• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.413-422
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• 1993

Air shipment affords the quickest possible delivery of horticultural products. The price of air shipped horticultural products are relatively high as most of these products are perishable. Usually the temperature in the cargo compartment is not controlled during flight. Thus, special attention should be paid to procooling prior to shipment. The environmental condition during transportation of horticultural products is an essential parameter for maintaining the quality of perishable products. Commonly horticultural products were loaded by ULD(Unit Load Devices) as a container or pallet in the aircraft (except for small aircraft) . Therefore, inside temperature of the container and cargo compartment came into question. Scarce literature on the relationship between environmental condition and quality changes of horticultural products during air shipment can be found. By the stand point of keeping fresh quality, investigations on the actual condition of air shipments were carried out to improve the technique during the distribution process of fresh horticultural products. Temperature, humidity, atmospheric pressure, carbon dioxide, ethylene, impacts, and changes in quality during the air shipment of snapbeans, okras and chrysanthemums were measured. Temperature was measured by recording thermometers, relative humidity by recording hygrometers, atmospheric pressure by a strain -guage type pressure sensor, carbon dioxide by testing tubes, ethylene by sampling bags and a gaschromatograph, impacts and vibrations by impact recorders and a 3D accelerometer. Relationships between environmental conditions and quality changes during air shipments were clarified. It was expected from investigations into actual shipments that the ventilation and insulation properties of air freight containers were related to the quality of agricultural products. Aircraft can no directly load and unload trucks into them. The transshipment is inclined to cause shocks and vibrations, and to invite damages within a short time.

• Advances in aircraft and spacecraft science
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• 제5권2호
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• pp.259-275
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• 2018

In mechanical analysis of spacecraft structures situations appear where static and dynamic loads must be considered simultaneously. This could be necessary either by load definition or preloaded structures. The superposition of these environments has an impact on the load and stress distribution of the analysed structures. However, this superposition cannot be done by adding both load contributions directly. As an example, to compute equivalent Von Mises stresses, the phase information must be taken into account in the stress tensor superposition. Finite Element based frequency response solvers do not allow the calculation of superposed static and dynamic responses. A manual combination of loads in a post-processing task is required. In this paper, procedures for static and harmonic loads superposition are presented and supported by analytical and finite element-based examples. The aim of the paper is to provide evidence of the risks of using different superposition techniques. Real application examples such as preloaded mechanism structures and propulsion system tubing assemblies are provided. This study has been performed by the Structural Engineering department of Airbus Defence and Space GmbH Friedrichshafen.

• Advances in aircraft and spacecraft science
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• 제6권2호
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• pp.145-156
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• 2019

As the industrial desire for a step change in productivity within the manufacture of composite structures increases, so does the interest in Through-Thickness Reinforcement technologies. As manufacturers look to increase the production rate, whilst reducing cost, Through-Thickness Reinforcement technologies represent valid methods to reinforce structural joints, as well as providing a potential alternative to mechanical fastening and bolting. The use of tufting promises to resolve the typically low delamination resistance, which is necessary when it comes to creating intersections within complex composite structures. Emerging methods include the use of 3D woven connectors, and orthogonally intersecting fibre packs, with the components secured by the selective insertion of microfasteners in the form of tufts. Intersections of this type are prevalent in aeronautical applications, as a typical connection to be found in aircraft wing structures, and their intersections with the composite skin and other structural elements. The common practice is to create back-to-back composite "L's", or to utilise a machined metallic connector, mechanically fastened to the remainder of the structure. 3D woven connectors and selective Through-Thickness Reinforcement promise to increase the ultimate load that the structure can bear, whilst reducing manufacturing complexity, increasing the load carrying capability and facilitating the automated production of parts of the composite structure. This paper provides an overview of the currently available methods for creating intersections within composite structures and compares them to alternatives involving the use of 3D woven connectors, and the application of selective Through-Thickness Reinforcement for enhanced damage tolerance. The use of tufts is investigated, and their effect on the load carrying ability of the structure is examined. The results of mechanical tests are presented for each of the methods described, and their failure characteristics examined.

• Composites Research
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• 제34권5호
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• pp.317-322
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• 2021

적층 복합재의 특성상 두께 방향 물성이 취약하여 비틀림, 저속충격, 피로 하중 등 복합 하중을 받게 되면 재료 내부의 미세크랙 진전을 통해 층간분리 현상이 발생하게 된다. 이를 방지하고자 Z-pinning, Stitching 등 다양한 3차원 보강 공법과 구조물의 미세균열을 실시간으로 검출하는 구조 건전성 감시 기법이 꾸준히 연구되고 있다. 본 논문에서는 I-fiber 스티칭 공법으로 보강된 Single-lap joint를 Co-curing 방법으로 제작하였으며, 제작된 시편의 강도 및 파손신호 검출 특성을 평가하였다. 균열과 파손신호 검출을 위하여 전기저항법과 AE법을 사용하였으며, 신호분석을 위한 전용회로를 제작하여 인장시험 중의 파손신호를 분석하였다. 실험결과, I-fiber 스티칭으로 보강된 Single-lap joint 시편은 보강이 없는 Co-cured single-lap joint 시편에 비해 강도가 약 44.6% 향상되었다. 또한, I-fiber로 보강된 Single-lap joint 시편은 강도 향상과 더불어 전기저항법과 AE법에 의한 파손 검출이 모두 가능하므로 파손 모니터링에도 효과적인 구조임을 확인하였다.

