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The model developed for stress-induced structural phase transformations of micro-crystalline silicon films

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Nano-Micro Letters 2010年第2期2卷 68-73页

作者： Chang-Fu Han Jen-Fin Lin department of mechanical engineering national cheng kung university Center for Micro/Nano Science and Technology national cheng kung university

The nanoindentations were applied to island-shaped regions with metal-induced Si crystallizations. The experimental stress-strain relationship is obtained from the load-depth profile in order to investigate the critical stresses arising at various phase transitions. The stress and strain values at various indentation depths are applied to determine the Gibbs free energy at various phases. The intersections of the Gibbs free energy lines are used to determine the possible paths of phase transitions arising at various indentation depths. All the critical contact stresses corresponding to the various phase transitions at four annealing temperatures were found to be consistent with the experimental results.

关键词： Silicon films Phase transitions Stress-strain model

Numerical Implementation of a Unified Viscoplastic Model for Considering Solder Joint Response under Board-Level Temperature Cycling

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Computer Modeling in engineering & Sciences 2021年第8期128卷 639-668页

作者： Hung-Chun Yang Tz-cheng Chiu department of mechanical engineering National Cheng Kung UniversityTainan701Taiwan

An implicit integration scheme was developed for simulating the viscoplastic constitutive behavior ofSn3.0Ag0.5Cu solder and programmed into a user material subroutine of the finite element software ANSYS. Thenumerical procedure first solves the essential state variables by using a three-level iterative procedure, and updatesthe remaining stress and state variables accordingly. The numerical implementation was applied to consider theresponses of solder joints in an electronic assembly under temperature cycling condition. The viscoplastic strainenergy density accumulation over one temperature cycle was identified as a feasible parameter for evaluating thethermomechanical reliability of the solder joints.

关键词： Pb-free hysteresis ratcheting fatigue tangent modulus

Constitutive modelling of composite laminates under uniaxial compression

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Chinese Journal of Aeronautics 2019年第4期32卷 938-947页

作者： Hsuan-Teh HU Lung-Shen KE department of Civil engineering ‘‘National" Cheng Kung University

A nonlinear constitutive model for a single lamina is proposed for the failure analysis of composite laminates. In the material model, both fiber and matrix are assumed to behave elasticplastically and the in-plane shear is assumed to behave nonlinearly with a variable shear *** damage onset for individual lamina is detected by a mixed failure criterion, composed of the Tsai-Wu criterion and the maximum stress criterion. After damage takes place within the lamina,the fiber and in-plane shear are assumed to exhibit brittle behavior, and the matrix is assumed to exhibit degrading behavior. The proposed nonlinear material model is tested against experimental data of composite laminates subjected to uniaxial compressive loads, and good agreement is obtained.

关键词： Composite laminates Constitutive model Finite element analysis Nonlinearity Uniaxial compression

Examination of DMT-based methods for evaluating the liquefaction potential of soils

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Journal of Zhejiang university-Science A(Applied Physics & engineering) 2011年第11期12卷 807-817页

作者： Gordon Tung-Chin kung Der-Her LEE Pai-Hsiang TSAI Sustainable Environment Research Center National Cheng Kung University department of Civil engineering National Cheng Kung University

The flat dilatometer test （DMT） has the potential to be a useful tool in the evaluation of liquefaction potential of soils. In practice, it is necessary to carefully examine existing DMT-based methods for evaluating liquefaction potential. We con- ducted the DMT and cone penetration test （CPT） in high liquefaction potential areas to examine the existing DMT-based methods for liquefaction potential evaluation. Specifically, the DMT and CPT were conducted side-by-side at each of six in-situ sites, and thus it is feasible to utilize those test results to validate the existing DMT-based methods. The DMT parameter, horizontal stress index （KD）, is used as an indicator for estimating liquefaction resistance of soils in terms of cyclic resistance ratio （CRR）. The analysis results revealed that the existing KD-based liquefaction evaluation methods would overestimate the CRR of soils, which leads to overestimation of the factor of safety against liquefaction. Also, the estimations of DMT-KI~ values by using the CPT-qc as well as the correlation between DMT-KD and CPT-qc proposed by the previous studies would be significantly smaller than field measurements. The results reflected that further validation of the existing DMT-based methods for liquefaction evaluation is desirable.

关键词： Liquefaction Flat dilatometer test (DMT) Horizontal stress index Earthquake

NUMERICAL SIMULATION OF SOLITARY WAVE RUN-UP AND OVER-TOPPING USING BOUSSINESQ-TYPE MODEL

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Journal of Hydrodynamics 2012年第6期24卷 899-913页

作者： TSUNG Wen-Shuo HSIAO Shih-Chun LIN Ting-Chieh department of Hydraulic and Ocean engineering National Cheng Kung University Tainan Hydraulics Laboratory National Cheng Kung University

In this article, the use of a high-order Boussinesq-type model and sets of laboratory experiments in a large scale flume of breaking solitary waves climbing up slopes with two inclinations are presented to study the shoreline behavior of breaking and non-breaking solitary waves on plane slopes. The scale effect on run-up height is briefly discussed. The model simulation capability is well validated against the available laboratory data and present experiments. Then, serial numerical tests are conducted to study the shoreline motion correlated with the effects of beach slope and wave nonlinearity for breaking and non-breaking waves. The empirical formula proposed by Hsiao et al. for predicting the maximum run-up height of a breaking solitary wave on plane slopes with a wide range of slope inclinations is confirmed to be cautious. Furthermore, solitary waves impacting and overtopping an impermeable sloping seawall at various water depths are investigated. Laboratory data of run-up height, shoreline motion, free surface elevation and overtopping discharge are presented. Comparisons of run-up, run-down, shoreline trajectory and wave overtopping discharge are made. A fairly good agreement is seen between numerical results and experimental data. It elucidates that the present depth-integrated model can be used as an efficient tool for predicting a wide spectrum of coastal problems.

