Ratio Of Circumferential Velocity Research Articles

Features of furrow formation with rotary and arrow-headed working bodies

BACKGROUND: Soil-cultivating machinery and tools equipped with rotary working bodies are effectively used at operations of surface tillage. However, the subject of furrow formation with rotary working bodies is unaddressed to the full extent that makes it a relevant issue for the study.
 AIMS: Revealing the patterns of furrow formation with rotary working bodies equipped with the cutting blades made along the elliptical line at the angle to the working body rotation plane.
 METHODS: The grapho-analytical method is presented in the article and used for defining the parameters of a furrow formed with the following types of rotary working bodies: a spherical disk with a closed surface, an annular working body and a rotary working body with the cutting blades made along the elliptical line and set up at the acute angle to the rotation axis. The experiments were carried out in controlled laboratory conditions with a physical model of the rotary working body with the cutting blades made along the elliptical line in a soil channel filled with dampened sand. During the experiments, the attack angle was 20-40 with a step of 10 and the kinematic coefficient, which is the ratio of circumferential velocity to transverse velocity, had the following values: 1, 1.4, 1.8 and 2.2.
 RESULTS: The cutting blades made along the elliptical line form short furrows with the ellipse-shaped cross-section and with the angle of inclination from the movement direction of 20-40 depending on the attack angle and the kinematic coefficient. Meanwhile, the furrows formed with the working body have the form of a parallelogram at the top view.
 CONCLUSIONS: The practical value of the study lies in revealing the features of furrow formation with rotary working bodies equipped with the cutting blades made along the elliptical line aimed to making a flat bottom of a furrow necessary for grain planting.

Effect of Cutting Conditions on Tool Wear in Driven Rotary Cutting of Maraging Steel

In this paper, driven rotary cutting of maraging steel was carried out and the influence on tool wear of difference cutting conditions was investigated. As cutting conditions, different coolant conditions, cutting speeds, circumferential velocity ratios, tool inclination angles, tool rotation directions and normal rake angles were tested. We found that as the coolant quantity decreased and cutting speed increased, the width of flank wear increased. It was also found that the circumferential velocity ratio, tool inclination angle, tool rotation direction and normal rake angle have optimal conditions that decrease wear. Optimal conditions were chosen, and a tool life test was carried out. As a result, driven rotary cutting was achieved with 11 or more times the tool life of conventional turning.

0525 Effect of cutting fluid on chip adhesion and tool wear in driven rotary cutting

In driven rotary cutting, adhesions sometimes occur on the tool, causing increased wear. The influences of the coolant supplying method on adhesion and wear was investigated, because how easily adhesions can occur depends on the cutting temperature. Results showed that in a circumferential velocity ratio of 1.0, there is no adhesion on the tool after cutting. In a circumferential velocity ratio of 2.0, adhesion occurred with overcooling of the flood coolant, and wear increased by adhesions to the rotating tool.

The flow around a flat plate acting in rotational and translational oscillations. Numerical analysis by the discrete vortex method.

The discrete vortex method with comformal mapping has been applied to analyze the flow around a flat plate acting in the combination of rotational and translational oscillations in a uniform flow, where the rotational oscillation is about the front end of the plate. Numerical calculations are performed for various nondimensional frequencies (ratio of circumferential velocity at rear end of plate to uniform velocity), angles in rotational oscillation, amplitudes in translational oscillation and phase angles in both oscillations. Vortex patterns and unsteady forces are obtained. As a result, the behavior of vortices shed from both ends of the plate greatly affects the thrust. The thrust on the plate increases as the nondimensional frequency increases.

