An investigation of the effects of the optical properties of surface-mount-device (SMD) light-emitting diode (LED) (side-view and top-view LEDs) packaging (PKG) components on the light extraction efficiency ηPKG using ray-tracing simulations is presented. In particular, it is found that the optical properties of the PKG resin and the lead-frame (L/F) silver-plating significantly affect ηPKG. Thus, the effects of the surface reflection methods of these components are investigated in order to optimize the optical design of the LED PKG. It is shown that there exists peak extraction efficiency for each PKG, and the cavity angle formed by the cavity wall is important to the optical design. In addition, the effect of phosphor present in the mold resin is examined using a Mie scattering simulation. Finally, an SMD LED PKG optical design method is proposed on the basis of the simulation results.
Fatigue induced damage is often progressive and gradual in nature. Structures subjected to large
number of fatigue load cycles will encounter the process of progressive crack initiation, propagation
and finally fracture. Monitoring of structural health, especially for the critical components, is therefore
essential for early detection of potential harmful crack.
Recent advent of smart materials such as piezo-impedance transducer adopting the
electromechanical impedance (EMI) technique and wave propagation technique are well proven to be
effective in incipient damage detection and characterization. Exceptional advantages such as
autonomous, real-time and online, remote monitoring may provide a cost-effective alternative to the
conventional structural health monitoring (SHM) techniques.
In this study, the main focus is to investigate the feasibility of characterizing a propagating fatigue
crack in a structure using the EMI technique as well as estimating its remaining fatigue life using the
linear elastic fracture mechanics (LEFM) approach. Uniaxial cyclic tensile load is applied on a
lab-sized aluminum beam up to failure. Progressive shift in admittance signatures measured by the
piezo-impedance transducer (PZT patch) corresponding to increase of loading cycles reflects
effectiveness of the EMI technique in tracing the process of fatigue damage progression. With the use
of LEFM, prediction of the remaining life of the structure at different cycles of loading is possible.