Nobuhiko Nishiwaki

Observation of Arc Column Movement during Monopulse Discharge in EDM

This paper describes the results of the detection and observation of arc column movement during monopulse discharge and the movement of the are column subjected to a transverse magnetic field in the EDM process. It is found that not only the cathode spot but also the anode spot moves at a high speed over the electrode surfaces during a monopulse, and that the moving patterns of the anode and cathode spots are the same. Besides the area over which patterns the are column moves becomes broader with the progress of the discharge, which coincides well with the observation of the resulting craters.

Improvement of Dynamic Rigidity of Tool Holder by Applying High-Damping Material

Recently various types of high-damping material have been developed. The objective of this study is to investigate theoretically and experimentally how to apply a ferromagnetic type of high-damping material to tool holder aiming at its dramatic improvement of dynamic rigidity in a fashion of quantitative and programmable introduction of damping element, which has not been realized hitherto. It has been revealed analytically that the highest dynamic rigidity of tool holder can be attained by combining the high-damping material and a statically high-stiff material such as sintered carbide approximately half and half in length. Finally, the analytical results have been confirmed through frequency response test and actual cutting test.

An application of a laser technique to the velocity measurement of the liquid-fuel film within intake pipe of internal combustion engines

A new experimental technique is developed by combining a flash photolysis method with a laser-photodiode system to measure the velocity of the flow of thin liquid films. The technique is applied to the measurement of the velocity of the liquid-fuel film within the intake pipe of an internal combustion engine operated under firing condition. The results show that the velocity of the fuel film is of the order of 1/100 of the mean air velocity inside the intake pipe.

Forces acting to remove spatter by wire brushing and its limits. Study of finishing of welding base metal surfaces (Report 2)

Spatter scattered over welding base metal surfaces by molten metal during the welding process seriously impairs the quality of welding products when deposited at the bead periphery. Manufacturers are therefore routinely constrained to remove such spatter. Particularly for welding products attaching importance to safety or impeccable appearance through the immediacy of eye contact, it is imperative to ensure complete removal of spatter. The spatter generated during welding, however, has different adhesion ranges from the bead depending on welding conditions, and the adhesive forces of individual spatters also considerably differ. Finishing of welding base metal surfaces is generally performed by wire brushing with air or electrically operated tools. This is due to the fact that, through the wire brush being an elastic tool, its action during wire brushing can be accommodated to complex joint shapes, and brushing work can be performed without any undue harm to welding base metal surfaces. During wire brushing of welding base metal surfaces, finishing methods and processing conditions often rely on experience, and no fundamental data whatever are currently available to support automation or the establishment of processing conditions ensuring efficient removal of spatter. To establish optimum processing conditions during wire brushing, this study clarifies the relationship between finishing surface shapes and processing conditions during wire brushing of welding base metal surfaces with adhered spatters. The previous paper in this series describes an investigation of the relationship between the brushing forces acting on steel plates and the brushing marks left on the surface when the brush holding angle and pushing force of the brush on the steel plates were varied during application of bevel type and cup type wire brushes affording different brush shapes. The properties of spatters adhering to welding base metal surfaces have also been previously reported. Using model spatters, this study experimentally determines the brush forces received by spatters during wire brushing of base metal with adhered spatters and establishes the relationship with the processing conditions. The paper further examines the adhesive forces and shapes of spatters unable to be removed by wire brushing of welding base metal surfaces with adhered spatters, establishes the relationship with the adhesion site temperature of the base metal surface, and considers the limits of spatter removal by wire brushing.

Research on the path and velocity of spatter in manual metal arc welding

Summary In this paper we studied the loci (paths) and the velocities of scattering spatter in shielded metal arc (MMA) welding with high titanium oxide type electrodes. We examined only spatter that flew off at a right angle to the weld line and passed through a slit of 4 mm by 75 mm. The loci of the spatter were photographed when they scattered in the air and their velocities were calculated from the camera shutter speed. We also simulated the loci and velocities of the spatter and the experimental data and the calculated values were compared. In the experiment we examined 110 spatter particles whose diameters ranged from 0.1 to 1 mm. The spatter particles flew around on the surface of the base metal within a 500 mm radius circle. They flew in the air for less than about 0.5 seconds. And the highest velocity was 6 m/see. The Reynolds numbers of the spatter were less than 7. They were given by Re = d × V/1 (d is the diameter of spatter. V is the velocity of the spatter v is the coefficient of kinematic ve...

