scholarly journals Sensitivity of Thermal Predictions to Uncertain Surface Tension Data in Laser Additive Manufacturing

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
J. Coleman ◽  
A. Plotkowski ◽  
B. Stump ◽  
N. Raghavan ◽  
A. S. Sabau ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Fluid Flow ◽  
Additive Manufacturing ◽  
Current Model ◽  
Surface Tension Gradient ◽  
Process Conditions ◽  
Conductive Heat ◽  
Melt Pool ◽  
Super Alloy

Abstract To understand the process-microstructure relationships in additive manufacturing (AM), it is necessary to predict the solidification characteristics in the melt pool. This study investigates the influence of Marangoni driven fluid flow on the predicted melt pool geometry and solidification conditions using a continuum finite volume model. A calibrated laser absorptivity was determined by comparing the model predictions (neglecting fluid flow) against melt pool dimensions obtained from single laser melt experiments on a nickel super alloy 625 (IN625) plate. Using this calibrated efficiency, predicted melt pool geometries agree well with experiments across a range of process conditions. When fluid mechanics is considered, a surface tension gradient recommended for IN625 tends to overpredict the influence of convective heat transfer, but the use of an intermediate value reported from experimental measurements of a similar nickel super alloy produces excellent experimental agreement. Despite its significant effect on the melt pool geometry predictions, fluid flow was found to have a small effect on the predicted solidification conditions compared to processing conditions. This result suggests that under certain circumstances, a model only considering conductive heat transfer is sufficient for approximating process-microstructure relationships in laser AM. Extending the model to multiple laser passes further showed that fluid flow also has a small effect on the solidification conditions compared to the transient variations in the process. Limitations of the current model and areas of improvement, including uncertainties associated with the phenomenological model inputs are discussed.

3D-Computer Simulation of Physical Transfer Process in Laser Molten Pool

2013 ◽  
Vol 341-342 ◽  
pp. 324-328 ◽  
Author(s):  
Bo Yang ◽  
Xi Chen Yang ◽  
Jian Bo Lei ◽  
Yun Shan Wang
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Computer Simulation ◽  
Fluid Flow ◽  
Molten Pool ◽  
Mathematic Model ◽  
Surface Tension Gradient ◽  
Drawing Force ◽  
Convection And Heat Transfer ◽  
3D Computer Simulation

The physical mathematic model for heat transfer and convection in laser molten pool established. 3D-computer simulation of temperature and fluid fields has been completed with finite difference method. It is shown that in laser molten pool there is a strong fluid flow, which is symmetrical in XY plane and anti symmetric in XZ plane. Due to effects of convection and heat transfer laser molten pool is widen. Surface tension gradient is the main drawing force for convection.

Effect of Time Spacing and Hatch Spacing on Thermal Material Properties and Melt Pool Geometry in Additive Manufacturing of S316L

2019 ◽  
Author(s):  
Elham Mirkoohi ◽  
Daniel E. Sievers ◽  
Steven Y. Liang
Keyword(s):  
Heat Transfer ◽  
Additive Manufacturing ◽  
Material Properties ◽  
Metal Additive Manufacturing ◽  
Melt Pool ◽  
Experimental Values ◽  
Melt Pool Size ◽  
Transfer Mechanisms ◽  
Hatch Spacing ◽  
Metal Additive

Abstract A physics-based analytical solution is proposed in order to investigate the effect of hatch spacing and time spacing (which is the time delay between two consecutive irradiations) on thermal material properties and melt pool geometry in metal additive manufacturing processes. A three-dimensional moving point heat source approach is used in order to predict the thermal behavior of the material in additive manufacturing process. The thermal material properties are considered to be temperature dependent since the existence of the steep temperature gradient has a substantial influence on the magnitude of the thermal conductivity and specific heat, and as a result, it has an influence on the heat transfer mechanisms. Moreover, the melting/solidification phase change is considered using the modified heat capacity since it has an influence on melt pool geometry. The proposed analytical model also considers the multi-layer aspect of metal additive manufacturing since the thermal interaction of the successive layers has an influence on heat transfer mechanisms. Temperature modeling in metal additive manufacturing is one of the most important predictions since the presence of the temperature gradient inside the build part affect the melt pool size and geometry, thermal stress, residual stress, and part distortion. In this paper, the effect of time spacing and hatch spacing on thermal material properties and melt pool geometry is investigated. Both factors are found statistically significant with regard to their influence on thermal material properties and melt pool geometry. The predicted melt pool size is compared to experimental values from independent reports. Good agreement is achieved between the proposed physics-based analytical model and experimental values.

Heat Transfer in Additive Manufacturing of Glass

2017 ◽  
Author(s):  
Junjie Luo ◽  
John M. Hostetler ◽  
Douglas A. Bristow ◽  
Robert G. Landers ◽  
Edward C. Kinzel ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Additive Manufacturing ◽  
Critical Parameter ◽  
Bubble Formation ◽  
Single Track ◽  
Melt Pool ◽  
Control Feedback ◽  
Laser Heated ◽  
Heated Filament ◽  
Simple Numerical Model

The temperature in the molten region is a critical parameter for Additive Manufacturing (AM) of transparent glass using a laser heated filament-fed processing. This paper presents a study of the heat transfer in single track printing of borosilicate glass using the filament-fed process. The incandescent radiation emitted from the melt pool is monitored using a spectrometer. The spectral data indicates the breakdown of materials occurring inside of the glass, and reflects the occurrence of bubble formation due to reboil at high temperatures. A simple numerical model of the filament-fed process based on an energy balance within the melt pool is used to estimate the temperature. By combining the numerical and experimental results, the estimated temperature calculated from this model is suitable for control feedback.

