The Experts below are selected from a list of 8778 Experts worldwide ranked by ideXlab platform
F G Mitri - One of the best experts on this subject based on the ideXlab platform.
-
interaction of an acoustical 2d beam with an Elastic Cylinder with arbitrary location in a non viscous fluid
Ultrasonics, 2015Co-Authors: F G MitriAbstract:The classical Resonance Scattering Theory (RST) for plane waves in acoustics is generalized for the case of a 2D arbitrarily-shaped beam incident upon an Elastic Cylinder with arbitrary location that is immersed in a nonviscous fluid. The formulation is valid for an Elastic (or viscoElastic) Cylinder (or a cylindrical shell, a layered Cylinder/shell, or a multilayered cylindrical shell, etc.) of any size and material. Partial-wave series expansions (PWSEs) for the incident, internal and scattered fields are derived, and numerical examples illustrate the theory. The wave-fields are expressed using a generalized PWSE involving the beam-shape coefficients (BSCs) and the scattering coefficients of the Cylinder. When the beam is shifted off the center of the Cylinder, the off-axial BSCs are evaluated by performing standard numerical integration. Acoustic resonance scattering directivity diagrams are calculated by subtracting an appropriate background from the expression of the scattered pressure field. The properties related to the arbitrary scattering of a zeroth-order quasi-Gaussian cylindrical beam (chosen as an example) by an Elastic brass Cylinder centered on the axis of wave propagation of the beam, and shifted off-axially are analyzed and discussed. Moreover, the total and resonance backscattering form function moduli are numerically computed, and the results discussed with emphasis on the contribution of the surface waves circumnavigating the Cylinder circular surface to the resonance backscattering. Furthermore, the analysis is extended to derive general expressions for the axial and transverse acoustic radiation force functions for the Cylinder in any 2D beam of arbitrary shape. Examples are provided for a zeroth-order quasi Gaussian cylindrical beam with different waist. Potential applications are in underwater and physical acoustics, however, ongoing research in biomedical ultrasound, non-destructive evaluation, imaging, manufacturing, instrumentation, and acoustic holography to name a few, would benefit from the results of this analysis.
-
Pseudo-Gaussian cylindrical acoustical beam – Axial scattering and radiation force on an Elastic Cylinder
Journal of Sound and Vibration, 2014Co-Authors: F G Mitri, Z.e.a. Fellah, G.t. SilvaAbstract:a b s t r a c t Making use of the addition theorem for the cylindrical wave functions and the complex-source-point method in cylindrical coordinates, an exact solution to the Helmholtz equation is derived, which corresponds to a tightly focused (or collimated) cylindrical quasi-Gaussian beam with arbitrary waist. The solution is termed "quasi-Gaussian" to make a distinction from the standard Gaussian beam solution obtained in the paraxial approximation. The advantage of introducing this new solution is the efficient and fast computational modeling of tightly focused or quasi-collimated cylindrical wave-fronts depending on the dimensionless waist parameter kw 0 , where k is the wavenumber of the acoustical radiation. Moreover, a closed-form partial-wave series expansion is obtained for the incident field, which has the property that the axial scattering (i.e. along the direction of wave propagation) and the axial acoustic radiation force (which is a time-averaged quantity) on a Cylinder, can be calculated without any approximations in the limit of linear acoustical waves in a nonviscous fluid. Examples are found where the extinction in the radiation force function plot is found to be correlated with conditions giving reduction of the backscattering from an Elastic Cylinder. Those results are useful in beam-forming design, particle manipulation in acoustic tweezers operating with focused cylindrical beams, and the prediction of the scattering and radiation forces on a cylindrical particle or liquid bridges.
-
theoretical and experimental determination of the acoustic radiation force acting on an Elastic Cylinder in a plane progressive wave far field derivation approach
New Journal of Physics, 2006Co-Authors: F G MitriAbstract:In this study, a new analytical expression of the radiation force function—which is the radiation force per unit energy density and unit cross sectional surface—for an Elastic Cylinder immersed in water and placed in a plane progressive acoustic wave is presented. The calculation is based on the far-field derivation approach. Furthermore, two solutions for the radiation force function are compared. The first is based on the far-field derivation and the second on the near-field. It is shown that for an ideal fluid both results are commensurate with the same result. Moreover, an experiment is conducted to verify the theoretical predictions for an Elastic Cylinder as well. The experimental results confirm the theory for Elastic Cylinders but show a quite different deviation from the rigid solution. These results are the first to confirm the theory for the radiation force on an Elastic Cylinder placed in a plane progressive wave-field.
Victor A. Eremeyev - One of the best experts on this subject based on the ideXlab platform.
-
Transverse surface waves on a cylindrical surface with coating
International Journal of Engineering Science, 2019Co-Authors: Giuseppe Rosi, Salah Naïli, Victor A. EremeyevAbstract:We discuss the propagation of transverse surface waves that are so-called whispering-gallery waves along a surface of an Elastic Cylinder with coating. The coating is modelled in the framework of linearized Gurtin–Murdoch surface Elasticity. Other interpretations of the surface shear modulus are given and relations to so-called stiff interface and stiff skin model are discussed. The dispersion relations are obtained and analyzed.
Hsihung Chang - One of the best experts on this subject based on the ideXlab platform.
