Etkin bir tek katmanlı mikro delikli ses yutucu geliştirilmesi.

Micro-perforated sound absorbers with sub-millimeter size holes can provide high absorption coefficients. Various types of micro-perforated absorbers are now available in literature for different applications. This thesis presents results of work on the development of an effective single layer micro-perforated sound absorber from the commercial composite material Parabeam with micro diameter holes drilled on one side. Parabeam is used as a structural material made from a fabric woven out of a E-glass yarn and consists of two decklayers bonded together by vertical piles in a sandwich structure with piles (thick fibers) woven into the decklayers. The thesis includes, the analytical model developed for prediction of absorption coefficients, finite element solution using commercial software MSC.ACTRAN and experimental results obtained from impedance tube measurements. Different absorption characteristics can be achieved by variations in hole diameter and hole spacing. Based on the developed models, an optimization is performed to obtain an efficient absorber configuration. It has been anticipated that several different and interesting applications can be deduced by combining structural and sound absorption properties of this.M.S. - Master of Scienc

Dispersion and Sensitivity Analysis of Quasi-Scholte Wave Liquid Sensing by Analytical Methods

Ultrasonic-guided wave sensing relies on perturbation of wave propagation by changing physical properties of the target media. Solid waveguides, through which guided waves can be transduced between the transducer and the target media, are frequently employed for liquid sensing and several other applications. In this manuscript, liquid sensing sensitivity of dispersive quasi-Scholte waves, which are guided interface waves that travel at the solid-liquid boundary, is investigated. Dispersion analysis of quasi-Scholte waves is done and sensitivities of quasi-Scholte waves to changes in fluid density and speed of sound in a dipstick configuration are analyzed. An experimentally verified analytical model based on a global matrix approach is employed in a nondimensional manner to generate representative dispersion and sensitivity surfaces. Optimum configurations with respect to the material properties of the liquid and of the waveguide are illustrated, which would enable optimal quasi-Scholte liquid sensing

Investigation of Scholte and Stoneley waves in multi-layered systems

ICU International Congress on Ultrasonics, ICU 2015; Metz; France; 11 May 2015 through 14 May 2015Interface waves are elastic waves that can propagate at the interface between two solids (Stoneley wave) or between a solid and a liquid (Scholte wave). In this study, properties of generalized Stoneley and Scholte waves are investigated analytically in a multi-layer system with both liquid-solid and solid-solid interfaces. The interface waves are modeled using partial waves in layers with finite thicknesses to trace quasi- and non-dispersive modes. Dispersion curves of the propagating modes and corresponding particle displacement profiles are obtained using numerical solution techniques with the global matrix method. Limiting conditions of quasi-modes are evaluated analytically for thickness and material selection. Furthermore, interference of the two interface waves and plate modes are investigated for small frequency-thickness products in the multi-interface system using dispersion curves and particle displacement profiles. Preliminary sensitivity analyses are also performed for development of multi sensing physical quantities such as temperature, viscosity and density simultaneously using interface waves.The Scientific and Technological Research Council of Turkey (114C102