Rajdeep Sharma

Hierarchical Life Prediction Model for Actively Cooled LED-Based Luminaire

The lifetime of an actively-cooled light emitting diode (LED)-based luminaire is dependent not only on the junction temperature of LEDs, but also on the reliability of active cooling devices. We propose a novel hierarchical model to assess the lifetime of an actively cooled LED-based luminaire that can provide light output equivalent to a 100 W incandescent lamp. After design considerations for LED-based luminaires with active cooling are discussed, the proposed model is described using component-level sub-physics-of-failure models. The model is implemented to predict the lifetime of a LED-based recessed downlight with synthetic jet cooling. The effects of the time-dependent performance degradation mechanisms of the active cooling device on the lifetime of the luminaire are also discussed.

Development of a High-Lumen Solid State Down Light Application

Light-emitting diode (LED)-based solid-state lighting (SSL) products have been exceeding the predicted performances especially at the chip and package levels. This has led to new SSL-based products for energy savings and long lifetimes. Large amounts of government funding and private investments have been made during the last decade to accelerate and guide the technology. This paper focuses on the development of an LED-based high-lumen luminaire technology. The critical subcomponents of the luminaire are the LED light engine (LED chips and optical system), thermal management, and driver electronics. Each of these subcomponents will be discussed in detail for a 100 W incandescent replacement technology. The paper addresses system integration of each of the subcomponents. While the design of new products evolve, the lack of reliability data poses a risk of premature failure of LED-based products. Premature failures would trigger customer rejection and may delay market penetration. Therefore, luminaire reliability is an important aspect of luminaire design. In cohort with this notion, finally, the luminaire reliability has been discussed.

Hierarchical Reliability Model for Life Prediction of Actively Cooled LED-Based Luminaire

The interest in light-emitting diodes (LEDs) for illumination applications has been increasing continuously over the last decade due to two key attributes of long lifetime and low energy consumption compared to the conventional incandescent light and compact fluorescent light. Although LEDs are attractive for lighting applications due to the aforementioned advantages, unique technical challenges, such as the extreme sensitivity of luminous output and useful lifetime to LED junction temperature, need to be overcome for their large-scale commercialization.

Modeling Ductile/Brittle Behavior in Polymeric Microlaminates: Effect of Volume Fraction

In this work we present a micromechanical model for two-phase ductile/brittle laminates that captures the macroscopic behavior, as well as the underlying micro-mechanisms of deformation and failure, in particular the synergy between the inelastic deformation mechanisms of crazing and shear yielding. The finite element implementation of our model considers a three-dimensional representative volume element (RVE), and incorporates continuum-based physics-inspired descriptions of shear yielding and crazing, along with failure criteria for the ductile and brittle layers. The interface between the ductile and brittle layers is assumed to be perfectly bonded. The model successfully explains the volume fraction effect on the micro and macromechanics of ductile/brittle microlaminates subjected to uniaxial tension.