• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.575-580
• /
• 2004

In this work, the effect of composite couplings and mass distributions on hub loads of a hingeless rotor in forward flight is investigated. 1'he hingeless composite rotor is idealized as a laminated thin-walled box-beam. The nonclassical effects such as transverse shear and torsion warping are considered in the structural formulation. The nonlinear differential equations of motion are obtained by applying Hamilton's principle. The blade responses and hub loads are calculated using a finite element formulation both in space and time. The aerodynamic forces acting on the blade are calculated using the quasi-steady strip theory. The theory includes the effects of reversed flow and compressibility The magnitude of elastic couplings obtained by MSC/NASTRAN is compared with the classical pitch-flap($\delta$$_{3}$) coupling. It is observed that the elastic couplings and mass distributions of the blade have a substantial effect on the behavior of $N_{b/}$rev hub loads. About 40% hub loads is reduced by tailoring or redistributing the structural properties of the blade.f the blade.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.12
• /
• pp.1192-1200
• /
• 2009

This paper deals with an analytical study on the aileron reversal characteristics of anisotropic composite aircraft wings modelled as thin-walled beam and having bending-torsion structural couplings caused by Circumferentially Asymmetric Stiffness layup scheme. For a study on the aileron reversal of CAS composite wings, it is essential to consider the following effects such as warping restraint, transverse shear flexibility, bending-twist structural coupling, wing aspect ratio, ratio of span-wise and chord-wise length of aileron to wing, and sweep angle, etc. The results on the aileron reversal could have a significant role in more efficient designs of thin-walled composite wing aircraft for which this aeroelastic instability is one of the most critical ones.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.8
• /
• pp.734-740
• /
• 2004

In this work, the effect of composite couplings and mass distributions on hub loads of a hingeless rotor in forward flight is investigated. The hingeless composite rotor is idealized as a laminated thin-walled box-beam. The nonclassical effects such as transverse shear and torsion warping are considered In the structural formulation. The nonlinear differential equations of motion are obtained by applying Hamilton’s principle. The blade responses and hub loads are calculated using a finite element formulation both in space and time. The aerodynamic forces acting on the blade are calculated using the quasi-steady strip theory. The theory includes the effects of reversed flow and compressibility. The magnitude of elastic couplings obtained by MSC/NASTRAN is compared with the classical pitch-flap($\delta$$_3$) coupling. It Is observed that the elastic couplings and mass distributions of the blade have a substantial effect on the behavior of $N_{b}$ /rev hub loads. About 40％ hub loads is reduced by tailoring or redistributing the structural properties of the blade.e.

• Journal of the Society of Naval Architects of Korea
• /
• v.36 no.2
• /
• pp.105-113
• /
• 1999

This paper resents a prediction method of natural frequencies of coupled horizontal and torsional vibration of hull girder based on design sensitivity analysis in case of the changes of system parameters. The sensitivity analysis is formulated applying the direct differentiation method and transfer matrix method. In the analysis, warping, shear deformation due to torsion and the continuity condition at the connected part of open and closed hull section are considered. Using the presented method. The affection for natural frequencies by the change of system parameters, especially cargo and added mass and their centers, is numerically investigated for a real large container carrier.

• Advances in aircraft and spacecraft science
• /
• v.4 no.3
• /
• pp.219-235
• /
• 2017

The large container ships and fast patrol boats are complex marine structures. Therefore, their global mechanical behaviour has long been modeled mostly by refined beam theories. Important issues of cross section warping and bending-torsion coupling have been addressed by introducing special functions in these theories with inherent assumptions and thus compromising their robustness. The 3D solid Finite Element (FE) models, on the other hand, are accurate enough but pose high computational cost. In this work, different marine vessel structures have been analysed using the well-known Carrera Unified Formulation (CUF). According to CUF, the governing equations (and consequently the finite element arrays) are written in terms of fundamental nuclei that do not depend on the problem characteristics and the approximation order. Thus, refined models can be developed in an automatic manner. In the present work, a particular class of 1D CUF models that was initially devised for the analysis of aircraft structures has been employed for the analysis of marine structures. This class, which was called Component-Wise (CW), allows one to model complex 3D features, such as inclined hull walls, floors and girders in the form of components. Realistic ship geometries were used to demonstrate the efficacy of the CUF approach. With the same level of accuracy achieved, 1D CUF beam elements require far less number of Degrees of Freedom (DoFs) compared to a 3D solid FE solution.

• Journal of Korean Society of Steel Construction
• /
• v.30 no.1
• /
• pp.1-12
• /
• 2018

A curved member should resist bending and torsional moments simultaneously even though the primary load is usually supposed to be gravitational load. The torsional moment causes complicate stress state and also can result in early yielding of material to reduce member strength. According to analysis results, the strength of a curved member that has 45 degrees of subtended angle could decrease more than 50% compare to straight girder. Nevertheless, there have been very few of researches related with ultimate strength of curved girders. In this study, various kinds of stiffness about bending, pure torsion and warping were considered with a number of models in order to verify the main factor that affects ultimate behavior of curved girder. Lateral and rotational displacement of curved member were introduced as lateral-torsional-vertical behavior and bending-torsional moment interaction curve was derived. Finally, a strength equation for ultimate moment of horizontally curved steel I-girders subjected to equal end moments based on the interaction curves. The equation could take account of the effect of curvature, unbraced length and sectional properties.