Date of Award

2011

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Department

Electronic Engineering

First Advisor

Dr. John Barrett

Abstract

Sensing systems for reliability prognostics are used extensively in life- and mission- critical electronics systems. They allow monitoring of reliability stresses in real time and scheduling of preventative maintenance before system failure. However, reliability prognostics systems are, in general, large and expensive and cannot be used in lower cost, small sized or portable products.

This thesis presents a sensing module for reliability prognostics which is only 1cm in volume and uses only commercial off-the-shelf components. In its 1cm package, the module combines all the necessary elements to act as an embedded prognostic sensor system for multi axial strain, vibration, humidity and temperature monitoring. The system consists of microcontroller, sensors, data storage, signal conditioning and communications interface in a single package. The module takes a cube form factor that is created using a new and innovative three dimensional packaging technique that was also developed, under the National Access Programme in the Tyndall National Institute, as part of this thesis work. The module can measure 3D strain, 3D temperature, low- level tri-axial shock and vibration as well as humidity at the point it is located. The use of commercial-off-the-shelf components throughout the module and its modular design mean that the system can be readily customised in terms of both size and functionality, a major advantage over approaches which use custom-designed test chips.

The module was subjected to a range of stress tests for both calibration and characterisation. Mechanical testing of “dog-bone” encapsulated test specimens verified that the direction and magnitude of all components of 3D strain could be resolved with a correlation on average of better than 10% with finite element analysis results when subjected to tensile and compressive loads. Climatic test results verify the systems functionality over the range of 0 to 85 degrees Celsius as well as providing data for calibration of the device. Vibration testing verifies the modules use as a mechanical shock and vibration sensor.

The module is small and modular enough that it can be used in applications such as structural health monitoring and reliability prognostics and for calibration of mechanical/ thermomechanical simulations.

Access Level

info:eu-repo/semantics/openAccess

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