• International Journal of Precision Engineering and Manufacturing-Green Technology
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• 제5권5호
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• pp.571-581
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• 2018

In the present study, monitoring of elliptical vibration cutting process by utilizing internal data in the ultrasonic elliptical vibration device without external sensors such as a dynamometer and displacement sensor is investigated. The internal data utilized here is the change of excitation frequency, i.e. resonant frequency of the device, voltages applied to the piezoelectric actuators composing the device, and electric currents flowing through the actuators. These internal data change automatically in the elliptical vibration control system in order to keep a constant elliptical vibration against the change of the cutting process. Correlativity between the process and the internal data is described by using a vibration model of ultrasonic elliptical vibration cutting and verified by several experiments, i.e. planing and mirror surface finishing of hardened die steel carried out with single crystalline diamond tools. As a result, it is proved that it is possible to estimate the elements of elliptical vibration cutting process, e.g. tool wear and machining load, which are important for stable cutting in such precision machining.

• 한국초지조사료학회지
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• 제8권1호
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• pp.26-32
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• 1988

This study was conducted to determine the effects of cutting frequency and cutting height on agronomic characteristics and yield performance of sorghum-sudangrass hybrid, cv. Pioneer 855 F on the experimental field of Livestock Experiment Station, Suweon. The results are summarized as follows: 1. The relative contribution of leaf component to total yield was higher when the plants were cut frequently rather than when defoliated only a few times, and tend to be higher with high cutting. 2. Leaf Area Index (LAI) was the highest at the primary growth of two cutting times scheme and the first regrowth for three or four cutting times a year, but LAI, in general, was not related to cutting height. 3. Crop Growth Rate was the heighest at the first regrowth-plants grown in summer, and it was also related to the amount of stubble left at the previous cut. 4. Dead stubbles were not occurred when plants were cut before heading, but those were accompanied by the frequent and low cutting. 5. Total fresh fodder and dry matter yield were the highest at two times cut a year, and decreased with frequent cutting. The optimum cutting height at two times cut was ca. lOCm height stubble from the ground level, but yield increased with higher level cutting at the three or four times cut a year.

• 한국초지조사료학회지
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• 제14권2호
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• pp.69-75
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• 1994

This experiment was canied out to study the effect of cutting frequencies (3, 4 and 5 cuts per year) and mineral nitrogen fertilization on dry matter yields, in order to estimate optimum level of fertilizing mineral nitrogen in orchardgrass(Dacry1is glomerafa L.). The results are as follows: 1. Dry matter yields were the highest in the 1st cut at 3 cutting frequency and in the 2nd cut at 4 and 5 cutting frequencies, and they shared 49.7, 37.0 and 37.0% of annual dry matter yield respectively. 2. When only phosphorus and potassium were applied, annual dry matter yields were between 9.4 and 11.5 tons per ha and the highest yield was observed at 3 cutting frequency. 3. Dry matter yield in relation to fertilization of mineral nitrogen was highly increased when more nitrogen was applied as 360 kg per ha compared to 240 kg per ha at 3 cutting frequency. At 4 and 5 cutting frequencies, increases in dry matter yield, to large extent, were showed at 120 and 150 kg of nitrogen per ha(30 kg Nlcutlha) compared to no application of nitrogen. The efficiencies of mineral nitrogen fertilization (kg DM/kg N) were 28.0, 22.7 and 20.6 kg dry matter yields per nitrogen(kg) respectively). 4. At 4 and 5 cutting frequencies, dry matter yields were reduced when 360 kg and 300 kg of mineral nitrogen per ha(90 kg and 60 kg Nlcutlha) were applied respectively. 5. Particularly at 4 and 5 cutting frequencies of this study, maximum marginal yields reached at 129.9 kg and 148.0 kg of fertilizing mineral nitrogen per ha, and economical borden of mineral nitrogen fertilization were between 222.4 and 250.0 kg and between 244.8 and 276.8 kg respectively. At the same cutting frequencies, the highest dry matter yields were obtained at 365.4 and 433.8 kg of fertilizing mineral nitrogen respectively.