Development and Modeling of Melt Electrohydrodynamic-Jet Printing of Phase-Change Inks for High-Resolution Additive Manufacturing

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Chuang Wei ◽  
Jingyan Dong
Keyword(s):  
Surface Tension ◽  
Additive Manufacturing ◽  
High Resolution ◽  
Phase Change ◽  
Electrostatic Force ◽  
Droplet Diameter ◽  
Scaling Law ◽  
Process Conditions ◽  
Drop On Demand ◽  
Jet Printing

This paper presents the development and modeling a high-resolution electrohydrodynamic-jet (EHD-jet) printing process using phase-change ink (i.e., wax), which is capable of producing sub-10 μm footprints (sub-10 fL in volume) for super-resolution additive manufacturing. In this study, we successfully apply EHD-jet printing for phase-change ink (wax), which is widely used as modeling and supporting material for additive manufacturing, to achieve micron-scale features. The resolution for single droplet on substrate is around 5 μm with the thickness in the range of 1–2 μm, which provides great potential in both high-resolution 3D printing and 2D drop-on-demand microfabrication. The droplet formation in EHD printing is modeled by finite element analysis (FEA). Two important forces in EHD printing, electrostatic force and surface tension force, are modeled separately by FEA. The droplet size is obtained by balancing the electrostatic force and surface tension of the pending droplets around meniscus apex. Furthermore, to predict the droplet dimension at different process conditions, a dimensionless scaling law is identified to describe the relationship between dimensionless droplet diameter and modified nondimensional electrical bond number. Finally, the droplets in-flight velocity and impact characteristics (e.g., Reynolds number and Weber number) are modeled using the results from FEA analysis.

Inverse-thermocapillary evaporation in a thin liquid film of self-rewetting fluid

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Elaine Lim ◽  
Tze Cheng Kueh ◽  
Yew Mun Hung
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Liquid Film ◽  
Temperature Region ◽  
Thin Liquid Film ◽  
Thermocapillary Flow ◽  
Working Fluid ◽  
Surface Tension Gradient ◽  
Thermocapillary Effect ◽  
Content Type

Purpose The present study aims to investigate the inverse-thermocapillary effect in an evaporating thin liquid film of self-rewetting fluid, which is a dilute aqueous solution (DAS) of long-chain alcohol. Design/methodology/approach A long-wave evolution model modified for self-rewetting fluids is used to study the inverse thermocapillary characteristics of an evaporating thin liquid film. The flow attributed to the inverse thermocapillary action is manifested through the streamline plots and the evaporative heat transfer characteristics are quantified and analyzed. Findings The thermocapillary flow induced by the negative surface tension gradient drives the liquid from a low-surface-tension (high temperature) region to a high-surface-tension (low temperature) region, retarding the liquid circulation and the evaporation strength. The positive surface tension gradients of self-rewetting fluids induce inverse-thermocapillary flow. The results of different working fluids, namely, water, heptanol and DAS of heptanol, are examined and compared. The thermocapillary characteristic of a working fluid is significantly affected by the sign of the surface tension gradient and the inverse effect is profound at a high excess temperature. The inverse thermocapillary effect significantly enhances evaporation rates. Originality/value The current investigation on the inverse thermocapillary effect in a self-rewetting evaporating thin film liquid has not been attempted previously. This study provides insights on the hydrodynamic and thermal characteristics of thermocapillary evaporation of self-rewetting liquid, which give rise to significant thermal enhancement of the microscale phase-change heat transfer devices.

Condensate Drop Movement on Heat Transfer Surface With Bulk Temperature Gradient in Marangoni Dropwise Condensation

2010 ◽  
Author(s):  
Zhihao Chen ◽  
Yoshio Utaka
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Temperature Gradient ◽  
Heat Transfer Surface ◽  
Surface Tension Gradient ◽  
Bulk Temperature ◽  
Dropwise Condensation ◽  
Wide Range ◽  
Initial Drop ◽  
Temperature Side

When a bulk temperature gradient was applied to a horizontal condensing surface in Marangoni dropwise condensation, the spontaneous movement of condensate drops occurred. The characteristics of the condensate drop movement in a condensate system of water and ethanol binary vapor mixture were experimentally investigated for a wide range of bulk temperature gradients and for various mass fractions. Drops moved from the low-temperature side to the high-temperature side of the heat transfer surface. When the initial drop distance was adopted as a parameter for the Marangoni force acting on the condensate drop together with the surface tension gradient corresponding to the surface temperature of the condensing surface, the drop moving velocity correlated well as a function of both the surface tension gradient and the initial drop distance. In the range of larger initial drop distances, the condensate drop velocity increases as the initial drop distance is reduced and it subsequently decreases after the velocity reaches its maximum value under an almost constant bulk surface tension gradient.

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