High-speed Video Camera System Research Articles

微量酸素軸流局部添加によるAr-MIGアーク溶接特性

GMA welding under pure Ar shielding gas atmosphere (pure Ar-MIG arc welding) is effective to obtain a high-quality welded joint. However, the pure Ar-MIG arc welding cannot be applied practically because of arc instability. In order to perform stable pure Ar-MIG welding, a new welding process has been required.We analyzed the cause of arc instability by high-speed video camera system. From video images, it was found that long column of liquid metal (CLM) formed at melting wire tip moves irregularly. Therefore, it was expected that unstable MIG arc is due to the behavior of the CLM, although the cathode spots moves irregularly in front of weld pool.Next, new welding process was developed, in which the small amount of oxygen can be added near the melting wire tip through the wire contact tip. In the developed process, the relationship between arc instability and oxygen content mixed in shielding gas was discussed. In the case of the introduction of small amount of oxygen, the length of CLM becomes effectively short and arc becomes stable, but the cathode spot moving area is not decreasing enough. Therefore, it was concluded that pure Ar-MIG arc instability depended on the CLM behavior.Finally, the oxygen content in weld metal was able to reduce to less than 100 ppm in the process, and then high ductility weld metal was successfully obtained with low transformation-temperature welding wire.

高速度ビデオ観察法およびX線透視法による溶接現象の可視化

高速度ビデオ観察法およびX線透視法による溶接現象の可視化

Micro-sizing degree as a property of ink-jet media printability

As well as supreme image quality realized by specialized paper, industrial and office printing markets demand uncoated general papers compatible with both offset printing and non-impact printing. The present work aims at clarifying the behavior of a micro-liquid droplet of water-based ink-jet inks or simply water absorbed into uncoated paper. In the experiment, laboratory handsheets were prepared by adding alkyl ketene dimmer (AKD) as a sizing agent at different levels of water repellency; none, 0.05, 0.10 and 0.20 % on dry pulp mass. The landing action and the absorption into paper of micro-droplets of water ejected from an ink-jet head were recorded by the microscopic high-speed video camera system every millisecond. The period of time between the landing and the completion of absorption was defined as “micro-sizing degree”. The micro-sizing degree was approximately 2 to 3 ms up to 0.10 % AKD addition. It is lower than that of commercial silica-coated ink-jet papers which was approximately 8 ms although silica-coated papers are known to absorb water very quickly. However, the micro-sizing degree was approximately 45 ms for the handsheets of 0.20 % AKD addition. This result implies that the water-repellency by AKD is distributed over fiber surfaces so homogeneously that micro-water droplets of diameters of as small as a few micrometers are absorbed stably at similar rates.

Escaping ion measurement with high time resolution on CHS

A scintillator-based lost ion probe can measure the temporal evolution of both the gyroradius and the pitch angle of energetic ions escaping a magnetically confined plasma. For the probe on the Compact Helical System, the time resolution of this detailed two-dimensional measurement is determined by a framing rate of the video camera that records the luminous images produced by the ions striking the scintillator plate. The framing rate of the old camera was 30Hz, thus the time resolution was about 33ms. Our interest is to understand the energetic ion transport in fast events such as a bursting energetic ion driven mode. The typical time scale of these events is less than 1ms, meaning that the old camera was too slow. By replacing it with an image-intensified high-speed video camera system, the temporal resolution was improved from 33to0.07ms. We have successfully installed the fast camera and captured some fast events caused by magnetohydrodynamics, which were unobservable using the original camera.

Mitral valve motion assessed by high-speed video camera in isolated swine heart

We have recently reported our isolated and working swine heart model that examines the valve motion precisely by a high-speed digital video camera system. Using this modality, the present study aimed (1) to delineate the motion of the mitral leaflets, chords and annulus throughout the cardiac cycle, and (2) to elucidate the influence of alterations in loading conditions on leaflet excursion. The valve motion of five isolated and working swine hearts was observed by an endoscope recording the images at 250 frames per second. Modified Krebs-Ringer solution was used as the sole perfusate. The images were obtained in hearts 30 min after reperfusion, changing the left atrial pressure as 4, 8, and 12 mmHg. The motion of the mitral valve in the vicinity of diastole was considered to be well understood by dividing the entire sequence into five stages: 'decoaptation,' 'E excursion,' 'diastasis,' 'A excursion,' and 'coaptation.' Initial separation occurred at both sides of the central tips of the leaflets. The leading edges always followed the mid-portion of the rough zone during opening and closing. The 'strut' second-order chords retained their tension throughout the cardiac cycle and played the role as rotary shafts of the other branching chords. The first-order chords lost their tension during opening, suggesting they mainly are involved in valve competence. Annular constriction occurred coincident with atrial contraction. An increase in preload made the isovolumic relaxation and contraction times shorter. The leaflets opened faster in the rapid-filling phase, whereas they required more time for opening and closing in the atrial-filling phase. The present study revealed the integrated movement of the mitral leaflets, chords and annulus, as well as the impact of altered preload.

