Modeling of Ordnance-Induced Pyrotechnic Shock Testing
Design of an ordnance-induced pyrotechnic shock test to meet a specific acceleration based Shock Response Spectrum (SRS) test requirement for a given test article has traditionally been an empirical process. Based on experience, the test engineer will determine a potential test configuration and then, through a trial-and-error process, modify the test parameters and configuration until acceptable SRS levels have been achieved. As a complement to this approach, National Technical Systems (NTS) has developed an explicit finite element based modeling approach to simulate an ordnance-induced pyrotechnic shock test. This tool may be used to assist with test configuration design for particularly challenging test requirements or to streamline the process of arriving at acceptable test levels during the calibration phase of a test program.
Development of a miniature point source pyroshock simulator
Abstract Pyrotechnic devices have been widely utilized in various applications: spacecraft, launch vehicles, missiles, and aircraft as well as for stage separation, valve control, and booster separation. However, most pyrotechnic separators generate an intensive mechanical transient response called pyroshock, which can cause catastrophic failures in electronic equipment. In order to validate that the structure or equipment can withstand the generated shock level, pyroshock tests should be performed with properly simulated structural configurations and the shock sources. Most of the previous pyroshock simulators using mechanical excitation have been developed as shock table configurations; they can effectively apply the target shock levels to the test component. However, it is difficult to simulate the pyroshock source in practical structures. In this study, a miniature pyroshock simulator that can easily replace a pyrotechnic device and is adaptable onto the most practical structures was developed. A disk resonator is introduced to control the shock response by changing the first natural frequency of the disk resonator. To excite the disk resonator, we devised a launch device that effectively controls the impact velocity with easy reloading capability. Experiments for 27 different conditions were conducted to identify the control parameters for the shock levels. The developed simulator also showed high repeatability, and it is easy to prepare repeated experiments using the developed shock simulator. This device can easily generate the simulated point-source pyroshock for real structures such as an assembled spacecraft.
Scaffolds Containing Spirulina sp. LEB 18 Biomass: Development, Characterization and Evaluation of In Vitro Biodegradation.
Polymer nanofibers are nanomaterials that can be used as scaffolds in tissue engineering. The objective of this study was to develop, characterize and evaluate the in vitro degradation of a biomaterial consisting of nanofibers produced from biodegradable and biocompatible polymers with potential applications as a scaffold for tissue regeneration and containing Spirulina sp. LEB 18 biomass as the bioactive compound. The polymers used were poly(hydroxybutyrate-co-hydroxyvalerate) and polycaprolactone. The polymeric solutions exhibited sufficiently high viscosity to produce uniform nanofibers with diameters between 335 and 617 nm. The applied conditions were as follows: a voltage of 25 kV, a distance from the capillary to the collector of 120 mm, a capillary diameter of 0.80 mm, and 12% polycaprolactone and a blend of 5% polycaprolactone and 10% poly(hydroxybutyrate-co-hydroxyvalerate). The biomass was incorporated into the nanofibers at a concentration of 3%, and the incorporation was confirmed using confocal microscopy. The nanofibers were characterized using differential scanning calorimetry and thermogravimetric analysis, which showed that the addition of biomass did not alter the thermal properties of the biomaterial. The addition of biomass improved the tensile strength and elongation of the scaffolds compared with those produced with polymers alone. A biodegradation assay showed enzymatic action toward the biomaterial, simulating the behavior of natural tissue. Based on the analysis, it was concluded that the scaffolds that were produced have the potential to be applied in the field of tissue regeneration as biomaterials with pharmacological properties.