• Journal of Aerospace System Engineering
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• v.14 no.spc
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• pp.22-30
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• 2020

Composite rotor blades for rotorcraft have an intrinsic vulnerability to foreign object impact from its inherent structural characteristics of insufficient strength in the thickness direction, which may easily lead to internal structure damage. Therefore, defects and strength reducing effects caused by foreign object impact should be considered in fatigue evaluation of composite blades. For this purpose, the flaw tolerant safe-life and fail-safe concepts were adopted in fatigue evaluation since 1980s, and recently those concepts have been replaced by the damage tolerance concept. In this paper, the relevant standards for fatigue evaluation are analyzed focusing on fiber reinforced composite rotor blades used in rotorcraft. In addition, fatigue evaluation procedure of composite blades considering impact damages is proposed by reviewing the practices implemented through domestic development projects.

• The Korean Journal of Air & Space Law and Policy
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• v.35 no.1
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• pp.153-180
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• 2020

This study is meaningful in finding out what legal and policy issues need to be improved in order to foster the aircraft industry, which is relatively underdeveloped compared to the fact that some heavy industries, such as the automobile industry and shipbuilding industry, have achieved a high level of production and technology globally. Korea's aircraft industry has been growing at a slower pace than other industries, largely due to the country's economic growth and the lack of a market structure to properly use variables such as the level of development in related industries, aircraft technology and demand for aircraft manufacturing. While most industries are privately led by the market structure of the competition system, heavy industries such as the aircraft industry generally grow under the market structure of the incomplete competition system, because only by securing huge initial investment costs, high technology, and sufficient demand, they can maintain minimum economic feasibility. The Korean aircraft industry was focused on developing and mass-producing military aircraft focusing on military demand, but it sought to turn the tide by signing the BASA (Bileral Aviation Safety Agreement) with the U.S. A preliminary feasibility study was conducted in 2010 to develop next-generation medium-sized aircraft, but was cancelled due to differences in position with Canada's Bombardier, which is subject to the concourse, and Korea Aerospace Industries (KAI) is pushing for the production of Bombardier's Q400 license on its own. Compared to the mid-to-large sized civil aircraft that are facing difficulties in development, KAI and KARI are successfully developing technologies to unmanned aerial vehicles and civil helicopters. In addition, the unmanned aerial vehicle sector is not yet suitable for manufacturers that have an exclusive global influence, so we believe that it is necessary to pursue government-led research and development projects with a focus on the areas of commercial helicopters and unmanned aerial vehicles in order to foster the aircraft industry in the future. In addition, since military aircraft such as KT-1 and T-50 are currently being exported smoothly, and it cannot be overlooked that the biggest demand for aircraft manufacturing in the Korea is the military, it is necessary to push forward national R&D projects and defense R&D program simultaneously to enable both civilian-military development. However, there are many differences between the two projects in the way they are implemented, the department in charge and the royalty system. Through this study, we learned about the technology ownership and implementation rights of national R&D projects and defense R&D programs, as well as the royalty system. In addition, problems with the system were identified and improvement measures were derived.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.6
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• pp.67-72
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• 2020

Life tests are essential in reducing the catastrophic damage caused by the accidents of large machinery such as aircraft and ships. However, life tests are challenging to implement due to the high costs and time required to test the life of large machinery parts. Therefore, it is advantageous and convenient to apply accelerated life test techniques for key components to reduce costs and time. In fact, extensive research has already been conducted on these techniques. However, recently, there have been cases in which an experimental value was applied to the shape parameter of the Weibull distribution used in the reliability test, but the test time was not significantly reduced. Therefore, in this paper, the shape parameters are estimated from the probability density function of the Weibull distribution for the analysis of an accelerated life test for bladder accumulators, which are core components of military helicopters. The test time was derived based on the number of samples and confidence level by substituting it into the test time equation. Next, the accelerated life test time was calculated using the steady-state test time with an acceleration factor obtained from the Arrhenius model. The steady-state life test required approximately 15,000 H, whereas the accelerated life test time for one sample at 100 ℃ was 34% shorter than that of the steady-state life test.

