The Coarsening of Dendrite Arm Spacing during Solidification of Al-Cu-Mn Alloy

2011 ◽  
Vol 239-242 ◽  
pp. 2029-2033 ◽  
Author(s):  
Zhi He
Keyword(s):  
Boundary Layer ◽  
Diffusion Flux ◽  
Experimental Results ◽  
Simplified Model ◽  
Back Diffusion ◽  
Secondary Dendrite Arm Spacing ◽  
Dendrite Arm Spacing ◽  
Solute Boundary Layer ◽  
Good Agreement

A secondary dendrite arm spacing coarsening model for multi-component alloy is proposed, where the back diffusion flux in solid is simplified by introducing the parameter of solute boundary layer,δi. The simplified model was applied to the predication of the secondary arm spacing of directional solidified Al-Cu-Mn alloy. The good agreement between the experimental results and the calculated lines shows that this simplified model is satisfactory for the prediction of dendrite arm coarsening during solidification in multi-component alloys.

Measurement of sheath characteristics in the presence of convection and ionization

1996 ◽  
Vol 74 (9-10) ◽  
pp. 671-675 ◽  
Author(s):  
R. M. Clements ◽  
J. R. Dawe ◽  
S. A. H. Rizvi ◽  
P. R. Smy
Keyword(s):  
Boundary Layer ◽  
Plasma Electron ◽  
Experimental Results ◽  
Ion Density ◽  
Current Voltage ◽  
Planar Grid ◽  
Theoretical Predictions ◽  
Flame Plasma ◽  
Theoretical Paper ◽  
Good Agreement

A flame plasma whose electron and (or) ion density can be varied over several orders of magnitude is constrained to flow perpendicular to a planar grid Langmuir probe. The probe is biased negative to the plasma, and the current–voltage characteristics and the thickness of the ion sheath formed at the probe are measured. The level of the electron and (or) ion density is set within a range at which the probe current due to thermal ionization throughout the sheath is comparable with the current of ions convected into the sheath. The experimental results are compared with the predictions of a recent theoretical paper that calculates the effect of recombination upon the characteristics of planar, cylindrical, and spherical probes with boundary layer sheaths. The theoretical predictions and experimental results for an idealized planar configuration show good agreement over wide ranges of variation of probe bias and plasma electron and (or) ion density. This verification of the theoretical planar electrode – perpendicular-flow model, which is the basis for all three boundary layer relations, is seen as providing strong backing for these relations, which have application to ionization measurements in various forms of recombinant plasma.

Prediction of Silicide Formation Sequence from the Principle of the Largest Free Energy Degradation Rate

1993 ◽  
Vol 311 ◽  
Author(s):  
Lin Zhang ◽  
Douglas G. Ivey
Keyword(s):  
Free Energy ◽  
Kinetic Model ◽  
Degradation Rate ◽  
Diffusion Flux ◽  
Experimental Results ◽  
Silicide Formation ◽  
Change Rate ◽  
Energy Degradation ◽  
Generalized Kinetic Model ◽  
Good Agreement

ABSTRACTRecently, a generalized kinetic model for silicide formation has been developed and a principle of the largest free energy degradation rate (largest FEDR) has been proposed. Free energy change rate as a function of diffusion flux has been derived from the kinetic model so that the principle can be justified not only for first phase formation but also for the subsequent processes. Silicide formation sequence predictions, from the model and the FEDR principle, for 15 metal-Si systems have shown very good agreement with the experimental results reported in the literature. In this paper, a brief introduction to the model and the principle is given, followed by examples of the predictions for several metal-Si systems and comparison with experimental results.

scholarly journals The aerodynamics of the curled wake: a simplified model in view of flow control

2019 ◽  
Vol 4 (1) ◽  
pp. 127-138 ◽  
Author(s):  
Luis A. Martínez-Tossas ◽  
Jennifer Annoni ◽  
Paul A. Fleming ◽  
Matthew J. Churchfield
Keyword(s):  
Boundary Layer ◽  
Wind Farm ◽  
Stokes Equations ◽  
Large Eddy Simulations ◽  
Simplified Model ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Actuator Disk ◽  
Large Eddy ◽  
Good Agreement

