KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 6 of 6

Some of the metrics are blocked by your
consent settings
Enhancing ductility of sintered Fe-Ni-Mo-Mn-Si-C alloy by Co addition
(2024-05-17)
Putsaccada, Viseth
;
Wongsa-Ngam, Jittraporn
;
Ohtake, Naoto
;
Morakotjinda, Monnapas
;
Krataithong, Rungtip
This research aims to investigate the effect of cobalt (Co) on accelerating the bainitic transformation in sintered Fe-Ni-Mo-Mn-Si-C alloys. Experimental sintered specimens were prepared from the mixtures of pre-alloyed Fe-4.00Ni-0.50Mo-0.2Mn powder with a fixed 4.00 wt% silicon carbide and varied Co contents (0.50 to 3.00 wt%) using a traditional press and sinter process. Sintering was conducted in a vacuum furnace at 1250 °C for 45 minutes and under slow cooling in the sintering furnace. It was found that Co strongly influenced the kinetics of bainite transformation in sintered Fe-Ni-Mo-Si-C-(Co) alloys. Tensile strength and hardness of sintered alloys increased with Co content. High elongation values were obtained in sintered specimens with high Co contents. The increases of tensile strength and ductility with Co content were attributed to accelerated bainitic ferrite formation and retained austenite stability, respectively.
Some of the metrics are blocked by your
consent settings
Physicomechanical Characteristics of Carbon Fiber Reinforced Polymer Composite Using X-Ray Diffraction, Atomic Force and Electron Microscopies
(2022-10-01)
Lin, Ye Htet
;
Karin, Preechar
;
Larpsuriyakul, Patcharee
;
Ohtake, Naoto
The physicomechanical characteristics of PAN-based carbon fibers were investigated by SEM-EDS, XRD, TEM and AFM analysis while the mechanical properties of the composites were studied by tensile, flexural and Charpy impact tests with ASTM standards. Regarding the tensile test of carbon fiber fabric, the average tensile strength of CF-I, CF-II and CF-III fibers were around 147 MPa, 137 MPa and 225 MPa and the tensile modulus of those were 12.8 GPa, 13.2 GPa and 12.8 GPa, respectively. Later, the nanostructure of carbon fiber was recognized not as a pure graphite carbon structure because they mixed with graphite and amorphous structures. The higher tensile strength and modulus of CF-III fiber fabric was lower interlayer spacing (d002) because it consisted of more graphene layers in the graphite structure when compared with CF-I and CF-II fiber fabrics. Concerning AFM analysis’s results, CF-I fiber fabric has higher surface roughness (Ra) of 34.8 nm and more in-depth with wider pit lines along the fiber axis, which caused higher mechanical properties among the three composites. According to this article, the nanostructure of carbon fibers had a lower impact on CFRP composite because the interfacial bonding between fiber and epoxy matrix, which obtained the higher mechanical properties in the composite, was directly enhanced by the higher surface roughness of the fibers.
Some of the metrics are blocked by your
consent settings
A Study on Curing Temperature and Fracture Mechanism of Carbon and Glass Fiber Reinforced Polymers Using an Electron Microscopy
(2021-06-01)
Man, Tial Cuai
;
Karin, Preechar
;
Lin, Ye Htet
;
Larpsuriyakul, Patcharee
;
Ohtake, Naoto
The morphology and nanostructure of carbon and glass fiber are investigated by using XRD, SEM and TEM analysis. The composites are divided into three groups which consists of “without post-curing”, “post-cured at 80 °C for 6 hrs” and “post-cured at 120 °C for 3 hrs” to investigate curing temperature effect. The mechanical properties of composites are tested in the indentation, tensile, and flexural machine with ASTM standard. According to the results, the hardness of post-curing of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) are increased approximately three-times and 5 % compared to with and without post-curing process. The tensile strength of CFRP and GFRP are approximately 458 MPa and 385 MPa, while post-cured at 120 °C for the three-hour results are 490 MPa and 433 MPa respectively. In contrast, composites of treated fiber are not improved mechanical strength significantly for CFRP, while GFRP are slightly increased by 7 %. On the other hand, the flexural strength of treated carbon and glass fiber of composite are increased to 3 % and 15 % respectively. Higher temperature and treated fiber composites of carbon fiber are not significantly improved because high temperature curing and treated fiber created more porous to occur fracture internally.
