A pipe is formed by press molding a U-shaped member including a U-shaped cross section. The U-shaped cross section includes at least five curved portions. The curved portions include a center curved portion facing an opening of the U-shaped cross section defined by both edges of the U-shaped cross section; a first right curved portion; a second right curved portion; a first left curved portion; and a second left curved portion. At least the center curved portion, the first right curved portion, and the first left curved portion each have a radius of curvature smaller than a radius of curvature of a corresponding portion of the pipe cross section.

A hollow shaft includes a cylindrical main body part and an extremity drawn part that is integrally connected to one end of the main body part on the same axis and whose diameter is made smaller than a diameter of the main body part by drawing processing, wherein an inner peripheral face of the main body part and an inner peripheral face of a base portion, which is continuous with one end side of the main body part, of the extremity drawn part are formed as cut faces that are subjected to cutting processing before the drawing processing, and an inner peripheral face of a tip portion, which is continuous with an extremity side of the base portion, of the extremity drawn part is a non-cut face. Accordingly, the hollow shaft can be molded with high shape precision while maintaining a low drawing ratio for an extremity drawn part.

A hollow shaft includes a cylindrical main body part and an extremity drawn part that is integrally connected to one end of the main body part on the same axis and whose diameter is made smaller than a diameter of the main body part by drawing processing, wherein an inner peripheral face of the main body part and an inner peripheral face of a base portion, which is continuous with one end side of the main body part, of the extremity drawn part are formed as cut faces that are subjected to cutting processing before the drawing processing, and an inner peripheral face of a tip portion, which is continuous with an extremity side of the base portion, of the extremity drawn part is a non-cut face. Accordingly, the hollow shaft can be molded with high shape precision while maintaining a low drawing ratio for an extremity drawn part.

A segmental tube section structure having a length and a circumference, the segmental tube section structure including a plurality of tube segments extending the length in a longitudinal direction of the segmental tube section structure and extending in a circumferential direction of the segmental tube section structure, wherein each tube segment of the plurality of tube segments extends in the circumferential direction to span an equal arc of the circumference of the segmental tube section, and wherein each of the plurality of tube segments are connected to adjacent tube segments of the plurality of tube segments in the circumferential direction to form the segmental tube section structure.

A segmental tube section structure having a length and a circumference, the segmental tube section structure including a plurality of tube segments extending the length in a longitudinal direction of the segmental tube section structure and extending in a circumferential direction of the segmental tube section structure, wherein each tube segment of the plurality of tube segments extends in the circumferential direction to span an equal arc of the circumference of the segmental tube section, and wherein each of the plurality of tube segments are connected to adjacent tube segments of the plurality of tube segments in the circumferential direction to form the segmental tube section structure.

A manufacturing method of a member according to an aspect of the present invention is a manufacturing method of a member including a specific three-dimensional tubular portion, the manufacturing method including: a U-forming step of performing U-forming on metal material sheet using a U-forming die and punch including a U-forming punch to manufacture a U-formed article having a recessed cross-sectional shape; and an O-forming step of causing side end portions of the U-formed article to abut each other by an O-forming die to form abutting portions, in which a forming condition ratio a=Du/Do is set to 0.85 to 0.95.

A manufacturing method of a member according to an aspect of the present invention is a manufacturing method of a member including a specific three-dimensional tubular portion, the manufacturing method including: a U-forming step of performing U-forming on metal material sheet using a U-forming die and punch including a U-forming punch to manufacture a U-formed article having a recessed cross-sectional shape; and an O-forming step of causing side end portions of the U-formed article to abut each other by an O-forming die to form abutting portions, in which a forming condition ratio a=Du/Do is set to 0.85 to 0.95.

A method for manufacturing annular sectors of an air intake lip includes arranging a revolution-shaped blank facing a three-dimensional forming surface of a die of a hydroforming tool, the three-dimensional surface including at least two plunging cavities spaced from each other along a circumferential direction, forming an air intake lip preform in one piece by hydroforming the revolution-shaped blank on the three-dimensional surface of the die, the air intake lip preform having in section a U-shape and including a plurality of crenellated portions each delimited by a plunging cavity, the production of a plurality of cutouts in the air intake lip preform so as to divide the preform into a plurality of annular sectors, each cutout including the removal of a sacrificial portion at the level of a crenellated portion so as to form two adjacent assembly edges with one of the two adjacent assembly edges including a plunging.

A method for manufacturing annular sectors of an air intake lip includes arranging a revolution-shaped blank facing a three-dimensional forming surface of a die of a hydroforming tool, the three-dimensional surface including at least two plunging cavities spaced from each other along a circumferential direction, forming an air intake lip preform in one piece by hydroforming the revolution-shaped blank on the three-dimensional surface of the die, the air intake lip preform having in section a U-shape and including a plurality of crenellated portions each delimited by a plunging cavity, the production of a plurality of cutouts in the air intake lip preform so as to divide the preform into a plurality of annular sectors, each cutout including the removal of a sacrificial portion at the level of a crenellated portion so as to form two adjacent assembly edges with one of the two adjacent assembly edges including a plunging.

An apparatus for backward flow forming a material may comprise a mandrel having a headstock at a proximate end of the mandrel, the mandrel configured to rotate about an axis, a plurality of rollers disposed radially outward of the mandrel configured to exert force on the material to form a work piece at a plastic deformation zone, wherein the work piece flows from the plastic deformation zone between the plurality of rollers and the mandrel toward a distal end of the mandrel, and a catcher, coaxial to the mandrel, and removably coupled to the work piece at a traveling end of the work piece.