• 한국해양공학회지
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• 제14권3호
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• pp.29-34
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• 2000

This paper describes transient responses of a very floating structure subjected to dynamic load induced by waves. A time domain method is applied to the hydroelastic problems for this purpose. The method is based on source-dipole and FEM scheme and on Newmark $\beta$ method to pursuit time step process taking advantage of memory effect. The present procedure is carried out to analyze hydroelastic responses in regular waves and impact responses due to dropping aircraft.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 춘계학술대회 논문집
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• pp.18-22
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• 2000

This paper is transient motions of a very large floating structure subjected to dynamic load induced by wave. A time domain method is applied to the hydroelasticity problems for this purpose. The method is based on source-dipole and FEM scheme and on Newmark $\beta$ method to pursuit time step process taking advantage of the memory effect. The present method is appied to hydroelastic response analysis in regular waves and impact responses due to dropping aircraft.

• 한국생산제조학회지
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• 제20권6호
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• pp.740-744
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• 2011

Carbon-carbon composite material is the reinforced carbon fiber. Because of its high strength, elasticity and the excellent heat-resisting property in high temperature, carbon-carbon composite material has been used in many fields such as aerospace and automotive industries, etc. Especially, aircraft brake discs used at aerospace can be cracked due to its fatigue and vibration under various loading condition. This research is focused on the influence of the vibration of carbon-carbon composite material by using accelerometer with impact hammer excitation. And the change of vibration mode will be known by applying tensile loading test.

• Advances in aircraft and spacecraft science
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• 제4권2호
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• pp.93-124
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• 2017

Aeroelastic performance controls wing shape in flight and its behaviour under manoeuvre and gust loads. Controlling the wing‟s aeroelastic performance can therefore offer weight and fuel savings. In this paper, the rib orientation and the crenellated skin concept are used to control wing deformation under aerodynamic load. The impact of varying the rib/crenellation orientation, the crenellation width and thickness on the tip twist, tip displacement, natural frequencies, flutter speed and gust response are investigated. Various wind-off and wind-on loads are considered through Finite Element modelling and experiments, using wings manufactured through polyamide laser sintering. It is shown that it is possible to influence the aeroelastic behaviour using the rib and crenellation orientation, e.g., flutter speed increased by up to 14.2% and gust loads alleviated by up to 6.4%. A reasonable comparison between numerical and experimental results was found.

• Advances in aircraft and spacecraft science
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• 제9권1호
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• pp.1-15
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• 2022

This paper presents calibration of flush air data sensing systems during ascent period of a satellite launch vehicle. Aerodynamic results are numerically computed by solving three-dimensional time dependent compressible Euler equations over a payload shroud of a satellite launch vehicle. The flush air data system consists of four pressure ports flushed on a blunt-cone section of the payload shroud and connected to on board differential pressure transducers. The inverse algorithm uses calibration charts which are based on computed and measured data. A controlled random search method coupled with neural network technique is employed to estimate pitch and yaw angles from measured transient differential pressure history. The algorithm predicts the flow direction stepwise with the function of flight Mach numbers and can be termed as an online method. Flow direction of the launch vehicle is compared with the reconstructed trajectory data. The estimated values of the flow direction are in good agreement with them.

• 항공우주시스템공학회지
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• 제16권3호
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• pp.99-104
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• 2022

항공기 파일런은 엔진이나 외부장착물을 주날개에 연결하고 파일런 자체에 작용하는 하중을 항공기의 주구조물로 전달하는 역할을 한다. 또한, 긴급상황이나 임무수행시 파일런에 탑재된 외부장착물을 분리하는 기능도 수행할 수 있어야 한다. 만약, 외부장착물 분리과정에서 주변기류나 기능적 문제로 외부장착물의 분리가 적절히 수행되지 않으면 항공기 안전에 심각한 영향을 줄 수 있기 때문에 항공기 적용 전에 파일런으로부터 외부장착물의 분리 안정성이 입증되어야 한다. 본 논문에서는 외부장착물인 외부연료탱크가 파일런으로부터 안전하게 분리가 이루어질 수 있는지 확인하기 위해 수행된 지상분리시험 결과를 제시하였다. 시험 결과로, 외부연료탱크가 시험치구로부터 분리된 후 투하 움직임을 고속카메라로 계측하고, 파일런으로부터 외부연료탱크의 분리 안정성을 확인하였다. 또한, 해당 시험결과는 실제 항공기에서의 외부장착물 분리 안정성 평가에 대한 기초 데이터를 제공할 수 있을 것으로 판단된다.