• Journal of the Korea Convergence Society
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• v.12 no.9
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• pp.161-168
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• 2021

As the demand for high speed and high precision increases in the field of machine tool, interest in stiffness and vibration of machine tool is increasing. However, it takes a lot of time to develop a detailed design of machine tool based on experience, and it is difficult to design appropriately. Recently, structural optimization using FEM are increasingly used in machine tool design. But, it is difficult to optimize in consideration of the vibration state of the structure since optimization through stress distribution of a structure is mainly used, In this paper, Static structural analysis, mode analysis, and harmonic analysis using FEM were conducted to optimize the head structure that has the most influence on machining in a 5-axis machine tool. It is proposed a topology optimization analysis method that considers both static stiffness and dynamic stiffness using objective function design.

• Advances in nano research
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• v.16 no.2
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• pp.111-125
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• 2024

Recently, a lot of research has been done on the analysis of axial vibrations of homogeneous and FG nanotubes (nanorods) with various aspects of vibrations that have been fully mentioned in history. However, there is a lack of investigation of the dynamic internal resonances of FG nanotubes (nanorods) between them. This is one of the essential or substantial characteristics of nonlinear vibration systems that have many applications in various fields of engineering (making actuators, sensors, etc.) and medicine (improving the course of diseases such as cancers, etc.). For this reason, in this study, for the first time, the dynamic internal resonances of FG nanorods in the simultaneous presence of large-amplitude size dependent behaviour, inertial and shear effects are investigated for general state in detail. Such theoretical patterns permit as to carry out various numerical experiments, which is the key point in the expansion of advanced nano-devices in different sciences. This research presents an AFG novel nano resonator model based on the axial vibration of the elastic nanorod system in terms of derivation from large-amplitude size dependent internal modals interactions. The Hamilton's Principle is applied to achieve the basic equations in movement and boundary conditions, and a harmonic deferential quadrature method, and a multiple scale solution technique are employed to determine a semi-analytical solution. The interest of the current solution is seen in its specific procedure that useful for deriving general relationships of internal resonances of FG nanorods. The numerical results predicted by the presented formulation are compared with results already published in the literature to indicate the precision and efficiency of the used theory and method. The influences of gradient index, aspect ratio of FG nanorod, mode number, nonlinear effects, and nonlocal effects variations on the mechanical behavior of FG nanorods are examined and discussed in detail. Also, the inertial and shear traces on the formations of internal resonances of FG nanorods are studied, simultaneously. The obtained valid results of this research can be useful and practical as input data of experimental works and construction of devices related to axial vibrations of FG nanorods.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.5
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• pp.879-885
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• 2013

Satellites provide a lot of information and essay roles in the areas of defense and space observations. The precise distances to the satellites are measured by emitting and retro-reflecting a laser. For such surveys, satellite laser ranging (SLR) systems have been developed in different forms and for different areas. The structural integrity of the tracking mount is essential for it to be able to track a high-speed satellite precisely, overcoming the various external and internal disturbances and operating conditions. In this study, the analysis of a tracking mount was performed for weight, wind loads, and inertia loads in order to verify its soundness. The results of the comparison between aluminum and steel were analyzed in order to select the optimal material for the fork and main housing part. In addition, the natural frequency and mode shape were predicted. Optimal material selection and structural integrity will also be verified using static analysis.

• Structural Engineering and Mechanics
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• v.52 no.3
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• pp.485-505
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• 2014

This study aimed to develop an approach to accurately predict the wind models and wind effects of large wind turbines. The wind-induced vibration characteristics of a 5 MW tower-blade coupled wind turbine system have been investigated in this paper. First, the blade-tower integration model was established, which included blades, nacelle, tower and the base of the wind turbine system. The harmonic superposition method and modified blade element momentum theory were then applied to simulate the fluctuating wind field for the rotor blades and tower. Finally, wind-induced responses and equivalent static wind loads (ESWL) of the system were studied based on the modified consistent coupling method, which took into account coupling effects of resonant modes, cross terms of resonant and background responses. Furthermore, useful suggestions were proposed to instruct the wind resistance design of large wind turbines. Based on obtained results, it is shown from the obtained results that wind-induced responses and ESWL were characterized with complicated modal responses, multi-mode coupling effects, and multiple equivalent objectives. Compared with the background component, the resonant component made more contribution to wind-induced responses and equivalent static wind loads at the middle-upper part of the tower and blades, and cross terms between background and resonant components affected the total fluctuation responses, while the background responses were similar with the resonant responses at the bottom of tower.