An analytical model was developed to understand the physics and predict the functional performance of a pin puller. The formulated model is based on one-dimensional gas dynamics for an ideal gas. Resistive forces against pin shaft movement were measured in quasi-static mechanical tests, the results of which were incorporated into the model. The expansion chamber pressure and the pin shaft displacement were measured from an actual firing test and compared to the model prediction. The gas generation rate was adjusted by a correction factor, and the heat transfer rate was obtained through parametric analysis. The validity of the model is assessed for additional firing tests with different amounts of pyrotechnic charge. This model can provide knowledge on how the pin puller functions, and on which design parameters contribute the most to the actuation of the pin puller. Using this model, we estimate the functional safety factor by comparing the energy generated by the pyrotechnic charge to the energy required to accomplish the function.
A parametric study based on an unsteady mathematical model of a pyrotechnically actuated device was performed for design optimization. The model simulates time histories for the chamber pressure, temperature, mass transfer and pin motion. It is validated through a comparison with experimentally measured pressure and pin displacement. Parametric analyses were conducted to observe the detailed effects of the design parameters using a validated performance analysis code. The detailed effects of the design variables on the performance were evaluated using the one-at-a-time (OAT) method, while the scatter plot method was used to evaluate relative sensitivity. Finally, the design optimization was conducted by employing a genetic algorithm (GA). Six major design parameters for the GA were chosen based on the results of the sensitivity analysis. A fitness function was suggested, which included the following targets: minimum explosive mass for the uniform ignition (small deviation), light casing weight, short operational time, allowable pyrotechnic shock force and finally the designated pin kinetic energy. The propellant mass and cross-sectional area were the first and the second most sensitive parameters, which significantly affected the pin's kinetic energy. Even though the peak chamber pressure decreased, the pin kinetic energy maintained its designated value because the widened pin cross-sectional area induced enough force at low pressure.
This paper reports a low-g MEMS acceleration switch with threshold acceleration below 10 g. The proposed switch is made of single-crystalline silicon for high thermal stability and stressfree structure. A vertical operation type is adopted to enable fine control of the contact surface during the fabrication process. The switch contains displacement-restricting structures in all directions for impact resistance and is packaged with anodic bonding process. The fabricated switches had an average proof mass, initial gap, and spring constant of 307.38 µg, 6.39 µm, and 3.29 N m −1 , respectively. Height profile of the free-hanging proof mass was measured to show that the switch does not suffer from stress problems. In the electrostatic operation test, the contact resistance of the switch was varied with contact force and the minimum value was estimated to be 8.5 Ω. The response time of the switch was measured to be shorter than 1.2 ms. The fabricated switch operated more than 10 000 cycles without failure. For the thermal stability test, the switch was heated at 80 °C for 6 h and the switch operated successfully over 200 times. In the rotation-table experiment, the switch operated at 6.61 g and error analysis was carried out in the consideration of tangential force generated during the rotation-table experiment. From the experimental values, the tangential force was calculated as 2.375 µN and the resulting reduction in the initial switching gap was simulated as 0.32 µm. The reduced threshold acceleration thus was estimated to be 6.62 g, which agrees very well with the measured threshold acceleration value of 6.61 g.
A pyrotechnic device that consists of a donor/acceptor pair separated by a gap or a bulkhead relies on the shock attenuation characteristics of the gap material and the shock sensitivity of the donor and acceptor explosives. In this study, a miniaturized exploding foil initiator, based on high pulsed electrical power generator, was designed to launch a micro Kapton® flyer for impact initiation of a high explosive in order to understand its performance characteristics. Here, the explosive substance was replaced with a witness plate because the flyer poses various flight motions of rotation, bend, and fragmentation due to its extreme thinness. By using a Velocity Interferometer System for Any Reflector and ANSYS Explicit Dynamics, the averaged velocity of a flyer is measured, which then allows for the calculation of the shock pressure and the duration imparted to the explosive for an initiation. Subsequently, the relationship between the flyer velocity, the amplitude, and the width of impact loading can be used to assess the performance of the designed exploding foil initiator of a micro pyro-mechanical device.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.