Method for gun barrel manufacture using tailored autofrettage mandrels
AssigneeUnited Defense, L.P.
InventorsMichael J. Hermanson, Brian Bauman, Donald A. Nalley
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Abstract
A method of manufacturing a monobloc gun barrel by calculating an optimal residual stress profile and then applying tailored autofrettage mandrels which are mechanically pressed down the bore of a large caliber barrel, the mandrel size optimized to create a residual stress distribution on the interior of the bore within the design constraints imposed by the worst-case heat flux scenario.
Claims18
A method of manufacturing a thick walled large caliber gun barrel, wherein the barrel requires active cooling to maintain a rate of fire, comprising the steps of:
- calculating a thermal profile for the barrel based on barrel geometry, barrel material and heat flux produced from a maximum fire rate scenario;
- calculating a barrel yield strength of the barrel based on the thermal profile;
- calculating a maximum residual stress profile based on the barrel yield strength;
- forging the barrel;
- mapping the inner diameter of the barrel;
- testing the yield strength of the barrel forgings;
- constructing a mandrel, wherein said mandrel is sized according to the inner diameter of the barrel, yield strength of the forging and residual stress profile;
- pressing the mandrel through the barrel;
- machining the outer diameter of the barrel to its finished dimensions;
- and
- machining the inner diameter of the barrel to its finished dimensions.
A method of subjecting a gun barrel to autofrettage wherein the inner bore of said barrel is subjected to pressure resulting in a plastic deformation of less than the thickness of the barrel wall, said method comprising;
- establishing a thermal profile for the barrel based on barrel geometry and heat input from a worst-case scenario fire rate;
- calculating an autofrettage stress that the barrel can support based on the thermal profile;
- measuring a yield strength of each barrel forging;
- mapping the inner bore diameter;
- constructing a mandrel sized to produce the autofrettage stress based on the yield strength and dimensions of an individual barrel;
- and
- applying said autofrettage stress by ramming said mandrel in a single pass through the inner bore of the barrel.
Dependencies are inferred from the claim text.