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Dissertation
Optimization of the formability of 70:30 brass and the elimination of the wedge defect in cartridge cases
Doctor of Philosophy (Ph.D.), Drexel University
1994
DOI:
https://doi.org/10.17918/00007923
Abstract
Cartridge brass has served as a consummate model material to evaluate structure-property relationships. Compared to steel as a sheet metal for forming, brass is equal in engineering importance yet basic anisotropy, crystallographic texture and grain size relationships are unavailable. This compendium fulfills the need for mechanical property, texture and formability data for a comprehensive grain size 10 to 300 [mu]m range and processing conditions. The dissertation broadly develops the analysis of microstructure relationships through deformation for the Olsen, Swift and Fukui cup tests, and drawability of cartridge cases. Microhardness, a tenacious high resolution grid method for measuring strain, and differential scanning calorimetry were developed as quantitative procedures to assess formability. These methods significantly advance the analysis of brass and can be applied to any forming process, e.g. extrusion, forging, et al. A progressive deep-draw finite element model "DRAWNG" developed by Battelle for large ordnance artillery shells has been successfully modified for small caliber cartridge cases. Process simulation research to optimize both batch and progressive draw have been accomplished for conical dies in a double action transfer type press. The model incorporates material parameters for flow stress, work hardening, anisotropy and friction values as interface shear stress. An insidious cartridge case defect characterized by a wedge shaped slip plane has been investigated. The defects are oriented parallel to the length of the cartridge and initiate on the inside diameter as shear bands. During the high speed taper forming operation, a wedge defect is formed that exhibits a transgranular white layer that is conclusively adiabatic shear. The focus of a comprehensive deep-drawing optimization was the Small Caliber Ammunition Modernization Program (SCAMP). Two unique capabilities of the SCAMP manufacturing system are: (1) instantaneous on-line sampling at 1200 cases/minute and (2) eddy current inspection at six cartridge case locations. Statistical process optimization tests were executed to isolate the shear band formation directly with tool design, die friction and case cup metallurgy. These wedge defects were successfully eliminated by SCAMP process optimization and precise grain size control of the preform cartridge case cups.
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Details
- Title
- Optimization of the formability of 70:30 brass and the elimination of the wedge defect in cartridge cases
- Creators
- Frederick Edward Schmidt Jr.
- Contributors
- Harry C. Rogers (Advisor) - Drexel University, Materials Science and Engineering
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xviii, 311 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991021888986904721