• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.715-722
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• 2011

In this paper, the behavior of nuclear-power plant subjected to an aircraft impact is performed using the parallel analysis. In the erstwhile study of an aircraft impact to the nuclear-power plant, it has been used that the impact load is applied at the local area by using the impact load-time history function of Riera, and the target structures have been restricted to the simple RC(Reinforced Concrete) walls or RC buildings. However, in this paper, the analysis of an aircraft impact is performed by using a real aircraft model similar to the Boeing 767 and a fictitious nuclear-power plant similar to the real structure, and an aircraft model is verified by comparing the generated history of the aircraft crash against the rigid target with another history by using the Riera's function which is allowable in the impact evaluation guide, NEI07-13(2009). Also, in general, it is required too much time for the hypervelocity impact analysis due to the contact problems between two or more adjacent physical bodies and the high nonlinearity causing dynamic large deformation, so there is a limitation with a single CPU alone to deal with these problems effectively. Therefore, in this paper, Message-Passing MIMD type of parallel analysis is performed by using self-constructed Linux-Cluster system to improve the computational efficiency, and in order to evaluate the parallel performance, the four cases of analysis, i.e. plain concrete, reinforced concrete, reinforced concrete with bonded containment liner plate, steel-plate concrete structure, are performed and discussed.

• Journal of Korean Society of Transportation
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• v.28 no.3
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• pp.51-57
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• 2010

In this study, damages due to the aircraft noise were examined in more than 190 elementary, middle and high schools near the airports in Korea, and the persecutory idea forecast model was established using the quantification theory type II. Via the survey of 1,012 teachers in the schools, a class interference forecast model was established, and the noise characteristics of five areas, four military/civil common-use airports and one shooting range, were examined. The following conclusions were made from the study. WECPNL values in the five military/civil common-use airports showed that all of them were Class 1 or 2 affected areas, which indicated that they had serious aircraft noise problems to be addressed. The most influential factor in the aircraft noise persecutory idea model was the distance between the airport and the school. It showed a positive relationship at a distance of less than 5 km, and a negative relationship at a distance of 10 km or more. The number and time of aircraft noise exposure as well as the types of airports and window structures had strong influences. The forecast model had a correlation ratio of 0.56, which indicates that it is highly appropriate. In the class interference factor analysis, the time and number of aircraft noise exposure were strong influential factors, and the results varied according to the service duration and sex of teachers. This model had a correlation ratio of 0.61, which indicates it is highly appropriate.

• Advances in aircraft and spacecraft science
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• v.7 no.5
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• pp.405-423
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• 2020

Non-linear energy sink (NES) is an emerging passive absorber able to mitigate the dynamic response of structures without any external energy supply, resonating with all the modes of the primary structure to control. However, its inherent non-linearities hinder its large-scale use and leads to complicated design procedures. For this purpose, an approximate design approach is herein proposed in a stochastic framework. Since loads are random in nature, the stochastic analysis of non-linear systems may be performed by means of computational intensive techniques such as Monte Carlo simulations (MCS). Alternatively, the Stochastic Linearisation (SL) technique has proven to be an effective tool to investigate the performance of different passive control systems under random loads. Since controlled systems are generally non-classically damped and most of SL algorithms operate recursively, the computational burden required is still large for those problems that make intensive use of SL technique, as optimal design procedures. Herein, a procedure to speed up the Stochastic Linearisation technique is proposed by avoiding or strongly reducing numerical evaluations of response statistics. The ability of the proposed procedure to effectively reduce the computational effort and to reliably design the NES is showed through an application on a well-known case study related to the vibrations mitigation of an aircraft wing.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.25 no.3
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• pp.35-43
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• 2017

Research for solar-powered high altitude long endurance(HALE) UAV was conducted by Korea Aerospace Research Institute(KARI), and the EAV-3 with 19.5m wing span was developed. For HALE flight, aircraft should be lightly designed. Especially, airframe structure that accounts for a large portion of the total weight of aircraft should be lightweight. In this paper, development process of airframe structure for solar-powered HALE UAV, EAV-3, is described briefly. Domestic developed T-800 grade CFRP(Carbon Fiber Reinforced Plastic) composite material with high modulus and strength was used to design main load carrying structures. Flightloads analysis that takes into account large structural deformation was carried out. Stress and flutter analyses for airframe structure sizing were conducted. Static strength test for main wing and aircraft ground vibration test were conducted successfully and structural integrity was secured.

