Download PDF - Durham e-Theses

!Wave Types in Solids
Particle Vibrations
!Longitudinal
Parallel to wave direction
Transverse(Shear)
Perpendicular to wave direction
!surface - Rayleigh
Elliptical orbit- symmetrical mode
<~
Table 3.1(a). Wave types in solids and their mode of vibration.
Among the properties of waves propagating m isotropic solid materials are
wavelength, frequency, and velocity. The wavelength is directly proportional to the
velocity of the wave and inversely proportional to the frequency of the wave. This
relationship is shown by the following equation.
wave lengt
velocity(v)
= ___
frequency(/)
The quoted parameters of structural steel are as follows [5].
Young's Modulus: 200 GPa
Poisson's ratio: 0.26
Density: 7850 kg/m3
Longitudinal wave speed: 5583.3 m/s
Transverse wave speed: 3179.7 m/s
Rayleigh wave speed: 2928.6 m/s
The particle motion in Rayleigh wave speed goes from counter-clockwise to
clockwise at a depth of 0.1902 times the wavelength.
3.2 The Simple Harmonic Oscillator
In order for mechanical oscillation to occur, a system must posses two
quantities: elasticity and inertia. When the system is displaced from its equilibrium
function, the elasticity provides a restoring force such that the system tries to return to
equilibrium. The inertia property causes the system to overshoot equilibrium. This
constant play between the elastic and inertia properties is what allows oscillatory
15