Patent ID: 8590767

Claim:
A method for welding a hollow structure, comprising: preparing a first joining member having a length in a vertical direction, wherein the first joining member has: an upper side part formed at an upper edge portion of the first joining member in a horizontal direction with respect to the vertical direction, the upper side part having an inner side and an outer side; and a lower side part formed at a lower edge portion of the first joining member in a horizontal direction with respect to the vertical direction, the lower side part having an inner side and an outer side; preparing a second joining member having a length in the vertical direction, wherein the second joining member has: only one recessed upper joining part formed at an upper side of the second joining member, sized to receive the upper side part of the first joining member; only one recessed lower joining part formed at a lower side of the second joining member, sized to receive the lower side part of the first joining member; only one upper protruded part that extends in the horizontal direction toward the upper side part of the first joining member such that an inner side of the upper protruded part contacts the outer side of the upper side part while the inner side of the upper side part contacts a bottom surface of the recess in the upper joining part when the upper side part is inserted into the upper joining part; and only one lower protruded part that extends in the horizontal direction toward the lower side part of the first joining member such that an inner side of the lower protruded part contacts the outer side of the lower side part while the inner side of the lower side part contacts a top surface of the recess in the lower joining part when the lower side part is inserted into the lower joining part; and joining the first joining member and the second joining member by friction stir welding, wherein the friction stir welding is conducted using a tool that includes a cylindrical shaped body and a probe that extends outward from an underside portion of the body.