scholarly journals Microsegregation Model Including Convection and Tip Undercooling: Application to Directional Solidification and Welding

Materials ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1252 ◽  
Author(s):  
Thomas Billotte ◽  
Dominique Daloz ◽  
Bernard Rouat ◽  
Guillaume Tirand ◽  
Jacob Kennedy ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Directional Solidification ◽  
Thermal Gradient ◽  
Experimental Results ◽  
Microsegregation Model ◽  
Gas Tungsten Arc ◽  
Melt Pool ◽  
Model Predictions ◽  
Solidification Processes ◽  
Alloy Filler

The microsegregation behavior of alloy filler metal 52 (FM 52) was studied using microprobe analysis on two different solidification processes. First, microsegregation was characterized in samples manufactured by directional solidification, and then by gas tungsten arc welding (GTAW). The experimental results were compared with Thermo-Calc calculations to verify their accuracy. It was confirmed that the thermodynamic database predicts most alloying elements well. Once this data had been determined, several tip undercooling calculations were carried out for different solidification conditions in terms of fluid flow and thermal gradient values. These calculations allowed the authors to develop a parametrization card for the constants of the microsegregation model, according to the process parameters (e.g., convection in melt pool, thermal gradient, and growth velocity). A new model of microsegregation, including convection and tip undercooling, is also proposed. The Tong–Beckermann microsegregation model was used individually and coupled with a modified Kurz-Giovanola-Trivedi (KGT) tip undercooling model, in order to take into account the convection in the fluid flow at the dendrite tip. Model predictions were compared to experimental results and showed the microsegregation evolution accurately.

Directional Solidification Behavior of CMSX-6 Superalloy

2014 ◽  
Vol 788 ◽  
pp. 554-559
Author(s):  
Shuai Zheng ◽  
Yu Liang Jia ◽  
Jiao Tang
Keyword(s):  
Single Crystal ◽  
Directional Solidification ◽  
Thermal Gradient ◽  
First Generation ◽  
Primary Dendrite ◽  
Solidification Rate ◽  
Experimental Results ◽  
Single Crystal Superalloy ◽  
Solidification Behavior ◽  
Rate Range

The directional solidification behavior of a first generation single crystal superalloy CMSX-6 was investigated. The solidification rate range in 25μm/s to 100μm/s and a thermal gradient G of 30K/cm were used for the present study. The experimental results show that the primary dendrite arm space (PDAS) decreased from (432±8) μm to (369±4) μm as the solidification rate increased, and the sizes of the eutectic pools also decreased as the solidification rate increased. And the volume fractions of eutectic γ/γ' were about 7% to 9% with different solidification rate. The γ/γ'- eutectic was comprised with coarse γ' phase and fine γ/γ' network. The morphology of the γ/γ’ eutectic supported the possibility that the solidification of γ/γ’ eutectic initiates with the formation of fine γ/γ’.

Numerical simulation of heat transfer and fluid flow in a double-sided gas-tungsten arc welding process

2003 ◽  
Vol 217 (1) ◽  
pp. 87-97 ◽  
Author(s):  
H Dong ◽  
H Gao ◽  
L Wu
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Arc Welding ◽  
Welding Process ◽  
Gas Tungsten Arc Welding ◽  
Experimental Results ◽  
Staggered Grid ◽  
Gas Tungsten Arc ◽  
Gas Tungsten ◽  
Arc Welding Process

Double-sided arc welding powered by a single power supply is a new type of welding process developed recently at the University of Kentucky. Experiments show that this process has advantages over conventional single-sided arc welding in enhancing penetration, minimizing distortion, improving solidification structure and welding aluminium without the necessity of using filler metal for cracking prevention. In this paper, a three-dimensional transient numerical model is developed for the heat transfer and fluid flow in double-sided gas-tungsten arc welding, including flat-position welding and vertical-up position welding. Based on a non-uniform staggered grid system, the governing equations are solved numerically using the SIMPLEC algorithm. The roles of the surface tension gradient, electromagnetic force and buoyancy force in determining the fluid flow and weld penetration are analysed and compared with those in the conventional arc welding process. The computed weld geometry is compared with experimental results and it is found that the computational results agree with the experimental results with reasonable accuracy.

Modeling and Experiments of Laser Cladding With Droplet Injection

2005 ◽  
Vol 127 (9) ◽  
pp. 978-986 ◽  
Author(s):  
J. Choi ◽  
L. Han ◽  
Y. Hua
Keyword(s):  
Fluid Flow ◽  
Laser Cladding ◽  
Dynamic Motion ◽  
Cladding Layer ◽  
Melt Pool ◽  
Material Deposition ◽  
Modeling And Experiments ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
The Impact

Laser aided Directed Material Deposition (DMD) is an additive manufacturing process based on laser cladding. A full understanding of laser cladding is essential in order to achieve a steady state and robust DMD process. A two dimensional mathematical model of laser cladding with droplet injection was developed to understand the influence of fluid flow on the mixing, dilution depth, and deposition dimension, while incorporating melting, solidification, and evaporation phenomena. The fluid flow in the melt pool that is driven by thermal capillary convection and an energy balance at the liquid–vapor and the solid–liquid interface was investigated and the impact of the droplets on the melt pool shape and ripple was also studied. Dynamic motion, development of melt pool and the formation of cladding layer were simulated. The simulated results for average surface roughness were compared with the experimental data and showed a comparable trend.