Some of the metrics are blocked by your
consent settings
Dry-sliding wear of the 316L/h-BN composites produced under crack ammonia atmosphere
(2020-01-01)
Chusong, Ekkarat
;
Kansuwan, Panya
;
Ohtake, Naoto
;
Wila, Pongsak
;
Tosangthum, Nattaya
Wear is one of different problems in mechanical failures of moving components. When a component encounters friction force on its surface, crack initiation tends to occur and wear follows crack propagation. Thus, the moving parts of automobiles should have proper wear resistance for long-time services, in addition to having high strength and hardness for heavy load operation. A self-lubricating material with compromised tribological and mechanical properties is important for some moving components. In this work, self-lubricating composites, metal matrix composites embedded with a solid lubricant, made from 316L stainless steel powder mixed with different hexagonal boron nitride (h-BN) contents of 10%, 15% and 20% by volume. The mixed powders were compacted into green parts (according with MPIF Standard 42) with density of 6.5 g·cm<sup>-3</sup>. Then, the green parts were sintered at 1100, 1150, 1200, 1250 and 1300°C under cracked ammonia (75% H<inf>2</inf>+25% N<inf>2</inf>) atmosphere for 60 min. The experimental results revealed that increases of hardness and strength sintered 316L matrix by reduction of pore amount and size were due to the increase of sintering temperature. However, the increase of h-BN content resulted in increase of pore amount and size. Additions of h-BN content up to 20 vol. % reduced friction coefficient of the sintered composites. At sintering temperatures of equal to and higher than 1200°C, h-BN did not react with 316L stainless steel powders to form intergranular boride phase. The sintered composites produced under the maximum experimental sintering temperature of 1300°C showed low specific wear rate.
Some of the metrics are blocked by your
consent settings
Characterization of carbon fiber and glass fiber's micro and nanostructure using electron microscopy, raman spectroscopy and xrd analysis
(2019-03-25)
Man, Tial Cuai
;
Karin, Preechar
;
Ohtake, Naoto
;
Aakasaka, Hiroki
;
Larpsuriyakul, Patcharee
Nowadays, most manufacturers are looking for the improvement of lightweight parts and other components in the automobile field. Carbon fiber and glass fiber are the most effective materials for their requirement to reduce the weight in vehicles due to their light weight and high tensile strength. The diameter of carbon fiber is 6 μm while glass fiber diameter is 17 μm. The mechanical tensile force of carbon fiber and glass fiber are 430 N and 290 N respectively on fiber alone without matrix. Carbon fibers are gradually smaller in each filament due to tensile force. Approximately 5 mm are elongated for both carbon fiber and glass fiber in tensile test report. In current research, characteristic and tensile force of carbon fiber and glass fiber were investigated by using electron microscopy, Raman spectroscopy and XRD.
Some of the metrics are blocked by your
consent settings
Production of low impurity aluminium rotor for motor efficiency enhancement
(2018-08-14)
Payakkapol, Savitri
;
Chayopitak, Nattapon
;
Kunsuwan, Panya
;
Ohtake, Naoto
;
Srimanosaowapak, Sompong
Induction motors have been widely used in various electrical applications. However, their efficiency are still limited due to losses occurring during operation, especially for smaller ratings. Higher the electrical conductivity of motor rotor by lower its impurity content is one of practical and simple way to improve motor efficiency. The aim of this work is to reduce the impurity content of aluminium rotor by addition of boron in the form of Al-5wt%B master alloy and Na<inf>2</inf>B<inf>4</inf>O<inf>7</inf>-NaCl-KCl flux, and then sedimention of their precipitated particles. The purer melt was then cast as rotors for single-phase induction motors. With the amount of addition of boron in aluminium melt in this work, boron in Al-5wt%B master alloy was more pronounced in removing impurities in aluminium melt than that in Na<inf>2</inf>B<inf>4</inf>O<inf>7</inf>. It was found that the rotors made of aluminium melt with lower impurity contents and hence higher electrical conductivity resulted in more enhancement of motor efficiency.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results