Nam N.D.,PetroVietnam University |
Journal of Alloys and Compounds | Year: 2017
An enhancement of tensile and compressive yield strengths, ultimate tensile and compressive strengths and hardness of extruded Mg-8Gd-4Y-0.5Zr have been achieved by alloying with 2 wt.% Zn. Corrosion resistance of the extruded Mg-8Gd-4Y-0.5Zr alloy in saline solutions is also improved by alloying with 2 wt.% Zn. These enhancements could be attributed to the suppression of Mg(Gd,Y) intermetallic phases and the inducement of MgZn precipitation in the Mg matrix along with grain refinement, resulting in an improvement of mechanical properties and corrosion resistance. In addition, an interaction of Zn oxide with Mg, Gd, Y, and Zr products serve as a corrosion barrier by alloying with Zn. © 2017 Elsevier B.V.
Nguyen T.H.,Petrovietnam University |
Bae W.,Sejong University
Proceedings of the Annual Offshore Technology Conference | Year: 2016
The Cuu long basin is the largest basin in the continental offshore Viet Nam that has high potential oil and gas reserves in offshore Viet Nam. One of the biggest oil fields in the Cuu Long basin is the White Tiger at which the basement reservoir has the highest oil and gas potential production. Due to drilling several wells in the basement have been met many troubles as in high well depth, extremely hard rock of the granitic basement formation, high vibration, shock on the drilling string during drilling, leading to the short time of bit life as an increase in the cost per foot. The aim of this work is to investigate the dynamic stability by the use of a tool Swallowtail of the catastrophe theory for drilling string in a slim hole with hole size diameter of 6 1/2", 5-1/2", and 4 1/2" in the addressed basement formation. The result of the study is to select a shock sub and new properties of a bit for keeping long bit life. © 2016, Offshore Technology Conference.
Liu Z.,Guangxi University for Nationalities |
Van Loi N.,PetroVietnam University |
Obukhovskii V.,Voronezh State Pedagogical University
International Journal of Bifurcation and Chaos | Year: 2013
In this paper, by using the topological degree theory for multivalued maps and the method of guiding functions, the existence and global bifurcation for periodic solutions of a class of differential variational inequalities are studied. © World Scientific Publishing Company.
Nam N.D.,PetroVietnam University
Journal of the Electrochemical Society | Year: 2016
Mg-5Ca-xZn alloys were prepared using various zinc contents from 1 to 5 wt% for use as degradable biomaterials in medical implant applications. The influence of zinc on the corrosion properties of Mg-5Ca alloys prepared in Hanks' solution was examined using electrochemical and surface analysis techniques. The electrochemical tests reveal that the addition of zinc improves the corrosion resistance of Mg-5Ca alloys compared with untreated alloys. The improved corrosion resistance is attributed to the increased refinement of the precipitates, the grain refinement, and the continuous precipitation of Mg-Ca and MgCaZn compounds as a corrosion barrier. © 2015 The Electrochemical Society.
Van Sy L.,PetroVietnam University
Particulate Science and Technology | Year: 2016
Gas-liquid cylindrical cyclone (GLCC) separator is widely used in the petroleum industry with potential field applications. Its performance is strongly influenced by the inlet configuration. The 27° optimal inclined inlet angle has been experimentally observed for GLCC with the same diameter of body and inlet. For other GLCCs, the effect of inlet angle on flow pattern and their performances have not been investigated. The main target of the current study is to deeply understand the changes of flow pattern with respect to different inclined angles and flow conditions. Twelve GLCCs with different inclined angles were numerically investigated by using the Reynold stress turbulence model to predict the flow pattern with GLCC. The distribution of radial, axial, and tangential velocity profiles and their maximum magnitudes with respect to the change of inlet angle were carefully considered in this study. 2016 Copyright © Taylor & Francis Group, LLC
Sy L.V.,PetroVietnam University |
Nam N.T.,National Key Laboratory of Digital Control and System Engineering
Journal of Manufacturing Technology Research | Year: 2015
In this paper, the formability of magnesium alloy sheet (AZ31) is analyzed through effect of strain rate (in terms of depth step and feedrate) and temperature in a warmincremental forming process. This novel manufacturing process is utilized to produce easily the complex products from sheet materials with low cost and short setting time by using a CNC movement of non-cutting hemispherical tool. For this research, the results of the tensile tests and microstructure of AZ31 sheet at various temperatures between 25◦C and 300◦C are analyzed and discussed relative to strain rate sensitivity, ductility, strength and anisotropy. The series of incremental forming experiments with respect to the temperatures and strain rates were also carried out to identify these effects on the formability of AZ31 sheet. Their effects on the formability of incremental forming process are demonstrated and discussed. The results showed that the higher the testing temperature is set, the higher the strain at fracture is, while the influence of the strain rate is opposite. Reduction of the forming time by increasing both depth step and feedrate with respect to certain temperature can be identified. The optimum temperature of 300◦C for high value of strain rate and 250◦C for intermediate value of strain rate should be applied for warm incremental forming process. © Nova Science Publishers, Inc.
