Numerical Analysis of Effect of Different Initial Morphologies on Molten Pool Flows

2020 ◽  
Vol 861 ◽  
pp. 491-498
Author(s):  
Kai Li ◽  
Zhen Yu Zhao ◽  
Hou Ming Zhou ◽  
Hao Zhou ◽  
Jing Cheng Jin
Keyword(s):  
Heat Transfer ◽  
Flow Velocity ◽  
Molten Pool ◽  
Flow Characteristics ◽  
Polished Surface ◽  
Initial Shape ◽  
Factors Affecting ◽  
Smooth Plane ◽  
Surface Morphologies

The different initial morphologies of polished surface is one of the important factors affecting the quality of laser polishing. In order to investigate the flow characteristics of the molten pool with different morphologies, a two-dimensional (2D) axisymmetric numerical model is established based on the COMSOL software. The nonisothermal flow interface is used to couple the heat transfer and fluid flow, and simulate the evolution process of the molten pool with three different surface morphologies. The results show that the initial shape is a smooth plane, the flow velocity of the molten pool is stable and always in thermocapillary regime, then the protrusions were generated at the edge of the molten pool. Likewise, with the increase of the surface curvature, the capillary becomes the main driving force to eliminate the surface asperities. While the flow velocity and instability of the molten pool enhance, and the depth of the molten pool increases with the heat transfer generated by the mass flow along the z-axis direction.

scholarly journals In-Situ Laser Polishing Additive Manufactured AlSi10Mg: Effect of Laser Polishing Strategy on Surface Morphology, Roughness and Microhardness

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 393
Author(s):  
Jiantao Zhou ◽  
Xu Han ◽  
Hui Li ◽  
Sheng Liu ◽  
Shengnan Shen ◽  
...  
Keyword(s):  
Surface Quality ◽  
Molten Pool ◽  
Surface Defects ◽  
Polished Surface ◽  
Transient Model ◽  
Surface Evolution ◽  
Powder Bed ◽  
Laser Polishing ◽  
Surface Morphologies

Laser polishing is a widely used technology to improve the surface quality of the products. However, the investigation on the physical mechanism is still lacking. In this paper, the established numerical transient model reveals the rough surface evolution mechanism during laser polishing. Mass transfer driven by Marangoni force, surface tension and gravity appears in the laser-induced molten pool so that the polished surface topography tends to be smoother. The AlSi10Mg samples fabricated by laser-based powder bed fusion were polished at different laser hatching spaces, passes and directions to gain insight into the variation of the surface morphologies, roughness and microhardness in this paper. The experimental results show that after laser polishing, the surface roughness of Ra and Sa of the upper surface can be reduced from 12.5 μm to 3.7 μm and from to 29.3 μm to 8.4 μm, respectively, due to sufficient wetting in the molten pool. The microhardness of the upper surface can be elevated from 112.3 HV to 176.9 HV under the combined influence of the grain refinement, elements distribution change and surface defects elimination. Better surface quality can be gained by decreasing the hatching space, increasing polishing pass or choosing apposite laser direction.

scholarly journals Flow and Mass Transfer Performance in Short Pin-Fin Channels with Different Fin Shapes

1998 ◽  
Vol 4 (2) ◽  
pp. 113-128 ◽  
Author(s):  
R. J. Goldstein ◽  
S. B. Chen
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Flow Velocity ◽  
Pressure Loss ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Flow Characteristics ◽  
Pin Fin ◽  
Pin Fin Arrays

The mass transfer (analogous to heat transfer) and pressure loss characteristics of staggered short pin-fin arrays are investigated experimentally in the range of Reynolds number 3000 to 18,000 based on fin diameter and mean approach-flow velocity. Three different shapes of fins with aspect ratio of 2 are examined: one uniform-diameter circular fin (UDCF) and two stepped-diameter circular fins (SDCF1 and SDCF2). Flow visualization using oil-lampblack reveals complex flow characteristics associated with the repeated production of horseshoe vortices and fin wakes, and the interactions among these. The SDCF1 and SDCF2 arrays show flow characteristics different from the UDCF array due to downflow from the steps. For all arrays tested, the near-endwall flow varies row by row in the initial rows until it reaches a stable pattern after the third row. The row-averaged Sherwood numbers obtained from the naphthalene sublimation experiment also show a row-by-row variation pattern similar to the flow results. While the SDCF2 array has the highest mass transfer rate, the SDCF1 array has the smallest pressure loss at the same approach-flow velocity. The fin surfaces have higher array-averaged Sherwood number than the endwall and the ratio between these changes with fin shape and Reynolds number. The performance of the pin-fin arrays is analyzed under two different constraints: the mass[heat transfer rate at fixed pumping power, and the mass/heat transfer area and pressure loss to fulfill fixed heat load at a fixed mass flow rate. In both cases, the SDCF2 array shows the best performance.