Effect of sodium dodecyl sulphate and dodecanol mixtures on foam film drainage: Examining influence of surface rheology and intermolecular forces

Intermolecular forces and surface rheology of adsorbed surfactants can jointly influence the drainage and stability of foam films significantly, but have been separately considered in the literature. Here we use mixtures of sodium dodecyl sulphate and dodecanol to produce different surface shear viscosities and to elucidate the role of intermolecular forces and surface rheology in foam film drainage. The thickness of plane parallel foam films with very small radius versus time was obtained with an improved Scheludko cell set-up used in conjunction with a high-speed video camera system operating at a frequency of 1000 frames per second. The surface tension and surface potential were measured by pendant bubble tensiometry and micro-electrophoresis, respectively. The surface shear viscosity was determined by a deep channel surface shear viscometer. The modelling considered surface tension gradient, surface shear viscosity and diffusion, and DLVO and non-DLVO intermolecular forces. Comparison between experimental data and theoretical models for foam film drainage shows that the film drainage is influenced by the Marangoni effect due to surface tension gradient, producing foam films with immobile interfaces. Intermolecular forces, in particular, non-DLVO hydrophobic attractive forces, have the most significant effect on the film drainage.

Magnetic Swimming Mechanism in a Viscous Liquid

A new type of micro swimming mechanism is examined for the development of medical microrobots working in human blood vessels. The magnetic micro swimming mechanism without the wire for supplying the energy is driven by the alternating magnetic field. The magnetic swimming mechanism is examined in a transparent polyvinylchloride pipe filled with a viscous liquid. The test fluid used in the experiment is glycerin. The Helmholtz coil and a bipolar power supply are used to apply the alternating magnetic field in the experiment. Locomotive characteristics of the swimming mechanism in a viscous liquid are analyzed by a high-speed video camera system. The dynamic behavior of a micro swimming robot in a viscous liquid is revealed.

2303 磁性流体を吸着した微小磁石の磁場応答(S42-1 複雑流体の流動現象(1),S42 複雑流体の流動現象)

This paper describes the dynamic response of a small magnet encompassed with magnetic fluid in the external alternating magnetic fields. This study is concerned with the development of the micro magnetic fluid actuator composed of a permanent NdFeB magnet and kerosene-based magnetic fluid. The actuator is characterized by wireless operation with alternating magnetic field. The driving characteristics of small permanent magnet encompassed with magnetic fluid are examined by using a digital high speed video camera system. Experimental results show the possibility of the control of the permanent magnet motion by the external magnetic field.

1A1-C22 磁性流体を利用したマイクロアクチュエータの開発

This paper describes the development of micro magnetic fluid actuator driven by the external alternating magnetic field. The micro magnetic fluid actuator is composed of a permanent NdFeB magnet and kerosene-based magnetic fluid. The actuator is characterized by wireless operation with alternating magnetic field. The driving characteristics of micro actuator are examined by using a digital high speed video camera system. The dynamic responses of micro actuator are revealed experimentally.

2P1-A27 チビゲンゴロウに観察される特異な遊泳メカニズム

This paper describes the unusual swimming mechanism of a small beetle Guignotus japonicus. Usual diving beetles swim by flexing their hindlegs together simultaneously like oars. Diving beetles Guignotus japonicus move their legs alternately. The locomotive behavior of the small diving beetle Guignotus japonicus is analyzed by a high speed video camera system. The velocity changes of the hindleg motion are measured. The relation between the hindleg velocity and swimming velocity of the diving beetle is revealed. Experimental data is useful to a design of a micro robot.