Abstract. When a wind turbine is yawed, the shape of the wake changes and a curled wake profile is generated. The curled wake has drawn a lot of interest because of its aerodynamic complexity and applicability to wind farm controls. The main mechanism for the creation of the curled wake has been identified in the literature as a collection of vortices that are shed from the rotor plane when the turbine is yawed. This work extends that idea by using aerodynamic concepts to develop a control-oriented model for the curled wake based on approximations to the Navier–Stokes equations. The model is tested and compared to time-averaged results from large-eddy simulations using actuator disk and line models. The model is able to capture the curling mechanism for a turbine under uniform inflow and in the case of a neutral atmospheric boundary layer. The model is then incorporated to the FLOw Redirection and Induction in Steady State (FLORIS) framework and provides good agreement with power predictions for cases with two and three turbines in a row.

Damping of surface waves in an incompressible liquid

1957 ◽  
Vol 2 (2) ◽  
pp. 172-184 ◽  
Author(s):  
K. M. Case ◽  
W. C. Parkinson
Keyword(s):  
Boundary Layer ◽  
Surface Waves ◽  
Viscous Dissipation ◽  
Laminar Boundary Layer ◽  
Small Amplitude ◽  
Incompressible Liquid ◽  
Experimental Results ◽  
Cylinder Radius ◽  
Theory And Experiment ◽  
Good Agreement

The damping of surface waves of small amplitude in liquid contained in cylinders has been calculated. Viscous dissipation in an assumed laminar boundary layer was taken to be the primary cause of damping. Experimental results were obtained for the logarithmic decrement as a function of the ratio of liquid height to cylinder radius for several water-filled cylinders. Theory and experiment were found to be in good agreement.

Study on Measurement and Simplified Model of Burning Rate of AP/HTPB Base Bleed Propellant under High Pressure

2013 ◽  
Vol 724-725 ◽  
pp. 1176-1180 ◽  
Author(s):  
Hui Shen ◽  
Yong Gang Yu
Keyword(s):  
High Pressure ◽  
Burning Rate ◽  
Experimental Results ◽  
Simplified Model ◽  
Combustion Theory ◽  
Calculation Results ◽  
Htpb Propellant ◽  
Base Bleed ◽  
Good Agreement

In order to understand the burning rate of AP/HTPB propellant of the base bleed unit, the p-t curves of combustion of AP/HTPB base bleed propellant are measured in the closed bomb. The burning rate formula of the propellant under 50-200MPa is obtained by fitting to the experimental results. Based on division zone combustion theory, a simplified model of the burning rate of AP/HTPB base bleed propellant under high pressure is established. The calculation results and the experimental results are in good agreement.

Influence of some Chemical Elements on SDAS of A357 Alloy

2021 ◽  
Vol 1020 ◽  
pp. 3-7
Author(s):  
Jie Hua Pan ◽  
Ke Zhun He ◽  
Meng Wang ◽  
Jian Min Zeng
Keyword(s):  
Chemical Elements ◽  
Cast Alloy ◽  
A357 Alloy ◽  
Solidification Condition ◽  
Secondary Dendrite Arm Spacing ◽  
Refining Effect ◽  
Solidification Model ◽  
Dendrite Arm Spacing ◽  
Good Agreement

A solidification model of coarsening coefficient for the criterion of secondary dendrite arm spacing has been established in this paper. When the model is applied to aluminum cast alloy, it is found that the model is in good agreement with the experiment results. Experiments and analysis show that addition of some chemical elements is conducive to the refinement of the secondary dendrite arm spacing under the same solidification condition. Different chemical elements have different refining effects, and Zr and Ti have better refining effect on A357 aluminum cast alloy than Cu.

scholarly journals Automatic Determination of Secondary Dendrite Arm Spacing in AlSi-Cast Microstructures

