• International Journal of Precision Engineering and Manufacturing
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• 제6권1호
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• pp.51-58
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• 2005

The development of the high-efficiency machine-tools equipment and new cutting tool materials with high hardness, heat- and wear-resistance has opened the way to application of high-speed cutting process. The basic argument of using of high-speed cutting processes is the reduction of time and the respective increase of machining productivity. In this sense, the spindle units may be regarded as one of the most important units, directly affecting many parameters of high-speed machining efficiency. One of the possible types of spindle units for high-speed cutting is the air-bearing type. In this paper, we propose the mathematical model of the dynamic behavior of the air-bearing spindle. To provide the high-level of speed capacity and spindle rotation accuracy we need the adequate model of "spindle-bearings" system. This model should consider characteristics of the interactions between system components and environment. To find the working characteristics of spindle unit we should derive the equations of spindle axis movement under the affecting factors, and solve these equations together with equations which describe the behavior of lubricant layer in bearing (bearing stiffness equations). In this paper, the three influence coefficients are introduced, which describe the center of spindle mass displacement, angle of shaft rotation around the axes under the unit force application and that under the unit torque application. These coefficients are operated in the system of differential equations, which describes the spindle axis spatial movement. This system is solved by Runge-Kutta method. Obtained trajectories and amplitude-frequency characteristics were then compared to experimental ones. The analysis shows good agreement between theoretical and experimental results, which confirms that the proposed model of air-bearing spindle is correctis correct

• 한국초지조사료학회지
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• 제9권2호
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• pp.77-81
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• 1989

This experiment was conducted to elucidate the changes of dry matter production in permanent pasture and its relation with relative yield of the 1st cutting, regrowth capacity, and persistance of orchardgrass sward, based on the data of preceeding The results were summarized as follows; 1. Relationship between relative yield of the 1st cutting and regrowth capacity were changed by the times of established pasture. Thus, the relative yield of the 1st cutting have negative significant correlation (P < -0.001) with regrowth capacity. 2. Regrowth capacity(RC) was positively significant correlations with the dry weight of plant (DW/pl.), number of tillers per plant (NT/pl.), plant size(PS) and distance between adjacent plants (DIS) of the 1st cutting. Also, regrowth capacity(RC) was positively correlations with the dry weight of plant (DW/pl.), number of tillers per plant (NT/pl.), stubble diameter(DIA), stubble area(SB), plant size(PS) and distance between adjacent plants(D1S) of the 2nd cutting. 3. The coefficients of regression of the 1st cutting showed a tendency to slightly decrease, on the other hand, the 2nd cutting and total yield were tended to increase by the times of established pasture. 4, Between the regrowth capacity and persistency were may deeply concerned to the changes of dry matter production in permanent pasture. 5. The process of dry matter production in permanent pasture can be shown in following diagrams.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.245-248
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• 2004

The press cutter is productive equipment that practically manufactures materials such as fabrics, papers, films, leathers, rubbers etc. into the desired shapes using cutting method. Plate cutting process is one of the primary energy absorbing mechanisms in a grounding or collision event. The cutting mechanism is complicated and involves plastic flow of plate in the vicinity of the tip, friction between wedge and plate, deformation of plate. In this paper, we studied the effect of friction between cutter and plastic sheet for producing precise and superior products. The press cutter is analyzed numerically using MARC finite element program according to the variation of friction coefficients. The FEM results showed that normal stress, equivalent cauchy stress, normal total strain, equivalent total strain are good when friction coefficient is 0.0 and shear stress, shear total strain are good when friction coefficient is 0.8.

• 한국생산제조학회지
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• 제20권3호
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• pp.225-231
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• 2011

In this paper, a new end-milling force modelling technique was suggested by considering runout, and its result was compared with real measured force. The specific cutting force is the multiplication of cutting force coefficient and uncut chip thickness. This parameter was used for experimental modelling and prediction of theoretical force. These coefficients, which can be obtained by fitting measured average forces in several conditions, were used for the formulation of theoretical force. The mechanism of end-milling force with runout was developed in this research and its result was verified by comparing the fluctuating theoretical force and its measured one. The fluctuation of force was incurred by a geometric shape of workpiece and its runout in holding. The result of suggested force considering runout shows a good consistency with measured one. So this modelling method can be used effectively for a prediction of end-milling force with runout effect.

• International Journal of Safety
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• 제3권1호
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• pp.1-5
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• 2004

This study discusses frequency analysis based on autoregressive (AR) time series model, and the characterization of surface quality in orthogonal cutting of a fiber-matrix composite materials. A sparsely distributed idealized composite material, namely a glass reinforced polyester (GFRP) was used as workpiece. Analysis method employs a force sensor and the signals from the sensor are processed using AR time series model. The experimental correlations between the fiber pull-out and AR model coefficients are then established.