• 한국초지조사료학회지
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• 제17권4호
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• pp.407-414
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• 1997

In this study, the optimum cutting 6equency and level of mineral nitrogen fertilization were investigated for the production of Reed canarygrass in uncultivated rice paddy. The results are summarized as follows; 1. Higher relative dry matter yields were recorded in 2nd cut of plots with 3 and 5 cutting frequencies, and 3rd cut of plot with 4 cutting kquency, respectively. 2. With no nitrogen fertilization, mean dry matter yields per year were 6.2~7.6 tonsha and the highest yield appeared in plot with 4 cutting 6equency. 3. The increased fertilization of mineral nitrogen resulted in the increased dry matter yield. Significantly higher dry matter yields than that of no nitrogen fertilization were recorded in fertilization of 90 kg nitrogen per year in 3 cutting fequency, 240 kg in 4 cutting frequency and 150 kg in 5 cutting 6equency respectively. 4. Efficiency of dry matter production with nitrogen fertilization(kg DMkg N) was higher in 30kg Nhalcut in 3 and 5 cutting eequency, 60kg Nhalcut in 4 cutting 6equency respectively. In each cutting kequency, the higher efficiency of dry matter production appeared in 1st cut in 3 cutting kequency, and 2nd cut in 4 and 5 cutting 6equency respectively. 5. Economic N level(kg/ha) was 179.5~242.3kg/ha in 3 cutting 6equency, and 189.6-241.6kg/ha and 167.0 ~253.2kg/ha in 4 and 5 cutting 6equency respectively, and marginal dry matter yields were 11.4~ 12.3 tons/ ha, 11.2 ~ 11.8 tons/ha and 8.3 ~9.1 tons/ha in 3, 4 and 5 cutting 6equency respectively. 6. The limiting N fertilization level to the highest dry matter were estimated to be 569.9kg/ha, 492.4kg/ha and 654.lkg/ha in 3, 4 and 5 cutting kequency respectively.

• 한국정밀공학회지
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• 제18권6호
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• pp.133-140
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• 2001

This paper suggests another system for a cutting force measuring tool in a milling process. Generally, tool dynamometer is taken into account for the most appropriate cutting force measuring tool in the analysis of cutting mechanism. However, high price and limited space make it difficult to be in-situ system for controllable milling process. Although an alternative method using AC current of servo-motor has been suggested, it is unsuitable for cutting force control because of small upper frequency limit and noise. The cutting force measuring system is composed of two load cells placed between the moving table bracket and the nut flange part of ballscrew. It has many advantages such as low cost and wide range measurement than tool dynamometer because of the built-in moving table and the low cost load cell. The static and dynamic model of the measuring system using imbeded load cell is introduced. Various Experiments are carried out to validate both models. By comparing the cutting forces from a series of end milling experiments on the tool dynamometer and the system developed in this paper, the accuracy of the cutting force measuring system is verified. Upper frequency limit is measured by the experiment of dynamic characteristics.

• 한국기계가공학회지
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• 제4권1호
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• pp.37-42
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• 2005

The localization of manufacturing technique development is actualizing for low cost with supplies of display devices. We need more high cutting technique because consumers want flat glasses of various sizes. Recently, most general two methods are normal wheel cutting and laser cutting, but both of them have some faults. First, the wheel cutting has cracks and sharp edges of sections. Second, it is easy for laser cutting to cut curved lines. however, it has thermal damage and low traverse speed. I suggest a new cutting method by high-wave frequency vibration wheel cutting(HFVC), which is good for quality improvement. Vertical cracks and crack depth is observed, after HFVC. When the average of the crack depth is $30{\mu}m$ and the average of the wallner liner depth is $200{\mu}m$, it has the most high quality of the sections in this experiment. As a result, when we consider between the normal wheel cutting method and the HFVC method, the latter has low cracks and good quality.

