Aixi Zhou

A Study of Accelerated Life Test of White OLED Based on Maximum Likelihood Estimation Using Lognormal Distribution

In this paper, accelerated life tests of white organic light-emitting diodes (WOLEDs) are conducted to obtain failure data at normal operation conditions. The lognormal distribution function was applied to describe WOLED life distribution. Log mean and log standard deviation were determined by maximum likelihood estimation. The Kolmogorov-Smirnov test was performed, and the results further confirmed that WOLED life met the lognormal distribution. Numerical results indicated that WOLED life followed the lognormal distribution. It was also found that the acceleration model was consistent with inverse power law.

Analysis of Nonlinear Dynamic Response of Wind Turbine Blade Under Fluid–Structure Interaction and Turbulence Effect

In this paper, the entity model of a 1.5 MW offshore wind turbine blade was built by Pro/Engineer software. Fluid flow control equations described by arbitrary Lagrange–Euler (ALE) were established, and the theoretical model of geometrically nonlinear vibration characteristics under fluid–structure interaction (FSI) was given. The simulation of offshore turbulent wind speed was achieved by programming in Matlab. The brandish displacement, the Mises stress distribution and nonlinear dynamic response curves were obtained. Furthermore, the influence of turbulence and FSI on blade dynamic characteristics was studied. The results show that the response curves of maximum brandish displacement and maximum Mises stress present the attenuation trends. The region of the maximum displacement and maximum stress and their variations at different blade positions are revealed. It was shown that the contribution of turbulence effect (TE) on displacement and stress is smaller than that of the FSI effect, and its extent of contribution is related to the relative span length. In addition, it was concluded that the simulation considering bidirectional FSI (BFSI) can reflect the vibration characteristics of wind turbine blades more accurately.

Validating Thermal Response Models Using Bench-Scale and Intermediate-Scale Fire Experiment Data

The thermal response of a fiber reinforced polymer composite was measured by the bench-scale Cone Calorimeter and Intermediate-scale Calorimeter (ICAL) fire experiments. Finite-rate and infinite-rate pyrolysis models were used to predict the response of the composite panels under the same thermal boundary conditions as in the fire tests. It was shown that both models can give acceptable temperature, mass loss, and effective char thickness predictions. The effect of internal gas convection on thermal response predictions was determined insignificant at low heat flux levels. The thermal insulation at the back surface of the composite panel significantly increased both temperature and mass loss predictions.

Fiber Reinforced Polymer Composite Structures in Fire: Modeling and Validation

This article presents a thermomechanical model for predicting the behavior of fiber reinforced polymer (FRP) composite structures subject to simultaneous fire and compressive loading. The model includes a thermal sub-model to calculate the temperature history of the structure and a structural sub-model to predict the mechanical performance of the structure. Both thermal and mechanical properties in the two sub-models are temperature dependent. The effect of heating rate on decomposition is considered through a shift temperature factor in the thermal sub-model. Cohesive elements are incorporated in the structural sub-model to consider the effect of delamination for sandwich panels. The model is implemented by the finite element method and is validated by comparing the numerical results with a one-sided heating test on FRP laminate strips and furnace structural fire tests on FRP laminate and sandwich panels.

White OLED Weibull Life Prediction Using Maximum Likelihood Estimation

A theoretical model using Weibull distribution and maximum likelihood estimation (MLE) was established to statistically analyze the test data, which were obtained by three groups of constant stress accelerated life tests. The life prediction software was applied to simplify the calculation and achieve organic light-emitting device (OLED) life estimation. The results indicate that the Weibull distribution is fit to describe white OLED life, and the precise accelerated parameter β is particularly useful to predict the white OLED life within a shorter time, which provides significant guidelines to help engineers make decisions in design and manufacturing strategy from the aspect of reliability life.

Finite Element Modeling of Mode I Failure of the Single Contoured Cantilever CFRP-Reinforced Concrete Beam

The single contour cantilever beam (SCCB) test method has been developed with the intent to capture Mode I opening failures of CFRP-reinforced concrete beams. Recent development in the method explores possible shifting damage into the concrete substrate by using the International Concrete Repair Institute (ICRI) Surface Profile Level Three (SP3) as the desired CFRP bonded interface to concrete. To validate and explain the interface fracture behavior, finite element analysis using special cohesive elements has been performed. The cohesive element allows separation of the concrete substrate from the CFRP. This paper presents the simulation of laboratory test results, where failure in the substrates has been successfully reproduced. The simulation results indicate that finite element method using cohesive elements can successfully replicate Mode I critical strain energy release rate and the peak capacity of the laboratory tests and may have the potential to simulate actual applications.

Study on constant–step stress accelerated life tests in white organic light-emitting diodes

In order to obtain reliability information for a white organic light-emitting diode (OLED), two constant and one step stress tests were conducted with its working current increased. The Weibull function was applied to describe the OLED life distribution, and the maximum likelihood estimation (MLE) and its iterative flow chart were used to calculate shape and scale parameters. Furthermore, the accelerated life equation was determined using the least squares method, a Kolmogorov-Smirnov test was performed to assess if the white OLED life follows a Weibull distribution, and self-developed software was used to predict the average and the median lifetimes of the OLED. The numerical results indicate that white OLED life conforms to a Weibull distribution, and that the accelerated life equation completely satisfies the inverse power law. The estimated life of a white OLED may provide significant guidelines for its manufacturers and customers.

Influences of gas velocity and particle distribution on PM10 collection in wire-plate ESP under diffusion charging mechanisms

To study the PM10 collection in a wire-plate ESP, a numerical model was built and performed by FLUENT software. Deutsch-Anderson Equation was subsequently applied to collection efficiency calculation. The numerical results under different gas velocities at inlet and particle distributions indicate that the collection efficiency of PM10 increases with a decrease in gas velocity, and that the increment of grade efficiency will become bigger if particle diameter gets smaller. By comparing with a decrease in gas velocity, diffusion charging mechanism is found to be valuable for PM10 in aspect of collection. As two parameters of Rosin-Rammler distribution decrease, grade efficiency will increase, especially for fine particles, and a larger positive effect the diffusion charging mechanism will have on collection efficiency, but overall efficiency will decrease. Finally, the effect of particle distributions on grade efficiency is much smaller than that of diffusion charging mechanism or the gas velocity at inlet.