Gas injection mixing is widely used in many mixing processes. For example, it has been applied to snow melting and wastewater treatment. In this research we focus on the treatment of sediments on the bottom of bays and lakes. The sediments are lifted up into a reaction vessel through an effect of a swirling bubbling jet and then treated by ozone contained in the jet. As a first step, investigation is carried out on the occurrence condition and the basic characteristics of a swirling bubbling jet generated with a top lance in a bottomless cylindrical vessel.
Phase-shifting digital holography is a valuable method to measure the displacement distribution and the strain distribution of an object surface. The complex amplitude distribution of an object surface is obtained as the complex amplitude distribution at a distance of reconstructed length. If there are optical components such as a lens on the optical path, it is difficult to measure the reconstructed length. We discovered that the standard deviation of the intensity on the reconstructed image becomes maximum value when reconstructed length is same as optical length. In this paper, the method to identify the reconstructed length using standard deviation of intensity distribution is proposed.
Shape recovery properties of a Ti-Ni alloy were experimentally studied. The Ti-Ni plate was curved to memorize a high temperature shape at 400°C,and then tensile stress was given for a low temperature shape memory at the room temperature. The three shape recovery patterns were obtained according to the tensile strains. In the PatternI, the normal shape recovery occurred at the tensile strain below 5%. In the PatternII, where the tensile strain was between 5% and 15%, the plate deforms opposite side before the normal shape recovery. In the PatternIII, there was only the opposite deformation without the normal shape recovery above 15% of the tensile strain. Behaviors of two way recovery with a heat cycle were different for the each pattern. The recovery ratio and bending force in these patterns were measured. The bending force and shape recovery ratio of the opposite deformation were smaller and larger than those of the normal shape recovery.
Frictional vibration with bouncing of the pin sliding on the rotating disk was investigated. It has been well examined on a silicon nitride ball-ended pin and flat disk pair that the sinusoidal runout of disk face in the direction of pin axis caused easily bouncing of the pin. In the present paper, it will be shown that bouncing vibration is able to occur, even though there is no disk runout, if disk rotation shaft and pin axis are not strictly parallel, where the pin does not contact with the disk face at right angle. A computer simulation on outbreak of bouncing vibration was made using a combined model of translational and rotational vibration systems for the pin-on-disk tribosystem used. In the model the pin is movable linearly in the loading direction and simultaneously capable of swaying in the frictional direction. Miscellaneous parameters concerning the occurrence of bouncing, for example, squareness between pin axis and disk face, elastic rebound of the pin from disk surface, dependence of friction coefficient on sliding velocity and static friction, were under consideration in the simulation.
On a newly designed pin-on-disk tribometer mounting a disk tilt mechanism, frictional vibration with bouncing of the silicon nitride ball-ended pin sliding on the silicon nitride flat disk was investigated. In the direction of sliding, disk tilt angle was able to set in the range of 90° ± 5° to pin axis and sinusoidal runout of the disk face during rotation was negligible. The pin motion during sliding was analyzed by a computer simulation using a coupled model of translational and rotational mass-spring-damper systems for the pin-on-disk assembly used. The effect of disk rotation speed and tilt angle of disk face on the occurrence of bouncing vibration was examined in the simulation. It was found that the pin sliding along upward slope, namely positive tilt angle, on the disk surface may bounce within certain rotation speed limits according to tilt angle and also bouncing never occur downslope with negative tilt angle below some specific higher sliding speed. Such simulation results were well recognized in the friction tests carried out on the present developed tribometer.
The flow patterns for gas-liquid two-phase flow have been experimentally investigated using "mm scale" rectangular channels. In this scale the transition of dominant forces from body forces such as the inertial force and buoyancy force to the surface force occurs. The surface force is changed in this study by coating repellent on the inner wall of the channel. The observed flow patterns are basically classified into three categories; bubbly flow, slug flow and annular flow just like those in wetted channels. The boundaries among them, however, become to depend on the wettability of the channel wall as the scale of the channel decreases.
Various methods have been employed for evaluating dynamic characteristics of viscoelastic materials. Viscoelastic Split Hopkinson Bar (SHB) Method is one of the indirect techniques. And also, there are some direct techniques, for example, the wave propagation method. However, some limitations of the shape and size of their specimens are existed. The authors devised a direct impact method for a short specimen, and analyzed experimental data by assuming perfectly free edge reflection. Compressive and tensile waves are generated alternately, propagate in the specimen, and are superposed each other. Using Polymethyl Methacrylate (PMMA) specimens, accuracy of determined viscoelastic properties was examined by comparing the data of the wave propagation method with that of the newly devised method. It was deduced that reasonable results were obtained with the new method. The three kinds of material which the particular 3-piece golf ball was constructed of were experimented on using the new method as one example of low impedance materials. The dynamic viscoelastic characteristics of the three materials for the 3-piece golf ball are clarified respectively and can be approximated as 3-element solid models.
A change in the distributions of the axial velocity component associated with transition to turbulence in a constant-acceleration pipe flow has been experimentally investigated. Air is used as the working fluid. The axial velocity component of air flow in the pipe is measured with a hot-wire anemometer. The amplification of disturbance and transition to turbulence are judged based on the velocity signal, the RMS value of velocity fluctuation, and the wavelet analysis of the velocity signal. The measurements are carried out for acceleration greater than the value indicating the boundary between the low and high acceleration regimes. The velocity distributions in the developing region of the pipe are found to be very sensitive to the acceleration and the axial position.
A nickel foil strain gage is devised for measuring the elastic surface stress of a specimen subjected to repeated loads at elevated temperatures up to 550°C. The elastic stress is measured by observing slip bands in the bonded foil resulting from repeated strains. The relation between the stress amplitude acting on the specimen and the density of slip bands is examined at various temperatures and different numbers of stress cycles. Moreover, by changing the mean crystal grain diameters of the nickel foil. It were examined on the effect to the calibration curves by using the foil with different mean crystal grain diameter at 400°C and 450°C. And an image processing system is applied for an automatic measurement of the density of slip bands. The peak stresses in grooved shafts under cyclic bending are measured by the nickel foil gage and the image processing system. It is found that the results are satisfactorily accurate.