• 한국농공학회지
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• 제17권3호
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• pp.3885-3893
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• 1975

This work was intended to study the cutting graph and vibratory phenomina of a newly developed mower which may be suitable for mowing agricultural product having large and hard stems like corn and sugar beet. The system consists of cutter-bar having Curvilinear-translation motion, which attached to drag-crank mechanism. The motion of equation developed for experimental vibratory system which equipped with the cutter-bar system was established and the parameters defining the system's vibratory motion were experimentally determined. The optimum balancing weight for the cutter-bar am vibratory characteristics of the cutter-bar for various counterweight were analyzed to provide the design and operational conditions. The results of the study are summarized as follows; (1) The cutting graph by the new cutter-bar system depends upon the magnitude of ratio of forward travel(Vm) to crank speed (R$\omega$); The cutting pitch for Vm/R$\omega$ 1 (whole cycle cutting) and Vm/R$\omega$=2/$\pi$ (a half cycle cutting) are 2$\pi$ Vm and 4R, respectively. (2) The experimental vibratory system had been proved to function adequately so that it can be used in determining the required counterweight to minimize the vibratory motion of cutter-bar. (3) Experimentally determined counterweight to give the least vibratory motion was a little greater than the theoretically determined one. With the optimum counterweight it was possible to reduce up to about 87% of the amplitude without counterweight, which may be considered to be within safe operational region. (4) To avoid the actual operation of the cutter-bar at resonance which occured in low frequency ratio, it was considered that the rotational speed of the crank for a specific design of mower should be determined separately in connection with the desired cutting graph.

• Journal of Biosystems Engineering
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• 제35권6호
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• pp.373-379
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• 2010

This study was carried out to develop a belt pick-up type one-row soybean cutter, using physical properties and production conditions of soybeans. The prototype soybean cutter consisted of 4 parts: cutting part, conveying part, collecting part, and travelling part. The prototype soybean cutter was designed to cut soybeans planted with a row spacing of 600 mm, and at a height of 30 mm from the bed bottom using a disk saw. Through various trials with different peripheral velocities of the disk saw and forward speed of the cutter, determined ranges of the peripheral velocity of the disk saw cutting soybeans stems were greater than 18.3 m/s. Spacing between pick-up belts (clearance) was in a range of 60~90 mm so that soybeans could be picked at heights greater than 25 cm, and the size and shape of the pick-up belt were determined the conventional manual harvesting method. The optimal ratio between the forward speed of cutter and the peripheral speed of pick-up belts were from 1 to 1.2 by theoretical analysis. the pick-up belts had a $35^{\circ}$ of tilted angle and $90^{\circ}$ of twisted angle to pick up soybeans safely from the plant input to the lower end of the belts and convey soybeans to the upper end of belts nearby a container. The soybeans at the rear container were dropped down on the soybean row with an interval. The effective field capacity of the prototype soybean cutter was 0.136 ha/h, reducing the working hour by 92% when compared with the manual cutting.

• 터널과지하공간
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• 제34권2호
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• pp.143-153
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• 2024

TBM 공법은 발파 공법에 비해 굴착 중 소음과 진동 수준이 낮고, 안정성이 높은 터널 굴착 공법이며, 전세계적으로 터널 프로젝트에 TBM 공법을 적용하는 사례가 증가하는 추세이다. 디스크 커터는 TBM의 커터헤드에 장착되는 굴착 도구로 지속적으로 막장면 지반과 상호작용하며, 이때 필연적으로 마모가 발생한다. 본 연구에서는 지질 조건과 TBM 운영파라미터, 머신러닝 알고리즘들을 이용하여 디스크 커터 마모를 정량적으로 예측하였다. 디스크커터 마모 예측의 입력변수 중 UCS 데이터의 수가 다른 기계 데이터 및 마모 데이터에 비해 매우 부족하기 때문에, 먼저 TBM 기계 데이터를 이용하여 전체 구간에 대한 UCS 추정을 진행하고, 완성된 전체 데이터로 마모율 계수 예측을 수행하였다. 마모율 계수 예측 모델의 성능을 비교해 본 결과 XGBoost 모델의 성능이 가장 높게 나타났으며, 복잡한 예측 모델의 해석을 위해 SHapley Additive exPlanation (SHAP) 분석을 진행하였다.

• 터널과지하공간
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• 제33권6호
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• pp.519-533
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• 2023

본 연구에서는 평균 압축강도가 100 MPa 이상인 암석에 대해 픽커터의 선형절삭시험을 실시하였고, 적외선 열화상 카메라를 통해 측정된 픽커터 절삭 시의 발생 온도와 커터 작용력과의 상관관계를 분석하였다. 모든 시험조건에서 최대 온도는 치핑이 발생하는 암석면에서 측정되었고, 암석에 발생한 온도는 픽커터의 작용력과 밀접한 상관관계를 나타내었다. 반면, 픽커터에 발생하는 온도는 대기 온도 대비 최대 36℃ 이내로 상승하였고 커터 작용력과의 상관관계도 뚜렷하지 않았다. 이는 실험실 조건의 짧은 절삭거리와 텅스텐 카바이드 삽입재의 높은 열전도 특성이 원인인 것으로 사료된다. 단, 픽커터의 주요 부위 중에 텅스텐 카바이드 삽입재에 상대적으로 높은 온도가 유지되는 것으로 나타나, 픽커터 절삭 성능의 유지를 위해서는 삽입재와 헤드부 사이에 보강을 실시하거나 픽커터 제작 시에 은납 공정의 품질을 향상시키는 것이 필요할 것으로 판단된다.

