• International Journal of Naval Architecture and Ocean Engineering
• /
• v.3 no.1
• /
• pp.95-104
• /
• 2011

As sea state harsher in the ocean space, more large motion and wave loads occurs on ships hull by non-linear phenomena. To consider nonlinear effect on ships hull in the structural design verification, the direct calculation method with numerical approach is used rather than rule values for the reliable accuracy. In this paper, the non-linear wave loads analysis in time domain is performed by using a Rankine Panel Method together with numerical schemes. Linear calculations have been carried out based on DNV CSA-2 notation to generate the motion responses and wave loads of large ships. By short and long term analysis, the design wave amplitudes are selected for the nonlinear analysis. The maximum wave induced bending moment in hogging and sagging conditions are calculated in the nonlinear analysis. Also, the green water effect on the wave induced vertical bending moment was investigated. The results show the vertical bending moments are more influenced by green water in sagging condition than in hogging condition due to green water loading.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.573-578
• /
• 2000

A bar with periodically nonuniform material properties is selected as a one-dimensional model of a flat-panel speaker. This paper describes a theoretical approach to the bending waves propagating in the nonuniform bar. The phase speed of the wave is obtained using perturbation techniques for small amplitude, sinusoidal modulation of the flexural rigidity and mass density. It is shown that the wave speed is decreased due to the nonuniformity of the material properties by the amount proportional to the square of the modulation amplitude.

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.2650-2652
• /
• 2011

The fiber reinforced composite materials have many advantages due to their high strength-to-density ratios. Thus they have been widely used in many industrial applications. As the wave propagation are closely related to dynamic analysis of structures, it is very important to predict them. This paper presents a wave propagation in the axially loaded axial-bending-shear coupled composite laminated beams which are represented by the Timoshenko beam models based on the first-order shear deformation theory.

• Advances in nano research
• /
• v.14 no.6
• /
• pp.495-506
• /
• 2023

We study the bending wave, shear wave and longitudinal wave characteristics in the double nanobeams in this paper for the first time, in the process of research, based on the Reddy's higher-order shear deformation theory and considering shear layer stiffness, linear stiffness, inter-laminar stiffness, the pore volume fraction, temperature variation, functionally graded index influence on wave propagation, based on the nonlocal strain gradient theory and Hamilton variational principle, the wave equation of the double-nanometer beams are derived. Since there are three different motion states for the double nanobeams, which includes the cases of "in phase", "out of phase" and "one nanobeam fixed", the propagation characteristics of shear-, bending-, and longitudinal- waves in these three cases are discussed respectively, and some valuable conclusions are obtained.

• Journal of the Korean Wood Science and Technology
• /
• v.23 no.3
• /
• pp.73-82
• /
• 1995

Black locust trees(Robinia pseudo-acacia L.) are growing widely in Korea and have been used to get honey and animal feed, but they have seldom been used as manufacturing materials. This study was carried out to evaluate the possibility of using black locust as bent-wood furniture materials. Softening methods were steaming and micro-wave heating. The specimens of 15${\times}$15${\times}$350mm were all air-dried. For softening, specimens were steamed at 100$^{\circ}C$ for 7 min, or microwave heated for 35 seconds. It is known that microwave heating softens wood much faster than steaming. The bending processing conditions are showed in Table 7. The minimum solid-bending radii of black locust were 40mm for steaming and 150mm for micro-wave heating, respectively. In conclusion the steamed black locust, showed very good solid bending properties, but the bending properties of micro-wave heated black locust were not sufficient for bent-wood furniture.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.19 no.1
• /
• pp.15-22
• /
• 1982

The effects of the forebody geometry of ships on the response function of wave loads are investigated by numerical calculations based on a strip method. For the vertical wave loads both shearing forces and bending moments, the V-shaped bow gives greater responses than the U-shaped one in regular oblique waves. These results have been clarified by the vector diagram of all static and dynamic components contributing to the resultant wave bending moment. In the present evaluation the phase relation among the components plays an important role. And the effect of the forebody geometry on lateral wave loads seems to be negligible from the result of the present investigation.

• Journal of Ocean Engineering and Technology
• /
• v.10 no.4
• /
• pp.10-16
• /
• 1996

The vibration due to progressive ocean waves is analyzed for a typical footing-type offshore airport platform. The platform is modelled as a spring-supported Euler beam and buoyancy change due to wave is considered as excitation force, under the assumption that the wave propagates without distortion by the structure. The results show that the natural frequencies of this structure are distributed very closely and are little affected by boundary conditions and that the response charateristics due to ocean waves are quite different according to the wave frequency. In this study, the wave frequencies are divided into three regions; the resonance region at which the response is governed by the resonance between the natural mode at the wave frequency and the corresponding modal component of the wave excitation force, the bending governed region at which the response is governed by the bending stiffness, and the spring (buoyancy) governed region at which the response is governed by the spring constant ahd therefore is same as the incident wave form.

• Journal of Power System Engineering
• /
• v.14 no.1
• /
• pp.53-58
• /
• 2010

A three-dimensional source distribution method is presented for the prediction of motions and vertical bending moments of ships travelling with forward speed in regular waves. Comparisons between theoretical and experimental results are shown for the motion responses and vertical bending moment of the S175 container ship model by Watanabe et al. The model ship was made of synthetic resins so as to simulate bending rigidity of a full scale ship. Numerical results are compared with experimental and numerical ones obtained in the literature. The results of comparison confirmed the validity of the proposed approach.

• Journal of Ocean Engineering and Technology
• /
• v.35 no.5
• /
• pp.347-359
• /
• 2021

This study aims to evaluate the dynamic responses of the jacket-type offshore wind turbine using FAST software (Fatigue, Aerodynamics, Structures, and Turbulence). A systematic series of simulation cases of a 5 MW jacket-type offshore wind turbine, including wind-only, wave-only, wind & wave load cases are conducted. The dynamic responses of the wind turbine structure are obtained, including the structure displacement, rotor speed, thrust force, nacelle acceleration, bending moment at the tower bottom, and shear force on the jacket leg. The calculated time-domain results are transformed to frequency domain results using FFT and the environmental load with more impact on each dynamic response is identified. It is confirmed that the dynamic displacements of the wind turbine are dominant in the wave frequency under the incident wave alone condition, and the rotor thrust, nacelle acceleration, and bending moment at the bottom of the tower exhibit high responses in the natural frequency band of the wind turbine. In the wind only condition, all responses except the vertical displacement of the wind turbine are dominant at three times the rotor rotation frequency (considering the number of blades) generated by the wind. In a combined external force with wind and waves, it was observed that the horizontal displacement is dominant by the wind load. Additionally, the bending moment on the tower base is highly affected by the wind. The shear force of the jacket leg is basically influenced by the wave loads, but it can be affected by both the wind and wave loads especially under the turbulent wind and irregular wave conditions.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.30 no.2
• /
• pp.139-145
• /
• 2010

Bending fatigue of aluminium alloy was characterized by acoustic nonlinearity of narrow band laser-generated surface wave. The higher harmonic components generated intrinsically by arrayed line laser beam were analyzed theoretically and acoustic nonlinearity was measured successfully on the surface of fatigue damaged aluminium 6061 alloy. The acoustic nonlinearity increased as a function of fatigue cycles and has close relation with damage level. Consequently, the nonlinear acoustic technique of laser-generated surface wave could be potential to characterize surface damages subjected to fatigue.