• Advances in aircraft and spacecraft science
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• v.5 no.6
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• pp.633-652
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• 2018

The present paper focuses on the development of a model for simulating the thermoelectric behavior of CNTs/CFRP Organic Matrix Composite (OMC) laminates for aeronautical applications. The model is developed within the framework of the thermodynamics of irreversible processes and implemented into commercial ABAQUS Finite Element software and validated by comparison with experimental thermoelectric tests on two types of composites materials, namely Type A with Carbon Nanotubes (CNT) and Type B without CNT. A simplified model, neglecting heat conduction, is also developed for simplifying the identification process. The model is then applied for FEM numerical simulation of the thermoelectric response of aircraft panel structures subjected to electrical loads, in order to discuss the potential danger coming from electrical solicitations. The structural simulations are performed on quasi-isotropic stacking sequences (QI) $[45/-45/90/0]_s$ using composite materials of type A and type B and compared with those obtained on plates made of metallic material (aluminum). For both tested cases-transit of electric current of intermediate intensity (9A) and electrical loading on panels made of composite material-higher heating intensity is observed in composites materials with respect to the corresponding metallic ones.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.4
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• pp.1-8
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• 2020

Mechanical components that support structures in aerospace and power generation industries require high-strength materials. Particularly, in the aerospace industry, aluminum alloys, titanium alloys, and composite materials are increasingly used due to their high maneuverability and durability to withstand low temperature extreme environments; however, ultra-high-strength steel is still used in key components under heavy loads such as landing gears. In this paper, the fault cause analysis and troubleshooting of aircraft parts made of ultra-high-strength steel (300M) broken during normal operation are described. To identify the cause of the defect, a temporary inspection of the same aircraft was performed, and material testing, non-destructive inspection, microstructure examination, and fracture area inspection of the damaged parts were performed. Fracture analysis results showed that a crack in the shape of a branch developed from the tool mark in the direction of the intergranular strain. Based on the results, the cause of fracture was confirmed to be stress corrosion.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.2
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• pp.179-186
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• 2012

The potential hazards resulting from a low-velocity impact(bird-strike, tool drop, runway debris, etc.) on aircraft structures, such as engine nacelle or leading edges has been a long-term concern to the aircraft industry. Certification authorities require that exposed aircraft components must be tested to prove their capability to withstand low-velocity impact without suffering critical damage. In most of the past research studies unloaded specimens have been used for impact tests, however, in reality it is much more likely that a composite structure is exposed to a certain stress state when it is being impacted, which can have a significant effect on the impact performance. And the radiated impact sound induced by impact is analyzed for the damage detection evaluation. In this study, an investigation was undertaken to evaluate the effect in-plane loading on the impact force and sound of composite laminates numerically.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.7
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• pp.535-540
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• 2019

The coupling between different models for MDO (Multi-disciplinary Optimization) greatly increases the complexity of the computational framework, while at the same time increasing CPU time and memory usage. To overcome these difficulties, POD (Proper Orthogonal Decomposition) and RBF (Radial Basis Function) are used to solve the optimization problem of determining the thickness of composites and sandwich cores when composite sandwich structures are used as aircraft wing skin materials. POD and RBF are used to construct surrogate models for the wing shape and the load data. Optimization is performed using the objective function and constraint function values which are obtained from the surrogate models.

• Journal of Aerospace System Engineering
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• v.15 no.1
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• pp.47-55
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• 2021

When an abnormal landing occurs, aircraft structures should be designed to guarantee occupants survivability without preventing egress. To find out fire root causes at crash, lots of fixed aircraft crash tests were conducted. Appropriate crash load factors were established with the comprehension of structural behavior based on dynamic analysis and investigation of human tolerance. Cargo restraint criteria were set up considering passengers safety and operational cost while analyzing past cargo aircraft accident data using a probabilistic approach. Reviewing results of past crash tests, current crash landing load factor was appreciated physically, medically, and economically.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.101-106
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• 2002

Requirements to fabrication processes for arc welding of highly loaded thick-walled joint and problems of research and development in term s of the tendency for the modern aircraft structure development are outlined. A justified, choice of the development line of the new promising welding processes for solution of these problems is presented. A complex of new welding processes and technologies for making highly reliable joints with different thickness (up to 120 mm and more) and length of weld (up to 0.1 m; 0.1-0.5 m and more than 0.5 m) has bee developed. It is shown that the possibility to control the heat flow distribution over the groove surface of the welded joints provides for improved reliability. The new welding processes are equipment are effectively used in serial production of the Mykoyan md Sukhoi supersonic aircrafts as well as in AN-124 Ruslan and AN-225 Mriya wide body aircrafts.