GERARD KELLY BEng
PhD Research Postgraduate (2005-2008)

e: gerard.kelly@ul.ie

t: +353-61-202471

Gerard Kelly graduated from the University of Limerick in 2005 with a first-class honours degree in Mechanical Engineering. He has been awarded an IRCSET postgraduate scholarship to study at Stokes.

PhD Project Title: Impact Dynamics of Small Portable Objects

Background: Robustness under impact conditions is a critical limitation on the reliability of portable electronic systems such as mobile phones and laptop computers. In particular, stress waves in the circuit boards of such systems cause the accumulation of damage in solder interconnections and fragile elements, ultimately leading to functional failure. Impact events for such objects are notably complex, however, featuring ‘clattering’ and ‘chattering’ phenomena which give rise to highly intermittent stress conditions that are challenging to analyse. Contemporary simulation approaches – specifically finite element analysis tools – involve lengthy modelling and convergence times, and achieve limited accuracy. The response of a small portable object subject to impact is currently not well understood, and there is a clear need for representative analytical models which indicate the influence of key parameters such as geometric parameters, material properties, drop height, impact surface, and angle of impact.

The objective of the research is to analyse the response of a small portable object under impact conditions. Test vehicles representative of typical portable electronic system will be instrumented with strain gauges and miniature accelerometers, and subjected systematically to a set of drop and impact stimuli on a range of surfaces. Tri-axial accelerations will be recorded during a statistically representative set of impacts which, in conjunction with high-speed image capture, will be used to formulate a graphical technique for visualising the dynamic acceleration and strain data. Time-frequency techniques – specifically, wavelet analysis – will be applied in order to achieve filtering and to assist with the identification of frequency components. The data will be used as the basis of an analytical model for the dynamic forces within a cubic object subject to impact. Load-strength techniques will be applied in order to assist with the extraction of design rules. The anticipated outcome of the research will be a fundamental understanding of the dynamic response of a representative portable electronic product to impact stimuli.

This research is being conducted in collaboration with Prof Suresh Goyal, Distinguished Member of Technical Staff, Bell Laboratories.

Publications to date

Kelly, G., Sheehy, M., Rodgers, B., Punch, J. and Goyal, S., 2007, “Analysis of High Acceleration Shock Pulses Part I: Geometry of Incident Mass”, accepted for presentation at the Society of Experimental Mechanics Annual Conference & Exposition, Paper 95, Springfield, MA, USA, June 3-6.

Sheehy, M., Kelly, G., Rodgers, B., Punch, J. and Goyal, S., 2007, “Analysis of High Acceleration Shock Pulses Part II: Pulse Shaper Material”, accepted for presentation at the Society of Experimental Mechanics Annual Conference & Exposition, Paper 94, Springfield, MA, USA, June 3-6.

Kelly, G., Punch, J. and Goyal, S., 2006, “The Dynamics of a Small-Scale Portable Electronics Device Under Impact Stimuli”, Proceedings of the American Society of Mechanical Engineers International Mechanical Engineering Congress and Exposition, IMECE2006-14371, Chicago, IL, November.