Numerical and Analytical Study of Fluid Dynamic Forces in Seals and Bearings

A numerical model based on a transformed, conservative form of the three-dimensional Navier-Stokes equations and an analytical model based on “lumped” fluid parameters are presented and compared with studies of modeled rotor/bearing/seal systems. The rotor destabilizing factors are related to the rotative character of the flow field. It is shown that these destabilizing factors can be reduced through a descrease in the fluid average circumferential velocity. However, the rotative character of the flow field is a complex three-dimensional system with bifurcated secondary flow patterns that significantly alter the fluid circumferential velocity. By transforming the Navier-Stokes equations to those for a rotating observer and using the numerical code PHOENICS-84 with a nonorthogonal body fitted grid, several numerical experiments were carried out to demonstrate the character of this complex flow field. In general, fluid injection and/or preswirl of the flow field opposing the shaft rotation significantly intensified these secondary recirculation zones and thus reduced the average circumferential velocity, while injection or preswirl in the direction of rotation significantly weakened these zones. A decrease in average circumferential velocity was related to an increase in the strength of the recirculation zones and thereby promoted stability. The influence of the axial flow was analyzed. The lumped model of fluid dynamic force based on the average circumferential velocity ratio (as opposed to the bearing/seal coefficient model) well described the obtained results for relatively large but limited ranges of parameters. This lumped model is extremely useful in rotor/bearing/seal system dynamic analysis and should be widely recommended. Fluid dynamic forces and leakage rates were calculated and compared with seal data where the working fluid was bromotrifluoromethane (CBrF3). The radial and tangential force predictions were in reasonable agreement with selected experimental data. Nonsynchronous perturbation provided meaningful information for system lumped parameter identification from numerical experiment data.

Improvements in Lightly Loaded Rotor/Bearing and Rotor/Seal Models

A model for lightly loaded steadily rotating shaft/bearing/seal systems is proposed in this paper. The model is based on modal characteristics for the rotor, and rotational characteristics for the fluid dynamic forces generated in bearings and/or seals. The fluid average circumferential velocity ratio as a nonlinear function of shaft eccentricity represents a key factor in the model. The model is extremely useful for rotor stability analysis. The model adequacy was proved for one and two lateral mode models of rotors.

The flow around a flat plate acting in rotational oscillation. Numerical analysis by discrete vortex model.

The discrete vortex model with conformal mapping method has been applied to analyze the flow around the flat plate acting in rotational oscillation about the front end of a plate in a uniform flow. Numerical conditions are determined by comparing with the result of flow visualization already reported.. Then, numerical calculations are performed for various nondimensional frequencies (ratio of circumferential velocity at end of plate to uniform flow velocity) of more than 0.1 and amplitudes. Vortex patterns and unsteady forces are obtained. As a result, a thrust is generated on the plate for nondimensional frequencies of more than 0.1 by this oscillation. The thrust on the plate increases as the amplitude becomes large under the condition of these frequencies.

Trial production of a specific sliding varying type contact roller testing machine and its characteristics.

In the case of a general roller testing machine which is- employed at researching the tooth surface fatigue of gear materials, the specific sliding on test roller is constant during a rotation of the test roller. In this report, a new roller testing machine which can give a continuously varying specific sliding to the test roller was developed using an eccentric gear mechanism and its characteristics were elucidated. In this new type machine, the specific sliding of the test roller changes continuously in the ranges of -125% to 0%, -50% to +33% and 0% to +56 %. The minimum oil film thichness between the test rollers changes during a rotation of the roller with the change of circumferential velocity ratio of the roller pair. The change of the tangential force between the rollers during a rotation of the roller depends upon the changes of the normal force and the friction coefficient between the rollers.

Some Computations of Circumferential Wave Velocities

The theory of circumferential waves has been extended for large cylinders (ka≫1) in the manner developed by Grace and Goodman [J. Acoust. Soc. Am. 39, 173–174 (1966)]. Numerical evaluations of the secular determinant have been made. The results can be checked easily with the limit ka→∞. Certain difficulties arise in the asymptotic expansions of Bessel functions, which depend on whether the ratio of circumferential velocity to shear velocity is greater than or less than unity. Values of the circumferential wave velocity and attenuation have been computed for steel and aluminum for values of ka pertinent to the experimental data, which will be discussed in the following paper.