Analysis of Progressive Damage in Fuze Electronics using Micro-Computed Tomography and Finite Element Models

Electronics assemblies used in fuzing applications are often potted, thus eliminating the possibility of visual inspection of the assemblies to allow for assessment of accrued damage and the ability to function without faults during mission life. The long storage life in addition to the harsh operational loads makes the study of fuzing applications very challenging. There may be material and dimensional variations in the potted fuze electronics part-to-part. Thus, modeling with nominal design dimensions may not be representative of the specific fuze assembly of interest. There is need for tools and techniques for the non-destructive assessment of the fuze electronics. Electronic fuze assemblies may be exposed to harsh environments during prolonged storage, transport and deployment. Under exposure to storage-transport environmental loads including mechanical shock, temperature, vibration and humidity the fuze assemblies may sustain damage without any surface signs of visible degradation. Further, the operational environment requires survivability under high-g loads often in excess of 10,000g. The need for non-destructive test methods to allow for determination of the internal damage and the assessment of expected operational reliability under the presence of accrued damage from prolonged storage is extremely desirable. While a number of non-destructive test methods such as x-ray, and acoustic imaging exist in the state-of-art - they are limited to the acquisition of imaging of the internal damage state without the ability of conducting measurement of deformation under the action of environment loads. In this paper, progressive damage in fuze assembly FMU143 has been measured using MicroCT based DVC. In addition, FE models of the fuze assemblies with accrued damage have been developed based on x-ray micro-computed tomography DICOM data. Deformations in the fuze assembly have been measured under a thermal load. DVC is used to measure the deformations at different locations while the part is under a thermal load. A detailed account of DVC calibration and experimentation has been given. The procedure to convert the micro-CT data into a FE mesh has been described briefly. The material properties of some of the main parts in the fuze have been found to account for the possible degradation. The results from the DVC and the finite element analysis have been compared.