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Usefulness of three parameters models in engineering plasticity and sheet metal forming research
Quoc-Tuan Pham(팜쿽투완),Seok-Chul Shin(신석철),Young-Suk Kim(김영석) 한국소성가공학회 2015 금형가공 심포지엄 Vol.2015 No.8
From an overview of mechanical engineering, it is accepted that the plasticity of metals is a strongly nonlinear problem in which many nonlinear curves are required to describe important characteristics of plasticity such as flow curve, yield locus and ductile fracture. Much effort has been made to capture these characteristics by introducing many parameters to precisely express the experimental results. For example, to describe the stress-strain relation of materials, Swift and Voce models are widely used, and Hill non-quadratic and Hosford yield functions are usually applied in modeling the yield locus, because of their simple expression with only two parameters. Similarly, the most ductile failure models with a few parameters are Clift and Oyane models. However, the above-mentioned models have at most two parameters in their equations and intrinsically have limited accuracy. Of course, introduction of more parameters in plasticity models may yield more accurate solutions, such as the Barlat (2003) yield function which has eight parameters. Nevertheless, these proposed models significantly increase the computational cost and may introduce inevitable errors in estimating their parameters. To overcome this disadvantage, this study proposes three-parameter models to describe the governing equation of the above mentioned topics. These models achieve a balance between accuracy and computational cost in engineering.
Quoc Tuan Pham,김영숙 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.2
This study aims to determine the plastic deformation characteristics of aluminum 5052-O based on non-associatedflow rule. To achieve this goal, a new strain hardening model named as Kim-Tuan hardening modelis proposed to perfectly describe the stress-strain relation of the studied material in terms of the uniaxial tensiletest and to predict the material’s post-necking behavior. Additionally, the plastic behaviors of AL5052-O sheetare described by two approaches: the associated flow rule with YLD2000-2d yield function and the nonassociatedflow rule with Hill's quadratic function (NAFR-Hill48). The parameters of these functions werederived from the material properties that were obtained from uniaxial tensile tests and bulge test. The flow curvebased on Kim-Tuan model and plastic behaviors obtained from two above-mentioned approaches were importedinto a finite element analysis code to simulate the hydraulic bulge test for this material to confirm the precisionof material characteristics achieved before. The simulation results based on the NAFR-Hill48 match wellwith the experiment results of bulge test while the YLD2000-2d provides highly accurate predictions foranisotropy of this material.
APPLICATION OF A GRAPHICAL METHOD ON ESTIMATING FORMING LIMIT CURVE OF AUTOMOTIVE SHEET METALS
Quoc Tuan Pham,Jinjae Kim,The-Thanh Luyen,Duc-Toan Nguyen,김영석 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.Supp
In the automotive engineering community, the modified maximum force criterion proposed by Hora and coworkers is considered acceptable for theoretically estimating the forming limit curve (FLC) of sheet metals. Based on this criterion, a graphical method is proposed to simplify evaluation of the FLC. This paper investigates the proposed graphical method in a special case by using a power-hardening law and the Mises yield function, which leads to an explicit expression of the critical strains according the strain paths. The FLC of a DP590 sheet estimated using the proposed method is compared with that estimated using existing analytical methods. The proposed method provides the best prediction of the FLC of the tested material. For verification, the calculated FLC is then adopted into the finite-element method to predict the punch stroke at fracture of several notched specimens subjected to Nakazima tests. The good agreement between the predicted and experimentally determined values of the punch strokes verifies the ability and potential of the proposed method in industrial engineering.
Software Piracy in Vietnam: Analysis of Key Factors
Tuan, Vo-Quoc,Yoo, Chul-Woo,Kim, Mi-Suk,Choe, Young-Chan 한국경영정보학회 2007 한국경영정보학회 학술대회논문집 Vol.2007 No.-
This research focuses on the development and empirical validation of a model of software piracy behavior on the basis of deterrence theory, expected utility theory and the theory of reasoned action. The total of sample numbered 86 and PLS (Partial Least Square) was utilized for analysis. The test of this study revealed that punishment severity was the greatest significant factor to influence to software piracy and subjective norms was also significantly related to it. However punishment certainty and software cost do not significantly affect to software piracy.
Quoc-Tuan Vien,Dao-Tan-Hoang Nguyen,Le-Nam Tran,Een-Kee Hong 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
This paper proposes a new distributed space-time block code (DSTBC) over frequency selective fading channels in amplify-and-forward (AF) turbo-coded cooperative wireless relay networks with hybrid automatic repeat request (HARQ) combining schemes. The proposed DSTBC and HARQ schemes are designed to achieve spatial diversity gain and low decoding complexity. These goals are obtained by precoding the received signal at the relay to form the conventional space-time block codes. In addition, the coding gain is combined with the diversity gain to enhance the performance of DSTBC by adding turbo coding at the source and iterative decoding at the destination. Together with turbo coding, two fundamental HARQ combining schemes are considered in our design, including Chase combining (CC) and incremental redundancy (IR).
High-Frequency Interdigitated Array Electrode-Based Capacitive Biosensor for Protein Detection
Tuan Vu Quoc,Viet Nguyen Ngoc,Tung Thanh Bui,Chun-Ping Jen,Trinh Chu Duc 한국바이오칩학회 2019 BioChip Journal Vol.13 No.4
This paper reports a study on developing of a protein detection biochip based on interdigitated array electrodes (IDAEs) capacitive immunosensor. The protein after being preconcentrated in a detection region will be selectively captured and detected by the capacitive immunosensor. Using electrical impedance spectroscopy operated at high-frequency in the range of 100 kHz–1 MHz, the capacitance of the gold electrode is determined and the antibody surface modification steps can be also monitored. The experiment results show the capacitance changes in accordance with the adding biochemical layer on gold electrodes for each step of the antibody surface modification. In particular, the total impedance operated at 1 MHz frequency has been seen to change from 2.1 kΩ of bare chip (before antibody surface modification) to 8 kΩ after antibody surface modification process while the serial capacitance is recorded to reduce steadily from 450 pF to 55 pF. Also, the efficiency of protein chip was investigated by implementing the measurement of 10 µM BSA with and without preconcentration process. The measurement results have shown the sensitivity increasing significantly after the protein is preconcentrated in this chip. The results demonstrate high efficiency of protein detection can be achieved by operating high frequency capacitive measurement on IDAEs capacitive immunosensor.