Investigation on the relationship between bending angle of the overhanging surface and overhanging surface quality printed using selective laser melting

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Weipeng Duan ◽  
Jitai Han ◽  
Qingfneg Xia ◽  
Keqing Wang ◽  
Meiping Wu ◽  
...  
Keyword(s):  
Surface Quality ◽  
Molten Pool ◽  
Bending Angle ◽  
Content Type ◽  
Factors Affecting ◽  
Overall Performance ◽  
Increasing Demand ◽  
The Relationship ◽  
Bending Angles

Purpose With the increasing demand for lightweight parts, the quality of the inner structure gained growing attention from different kinds of fields. As the quality of the overhanging surface was one of the most important factors affecting inner structure formation, its quality still needs to improve. This paper aims to clarify the change of the overhanging surface quality caused by different bending angles. Design/methodology/approach The structure of the inner hole was redesigned according to the different performances of the overhanging and side inner surface. The experimental results revealed why different surface qualities can be seen under different bending angles. According to the experimental data, the inner structure was redesigned to increase its overall performance. Findings The results revealed that when the bending angle was small, the slope of the overhanging surface increased which lead to the decreasing length of the powder-supported layer. However, less space on bending angle resulted in the accumulation of unmelted powder which leads to the increasing of sinking distance. When the bending angle was too large, the slope of the overhanging surface decreased and the length of the molten pool which was supported by powder increased. It resulted in the sinking of the molten pool caused by the gravity of powder and its attachment. Originality/value This paper is the first work to study the relationship between bending angle and overhanging surface quality as far as the authors know. The different performances of left and right overhanging surfaces also have not been revealed in other research studies to the best of the knowledge.

Customer’s satisfaction on service quality at Vietnam Technological and Commercial Joint Stock Bank – An Giang Branch

2020 ◽  
Vol 4 (3) ◽  
pp. First
Author(s):  
Tran Minh Hieu ◽  
Nguyen Duong Ngoc Mai Chi
Keyword(s):  
Customer Satisfaction ◽  
Service Quality ◽  
Test Method ◽  
Quality Of Services ◽  
Factors Affecting ◽  
Factors Influencing ◽  
Alpha Reliability ◽  
Survey Results ◽  
Development Orientation

This study applied SERVQUAL scale of Parasuraman et al to measure factors affecting customer satisfaction on service quality at Vietnam Technological and Commercial Joint Stock Bank - An Giang Branch (Techcombank An Giang). The study was conducted to survey 207 customers who have been using the service at Techcombank An Giang. The survey results were analyzed by the Cronbach's Alpha reliability test method, then used Exploratory factor analysis (EFA) to verify and evaluate the scale of service quality. The results of the regression analysis show that customer's satisfaction about service quality at Techcombank An Giang includes four factors: The factor with the highest level is the Empathy with Beta = 0.253, the second of factor is the Responsibility with Beta = 0.248, ranked third in the influence level is the Tangible with Beta = 0.235, and the lowest impact level is the Reliability with Beta = 0.144. The research also uses statistical methods to describe and test the differences of demographic factors with customer's satisfactionon service quality.The analysis results show that there is no difference between customer's satisfaction on service quality and factors such as gender, age, income, number of transaction banks, regular transaction banks, and time to use the service at Techcombank An Giang. Through the research results, the author would like to propose some ideas to improve the quality of services, thereby attracting new customers and importantly, keeping traditional customers because the development orientation of Techcombank is to take care of old customers to cross sell other products of the bank. The Stud results offer a basis for the branch to identify the factors influencing customer satisfaction on their service quality, thereby having an appropriate strategy to improve customer satisfaction.

THE STUDY ON TA VAT WINE PRODUCTION FROM SUGAR PALM (ARENGA PINNATA) SAP

2014 ◽  
Vol 83 (5) ◽  
Author(s):  
Nguyễn Thị Hồng Thu ◽  
Đặng Minh Nhật ◽  
Nguyễn Hoàng Dung
Keyword(s):  
Room Temperature ◽  
Fermentation Process ◽  
Inoculum Size ◽  
Wine Fermentation ◽  
Wine Production ◽  
Factors Affecting ◽  
Natural Fermentation ◽  
Tropical Asia ◽  
Best Parameters

Sugar palm (Arenga pinnata) is a feather palm native to tropical Asia. In Vietnam, it is named Búng Báng or Đoác and grown only on the highlands in the central or northern part of Vietnam. It is utilized for many purposes, especially for Ta Vat wine production - a characteristic and unique product of Co Tu ethnic minority. However, because of the natural fermentation used in the production, the product quality is inconsistent. The purpose of this study was to examine a new procedure of using palm sap for making Ta Vat wine. Some characteristics of the sap, which was collected at Nam Giang district, Quang Nam province are determined, proving the potential of the sap for making wine product. The quality of sap changes quickly at room temperature. At low temperature (4 - 60C), the changes in sap quality are apparently slower. Examining some factors affecting its quality during the wine fermentation process, we determined the best parameters for the fermentation process as follows: inoculum size of 3% with cell density of about 1x108 cells/ml, the addition of the extract from the bark of Ceylon ironwood (Mesua ferrea L.) 4%. Keywords: Arenga pinnata, sap, Ceylon ironwood bark, Mesua ferrea L., wine fermentation.

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