Propagation of torsional waves in tubular bones

By considering the material inhomogeneity and anisotropy of osseous tissues, the propagation of torsional waves in tubular bones has been studied in this paper. An exact closed form solution is presented. The electric and magnetic fields induced by the travelling torsional waves in tubular bones are also derived by accounting for the piezoelectricity of osseous material. Making use of the derived analytical solution, and the experimentally determined constants for osseous tissues, numerical values of the phase velocities and attenuation coefficients are calculated for different frequencies in the ultrasonic range. Further, the effects of material damping and inhomogeneity on the attenuation and phase velocities of the waves are examined.     

Use of ultrasonic surface waves for studying the properties of the human tibia

A method of determining the ultrasonic surface-wave velocity by means of exponential concentrators is proposed for determining the properties of human tibia in vitro. The effect of the radiation frequency and the thickness of the surface layer of bone tissue on the surface-wave propagation velocity is studied. For measurement purposes the tibia is divided into 24–28 vertical levels and six to seven horizontal zones. The variation of the surface-wave velocity with the measuring point is investigated. Relations are established between the distribution of surface-wave velocities and the statistical parameters characterizing the dispersion of the results, on the one hand, and biological age and the source of the bone (right or left leg), on the other.     

The propagation of ultrasonic waves in piezoelectric semiconductors

The equations of wave propagation in piezoelectric semiconductors have been derived for a frame of reference in which the principal axes concide with the crystallographic axes. It is shown that generally the dispersion relation is given by a determinant of order six but under condition wherein the plasma modes are not excited, it could be reduced to a determinant of order five, which is equivalent to the one given by Hutson and White. The dispersion relation for hybrid waves which couple acoustic phonons with plasmons has been derived and this is shown to be given by a determinental equation of order four.     

A study of bending waves in infinite and anisotropic plates

In this paper we present a unified approach to obtain integral representation formulas for describing the propagation of bending waves in infinite plates. The general anisotropic case is included and both new and well-known formulas are obtained in special cases (e.g. the classical Boussinesq formula). The formulas we have derived have been compared with experimental data and the coincidence is very good in all cases.     

Nondestructive evaluation of fatigue-induced changes in the structure of composites by an ultrasonic method using a laser

Studies were conducted to nondestructively evaluate the damage to a glass-fiber-reinforced plastic during cyclic and static loading. The evaluation was made by an ultrasonic method employing a laser. In both the unloaded and loaded specimens, the ultrasound attenuation spectrum has a resonance peak attributable to the periodic nature of the structure of the composite. This peak is shifted to the low-frequency region during static loading, due to a decrease in the elastic modulus. The spectra obtained after cyclic loading have no resonance peaks, due to attenuation of the ultrasound over a broad range of frequencies by a large number of fatigue cracks. Additional static loading results in concentration of the cracks near the boundary between the glass fibers and the polymer matrix, which leads to the formation of a resonance peak in the high-frequency region of the spectrum.Paper to be presented at the Ninth International Conference on the Mechanics of Composite Materials (Riga, October, 1995).Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 3, pp. 405–410, May–June, 1995.     

Correlations between the velocities of ultrasonic surface waves and the characteristics of the mechanical properties of human bone tissue

The correlation between the ultrasonic surface wave velocities in the human tibia, on the one hand, and the characteristics of the mechanical properties of compact bone tissue, the ultrasonic longitudinal wave velocities, and the principal biochemical components of the bone, on the other, has been investigated. The regression equations obtained make it possible to estimate the state of the bone tissue on the basis of the data of one of the most convenient methods of nondestructive materials testing.