초록 ▼

A method of making an monolithic metallic sandwich structure includes selecting at least two chemically clean metal core sheets having superplastic characteristics and placing them face-to-face. The core sheets are welded together into a core pack along intersecting lines that will form junction lin

A method of making an monolithic metallic sandwich structure includes selecting at least two chemically clean metal core sheets having superplastic characteristics and placing them face-to-face. The core sheets are welded together into a core pack along intersecting lines that will form junction lines of webs defining cells between the core sheets when the core pack is expanded superplastically. Gaps are left adjacent to the intersections of the weld lines to produce openings through which gas can pass to pressurize each cell. The position of the gaps adjacent the weld line intersections minimizes strain on the marginal regions around the openings as the core pack is inflated, to reduce the tendency of the sheets to tear or rupture around the openings. A gas pressure line fitting is inserted between one edge and the core pack is welded around its periphery with the gas fitting protruding from the edge for connection to a gas source that will purge and pressurize the core pack with gas. Two chemically cleaned metal face sheets having superplastic characteristics are placed over and under the core pack, and all four sheets are peripheral seal welded to produce a sealed envelope pack enclosing the core pack, with gas fittings into the core pack and into a face sheet zone between the face sheets and the core pack. Dry Argon is admitted through the gas fittings to purge air and moisture from the packs and then to pressurize the packs to a low pressure to maintain separation of the sheets while heating to prevent premature diffusion bonding. The full pack is placed in an internal cavity of a heated die and is raised to superplastic temperatures. Forming gas is injected through the fittings at a forming pressure sufficient to inflate the envelope pack to the interior walls of the cavity, and inflate the core pack to the envelope pack and to diffusion bond the face sheets to the core sheets. After forming, the die is opened and the formed pack is removed.

대표청구항 ▼

[ We claim:] [1.] A method of making an monolithic metal sandwich structure, comprising:selecting at least two metal sheets having superplastic characteristics for forming a core of said sandwich structure, said core sheets having a surface area and planar shape at least equal to the plan size and s

[ We claim:] [1.] A method of making an monolithic metal sandwich structure, comprising:selecting at least two metal sheets having superplastic characteristics for forming a core of said sandwich structure, said core sheets having a surface area and planar shape at least equal to the plan size and shape of said core of said metal sandwich structure;placing said core sheets in a vertical stack;inserting a gas pressure line fitting between said core sheets on at least one edge thereof, said fitting having a through bore communicating through said fitting into an interior region between said core sheets;welding said gas pressure line fitting to said core sheets;pressing said core sheets together and welding said core sheets forming a core pack, said welding being done along intersecting weld lines which will form junction lines between said core sheets and delineate cells within said core pack when said core pack is superplastically expanded;leaving gaps in said weld lines through which gas can pass from said gas pressure line fitting into and through said cells, said gaps being located adjacent intersections of said weld lines;selecting at least two additional metal sheets having superplastic characteristics for forming face sheets of said sandwich structure;placing one each of said sheets on top and bottom faces of said core pack and placing an envelope gas fitting between said face sheets;sealing peripheral edges of said face sheets to peripheral edges of said core pack and sealing said gas fittings between said face sheets to produce a sealed envelope pack enclosing said core pack, with gas fittings into said core pack and into a face sheet zone between said face sheets and said core pack;connecting a gas supply tube from a gas supply control system to each of said fittings and purging air and moisture from said packs;pressurizing said packs to a low pressure with an inert forming gas such as argon, said core pack being pressurized to a higher pressure than said envelope pack;placing said full pack in an internal cavity of a heated die, said cavity having the same shape as the desired shape of the metal sandwich structure after it is expanded;raising the temperature of said full pack in said die to a temperature at which said metal exhibits superplastic characteristics;injecting forming gas through said fittings at a forming pressure sufficient to inflate said envelope pack to the interior walls of said cavity, and inflate said core pack to said envelope pack;forming said envelope pack against the interior walls of said cavity, and forming said core pack against inside surfaces of said envelope pack while folding said sheets of said core pack over on themselves about said weld lines to form said webs and expand said weld gaps into openings in said webs;maintaining said forming gas pressure until said core sheets are diffusion bonded to said face sheets and are diffusion bonded to themselves to form said webs;opening said die and removing said formed pack from said die;allowing said formed pack to cool and removing said gas supply lines from said gas fittings.