论文部分内容阅读
本文认为,在第二临界角下,固体表面附近存在的应是滑行畸变波,而不是横波。滑行畸变波有负指数滑行畸变波和正指数滑行畸变波。两种滑行畸变波必须并存,单独一种不能存在。滑行畸变波系由第二临界角下离开固体表面稍远的、沿平行表面方向传播的横波声来转化而来,此横波声束并不受边界条件的制约。两种滑行畸变波的声速相同,其值略小于横波声速。总之,在第二临界角下,入射纵波会转化出固体中的横波声束、负指数滑行畸变波和正指数滑行畸变波。在传播中,滑行畸变波被相应的横波声束抛落在后。但此横波声束不断向固体表面扩散,在固体表面附近转化出新生的滑行畸变波。所以,实测所得的声速应该等于或非常接近横渡声速。这种分析对于井下情况也能近似适用。
This paper argues that at the second critical angle, there should be a gliding distortion rather than a shear wave in the vicinity of the solid surface. The glide wave has negative exponential gliding wave and positive exponential gliding wave. Two kinds of gliding wave must coexist, a single kind can not exist. The glide waves are transformed by the shear waves that are slightly further away from the surface of the solid at the second critical angle and propagate along the parallel surfaces. The shear waves are not constrained by the boundary conditions. The two types of glide waves have the same sound velocity, which is slightly smaller than the shear wave velocity. In summary, at the second critical angle, the incident longitudinal wave transforms the shear wave, negative exponential and positive exponential aberration waves in the solid. During propagation, the gliding wave is dropped behind by the corresponding transverse wave beam. However, the shear wave beam continuously spreads to the solid surface and transforms the nascent gliding distortion wave near the solid surface. Therefore, the measured sound speed should be equal to or very close to the speed of sound crossing. This analysis can also be applied to the downhole situation.