• International Journal of Precision Engineering and Manufacturing
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• v.9 no.2
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• pp.63-68
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• 2008

Hard and brittle materials, such as Ni- and Ti-based alloys, glass, and ceramics, are very useful in aerospace, marine, electronics, and high-temperature applications because of their extremely versatile mechanical and chemical properties. One Ni-based alloy, Inconel 718, is a precipitation-hardenable material designed with exceptionally high yield strength, ultimate tensile strength, elastic modulus, and corrosion resistance with outstanding weldability and excellent creep-rupture properties at moderately high temperatures. However, conventional machining of this alloy presents a challenge to industry. Ultrasonic vibration cutting (UVC) has recently been used to cut this difficult-to-machine material and obtain a high quality surface finish. This paper describes an experimental study of the UVC parameters for Inconel 718, including the cutting force components, tool wear, chip formation, and surface roughness over a range of cutting conditions. A comparison was also made between conventional turning (CT) and UVC using scanning electron microscopy observations of tool wear. The tool wear measured during UVC at low cutting speeds was lower than CT. UVC resulted in better surface finishes compared to CT under the same cutting conditions. Therefore, UVC performed better than CT at low cutting speeds for all measures compared.

• International Journal of Concrete Structures and Materials
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• v.6 no.4
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• pp.247-250
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• 2012

Composites are somewhat more difficult to model than an isotropic material such as iron or steel due to the fact that each layer may have different orthotropic material properties. In finite element literature the asphalt mixes are represented by using rectangular meshes, not the actual picture of their cross-sections. Asphalt aggregate size and distribution in the asphalt concrete sample, aggregate shape, and fractured surface effects are ignored. In this research, the actual image of the sample including all these effects were directly considered in the finite element. The samples, were cut into cross-sections and were scanned. The image-processing toolbox of Labview was utilized in obtaining the rectangular gray images of the scanned images. In the rectangular sample the aggregates were white and the asphalt binders were black. The grayscale images were converted by LABVIEW into the format required by ANSYS as an input file, with the same dimensions. The nodes at the bottom of the model were constrained in both x and y directions. Left and right edges were symmetry and top was free. Certain amount of pressure was applied along the top surface to simulate the tire pressure.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.93-98
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• 2019

Recently, with the development of the aerospace and automotive industries, the demand for high-melting-point materials has increased. However, high-melting-point materials are difficult to cut through conventional machining methods. Thermally assisted machining (TAM) is a method for improving the machinability by preheating the materials. A laser, the most commonly used device for TAM, has high efficiency through local preheating but is not sufficient for maintaining a high preheating temperature due to rapid cooling. However, the use of multi-heat sources can supplement the disadvantage of a single heat source. The high preheating temperature can be maintained with a wide and deep heat-affected zone (HAZ) by multi-heat sources. The purpose of this study is to analyze the preheating effects of multi-heat sources using laser plasma. Thermal analysis and preheating experiments were carried out. As a result, the high preheating effect of multi-heat sources compared with a single heat source was verified.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.6
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• pp.1-6
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• 2017

Recently, the brittle materials such as ceramics, glass, sapphire and textile material have been widely used in semiconductors, aerospace and automobile owing to high functional characteristics. On the other hand, it has the characteristics of difficult-to-cut material relative to all materials. In this study, diamond electro-deposited band-saw machine was developed to operate stably using water-coolant type through relative motion between band-saw tool and $Al_2O_3$ material. High densified $Al_2O_3$ material was manufactured by spark plasma sintering method. The bulk density was observed by the Archimedes law and the theoretical density was estimated to be $3.88g/cm^3$ and its hardness 14.7 MPa. From the dicing sawing test of $Al_2O_3$ specimen, behavior of surface roughness and band-saw wear are dominantly affected by the increase of the band-saw linear velocity. Additionally, an continuous pattern type of diamond band-saw was a very effective due to entry impact as a one-off for brittle material.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.6
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• pp.445-451
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• 2016

