• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2001.10a
• /
• pp.51-56
• /
• 2001

This work describes reduction of disturbance created by driving actuator in milling process. To the end, controller includes disturbance dynamics. Experimently it is shown that steady disturbance can be rejected to a certain degree.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.7
• /
• pp.151-157
• /
• 1999

Vibrations in machine tools make many problems in precision, production efficiency, and machine performance. The relative vibration between a workpiece and a tool is very complicated due to many sources. In this study, the dynamic characteristics of a newly developed CNC lathe were analyzed and its chatter characteristics were predicted by a chatter analysis method using finite element analysis and 3 dimensional cutting dynamics. The simulated results showed very complex characteristics of chatter vibration and the borderline of limiting depth of cut was used as the stability limit. To check the validity of this method, cutting tests were done in the CNC lathe using a boring bar as a tool because boring process is very weak due to long overhang . The experimental results showed that the simplified borderline was to be considered as limiting depth of cut at which the chatter vibration starts and the stability limits depended on various cutting parameters such as cutting speed, feed and nose radius of tool.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.20 no.10
• /
• pp.88-94
• /
• 2021

Machining operations require the removal of chips to keep the water-soluble cutting oil clean and fresh throughout the operation time. Water-soluble cutting oil for metal processing is diluted using a 3-8% solution in water which is generally replaced every three to six months. This study aims to develop multiple purification devices to efficiently remove fine contaminating particles from water-soluble cutting oil. The 2D concept designs were created using AutoCAD. The designs were drawn using the 3D modelling feature of CATIA. Flow analysis was performed in a bubble purifier using Ansys computational fluid dynamics (CFD). This analysis has aided in improving the design and structure of the device to create the final prototype. Experiments were conducted to check the prototype's performance. Comparisons of the effects of each process variable on the experiment was carried out using ANOVA.

• Journal of Korean Society of Forest Science
• /
• v.94 no.1 s.158
• /
• pp.6-10
• /
• 2005

This study was conducted to understand the dynamics of naturally regenerated seedlings and saplings in 28years after selective cutting at natural Korean pine-broadleaved forests in Mt. Changbai. The number of naturally regenerated tree species was 16 species in 28 years after selective cutting. The appearance rate of naturally regenerated tree species was 56 percentage and the early-successional tree species of Acer ukurunduense, Acer mono, Acer pseudosieboldianum, Prunus padus var. pubescens, and Maackia amurensis were found in the first 10 years after selective cutting. The seedlings and saplings of shade-tolerant tree species of Pinus koraiensis, Acer mandshuricum, Ulmus laciniata were appeared and the appearance rate was higher than 75% after 15 years while it showed little changes from 19 years after selective cutting. The distribution density of seedlings and saplings of regenerated tree species in selective cutting area was 5,500~6,100 trees per hectare in the first 10 years, and it increased gradually along with the restoration of disturbed area and it could reach 7,500 trees per hectare after 15 years.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1993.10a
• /
• pp.83-88
• /
• 1993

Recently, the analysis of microcutting with submicrometer depth of cut is tried to get a more high quality surface product, but to get a valuable result another method instead of conventional finite element method must be considered because finite elment method is impossible for a very small focused region and mesh size. As the altermative method, Molecular Dynamics or Statics is suggested and acceoted in the field of microcutting, indentation and crack propagation. In this paper using Molecuar Dynamics simulation, the phenomena of microcutting with subnanometer chip thickness is studied and the cutting mechanism for tool edge configuration is evaluated. As the result of simulation the atomistic chip formation is achieved.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.7
• /
• pp.685-692
• /
• 2016

A cutting head is an attachment on the front of an excavator that cuts or grinds rocks. Cutting tools, called pick cutters, are arranged on the surface of the cutting head. The exact arrangement and configuration of pick cutters is one of the most important factors in determining grinding efficiency. This study focuses on the problem of automation for pick arrangement design, in order to make the design process more efficient and convenient. Design automation was carried out using RecurDyn/ProcessNet, and it was composed of three parts: 'Drum set', 'Pick load', and 'Pick arrangement' sections. The presented method helps to decrease costs attributed to designing cutting heads and can be used to generate a wide range of attachment mechanisms.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.199-202
• /
• 2005

