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심현주(Sim, Hyun-Ju),강재훈(Kang, Jae-Goon) 한국소음진동공학회 2005 한국소음진동공학회 논문집 Vol.15 No.4
A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of thick, complete (not truncated) conical shells of revolution, Unlike conventional shell theories, which are mathematically two-dimensional (2-D). the present method is based upon the 3-D dynamic equations of elasticity. Displacement components $u_{r},\;u_{z},\;and\;u_{\theta}$ in the radial, axial, and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in , and algebraic polynomials in the r and z directions. Potential (strain) and kinetic energies of the conical shells are formulated, the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four-digit exactitude is demonstrated for the first five frequencies of theconical shells. Novel numerical results are presented for thick, complete conical shells of revolution based upon the 3-D theory. Comparisons are also made between the frequencies from the present 3-D Ritz method and a 2-D thin shell theory.
방사 조건이 폴리프로필렌 모노필라멘트의 탄젠트 탄성률-변형률 곡선에 미치는 영향
임정렬,심현주,김상용,Im, Jeong-Ryeol,Sim, Hyeon-Ju,Kim, Sang-Yong 한국섬유공학회 1994 한국섬유공학회지 Vol.31 No.2
The effects of spinning conditions on the tangent modulus-strain curves have been studied using isotactic polypropylene(iPP) mononlaments. The tangent modulus-strain curve, which is derived from the first derivative of the true stress-strain curve, showed three distinct peaks. The tangent modulus of the first and the second peak in the tangent modulus-strain curve were increased as the draw ratio and the spinning speed were increased. The tensile strain of the first peak had little dependence on the process conditions, however, that of the second peak decreased above the natural draw ratio. The spinning conditions had little effect on the tangent modulus of the third peak, while the tensile strain of the third peak decreased as the draw ratio was increased. The variation of the isotactic helix content in iPP monofilament, determined from the FIIR spectra, was in agreement with that of the tangent modulus-strain curve with the tensile strain.