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2827
Author(s):  
Christian Gawert ◽  
Rüdiger Bähr
Keyword(s):  
Computation Time ◽  
Automatic Measurement ◽  
Secondary Dendrite Arm Spacing ◽  
Dendrite Arm Spacing ◽  
Aluminum Cast Alloys ◽  
Cast Alloys ◽  
The Individual ◽  
Good Agreement

A new procedure for the automatic measurement of the secondary dendrite arm spacing (SDAS) from microscopic images is presented. The individual primary and secondary dendrite arms are identified through suitable segmentation techniques and clustered in such a way that dendritic structures are obtained suitable for SDAS measurement. The algorithms are applied to two different hypoeutectic aluminum cast alloys, and the quality of the measurements obtained is assessed through a comparison to manually measured SDAS values. A good agreement between the automated measurements and the distribution of manual measurements is found for both cast structures considered. In addition, a decrease in computation time is observed which allows for an increase in measurement density that is used to characterize the microstructures.

An Investigation of the Corner Secondary Flows Generated in Planar Nozzles

1974 ◽  
Vol 96 (3) ◽  
pp. 234-245
Author(s):  
W. B. Wagner ◽  
J. A. Owczarek
Keyword(s):  
Boundary Layer ◽  
Total Pressure ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Flow Speed ◽  
Secondary Flows ◽  
Experimental Results ◽  
Average Flow ◽  
Aspect Ratios ◽  
Good Agreement

An experimental study was made of the total pressure distribution in the corner secondary flow generated in two planar nozzles having different contours. Also, an analysis was made of the extent of the sidewall boundary layer migration caused by the cross flow and of its accumulation in the corner between the sidewall and horizontal nozzle walls at exits of planar nozzles. A comparison of the calculated and experimental results was made. Reasonably good agreement was found between the analytical and experimental results. The Reynolds numbers considered in this study, based on the average flow speed at nozzle exits and on the nozzle widths, were 5000, 10,000, and 20,000. The nozzle aspect ratios were 4 and 2.

Inducing Frictional Force to Enhance the Transient Response in Beams

2019 ◽  
Vol 22 (2) ◽  
pp. 88-93
Author(s):  
Hamed Khanger Mina ◽  
Waleed K. Al-Ashtrai
Keyword(s):  
Numerical Analysis ◽  
Transient Response ◽  
Frictional Force ◽  
Damping Ratio ◽  
Experimental Results ◽  
Damping Capacity ◽  
Tightening Force ◽  
Contact Areas ◽  
Good Agreement ◽  
Ansys Workbench

This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.

PHOTOINDUCED NONLINEAR OCTUPOLAR POLARIZATION: TRANSIENT AND PERMANENT REGIMES

1996 ◽  
Vol 05 (04) ◽  
pp. 653-670 ◽  
Author(s):  
CÉLINE FIORINI ◽  
JEAN-MICHEL NUNZI ◽  
FABRICE CHARRA ◽  
IFOR D.W. SAMUEL ◽  
JOSEPH ZYSS
Keyword(s):  
Theoretical Analysis ◽  
Second Harmonic ◽  
Experimental Results ◽  
Polar Field ◽  
Rotational Spectrum ◽  
Dual Frequency ◽  
One Dimensional ◽  
Ethyl Violet ◽  
Disperse Red 1 ◽  
Good Agreement

An original poling method using purely optical means and based on a dual-frequency interference process is presented. We show that the coherent superposition of two beams at fundamental and second-harmonic frequencies results in a polar field with an irreducible rotational spectrum containing both a vector and an octupolar component. This enables the method to be applied even to molecules without a permanent dipole such as octupolar molecules. After a theoretical analysis of the process, we describe different experiments aiming at light-induced noncentrosymmetry performed respectively on one-dimensional Disperse Red 1 and octupolar Ethyl Violet molecules. Macroscopic octupolar patterning of the induced order is demonstrated in both transient and permanent regimes. Experimental results show good agreement with theory.

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