• 산림경영
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• s.139
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• pp.20-23
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• 1999

산림청에서는 백두대간을 체계적으로 보전하고 골프장 설치등으로 산림이 무분별하게 훼손되는 일이 없도록 하기 위하여 '산림피해 확대방지 종합대책'을 수립$\cdot$시행한다고 밝혔다. 산림청은 그동안 많은 논란이 있었던 백두대간의 실체규명과 보전을 위하여 백두대간의 개념 및 보전에 필요한 사항 등을 2000년중으로 정립, 제도화하는 방안을 강구키로 하였다. 또한 건설교통부가 국토이용계획을 변경하고자 산림청과 협의할 때 적용하는 산림청의 '국토이용계획변경 협의기준'을 강화하는 내용으로 금년 하반기에 개정하기로 하였다. 스키장$\cdot$골프장 등 설치로 백두대간이 훼손되지 않도록 백두대간 마루금 침범을 금지하는 내용으로 개정하고 집단묘지개발시 피해유발 우려가 있는 경사 30$\%$이상지역, 마사토지역과 경관지역은 묘지개발을 금지하게 할 계획이다. 또한 무분별한 산림형질변경을 제도적으로 방지하기 위하여 현행 시장$\cdot$군수로 되어 있는 산림형질변경허가권자를 시$\cdot$도지사로 상향하는 내용으로 금년중 산림법 시행령을 개정하기로 하였다고 밝혔다. 특히 각종 개발사업 추진과정에서 장마철 집중호우로 인한 수해가 발생하지 않도록 하기 위하여 1년 이상 공사중단된 골프장은 6월중에 일제조사를 실시하여 장마철 집중호우시 수해위험에 있는 골프장에 대하여는 시$\cdot$도지사에게 요청하여 사업승인을 취소하거나 사업중지토록 할 계획이다. 산림경영 기반시설인 임도에 대하여는 피해방지 및 경관유지를 최우선하는 '환경친화적 녹색임도' 정책으로 전환하기 위하여 기존의 부실 임도에 대하여는 7월부터 대대적인 구조개량 사업에 착수하고, 내년부터는 임도계획 단계부터 노선등의 적정여부를 사전평가하는 제도를 도입하겠다고 밝혔다. 최근 산림훼손으로 문제되고 있는 송전탑진입로는 산림 형질변경허가를 엄격하게 운용하기 위하여 앞으로는 한국전력으로 하여금 진입로 설치 대신 삭도$\cdot$모노레일$\cdot$헬기운반을 대폭 확대하도록 조치하였으며 또한 이미 공사완료한 곳 중 피해방지$\cdot$경관유지가 필요한 경우에는 한국전력으로 하여금 설계를 변경하여 추가공사를 하도록 협의완료하였다고 산림청은 밝혔다.

• Journal of the Korea Society for Simulation
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• v.23 no.4
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• pp.75-83
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• 2014

Most warship combat systems inquire human operator to control several sensor and another equipments as well as decision-modeling. For this reason, many researches with multi-agent based M&S (Modeling and Simulation) have been increasingly conducted. However there cannot find any researches of M&S based analysis for anti-submarine warfare that requires a high level of mission complexity between multiple platforms. In this research, we have been developed various combat platform models such as warship, submarine and helicopter, etc. In order to apply the multi-agent-based M&S technology to the anti-submarine warfare i.e. a HVU (High Value Unit) escort mission scenario. Then we have successfully analyzed the measures of effectiveness according to the different tactics and different situations. In future, the defence engineer maybe employ our methodology and tools to analyze actual tactical problem by simply inserting actual data into our agent model.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.71-78
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• 2014

There is a big risk of bullet impact because military rotorcraft is run in the battle environment. Due to the bullet impact, the rapid increase of the internal pressure can cause the internal explosion or fire of fuel cell. It can be a deadly damage on the survivability of crews. Then, fuel cell of military rotorcraft should be designed taking into account the extreme situation. As the design factor of fuel cell, the internal fluid pressure, structural stress and bullet kinetic energy can be considered. The verification test by real object is the best way to obtain these design data. But, it is a big burden due to huge cost and long-term preparation efforts and the failure of verification test can result in serious delay of a entire development plan. Thus, at the early design stage, the various numerical simulations test is needed to reduce the risk of trial-and-error together with prediction of the design data. In the present study, the bullet impact numerical simulation based on SPH(smoothed particle hydrodynamic) is conducted with the commercial package, LS-DYNA. Then, the resulting equivalent stress, internal pressure and bullet's kinetic energy are evaluated in detail to examine the possibility to obtain the configuration design data of the fuel cell.

