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Whole-body vibration analysis for assessment of railway vehicle ride quality
강주석,최연선,최강윤 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.3
In this paper, a whole-body vibration analysis using a three-dimensional human biodynamic model is presented, and the dynamic behavior of the body exposed to vibration by a railway vehicle is investigated with respect to ride quality. Since a subject in a railway vehicle is exposed to multi-axial excitation conditions, the acceleration of the body is calculated by summing the accelerations in three directions. The equations for the acceleration response of the body are formulated as complex transfer functions multiplied by input accelerations from the three axes in the form of a frequency response function. Body behavior when exposed to random acceleration inputs measured at the floor of the railway vehicle is investigated across a frequency domain. Root Mean Square (RMS) values of the acceleration magnitudes in the body regions are calculated from the power spectral density (PSD) values of the acceleration responses. The absolute magnitude of the accelerations of the body is compared with the ride index, which is calculated using the input accelerations and standard methods. It is shown that the absolute magnitudes in the body regions are proportional to the standard ride index and that the ride index accurately reflects vibration damage to the body. A proposed seat design using the vibration magnitudes calculated with the human biodynamic model also is presented.
Optimization of helix angle for helical gear system
강주석,최연선 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.12
A method is presented to optimize the helix angle of a helical gear from the viewpoint of the transmission error, which is the deflection of the teeth due to the transmitted load. The deflection of the gear teeth is calculated by using the bending and shear influence function, which is formulated from the common formula for deflection obtained from FEM, and the contact influence function based on Hertzian contact theory. Tooth contact analysis is performed to calculate the contact lines of the helical gear, where the deflection of the tooth is measured. A numerical example is presented to explain a method to optimize the helix angle of a helical gear system. The relation between the contact ratio and transmission error is investigated through calculations of the variation in the transmission error with the helix angle.