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주기적 충격하중이 작용하는 회전원판의 횡진동에 관한 실험 분석
신응수(Eung-Soo Shin),윤상열(Sang-Yul Yoon) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
The purpose of this study is to investigate experimentally the lateral stability of a rotating disk under periodic impact loadings. A test rig has been developed including a disk with multiple loading spots, a driving motor and a pendulum-type impact tip. The lateral stability of the rotating disk was experimentally analyzed based on measured transverse vibration amplitudes with the disk changing its speed. Results show that vibration responses are affected by the frequency of the impact loadings as well as the rotational speed. Specifically, vibration amplitudes increase significantly at several ranges of the disk speed below the critical region, which is closely related to sub-harmonic instability due to parametric excitation. By comparing the experimental results with analytic estimation based on the assumption of the speed fluctuations, it is found that the periodic impact greatly affects lateral vibration behaviors in unstable regions, but it has almost no effects in stable regions.
신응수 ( Eung Soo Shin ),김태광 ( Tae Kwang Kim ) 충북대학교 산업과학기술연구소 2010 산업과학기술연구 논문집 Vol.24 No.1
This paper presents the dynamic stability of a supercritical shaft supported by a cantilever. A primary objective is to investigate the effects of cantilever parameters on the whirling stability. An analytical model is developed based on finite element methods that consists of the rotating shaft with a disk, two support bearings and the support beam. Then, the state matrix is derived to identify the whirling stability. An eigenvalue analysis is first employed to estimate the stability boundaries based on the real parts of eigenvalues. Results show that the whirling instability is closely related to the bending stiffness of the cantilevered support beam as well as the shaft/bearing stiffnesses. It was found that the stable and unstable regions appear alternately in terms of the anisotropy of the support beam, the driveshaft``s rotating speed, a stiffness ratio of the support beam to the shaft/bearings.
신응수(Eung-Soo Shin),유문수(Moon-Soo Yoo) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
This work intends to investigate the propulsion characteristics of a manual wheelchair with an automatic transmission. A primary feature of the automatic transmission is its shift mechanism based on the distance traveled from rest. A planetary gear train with rachets/pawls and bushes is employed to generate two-stage shift automatically. Motion analysis has been performed for measuring kinematic properties of the arm and then inverse dynamics has been done for estimating joint forces/torques. Results show that the two-stage transmission can greatly lower the joint loadings by the speed reduction, which eventually contribute to prevent joint injuries of wheelchair users.