Abstract: Irradiation with a laser beam is performed along a welding bead, while the laser beam is aimed, as an irradiation point of the laser beam, at a contact point between a deck plate and a U-rib that is contained in a non-welded portion of a root part, from a side of the welding bead of the root part. Thereby, it is possible to remove a crack beginning at the non-welded portion of the root part generated at a joining portion between the deck plate and the U-rib of a steel floor slab, by the irradiation with the laser beam.

Abstract: A metal-resin joining method of joining a metal member to a composite material member including a fiber reinforced plastic composite material includes an applying step of applying a first adhesive that is a thermosetting adhesive to a first region between the metal member and the composite material member, and applying a second adhesive that is a thermosetting adhesive to a second region between the metal member and the composite material member, a provisional bonding step of irradiating a first irradiation region of the metal member opposed to the first region with a laser light, and heating and curing the first adhesive to provisionally bond the metal member and the composite material member together, and a main bonding step of curing the second adhesive after the provisional bonding step to bond the metal member and the composite material member together.

Abstract: A crack repair method includes a build-up welding step of performing build-up welding on a portion of an existing steel structure where a crack is generated while feeding a filler wire, and a laser beam piercing welding step of performing piercing welding using a laser beam on a filler material build-up portion caused by the build-up welding in the build-up welding step and the crack. The crack can be melted and repaired without lowering a toughness value regardless of an operation condition.

Abstract: Provided is a crack repair method of melting and eliminating a crack generated in a steel material, the method including holding a tab plate in surface contact with the steel material in which the crack is generated, thereafter continuously irradiating the tab plate to a first end portion of the crack in the steel material with a laser beam, and subsequently continuously irradiating the crack with the laser beam along the crack to a second end portion of the crack to melt and eliminate the crack. Consequently, when eliminating the crack generated in a constituent member of an existing structure or a constituent member such as a machine component, the crack can be eliminated without forming a through hole in the constituent member.

Abstract: A laser welding repair device includes a laser oscillator, a laser head that condenses laser light from the laser oscillator to irradiate a repair portion, a temperature sensor that detects a temperature distribution of a steel material irradiated with the laser light, and a control unit. The control unit sets a spot diameter of the laser light to be less than 3 mm, moves the laser head and enlarges a heat input area to check for a crack in the heat input area, the heat input area being formed by irradiating the steel material with the laser light, and controls the laser head to irradiate a region where a temperature detected by the temperature sensor is equal to or less than a mechanical melting temperature of the steel material. Where a welding is performed in a flat position, the crack can be easily and reliably erased without causing burn through.