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Bandgap Materials effective medium model and modal association between band

Author: WangDaPeng
Tutor: WangYueSheng
School: Beijing Jiaotong University
Course: Solid Mechanics
Keywords: Bandgap Materials Elastic wave Nonlocal elasticity theory Equivalent medium Dispersion relation Bandgap
CLC: TB303
Type: Master's thesis
Year: 2010
Downloads: 25
Quote: 0
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Abstract


Vocal gap materials with unique properties and potential applications in recent years has become physics , acoustics, mechanics , and other related disciplines active area of ??research , and many scholars have characterized its bandgap done a lot of research, this paper establish the equivalent vocal gap material nonlocal elastic medium model to study the various modal body rippled surface wave dispersion curves between . With tetragonal lattice and triangular lattice system , for example, focused on the waves along the two main symmetry directions ( ie Brillouin zone Γ-X and Γ-M direction ) the spread of the use of the dispersion relation is equivalent to obtain the equivalent nonlocal elastic modulus ( ie classic local elastic modulus and the influence function of the product ) , by assuming the form of a unified influence function to calculate the modal wave dispersion curves , and the results with the results of the plane wave expansion method compared verification effect the validity of non- local model . About the two lattices body waves findings showed that: along Γ-X direction , three kinds of influence function in the first BZ zone difference is small , can be approximated as the same form , and thus obtain three kinds of modal body wave dispersion curves approximate relationship between ; influence function in the second BZ region vary greatly , P wave and SV and SH wave dispersion curves approximate relationship between compliance is not good, but the SH and SV wave dispersion curve An approximate relationship between still in good . Along Γ-M direction , three kinds of influence function in the first BZ region has a large gap , should not affect the function of each is taken as the same kind of form , and therefore could not get the modal wave dispersion curve relationship. Tetragonal lattice structure of the surface wave on the findings showed that: along Γ-X direction in the first BZ area, will affect the form of function approximation is taken as the same wave dispersion curves obtained with the plane wave expansion method results are very close , this actually gives the body waves and surface wave dispersion curves between ; difference between the results in the second BZ area slightly larger degree of approximation is not high. In short , the equivalent nonlocal elastic model is a promising vocal gap material can be approximated new wave acts continuum model , but when the waves propagate in any direction equivalent nonlocal elastic modulus ( or influence function ) to determine yet difficulties , pending further study.

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CLC: > Industrial Technology > General industrial technology > Materials science and engineering > General issues of engineering materials > Material structure and physical properties
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