The linear instability of Faraday waves in Hele-Shaw cells is investigated with consideration of the viscosity of fluids after gap-averaging the governing equations due to the damping from two lateral walls and the dynamic behavior of contact angle. A new hydrodynamic model is thus derived and solved semi-analytically. The contribution of viscosity to critical acceleration amplitude is slight compared to other factors associated with dissipation, and the potential flow theory is sufficient to describe onset based on the present study, but the rotational component of velocity can change the timing of onset largely, which paradoxically comes from the viscosity. The model degenerates into a novel damped Mathieu equation if the viscosity is dropped with two damping terms referring to the gap-averaged damping and dissipation from dynamic contact angle, respectively. The former increases when the gap size decreases, and the latter grows as frequency rises. When it comes to the dispersion relation of Faraday waves, an unusual detuning emerges due to the imaginary part of the gap-averaged damping.
The modern mechanical excavation machines have enough power for cutting hard rock. The bottle neck which limits the use of machines for hard rock excavation is cutting tool. To cut hard and abrasive rock, CSIRO has been developing Super Material Abrasive Resistant Tools (SMART*CUT). SMART*CUT technology replaces the tungsten carbide (WC) tip of conventional pick with thermally stable diamond composite (TSDC) and attaches the TSDC tip to steel tool body with CSIRO worldwide patented bonding technology. This paper compares its performance with conventional WC tipped tools by a series of hard rock cutting tests. The cutting and normal forces acting on the tools were measured during these tests. The tests shown that the cutting performance of SMART*CUT pick was significantly better than that of WC pick. The testing results indicate that TSDC can be applied as an effective cutting tool material for cutting hard and abrasive rocks.
The purpose of this study is to develop adhesive materials for joining different kinds of materials such as FRP and metals, and to decompose the bonding structures conveniently. As the first step, we proposed the adhesive with epoxy and ceramics particles (SiC) for a GFRP joint, and tried to decompose it by microwave irradiation. A tensile shear test of GFRP joints with the proposed adhesive was carried out with/without microwave irradiation, and effects of the volume fraction of SiC particles on the adhesive strength were investigated. As the results, it was obvious that the optimum amount of volume fraction of SiC existed to satisfy the high strength before irradiation and low strength after irradiation. Furthermore, the strength could be decreased by one irradiation and the repeat of irradiation was not necessary, and the fracture surfaces were different caused by the volume fraction of SiC particles and the effect of microwave irradiation.
Comparison of damage development of textile composites made by combination of two resin (Polyamide and Epoxy) and two kinds of fiber bundles (conventional tows and spread tows) is carried out. The quasi-static tensile tests were carried out with using DIC (digital image correlation) system to estimate the full field strain and AE (acoustic emission) sensors for measurement of the acoustic emission features. The CFRTP specimens were also investigated with optical microscope to clarify the difference of damage. Fig.1 shows characteristic damage of each CFRTP. The fiber debonding and delamination were shown in CF(with spread tows)/PA composites and the damage in weft yarn covered a wide range of test specimens. It is suggested that these features of damage were influenced with effect of fiber opening. This may also be explained by AE events. In weft yarn of CF(with conventional tows)/PA composites, we observed not only transverse crack but also clack which propagated parallel to loading direction. This type of crack was not found in other thermoplastic carbon composites such as CF/PPS described in the literature. From these results, we conclude that the damage development of textile composites is sensitive to the form of fiber bundles and the properties of the matrix.
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