A method of incremental autofrettage is taught herein, whereby the cycle life of a metal liner in a pressure vessel is increased. This method serves to increase the yield strength of the metal liner through sequential work hardening due to repeated autofrettage at increasing pressures. By incrementally increasing the internal pressure used in the autofrettage process, the compressive stresses at an inner surface of the metal liner may be controlled so that post-pressurization buckling does not occur, yet the yield strength of the metal liner is substantially increased. The higher compressive stresses in the metal liner mean that higher Maximum Expected Operating Pressures (MEOPs) may be used without detracting from the cycle life of the metal liner, or alternatively, for lower pressures, a longer metal liner cycle life may be obtained. Either internal or external pressures may be used, generated by a pressure source, or a suitable die.

Disclosed are a double water pipe manufactured via hydroforming and a method of manufacturing the same. The method includes: inserting an inner pipe into an outer pipe made of steel, the inner pipe being made of a corrosion resistant material selected from among stainless steel, titanium and aluminum, and having a smaller outer diameter than an inner diameter of the outer pipe; placing the outer pipe on a die unit and sealing opposite ends of the die unit with sealing members each having a through-hole connected to a fluid supply unit for supplying a fluid to the inner pipe; supplying the fluid to the inner pipe to perform plastic expansion of the inner pipe and elastic expansion of the outer pipe; and discharging the fluid from the inner pipe to allow frictional coupling between the inner pipe and the outer pipe through elastic restoration of the outer pipe.

Disclosed are a double water pipe manufactured via hydroforming and a method of manufacturing the same. The method includes: inserting an inner pipe into an outer pipe made of steel, the inner pipe being made of a corrosion resistant material selected from among stainless steel, titanium and aluminum, and having a smaller outer diameter than an inner diameter of the outer pipe; placing the outer pipe on a die unit and sealing opposite ends of the die unit with sealing members each having a through-hole connected to a fluid supply unit for supplying a fluid to the inner pipe; supplying the fluid to the inner pipe to perform plastic expansion of the inner pipe and elastic expansion of the outer pipe; and discharging the fluid from the inner pipe to allow frictional coupling between the inner pipe and the outer pipe through elastic restoration of the outer pipe.

A two-section assembly chamber includes a section S1 (11) and a section S2 (12), whose shapes are selected between cylindrical, where section S1 (11) has a diameter larger than the section S2 (12), and in the shape of a conical frustum, where sections S1 (11) and S2 (12) form a conical frustum, where the conical frustum begins at S1 (11) with the wider part and ends at S2 (12) with the narrower part, both sections S1 (11) and S2 (12) are joined or welded together, and are removable, each having respective caps (21, 22), wherein the assembly chamber has at least one perforation for introducing a pressurized fluid. The assembly chamber is configured so that a tube (30) or a second chamber, which has a larger diameter than the section S2 (12), is assembled within the inner diameter of the section S2 (12).

A method for manufacturing a double-wall heat-exchanger tube including an external tube and an internal tube, these tubes being metallic, cylindrical and coaxial. This method includes providing a first tube having an inside diameter d.sub.1int and an outside diameter d.sub.1ext, this first tube being intended to form the external tube, a second tube having an inside diameter d.sub.2int and an outside diameter d.sub.2ext, this second tube being intended to form the internal tube, and a cylindrical coaxial tubular leaf made from Fe.sup.0 having an inside diameter d.sub.int and an outside diameter d.sub.ext, such that 0.15 mm(d1intdext)0.25 mm, 0.15 mm(dintd2ext)0.25 mm, and 10 m(dextdint)200 m.

A method for manufacturing a double-wall heat-exchanger tube including an external tube and an internal tube, these tubes being metallic, cylindrical and coaxial. This method includes providing a first tube having an inside diameter d.sub.1int and an outside diameter d.sub.1ext, this first tube being intended to form the external tube, a second tube having an inside diameter d.sub.2int and an outside diameter d.sub.2ext, this second tube being intended to form the internal tube, and a cylindrical coaxial tubular leaf made from Fe.sup.0 having an inside diameter d.sub.int and an outside diameter d.sub.ext, such that 0.15 mm(d1intdext)0.25 mm, 0.15 mm(dintd2ext)0.25 mm, and 10 m(dextdint)200 m.

A forming assembly for forming a wick is disclosed. The forming assembly includes a tube inflatable to an inflated configuration. A wick mesh is configured to be wrapped about the tube. The forming assembly further includes a sheath positionable about the tube and the wick mesh. The tube and the sheath are configured to compress the wick mesh and form the wick based on the tube inflating towards the inflated configuration.

A forming assembly for forming a wick is disclosed. The forming assembly includes a tube inflatable to an inflated configuration. A wick mesh is configured to be wrapped about the tube. The forming assembly further includes a sheath positionable about the tube and the wick mesh. The tube and the sheath are configured to compress the wick mesh and form the wick based on the tube inflating towards the inflated configuration.

A method and a device for obtaining a joint between two surfaces of two parts that have a simple curvature are proposed in which a mandrel is placed below the first surface, which contains a moving stamp in its interior. A template is placed above the second surface, which has a deep drawing opening. The stamp is moved along the surface normals of the two surfaces, such that material forming the two surfaces is forced into the deep drawing opening, wherein the deep drawn and compressed portion of the first surface engages behind the remaining part of the second surface to obtain a form-fit connection between the two surfaces. The stamp blocks a channel inside the mandrel until pressure from a medium therein causes the stamp to move.

A method of forming a wick using a mandrel is disclosed. The method includes positioning a wick mesh about the mandrel, positioning a sheath about the mandrel and the wick mesh, coupling a first fitting to the mandrel, wherein the first fitting comprises an adapter configured to couple with a source of pressure, and pressurizing the mandrel with the source of pressure to hydraulically expand the mandrel such that that mandrel compresses the wick mesh against the sheath and forms the wick.