Structural Design and Optimization of Herringbone Grooved Journal Bearings Considering Turbulent

In order to improve the performance of the traditional constant-width herringbone grooved journal bearing in a computed tomography tube under a high-temperature environment, the present study designed a convergent herringbone grooved journal bearing (HGJB) structure lubricated by liquid metal. The bearing oil film thickness and the Reynolds equation considering the influence of turbulence are established and solved by using the finite difference method in the oblique coordinate system. The performance of the two bearings was compared, and the static and dynamic performance change trends of the two bearing structures under different eccentricities were systematically studied. The results show that the convergent herringbone grooved journal bearings are superior to the constant-width herringbone grooved journal bearings in terms of bearing capacity and stiffness coefficient. At the same time, the influence of structural parameters, such as the number of grooves, helix angle, groove to ridge ratio, groove depth on the performance of the constant-width herringbone grooved journal bearings, and the convergent herringbone grooved journal bearings was studied. Finally, we conclude that the performance of the convergent herringbone grooved journal bearings is optimal when the number of grooves is 15–20, the helix angle is 30–45°, the ratio of the groove to ridge is 1, and the groove depth is 0.02 mm −0.024 mm. This research has provided the thinking and reference basis for the design of liquid metal bearings for high-performance CT equipment.

Experimental Investigations into Assessment of Thrust Force and Temperature in Bone Drilling

Drilling of bone is a challenging task for surgeons due to its effect on bone tissues. During drilling, it is noted that the temperature of bone increases. This increase in temperature if above 47°C causes thermal necrosis. Experiments were conducted to study the effect of input drilling parameters and drill bit parameters on bone health. To plan experiments a full factorial design method was used. An analysis is done on the effect of input parameters on thrust force and temperature of bone. The analysis of results shows an increase in thrust force and temperature when the feed rate increases and the spindle speed decreases. Further, the analysis of results shows an increase in thrust force and temperature when point angle increases and helix angle decreases. The increase in thrust force results in temperature rise. Scanning electron microscopy is done to analyze the surface topography of drilled hole. SEM image analysis shows an increase micro-crack in the drilled area when the thrust force and temperature increases.

MEASUREMENT OF THE GEOMETRY OF MANUFACTURED DRILLS USING OPTICAL SCANNING

This article deals with the control of the geometry of manufactured tools. The geometry of the cutting tool has a great influence on the machining process. One of the processes of manufacturing cutting tools is grinding. Grinding cutting tools is a complex process after which it is necessary to check the geometry of the tools. Five solid drilling tools were manufactured for the experiment. The measured parameters were tool diameter, helix angle, point angle, rake angle, relief angle and core diameter of the cutting tools. The geometry of the cutting tools was measured on a non-contact structured 3D scanner ATOS Triple Scan light. The measurement results were evaluated using GOM software. The scanning results were compared with the geometry measurement on an optical measuring device Zoller Genius 3s. It has been found that the use of a non-contact structured 3D scanner is suitable for checking the geometry of cutting tools. Furthermore, the article deals with the roughness arising when grinding a sintered carbide flute.

Consume Power Torque and Conveyor energy efficiency for a Horizontal Screw Conveyor with three different Screw Flight –A Comparison

Material handling cost plays crucial role in any manufacturing industries. A judicious selection of material handling system or equipment can only help to enhance productivity and thereby increasing profitability of an industry. Extensive studies require for establishing cost effective solution related to selection of right handling system. The objective of work is to find out running cost associated with screw type horizontal conveyor through experimental investigation of consume power and associated torque against three different types of screw flight(Continuous, Ribbon and Cut Flight) of same nominal diameter and pitch while keeping conveying distance as constant with same material at different screw speed. The experiment was conducted against two different trough heights for finding out mass flow rate. The consume power, torque and conveying energy efficiency calculated with three different screw flight and the results were compared for analysis. Hence on the basis of experimental results, conclusion was drawn. Present work confirming experimentally that the consume power at conveyor shaft and torque in case of ribbon flight was found to be 10 percent less than that of the continuous screw type of same nominal diameter, pitch and helix angle with same range of speed against single conveying material type in case of both the trough height(112 mm and 180 mm), which was in line with the statement made earlier[6]. In addition to that a trial has been made to establish a comparison in terms of consume power in between ribbon and cut flight against a constant trough height, which was not reported earlier. This comparative study may be helpful for taking decision in selecting material handling equipment type for specific application area. Now a day overall energy consumption becomes serious concern for different industries.

