A novel Micro-CT data based Finite Element Modeling technique to study reliability of densely packed fuze assemblies

Abstract

Densely packed electrical assemblies like fuze, contain large number of components, potted in protective adhesives. The number of components, varying material types, irregular geometry of the components and the geometric details of the assembly makes conventional CAD modeling, meshing and Finite Element(FE) modeling of these large assemblies extremely time consuming, often, to the extent of being impractical. CAD geometries compatible with modern Finite Element (FE) platforms may not be available for several legacy systems. Furthermore, conventional CAD modeling may not account for the real geometry realized after the manufacturing process and this can often affect the fidelity of the FE model. There is no method for capturing the actual assembly geometry and its embedded components. Assessment of survivability of fuzes requires assessment of stresses and strains under operational loads. Previously, researchers have studied the reliability of key components in a fuze device subjected to high temperature and high g mechanical shocks [1]. Researchers have measured redundancy and reliability of fuze electronics using failure rates and mean time to failure as per MIL-HDBK-217F standard [2]. There is little to no literature on FE modeling of a comprehensive fuze assembly. In this paper, a methodology for the creation of an FE model based on Micro-CT (Computed Tomography) data is presented. The method has been applied to an actual fuze subjected to mechanical shock. This method involves usage of advanced 3D imaging, image segmentation, image filtering and meshing techniques to directly convert CT scanned electrical assemblies into a FE mesh. This method successfully bypasses the time consuming CAD modeling step of conventional FE modeling. The as-is geometry of each component, positioned accurately in a 3D space, as per the original assembly, has been realized in this process by usage of micro-CT scanning technique. The submicron scale tolerances of the CT scanned data ensure true representation of the fuze assembly, in this case. The FE model thus realized, allows for measurement of all the field variables, anywhere over its meshed domain. Stress and strain histories have been extracted for embedded components of the fuze assembly using explicit finite element models.