Mixing time in spherical and tapered baths agitated by bottom gas injection was measured in the presence of a swirl motion of the deep-water wave type. The measured values of the mixing time were compared with empirical equations proposed for the most commonly used cylindrical baths. When the aspect ratio of the bath, H_L/D was smaller than 0.5, the mixing time in the spherical bath was the shortest, where H_L is the bath depth and D is the bath diameter. On the other hand, when the aspect ratio was greater than 0.5, the tapered bath was the most suitable for mixing.

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We investigated the shapes and dynamic behaviors of vortexes in a mechanically agitated water bath, focusing attention mainly on inclined-vortex formation by offset agitation that is effective for the mixing of a liquid and low density particles. The shapes of observed vortexes were classified into two groups, i.e., inclined vortexes and pseudo-vertical vortexes. The dynamic behaviors of the vortexes were classified into the following types: (1) stable, (2) intermittently developed, and (3) undeveloped vortexes. The relationship between the vortex type and geometrical conditions (i.e., the depth of the water, H_W, and the height of the impeller, H) was summarized as the vortex formation map (H-H_W diagram) for given bath diameter, rotation speed of the stirrer and offset distance, R_E. The condition for the formation of each vortex-shape group was expressed by the corresponding equation containing geometrical parameters such as H, H_W, and R_E.

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In the current continuous casting, biased flow of molten steel in the mold leads to entrapment of nonmetallic inclusions, and hence, severe defects of the steel products are caused. Bubble attachment to the sliding gate appears to be the main cause of the biased flow. In this water model study, patterns of bubble attachment to the sliding gate were experimentally investigated. Also, the velocity of water flow around the sliding gate was measured using particle image velocimetry (PIV). The patterns of bubble attachment were classified into four types. The water flow around the sliding gate fluctuated strongly under a specific bubble attachment pattern.

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A simple and economical fabricating process for free-form microchannels in metal bodies has been proposed. The concept for our process is based on a microscopic infiltration phenomenon that often occurs during liquid phase sintering of a mixture of different metals powder, e.g., a mixture of titanium and aluminum. In our microchanneling process, a shaped compound of aluminum powder and an organic binder is used as a sacrificial core. The powder-binder compound is formed into the same shape as the intended microchannel-network by a micro-injection process. A titanium powder compact containing the sacrificial core is sintered at a temperature above the melting point of aluminum. During sintering of the powder compact, the organic binder is removed and liquid aluminum originating from the aluminum powder flows into narrow capillaries between the titanium powder particles and reacts with the titanium particles to produce Ti-Al alloy layers lining the cavity formed at the sites initially occupied by the powder-binder compound. The composition, phase and structure of the lining layers can be changed by the addition of a third element into the powder-binder compound.

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Experimental investigation was carried out on the effects of small particles on the occurrence region, starting time, T_s,s, damping time, T_s,d, amplitude, A, and period, T_s, of a swirl motion of a bottom blown bubbling jet in a cylindrical bath. The occurrence region of the swirl motion was affected by the particles only when the aspect ratio of the bath was higher than 0.7. The measured values of T_s,s, T_s,d, A, and T_s were hardly affected by the particles as long as the steady swirl motion occurred. Solid particles were lifted up into the bath in the presence of the swirl motion, and then dispersed in the whole bath. Under a specific condition, the swirl motion ceased through an effect of the dispersed particles, and as a result, lifting of solid particles also ceased. Such a series of events were periodically repeated.

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The stress wave propagation in the solid medium is affected by the change in temperature of the medium. In this paper, we observe the patterns of the propagating stress waves in the rod of rectangular cross section at high temperatures and room temperature by the photographic method, and analyze the dynamic behavior of stress waves by means of the high speed photoelastic experimental method with the aid of a semiconductor strain gauge in order to examine the effect of temperature on the velocity of the propagating stress waves in the isotropic medium. We consider the velocity of the propagating stress waves in the high temperature and room temperature media by using the thermodynamical method. The experimental results on the velocity of propagation of stress waves are found to be in fairly good agreement with the theoretical values of velocity derived from the thermodynamical consideration.

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The effects of the kinematic viscosity of slag on the fluid flow phenomena in a molten metal bath agitated by bottom gas injection was investigated using a cold model. Water and some silicone oils of different kinematic viscosities were used as models for the molten metal and slag, and air was used as a model for the injected gas. The liquid flow velocity was measured with a two channel laser Doppler velocimeter (LDV). The turbulence components were more influenced by the kinematic viscosity than the mean velocity components. Empirical equations were derived for the spatial mean kinetic energies of the mean velocity and turbulence components.

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To evaluate the mechanical properties of molten slags, the compression test and relaxation test of molten slags have been carried out and the compression stresses of molten slags were measured as a function of temperature (1623 to 1723K), deformation rate (1 μm to 1 mm/min) and slag composition (CaO-SiO₂-Al₂O₃ system). Stress relaxation test was carried out to understand their lubrication properties at the strand during withdrawing steel slabs by the caster. It was found that the compression stress was increased with increase of Al₂O₃ content. The compression stress was also found to increase with increase of compression rate. For relaxation tests of molten CaO-SiO₂-Al₂O₃ system, the compression did not return to zero, but showed residual compression stress. The stress relaxation behavior of molten slag has been well expressed by using three-parameter solid model.

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The collision dynamics of a water droplet on a wing surface of live dragonfly were studied using a high-speed video camera system. The high-speed video camera system is composed of two video cameras, two video cassette recorders, motion grabber, two video monitors, and a personal computer. This experimental study focused mainly on the function of the dragonfly wings for the droplet collision. The dynamic response of dragonfly wing was studied for two impact velocities of water droplet. It was found that live dragonfly wings have excellent shock absorption and deformability for the rain droplet collision.

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High power spallation targets for neutron sources are developing in the world. Mercury target will be installed at the material and life facility in J-PARC, which will promote innovative science. The mercury target is subject to the pressure wave caused by the proton bombarding in mercury. The pressure wave propagation induces the cavitation in mercury that imposes localized impact damage on the target vessel. The impact erosion is a critical issue to decide the lifetime of the target. The electric-Magnetic Impact Testing Machine, MIMTM, was developed to reproduce the localized impact erosion damage and evaluate the damage formation. Additionally, acoustic vibration measurement was carried out to investigate the correlation between damage and acoustic vibration. It was confirmed that the acoustic vibration is useful to predict the damage due to the localized impact erosion.

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Mechanical properties of submicrocrystalline (grains size of about 0.4 μm) Ti-6Al-4V alloy produced by means of sequential deformation of a sample along three orthogonal directions (“abc” deformation). Enhancement of the mechanical properties of the alloy in terms of yield strength, ultimate tensile strength and fatigue strength as compared with the heat-strengthened microcrystalline alloy was revealed. Further increase in the strength of the submicrocrystalline alloy due to cold or warm rolling was shown. The causes of mechanical properties enhancing are discussed.

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