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Fluid–rigid body interaction is a significant topic in research on particle methods. This study developed a fluid–rigid body coupling method based on a physically consistent particle method, i.e., the moving particle hydrodynamics (MPH) method, incorporating the passively moving solid (PMS) model. When the discrete particle system satisfies the fundamental laws of physics, i.e., mass conservation, linear and angular momentum conservation, and the second law of thermodynamics, the method is asserted physically consistent, and this feature is important for robust dynamic calculations. The PMS model is a pioneering approach that is practical for particle methods in which fluid and rigid-body particles are initially calculated as a fluid. Then, only rigid-body particles are modified to restore the initial shape by applying rigid-body constraints. Thus, combining the MPH method and the PMS model realizes a fluid–rigid body coupling method that satisfies fundamental physical laws. The proposed method was first verified via the fundamental rigid body and fluid–rigid body coupling problems: the Dzhanibekov effect on a T-shaped rigid body, a floating rectangular solid, a floating cylinder, and water entry of a two-dimensional cylinder. Second, the proposed method was validated via calculating a cylinder rolling on a liquid film as a fluid–rigid body coupling problem with rotation. By using a potential-based surface tension model, the computed results showed reasonable agreement with the experimental data obtained in this study. Overall, it was confirmed that the proposed method is a promising fluid–rigid body coupling approach, in which the surface tension and wettability can be considered as well. [ABSTRACT FROM AUTHOR]

The payload fairing in Japan is fixed by a lot of notched bolts. These notched bolts were fractured by axial impact tensile using the explosive devices to separate the fairing. In this case, the stress waves and the oscillations propagate, which may seriously damage the satellites. In this study, the impact deformation and the fracture behavior of notched titanium alloy bolt was investigated using a split Hopkinson pressure bar method. The notched bolt specimen was made of commercial Ti-6Al-4V alloy. The maximum load value was increased with increasing the displacement rate. It can be said that the strain rate dependence of strength for Ti-6Al-4V alloy appeared. From the observation of fracture surface using a scanning electron microscope, compared with the quasi-static test, it was clear that the irregularities of the fractured surface at the impact tensile test became rough. Therefore, it was found that the brittle fracture was mainly observed due to the increase in displacement rate, which may mean that the mode of fracture changes from the transgranular to the intergranular. It was surmised that this change of fracture mode was caused by the high strain rate due to stress concentration of the notched part.

A method of estimating the thickness distribution on a surface with inhomogeneous buried layers is presented. It revealed that the lubricant distributes nonuniformly on discrete track media (DTM). First, the estimation method was theoretically developed. To balance the disjoining pressures of the lubricants in the track and off-track regions, the lubricant takes different film thicknesses in the two regions because the regions consist of different materials and have different intermolecular interactions. Formulating the balance of the disjoining pressures by using the theory for intermolecular force, we obtained the thicknesses in the two regions. Next, the validity of the theoretical estimation was experimentally verified. When a nonpolar lubricant was applied to a nanometer-thick oxide layer on a silicon surface, which was locally fabricated by probe oxidation, AFM images showed that the lubricant height in the oxide region decreased and the thickness distribution agreed well with that predicted by theory. Using the developed theory, we estimated the lubricant thicknesses on DTM. Even if lubricant is uniformly applied onto the disk, it moves from the off-track to track regions due to the pressure balance. Thus, the theory predicts that the lubricant is thicker in the track regions than the off-track region at equilibrium. Index Terms--Discrete track media, disjoining pressure, head-disk interface, lubricant, magnetic recording.

The dual-axis micromechanical probe, which unites a double cantilever and torsion beams, minimizes the mechanical cross-talk between the lateral and vertical force detections, is described. The mechanical design of the probe, the exhaustive information of the fabrication technique, performance of the friction force microscopes (FFMs) and calibration of the friction force are presented.