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141.
ULTRASONIC INFLUENCE OF POROSITY LEVEL ON CFRP COMPOSITE LAMINATES USING RAYLEIGH PROBE WAVES 总被引:2,自引:0,他引:2
Je-Woong Park Do-Jung Kim Kwang-Hee Im Sang-Kyu Park David K.Hsu Adam H.Kite Sun-Kyu Kim Kil-Sung Lee In-Young Yang 《Acta Mechanica Solida Sinica》2008,21(4):298-307
It was found that a pitch-catch signal was more sensitive than normal incidence backwall echo of longitudinal wave to subtle flaw conditions in the composites (damages, fiber orientation, low level porosity, ply waviness, and cracks). Both the strength and stiffness depend on the fiber orientation and porosity volume in the composites. The porosity content of a composite structure is critical to the strength and performance of the structure in general. The depth of the sampling volume where the pitch-catch signal came from was relatively shallow with the head- to-head miniature Rayleigh probes, but the depth can be increased by increasing the separation distance of the transmitting and receiving probes. Also, a method was utilized to determine the porosity content of a composite lay-up by processing micrograph images of the laminate. A free software package was utilized to process micrograph images of the test sample. The results from the image processing method were compared with existing data. Beam profile was characterized in unidirectional CFRP(carbon fiber reinforced plastics) using pitch-catch Rayleigh probes and the one-sided pitch-catch technique was utilized to produce C-scan images with the aid of the automatic scanner. 相似文献
142.
Received: 14 April 1998/Accepted: 22 April 1998 相似文献
143.
运用推广的液滴模型来确定新核素288115及其α衰变链上核的衰变位垒, 采用量子力学中处理α衰变的WKB方法, 对该链上各原子核的α衰变半寿命进行了研究.计算结果表明推广的液滴模型结合WKB方法可以很好地在超重区符合α衰变半寿命的实验值. 同时把推广的液滴模型的计算结果和采用密度相关的M3Y微观核力的结果做了详细的比较, 宏观模型(推广的液滴模型)和微观模型(密度相关的M3Y微观核力)计算的α衰变半寿命以及实验值三者之间的符合是对新核素288115及其α衰变链上核半寿命很好的检验. 相似文献
144.
145.
Son BW Cho YJ Cho JS Lee WK Kim DS Choi HD Choi JS Jung JH Im KS Choi WC 《Natural product letters》2001,15(5):299-306
Two new galactopyranosyldiacylglycerols have been isolated from the marine bacillariophycean microalga Nitzschia sp. and their structures were determined as (2S)-3-O-beta-D-galactopyranosyl-1,2-di-O-(9Z-hexadecenoyl)glycerol (1) and (2S)-3-O-beta-D-galactopyranosyl-1-O-(5Z,8Z,11Z,14Z,17Z-eicosapentaenoyl)-2-O-(9Z-hexadecenoyl)glycerol (2) by physicochemical evidence. 相似文献
146.
Se Hyuk Im 《Journal of the mechanics and physics of solids》2008,56(12):3315-3330
This paper presents a nonlinear mathematical model for evolution of wrinkle patterns of an anisotropic crystal film on a viscoelastic substrate layer. The underlying mechanism of wrinkling has been generally understood as a stress-driven instability. Previously, theoretical studies on wrinkling have assumed isotropic elastic properties for the film. Motivated by recent experimental observations of ordered wrinkle patterns in single-crystal thin films, this paper develops a theoretical model coupling anisotropic elastic deformation of a crystal film with viscoelastic deformation of a thin substrate layer. A linear perturbation analysis is performed to predict the onset of wrinkling instability and the initial evolution kinetics. An energy minimization method is adopted to analyze wrinkle patterns in the equilibrium states. For a cubic crystal film under an equi-biaxial compression, orthogonally ordered wrinkle patterns are predicted in both the initial stage and the equilibrium state. This is confirmed by numerical simulations of evolving wrinkle patterns. By varying the residual stresses in the film, numerical simulations show that a variety of wrinkle patterns (e.g., orthogonal, parallel, zigzag, and checkerboard patterns) emerge as a result of the competition between material anisotropy and stress anisotropy. 相似文献
147.
用Skyrme Hartree Fock模型系统地研究了40Ca到70Ca到Ca同位素偶偶核的基态性质及其同位旋依赖性.讨论了结合能、均方根半径、密度分布随同位旋的变化,研究了壳效应对结合能、双中子分离能S2n及和表面弥散厚度的影响.结果表明壳效应在S2n、表面弥散厚度中表现得非常明显.质子均方根半径Rrms随相对中子数I=(N-Z)/A的变化满足Rrms=3/5(1+αI+βI2)rpZ1/3.离心位垒对核表面以外的密度分布有很大影响. 相似文献
148.
Particles in classically forbidden area were studied with the Skyrme-Hartree-Fock theory for Ca isotopes from β stability line to neutron drip line. The number of neutrons in the classically forbidden area increases with mass number A, because of the increase of the number of neutrons occupied in the weakly-bound open shell. The number of protons in the classically forbidden area, in contrast, decreases with mass number A, because the orbits of protons become more tightly bound. It is shown that the number of particles in the classically forbidden area can give information on the appearance of the halo or skin. 相似文献
149.
M. Iqbal Z. Urrehman H. Im J. G. Son O. Seo H. Stiel P. V. Nickles D. Y. Noh K. A. Janulewicz 《Applied physics. B, Lasers and optics》2014,116(2):305-311
A tabletop, short-pulse laser-based hard X-ray (Kα) source equipped with an advanced X-ray optics and dedicated for high-resolution spectroscopy and time-resolved diffraction is described. Operation of the source together with a high-resolution spectrometer containing a large-aperture highly annealed pyrolytic graphite gave a resolution E/ΔE of ~1,800 for the spectral range around Kα line of Cu. The estimated total flux of the 8.05-keV photons was equal to 5.9 × 1010 ph/s in 4π sr. Performance boost of the source caused by X-ray optics relied on the significant increase in the Cu-Kα photon flux on both, the sample (4.7 × 106 ph/s) and the detector (3.4 × 103 ph/s). A spectral brightness of 1.4 × 107 ph/s/mm2/mrad2 was derived from the source parameters for the Kα line. Better performance due to high collecting power and reflectivity of the spectrometer enabled application of the cross-correlation technique with an Ni foil. An upper bound of emission duration of 323 ± 47 fs was obtained in this measurement. X-ray absorption near-edge spectroscopy on an Ni sample with an acquisition time of only 15 min confirmed the increased capability of the setup also for continuous spectrum (bremsstrahlung). 相似文献