Conductive cooling of lava: columnar joint diameter and stria width as functions of cooling rate and thermal gradient

1995 ◽  
Vol 69 (1-2) ◽  
pp. 95-103 ◽  
Author(s):  
Kenneth A. Grossenbacher ◽  
Stephen M. McDuffie
Keyword(s):  
Cooling Rate ◽  
Thermal Gradient ◽  
Columnar Joint

Local solidification thermal parameters affecting the eutectic extent in Sn-Cu and Sn-Bi solder alloys

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Rafael Kakitani ◽  
Cassio Augusto Pinto da Silva ◽  
Bismarck Silva ◽  
Amauri Garcia ◽  
Noé Cheung ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Thermal Gradient ◽  
Experimental Spectrum ◽  
Eutectic Growth ◽  
Solidification Velocity ◽  
Solder Alloys ◽  
Content Type ◽  
Growth Zones ◽  
Coupled Growth

Purpose Overall, selection maps about the extent of the eutectic growth projects the solidification velocities leading to given microstructures. This is because of limitations of most of the set of results when obtained for single thermal gradients within the experimental spectrum. In these cases, associations only with the solidification velocity could give the false impression that reaching a given velocity would be enough to reproduce a result. However, that velocity must necessarily be accompanied by a specific thermal gradient during transient solidification. Therefore, the purpose of this paper is to not only project velocity but also include the gradients acting for each velocity. Design/methodology/approach Compilation of solidification velocity, v, thermal gradient, G, and cooling rate, Ṫ, data for Sn-Cu and Sn-Bi solder alloys of interest is presented. These data are placed in the form of coupled growth zones according to the correlated microstructures in the literature. In addition, results generated in this work for Sn-(0.5, 0.7, 2.0, 2.8)% Cu and Sn-(34, 52, 58)% Bi alloys solidified under non-stationary conditions are added. Findings When analyzing the cooling rate (Ṫ = G.v) and velocity separately, in or around the eutectic composition, a consensus cannot be reached on the resulting microstructure. The (v vs. G) + cooling rate diagrams allow comprehensive analyzes of the combined v and G effects on the subsequent microstructure of the Sn-Cu and Sn-Bi alloys. Originality/value The present paper is devoted to the establishment of (v vs. G) + cooling rate diagrams. These plots may allow comprehensive analyses of the combined v and G effects on the subsequent microstructure of the Sn-Cu and Sn-Bi alloys. This microstructure-processing mapping approach is promising to predict phase competition and resulting microstructures in soldering of Sn-Cu and Sn-Bi alloys. These two classes of alloys are of interest to the soldering industry, whereas manipulation of their microstructures is considered of utmost importance for the metallurgical quality of the product.

58 MULTI-THERMAL GRADIENT FREEZING ALLOWS THE CRYOPRESERVATION OF SHEEP WHOLE OVARIES WITH THE SAME EFFICIENCY OF OVARIAN FRAGMENTS

2013 ◽  
Vol 25 (1) ◽  
pp. 176
Author(s):  
T. A. L. Brevini ◽  
S. Maffei ◽  
G. Pennarossa ◽  
A. Arav ◽  
F. Gandolfi
Keyword(s):  
Cooling Rate ◽  
Nude Mice ◽  
Thermal Gradient ◽  
Ovarian Tissue ◽  
Sample Volume ◽  
Ovarian Tissue Cryopreservation ◽  
Cortical Region ◽  
Cryoprotectant Solution ◽  
Whole Ovary ◽  
Whole Ovaries

Ovarian tissue cryobanking is proposed as an effective option for preserving female fertility in cancer patients. At present 2 options are available: cryopreservation of ovarian cortical fragments or of the whole ovary. The use of whole ovary reduces ischemic insult. However, the larger the sample volume, the more difficult it is to introduce the cryoprotective agents and to ensure an adequate cooling rate that minimizes tissue damage. For this reason, we used the multi-thermal gradient method, based on running the sample through a temperature gradient. This allows a homogeneous cooling rate through the whole sample independently from its volume. The aim of the study was to determine whether multi-thermal gradient freezing allows a substantial reduction of the damages induced by cryopreservation of large samples by comparing the viability of cortical fragments versus whole ovaries after thawing and grafting in nude mice. Sheep ovaries were collected at the local abattoir and randomly divided into 3 groups: A) ovaries frozen as cortical fragments, B) ovaries frozen as whole organs, and C) fresh ovaries immediately processed for further analysis (control). Ovarian fragments (10 × 5 × 1 mm) were sliced from the cortical region and immersed into cryoprotectant solution (Leibovitz L-15 medium, 10% FCS, and 1.5 M dimethyl sulfoxide), while whole ovaries were perfused with the same solution. Samples were placed into glass freezing tubes 16 mm in diameter filled with cryoprotectant solution. Samples were frozen with the multi-thermal gradient freezing apparatus (Core Dynamics, Ness Ziona, Israel) progressing along the thermal gradient at a rate of 0.01 mm s–1, resulting in a cooling rate of 0.3°C min–1. Two weeks later, samples were thawed by plunging the tubes into a 37°C water bath with gentle shaking. Whole ovaries were perfused with 10 mL of HEPES-Talp medium, 0.5 M sucrose, and 10 IU mL–1 of heparin and their cortical region was cut into fragments. These fragments and those derived from group A were rehydrated in L-15 medium with decreasing sucrose concentrations. Fragments (2 × 2 × 1 mm) were xenografted in the dorsal region of 6 nude mice for each group. Mice were killed after 8 weeks and grafts were collected for analysis. Cryopreserved samples were compared with each other and fresh controls (group C). Morphologically normal follicles at primordial, primary, and secondary stages were visible in all samples. Cell proliferation was assessed measuring Ki-67 mRNA and counting immunohistochemically positive cells. The FSH receptor and GDF9 gene expression were used to evaluate tissue viability. No significant differences for any of these parameters were measured amongst the groups. We conclude that directional freezing is an effective method for ovarian tissue cryopreservation independently from the sample volume, thus overriding the limitations usually associated with whole-organ banking. Supported by AIRC IG 10376 and by Carraresi Foundation.

