GHTA Spot-Welding Experiments of Aluminum and Titanium Plates under a Simulated Space Environment.

Suita, Yoshikazu; Kurokawa, Teppei; Sato, Junko; Shobako, Shinitiro; Kohno, Teppei; Tsukuda, Yoshiyuki; Terajima, Noboru; Masubuchi, Koichi

doi:10.2322/tjsass.45.139

Cited by 7 publications

(5 citation statements)

References 8 publications

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“…The magnitude of the gravity-or densitydriven buoyancy effect scales with the Rayleigh number (R a ), R a = β g ∆T D 3 ν -1 κ -1 (5) The magnitude of surface-tension-driven convection scales with the Marangoni number (M a ), M a = -∂σ/∂T ∆T D µ -1 κ -1 (6) In these equations, β = -1/ρ(∂ρ/∂T) is the thermal-expansion coeffi cient, ∂σ/∂T is the temperature-dependence of surface tension, g is the acceleration due to gravity, ∆T is the temperature gradient, D is a characteristic length, ν is the kinematic viscosity, µ is the dynamic viscosity, and κ is the thermal diffusivity. The relative magnitude of the Marangoni and gravity-driven buoyancy effects must be compared to determine which effect dominates the physical state of the melt pool.…”

Section: Discussionmentioning

confidence: 99%

“…Masubuchi and Nayama 3 observed that in microgravity, the weld bead free surface did not contain ripples, which form in a terrestrial environment. Wang and Tandon 4 reported increases in weld depth and surface ripples in microgravity compared to in 1 g. Suita et al 5 concluded that microstructure development in the weld metal was unaffected by simulated changes in gravity.…”

Section: Introductionmentioning

confidence: 99%

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Prototype analysis of gravity-modulated welding by inverting weld cross sections

Cooper

Lambrakos

Jones

2003

JOM

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WeldingResearch SummaryWelding studies are usually conducted in the terrestrial environment where gravity plays an uncertain role in governing melt pool dynamics. Microgravity welding research is essential to "switchoff" the gravity component and its infl uence on the solidifi cation structure or to investigate welding as a fabrication tool in space. This article examines changes in weld-pool characteristics due to changes in gravitational environment. Also examined is the use of the inverseproblem approach to determine the dependence of the temperature histories of welds on process changes due to changes in gravity.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Prototype analysis of gravity-modulated welding by inverting weld cross sections

Cooper

Lambrakos

Jones

2003

JOM

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“…が行われ，微小重力環境が溶接現象に及ぼす影響が調査されている．著者らは 1993 年に中空タングステン電極を使用する宇宙 GHTA(Gas Hollow Tungsten Arc)溶接法 12,13) を提案した．1998 年には真空チャンバを搭載した航空機の放物飛行で得られる模擬宇宙環境下での GHTA 溶接実験 14,15)…”

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GHTA Welding Experiments in the Space Station Orbital Pressure.

義一¹,

信一郎²,

順子³

et al. 2003

QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY

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As a welding method in space, the authors have proposed the GHTA (Gas Hollow Tungsten Arc) welding method in the previous papers, where some GHTA welding experiments have been conducted under the condition of low pressure (10 -2 Pa) and/or the micro-gravity. In the present paper, a feasibility study has been conducted whether the method can be used under such a high vacuum condition (10 -5 Pa) as on the space station orbit.As a result, it is made clear that the GHTA method is quite feasible under the high vacuum condition and its melting process strongly depends on the operating gas species such as Ne, Ar and Kr. Increasing the flow rate of operating gas decreases the mass of metal vapor from molten pool and the use of a heavy operating gas such as Kr also decreases the mass of metal vapor.

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“…We are now performing research and development of the GHTA welding process [6][7][8][9][10] for space applications. The high-frequency device employed to start the arc in previous conventional experiments may be an obstacle for electric devices placed on the ISS due to the creation of electromagnetic noise.…”

Section: Introductionmentioning

confidence: 99%

Welding Experiments of Aluminum Alloy by Space GHTA Welding at ISS Orbital Pressure

Suita¹,

Takai²,

Sugiyama³

et al. 2005

Trans. Japan Soc. Aero. S Sci.

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As a feasible welding method in space, the authors previously proposed the space GHTA (Gas Hollow Tungsten Arc) welding process. However, space GHTA welding with a high-frequency device for arc start may cause electromagnetic noise problems for the computer equipment placed on the ISS (International Space Station). Therefore, in this report, welding experiments of space GHTA welding using aluminum alloy with a high-voltage DC device for arc start were carried out at the ISS orbital pressure, 10 À5 Pa. It is clear from the experiments using a high-voltage DC device in a high-vacuum condition, that there is a shifting phenomenon in which the spark discharge shifts to either a glow discharge or an arc discharge when starting the arc. Welding projects in space need an arc discharge, so we investigated the effects of welding parameters on the arc formation ratio. As a result, space GHTA welding with a high-voltage DC device can be used for arc start when welding at the ISS orbital pressure.

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GHTA Spot-Welding Experiments of Aluminum and Titanium Plates under a Simulated Space Environment.

Cited by 7 publications

References 8 publications

Prototype analysis of gravity-modulated welding by inverting weld cross sections

Prototype analysis of gravity-modulated welding by inverting weld cross sections

GHTA Welding Experiments in the Space Station Orbital Pressure.

Welding Experiments of Aluminum Alloy by Space GHTA Welding at ISS Orbital Pressure

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