The Inconel 718 alloy is a well-known super-heat-resistant alloy and a difficult-to-cut material. Inconel 718 with excellent corrosion and heat resistance is used in harsh environments. However, the heat generated is not released owing to excellent physical properties, making processes (e.g., adhesion and thermal fatigue) difficult. Tool condition monitoring in machining is significant in reducing manufacturing costs. The cutting tool is easily broken and worn because of the material properties of Inconel 718. Therefore, tool management is required to improve tool life and machinability. This study proposes a method of predicting the tool wear with non-contacting sensors (e.g., IR thermometer for measuring the cutting temperature and a microphone for measuring the sound pressure level in machining). The cutting temperature and sound pressure fluctuation according to the tool condition and cutting force are analyzed using experimental data. This experiment verifies the effectiveness of the non-contact measurement signals in tool condition monitoring.

• Korean Journal of Oriental Medicine
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• v.12 no.3 s.18
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• pp.117-130
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• 2006

The purpose of this study was to introduce the differential standard of Mok-Hyaeng Radix species. We established the classificatory standard according to the external and internal morphology and the pattern in 4 kinds of Mok-Hyaeng Radix. The results follow: 1. On the external morphology, Radix of Vladimiria souliei had a sticky material in the head of roots and it was yellowish white in the cut surface. It attached to teeth during chewing. Radix of Aucklandia lappa (=Saussurea lappa) was dark grayish brown and was grayish brown in the cut surface. It had special odor and was not attache to teeth chewing it. On the other hand, Radix of Inula helenium was dark brown. In the cut surface, cortical layer was different from wood layer. Radix of Aristolochia contorta was yellowish brown. In the cut surface, it was not smooth and cortical layer was different from wood layer. 2. On the internal morphology, Radix of Vladimiria souliei had many fascicular fibers and scattered large oil chambers in the bast ray, xylem ray, and parenchyma. On Radix of Aucklandia lappa (=Saussurea lappa), it was difficult to find out the trace when the cork layer was exfoliated. The cambium formed circle and the large oil chambers were scattered in the phloem and xylem. On the other hand, external cortical layer of Radix of Inula helenium was detached and cambium was formed to indistinct circle and large oil chambers were scattered in the phloem and xylem. On Radix of Arustolochia contorta, the large oil chambers were scattered in the surface later, bast part was relatively broad and cambium formed circle. 3. On the TLC pattern, Radix of Aristolochia contorta, Inula helenium, Aucklandia lappa, and Vladimiria souliei were chromogenic to violet and purple according to sulfuric acid colour pattern, especially faint on Aristolochia contorta. 4. On the pattern analysis of HPLC, we compared the content and the pattern of constunolide and dehydrocostus lactone, Radix of Aucklandia lappa was similar to Radix of Vladimiria souliei and Radix of Aristolochia contorta was similar to Radix of Inula helenium. On the total HPLC component pattern, constunolide and dehydrocostus lactone were similar in all four types, but it showed the Rf 5-6 peak was only in Radix of Aristolochia contorta, not in Radix of Inula helenium, Aucklandia lappa, and Vladimiria souliei. It is considered the results of this study will be furnished the basis to succeeding studies and it is needed to extensive comparative study for the same genus-degree of relatedness.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.85-91
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• 2013

