Structural damages are often associated with under-performance of an engineering system. Hence localisation of such damages, followed by remedial measures, is the key to ensure proper functioning of the structures during their design lives. Acoustic emission (AE) technique is one of the effective non destructive evaluation (NDE) techniques for damage localisation. The present study makes an effort to review the existing literature on this technique under a few broad categories and discuss chronological advancements in each such category. The advantages and drawbacks of each method are deliberated and further scopes of research are pointed out.

Scaling transistor feature size allows greater density, higher performance and lower cost. The unrelenting pursuit of device scaling has enabled MOS gate dimensions to be reduced from IO-m in the 1970's to a present day size of 0.1-m. Conventional scaling of gate oxide thickness, source/drain extension, junction depths, and gate lengths have brought about several new technology issues invalidating some earlier methods for testing ICs. To enable testing devices into the 21'' century, new approaches are required in both test and design for testability.In this paper, we will define the problems that arise with device scaling such as Gate Oxide leakage, sub-threshold leakage, power density, electromigration, and soft error problems in qualitative and quantitative terms. The later half of the paper deals with some of the solutions being pursued at Intel.

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Structural damages generate acoustic emission (AE) in the media and cause extensional and flexural acoustic waves. Often in structures like plates, flexural mode is predominant. In this study, the flexural mode AE waveforms due to simulated damage are studied for multi-layered composite plates. A generalized refined 2D plate theory, which satisfies the transverse shear stress continuity at the layer interfaces, is proposed here for modelling the plates. This formulation is implemented through finite element method where a four-node rectangular element, that satisfies C1 continuity, is used. Plates, having different thickness ratios, are studied through numerical examples using the model. Results are validated wherever applicable and some new results are obtained. The results indicate that the proposed model can simulate the flexural waveforms realistically for ‘very thin’ to ‘moderately thick’ plates. It is also found that the present model is as accurate as 3DFEM but it possesses much better computational efficiency.