Journal of the Computational Structural Engineering Institute of Korea (한국전산구조공학회논문집)

Computational Structural Engineering Institute of Korea (한국전산구조공학회)
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Cross-sectional Optimization of a Human-Powered Aircraft Main Spar using SQP and Geometrically Exact Beam Model

기하학적 정밀 보 이론 및 SQP 기법에 의한 인간동력항공기 Main Spar 단면 설계 최적화 연구

  • Kang, Seung-Hoon (Department of Mechanical and Aerospace Engineering, Seoul Nat'l Univ.) ;
  • Im, Byeong-Uk (Department of Mechanical and Aerospace Engineering, Seoul Nat'l Univ.) ;
  • Cho, Hae-Seong (Institute of Advanced Machines and Design, Seoul Nat'l Univ) ;
  • Shin, Sang-Joon (Department of Mechanical and Aerospace Engineering, Seoul Nat'l Univ.)
  • 강승훈 (서울대학교 기계항공공학부) ;
  • 임병욱 (서울대학교 기계항공공학부) ;
  • 조해성 (서울대학교 정밀기계설계공동연구소) ;
  • 신상준 (서울대학교 기계항공공학부)
  • Received : 2018.05.21
  • Accepted : 2018.06.21
  • Published : 2018.08.31
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Abstract

This paper presents optimization of the main spar of Human-Powered Aircraft (HPA) wing. Mass minimization was attempted, while considering large torsional deformation of the beam. Sequential Quadratic Programming (SQP) method was adopted as a relevant tool to conduct structural optimization algorithm. An inner diameter and ply thicknesses of the main spar were selected as the design variables. The objective function includes factors such as mass minimization, constant tip bending displacement, and constant tip twist of the beam. For estimation of bending and torsional deformation, the geometrically exact beam model, which is appropriate for large deflection, was adopted. Properties of the cross sectional area which the geometrically exact beam model requires were obtained by Variational Asymptotic Beam Sectional Analysis (VABS), which is a cross sectional analysis program. As a result, maintaining tip bending displacement and tip twist within 1.45%, optimal design that accomplished 7.88% of the mass reduction was acquired. By the stress and strain recovery, structural integrity of the optimal design and validity of the present optimization procedure were authenticated.

본 논문에서는 보의 대변형 및 비틀림 변형을 고려한 인간동력항공기 주익 main spar 질량 최적화 과정을 소개한다. 순차적 이차 프로그래밍 기법(sequential quadratic programming)을 최적화 기법으로 선정해 구조 최적설계에 적절한 최적화 알고리즘을 수행하였다. Main spar 내부 직경, 적층 두께 등을 설계변수로 설정하였다. 목적함수에는 질량 최소화, 굽힘 변형 변위 일정, 그리고 비틀림 변형 각도 일정 등의 요소를 포함하였다. 굽힘과 비틀림 변형 계산엔 대변형 해석에 적합한 기하학적 정밀 보 모델을 도입하였으며, 기하학적 정밀 보 모델에 필요한 단면 물성은 Variational Asymptotic Beam Sectional Analysis(VABS) 단면 해석프로그램를 통해 계산하였다. 그 결과 main spar의 굽힘 변형 및 비틀림 변형을 최대 1.45% 이내로 유지한 채로 7.88%의 질량 감소를 이루는 최적설계를 도출하였다, 이후 응력복원 및 변형률 복원을 통해 최적설계의 구조적 안정성과 최적화 과정의 타당성을 검증하였다.

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References

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