CSRIO Materials Science and Engineering

Japan

CSRIO Materials Science and Engineering

Japan

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Kodama S.,Nippon Steel & Sumitomo Metal Corporation | Sugiura K.,Osaka University | Nakanishi S.,Osaka University | Tsujimura Y.,Osaka University | And 2 more authors.
Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society | Year: 2013

In order to clarify the mechanism of metal vapor generation in helium (He) gas tungsten arc plasma, the phenomenon of heat transfer between the plasma and the base metal was examined. In addition to the argon (Ar) arc and He arc, the numerical analyses of imaginary arcs changing the thermal conductivities of respective arcs were conducted, and the plasma temperatures, molten pool temperatures, and the concentrations of metal vapor were compared. As a result, with the increase of the thermal conductivity of the plasma, the maximum temperature of the molten pool surface and the maximum iron (Fe) vapor concentration went up while the plasma temperature in the vicinity of the molten pool dropped. Therefore it is assumed that the phenomenon of Fe vapor generation in the He arc and the phenomenon of the plasma temperature drop near the molten pool are influenced greatly by the high thermal conductivity of the He plasma.


Sugiura K.,Osaka University | Kodama S.,Nippon Steel & Sumitomo Metal Corporation | Tsujimura Y.,Osaka University | Murphy A.B.,CSRIO Materials Science and Engineering | Tanaka M.,Osaka University
Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society | Year: 2013

It is problem that nitrogen absorption in gas tungsten arc (GTA) weld metal. Recently, various arc welding simulation techniques have been developed. However, there are few models dealing with the absorption and a mixture of a shielding gas, an atmosphere and a metal vapor.. In this study, intruding behaviors of the atmospheric gas (N2) into the molten poor and nitrogen transportation phenomenon in the molten poor during GTA welding was investigated using a unified numerical model. This model includes the tungsten cathode, arc plasma and base metal. We take atmosphere (N2), shielding gas from the gas nozzle and metal vapor from the molten poor into consideration. As a result, we show nitrogen concentration distribution and nitrogen transportation in the molten poor. Additionally, we clarify that these behaviors are affected by the arc plasma characteristics.


Nakanishi S.,Osaka University | Tsujimura Y.,Osaka University | Kodama S.,Nippon Steel & Sumitomo Metal Corporation | Murphy A.B.,CSRIO Materials Science and Engineering | Tanaka M.,Osaka University
Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society | Year: 2013

This study shows the time variation of temperature distribution and concentration distribution of metal vapor during gas tungsten arc welding. In this study, stationary gas tungsten arc welding of pure iron was conducted in helium as shielding gas. We investigated the influence of iron vapor on arc plasma and mechanism of iron vapor transportation from the weld pool into the arc plasma. We observed the arc plasma two-dimensionally with spectrometric method. We captured three different monochromatic images simultaneously by three monochromators with high speed video cameras. Thus, two inherence spectra of iron and also one inherence spectrum of helium in arc plasma were obtained. Using these spectra, plasma temperature distribution was obtained. In addition, concentration distribution of iron vapor was obtained by measuring electron density. It was concluded that plasma temperature decreased with increase of iron vapor concentration. Especially, the metal vapor concentration indicated the highest value near the base metal and the temperature around the weld pool decreased rapidly.


Tsujimura Y.,Osaka University | Nakanishi S.,Osaka University | Kodama S.,Nippon Steel & Sumitomo Metal Corporation | Murphy A.B.,CSRIO Materials Science and Engineering | Tanaka M.,Osaka University
Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society | Year: 2013

In this study, plasma diagnostics in MIG welding of aluminum is performed. In MIG welding, the metal vapor has the large influences on the welding process since the content of the metal vapor in the arc plasma is large. The distribution of metal vapor varies dynamically by a metal transfer. Therefore, the dynamical distributions of temperature and concentration of metal vapor are obtained by the spectral images pictured by high-speed video cameras. Consequently, the metal vapor is distributed near the center axis and the temperature of the arc plasma decreases. Finally, we discuss plasma physics in the welding arc through numerical simulations, using the basic conservation equations of mass, energy, momentum, current and electron density of plasma physics. There is close interaction between the electrode, the arc plasma, the weld pool, and also the metal vapor, which constitute the welding process, and must be considered as a unified system. The simulation results also show the temperature of the arc plasma decreases near the center axis. This is caused by the fact that the energy loss by the radiation increases with increases with the metal content.


Hess M.,Chosun University | Allegra G.,Polytechnic of Milan | He J.,CAS Institute of Chemistry | Horie K.,Kozukayama | And 7 more authors.
Pure and Applied Chemistry | Year: 2013

The document gives definitions of terms met in the conventional thermal and thermo mechanical characterisation of polymeric materials. © 2013 IUPAC.


Hess M.,Odjel Znanosti I Tehnologije Polimera | Allegra G.,Odjel za Kemiju | He J.,Kemijski Institute | Horie K.,Kozukayama | And 7 more authors.
Kemija u industriji/Journal of Chemists and Chemical Engineers | Year: 2015

The document gives definitions of terms met in the conventional thermal and thermomechanical characterisation of polymeric materials. © 2015, Croatian Society of Chemical Engineers. All rights reserved.