Factors affecting adhesion of spatter: Study of spatter occurring during arc welding (2nd Report)

Summary In CO2 gas-shielded arc welding, spatter is scattered and adheres to the base metal surface. The main factors affecting any difference in the bonding force remain obscure. This paper examines the bonding force of spatter adhering to the surface of SS400 base metal (rolled steel sheets) under different temperature conditions in CO2 gas-shielded arc welding using 1.2 mm dia. solid wire. The following four types of base metal surface condition were adopted: Type 1: As-received surface covered with an oxide film; Type 2: Ground surface machined with a plain grinder (Rmax = 0.6 μm); Type 3: Surface with fume adhering to the ground surface; Type 4: Free-ground surface machined with a disc grinder (Rmax = 7–16 μm). The base metal was heated by a 14 mm dia. x 600 mm ceramic heater arranged on the back of the base metal. The bonding force was measured as the shearing force of the spatter. Some 400 spatter particles on each surface were examined. The particles mostly have diameters ranging between 0.4–1.4 m...

Acting Force at Removing Spatter by Wire Brush and Its Limit. Study on the Finishing of Weld Metal Surface. Report 2.

In the arc welding, spatters attached around the bead of base metal. The adhered spatters lower the surface quality of the welding product. Therefore, it is very important to remove the spatters from the welding product. In general, wire brushes of bevel type or cup type have been used to remove the spatters. However, the adherent force of spatters on base metal is not constant. Then, the removal force, which is needed to remove the adhered spatters, is not also constant. Moreover, spatters are scattered on the base metal. Therefore, in order to remove the spatters by the brush, it is very important to clear the relationship between brushing conditions and the removal behavior of spatters.In this study, the removal forces of the adhered spatters are measured by using the removal tool to which strain gages attached. The shapes of the adhered spatters are also measured. Moreover, the force that is applied to the spatter in the brushing has been measured by using a model spatter. The shape of the model spatter is very similar to that of the adhered spatter. A steel plate with scale is used as a base metal. In brushing the metal, the pushing force of the brush is 29.4 N and the holding angle, that is the angle between the brush and base metal, is 15, 20, 25, or 30 degrees.As the result, it is indicated that the applied force to the model spatter in the brushing increases with the height of model spatter proportionally. The holding angle of the wire brush has little influence on the applied force to the model spatter. When the temperature of base metal is less than about 450 K, most of the removal shear forces of spatters are less than about 50 N. In this case, all of the attached spatters can be removed by the brushing. However, when the temperature of the base metal become high, the removal shear force become large and it become hard to remove all of the adhered spatter.

Measuring the force required to remove spatter from base metal: Research on spatter caused by arc welding (Report 1)

Summary This study deals with shielded metal arc (manual metal arc, MMA) welding and CO2 gas shielded arc welding, measuring the force required to remove adhering spatter from the surface of base metal by using different filler metals and by changing the conditions of the surface of the base metal. Rolled steel for general structural use (SS400) was used as base metal. A high titanium oxide type electrode and a low hydrogen type electrode were used for shielded metal arc welding, a solid wire and a flux‐cored wire were used as filler metal for CO2 gas shielded arc welding respectively. In order to examine the relationship between the condition of the surface of the base metal and the force required to remove spatter, a base metal whose surface was ground by an electric grinder, one which was not ground by an electric grinder, and another which was coated with an anti‐spatter compound were used for the experiments. Whichever filler metal was used, the spatter which adhered to the surface of the base metal ...

The Lean Hunting Phenomenon in Gasoline Engines - part 2

The hunting phenomenon which occurs at the lean air-fuel ratio and under light conditions was studied and it was disclosed that this was not mechanical hunting and the fuel flow delay into the cylinder had a dominant effect on this lean hunting. This paper first describes the experiments which demonstrate that such a fuel flow delay can occur by changing the throttle position sinusoidally in various periods, and that Pmax (the maximum pressure in the cylinder) responds quite differently according to the magnitude of the air-fuel ratio; and then describes the effects of ignition energy and ignition timing on lean hunting.

The lean hunting phenomenon in gasoline engines

A quite interesting self-excited oscillation phenomenon in engine speed, which may not be explained with the classical theory of mechanical hunting, is studied experimentally. The effects of the various engine operating variables on the phenomenon are examined using a four cycle single cylinder gasoline engine with an inertia governor. It was found that the phenomenon occurs when engines are operated at a lean air fuel ratio under light load conditions, and that the hunting phenomenon is ascribable to the temporary shift in air fuel ratio from the steady state value. This shift in air fuel ratio occurs due to the fuel flow delay into the cylinder caused by the fact that the fuel flow into the cylinder cannot follow the movement of the throttle valve.