Propagation of elastic waves in an anisotropic functionally graded hollow cylinder in vacuum

• Published in: Ultrasonics Vol. 51; no. 2; pp. 123 - 130
• Main Author: Baron, Cécile
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-02-2011; Elsevier
• Subjects: Anisotropy; Biological and medical sciences; Bone and Bones - diagnostic imaging; Bones; Cylinders; Density; Dispersions; Elastic wave propagation; Elasticity; Humans; In vitro bone characterization; Investigative techniques, diagnostic techniques (general aspects); Mathematical models; Media; Medical sciences; Models, Theoretical; Osteoarticular system. Muscles; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Plates; Radially graded tube; Stroh’s formalism; Ultrasonics; Ultrasonography; Vacuum; Waveguide; Elastic wave propagation; In vitro bone characterization; Radially graded tube; Stroh’s formalism; Waveguide; Elastic constant; Stratified material; Tube; Eigenmode; Mechanical properties; Elastic wave; Modeling; Wave dispersion; Osteoarticular system; Heterogeneous material; Vacuum; Functionnally graded material; Non invasive method; Series expansion; Mass density; Cylindrical shell; Elastodynamics; Curvature; Non destructive test; Stroh's formalism
• ISSN: 0041-624X; 1874-9968
• DOI: 10.1016/j.ultras.2010.07.001

As a non-destructive, non-invasive and non-ionizing evaluation technique for heterogeneous media, the ultrasonic method is of major interest in industrial applications but especially in biomedical fields. Among the unidirectionally heterogeneous media, the continuously varying media are a particular but widespread case in natural materials. The first studies on laterally varying media were carried out by geophysicists on the Ocean, the atmosphere or the Earth, but the teeth, the bone, the shells and the insects wings are also functionally graded media. Some of them can be modeled as planar structures but a lot of them are curved media and need to be modeled as cylinders instead of plates. The present paper investigates the influence of the tubular geometry of a waveguide on the propagation of elastic waves. In this paper, the studied structure is an anisotropic hollow cylinder with elastic properties (stiffness coefficients
c
ij
and mass density
ρ) functionally varying in the radial direction. An original method is proposed to find the eigenmodes of this waveguide without using a multilayered model for the cylinder. This method is based on the sextic Stroh’s formalism and an analytical solution, the matricant, explicitly expressed under the Peano series expansion form. This approach has already been validated for the study of an anisotropic laterally-graded plate (Baron et al., 2007; Baron and Naili, 2010)
[6,5]. The dispersion curves obtained for the radially-graded cylinder are compared to the dispersion curves of a corresponding laterally-graded plate to evaluate the influence of the curvature.
Preliminary results are presented for a tube of bone in vacuum modelling the
in vitro conditions of bone strength evaluation.