What Is an Elastic Wave?

A kind of stress wave, a form of transmission of stress and strain caused by disturbance or external force in an elastic medium. Elastic forces interact with each other in the elastic medium. When a material particle leaves the equilibrium position, that is, strain occurs, the particle vibrates under the action of elastic force, and at the same time causes the strain and vibration of surrounding particles. wave".

Stress wave is the propagation form of stress and strain disturbance. Elastic wave is a kind of stress wave, that is, the stress and strain caused by disturbance or external force

By propagation direction and

A characteristic of interface waves is,

Along semi-infinite elasticity

in case

In two different

After the elastic wave reaches the interface, part of it returns to the original

The bending phenomenon that occurs when an elastic wave encounters the edge of an obstacle or a hole during its propagation is called the diffraction of the wave. The smaller the obstacles or holes,

The study of elastic wave propagation can be divided into theoretical and experimental studies.

Theoretical research is mainly from

It is the basis of theoretical research. Before the advent of electronic technology, experiments of elastic wave propagation in media were mainly used for

In 1821, C.-L.-M.-H. Navier established the general equations of equilibrium and motion of elastomers, and the study of elastic waves began. In 1829, when S.-D. Poisson studied the problem of wave propagation in elastic media, he found that there are two types of waves, longitudinal and transverse, far from the source of the wave. By 1845, the mathematical theory of elastic wave propagation had matured. GG Stokes proved that the longitudinal wave was an expansion and contraction wave, and in 1849 the transverse wave was proved to be a distortion wave. Later, scholars studied the propagation of elastic waves in three types of infinitely long elastic rods under tension, torsion and bending, and obtained accurate solutions. Rayleigh, H. Lamb and others gave the solution of the wave equation in an infinite plate. In 1904, Lamb established the theory of the wave problem caused by the disturbance of line and point sources on the surface and inside of a semi-infinite elastomer, and obtained a solution to the problem. Therefore, this problem is called the Lamb problem. In seismology, the Lamb problem is widely used, but only applies to the far field (away from the source of the disturbance). After the 1950s, research on the diffraction of elastic waves has achieved results, but it is mainly limited to spherical and cylindrical cavities in infinite elastic media. Analytical solutions of irregular holes and structures and diffraction of waves in semi-infinite media are difficult to find, mainly due to the difficulty of satisfying irregular boundary conditions. The propagation of elastic waves in viscoelastic media is an important subject that can be used to explain many geophysical, acoustic, and engineering mechanical phenomena. The rapid development of composite mechanics has promoted the study of wave propagation theory in composites. Research on wave propagation theory in porous media has begun, and it has important practical significance for geophysics, materials engineering, petroleum exploration, and so on.

At the same time as the development of precise theory, the theory of approximate solutions has also developed. The finite difference method was first used to solve the problem of elastic wave propagation in short bars, and then it was extended to the wave propagation problem in some complex structures. The finite element method is gradually used to study the problem of elastic waves. It is used to analyze the propagation of elastic waves in thin rods, and then used to analyze the propagation of waves in various structures (columns, plates, shells), layered media, and orthogonality. Propagation of waves in heterosexual media. Preliminary studies have also been made on the study of nonlinear elastic wave propagation.