Nam N.D.,Petrovietnam University |
Vaka M.,Deakin University |
Tran Hung N.,Institute of Chemistry and Materials Science
Journal of Power Sources | Year: 2014
To gain high hardness, good thermal stability and corrosion resistance, multicomponent TiAlSiN coating has been developed using different deposition methods. In this study, the influence of Al and Si on the electrochemical properties of TiN-coated 316L stainless steel as bipolar plate (BP) materials has been investigated in simulated proton exchange membrane fuel cell environment. The deposited TiN, TiAlN and TiAlSiN possess high hardness of 23.9, 31.7, 35.0 GPa, respectively. The coating performance of the TiN coating is enhanced by Al and Si addition due to lower corrosion current density and higher Rcoating and Rct values. This result could be attributed to the formation of crystalline-refined TiN(200), which improves the surface roughness, surface resistance, corrosion performance, and decreased passive current density. © 2014 Elsevier B.V. All rights reserved.
Nam N.D.,Petrovietnam University
Journal of Magnesium and Alloys | Year: 2014
The corrosion properties of four Mg-5Al alloys with M-alloying elements (tin, manganese and zinc) in a 3.5 wt.% NaCl solution were examined using electrochemical tests and surface analyses. The electrochemical results indicated that the addition of 1 wt.% M metal decreased the corrosion rate and hydrogen evolution rate of the Mg-5Al specimens. Moreover, the addition of 1Zn resulted in having the best corrosion resistance due to the interaction of Zn oxide with Mg and Al oxides which acted as a corrosion barrier. © 2014 National Engineering Research Center for Magnesium Alloys of China, Chongqing University.
Nguyen T.P.N.,French National Center for Scientific Research |
Nguyen T.P.N.,CNRS Institute of Electronics, Microelectronics and Nanotechnology |
Nguyen T.P.N.,PetroVietnam University |
Boukherroub R.,French National Center for Scientific Research |
And 2 more authors.
Journal of Colloid and Interface Science | Year: 2014
We report on the fabrication of silicon nanostructured superhydrophobic and superoleophobic surfaces also called "superomniphobic" surfaces. For this purpose, silicon interfaces with different surface morphologies, single or double scale structuration, were investigated. These structured surfaces were chemically treated with perfluorodecyltrichlorosilane (PFTS), a low surface energy molecule. The morphology of the resulting surfaces was characterized using scanning electron microscopy (SEM). Their wetting properties: static contact angle (CA) and contact angle hysteresis (CAH) were investigated using liquids of various surface tensions. Despite that we found that all the different morphologies display a superhydrophobic character (CA > 150° for water) and superoleophobic behavior (CA. ≈. 140° for hexadecane), values of hysteresis are strongly dependent on the liquid surface tension and surface morphology. The best surface described in this study was composed of a dual scale texturation i.e. silicon micropillars covered by silicon nanowires. Indeed, this surface displayed high static contact angles and low hysteresis for all tested liquids. © 2013 Elsevier Inc.
Sy L.V.,PetroVietnam University
Lecture Notes in Electrical Engineering | Year: 2016
Incremental sheet forming (ISF) is an innovative die-less technique for forming the product from sheet materials. This process has been attracted a considerable interest of the scientific community due to its high formability, flexibility, short lead-time and inexpensive equipment. However, applicability of this process in practices is limited by anticipating mechanical failures during the forming process. This paper presents implementing a developing fracture model into finite element simulation to predict the occurrence of fracture in forming a cone shape. The works were begun by analyzing material properties, choosing fracture criteria, and implementing into ABAQUS environment. Finally, the simulated results were validated by one of practical experiments in aspects of, for instance, geometric accuracy and formability. They showed an excellent agreement between the simulated work and the experiment conducted in this study. © Springer International Publishing Switzerland 2016.