• 한국초지조사료학회지
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• 제20권4호
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• pp.237-242
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• 2000

This study was conducted to investigate the effects of cutting frequency on dry matter yield and nutritive value between heading and headless varieties of sorghumxsudangrass hybrid in 1998. Treatments were var. TE hay grazer(heading type) and Jumbo(headless type) as main plot, and 1, 2, and 3 cutting times per a year as sub plot. Although plant height of sorghumxsudangrass hybrid was no significant difference among treatments, headless type was very slightly higher than that of heading type, and both of variety decreased with 1, 2, and 3 cutting times in order. Also, dry matter yield of sorghum~sudangrass hybrid was no significant difference between heading and headless type. Dry matter yield of first cutting plot in heading type and in headless type was the higher than those of second and third cutting plot. Acid detergent fiber and neutral detergent fiber of headless type were slightly higher than that of heading type. Acid detergent fiber of sorghumxsudangrass hybrid was highest at first cutting plot in both varieties. Neutral detergent fiber of second cutting plot in heading type and first cutting plot in headless type were the highest respectively. In vitro dry matter digestibility of headless type was very slightly higher than that of heading type. And in vitro dry matter digestibility of second cutting plot was the highest in both varieties. In vitro digestible dry matter of sorghumxsudangrass hybrid was no significant difference among treatments. The results demonstrated that although there was not significant difference, cultivation of headless type and first cutting plot per a year were very good for nutritive value and DM yield of sorghumxsudangrass hybrid as summer forage crops in Korea. (Key words : Heading, Headless type, Cutting frequency, Sorghum X Sudangrass Hybrid)

• 한국가구학회지
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• 제16권1호
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• pp.17-23
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• 2005

European maple is famous for the optimum solid wood for making bridge which is the most important part in violin acoustics. This study was carried out to investigate the variation of main features, i. e. annual ring width and cutting direction of costly imported violin bridge blanks and to examine the effect of these features of the blanks on the vibrational characteristics of bridge blanks. Imported violin bridge blanks had somewhat large variation in major macroscopical and physical properties and there was little relationship between annual ring density and weight of maple blanks. Resonant frequency of violin bridge blanks had some positive correlation with weight, however, damping having negative relationship with frequency was seldom affected by any physical properties of the maple blanks. Deviation from the radial cutting of tail side(ray direction from top toward feet on the edge of bridge blank) lowered the resonant frequency. Consequently, weight and ray direction should be taken for the critical quality decisive factors(QDF) of incoming bridge blanks by not only inspectors also luthiers who tune the bridge by shaping and are responsible for the final timbre quality of this complicate instrument.

• 한국정밀공학회지
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• 제24권11호
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• pp.52-58
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• 2007

A cutting device capable of generating various shapes of the cyclic elliptical trajectory of a cutting tool was proposed and micro v-grooving experiments were performed to investigate the characteristics of elliptical vibration cutting (EVC). The proposed cutting device is comprised of a pair of parallel piezoelectric actuators with which harmonic voltages of varying phase difference and magnitude are supplied, creating various shapes of the elliptical tool path. The attributes of the elliptical locus involving the direction of the axis of an ellipse, the rotational direction and amplitudes of a trajectory were fine-tuned for stable operation of the EVC. The EVC characteristics performed with brass and copper revealed reduction in the cutting resistance and suppression of burr formation, resulting in the enhancement of form accuracy of machined micro-features. While the effect of the EVC increases with the increase of excitation frequency and the amplitude, it is found that a change in the cutting force decreases as the amplitude of an elliptical locus increases.

• 한국정밀공학회지
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• 제11권4호
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• pp.13-25
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• 1994

In order to design and improve a new machine tool, there is a need for a better understanding of the cutting force. In this paper, the computer programs were developed to predict not only the mean specific cutting pressure but also the cutting force. The simulated cutting forces in X, Y, Z directions resulted form the developed cutting force model were compared with the measured cutting forces in the time and frequency domains. The simulated cutting forces resulted from the new cutting force model have a good agreement with the measured force in comparison with these resulted from the existing cutting force model.