Samer Guirguis

In this talk, we present the semi-analytical gradient-based optimization (GBO) technique for an efficient design of the broadband acoustic lens. This idea differs from earlier inverse designs that use topology optimization, shape optimization, and generic algorithms. We derived a formula for the gradients of the absolute pressure at the focal point with respect to positions and radii of a set of cylindrical scatterers. The derived analytic form of gradients of absolute pressure complements the modeling when combined with optimization and parallel computing. The GBO algorithm maximizes the sound amplification at focal point by evaluating pressure derivative with respect to the cylinder positions and radii, and then perturbatively optimizing the position and radius of each cylinder in the lens while considering acoustic multiple scattering between the cylinders. Computations are performed using the MultiStart Global optimization solver with fmincon while supplying the gradient of pres...

The laminated composite plates are basic structural components used in a variety of engineering structures. An important element in the dynamic analysis of composite laminate structure is the computation of their natural frequencies. The present study involves extensive experimental works to investigate the free vibration of square woven fiber Glass/Epoxy composite plates with two opposite simply supports edges and the remaining two edges are free boundary conditions. The specimens of woven glass fiber and epoxy matrix composite plates were manufactured by the hand-layup technique. Elastic parameters of the plate were also determined experimentally by tensile testing of specimens. Finite element modelling was employed to simulate the dynamic response of composite laminates plates with delamination and extract their vibration parameters. Present experiments were used to validate the results obtained from the FEM numerical analysis. In this paper, the effect of delamination on free vibration through thicknesswise direction was introduced. First natural frequency was investigated theoretically by using energy method and compared with numerical and experimental results. Good agreement was found between theoretical, numerical and experimental results. Results show that the delamination has considerable effect on the natural frequencies.

Infrared thermography is a twodimensional, non-contact technique allowing surface temperature mapping by providing colourful images easy to interpret through the use of an external energy source and an infrared detector. The attention of the present study was focused on the aid provided by active thermography for non-destructive evaluation of composite material. In present work the experimental analysis was performed by testing several specimens, which were made of E glass woven with epoxy which included the most commonly encountered kinds of damage called delamination artificially created in composite laminate specimens. From the experimental investigations, the effects of delamination area on the detection were elucidated. Also the applicability of the present thermograph method depends on a relative difference of thermal property between the delamination and its surrounding was explained.

A broadband acoustic lens is designed based on the principle of reciprocity and gradient-based optimization. Acoustic reciprocity is used to define the pressure at the focal point due to a source located in a far-field and to relate the response by a configuration of scatterers for an incident plane wave. The pressure at the focal point is maximized by rearranging the scatterers and supplying the gradients of absolute pressure at the focal point with respect to scatterer positions. Numerical examples are given for clusters of cylindrical voids and sets of elastic thin shells in water.

A gradient-based optimization (GBO) method is presented for acoustic lens design and sound localization. GBO uses a semi-analytical optimization combined with the principle of acoustic reciprocity. The idea differs from earlier inverse designs that use topology optimization tools and generic algorithms. We first derive a formula for the gradients of the pressure at the focal point with respect to positions of a set of cylindrical scatterers. The analytic form of the gradients enhances modeling capability when combined with optimization algorithms and parallel computing. The GBO algorithm maximizes the sound amplification at the focal point and enhances the sound localization by evaluating pressure derivatives with respect to the cylinder positions and then perturbatively optimizing the position of each cylinder in the lens while incorporating multiple scattering between the cylindrical scatterers. The results of the GBO of the uni- and multi-directional broadband acoustic lens desig...