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Microstructural Treatment of Munitions Cases to Improve Performance

Description:

TECHNOLOGY AREA(S): Weapons 

OBJECTIVE: Develop and validate technologies to cheaply alter a legacy munition’s case microstructure to improve the munition’s fragmentation performance. 

DESCRIPTION: Develop and demonstrate localized microstructure (grain size, shape, size distribution) altering processing techniques for steel (e.g. 4340, HRC and 1XXX) munitions cases that introduced localized stress concentrations equivalent to machined notch stress concentrations (1-10mm deep v-notches). Such processes cannot significantly alter the surface roughness of either the munitions case’s outer or inner diameters and be amenable to low cost scale-up for high volume manufacture. Generate mechanical (static and fatigue) property data of altered microstructural zones to assist on-wing munitions structural durability analyses of treated cases. Create and execute a design of experiments experimental/modeling test protocol. Design of experiments shall include multiple microstructural alteration severity levels and application patterns as applied to subscale cylindrical range test specimens. Exercise the resulting model to optimize the microstructural altering technique/s to government identified desired fragmentation performance. Demonstrate an optimized solution via subscale fragmentation range test (if not included in original DOE). Evaluate and document work required (plan) to apply microstructural altering technique to Mk-82, Mk-84, and Mk-86 form factors as well as estimate associated processing costs. Scale-up process to full-up munition form factor and be applied in a high volume production environment. 2) Exercise process in simulated production environment and refine production cost estimate. Treat one entire Mk-82/Mk-84/Mk-86 weapons case for Air Force range testing. 

PHASE I: Delivered products anticipated to include: A) Material and Processes report identifying microstructural altering solution, metallurgical results, associated mechanical properties, and any fragmentation modeling performed, B) Design of experiments test plan detailing all anticipated variables, levels, test specimen preparation, and range test plan. 

PHASE II: Delivered products anticipated to include: A) Range fragmentation test report, B) Response surface model, C) optimized microstructural altering treatment, D) processing technique scale-up requirements/plan. 

PHASE III: Delivered products anticipated include: A) pilot production scale refined production cost estimate and B) treated Mk-82/Mk-84/Mk-86 weapons case for Air Force testing. 

REFERENCES: 

1: Gold, V.M., Baker, E.L., Ng, K.W., Hirlinger, J.M, A Method for Predicting Fragmentation Characteristics of Natural and Preformed Explosive Fragmentation Munitions, ARWEC-TR-01007, 2001.

2:  US Army Materiel Command, Engineering Design Handbook, Warheads-General, AMCP 706-290, AMC, 1964.

3:  Johnson, C, Mosely, J.W., US Naval Weapons Laboratory, Preliminary Terminal Ballistic Handbook, Part I, Terminal Ballistic Effects, NWL Report No 1821, Defense Documentation Center for Scientific and Technical Information, 1964.

KEYWORDS: Munition, Bomb, Case, Microstructure, Fragmentation 

CONTACT(S): 

Lt Olawale B. Lawal, PhD (AFLCMC/EBE) 

(850) 882-6245 

olawale.lawal.2@us.af.mil 

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