unit and the irradiation unit move along the crack and the material surface where the crack occurs to form a bead.
3. Apparatus according to claim 1 or 2. The crack is a crack occurring in any one of concrete, a fired material obtained by firing an inorganic compound material, a sintered material obtained by sintering an inorganic compound material, and rock.
The method according to claim 1 or 2.

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