The machinability of wear-resistible tungsten carbides and the tool wear behavior in machining of V30 and V50 tungsten carbides using PCD (Poly Crystalline Diamond) cutting tool was investigated to understand machining characteristics. This material is one of the difficult-to-cut materials in present, but their usage has been already broadened to every commercial applications such as mining tools, and impact resistant tools etc. Summary of the results are as follows. (1) Tool wear progression of PCD tools in turning of wear-resistible tungsten carbides were observed specially fast in primary cutting distance within 10m. (2) Three components of cutting resistance in this research were different in balance from the ordinary cutting such as that cutting of steel or cast iron. Those were expressed large value by order of thrust force, principal force, feed force. (3) If presume from viewpoint of high efficient cutting within this research, a proper cutting speed was 15m/min and a proper feed rate was 0.1mm/rev. In this case, it was found that the tool life of PCD tool was cutting distance until 230m approximately. (4) In cutting of wear-resistible tungsten carbides such as V30 and V50, it was recognized that the tool wear rate of V30 was very fast as compared with V50. (5) When the depth of cut was 0.1mm, there was no influence of the feed rate on the feed force. And the feed force tended to decrease as the cutting distance was long, because the tool was worn and the tool edge retreated. (6) It was observed that the tungsten carbides were adhered to the flank.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.5
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• pp.27-34
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• 2021

This study analyzes machining characteristics and presents optimal cutting conditions by measuring the surface roughness, dimensional accuracy, and dimension straightness based on the feed rate after processing the inner diameter hall of SCM415 steel using an automatic CNC(Computerized Numerical Control) lathe. The testing material was cut using an 11.8 mm-diameter Chamdrill after mounting the 32 mm-diameter round bar on an automatic CNC lathe. The cut depth was set at 3 mm, and the cutting speed was fixed at 1500 rpm. The surface roughness, dimensional accuracy, and dimension straightness of 15 testings were measured by changing the feed rate to 0.05, 0.1, and 0.15 mm/rev, respectively. It was difficult to process more than 15 tests during the maching due to noise or break. Additionally, the optimum cutting of SCM415 steel showed excellent surface roughness in the 10^th and 11^th of testing at cutting speed and feed speed of 1500 rpm and 0.05 mm/rev, respectively. The dimensional accuracy was measured in three dimensions after drilling, which showed good results with an average range of 0.0138-0.0208 mm. Moreover, the lower the feed speed, the higher the accuracy. Additionally, the measurement results of the dimensional straightness showed that the straightness is the straightness was the best at the 1^th and 2^th cutting regardless of the feed speed.

• Journal of Powder Materials
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• v.21 no.4
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• pp.301-306
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• 2014

Titanium alloys are extensively used in high-temperature applications due to their excellent high strength and corrosion resistance properties. However, titanium alloys are problematic because they tend to be extremely difficult-to-cut material. In this paper, the powder synthesis, spark plasma sintering (SPS), bulk material characteristics and machinability test of hybrid $Ti_2AlC$ ceramic bulk materials were systematically examined. The bulk samples mainly consisted of $Ti_2AlC$ materials with density close to theoretical value were synthesized by a SPS method. Random orientation and good crystallization of the $Ti_2AlC$ was observed at $1100^{\circ}C$ for 10 min under SPS sintering conditions. Scanning electron microscopy results indicated a homogeneous distribution and nano-laminated structure of $Ti_2AlC$ MAX phase. The hardness and electrical conductivity of $Ti_2AlC$ were higher than that of Ti 6242 alloy at sintering temperature of $1000^{\circ}C{\sim}1100^{\circ}C$. Consequently, the machinability of the hybrid $Ti_2AlC$ bulk materials is better than that of the Ti 6242 alloy for micro-EDM process of micro-hole shape workpiece.

• Journal of Powder Materials
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• v.22 no.3
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• pp.163-168
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• 2015

Ti alloys are extensively used in high-technology application because of their strength, oxidation resistance at high temperature. However, Ti alloys tend to be classified very difficult to cut material. In this paper, The powder synthesis, spark plasma sintering (SPS), bulk material properties such as electrical conductivity and thermal conductivity are systematically examined on $Ti_2AlN$ and $Ti_2AlC$ materials having most light-weight and oxidation resistance among the MAX phases. The bulk samples mainly consisted of $Ti_2AlN$ and $Ti_2AlC$ materials with density close to theoretical value were synthesized by a SPS method. Machining characteristics such as machining time, surface quality are analyzed with measurement of voltage and current waveform according to machining condition of micro-electrical discharge machining with micro-channel shape.