Numerical Studies on Channel Formation and Growth During Solidification: Effect of Process Parameters

2006 ◽  
Vol 129 (4) ◽  
pp. 548-558 ◽  
Author(s):  
Jayesh Jain ◽  
Arvind Kumar ◽  
Pradip Dutta
Keyword(s):  
Cooling Rate ◽  
Process Parameters ◽  
Thermal Gradient ◽  
Chloride Solution ◽  
Liquid Fraction ◽  
Process Conditions ◽  
Channel Formation ◽  
Initial Concentration ◽  
Numerical Studies ◽  
Freckle Formation

In the present work, solidification of a hyper-eutectic ammonium chloride solution in a bottom-cooled cavity (i.e. with stable thermal gradient) is numerically studied. A Rayleigh number based criterion is developed, which determines the conditions favorable for freckles formation. This criterion, when expressed in terms of physical properties and process parameters, yields the condition for plume formation as a function of concentration, liquid fraction, permeability, growth rate of a mushy layer, and thermophysical properties. Subsequently, numerical simulations are performed for cases with initial and boundary conditions favoring freckle formation. The effects of parameters, such as cooling rate and initial concentration, on the formation and growth of freckles are investigated. It was found that a high cooling rate produced larger and more defined channels which are retained for a longer durations. Similarly, a lower initial concentration of solute resulted in fewer but more pronounced channels. The number and size of channels are also found to be related to the mushy zone thickness. The trends predicted with regard to the variation of number of channels with time under different process conditions are in accordance with the experimental observations reported in the literature.

Some Fundamental Considerations During Rapid Solidification Processing

1983 ◽  
Vol 28 ◽  
Author(s):  
V. Laxmanan
Keyword(s):  
Cooling Rate ◽  
Rapid Solidification ◽  
Stability Criterion ◽  
Thermal Gradient ◽  
Absolute Stability ◽  
Melt Spinning ◽  
Rapid Solidification Processing ◽  
Dendritic Solidification ◽  
Solidification Processing ◽  
The Third

ABSTRACTThree estimates of the solidification rates required to obtain a fully homogeneous structure during rapid solidification processing (RSP) have been made. One is given by the “absolute stability” criterion and another obtained from a new analysis for dendritic solidification. The third estimate, also derived from the above analysis, requires that “hypercooled” conditions be maintained after nucleation. A mechanism for the formation of “featureless” segregation-free zones during melt spinning and atomization processes is suggested and expressions for the critical cooling rate and thermal gradient required to produce such structures have been obtained.

Thermal history analysis of surface heating of mild steel with different laser beam geometries

2006 ◽  
Vol 220 (10) ◽  
pp. 1549-1557 ◽  
Author(s):  
S Safdar ◽  
L Li ◽  
M A Sheikh ◽  
M J Schmidt
Keyword(s):  
Material Processing ◽  
Laser Beam ◽  
Cooling Rate ◽  
Laser Processing ◽  
Thermal Gradient ◽  
Surface Heating ◽  
Thermal Gradients ◽  
Transient Effects ◽  
Laser Material Processing ◽  
Cooling Rates

Lasers are in use in the material processing industry for well over 30 years now. The way in which the temperature is distributed inside the material is of prime importance in laser material processing, as it directly affects the heating/cooling rates and thermal gradients. Optimization of different laser processes requires control over heating/cooling rate and thermal gradient. Different processes have different requirements of heating/cooling rate and thermal gradient. Knowing these parameters and relevant metallurgical information, one can predict the microstructure and hence control the material properties. To date, majority of laser processing is carried out by using either circular or rectangular beam. At present, the variation in temperature distribution to control the heating/cooling rates and thermal gradients is caused by the variation either in laser power or in scanning speed. Variations in these parameters are often limited by other processing conditions. Although different beam intensity distributions with circular or rectangular laser beams have been studied to improve the process, no other beam geometries have been investigated. The effect of laser beam geometry on laser processing of materials has received very little attention. This article presents an investigation of the effects of different beam geometries including circular, rectangular, and triangular shapes on heating of metallic materials. Finite-element modelling technique has been used to simulate the transient effects of a moving beam for laser surface heating of metals. The temperature distributions, cooling rates, and thermal gradients have been calculated. Some of the results have been compared with the experimental data.

