Propagation Of Elastic Waves Through A Micro Gap With Consideration Of Contact

Interfaces are normal in natual materials,artificial materials and engineering structures.The common assumption in treating the reflexion and refraction of elastic waves at the interface between two solids is that the bodies adhere,and that the required tensile tractions can be transmitted. For some case,they are invaild for another kind of interface with possible separation,which exist widely in practical cases.The paper investigates the propagation of elastic waves from one solid to another when the bodies are initially separated by a small gap. When a pulse of elastic waves(for sub-critical angle incdengce) strikes the surface of one of the soilds and the amplitude of the pulse is lager enough, the solids can come into contact and separate locally. Since the zones of the separation and contact are unknown as a part of the solution,the boundary problem is indeed a nonlinear one. The displacements are expressed as Fouier series. The nonlinear boundary problem is used to set a algebraic equations. Finally solutions in different zones and the condition for the appearance of the local separation and contact on the interface are discussed.The paper discussed the propagation of elastic waves through a micro gap with consideration of smoothly contact and anysised the extent and location of the zones of the contact, the interface tractions,the dimensionless gap ,the normal ratio displacement,the energy partition for different the wide of the gap etcThe thesis solves the following problems and derives some significant results:1)The extent and location of the zones of the contact is relatived with the wide of the gap.When the wide of the gap increased,the extent of the zones of the contact decreased.2)When the wide of the gap increased,the interface tractions in the zones of the contact and the dimensionless gap in the zones of the separation decreased.the interface tractions act discontinuous slopes at the trailing edges of the zones of separation , but act with smoothly at the leading edges.3)When the wide of the gap increased,the normal ratio displacement of the refract-ed waves with basic frequency induced and the normal ratio displacement of the reflect-ed waves with basic frequency decreased then increased.When the wide of the gap got the mininum value, the normal ratio displacement of the reflected taken the biggest value and the normal ratio displacement of the refracted waves did not got the biggest value.4)The contact interface produced high-frequency waves.When the wide of the gap increased,the normal ratio displacement of the refracted/ reflected waves with second-frequency increased then decreased.The relationship of the normal ratio displacement of the secondfrequency waves with the wide of the gap provided theories basis on the examine of without damage.5)The wide of the gap have significant effects on the energy partition.When the wide of the gap increased, refracted energy coefficients induced and reflected energy coefficients increased. The wide of the gap is closed to 0,refracted energy coefficients got 35%6)The angle incidence makes small influnce with the interface tractions and the dimensionless gap.When the angle incidence increased,the interface tractions and the dimensionless gap decreased.When the angle incidence got the mininum value,the extent of the zones of the separation taken the biggest value.