• Korean Journal of Metals and Materials
• /
• v.46 no.6
• /
• pp.390-401
• /
• 2008

The objective of this study is to evaluate various machining characteristics of AlN-hBN machinable ceramics in micro end-milling process for its further application. First, AlN based machinable ceramics with hBN contents in the range of 10 to 20vol% were prepared by hot-pressing. Material properties of the composites, such as relative density, Vickers hardness, flexural strength, Young's modulus and fracture toughness were measured and compared. Then, micro end-milling experiments were performed to fabricate micro channels using prepared system. During the process, cutting forces, vibrations and AE signals were measured and analyzed using applied sensor system. Machined micro channel shapes and surface roughness were measured using 3D non-contact type surface profiler. From the experimental results, it can be observed that the cutting forces, vibrations and AE signal amplitudes decreased with increasing hBN contents. Also, measured surface roughness and profiles were improved with increasing hBN contents. As a result of this study, optimum machining conditions can be determined to fabricate desired products with AlN-hBN machinable ceramics based on the experimental results of this research.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.37 no.6
• /
• pp.637-643
• /
• 2024

One method to increase the output of solar modules is the application of the Half-cut technique, which requires a scribing process involving direct irradiation of infrared lasers on the solar cells. During this process, the laser melts the surface of the solar cells at high temperatures, enabling mechanical division, but this can lead to output loss due to thermal degradation caused by the laser. To minimize such losses, a low-temperature and low-loss division method has been devised. In this study, we compared the electrical characteristics and leakage currents affecting output degradation between the newly devised low-temperature and low-loss cell division method and the conventional laser division method. Additionally, we conducted a 3-point flexural test to evaluate the mechanical properties of both methods.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.1
• /
• pp.120-130
• /
• 1993

Generally, the machinability of materials that have a good mechanical properties is poor. For materials having a high strength, high toughness, high strength in high temperature and wear resistance, it is difficult to remove a chip from work materials. These properties are well shown in a Nickel, so this metal is used in machine materials, semi-conductor industry, metal mold and optical fields etc. But it is limitted in use because of high cost and poor machinability. In this study, the cutting of pure Nickel was conducted to examine wear of CBN, poly crystal diamond (PCD) and single crystal diamond (SCD) tools. From the result, the CBN tool is superior to poly crystal diamond tools or single crystal diamond tools in terms of tool wear and tool wear is predictable from experimental data base.

• Journal of the Korean Society of Food Culture
• /
• v.4 no.2
• /
• pp.167-172
• /
• 1989

Kimchi during fermentation with different periods of storage at room temperature were evaluated for the textural properties, titratable acidity, pH value and thickness of leaves in salting, during fermentation. Thickness of internal leaves in Korean cabbage were decreased of 50% for external leaves. but less decreased on the thickness of leaves in salting. Cutting force of leaves were increased with salting and during kimchi fermentation before 7 days. Stress (force vs area) in kimchi and Korean cabbage was same result of cutting force. Equation of pH change was y=-0.23x+6.13 (r=-0.97). Titratable acidity equation was y=0.09x-0.01(r=0.96). A desirable pH value and titratable acidity were 4.2 and 0.63% in kimchi fermentation.

• Journal of Korea Foundry Society
• /
• v.38 no.2
• /
• pp.32-40
• /
• 2018

Changes in the microstructures and mechanical properties of an AC2B alloy through solution heat treatment were investigated using recycled AC2B cutting chips as raw material. The as-cast microstructure of the AC2B alloy comprised ${\alpha}$-Al, $Al_2Cu$, and coarse needle-shaped phases considered to be eutectic Si and an Al-Fe-Si based intermetallic compound. After solution heat treatments at $505^{\circ}C$ for 1 h and 6 h, the samples showed complete dissolution of $Al_2Cu$ and relatively fine distribution of intermetallic compounds. Hardness test results showed that the hardness rapidly increased after the solution heat treatment for 1 h by solid solution hardening, and the increase of hardness exhibited a plateau from 1 h to 6 h. The results of the hardness and tensile tests showed that there was no visible difference in the effect of 1 h and 6 h solid solution treatment.