Doppler-shift compensation in the Taiwanese leaf-nosed bat (Hipposideros terasensis) recorded with a telemetry microphone system during flight

Biosonar behavior was examined in Taiwanese leaf-nosed bats (Hipposideros terasensis; CF-FM bats) during flight. Echolocation sounds were recorded using a telemetry microphone mounted on the bat's head. Flight speed and three-dimensional trajectory of the bat were reconstructed from images taken with a dual high-speed video camera system. Bats were observed to change the intensity and emission rate of pulses depending on the distance from the landing site. Frequencies of the dominant second harmonic constant frequency component (CF2) of calls estimated from the bats' flight speed agreed strongly with observed values. Taiwanese leaf-nosed bats changed CF2 frequencies depending on flight speed, which caused the CF2 frequencies of the Doppler-shifted echoes to remain constant. Pulse frequencies were also estimated using echoes returning directly ahead of the bat and from its sides for two different flight conditions: landing and U-turn. Bats in flight may periodically alter their attended angles from the front to the side when emitting echolocation pulses.

Determination of springback gradient in the die on compacted polymer powders during high-velocity compaction

A uniaxial high-velocity compaction process for polymer powder using a cylindrical, hardened steel die and a new technique with relaxation assist was tested with various heights. The influences of the relaxation assist device on the process characteristics are discussed. Two bonded strain gauges and a high-speed video camera system were used to investigate the springback phenomenon during the compaction process. It was found that the relaxation assist improves the compaction of the polymer powder by locking the powder bed in the compacted form. It is shown that the high-velocity compaction process is an interruption process and that the delay times between the pressure waves can be reduced by increasing the height of the relaxation assist device. The delay times between the pressure waves are also strongly dependent on the strain rate. If the height of the relaxation assist device is increased, the first gross instantaneous springback, and the total elastic springback, are reduced. In addition, the density of the powder bed is increased. The relative times of the compacting stage, decompacting stage and the reorganisation of the particles can be also controlled by altering the height of the relaxation assist.

Multiple pulsed hypersonic liquid diesel fuel jetsdriven by projectile impact

Further studies on high-speed liquid diesel fuel jets injected into ambient air conditions have been carried out. Projectile impact has been used as the driving mechanism. A vertical two-stage light gas gun was used as a launcher to provide the high-speed impact. This paper describes the experimental technique and visualization methods that provided a rapid series of jet images in the one shot. A high-speed video camera (106 fps) and shadowgraph optical system were used to obtain visualization. Very interesting and unique phenomena have been discovered and confirmed in this study. These are that multiple high frequency jet pulses are generated within the duration of a single shot impact. The associated multiple jet shock waves have been clearly captured. This characteristic consistently occurs with the smaller conical angle, straight cone nozzles but not with those with a very wide cone angle or curved nozzle profile. An instantaneous jet tip velocity of 2680 m/s (Mach number of 7.86) was the maximum obtained with the 40\(^\circ\) nozzle. However, this jet tip velocity can only be sustained for a few microseconds as attenuation is very rapid.

Measurement of biosonar signals of echolocating bat during flight by a telemetry system

A telemetry microphone system (Telemike) has been developed, which can be mounted on the bat’s head, to measure acoustic characteristics of emitted pulses and returning echoes. The system allows us to monitor what the bat listens to during its flight. A high-speed video camera system has been also adopted together with the Telemike to trace positions in space of the flying bat for analyzing temporal pulse emission patterns. With those devices, how the CF-FM bats execute parallel time-sharing real-time processing during their flight can be investigated. Doppler-shift compensation, echo amplitude compensation and processing for multiple target detections were observed. Some of the evidence found by the Telemike will be introduced and discussed. [Work partly supported by the Innovative Cluster Creation Project promoted by MEXT and by a grant to RCAST at Doshisha University from MEXT.]

Magnetic Fluid Devices for Driving Micro Machines

This paper is concerned with the development of micro magnetic fluid devices for driving micro machines. Two kinds of new magnetic fluid devices are proposed. One is the magnetic fluid motor, and another one is reciprocating actuator. These micro devices are composed of a permanent NdFeB magnet and kerosene-based magnetic fluid HC-50. They are characterized by wireless operation with alternating magnetic field. The driving characteristics of micro magnetic fluid devices are examined by using a digital high speed video camera system. The rotary motion of the micro magnetic fluid motor shows the existence of rotational regions and irrotational regions in frequencies of external magnetic field. The amplitude of reciprocating actuator depends on the frequency of magnetic field. The effect of the volume of magnetic fluid adsorbed to the permanent magnet is also revealed experimentally.

