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Williard N.,Center for Advanced Life Cycle Engineering | Williard N.,Schlumberger | Baek D.,Korea Institute of Machinery and Materials | Park J.W.,Korea Institute of Machinery and Materials | And 3 more authors.
IEEE Transactions on Device and Materials Reliability | Year: 2015

Supercapacitors provide high-power energy storage for electrical systems. The expected useful life of a supercapacitor is related to the oxidation of functional groups on the graphite electrode surface during usage, and it is highly dependent on operational voltage and temperature. In this paper, a life model is developed for commercial supercapacitors. The model incorporates a new voltage multiplier to describe the combined effects of temperature and voltage on supercapacitor life. Accelerated testing was conducted to obtain the time to failure of supercapacitors over a range of voltage and temperature conditions, validate the life model, and compare the model with two previously established capacitor life models. Failure was defined by a 30% decrease in capacitance or a 100% increase in equivalent series resistance. © 2001-2011 IEEE.

Han S.,Center for Advanced Life Cycle Engineering | Osterman M.,Center for Advanced Life Cycle Engineering | Pecht M.,Center for Advanced Life Cycle Engineering
SMT Surface Mount Technology Magazine | Year: 2012

For electronic equipment, tin whisker growth can produce unintended electrical shorts resulting in product failure. Under certain conditions, tin whiskers can initiate a metal vapor arc that can have destructive consequences. This study investigates the role of bias voltage, pressure, and whisker geometry on metal vapor arc formation, and presents a metric for whisker arc formation.

Srinivas V.,Center for Advanced Life Cycle Engineering | Osterman M.,Center for Advanced Life Cycle Engineering | Al-Bassyiouni M.,Center for Advanced Life Cycle Engineering | Pecht M.,Center for Advanced Life Cycle Engineering
ASME International Mechanical Engineering Congress and Exposition, Proceedings | Year: 2010

Mechanical torsion loads often arise in portable electronics under life cycle conditions. With increased market pressure, drive to reduce time to market, and varying use conditions, it is critical to develop accelerated tests to evaluate reliability quickly. Mechanical torsion testing can provide a rapid assessment technique to characterize solder interconnect durability. This paper presents an evaluation of select lead-free solders, SAC305 (96.5Sn-3.0Ag-0.5Cu) and SN100C (99.25Sn-0.7Cu-0.05Ni+Ge), under mechanical torsion loading. For comparison, SnPb (63Sn-37Pb) solder was also evaluated. Common test vehicles with resistor 2512 packages were used for these tests. For the mechanical cycle tests, no statistical difference in reliability was observed between SAC305 and SnPb solder paste while SN100C solder pastes were found to exhibit lower durability during Weibull analysis. Copyright © 2010 by ASME.

Haddad G.,Center for Advanced Life Cycle Engineering | Sandborn P.,Center for Advanced Life Cycle Engineering | Pecht M.,Center for Advanced Life Cycle Engineering
Technical Program for MFPT: The Applied Systems Health Management Conference 2011: Enabling Sustainable Systems | Year: 2011

This paper provides an optimization model based on Real Options (RO) and stochastic dynamic programming for the availability maximization of an offshore wind farm with prognostic capabilities. Alternative energy sources such as offshore wind turbines are promising technologies, but they are capital intensive projects, and the economics of the project depend heavily on the wind resources, and the availability of the turbines. Prognostics and health management (PHM) is an enabling technology that potentially allows for reduced life cycle cost through a transition from cycle or time based to demand-based maintenance, performance based logistics, and condition-based maintenance. This is especially important for offshore wind farms that require non-traditional resources for maintenance, and are often located in sites that are not always accessible. The proposed model uses information from the PHM system in order to allocate appropriate investments in maintenance while maintaining a specified availability requirement. The RO theory provides promising means to address the economic aspects of PHM after prognostic indication, and assessing the cost required for meeting availability requirements.

Williard N.,Center for Advanced Life Cycle Engineering | He W.,Center for Advanced Life Cycle Engineering | Osterman M.,Center for Advanced Life Cycle Engineering | Pecht M.,Center for Advanced Life Cycle Engineering
International Journal of Prognostics and Health Management | Year: 2013

Traditionally, capacity and resistance have been used as the features to determine the state of health of lithium-ion batteries. In the present study, two additional features, the length of time of the constant current and the constant voltage phases of charging were used as additional indicators of state of health. To compare the appropriateness of each state of health feature, batteries were subjected to different discharge profiles and tested to failure. For each cycle, capacity, resistance, length of the constant current charge time and length of the constant voltage charge time were measured and compared based on their usefulness to estimate the state of health. Lastly, all the features were combined to give a fusion result for state of health estimation.

Huang H.,Center for Advanced Life Cycle Engineering | Dasgupta A.,Center for Advanced Life Cycle Engineering | Mirbagheri E.,Microsoft
2016 17th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2016 | Year: 2016

The focus of this paper is on a modeling methodology for capturing the complex mechanical behavior of a single layer pressure-sensitive adhesive (PSA) system, based on empirical observations of its stress-strain behavior. This study is motivated by the fact that there is very limited modeling ability to mechanistically predict the bimodal stress-strain curves of single-layer PSAs. Empirical observations verify that this behavior is due to softening caused by nucleation and growth of cavities in the early deformation stage and hardening due to fibrillation during the final deformation stage before terminal debonding from the substrate. The effects of different loading conditions, including loading rate, stress and temperature, on PSA systems are also important. In-depth physics-based understanding of the connection between morphological changes in the joint and mechanical performance (including relevant failure mechanisms) of PSA-bonded assemblies will help to optimize PSA materials and joint architecture for maximum performance and durability. The goal of the mechanical modeling capability proposed in this study is to enable a virtual testing capability with reasonably high fidelity. The proposed modeling approach builds on an existing 'block model' methodology [1] and improves the existing approach by modeling each block with a strain-hardening viscoelastic constitutive model to capture the fibrillation process. Results show reasonable agreement between this improved mechanistic 'block model' and experiments. Such a mechanistic model can now be used as a virtual-testing tool, to explore how these PSA systems will behave on different substrates under different loading conditions. © 2016 IEEE.

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