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Numerical Calculation of Hip Squeak Over the Normal Gait Cycle
강재영 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.12
This paper present the numerical and analytical hip squeak model using the normal gait data acquired from the experiment. The axis of the ground reaction force is defined on the hip joint at the successive position of the right hip during the gait cycle. The contact pressure and its distribution on the ball are calculated by the Hertz theory at the corresponding cycle. The eigenvalue sensitivity analysis is conducted at the quasi-static state of the successive position of the right hip for both the full lubrication and the mixed lubrication. For the full lubrication case, the hip joint system becomes dynamically unstable only when the hip extends. In the mixed lubrication, the 2nd bending mode has the very high squeak propensity and its frequency drastically varies with the gait cycle.
두 번의 연속적 뇌경색에 의한 Hemimedulla 증후군
강재영 대한뇌졸중학회 2000 Journal of stroke Vol.2 No.1
Background : Two major vascular syndromes of the medulla oblongata are the medial and lateral medullary syndrome. Combination of the two syndromes may occur by obstruction of vertebral artery, but the report about hemimedullary syndrome caused by consecutive infarction with its MRI scan is rare. Case report : 1st admission; A 59-year-old hypertensive man developed abrupt weakness and tingling sensation of his right limb. He also noted dizziness and speech disturbances. On neurologic examination, he had dysarthria, nystagmus, left hypoglossal nerve palsy, and right hemiparesis without facial weakness. Carotid doppler sonography results showed findings suggestive of occlusion of the left vertebral artery. Brain MRI revealed left anteromedial medullary lesion. 2nd admission (after 1 month); The patient our hospital again because of newly developed hoarseness, tingling sensation of the left face, and recurrent right hemiparesis. Neurologic examinations revealed dysarthria, vocal cord paralysis, Honer’s syndrome, nystagmus, facial palsy and hypesthesia, absent gag reflex, hypoglossal nerve palsy, cerebellar ataxia on the left side, and hemiparesis, and sensory disturbance on the right hemibody. Repeat brain MRI revealed left hemimedullary infarction. Conclusion : Hemimedullary syndrome may be caused by two consecutive medullary infarcts.Korean Journal of Stroke 2000;2(1): 103~107
Experimental investigation of friction noise in lead screw system under mode-coupling
강재영,서강숙,김기선 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.12
This study experimentally investigated the friction noise in the lead screw system. The mechanism involved in the friction noise wasanalyzed on basis of the mode-coupling characteristics. Therefore, the frequency separation between two modes near the squeak frequencywas traced with the location of nut. It was found that the friction noise of the lead screw was generated only at the nut locationwhere the frequencies of the axial and torsion modes were met. It indicated that the friction noise in the lead screw system was caused bythe mode coupling between the torsion and axial modes.
Finite element modeling for stick-slip pattern of squeal modes in disc brake
강재영 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.10
This paper provides the finite element modeling for describing the nonlinear stick-slip response of squealing modes in a disc brake system. The analytical nonlinear contact kinematics is applied to each contact node of the finite element disc and pads. Numerical resultsshow that a portion of the contact area can undergo the stick-slip oscillation. Depending on the size of the stick-slip zone, the correspondingsqueal vibration can be either the pure harmonic or periodic oscillation. Particularly, the squeal mode arising from the pad rigid modegenerates the periodic stick-slip limit cycle in its steady-squealing response, as opposed that the disc squeal modes become the pure harmonicresponse.
Lyapunov exponent of friction-induced vibration under smooth friction curve
강재영 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.8
This paper studies the nonlinear behavior of the friction-induced vibration by using spring-mass model subject to the smooth frictionvelocity curve. The nonlinearity and instability of the friction may produce the chaotic vibration depending on the friction curve. In order to show this, the Lyapunov exponents are calculated for a variety of the slope and magnitude in the smooth friction curve. In turn, the dependency of the friction curve on the chaotic attractor is illustrated.