Ink Dot Formation in Coating Layer of Ink-Jet Paper with Modified Calcium Carbonate

Commercial ink-jet papers are made from silica or alumina as a coating pigment, both of which give high image quality, but are expensive. The present work aims at efficient use of calcium carbonate as an alternative of silica for ink receptive coating layers. Commercial calcium carbonate was ground mechanically or dissolved partially with hydrochloric acid to reduce and equalize the aggregates size. Trial ink-jet papers were prepared and some of them were plasma-etched to give a hydrophilic property. The trial ink-jet papers were evaluated in terms of dynamic behavior of ink droplets ejected from a test ink-jet head visualized by a microscopic high-speed video camera system and of ink penetration depth determined by confocal laser scanning microscope (CLSM). Particle size reduction of calcium carbonate pigment by mechanical grinding and hydrochloric acid dissolution decreased ink dot area and dot roughness on the papers. This result suggests that particle size reduction improves image quality. Based on the criterion standard that the smaller the dot area, the better the image quality, the efficient processes were mechanical grinding, hydrochloric acid dissolution and plasma-etching in the decreasing order. It is concluded that particle size reduction decreases pore size of the coating structures and consequently ink droplets tend to penetrate deep in coatings rather than spread laterally along surfaces.

On the Wavy Crack Propagation Behavior in Internally Pressurized Brittle Tube

Fracture experiments were conducted using glass tubes by pressurizing internally with high pressure water and the paths of the crack propagations were observed. As the results, it has been clarified that regular wavy cracks often appear in glass tubes and that the shapes of the wavy cracks are approximately similar to one another. Monitoring crack propagations by a high-speed video camera system revealed that a crack snakes sinusoidally only when the crack propagation velocity is sufficiently small comparing with the elastic wave velocity of glass and that the wavy crack never appears when the crack tip velocity is large. Therefore, it can be concluded that the mechanism of the wavy crack propagation is not due to the dynamic effect resulting from the rapid crack propagation. Furthermore, by observing the fracture surface, it was found that the anti-plane shear stress plays an important role in the formation of wavy cracks.

Drafting Dynamics of Fine Denier Polyester Fibers

It is important to understand the role of fiber properties in the drafting process. Finer denier fibers may have different drafting behaviors than average denier fibers, such as drafting force, required roller settings, draft distribution, and velocity change zone. The objective of this work is to study the interaction of specific fiber fineness values and the drawing machine. Three different fine denier polyester fibers (0.8, 1.0, and 1.2) are run on a three-over-three roller drafting machine set at six different drafts with three roller settings. A high-speed video camera system observes fiber movements and measures fiber speeds in the drafting zone. In this study, fiber speed and variations in fiber speed are significantly affected by fiber fineness and drafting conditions. Fineness changes drafting behavior by introducing fiber clusters and fiber contact points. The acceleration process depends on the interaction of static and dynamic friction forces at the fiber contact points. Therefore, fiber movement in the drafting zone is not a continuous process, that is, it consists of local acceleration and slowing down of segments of fibers.

Inception and Dynamics of Traveling-Bubble-Type Cavitation in a Venturi.

The inception of cavitation is basically caused by a bubble nucleus which flows into the low pressure region in liquid flow. Therefore the phenomenon is dependent on the tensile strength or the nuclei concentration of tested water. In the present paper, to establish a measurement method of cavitation susceptibility using a venturi tube, the following points are investigated, such as the relation between the occurrence rate of cavitation bubbles and cavitation number, the measurement of positions and local pressure of bubble occurrence, and the high-speed video observation of bubble aspects from inception to collapse. As the result, the main points obtained are as follows. A traveling-bubble cavitation appears dominantly in a nozzle-type venturi with little possibility of flow separation. Cavitation aspects and bubble occurrence rate change with cavitation number and water quality. The various behaviors of traveling bubble cavitation in a venturi are observed using a high-speed video camera system.

Attachment interaction between air bubbles and particles in froth flotation

Direct quantitative measurements of the particle trajectories on the surface of an air bubble were obtained using a CCD high-speed video camera system. Rupture of the intervening water film between the hydrophobic particle and air bubble surfaces with the consequent formation of a three-phase contact was observed. Surface forces had little effects on the motion of the particles with a water film over the bubble surface until the film rupture occurred. The bubble–particle sliding attachment interaction is not satisfactorily described by the available theory. The corrections to the available attachment models were discussed.