• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.367-367
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• 2015

토석류는 바위, 자갈, 토사 등이 물과 혼합하여 흐르는 재해 현상이다. 근래에 이슈가 되었던 우면산 토석류사태, 춘천시 펜션 토석류재해로 인한 피해로 토석류에 대한 국민적 관심이 높아지게 되었다. 토석류의 피해를 저감하기 위한 대표적 시설로는 사방댐, 링네트, 브레이커시스템 등의 다양한 저감시설이 있다. 2000년 이후 국내에는 사방댐 형태의 토석류 유출저감시설의 설치가 매년 증가하고 있다. 그러나 대부분의 사방시설은 표준화된 설계기준에 의해 시공되기 보다는 단순한 검토만을 통해 시공되고 있어 관리적인 측면에서 문제점이 대두되고 있다. 또한 대부분 구조적인 안정성 검토는 이루어지고 있으나 수리적인 특성을 고려한 검토는 미흡한 실정이다. 따라서 본 연구에서는 수리 실험 연구를 진행하기 위한 실험계획을 수립하고, 수리실험에 사용할 토석류 유출 저감시설 축소모형을 제작하였다. 모형의 제작 방법으로는 최근 다양한 분야에 활용되며, 널리 보급 되고 있는 3D프린터를 이용하였다. 3D프린터는 레이어를 한 장씩 쌓는 과정으로 제작되어 정밀하고 세밀한 모형물을 제작할 수 있다. 이러한 특성을 활용하여 기존에 단순화 시켜 제작되던 모형을 실제와 거의 동일한 형태로 제작하였다. 본 연구에서는 3D 프린터로 제작된 실험용 모형을 이용하여 토석류 유출저감시설의 토석류 저감효과 분석을 위한 기초 수리실험을 수행하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1207-1212
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• 2015

A vibro ripper utilizes high-frequency vibration for rock fragmentation. This concept is different from those used by other existing breakers. The gearbox-shank welded joint of a vibro ripper is a very important part. Because it delivers the vibromotive force to the tooth, it is important to predict its soundness. This study was conducted to predict the fatigue life under welding conditions. The shank materials were Hardox-Hituf and AR400, and the filler metals were CSF-71T and CSF-81T. Fatigue tests were conducted under each set of conditions. P-S-N curves are presented based on the statistical testing method recommended by JSME-S002, and a comparison is made of the results under each set of conditions. The life was estimated using a P-S-N curve.

• Korean Journal of Construction Engineering and Management
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• v.4 no.4 s.16
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• pp.173-181
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• 2003

During the last few years, the use of Pre-tensioned spun high strength concrete piles(PHC pile) has been gradually increased in many construction sites. Cutting work of the concrete pile is an important task to crush a part of pile head which is compressed with more than 800$\cal{kg}f/cm^2$. It is usually performed by a crusher and three to four skilled workers. Recent analysis results of the pile cutting work reveal that it frequently makes a lot of cracks which significantly reduce the strength of the pile and is labor-intensive work. The primary objective of this study is to propose conceptual designs for developing an automated pile cutting machine. It is anticipated that the development of the automated pile cutting machine would be able to bring improvements in safety, productivity, quality as well as cost saving.

• Design & Manufacturing
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• v.12 no.1
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• pp.41-46
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• 2018

This study proves the causes of cylinder and piston jam by scratches which is the fatal problem of hydraulic breaker through the thermal analysis and thermal-structural coupled field analysis. The trouble from the scratch is a complex problem which can be caused by manufacturing process (this is an internal factor) and the users mistake or contamination in the hydraulic circuit (these are an external factor). Hence, it's not easy to investigate the causes, also hard to prevent the recurrence. In this reason, hydraulic breaker manufacturers are trying to improve the manufacturing process such as machining, heat treatment, grinding, cleaning, also to prevent the contamination in hydraulic circuit and to remove the remains. It's being managed thoroughly by manufacturers. This study shows the effect of the temperature rise by the frictional heat generated when the piston hits the tool on the hydraulic oil while the hydraulic breaker is operating, also the temperature distribution when it starts to affect main components of hydraulic breaker. The stress and the amount of deformation also could be found through thermal-structural coupled field analysis. It proved that the stress and deformation are proportionally increased according to the temperature rise in hit area, and it affects the cylinder and the viscosity of hydraulic oil inside the cylinder when it heats up beyond the certain temperature.

• Tunnel and Underground Space
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• v.29 no.3
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• pp.135-147
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• 2019

This paper introduced a impact load estimation method by examining vibration transfer path analysis (TPA). The theoretical background and the load quantification procedure are explained, and a case study of hydraulic breaker is reported. We explained the merits and limitations of the load estimation method of TPA, and improvement method was suggested through case analyses of drilling equipment. The necessity of R&D of load-estimation technology was discussed. A new strategy for developing new techniques for impact load measurement was proposed.