• 한국산업안전학회:학술대회논문집
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• 한국안전학회 2000년도 춘계 학술논문발표회 논문집
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• pp.52-57
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• 2000

This paper discusses frequency analysis based on frequency spectrum in orthogonal cutting of fiber-matrix composite materials. A glass reinforced polyester (GFRP) was used as workpiece. Analysis method employs a force sensor and the signals from the sensor are processed using a fast Fourier transform (FFT) technique. The experimental correlation between the different chip formation mechanisms and model coefficients are then established. (omitted)

• Journal of Forest and Environmental Science
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• 제14권1호
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• pp.145-156
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• 1998

본 연구는 집중호우로 인하여 임도사면 붕괴가 발생한 강원도 춘천시 지역의 5개 임도(백양임도, 변가터임도, 사오랑임도, 부귀임도, 당림임도)를 대상으로 수량화이론(II)에 의한 절토사면의 붕괴위험 예측에 관하여 분석하였다. 그 결과는 다음과 같다. 임도 절토사면 붕괴는 주로 절토부 구조적인 요인과 식생, 지형적인 요인이 복합적으로 작용하여 발생하는 것으로 나타났다. 또한 편상관계수(partial correlation coefficient) 및 범위(range) 값에 의한 절토사면의 붕괴예측 결과는 절토길이 8m이상, 토심이 2.5m이상, 산지경사 $30^{\circ}{\sim}50^{\circ}$사이, 절토피복율이 무식생인 경우, 절토경사 $60^{\circ}$ 이상에서 붕괴위험도가 높게 나타났으며, 판별적중율은 90.1%이었다.

• 동력기계공학회지
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• 제12권3호
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• pp.66-71
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• 2008

Diamond-like-carbon (DLC) coatings could be good candidates as solid lubricants for cutting tools in dry machining of aluminum alloy. In this work, DLC thin films were produced as a friction reduction coating for WC-Co insert tip using the plasma immersion ion beam deposition (PIIED) technique. DLC coatings were also coated on $Al_2O_3$ specimens and high temperature wear tested up to $400^{\circ}C$ in dry air to observe the survivability of the DLC coating in simulated severe cutting conditions using a pin-on-disc tribotester with Hertzian contact stress of 1.3GPa. It showed reduced friction coefficients of minimum 0.02 up to $400^{\circ}C$. And cutting performance of DLC coated WC-Co insert tips to Al 6061 alloy were conducted in a high speed machining center. The main problems of built-up edge formation in aluminum machining are drastically reduced with improved surface roughness. The improvements were mainly related to the low friction coefficient of DLC to Al alloy and the anti-adhesion of Al alloy to WE due to the inertness of DLC.

• 한국산업안전학회:학술대회논문집
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• 한국안전학회 2000년도 추계 학술논문발표회 논문집
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• pp.39-45
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• 2000

In recent years, composite materials such as fiber reinforced plastics (FRP) have gained considerable attention in the aircraft and automobile industries due to their light weight, high modulus and specific strength. In practice, control of chip formation appears to be the most serious problem since chip formation mechanism in composite machining has significant effects on the finished surface ［1,2,3,4,5］. Current study will discuss frequency analysis based on autoregressive (AR) time series model and process characterization in orthogonal cutting of a fiber-matrix composite materials. A sparsely distributed idealized model composite material, namely a glass reinforced polyester (GFRP) was used as workpiece. Analysis method employs a force sensor and the signals from the sensor are processed using AR time series model. The experimental correlation between the different chip formation mechanisms and model coefficients are established.(omitted)

• 한국산업안전학회:학술대회논문집
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• 한국안전학회 2003년도 추계 학술논문발표회 논문집
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• pp.113-117
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• 2003

The reliability of machined fiber reinforced composites (FRC) in high strength applications and the safety in using these components are often critically dependent upon the quality of surface produced by machining since the surface layer may drastically affect the strength and chemical resistance of the material [1,2,3,4]. Current study will discuss the characterization of fiber pull-out in orthogonal cutting of a fiber-matrix composite materials. A sparsely distributed idealized model composite material, namely a glass reinforced polyester (GFRP) was used as workpiece. Analysis method employs a force sensor and the signals from the sensor are processed using AR time series model. The experimental correlation between the fiber pull-out and the AR coefficients is examined first and effects of fiber orientation, cutting parameters and tool geometry on the fiber pull-out are also discussed.