Fault dip variations related to elastic layering

Summary In this paper we model the crack growth in an elastic medium constituted by two welded half-spaces with different rigidities. We implement a 2D Boundary Element Method (BEM) computing shear and normal tractions acting on the crack and the slip accommodating stress drop from an arbitrary initial configuration to a final frictional configuration. The direction of crack growth follows the criterion of maximum energy release (strain and gravitational energy) provided that it overcomes the surface fracture energy and the work dissipated by friction. The energetic criterion leads to estimates of the dip angle of seismic faults depending on the amplitude of the initial stress and it includes the classical Anderson's results as a particular case. Moreover, in presence of a sharp rigidity contrast, the direction of crack growth is strongly deflected. The model simulates non-planar, complex, fault geometries, as in the case of detachment and listric faults and it explains the increase of dip angles for both normal and reverse faults, when they enter soft sedimentary layers.

Dislocation Arrays in Sapphire using Femtosecond Laser Irradiation

We investigated the formation mechanism and thermal behaviors of defects which were induced at a microscopic area inside (1120) sapphire. We used a femtosecond laser having a pulse width, wavelength, and repetition rate of 238 fs, 780 nm, and 1 kHz, respectively. Cracks were formed at the focal point along the {1102} and the {1100} planes by laser irradiation. The preferential crack formation on these planes was attributed to the different surface fracture energy between the crystallographic planes of sapphire. The cracks transformed into the array of discrete pores by the subsequent heat treatment above 1300 °C, which was due to the diffusive crack healing process. In addition, dislocations were also introduced at the interface between closed cracks.

The Cutting Energy of Rubber Cutting by a Sharp Cutter

In order to obtain the total cutting energy and the ratios of the three parts of the total energy during cutting off the rubber, a test method was proposed and a test apparatus was constructed to perform the rubber cutting experiment. In the test, the friction force and the cutting force were obtained. Through the analysis of the test results, the friction work, the deformation energy, the surface fracture energy in cutting different thickness of the rubber were calculated. This work originally proposed a test method to acquire the friction force, the friction work between the cutter and workpiece during punching process.