• Journal of Surface Science and Engineering
• /
• v.54 no.5
• /
• pp.230-237
• /
• 2021

In this study, the influence of silicon contents on the microstructure, mechanical and tribological properties of Ti-Al-Si-N coatings were systematically investigated for application of cutting tools. The composition of the Ti-Al-Si-N coatings were controlled by different combinations of TiAl₂ and Ti₄Si composite target powers using an arc ion plating technique in a reactive gas mixture of high purity Ar and N₂ during depositions. Ti-Al-Si-N films were nanocomposite consisting of nanosized (Ti,Al,Si)N crystallites embedded in an amorphous Si₃N₄/SiO₂ matrix. The instrumental analyses revealed that the synthesized Ti-Al-Si-N film with Si content of 5.63 at.% was a nanocomposites consisting of nano-sized crystallites (5-7 nm in dia.) and a three dimensional thin layer of amorphous Si₃N₄ phase. The hardness of the Ti-Al-Si-N coatings also exhibited the maximum hardness value of about 47 GPa at a silicon content of ~5.63 at.% due to the microstructural change to a nanocomposite as well as the solid-solution hardening. The coating has a low friction coefficient of 0.55 at room temperature against an Inconel alloy ball. These excellent mechanical and tribological properties of the Ti-Al-Si-N coatings could help to improve the performance of machining and cutting tool applications.

• Animal Bioscience
• /
• v.35 no.1
• /
• pp.39-46
• /
• 2022

Objective: The fermentation profile and silage quality of 3 Italian ryegrass (Lolium multiflorum Lam.) cultivars (cvs. Devis, Hellen, and Trinova) treated with 5 nitrogen doses (0, 50, 100, 150, and 200 kg/ha) were evaluated. Methods: The experiment was laid out in split plot in randomized complete block design with three replications. Annual ryegrass cultivars used in this study have been commonly grown in Turkey. Nitrogen doses were set in main plot and cultivars in split plot in the field. Plants were harvested at full-flowering stage with dry matter content about 220 g/kg for first cutting and 260 g/kg for second cutting. Harvested plants were chopped theoretically into 2 to 3 cm lengths for ensiling. Chopped fresh materials were ensilaged by compressing in 2 L plastic jars about 3±0.1 kg. Results: Effects of N doses on dry matter, neutral detergent fiber, acid detergent fiber, dry matter digestibility, relative feed value, crude protein, pH, ammonia nitrogen, lactic acid, acetic acid, and lactic acid/acetic acid were statistically significant while water soluble carbohydrate, ash and organic matter were not statistically different. Ammonia nitrogen, crude protein, ash, organic matter, lactic acid, and lactic acid/acetic acid were affected by cultivars, but the other parameters were not. Increasing nitrogen applications positively affected the chemical composition of annual ryegrass silage. The significant increase in protein content was remarkable, however, silage fermentation properties were adversely affected by the increasing nitrogen dose. Conclusion: It can be recommended 150 kg/ha nitrogen dose for annual ryegrass harvested at full blooming stage. Even though the silage fermentation properties of the used cultivars were similar, cv. Devis gave better results than the others in terms of silage pH and relative feed value.

• Proceedings of the KIEE Conference
• /
• 1996.07a
• /
• pp.196-198
• /
• 1996

The manufacturing process of the amorphous transformer core consists of winding, cutting, forming, annealing. Clamping of cores during this process are required for shape forming. Clamping of cores enhances the space factor, but degrades the magnetic properties and core loss characteristics of the cores. In this study, we investigated the optimal clamping pressure required in magnetic field annealing of 5 kVA amorphous transformer core.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.1
• /
• pp.61-70
• /
• 2004

Generally, ceramics are very difficult-to-cut materials because of its high strength and hardness. The machining process of ceramics can be characterized by cracking and brittle fracture. In the machining of ceramics, edge chipping and crack propagation are the principal reasons to cause surface integrity deterioration. Such phenomenon can cause not only poor dimensional and geometric accuracy, but also possible failure of the ceramic parts. Ceramics can be machined with traditional method such as grinding and polishing. However, such processes are generally cost-expensive and have low material removal rate. Thus, in this paper, to overcome these problems. BN powder, which gives good cutting property, is added for the fabrication of machinable ceramics by volume of 5,10,15,20,25 and 30%. And, mechanical properties, R-curve behavior and machining tests are carried out to evaluate the machining properties of the manufactured machinable ceramics.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1996.10a
• /
• pp.183-188
• /
• 1996

Films and coatings are used for an enormous and diverse set of applications including mechanical, electronic and optical devices, protection at high temperature, cutting tools enhancement and automotive use. Many of these applications require the various properties associated with inorganic and metallic / non-metallic materials; i.e., with ceramics. Therefore, a large number of coatings have been developed and used for a long time in the various fields, especially in mechanical one. As one of the mutual surface actions, the problems of contact stresses are complex. The relationship between load and stress are nonlinear. Besides, the material is often apt to deform plastically under low load. However, analytical solutions exist only for some simple problems. If a material has a complicated shape or inhomogeneous properties, numerical method must be used. In this paper, the analysis of the contact stress of the coating layer was solved, using the finite element method.