• 항공우주기술
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• 제7권2호
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• pp.1-10
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• 2008

일반적으로 조류충돌 안전성 입증에 대한 규정은 고정익 항공기 중 FAR Part 23급 커뮤터 및 FAR Part 25급 민간항공기 부류의 항공기에 국한되어 적용되고 있다. 이는 상대적으로 낮은 비행속력과 주로 개인용 항공기로의 활용 등의 이유로 조류 충돌에 대한 위험성이 낮게 평가되었기 때문이다. 하지만 최근의 지점 간 운송을 목적으로 하는 Air-Taxi 등의 수요 증가로 인한 소형항공기 운항시간 증가 예측과 급격한 수요의 VLJ(Very Light Jet)등은 FAR Part 23급 Normal, Utility급 항공기의 조류 충돌 안전성에 대한 규정 적용 및 안전성 향상에 대한 필요성을 증가시키고 있다. 본 연구에서는 외연적 유한요소 해석을 이용한 소형항공기 주익에 대한 조류 충돌 안전성 평가와 Crushable Foam을 적용한 안전성 향상방안을 제시하고 있다.

• Steel and Composite Structures
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• 제17권2호
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• pp.159-172
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• 2014

A finite element model with the consideration of damage initiation and evolution has been developed for the analysis of the dynamic response of a composite sandwich panel subject to low velocity impact. Typical damage modes including fiber breakage, matrix crushing and cracking, delamination and core crushing are considered in this model. Strain-based Hashin failure criteria with stiffness degradation mechanism are used in predicting the initiation and evolution of intra-laminar damage modes by self-developed VUMAT subroutine. Zero-thickness cohesive elements are adopted along the interface regions between the facesheets and the foam core to simulate the initiation and propagation of delamination. A crushable foam core model with volumetric hardening rule is used to simulate the mechanical behavior of foam core material at the plastic state. The time history curves of contact force and the core collapse area are obtained. They all show a good correlation with the experimental data.

• 대한조선학회논문집
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• 제48권1호
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• pp.42-48
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• 2011

To define ice as a solid material, mathematical and physical characteristics and their application examples are investigated for several materials' yield functions which include isotropic elastic, isotropic elastic-plastic, classical Drucker-Prager, Drucker-Prager Cap, Heinonen's elliptic, Derradji-Aouat's elliptic, and crushable foam models. Taking into account brittle failure mode of ice subject to high loading rate or extremely low temperature, isotropic elastic model can be better practicable than isotropic elastic-plastic model. If a failure criterion can be properly determined, the elastic model will provide relatively practicable impact force history from ice-hull interactions. On the other hand, it is thought that the soil models can better predict the ice spalling mechanism, since they contain both terms of shear stress-induced and hydrostatic stress-induced failures in the yield function.