• Title/Summary/Keyword: Cross-Sectional Stiffness

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Cross-Sectional Structural Stiffness Prediction Model for Rotor Blade Based on Deep Neural Network (심층신경망 기반 회전익 블레이드의 단면 구조 강성 예측 모델)

  • Byeongju Kang;Seongwoo Cheon;Haeseong Cho;Youngjung Kee;Taeseong Kim
    • Journal of Aerospace System Engineering
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    • v.18 no.1
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    • pp.21-28
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    • 2024
  • In this paper, two prediction models based on deep neural network that could predict cross-sectional stiffness of a rotor blade were proposed. Herein, we employed structural and material information of cross-section. In the case of a prediction model that used material properties as the input of the network, it was designed to predict the cross-sectional stiffness by considering elastic modulus of each cross-sectional member. In the case of the prediction model that used structural information as a network input, it was designed to predict the cross-sectional stiffness by considering the location and thickness of cross-sectional members as network input. Both prediction models based on a deep neural network were realized using data obtained by cross-sectional analysis with KSAC2D (Konkuk section analysis code - two-dimensional).

Effect of Three-dimensional Warping on Stiffness Constants of Closed Section Composite Beams

  • Dhadwal, Manoj Kumar;Jung, Sung Nam
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.3
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    • pp.467-473
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    • 2017
  • This paper focuses on the investigation of three-dimensional (3D) warping effect on the stiffness constants of composite beams with closed section profiles. A finite element (FE) cross-sectional analysis is developed based on the Reissner's multifield variational principle. The 3D in-plane and out-of-plane warping displacements, and sectional stresses are approximated as linear functions of generalized sectional stress resultants at the global level and as FE shape functions at the local sectional level. The classical elastic couplings are taken into account which include transverse shear and Poisson deformation effects. A generalized Timoshenko level $6{\times}6$ stiffness matrix is computed for closed section composite beams with and without warping. The effect of neglecting the 3D warping on stiffness constants is shown to be significant indicating large errors as high as 93.3%.

Multifield Variational Finite Element Sectional Analysis of Composite Beams

  • Dhadwal, Manoj Kumar;Jung, Sung Nam
    • Composites Research
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    • v.30 no.6
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    • pp.343-349
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    • 2017
  • A multifield variational formulation is developed for the finite element (FE) cross-sectional analysis of composite beams. The cross-sectional warping displacements and sectional stresses are considered to be the primary variables through the application of Reissner's partially mixed principle. The warping displacements are modeled using generic FE shape functions with nonlinear distribution over the beam section. A generalized Timoshenko level stiffness matrix is derived which incorporates the effects of elastic couplings, transverse shear, and Poisson's deformations. The accuracy of the present analysis is validated for the stiffness constants and elastostatic responses of composite box beams which correlate well with the experimental data and other state-of-the-art approaches.

Static behavior of Kiewitt6 suspendome

  • Li, Kena;Huang, Dahai
    • Structural Engineering and Mechanics
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    • v.37 no.3
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    • pp.309-320
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    • 2011
  • As a new type of large-span space structure, suspendome is composited of the upper single-layer reticulated shell and the lower cable-strut system. It has better mechanical properties compared to single-layer reticulated shell, and the overall stiffness of suspendome structure increases greatly due to the prestress of cable. Consequently, it can cross a larger span reasonably, economically and grandly with high rigidity, good stability and simple construction. For a better assessment of the advantages of mechanical characteristic of suspendome quantitatively, the static behavior of Kiewitt6 suspendome was studied by using finite element method, and ADINA was the software application to implement the analysis. By studying a certain suspendome, the internal forces, deformation and support constrained forces of the structure were obtained in this paper. Furthermore, the influences of parameters including prestress, stay bar length, cross-sectional area and rise-to-span ratio were also discussed. The results show that the increase of prestress and vertical stay bar length can improve the stiffness of suspendome; Cross-sectional area has nearly no impact on the static behavior, and the rise-to-span ratio is the most sensitive parameter.

Evolutionary Shape Optimization of Flexbeam Sections of a Bearingless Helicopter Rotor

  • Dhadwal, Manoj Kumar;Jung, Sung Nam;Kim, Tae Joo
    • Composites Research
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    • v.27 no.6
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    • pp.207-212
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    • 2014
  • The shape optimization of composite flexbeam sections of a bearingless helicopter rotor is studied using a finite element (FE) sectional analysis integrated with an efficient evolutionary optimization algorithm called particle swarm assisted genetic algorithm (PSGA). The sectional optimization framework is developed by automating the processes for geometry and mesh generation, and the sectional analysis to compute the elastic and inertial properties. Several section shapes are explored, modeled using quadratic B-splines with control points as design variables, through a multiobjective design optimization aiming minimum torsional stiffness, lag bending stiffness, and sectional mass while maximizing the critical strength ratio. The constraints are imposed on the mass, stiffnesses, and critical strength ratio corresponding to multiple design load cases. The optimal results reveal a simpler and better feasible section with double-H shape compared to the triple-H shape of the baseline where reductions of 9.46%, 67.44% and 30% each are reported in torsional stiffness, lag bending stiffness, and sectional mass, respectively, with critical strength ratio greater than 1.5.