-
a circular Elastic Cylinder under its own weight
International Journal of Solids and Structures, 2009Co-Authors: Jiann-quo Tarn, Weider Tseng, Hsihung ChangAbstract:An exact analysis of deformation and stress field in a finite circular Elastic Cylinder under its own weight is presented, with emphasis on the end effect. The problem is formulated on the basis of the state space formalism for axisymmetric deformation of a transversely isotropic body. Upon delineating the Hamiltonian characteristics of the formulation, a rigorous solution which satisfies the end conditions is determined by using eigenfunction expansion. The results show that the end effect is significant but confined to a local region near the base where the displacement and stress distributions are remarkably different from those according to the simplified solution that gives a uniaxial stress state. It is more pronounced in the Cylinder with the bottom plane being perfectly bonded than in smooth contact with a rigid base.
A N Sinclair - One of the best experts on this subject based on the ideXlab platform.
-
correlation between helical surface waves and guided modes of an infinite immersed Elastic Cylinder
Ultrasonics, 2011Co-Authors: Farhang Honarvar, Esmaeil Enjilela, A N SinclairAbstract:Abstract Scattering of obliquely incident plane acoustic waves from immersed infinite solid Elastic Cylinders is a complex phenomenon that involves generation of various types of surface waves on the body of the Cylinder. Mitri [F.G. Mitri, Acoustic backscattering enhancement resulting from the interaction of an obliquely incident plane wave with an infinite Cylinder, Ultrasonics 50 (2010) 675–682] recently showed that for a solid aluminum Cylinder, there exist acoustic backscattering enhancements at a normalized frequency of ka ⩽ 0.1 . The incidence angle α c at which these enhancements are observed lies between the first (longitudinal) and second (shear) coupling angles of the Cylinder. He also confirmed the observations previously reported by the authors that there exist backscattering enhancements of the dipole mode at large angles of incidence where no wave penetration into the Cylinder is expected. In this paper, physical explanations are provided for the aforementioned observations by establishing a correlation between helical surface waves generated by oblique insonification of an immersed infinite solid Elastic Cylinder and the longitudinal and flexural guided modes that can propagate along the Cylinder. In particular, it is shown that the backscattering enhancement observed at ka ⩽ 0.1 is due to the excitation of the first longitudinal guided mode travelling at the bar velocity along the Cylinder. It is also demonstrated that the dipole resonance mode observed at incidence angles larger than the Rayleigh coupling angle is associated with the first flexural guided mode of the Cylinder. The correlation established between the scattering and propagation problems can be used in both numerical and experimental studies of interaction of mechanical waves with Cylinders.
Shaohua Chen - One of the best experts on this subject based on the ideXlab platform.
-
Rolling motion of an Elastic Cylinder induced by Elastic strain gradients
Journal of Applied Physics, 2014Co-Authors: Lei Chen, Shaohua ChenAbstract:Recent experiment shows that an Elastic strain gradient field can be utilized to transport spherical particles on a stretchable substrate by rolling, inspired by which a generalized plane-strain Johnson-Kendall-Roberts model is developed in this paper in order to verify possible rolling of an Elastic Cylinder adhering on an Elastic substrate subject to a strain gradient. With the help of contact mechanics, closed form solutions of interface tractions, stress intensity factors, and corresponding energy release rates in the plane-strain contact model are obtained, based on which a possible rolling motion of an Elastic Cylinder induced by strain gradients is found and the criterion for the initiation of rolling is established. The theoretical prediction is consistent well with the existing experimental observation. The result should be helpful for understanding biological transport mechanisms through muscle contractions and the design of transport systems with strain gradient.
-
non slipping adhesive contact of an Elastic Cylinder on stretched substrates
Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 2006Co-Authors: Shaohua Chen, Huajian GaoAbstract:The plane strain problem of an Elastic Cylinder in adhesive contact with a stretched substrate is studied via a generalized JKR model taking into account the transmission of both tangential and normal tractions across the contact interface. The width of the contact region is determined from the Griffith energy balance near the contact edge. In the absence of external loading, the tangential traction is found to have a negligible effect on the contact size. As an external stress is applied to stretch the substrate, the contact solution exhibits three distinct regimes characterized by two threshold strains: (i) the size of the contact region is hardly affected by the applied loading when the substrate strain is below the first threshold level; (ii) the contact size decreases quickly with stretch as the substrate strain increases to between the two threshold levels; (iii) the contact size approaches zero when the substrate strain exceeds the second threshold level. Interestingly, these results share a number of common features with the experimentally observed cell reorientation on a cyclically stretched substrate. An approximate solution is presented in an appendix to represent the numerical results in closed form.
-
generalized maugis dugdale model of an Elastic Cylinder in non slipping adhesive contact with a stretched substrate
International Journal of Materials Research, 2006Co-Authors: Shaohua Chen, Huajian GaoAbstract:We have recently developed a generalized JKR model for non-slipping adhesive contact between an Elastic Cylinder and a stretched substrate where both tangential and normal tractions are transmitted across the contact interface. Here we extend this model to a generalized Maugis-Dugdale model by adopting a Dugdale-type adhesive interaction law to eliminate the stress singularity near the edge of the contact zone. The non-slipping Maugis-Dugdale model is expected to have a broader range of validity in comparison with the non-slipping JKR model. The solution shares a number of common features with experimentally observed behaviors of cell reorientation on a cyclically stretched substrate.