High speed milling process is emerging as an important fabrication process benefits include the ability to fabricate micro and meso-scale parts out of a greater range of materials and with more varied geometry. It also enables the creation of micro and meso-scale molds for injection molding. Factors affecting surface roughness have not been studied in depth for this process. A series of experiments has been conducted in order to begin to characterize the factors affecting surface roughness and determine the range of attainable surface roughness values for the high speed milling process. It has previously been shown that run-out creates a greater problem for the dimensional accuracy of parts created by high speed milling process. And run-out also has a more significant effect on the surface quality of milled parts. The surface roughness traces reveal large peak to valley variations. This run-out is generated by spindle dynamics and tool geometry. In order to investigate the relationship between tool setting errors and surface roughness end tilted mills were used to cut aluminum samples. The results indicate that tool setting errors have significant effects on surface roughness and cutting forces.

• 한국전산유체공학회:학술대회논문집
• /
• 2011.05a
• /
• pp.508-511
• /
• 2011

Dust released from the rotating timber cutting process causes various kinds of diseases as well as safety issues. Although there were lots of efforts to reduce the amount of dust by installing large-sized dust collectors or by using expensive high-quality cutters, they proved to be not so effective. In this study we want to modify and improve the design of the rotary cutter system to prevent dust from being released to the environment as possible by using computational fluid dynamics (CFD) analysis. We have developed CFD models of the conventional cutter and several design modifications. Through the CFD analysis the characteristics of the air flow was predicted, and then the behavior of dust produced during the cutting process was analyzed for different designs. The most efficient design feature to capture dust inside the cutter as much as possible was chosen based on the CFD analysis results. Finally the prototype of the ratary saw machine was constructed and tested to check the dust capturing efficiency, which result is reasonably consistent with the predicted performance through the CFD analysis.

• Nuclear Engineering and Technology
• /
• v.50 no.7
• /
• pp.1088-1098
• /
• 2018

Kori unit #1, which is the first commercial nuclear power plant in Korea, was permanently shutdown in June 2017, and it is about to be decommissioned. Currently in Korea, researches on the decommissioning technology are actively conducted, but there are few researches on workers internal exposure to radioactive aerosol that is generated in the process of decommissioning nuclear power plants. As a result, the over-exposure of decommissioning workers is feared, and the optimal working time needs to be revised in consideration of radioactive aerosol. This study investigated the annual exposure limits of various countries, which can be used as an indicator in evaluating workers' internal exposure to radioactive aerosol during pipe cutting in the process of decommissioning nuclear power plants, and the growth and dynamics of aerosol. Also, to evaluate it, the authors compared/analyzed the cases of aerosol generated when activated pipes are cut in the process of nuclear power plants and the codes for evaluating internal exposure. The evaluation codes and analyzed data conform to ALARA, and they are believed to be used as an important indicator in deriving an optimal working time that does not excess the annual exposure limit.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.5 no.2
• /
• pp.16-21
• /
• 2006

In this study, the analytic realization of chatter mechanism using radial basis neural network(RBNN) was introduced and compared with the conventional stability analysis. In this regard, the FFT and time series spectrum analysis was used as a criterion for the existence of chatter in end-milling force. The desired coded outputs of chatter was trained and finally converged to desired outputs. The output of the RBNN match well with the conventional desired stability lobe. Using this trained data, the stability boundary of the radial basis neural network was acquired using the contour plotting. As a result, the proposed stability lobe boundary using RBNN consists well with the conventional analytical boundary that is calculated in characteristic equation of transfer function in chatter dynamics. In this RBNN analysis, two input and three output parameters were used in this paper.