• The Korean Journal of Emergency Medical Services
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• v.11 no.3
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• pp.93-109
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• 2007

The pre-hospital care in site transportation care and site care will be divided, it will follow in site or evacuation it will enforce it will can evacuate in condition of the emergency patient of like this at the initial stage and emergency care from inside fire fighting helicopter back transfer means and the manpower security of the specialty emergency necessary personnel(nursing and 1st EMT's) as the medical treatment agency and modernization of first aid equipment necessity inside American securing and fire fighting helicopter and specialty first aid packet won about lower the emergency care which is appropriate cannot become accomplished are the actual condition in total lack of emergency care equipment. Consequently craving augmentation, in order to be adapted with the handling kind transfer whose specialty and is appropriate and present time of rapid increase and the citizen of emergency demand by fire fighting helicopter simplicity transfer compared to it is a condition where the countermeasure preparation is earnest. Must expand emergency care equipment first even in fire fighting helicopter and 1st EMT's which it follows in him become arrangement and quickly the execution and specialty temporary disposal(ALS) must be enforced a temporary disposal and must buy the life which is. Also it gets by experience a helicopter induction outline, a radio communication method and the patient helicopter on-board hour attention point back various attention fact back with the body and when where it stands but accurately there must be it will be able to induce the helicopter. Also every manuals anger it does a helicopter transfer method and the emergency care method back and that all processes must do fixed form anger, it becomes feed. Also it related with a helicopter transfer even from the relationship agency many research to lead, difference of the advanced foreign nation and the maximum it is the actual condition where the medical emergency system construction which it reduces is earnestly demanded. Also with emergency structure(crane) it confronts to an aviation transfer even from the establishment college and education it leads intensively and 1st EMT's of the good quality which relates with an aviation structure expects is cultivate at all.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1275-1282
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• 2012

Helicopter rotor systems are dynamically loaded structures with many composite components such as the main and the tail rotor blades. The fatigue properties of composite materials are extremely important to design durable and reliable helicopter rotor blades. The safe-life methodology has generally been used in the helicopter industry to substantiate dynamically loaded composite components. However, it cannot be used to evaluate the strength reducing effects of flaws and defects that may occur during manufacturing and operational usage. The damage tolerance methodology provides a proper means to overcome this shortcoming; however, it is difficult to economically apply it to every composite component. The flaw tolerant methodology is an equivalent option to the damage tolerance methodology for civil and military rotorcraft. In this study, the flaw tolerant safe-life evaluation is described and illustrated by means of successful application to substantiate the retirement time of composite rotor blades.

• Korean Journal of Environment and Ecology
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• v.31 no.1
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• pp.93-103
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• 2017

The purpose of this study is to assess the recovery rate of vegetation structure after restoration works at the damaged Nogodan area in Jirisan National Park. Fourteen monitoring plots were set up at restoring work area and twelve control plots were set up at natural forest near monitoring plots. Flora, Relative Importance Percentage and Similarity Index were analyzed. Mean Similarity Index between monitering plot and control plot near helliport area showed thirty five point two percent and height of shrub layer recovered up to twenty percent, approxomately durindg twenty three years after experimental restoration works. Mean Similarity Index between monitering plot and control plot around Nogodan peak area showed seventeen point six percent but height of shrub layer recovered up to twenty percent, approxomately during ninteen years after restoration works. Mean similarity index between monitering plot and control plot on transfered millitary area showed thirty four point three percent but coverage of shrub layer showed twenty percent,approxomately during seven years after restoration works. Long term monitering shall be necessary for developing assessment criteria of ecologial restoration and ecological restoration technology.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.8
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• pp.759-769
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• 2013

Electronic equipment has been applied to virtually every area associated with commercial, industrial, and military applications. Specifically, electronics have been incorporated into avionics components installed in aircraft. This equipment is exposed to dynamic loads such as vibration, shock, and acceleration. Especially, avionics components installed in a helicopter are subjected to simultaneous sine and random base excitations. These are denoted as sine on random vibrations according to MIL-STD-810F, Method 514.5. In the past, isolators have been applied to avionics components to reduce vibration and shock. However, an isolator applied to an avionics component installed in a helicopter can amplify the vibration magnitude, and damage the chassis, circuit card assembly, and the isolator itself via resonance at low-frequency sinusoidal vibrations. The objective of this study is to investigate the dynamic characteristics of an avionics component installed in a helicopter and the structural dynamic modification of its tray plate without an isolator using both a finite element analysis and experiments. The structure is optimized by dynamic loads that are selected by comparing the vibration, shock, and acceleration loads using vibration and shock response spectra. A finite element model(FEM) was constructed using a simplified geometry and valid element types that reflect the dynamic characteristics. The FEM was verified by an experimental modal analysis. Design parameters were extracted and selected to modify the structural dynamics using topology optimization, and design of experiments(DOE). A prototype of a modified model was constructed and its feasibility was evaluated using an FEM and a performance test.