Assessment of reliability of missile fuze using micro-CT data based finite element technique with digital volume correlation

Densely packed field extracted electrical assemblies like fuze, subjected to harsh environments may often undergo degradation in terms of material properties and physical structure (geometry), but no signs of damage may be visible from the physical appearance. Quantification of accrued damage may require cross-sectioning and thus sacrificing the sample which may be undesirable as it may not allow for any further investigation. Use of conventional finite element techniques for modeling such assemblies may be prohibitively time consuming. It has been shown earlier that the large number of components and geometric details in such assemblies make the modeling process, time consuming and results may not be accurate because of not modeling the accrued physical damage [1]. In the past, researchers have studied the reliability of such assemblies using failure rates and mean time to failure approach [2], [3]. Lall et al have used Digital Volume Correlation and micro-CT (Computed Tomography) data based finite element mesh to study remaining useful life of small sized packages like ball grid arrays [4]. No literature is found on studying reliability of large, densely packed electronics using micro-CT based noncontact type, full field deformation measurement techniques and finite element models that capture the real 'as is' geometry. In this paper, micro-CT data of the fuze has been used to perform Digital Volume Correlation, to measure deformations when the device is subjected to a thermal load. Young's modulus of the sub-components have been measured using nano-indentation, thus accounting for degradation in the material properties. Micro-CT data of a fuze has been used to create a finite element mesh which has been further used to perform a thermomechanical analysis of implicit type. Usage of micro-CT data has ensured the modeling of 'as is' geometry of the components of the fuze assembly, thus accounting for the prior accrued physical damage. The results of the finite element model are compared with the deformations measured using Digital Volume Correlation to analyze the accuracy of the FE method used for modeling fuze device.