The U.S. Army uses several types of tests to increase the reliability of gun-fired munitions. Systems, subsystems, and components are gun fired to assess reliability. When failures are found, root-cause investigations are completed and parts may be redesigned. For instance, the 155 mm projectile Excalibur uses several types of tests to find failures and build reliability. Components are tested in a rail gun, a new soft-catch gun, and in soft recovery vehicles. With the rail gun, test projectiles are fired from a worn gun tube into a trough of water. The soft-catch gun, a hybrid system using both air and water, has a standard cannon tube and a series of catch tubes to stop a projectile. The third type of test, a soft recovery vehicle, uses a modified tactical Excalibur with a parachute for a soft landing. All three types of tests have on-board recorders to capture ballistic accelerations. Accelerometer data are used in failure investigations, redesign parts, and to design new projectiles. The purpose of this paper is to compare accelerations from different types of ballistic tests. Comparisons were done to determine if the tests were in the same statistical family. Comparisons are made for a United States MACS 5 charge. The maximum axial forces were the same for the soft-catch gun and the soft recovery vehicle. In the balloting directions, the rail gun and soft recovery vehicle had similar forces. The set forward forces differed in all three cases, reflecting the different catch mechanisms for the projectiles. Comparisons of g-forces were also made using shock response spectra. The shock response indicated that the damage potential is greatest for the rail gun tests, consistent with an increase rate of failures for some electronics.

Smart projectiles use electronic components such as circuit boards with integrated circuits to control guidance and fusing operations. During gun-launch, the electronics are subjected to 3-dimensional g-forces as high as 15,000 G, The U.S. Army uses finite element analysis to simulate electronics with high-g, dynamic loads. Electronics are difficult to model due to the large variation in size, from large circuit boards, to very small solder joints and solder pads. This means that to accurately model such small features would require very large models that are computationally expensive to analyze; often beyond the capability of resources available. Therefore, small features such as solder joints are often not included in the finite element models to make the models computationally tractable. The question is: what is the effect on model accuracy without these small features in the model? The purpose of this paper is to evaluate the effect that solder joints and solder pads have on the accuracy of the structural analysis of electronic components mounted on circuit boards during gun shot. Finite element models of simplified circuit boards, chips, and potting were created to do the evaluation. Modal analysis and dynamic structural analysis using typical gun loads were done. Both potting at high temperature (soft) and potting at low temperature (stiff) were used in the dynamic analysis. In the modal analysis there was no potting. All of these models were run with and without solder. In all cases, the results differed between the models with solder and those without. In the models with potting, there was a difference in magnitude and stress distribution between the models with and without solder. This indicates that there is a significant reduction in accuracy when solder is not included in the model.

an effort to produce a more secure assembly fit between the primer and the cartridge case in 5.56 mm combat ammunition, variants of the conventional case stamping tool were developed and incorporated in the small caliber ammunition manufacturing process (or SCAMP). The challenge is to develop a tool that provides a secure cartridge case-primer assembly fit while maximizing tool life. Two concept tool designs were realized-a concept four-prong triangular stamping tool and a concept four-prong wave stamping tool. This work compares the results of SCAMP trials using a concept four-prong triangular stamping tool, a concept four-ptong wave stamping tool and the conventional circular stamping tool. Comparison data include cartridge case material movement after stamping, stamping tool stress distribution, stamping tool life, and stamping forces required to achieve the objective primer seating depths. Although the SCAMP trials are still ongoing, the findings to date show that the wave stamping tool has consistently met the design challenges of improved cartridge case-primer assembly fit and maximized tool life and is currently the leading candidate for implementation in SCAMP.

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Nacre is a hierarchical multi-composite matrix consisting of mineral plate-like structures stacked up similar to brick and mortar. When impacted with a projectile this type of structure is expected to reduce the overall shock loading into the system as well as projectile velocity as a consequence of variations in structural stiffness between the composite plates and the organic interlayers. Bio-mimicked nacre derived from alumina as the base ceramic is also shown to have increased fracture toughness over an alumina monolith. One challenge to building the nacre alumina structure is the design and processing of the composite mineral plates which should be comprised of roughly 90-95% nano-filler and 5-10% organic binder. In order for these plates to accurately mimic the nacre mineral plates they must also emulate aspect ratios on the order of 1:10 to 1:20. This paper will discuss the design and processing of nacre-alumina plates for studies into the impact behavior of nacre composites.