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  • Open Access

    ARTICLE

    Icing Tests in a Small Blow-Down Wind Tunnel

    G. P. Russo1, A. Esposito1, B. Esposito2, R. Renis1,1, F. Parente1

    FDMP-Fluid Dynamics & Materials Processing, Vol.6, No.3, pp. 319-336, 2010, DOI:10.3970/fdmp.2010.006.319

    Abstract A low-cost facility, able to simulate icing conditions occurring in flight, has been built via modification of a small blow-down supersonic wind tunnel. As the storage tank (30bar) is emptied through the wind tunnel, expansion of the contained air makes temperature to decrease down to -20 C and a control valve holds such temperature for about 200s. In order to increase the liquid water content (LWC) of the flow allowing ice formation on model surfaces within the test chamber, water is sprayed in the stream within the stagnation chamber by means of a controlled spray gun. This unsteady technique allows… More >

  • Open Access

    ARTICLE

    Impact of Overhead Excavation on an Existing Shield Tunnel: Field Monitoring and a Full 3D Finite Element Analysis

    F. Wang1,2, D.M. Zhang1,2,3, H.H. Zhu4, H.W. Huang1,2, J.H. Yin5

    CMC-Computers, Materials & Continua, Vol.34, No.1, pp. 63-81, 2013, DOI:10.3970/cmc.2013.034.063

    Abstract This paper studies the impact of overhead excavation on an existing tunnel through both field monitoring and a full 3D numerical model. It is found that the excavation induced longitudinal heave of the tunnel is uneven with maximum heave occurring below the excavation center. Even at the same cross section, the excavation induced heave is not uniform with the most significant heave occurring at the tunnel crown. The bending moments of the tunnel lining is decreased due to the overhead excavation. The axial forces of the tunnel lining generally decrease except at the tunnel invert. The shear forces of the… More >

  • Open Access

    ARTICLE

    Numerical Simulations on Piezoresistivity of CNT/Polymer Based Nanocomposites

    Alamusi1, Y.L. Liu1, N. Hu1,2

    CMC-Computers, Materials & Continua, Vol.20, No.2, pp. 101-118, 2010, DOI:10.3970/cmc.2010.020.101

    Abstract In this work, we propose a 3 dimensional (3D) numerical model to predict the piezoresistivity behaviors of a nanocomposite material made from an insulating polymer filled by carbon nanotubes (CNTs). This material is very hopeful for its application in highly sensitive strain sensor by measuring its piezoresistivity, i.e., the ratio of resistance change versus applied strain. In this numerical approach, a 3D resistor network model is firstly proposed to predict the electrical conductivity of the nanocomposite with a large amount of randomly dispersed CNTs under the zero strain state. By focusing on the fact that the piezoresistivity of the nanocomposite… More >

  • Open Access

    ARTICLE

    The Colossal Piezoresistive Effect in Nickel Nanostrand Polymer Composites and a Quantum Tunneling Model

    Oliver K. Johnson1, Calvin J. Gardner1, David T. Fullwood1, Brent L.Adams1, Nathan Hansen2, George Hansen2

    CMC-Computers, Materials & Continua, Vol.15, No.2, pp. 87-112, 2010, DOI:10.3970/cmc.2010.015.087

    Abstract A novel nickel nanostrand-silicone composite material at an optimized 15 vol% filler concentration demonstrates a dramatic piezoresistive effect with a negative gauge factor (ratio of percent change in resistivity to strain). The composite volume resistivity decreases in excess of three orders of magnitude at a 60% strain. The piezoresistivity does decrease slightly as a function of cycles, but not significantly as a function of time. The material's resistivity is also temperature dependent, once again with a negative dependence.
    The evidence indicates that nickel strands are physically separated by matrix material even at high volume fractions, and points to a charge… More >

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