Sharif Digital Repository

In this paper we first obtain the order of stress singularity for a dynamically propagating self-affine fractal crack. We then show that there is always an upper bound to roughness, i.e. a propagating fractal crack reaches a terminal roughness. We then study the phenomenon of reaching a terminal velocity. Assuming that propagation of a fractal crack is discrete, we predict its terminal velocity using an asymptotic energy balance argument. In particular, we show that the limiting crack speed is a material-dependent fraction of the corresponding Rayleigh wave speed  

Using the mathematical framework of surface elasticity theory, an analytical solution is presented for Love and Rayleigh surface wave propagations in a semi-infinite medium with face-centered cubic (fcc) single crystal structure. Previous formulations within surface elasticity have been based on the simplistic assumption of isotropy. Two different crystallographic orientations with respect to the incident wave vector are examined: (a) the free surface of the half-space is (010) plane and the surface waves propagate in [100] direction, (b) the free surface of the half-space is (110) plane and the surface waves propagate in [11¯0] direction. It is well-known that, contrary to the predictions... 

The open or in-filled trenches are often used in engineering practice to mitigate ground vibration induced by different types of vibration sources. A novel approach which is considering the effect of Rayleigh wavelength on the efficiency of open and in-filled trenches coupled with regular specific normalized dimensions was implemented in this study. While impact loading is a very common type of loading (in, e.g., machine foundations, driven pile installation), it was rarely studied in the past. The loading is selected to consist of 12 impact pulses. In this study, it was shown that Rayleigh wavelength controls the effect of trench-normalized dimensions on its performance, and therefore,...