Biomedical Engineering Reference
In-Depth Information
A potentially interesting concept suggested in the present chapter would use
superelastic shape memory alloy inclusions for optimum energy dissipation in an
FGM composite structure. Superelastic shape memory alloys have an exceptionally
high damping potential due to their large hysteresis loop area that can be employed
to enhance dynamic response of composites (e.g., [
57
]).
2.4.4 Waves in FGM
Studies on waves in FGM and on the scattering of waves in FGM structures have
gained noticeable popularity in recent years. For example, the effect of grading on
the stress and displacement fields generated by Love waves in an FGM layered
structure has been recently investigated [
58
]. The scattering of waves by hollow
FGM ZrO
2
-Al cylinders submerged in and filled with a nonviscous fluid was
analyzed by acoustic resonance scattering theory [
59
]. A study concerned with
the propagation of guided acoustic waves in FGM plates was undertaken in [
60
].
Propagation of waves in piezoelectric media represents a fascinating theoretical
and engineering problem. For example, the problem of wave propagation in piezo-
electric FGM structures in contact with viscous fluid was analyzed in [
61
]. A three-
dimensional piezoelastic formulation was employed to study wave propagation in
hollow cylinders in [
62
]. Wave propagation was also considered for transversely
isotropic elastic piezoelectric half-sphere with grading in the depth direction [
63
].
The propagation of antiplane and shear-horizontal planes along the interface
between two half-space piezoelectric FGM with properties varying in the direction
perpendicular to the interface was analyzed in [
64
].
Shear wave scattering from a crack in a piezoelectric layer bonded to an FGM
half-space was studied yielding normalized dynamic stress intensity factors as well
as normalized electric displacement intensity factors [
65
]. The scattering of electro-
elastic waves and the dynamic stress problem in the vicinity of a cavity in an FGM
layer bonded to a homogeneous piezoelectric material was considered by Fang [
66
].
A further degree of complexity is encountered in the problems involving
structures composed of piezoelectric and magnetostrictive materials (e.g., such
structures are being considered in energy harvesting applications). For example,
the propagation of waves in plates composed of graded piezoelectric (BaTiO
3
) and
magnetostrictive (CoFe
2
O
4
) layers was investigated in [
67
].
2.4.5 Optimization of FGM
An optimization problem in FGM hollow cylinders and spheres with a radial
volume fraction variation was considered in [
68
] aiming either at a constant hoop
or circumferential stress or a constant in-plane shear stress (in particular, constant
hoop stresses imply an elimination of stress concentration). In the same paper, the
radial distribution of constituent volume fractions necessary for a constant
through-the-thickness linear combination of the radial and hoop stresses was
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