scholarly journals Deformation mechanisms of Inconel-718 at nanoscale by molecular dynamics

2021 ◽  
Author(s):  
Abrar Faiyad ◽  
Md Adnan Mahathir Munshi ◽  
Md Mahbubul Islam ◽  
Sourav Saha
Keyword(s):  
Molecular Dynamics ◽  
3D Printing ◽  
Dislocation Density ◽  
Cooling Rate ◽  
Inconel 718 ◽  
Thermal Gradient ◽  
Deformation Mechanisms ◽  
Initial Dislocation Density ◽  
Metal 3D Printing ◽  
Super Alloy

Ni-based super alloy Inconel-718 is ubiquitous in metal 3D printing where a high cooling rate and thermal gradient are present. These manufacturing conditions are conducive to high initial dislocation density...

Microstructural Modeling of Mg Alloys and Experimental Validation

2013 ◽  
Vol 765 ◽  
pp. 185-189
Author(s):  
Manas Paliwal ◽  
Youn Bae Kang ◽  
Elhachmi Essadiqi ◽  
In Ho Jung
Keyword(s):  
Cooling Rate ◽  
Thermal Gradient ◽  
Reasonable Agreement ◽  
Experimental Validation ◽  
Systematic Investigation ◽  
Solidification Velocity ◽  
Second Phase ◽  
Microstructural Modeling ◽  
Modeling Data ◽  
The Impact

A systematic investigation was carried out in the present study to study the impact of solidification variables like thermal gradient (G), solidification velocity (V) and cooling rate on the second phase fraction and microsegregration in Mg-Al (3, 6 , 9 wt.%) binary alloys. Solidification experiments such as directional solidification and gravity castings were conducted to obtain a cooling rate in the range of 0.05-700 K/s. The experimental results were tested against the microstructural modeling data and a reasonable agreement was obtained between them.

Redefining cooling rate in terms of ice front velocity and thermal gradient: First evidence of relevance to freezing injury of lymphocytes

Cryobiology ◽  
1990 ◽  
Vol 27 (3) ◽  
pp. 279-287 ◽  
Author(s):  
J. Beckmann ◽  
Ch. Körber ◽  
G. Rau ◽  
A. Hubel ◽  
E.G. Cravalho
Keyword(s):  
Cooling Rate ◽  
Thermal Gradient ◽  
Front Velocity ◽  
Freezing Injury

Experimental Observations of Thermal Bow due to Natural Convection on a Gas Turbine Compressor Rotor Shaft Analogue

2016 ◽  
Author(s):  
E. O. Smith ◽  
A. J. Neely ◽  
A. P. Butcher
Keyword(s):  
Natural Convection ◽  
Cooling Rate ◽  
Gas Turbine ◽  
Parametric Study ◽  
Thermal Gradient ◽  
Thermal Plume ◽  
Rotor Shaft ◽  
Compressor Rotor ◽  
Numerical Predictions ◽  
Gas Turbine Compressor

This study describes the development of an experimental apparatus designed to provide initial validation of numerical simulations of a gas turbine compressor rotor shaft under thermal bow due to natural convection. The experimental analogue represents a simplified model developed by the authors in previous works, designed to represent the basic elements of a compressor rotor shaft, as part of an ongoing parametric study into the influence of compressor design and integration on the onset time, duration, and severity of thermal bow, and the propensity of an engine to suffer from the Newkirk Effect. The semi-enclosed steel shaft, mounted on a support frame, was heated to approximately 600K in a convective oven before being removed and allowed to cool under ambient conditions. Observations of the shaft under natural cooling were made using several experimental techniques, including temperature profiling using thermographic imaging and a thermocouple array, and physical distortion measurement using linear variable displacement transducer (LVDT) probes. The behaviour of the buoyant plume was also observed using background oriented schlieren (BOS). Using these techniques, the natural convection-driven thermal gradient and resultant physical deformation were measured and recorded over a period of 60 minutes. The observed thermal gradients and resultant thermal bow distortions were then compared to a one-way fluid thermal structural interaction (FTSI) 3D conjugate heat transfer (CHT) computational fluid dynamics (CFD) and finite element analysis (FEA) model developed by the authors, in order to validate the numerical model. The behaviour of the thermal plume from the BOS imagery was also used as a qualitative validation method. The temperature measurements and overall cooling rate measured on the experimental model showed good agreement with the numerical predictions (within 1%); however, uncertainties in the initial phase of the experiment led to error in the numerical prediction of the thermal gradient and resultant thermal bow measurements (error of up to 63%). Noting the uncertainties in the experiment, the agreement between numerical and experimental results with respect to the overall cooling rate indicates that the numerical approach being employed as part of the larger parametric study into gas turbine compressor rotor shaft thermal bow is appropriate and valid.

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