scholarly journals Directional Bouncing of Impacting Droplets on Non-Uniform Rough Surfaces with High Temperature

2021 ◽  
Vol 261 ◽  
pp. 02030
Author(s):  
Kuan Sun ◽  
Cong Liu ◽  
Shile Feng ◽  
Yahua Liu
Keyword(s):  
Surface Roughness ◽  
High Temperature ◽  
304 Stainless Steel ◽  
Film Boiling ◽  
Laser Etching ◽  
Directional Movement ◽  
Leidenfrost Temperature ◽  
Droplet Impacts ◽  
Directional Transport ◽  
Main Factor

Directional transport of high-temperature droplets enjoys broad application prospects in the fields of drag reduction and heat transfer. In this paper, two adjacent regions with different surface roughness were constructed on 304 stainless steel by laser etching to control the directional movement of high-temperature droplets. It is found that the regions with different surface roughness have different Leidenfrost temperatures, and the Leidenfrost temperature is lower under smaller roughness. When the droplet hits the boundary of the adjacent regions at high temperatures, it will bounce towards the region with larger roughness spontaneously, and the directional bouncing distance tends to first increase and then decrease with the increase of temperature and Weber number. In addition, when the droplet impacts at the boundary of the adjacent regions which have different Leidenfrost temperatures, the two parts of the droplet will be in transition boiling and film boiling respectively. The resulting Young’s force is the main factor that drives the droplets to bounce directionally.

Superconducting Wind Generators with Capacities of 10 MW and Larger

2020 ◽  
Vol 10 (10) ◽  
pp. 59-67
Author(s):  
Victor N. ANTIPOV ◽  
◽  
Andrey D. GROZOV ◽  
Anna V. IVANOVA ◽  
◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Wind Power ◽  
State Of The Art ◽  
Superconducting Materials ◽  
Commercial Application ◽  
Synchronous Generators ◽  
High Temperature Superconducting ◽  
Wind Generators ◽  
Main Factor

The overall dimensions and mass of wind power units with capacities larger than 10 MW can be improved and their cost can be decreased by developing and constructing superconducting synchronous generators. The article analyzes foreign conceptual designs of superconducting synchronous generators based on different principles: with the use of high- and low-temperature superconductivity, fully superconducting or only with a superconducting excitation system, and with the use of different materials (MgB2, Bi2223, YBCO). A high cost of superconducting materials is the main factor impeding commercial application of superconducting generators. In view of the state of the art in the technology for manufacturing superconductors and their cost, a conclusion is drawn, according to which a synchronous gearless superconducting wind generator with a capacity of 10 MW with the field winding made of a high-temperature superconducting material (MgB2, Bi-2223 or YBCO) with the «ferromagnetic stator — ferromagnetic rotor» topology, with the stator diameter equal to 7—9 m, and with the number of poles equal to 32—40 has prospects for its practical use in the nearest future.

Effect of SiC-Cu Electrode on Material Removal Rate, Tool Wear and Surface Roughness in EDM Process

2020 ◽  
Vol 38 (9A) ◽  
pp. 1406-1413
Author(s):  
Yousif Q. Laibia ◽  
Saad K. Shather
Keyword(s):  
Surface Roughness ◽  
Tool Wear ◽  
Material Removal Rate ◽  
Material Removal ◽  
Electrical Discharge Machining ◽  
Removal Rate ◽  
304 Stainless Steel ◽  
Tool Electrode ◽  
Pulse Time ◽  
Edm Process

Electrical discharge machining (EDM) is one of the most common non-traditional processes for the manufacture of high precision parts and complex shapes. The EDM process depends on the heat energy between the work material and the tool electrode. This study focused on the material removal rate (MRR), the surface roughness, and tool wear in a 304 stainless steel EDM. The composite electrode consisted of copper (Cu) and silicon carbide (SiC). The current effects imposed on the working material, as well as the pulses that change over time during the experiment. When the current used is (8, 5, 3, 2, 1.5) A, the pulse time used is (12, 25) μs and the size of the space used is (1) mm. Optimum surface roughness under a current of 1.5 A and the pulse time of 25 μs with a maximum MRR of 8 A and the pulse duration of 25 μs.

EFFECT OF ABRASIVE TYPE ON THE SURFACE ROUGHNESS AND MRR IN MAF OF AISI 304 STEEL

2021 ◽  
Author(s):  
MAHMUT ÇELIK ◽  
HAKAN GÜRÜN ◽  
ULAŞ ÇAYDAŞ
Keyword(s):  
Surface Roughness ◽  
Removal Rate ◽  
Three Dimensional ◽  
Steel Plates ◽  
304 Stainless Steel ◽  
Average Surface Roughness ◽  
Machining Time ◽  
Aisi 304 ◽  
Average Surface ◽  
Different Levels