• 터널과지하공간
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• 제33권5호
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• pp.414-424
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• 2023

본 연구에서는 픽커터의 다양한 형상변수들과 그에 따른 절삭 가능 암반 조건들에 대한 총 326개의 정보를 수집하고 데이터베이스를 구축하였다. 이와 같이 구축한 데이터베이스를 대상으로 통계분석을 실시한 결과, 픽커터의 형상을 정의하는 변수들 사이에는 유의미한 양(+)의 상관관계가 존재하는 것으로 나타났다. 특히, 픽커터의 길이 관련 변수들과 텅스텐 카바이드 삽입재의 형상 변수들 사이의 상관관계가 높게 나타났다. 픽커터 샤프트의 직경도 삽입재의 형상변수들과 밀접한 상관관계를 나타내었다. 반면, 네 가지 조건으로 정의한 암반 조건에 대한 변수와 픽커터의 형상 변수들 사이에는 뚜렷한 상관관계를 확인하기 어려웠다. 이는 암반의 불확실성으로 인해 픽커터의 적용 대상을 수치가 아닌 적용 가능 범위로 제시했기 때문인 것으로 사료된다. 단, 암반이 강해질수록 픽커터 형상변수들의 평균값이 증가하는 경향을 나타내었다. 그러나 픽커터의 길이 관련 변수들은 암반이 강해질수록 오히려 작아지는 것으로 나타났는데, 이는 경암반에서 길이가 긴 픽커터를 사용할 때 발생할 수 있는 모멘트의 발생을 줄이기 위한 방안으로 사료된다.

• Geomechanics and Engineering
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• 제35권6호
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• pp.647-663
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• 2023

The investigation of the disc cutter wear prediction has an important guiding role in TBM equipment selection, project planning, and cost forecasting, especially when tunneling in a long-distance rock formations with high strength and high abrasivity. In this study, a comprehensive database of disc cutter wear data, geological properties, and tunneling parameters is obtained from a 1326 m excavated metro tunnel project in leptynite in Shenzhen, China. The failure forms and wear consumption of disc cutters on site are analyzed with emphasis. The results showed that 81% of disc cutters fail due to uniform wear, and other cutters are replaced owing to abnormal wear, especially flat wear of the cutter rings. In addition, it is found that there is a reasonable direct proportional relationship between the uniform wear rate (WR) and the installation radius (R), and the coefficient depends on geological characteristics and tunneling parameters. Thus, a preliminary prediction formula of the uniform wear rate, based on the installation radius of the cutterhead, was established. The correlation between some important geological properties (K_V and UCS) along with some tunneling parameters (F_n and p) and wear rate was discussed using regression analysis methods, and several prediction models for uniform wear rate were developed. Compared with a single variable, the multivariable model shows better prediction ability, and 89% of WR can be accurately estimated. The prediction model has reliability and provides a practical tool for wear prediction of disc cutter under similar hard rock projects with similar geological conditions.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.1025-1030
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• 1997

In this study,the procedure of interpolation surface modeling on bicubic spline patch equation and NC machining are presented. The procedure consists of three parts : patch modeling,cutter location data generation,post processing and NC milling machining. For generation of the cutter location data,tangent vectors and units normal vectors on the patch must be calculated. In order to investigate the properties of the interpolation surface created by bicubic spline patch, two kinds of end conditions, clamped end condition and relaxed end condition,were applied in this study. The shape of the patch depends on the magnitide of the tangent vectors and twist vectors at the corners of bicubic surface patch. the patch generated by relaxed end condition more approximated to the surface patch which was given.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.1018-1022
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• 2000

Enhancement of the accuracy of products and productivity are essential to survive in a global industrial competition. This trend requires tighter dimensional tolerance specifications. To actively cope with the rapid change of the workpiece material and cutter geometry, a general method that can predict and analyze the machined surface is needed. Surface generation model for the prediction of the topography of machined surfaces is developed based on cutting force model considering cutter deflection and runout. This paper presents the method that constructs the three-dimensional machined surface error following the movement of a cutter, irrespective of the variations of cutting conditions. In addition, the effects of the cutting forces and the kink shape on the machined surface are extensively investigated.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.995-1000
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• 2000

In this paper. a mechanistic model is first constructed to predict three-dimensional cutting forces, and the uncut chip th thickness is calculated by following the movements of the position of the center of a cutter, which varies with the nominal feed, cutter deflection and runout. For general implementation to a real machining, this paper presents the method that determines constant cutting force coefficients, irrespective of the cutting conditions or cutter rotation angles. In addition, this study presents the approach which estimates runout-related parameters. the runout offset and its location angle, using only one measurement of cutting forces. For more accurate cutting force predictions, the size effect has to be considered in the cutting force model. In this paper, two approximate methods are suggested since the strict approach is practically impossible due to a measurement problem. The size effect is individually considered for narrow and wide cuts.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.74-79
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• 1996

The wear of partially coated pinion cutters under several cutting conditions was studied. In the realm of this experiment, chipping was a dominant tool wear mechanism and flank wear was much larger than crater wear. Under the condition of relatively low rotary feed and low radial feed rate, the wear due to chipping was concentrated at the nose part of pinion cutter. Increasing of rotary feed and radial feed rate alleviated the concentration of chipping at nose and prolonged tool life.