Method for gun barrel manufacture using tailored autofrettage mandrels

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.

Description

RELATED APPLICATIONS [0001] This application is a divisional of U.S. patent application Ser. No. 10 / 358,686 entitled METHOD FOR GUN BARREL MANUFACTURE USING TAILORED AUTOFRETTAGE MANDRELS filed Feb. 5, 2003 and is incorporated by reference herein.FIELD OF THE INVENTION [0002] The present invention relates to an improved method of manufacturing a gun barrel. More particularly, the present invention relates to an autofrettage method designed for the manufacturing of liquid cooled barrels subjected to high rates of fire. BACKGROUND OF THE INVENTION [0003] For years large caliber guns have used residual stress to provide increased strength and fatigue life to the barrel. The method most often used to produce the favorable residual stress is called autofrettage which is a manufacturing process resulting in plastic deformation to the interior of the barrel. The autofrettage increases the elastic strength of the barrel, makes gross change in their resistance to fatigue and inhibits the rat...

AI Technical Summary

Benefits of technology

[0009] The present invention is a method for applying a mechanical autofrettage process to externally cooled artillery barrels. Due to the temperature distribution expected within the barrel due to the rate of fire, the autofrettage process must be limited so as to avoid bore collapse. The level of autofrettage is determined based on the yield strength of the material as compared to the acceptable stress

Problems solved by technology

The emphasis on firing rates in excess of ten rounds per minute for extended periods has complicated barrel construction.

High fire rates create a number of problems including “cook-off” of the ammunition propellant, projectile exudation, and increased tube wear.

The ability to simply include cooling features in such newly designed larger caliber barrels is not straightforward due to the tremendous pressures created within the barrel, on the order of 60,000 psi.

However, air-cooling will not support the higher firing rates.

In the case of actively cooled guns, cooling of the barrels outside diameter induces significant thermal stresses that are incompatible with the stresses induced by traditional autofrettage methods.

However, the midwall design involves greater cost and manufacturing complexity.

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