关键词： Boussinesq equations solitary wave run-up shoreline scale effect overtopping

Solution Combustion Synthesis of TiO_2 and Its Use for Fabrication of Photoelectrode for Dye-sensitized Solar Cell

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Journal of Materials Science & Technology 2012年第8期28卷 713-722页

作者： Shyan-Lung Chung Ching-Mei Wang department of Chemical engineering National Cheng Kung University Advanced Optoelectronic Technology Center National Cheng Kung University

Three different types of TiO2 nano powders were synthesized by a solution combustion synthesis （SCS） method using three different fuels and for comparison, another type of Ti2 nano powder was synthesized by calcination of titanyl hydroxide. These TiO2 nano powders were used to fabricate photoelectrodes for the dye-sensitized solar cell （DSSC） and their performance was compared to that of the DSSC fabricated with Degussa P25 TiO2. The results showed that the SCS TiO2 could work well as photoelectrode for DSSC. The SCS TiO2 contained impurities of C and/or S, thus exhibiting visible light absorption and reduced band gap. The open circuit voltage and the fill factor both varied little among the various TiO2 and thus both had little effect on the photoelectrical conversion efficiency （η）. However, the variation of r/was seen to be in quite a good agreement with that of the short circuit current （Isc）, suggesting that r/was dominated by Isc. lsc was found to be enhanced by light scattering effect due to the presence of large particles but reduced by high impurity content due to an increase in electron transfer resistance. In addition, the specific surface area of the powders was found to be an important factor affecting the Isc and thus the η.

关键词： TiO2 Combustion synthesis Dye-sensitized solar cells

Numerical simulation of solidification morphologies of Cu-0.6Cr casting alloy using modified cellular automaton model

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Transactions of Nonferrous Metals Society of China 2010年第6期20卷 1072-1077页

作者： TSAI De-chang HWANG Weng-sing department of Materials Science and engineering National Cheng Kung University

The purpose of this study is to predict the morphologies in the solidification process for Cu-0.6Cr(mass fraction,%)alloy by vacuum continuous casting(VCC)and verify its accuracy by the observed experimental *** numerical simulation aspect, finite difference(FD)method and modified cellular automaton(MCA)model were used to simulate the macro-temperature field, micro-concentration field,nucleation and grain growth of Cu-0.6Cr alloy using real data from actual casting *** the observed casting experiment,the preliminary grain morphologies are the directional columnar grains by the VCC *** solidification morphologies by MCAFD model are in agreement with the result of actual casting experiment well.

关键词： Cu-Cr alloy vacuum continuous casting solidification morphology simulation modified cellular automaton model finite difference method

THREE-DIMENSIONAL NUMERICAL SIMULATION OF INTAKE MODEL WITH CROSS FLOW

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Journal of Hydrodynamics 2011年第3期23卷 314-324页

作者： HSIAO Shih-Chun department of Hydraulics and Ocean engineering national cheng kung university

The hydrodynamics of a pump sump consisting of a main channel, pump sump, and intake pipe is examined using Truchas a three-dimensional Navier-Stokes solver, with a Large Eddy Simulation （LES） turbulence model. The numerical results of streamwise velocity profiles and flow patterns are discussed and compared with experimental data of Ansar and Nakato. Fairly good agreement is obtained. Furthermore, unlike Ansar et al.＇s inviscid solution, the proposed numerical model includes the effect of fluid viscosity and considers more realistic simulation conditions. Simulation results show that viscosity affects the prediction of flow patterns and that the streamwise velocity can be better captured by including cross flow. The effects of the submergence Froude number on the free surface and streamwise velocity are also examined. The free surface significantly fluctuates at high submergence Froude number flows and the corresponding distribution of streamwise velocity profiles exhibits a trend different from that obtained for low submergence Froude number flows.

关键词： pump sump cross flow submergence Froude number Large Eddy Simulation (LES)

Adomian Decomposition Method Using Integrating Factor

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Communications in Theoretical Physics 2013年第8期60卷 159-164页

作者： Yinwei Lin Tzon-Tzer Lu Cha'o-Kuang Chen department of mechanical engineering National Cheng Kung University department of Applied Mathematics National Sun Yat-sen University

This paper proposes a new Adomian decomposition method by using integrating *** models are solved by this method to get more reliable and efficient numerical *** can also solve ordinary differential equations where th... 详细信息

关键词： Adomian decomposition integrating factor nonlinearity analytic solution Taylor series erroranalysis