• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.35-40
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• 2019

The objective of this paper is to identify the fatigue properties of carbon-fiber composite which is widely applied for the development of aircraft structures and obtain data for full-scale fatigue test. The durability and damage tolerance evaluation of composite structures is achieved by fatigue tests and parameters such as fatigue life factor and load enhancement factor. The specimens are made with carbon-fiber/epoxy UD tape and fabric prepreg. Fatigue tests are performed with several stress ratios and lay-up patterns. The Weibull shape parameters are analyzed by Sendeckyj model and individual fatigue lives with Weibull distribution. And the fatigue life factor and load enhancement factor considering reliability are evaluated.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2003.10a
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• pp.101-106
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• 2003

항공기 외부 장착물인 POD는 전자전 방해장치(ECM, electronic counter measures)로서 전자방해 장비 및 부분 부품인 전ㆍ후방 러그(lug)와 외부 케이스로 이루어져 있다. POD는 항공기 외부 동체 하단부 및 파일런(pylon)에 장착되어 작동하므로 항공기의 운용중 이륙부터 착륙간의 기동에 의한 피로하중을 주로 받게 되므로 POD 부품들에 대한 구조 건전성 확보하기 위해서는 MIL-STD-1530의 요구에 따라 내구성(durability) 및 손상허용설계(damage tolerance design) 의 평가가 요구되고 있다.(중략)

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.5
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• pp.127-133
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• 2002

The general requirements to achieve the structural integrity of the airframe are described in the military specification, MIL-STD-1530A. One of these requirements is the durability and damage tolerance of the airframe, which should be shown through the analysis and test based on the related specifications. This paper introduces the full scale durability test to evaluate the structural safety and durability of the basic trainer, KT-1. The test was performed according to the procedure in the military specification. The flight by flight load spectrum was developed by KT-1 fatigue load criteria and used for the durability test. The durability test had been performed for 4 service lives and was completed successfully. Therefore, it was shown that KT-1 airframe satisfied the durability requirements.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.3
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• pp.82-87
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• 2004

The general requirements to achieve the structural integrity of the airframe are described in the military specification, MIL-HDBK-1530. One of these requirements is the durability and damage tolerance of the airframe, which should be shown through the analysis and test based on the related specifications. This paper describes the full scale durability test load simulation to evaluate the structural safety and durability of the advanced trainer, T-50. The test load simulation was performed according to the procedure in the military specification and the KAF contract requirements. The durability test design technique which involve the floating test set-up, the optimal test load simulation method, and the 6-DOF test article balance method to secure the real flight conditions as many as possible. It was confirmed that this method will be available in a similar full-scale airframe structural test in future.

• 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.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.3
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• pp.30-37
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• 2023

The PSCB girder bridge is a closed cross-section in which the top and bottom flanges and the web are integrated, and the structural characteristics are generally different from the bridges in which the girder and the floor plate are separated, so a maintenance plan that reflects the characteristics of the PSCB girder bridge is required. As a result of analyzing damage types by collecting detailed safety diagnosis reports of highway PSCB girder bridges, most of the deterioration and damage occurring during use is concentrated on the top flange. In particular, cracks in the bridge direction on the underside of the top flange occurred in about 70 % of the PSCB girder bridges to be analyzed, and these cracks were judged to be caused by indirect loads such as heat of hydration and drying shrinkage rather than structural cracks caused by external loads. In order to improve durability and reduce maintenance costs of PSCB girder bridges in use, it is necessary to control restraint drying shrinkage cracks from the design stage. Therefore, in this paper, the cracks caused by drying shrinkage under restraint, which is the main cause of cracks under the flanges of the top part of the PSCB girder bridge, were directly calculated using the Gilbert Model, and the influencing factors such as the amount of reinforcing bars, diameter and spacing of reinforcing bars were analyzed. As a result of the analysis, it was found that the crack width caused by restraint drying shrinkage exceeded the allowable crack width of 0.2 mm for reinforcing bars with a reinforcing bar ratio of 0.01 or less based on the H16 reinforcing bar and a reinforcing bar with a diameter greater than H19 based on the reinforcing bar ratio of 0.01. Finally, based on the results of the crack width review, a method for controlling the crack width of the top flange of the PSCB girder bridge was proposed.