• Explosives and Blasting
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• v.39 no.4
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• pp.1-11
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• 2021

In this study, the vibration data were obtained to analyze the vibration generated during dismantling of slab using the mechanical dismantling method. The obtained vibration data were classified according to the attachment device and then the waveform and dominant frequency analysis were performed. And the correlation was analyzed by the different methods of measuring the distance between the work section and the measurement point. As a result of the waveform analysis for each attachment device, there was little change in the phase of the vibration waveform and only the change in amplitude, which is the magnitude of the vibration velocity. And as a result of frequency analysis, the frequency band was lower when using a crusher method than a braker method and frequency band were close of the natural frequency of the structure to be dismantled. As a result of the correlation analysis, the separation distance was estimated a higher correlation when evaluated as the path through which the vibration propagates along the structure frame than the straight distance between the measurement point and the working section.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.415-427
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• 2021

This technical report briefly introduced the rock cutting splitting method under development. This method is a method of excavating the rock by splitting the block after the rock cutting process. After designing the cutting geometry of the rock face, the chisel is press-fitted to remove the rock block. At this time, when the cutting block is properly designed, the tensile crack propagates smoothly at the bottom of the rock block. An analytical solution was devised to estimate the indentation force required for splitting rock blocks using fracture toughness mode 1 required for tensile crack growth. The impact force of the hydraulic breaker of the excavator was analyzed, and the grade of the excavator that can be constructed according to the rock block design geometry was analyzed.

• Journal of the Korea Fashion and Costume Design Association
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• v.25 no.3
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• pp.81-95
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• 2023

The purpose of this study is to analyze the newtro fashion style and extract key descriptive terms for visual image evaluation based on the style. To achieve this, a literature review, case study, and survey were conducted. The results are as follows: 1) Newtro fashion exhibited a variety of styles depending on the items being considered. In particular, the windbreaker style is composed of windbreakers, sweatshirts, and training pants, the blazer style consists of blazers, sweatshirts, and denim pants, and the padding style is characterized by short padding, sweatshirts, and jogger pants. 2) A total of 28 terms were identified as vocabulary to represent the visual images of newtro fashion. Among these, 17 terms appeared with a frequency of 30 or more times across the three styles. Commonly used terms included 'emotional', 'desirable', 'empathetic', 'unique', 'moody', 'retro', 'sophisticated', 'stylish', 'vintage', 'confident', 'youthful', 'trendy', and 'modern'. 3) By examining terms with a frequency of 50 times or more, the visual images associated with each style were compared. For the windbreaker style, the newtro fashion image was predominantly described as 'desirable', 'youthful', 'modern', 'stylish', and 'emotional'. The blazer style was associated with 'retro', 'unconventional', 'stylish', 'trendy', 'empathetic', 'modern', 'intricate', and 'unique'. In the padding style, the newtro fashion image was characterized as 'youthful', 'intricate', 'cute', 'stylish', 'modern', 'unique', and 'confident'.

• Journal of Korean Society of Forest Science
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• v.87 no.1
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• pp.82-89
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• 1998

This study was carried out to investigate working time, performance, and to predict performance that related to the factor of forest road in earth work using excavator. It was found that the real working time was 503 minutes in a day. The ratio of real working time and allowance per total working time was approximately 85.7% and 14.3% individually. The rate of soil movement(Sm) to net working time was 38.6%, and earth cutting(Ec) was 32.5%. According to performance analysis, performance of earth work using excavator($0.8m^3$) in straight part was 1.4 times larger than curve part and rock work using excavator($0.8m^3$) which had breaker in straight was 9.1 times larger than earth work using excavator($0.8m^3$) which had bucket. Performance of earth work using excavator($1.0m^3$) was 1.3 times larger than using excavator($0.8m^3$) in straight and curve part. Working performance in earth work using excavator($0.8m^3$) was influenced by the conditions of radius of curve, width of roadway, slope gradient. It is not influenced by diameter and number of root stock.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.672-679
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• 2018

This paper describes a methodology for shape design using an optimal design system, whereas generally a three dimensional analysis is required for such designs. An automatic finite element mesh generation technique, which is based on fuzzy knowledge processing and computational geometry techniques, is incorporated into the system, together with a commercial FE analysis code and a commercial solid modeler. Also, with the aid of multilayer neural networks, the present system allows us to automatically obtain a design window, in which a number of satisfactory design solutions exist in a multi-dimensional design parameter space. The developed optimal design system is successfully applied to evaluate the structures that are used. This study used a stress gauge to measure the maximum stress affecting the parts of the side housing bracket which are most vulnerable to cracking. Thereafter, we used a tool to interpret the maximum stress value, while maintaining the same stress as that exerted on the spot. Furthermore, a stress analysis was performed with the typical shape maintained intact, SM490 used for the material and the minimizing weight safety coefficient set to 3, while keeping the maximum stress the same as or smaller than the allowable stress. In this paper, a side housing bracket with a comparably simple structure for 36 tons was optimized, however if the method developed in this study were applied to side housing brackets of different classes (tons), their quality would be greatly improved.