• 한국생산제조학회지
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• 제20권5호
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• pp.523-527
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• 2011

Polycarbonate (PC) polymer is an engineering plastic which has large tensile strength and impact resistance and is wildly used as functional parts like micro mold. Direct machining of PC materials produces lots of burrs and rough surface due to large ductility and weak heat resistance and hence it is very difficult to machine PC materials using cutting tool to make micro-parts. In this study, elliptical vibration cutting (EVC) or 2-dimensional vibration cutting was performed to minimize the size of micro V-grooves on PC material. From the experimental results, it was observed that as the cutting depth and pattern size become smaller, the better machining quality was obtained, which is attributed to the positive effect of EVC that is dependent on the ratio of vibration amplitude to cutting depth. As the height of V-groove becomes less than $1.8{\mu}m$, however, the machining quality becomes lower as the pattern size decreases.

• 한국생산제조학회지
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• 제6권3호
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• pp.103-110
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• 1997

This study provides the useful actual data instead of the experience data using in industrial fields. Especially, values of each components of cutting force are effective in the rake angle, setting angle and cutting area. Many researches have been made on the work piece materials, kinds of bite materials, rake angle, nose radius and depth of cut, but a few on the bite setting angle. In order to select optimal cutting speed, it was summarized the following results are achieved; A chieved that an affect of cutting resistance on the setting angle is a little under giving experimental conditions and therefore a worker can be choose the value of it randomly.

• 한국표면공학회지
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• 제53권6호
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• pp.360-368
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• 2020

Wear resistance of cutting tools is one of the most important requirements in terms of the durability of cutting tool itself as well as the machining accuracy of the workpiece. Generally, tungsten carbide ball end mills have been processed with hard coatings for high durability and wear resistance such as diamond coating and tetrahedral amorphous carbon(ta-C) coating. In this study, we developed multilayer ta-C coatings whose wear resistance is comparable to that of diamond coating. First, we prepared single layer ta-C coatings according to the substrate bias voltage and Ar gas flow, and the surface microstructure, raman characteristics, hardness and wear characteristics were evaluated. Then, considering the hardness and wear resistance of the single layer ta-C, we fabricated multilayer coatings consisting of hard and soft layers. As a result, it was confirmed that the wear resistance of the multilayer ta-C coating with hardness of 51 GPa, and elastic recovery rate of 85% improved to 97% compared to that of the diamond coated ball end mill.

• Journal of Ecology and Environment
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• 제44권4호
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• pp.256-263
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• 2020

Background: Ambrosia trifida is a highly invasive annual plant, but effective control methods have not been proposed. Among various eradication methods, cutting is a simple measure to control invasive plants, and sowing seeds of native plants may effectively increase biotic resistance to invasion. In this study, we conducted a field experiment with two treatments: cutting and sowing seeds of six native or naturalized plants. Results: We found a significantly lower A. trifida abundance after cutting than in the control (77% decrease). Sowing seeds of native species did not provide any additional benefit for the control of A. trifida, but increased the importance values and diversity of other native vegetation. The abundance of A. trifida was negatively correlated with that of other plant taxa based on plant cover, biomass, and density. However, biotic resistance of sown plants was not effective to control invasion because A. trifida was so competitive. Conclusions: We concluded that cutting is an effective measure to control Ambrosia trifida while sowing seeds of native plants can increase native plant diversity.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.83-88
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• 2003

In this study, experiments were conducted with an ultra-precision machine, developed In domestic, to find the characteristics and the most suitable cutting conditions of ultra-precision machining. To maximize the performance of the machine, the machine was installed in a room that is protected from vibration and is maintained constant temperature and constant humidity. Selected work pieces are an aluminum-alloyed material, which has excellent corrosion resistance and has low deformation. The used tool is synthetic poly crystal diamond which has excellent abrasion resistance and has low affinity. Four types of tool nose radius were used such as 0, 0.1, 0.2 and 0.4mm. Machining is performed with cutting speed of 500, 800 and 1000m/min., feed rate of 0.005, 0.008, 0.010mm/rev. and cutting depth of 0.0005, 0.0025 and 0.005mm respectively which can generally be used in the field as a cutting condition. As a method of evaluation surface roughness was measured for each cutting condition and reciprocal characteristics are computed for each tool nose radius, cutting speed, feed rate and cutting depth. As a result the most suitable cutting condition and characteristics of ultra-precision machining were identified which can usefully be applied in the industrial field.

