Assessment of tamper-revealing ceramic seals.

摘要

The objective of the program described in this report is the development of a simple and rapidly authenticated tamper-revealing ceramic seal. This seal would resist state-of-the-art tampering, operate under severe conditions, and establish identity and integrity with one interrogation. The seal could be used, for example, on containers of various sizes, valves, or perimeter gates to establish whether tampering or entry has occurred. The feasibility of assembling a ceramic tamperproof seal with seeded defects has been established and a laboratory system for rapid ultrasonic scanning of ceramic components has been assembled. Seeded zirconia samples, two ceramic seals, and one ceramic-and-metal seal have been fabricated. The seeded zirconia samples have been ultrasonically scanned and the uniqueness of their ultrasonic fingerprints due to the presence of seeded defects has been demonstrated. Semper image-processing software has been used to correlate ultrasonic amplitude images. A linear correlation coefficient greater then 0.8 should be achievable for scans of the same seal. Shrink fitting of the connecting and binding parts has also been demonstrated to be feasible and essentially irreversible. Tests have demonstrated that a scheme for coupling ultrasonic waves to the seal can be carried out using commercially available ultrasonic gel pads. Breaking and repair of the stainless steel part of the more flexible ceramic-and-metal seal can be revealed by ultrasonic shear waves reflected from a welded joint. All problems associated with fabrication and authentication have been addressed, and the preliminary conclusion is that the concept presents no major technical difficulties.