Free space microwave measurement for detecting corrosion under a thin paint of aluminium panel
This paper presents a free space microwave measurement methods which are non-destructive and noncontact to determine the corrosion under a thin paint on aluminium panel. For free space microwave measurements techniques, the measured parameters are reflection coefficients S11, transmission coefficients S21, dielectric constants, loss factors, and complex permittivity as a function of frequencies. This paper is focusing on metal backed method in order to detect corrosion under thin paint on Aluminium panel. The metal backed method will measure the free space reflection coefficients, S11 only. In order to obtain smaller errors of dielectric constant, it is required that the sample thickness to be close to odd multiples of quarter wavelength. The results of the complex permittivity of the samples were calculated from measured reflection coefficient S11 at frequency range of 8 GHz-12 GHz.
One-Port Methods for Complex Permittivity Measurement. Short Review
The fast-growing field of different applications for dielectric material requires of development new types of such kinds of material with a wide range of characteristics and different aggregate states. One of the most important parts of developing new material is a verification procedure of its electrodynamical characteristics, which gives us the possibility to compare measured values with calculated ones. For measurement material properties nowadays use a lot of different methods for the complex permittivity extraction in the wide frequency range, but all of these methods can be divided into two big groups – one-port and two-port methods. In this article, one-port methods for complex permittivity measurement were reviewed, such as open-ended coaxial probe (OCP), short circuit probe (SCP), coplanar probe (CP), and free space (FP) measurements. The area of implementation of the most popular one-port methods and realization features are described in the article. The positive and negative sides of each of the presented methods are considered.
APPLICATION OF THE FINITE ELEMENT METHOD TO ROTARY-WING AEROELASTICITY.
Recent research in rotary-wing aeroelasticity has indicated that all fundamental problems in this area are inherently nonlinear. The non-linearities in this problem are due to the inclusion of finite slopes, due to moderate deflections, in the structural, inertia and aerodynamic operators associated with this aeroelastic problem. In this paper the equations of motion, which are both time and space dependent, for the aeroelastic problem are first formulated in P.D.E. form. Next the equations are linearized about a suitable equilibrium position. The spatial dependence in these equations is discretized using a local Galerkin method of weighted residuals resulting in a finite element formulation of the aeroelastic problem. As an illustration the method is applied to the coupled flap-lag problem of a helicopter rotor blade in hover. Comparison of the solutions with previously published solutions establishes the convergence properties of the method. It is concluded that this formulation is a practical tool for solving rotary-wing aeroelastic stability or response problems.