• Coupled systems mechanics
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• 제2권1호
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• pp.23-51
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• 2013

An analytical algorithm for the estimation of the resistance forces exerted on the dipper of a cable shovel and the specific energy consumed in the cutting-loading process is presented. Forces due to payload and to cutting of geomaterials under given initial conditions, cutting trajectory of the bucket, bucket's design, and geomaterial properties are analytically computed. The excavation process has been modeled by means of a kinematical shovel model, as well as of dynamic payload and cutting resistance models. For the calculation of the cutting forces, a logsandwich passive failure mechanism of the geomaterial is considered, as has been found by considering that a slip surface propagates like a mixed mode crack. Subsequently, the Upper-Bound theorem of Limit Analysis Theory is applied for the approximate calculation of the maximum reacting forces exerted on the dipper of the cable shovel. This algorithm has been implemented into an Excel$^{TM}$ spreadsheet to facilitate user-friendly, "transparent" calculations and built-in data analysis techniques. Its use is demonstrated with a realistic application of a medium-sized shovel. It was found, among others, that the specific energy of cutting exhibits a size effect, such that it decreases as the (-1)-power of the cutting depth for the considered example application.

• 한국공작기계학회논문집
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• 제13권1호
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• pp.9-15
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• 2004

In this study, experiments were conducted with an ultra-precision machine, developed in domestic, to find the characteristics and the most suitable cutting conditions of ultra-precision machining. To maximize the performance of the machine, the machine was installed in a room that is protected from vibration and is maintained constant temperature and constant humidity. Selected work pieces are an aluminum-alloyed material, which has excellent corrosion resistance and has low deformation. The used tool is synthetic poly crystal diamond, which has excellent abrasion resistance and has low affinity. Four types of tool nose radius were used such as 0, 0.1, 0.2 and 0.4mm. Machining is performed with cutting speed of 500, 800 and 1000m/min., feed rate of 0.005, 0.008, 0.010mm/rev. and cutting depth of 0.0005, 0.0025 and 0.005mm respectively which can generally be used in the field as a cutting condition. As a method of evaluation, surface roughness was measured for each cutting condition, and reciprocal characteristics are computed for each tool nose radius, cutting speed, feed rate and cutting depth. As a result, the most suitable cutting condition and characteristics of ultra-precision machining were identified which can usefully be applied in the industrial field.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.985-988
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• 1997

In end milling process, the undeformed chip section area and cutting forces vary periodically with phase change of the tool. However the real undeformed chip section area deviates from the geometrically ideal one owing to cutter runout and tool shape error. In this study ,a method of estimating the real undeformed chip section area which reflects cutter runout and tool shape error was presented in up end milling process using measured cutting forces. Size effect was identified from the analysis of specific cutting resistance obtained by using the modified undeformed chip section area.

• 지질공학
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• 제14권4호
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• pp.451-460
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• 2004

사면안정해석에 일반적으로 이용되는 2차원 한계평형해석에서는 활동면의 강도를 활동면 전체에 동일하게 설정한다. 그러나 사면의 활동면에서 저면부와 가장자리부의 강도는 다른 경우가 대부분이다. 4가지 절취모델을 이용한 3차원 사면안정해석의 결과에 따르면 활동면내에서 가장자리부의 저항력이 사면의 안정성에 크게 영향을 미치는 것으로 나타났다. 3차원 사면안정해석에서 활동면 강도를 저면부와 가장자리부로 구분하여 설정함으로써 지금까지 고려하지 못했던 사면 가장자리부의 전단강도가 사면안정에 미치는 영향을 정량적으로 파악할 수 있었다. 활동 저면부의 저항력이 낮은 경우에는 사면의 측부 절토에 의하여 안전율이 크게 저하되며, 저항력이 높은 경우에는 말단부 절토에 의하여 안전율이 저하되고 두부 절토에 의하여 안전율이 향상된다.

• 한국정밀공학회지
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• 제24권10호
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• pp.37-45
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• 2007

End-milling is intermittent cutting process performed by a tool with a number of teeth. Its cutting forces are commonly measured by the tool dynamometer which has rectangular coordinates. In this case, the pattern of cutting forces is different according to cutting conditions. At a certain cutting condition, the sign of cutting force changes from positive to negative during a revolution of one tooth. The change of force direction excites a cutting tool and severe vibration arises when radial depth of cut increases. In this study, cutting experiments and simulations were carried out in order to explain the cause of the change of the cutting force direction. In addition, the effect of the cutting force change was discussed in terms of chatter vibration in end milling.