Schnick M.,TU Dresden | Fussel U.,TU Dresden | Hertel M.,TU Dresden | Rose S.,TU Dresden | And 3 more authors.
Welding in the World | Year: 2011

Current numerical models of gas metal arc welding (GMAW) attempt to combine a magnetohydrodynamic (MHD) model of the arc and a volume-of-fl uid (VoF) model of metal transfer. But in these models vaporization of metal is neglected and the arc region is assumed to be composed of pure argon, as it is common practice for models of gas tungsten arc welding (GTAW). These models predict temperatures over 20 000 K and a temperature distribution similar to GTAW arcs. However, recent spectroscopic temperature measurements in GMAW arcs have demonstrated much lower arc temperatures. In contrast to GTAW arcs, they found a central local minimum of the radial temperature distribution. The paper presents a GMAW arc model that considers metal vapour and which is in very good agreement with experimentally observed temperatures. Furthermore, the model is able to predict the local central minimum in the radial temperature and the radial electric current density distributions for the first time. The axially symmetric model of the welding torch, the workpiece, the wire and the arc (fluid domain) implements MHD as well as turbulent mixing and thermal demixing of metal vapour in argon. The mass fraction of iron vapour obtained from the simulation shows an accumulation in the arc core and another accumulation on the fringes of the arc at 2 000 to 5 000 K. The demixing effects lead to very low concentrations of iron between these two regions. Sensitive analyses demonstrate the influence of the transport and radiation properties of metal vapour, the welding current and the evaporation rate.


Tsujimura Y.,Osaka University | Yamamoto K.,Osaka University | Tanaka M.,Osaka University | Murphy A.B.,CSRIO Materials Science and Engineering | Lowke J.J.,CSRIO Materials Science and Engineering
Welding in the World | Year: 2011

In the present paper, Tungsten Inert Gas (TIG) arc with Constant Voltage (CV) power source is modelled if arc length changes. And TIG arc with Constant Current (CC) power source is also modelled if arc length changes. The TIG arc is assumed on base material of water-cooled copper. For the CV power source, maximum temperature of arc plasma and arc current increase with decrease of arc length. For the CC power source, arc voltage changes but maximum temperature of arc plasma is almost constant in spite of change of arc length. Arc power increases with decrease of arc length for the CV power source. On the other hand, arc power decreases with decrease of arc length for the CC power source. For the CV power source, arc power changes largely if arc length changes. However, for the CC power source, arc power changes little if arc length changes. Heat input from welding power source is more stable using a CC power source than a CV power source at TIG welding with a change of arc length.


Jun Han Z.,CSRIO Materials Science and Engineering | Rider A.E.,CSRIO Materials Science and Engineering | Rider A.E.,University of Sydney | Ishaq M.,CSRIO Materials Science and Engineering | And 7 more authors.
RSC Advances | Year: 2013

The primary goal in hard tissue engineering is to combine high-performance scaffold materials with living cells to develop biologically active substitutes that can restore tissue functions. This requires relevant knowledge in multidisciplinary fields encompassing chemical engineering, material science, chemistry, biology and nanotechnology. Here we present an overview on the recent progress of how two representative carbon nanostructures, namely, carbon nanotubes and graphene, aid and advance the research in hard tissue engineering. The article focuses on the advantages and challenges of integrating these carbon nanostructures into functional scaffolds for repairing and regenerative purposes. It includes, but is not limited to, the critical physico-chemical properties of carbon nanomaterials for enhanced cell interactions such as adhesion, morphogenesis, proliferation and differentiation; the novel designs of two- and three-dimensional nanostructured scaffolds; multifunctional hybrid materials; and the biocompatible aspects of carbon nanotubes and graphene. Perspectives on the future research directions are also given, in an attempt to shed light on the innovative and rational design of more effective biomedical devices in hard tissue engineering. © 2013 The Royal Society of Chemistry.


Lowke J.J.,CSRIO Materials Science and Engineering
Welding in the World | Year: 2011

"Globular" and "spray" are classifi ed by IIW as two distinct modes of metal transfer in "Metal Inert Gas" (MIG) welding. In argon there is a fairly sudden transition current above which the diameter of the molten droplets from the welding wire changes from having a diameter larger than the welding wire in the "globular" mode to being smaller than the welding wire in the "spray" mode. An approximate physical model is considered where, for currents much below the transition current, the forces on the molten drop attached to the welding wire are dominated by surface tension, tending to hold the drop to the wire, and gravity, tending to pull the drop from the wire. Above the transition current, however, the magnetic pinch pressure from the self-magnetic field of the current becomes greater than the increase in pressure inside the drop produced by surface tension so there is then spray transfer. Equating these pressures, a formula for the transition current I, is I = 2π(γD/μ0)1/2 where D is the diameter of the wire, γ is the surface tension coeffi cient of the molten metal and μ0 is the permeability of free space. Predicted transition currents are in fair agreement with experimental results for both steel and aluminium, for wire diameters varying from 0.4 to 3.0 mm.

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