In this study, the effects of experimental parameters on average surface roughness and material removal rate (MRR) were experimentally investigated by machining of AISI 304 stainless steel plates by magnetic abrasive finishing (MAF) method. In the study in which three different abrasive types were used (Al2O3, B4C, SiC), the abrasive grain size was changed in two different levels (50 and 80[Formula: see text][Formula: see text]m), while the machining time was changed in three different levels (30, 45, 60[Formula: see text]min). Surface roughness values of finished surfaces were measured by using three-dimensional (3D) optical surface profilometer and surface topographies were created. MRRs were measured with the help of precision scales. The abrasive particles’ condition before and after the MAF process was examined and compared using a scanning electron microscope. As a result of the study, the surface roughness values of plates were reduced from 0.106[Formula: see text][Formula: see text]m to 0.028[Formula: see text][Formula: see text]m. It was determined that the best parameters in terms of average surface roughness were 60[Formula: see text]min machining time with 50[Formula: see text][Formula: see text]m B4C abrasives, while the best result in terms of MRR was taken in 30[Formula: see text]min with 50[Formula: see text][Formula: see text]m SiC abrasives.

Introduction of high tensile strain into Ge-on-Insulator structures by oxidation and annealing at high temperature

2021 ◽  
Author(s):  
Xueyang Han ◽  
ChiaTsong Chen ◽  
Cheol-Min Lim ◽  
Kasidit Toprasertpong ◽  
Mitsuru Takenaka ◽  
...  
Keyword(s):  
Surface Roughness ◽  
High Temperature ◽  
Wafer Bonding ◽  
Present Method ◽  
Thermal Process ◽  
Tensile Strain ◽  
Process Condition ◽  
Thermal Expansion Mismatch ◽  
Physical Origin ◽  
N2 Annealing

Abstract It is demonstrated in this work that a high temperature thermal process including oxidation and N2 annealing at 850 oC can provide tensile strain of ~0.58 % at maximum into Ge-on-Insulator (GOI) structures without any special patterning or external stressors. The different impacts of oxidation and annealing on tensile strain generation, surface roughness and crystal qualities in the GOI structures fabricated by Ge condensation and wafer bonding are systematically examined. Tensile strain of 0.47 % is achieved without severe thermal damages under the optimal thermal process condition, which indicates the high potential of the present method for improving the performance of GOI n-channel MOSFETs. The influence of thermal expansion mismatch between Ge and SiO2 are suggested as a possible physical origin of high amount of tensile strain into GOI structures.

scholarly journals Study of Optimum Cutting While Lathing Carbonate Steel VCN-150 Uses a Layered Carbide Chisel PVD on Dry and Wet Condition

2018 ◽  
Vol 7 (2.13) ◽  
pp. 389
Author(s):  
Muksin R. Harahap ◽  
Ahmad Bakhori ◽  
Suhardi Napid ◽  
Muhammad Rafiq Yanhar ◽  
Abdurrozzaq Hasibuan
Keyword(s):  
Surface Roughness ◽  
High Temperature ◽  
Carbon Steel ◽  
Dry Cutting ◽  
Surface Method ◽  
Significant Difference ◽  
Optimum Cutting ◽  
Wet Condition

To improve the productivity of this machining perhaps it may be recommended in a dry cutting but a dry cutting is recognized very sensitive to a high temperature. In this case, in order to overcome is perhaps required by using a tool carbide either in layers or without any layers whereby each layer has certain superior. There was conducted an experiment to have an optimum cutting on a carbon steel VCN-150 using a layers tool carbide  and Respond Surface Method (RSM) with a CCD operation. The result of study recommended that condition optimum cutting shall be achieved (When cutting tc ) on a medium machining refers to ISO 3685 and medium surface roughness (Ra ) ISO 1320. Statistically, there is no found significant difference between a dry and wet cutting on optimum dry condition.  

Manganese Effect on Isothermal High Temperature Oxidation Behaviour of AISI 304 Stainless Steel

2008 ◽  
Vol 595-598 ◽  
pp. 1127-1134 ◽  
Author(s):  
Frédéric Riffard ◽  
Henri Buscail ◽  
F. Rabaste ◽  
Eric Caudron ◽  
Régis Cueff ◽  
...  
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Oxide Scale ◽  
304 Stainless Steel ◽  
Initial Growth ◽  
Aisi 304 Stainless Steel ◽  
Protective Oxide ◽  
Temperature Oxidation ◽  
Aisi 304

Chromia-forming steels are excellent candidates to resist to high temperature oxidizing atmospheres because they form protective oxide scales. The oxide scale growth mechanisms are studied by exposing AISI 304 stainless steel to high temperature conditions in air, and the analyses were carried out by means of thermogravimetry and in situ X-rays diffraction. The in situ XRD analyses carried out during high temperature AISI 304 steel oxidation in air reveals the accelerated growth of iron-containing oxides such as hematite Fe2O3 and iron-chromite FeCr2O4, when the initial germination of the oxide layer contains the presence of a manganese-containing spinel compound (1000°C). When the initial growth shows the only chromia formation (800°C), hematite formation appears differed in time. Protection against corrosion is thus increased when the initial germination of manganese-containing spinel oxide is inhibited in the oxide scale.

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