Dynamic Analysis of Switchable Hydraulic Engine Mount with an Inertia Track and a Decoupler (유체봉입 마운트의 유로 조절에 따른 진동감쇠 성능향상)

  • Ahn, Young Kong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.27 no.1
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    • pp.80-86
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    • 2017
  • This paper describes switching method of the cross-sectional area of the fluid passage way to improve the performance of a hydraulic engine mount with an inertia track and a decoupler. The mount has nonlinear dynamic characteristics depending on the vibrational frequency and amplitude. For the convenience of analysis, two linear motion equations were derived on the basis of the mechanical model according to the low-and high-frequencies. The properties of the transmissibility and dynamic stiffness derived from the equations were investigated according to switching the cross-sectional area of the inertia track and decoupler. Switching method of the cross-sectional area can be derived from the transmissibility plot. In comparison between transmissibility of passive and switchable mounts with an inertia track and a decoupler, the performance of the switchable mount is improved greatly than the passive mount. The resonant peak is remarkably reduced in the high frequency region.

Structural Dynamic Analysis of Bearingless Rotor System with Cross-shaped Composite Flexbeam (십자형 복합재 유연보 장착 무베어링 로터 시스템 구조동역학 해석)

  • Kim Do-Hyung;Lim In-Gyu;Lee Myung-Kyu;Lee In
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2004.10a
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    • pp.108-111
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    • 2004
  • Structural dynamic characteristics and aeroelastic stability of a small-scale bearingless rotor system have been investigated. A flexbeam is one of the most important component of bearingless hub system. It must have sufficient torsional flexibility as well as baseline stiffness in order to produce feathering motion. In the present paper, a cross-shaped composite flexbeam has been proposed for a guarantee of torsional flexibility and flapwise and lagwise bending stiffness. One dimensional elastic beam model was used for the construction of a structural model. Equivalent isotropic sectional stiffness was used in the blade model, and the flexbeam was regarded as anisotropic; which has ten independent stiffness quantities. CAMRAD II has been used for the analysis of structural dynamic characteristics of the bearingless rotor system. Rotational natural frequencies and aeroelastic stability at hovering have been investigated. Analysis result shows that the cross-shaped flexbeam has the rotational natural frequency tuning capacity.

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Validation Study of Composite Rotor Blade Sectional Analysis Program (Ksec2d-AE) (복합재료 블레이드 단면 해석 프로그램(Ksec2d-AE)의 신뢰성 검증)

  • Bae, Jae-Seong;Kim, Hyun-Sik;Bae, Jin-Kyu;Lim, Tae-Hyun;Hwang, Jae-Min;Jung, Sung Nam
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.4
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    • pp.277-282
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    • 2018
  • In this study, the accuracy and efficiency of a composite rotor blade cross-section analysis program, Ksec2d-AE, which is available at an educational web-based platform called EDISON-CSD, are assessed for possible use in undergraduate structural analysis projects. To this purpose, the convergence of cross-sectional constants by varying the number of finite elements in the cross-section of a wind turbine blade is investigated. The stiffness constants along with the cross-sectional engineering offsets obtained using Ksec2d-AE are validated against a 3D finite element analysis program MSC NASTRAN.

Development of Carbon Continuous-fiber Composite Frame for Automotive Sun-roof Assembly (자동차용 탄소 연속섬유 복합재 선루프 프레임의 개발에 대한 연구)

  • Kim, Jinbong;Kim, Kyoung-Deok;Kim, Sungjin;Shin, Dongwan;Kim, Dukki
    • Transactions of the Korean Society of Automotive Engineers
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    • v.25 no.3
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    • pp.350-359
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    • 2017
  • This paper presents a new holistic development approach for the carbon continuous-fiber composite frame of an automotive sunroof assembly. The original steel frame has been designed to get higher bending stiffness with its corrugated cross-sectional shape. The new approach uses the prepregs of a fast cure epoxy and PCM manufacturing processing. For higher productivity, the new frames feature a very simple plat cross sectional shape but achieve high bending stiffness through the laminate design. The sandwich structure with a PET foam core was presented. The frames were made of carbon UD laminae covered single carbon fabric on the outer surfaces. The fabrics provide torsional stiffness and also hold the carbon UD fibers floating in the low viscous epoxy resin of prepregs at the curing temperature during processing. The final product yields approximately 18 % savings in weight compared with the original.

Efficient cross-sectional profiling of built up CFS beams for improved flexural performance

  • Dar, M. Adil;Subramanian, N.;Atif, Mir;Dar, A.R.;Anbarasu, M.;Lim, James B.P.
    • Steel and Composite Structures
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    • v.34 no.3
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    • pp.333-345
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    • 2020
  • In the past, many efficient profiles have been developed for cold-formed steel (CFS) members by judicious intermediate stiffening of the cross-sections, and they have shown improved structural performance over conventional CFS sections. Most of this research work was based on numerical modelling, thus lacking any experimental evidence of the efficiency of these sections. To fulfill this requirement, experimental studies were conducted in this study, on efficient intermediately stiffened CFS sections in flexure, which will result in easy and simple fabrication. Two series of built-up sections, open sections (OS) and box sections (BS), were fabricated and tested under four-point loading with same cross-sectional area. Test strengths, modes of failure, deformed shapes, load vs. mid-span displacements and geometric imperfections were measured and reported. The design strengths were quantified using North American Standards and Indian Standards for cold-formed steel structures. This study confirmed that efficient profiling of CFS sections can improve both the strength and stiffness performance by up to 90%. Closed sections showed better strength performance whereas open sections showed better stiffness performance.