scholarly journals Thermal Steady States of Gases in a Gravitational Field

2011 ◽  
Vol 66 (1-2) ◽  
pp. 123-133
Author(s):  
Kunihiko Kigoshi
Keyword(s):  
Heat Transfer ◽  
Gravitational Field ◽  
Temperature Difference ◽  
Thermal Gradient ◽  
Vertical Direction ◽  
Steady States ◽  
Gas Pressure ◽  
Experimental Results ◽  
Gravity Effect ◽  
Gas Molecules

This paper presents results on observations of a temperature difference between the top and bottom of a vessel filled with gas in a gravitational field. The observed temperature at the top of the vessel was always lower than the temperature at the bottom of the vessel, and this temperature difference was persistent and steady over more than 20 h. The magnitude of the temperature difference depends on the types of gas molecules present but is independent of the gas pressure in the vessel within the range from 2.7×104 Pa to 27 Pa. A temperature difference between the top and the bottom is only observed along the vertical direction and is only observed when the vessel contains a gas. These experimental results indicate a gravity effect on molecular heat transfer which enables the transport of energy in the gas without a thermal gradient.

scholarly journals A Simplified Model Applied to the Barite Sag and Fluid Flow in Drilling Muds: Simulation and Experimental Results

2017 ◽  
Vol 72 (4) ◽  
pp. 23 ◽  
Author(s):  
José Messias Ribeiro ◽  
Felipe Moreira Eler ◽  
André Leibson Martins ◽  
Cláudia Miriam Scheid ◽  
Luís Américo Calçada ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Experimental Results ◽  
Simplified Model ◽  
Drilling Muds

Cooling Process for Directional Solidification in Directed Energy Deposition

2018 ◽  
Author(s):  
Keiya Ishiyama ◽  
Ryo Koike ◽  
Yasuhiro Kakinuma ◽  
Tetsuya Suzuki ◽  
Takanori Mori
Keyword(s):  
Directional Solidification ◽  
Thermal Gradient ◽  
Large Scale ◽  
Energy Deposition ◽  
Production Efficiency ◽  
Production Costs ◽  
Special Structure ◽  
Mechanical Stiffness ◽  
Directed Energy Deposition ◽  
Directed Energy

Additive manufacturing (AM) for metals has attracted attention from industry because of its great potential to enhance production efficiency and reduce production costs. Directed energy deposition (DED) is a metal AM process suitable to produce large-scale freeform metal products. DED entails irradiating the baseplate with a laser beam and launching the metal powder onto the molten spot to produce a metal part on the baseplate. Because the process enables powder from different materials to be used, DED is widely applicable to valuable production work such as for a dissimilar material joint, a graded material, or a part with a special structure. With regard to parts with a special structure, directional solidification can prospectively be used in the power plant and aerospace industries because it can enhance the stiffness in a specific direction via only a simple process. However, conventional approaches for directional solidification require a special mold in order to realize a long-lasting thermal gradient in the part. On the other hand, from the viewpoint of thermal distribution in a produced part, DED is able to control the gradient by controlling the position of the molten pool, i.e., the position of the laser spot. Moreover, unlike casting, the thermal gradient can be precisely oriented in the expected direction, because the laser supplies heat energy on the regulated spot. In this study, the applicability of DED to directional solidification in Inconel® 625 is theoretically and experimentally evaluated through metal structure observation and Vickers hardness measurements. Furthermore, the effect of two different cooling processes on directional solidification is also considered with the aim of improving the mechanical stiffness of a part produced by DED. The observations and experimental results show that both the cooling methods (baseplate cooling and intermittent treatment with coolant) are able to enhance the hardness while retaining the anisotropy.

scholarly journals Grounding Action Descriptions in Videos

2013 ◽  
Vol 1 ◽  
pp. 25-36 ◽  
Author(s):  
Michaela Regneri ◽  
Marcus Rohrbach ◽  
Dominikus Wetzel ◽  
Stefan Thater ◽  
Bernt Schiele ◽  
...  
Keyword(s):  
Natural Language ◽  
Recent Work ◽  
Visual Information ◽  
General Purpose ◽  
Experimental Results ◽  
High Quality ◽  
Improve Model ◽  
Model Predictions ◽  
Static Images

Recent work has shown that the integration of visual information into text-based models can substantially improve model predictions, but so far only visual information extracted from static images has been used. In this paper, we consider the problem of grounding sentences describing actions in visual information extracted from videos. We present a general purpose corpus that aligns high quality videos with multiple natural language descriptions of the actions portrayed in the videos, together with an annotation of how similar the action descriptions are to each other. Experimental results demonstrate that a text-based model of similarity between actions improves substantially when combined with visual information from videos depicting the described actions.

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