Using the Box–Behnken Response Surface Method to Study Parametric Influence to Improve the Efficiency of Helical Gears

Studying gear power loss theoretically and determining the efficiency of a helical gear drive depend on many geometrical and working parameters, such as rotation speed, tooth number, gear ratio, helix angle, and torque, among others. In this paper, the Plackett–Burman screening design and the Box–Behnken response-surface method are used to consider how the above parameters influence gear drive efficiency, and experimental models are provided to evaluate these influences. The present results can be used to select the efficiency when calculating and designing gear transmissions and to choose the parameters for improving gear transmission efficiency.

Research on Centroid Distribution and Dynamic Characteristics of Irregular Tooth End Milling Cutters

For irregular end milling cutters, the incomplete equality of the pitch angle and helix angle will lead to an uneven mass distribution. The problems of centroid distribution caused by this, and whether it would affect the dynamic characteristics of milling cutters, have not been systematically studied. In this paper, through the proposed mathematical model, the centroid positions of each radial section of four types of end milling cutters, with equal overall eccentricities and different structures, are calculated, respectively. The centroid distribution of end milling cutters is studied and analyzed. Combined with finite element analysis, the vibration mode, frequency, and resonance frequency band of each type of end milling cutter, under the same dynamic excitation, is obtained. Based on a study of the dynamic characteristics of various types of end milling cutters, it is found that the response displacement of the variable pitch variable helix end milling cutter is the smallest, which is 0.043800 mm. With the same level of accuracy, its dynamic performance is the best. On the premise of not changing the overall eccentricity of the end milling cutter, a new idea for the structural design to improve the dynamic characteristics of the end milling cutter is provided.

Influence of Groove Structure Parameters Based on Optimal Mass Transfer Coefficient on Vaporization Characteristics and Sealing Performance of Liquid Film Mechanical Seals

In this study, a spiral groove liquid film vaporization model based on the viscosity–temperature equation, fluid internal friction, saturation temperature, and pressure relationship equation was established. Using a multiphase flow model based on the finite volume method, the influence of the change in the mass transfer coefficient on the vaporization of the liquid film was studied. Moreover, the influence law of structural parameter changes in liquid film vaporization characteristics and sealing performance was analyzed. The results indicate that, with an increase in the mass transfer coefficient, the average vapor phase volume fraction first increases and then gradually stabilizes. When calculating the average vapor phase volume fraction, it is necessary to consider the influence of the mass transfer coefficient, whereas its effect on the opening force and leakage can usually be neglected. Under the optimal mass transfer coefficient conditions, the average vapor phase volume fraction increases with an increase in the helix angle, groove-weir ratio, and groove depth. By comparison, with an increase in the groove-diameter ratio, the average vapor phase volume fraction first increases and then decreases. The opening force decreases with an increase in the helix angle, groove-to-weir ratio, and groove depth. On the other hand, it first decreases and then increases with an increase in the groove-diameter ratio. The leakage rate increases first and then stabilizes with an increase in the helix angle. Moreover, it increases continuously with an increase in the groove-diameter ratio, groove-weir ratio, and groove depth.

Investigation of the Influences of Thrust Loads Resulted by Helix Angle Directions of Planetary Gear Sets on Bearing Power Losses in Automotive Planetary Gear Trains

In the recent automotive industries, automotive technologies for improving fuel efficiency have focused on the developments of reducing power losses in a transmission. As a well-developed and conventional power transmitting system, an automatic transmission is still widely used in many automotive vehicles. The automatic transmission is co-axially designed with several planetary gear sets and other mechanical parts. The co-axial arrangements and gear helix angles make the transmission necessarily include bearings for supporting loads and allowing relative rotations. In this study, the influences of thrust loads yielded by helix angle directions of planetary gear sets on bearing power losses are presented by performing the structural and power loss analysis. Bearing power losses consist of mechanical and spin power losses. For calculating thrust loads and bearing rotations, a complete transmission model is constructed by using an example structure, and structural analysis is performed for the combinations of helix angle directions of the gear sets. Finally, bearing power losses are computed by using the bearing power loss model, and the results of the entire combinations of helix angle directions are discussed.

DESIGN AND PERFORMANCE TEST OF DIRECT SEED METERING DEVICE FOR RICE HILL

In order to meet the requirements of rice field precision direct seeding in rows and hills, a spiral grooved seed metering device for rice field precision direct seeding in hills is designed. The Matlab software is used to study the movement trajectory of rice buds in the spiral groove during the seeding process. Based on the quadratic regression-orthogonal rotation combination design, and taking the working speed of the seeding wheel, the spiral groove length and the helix angle of the spiral groove as the test factors, as well as the qualified rate of hill diameters, the qualified rate of hill grains and the miss-seeding rate as the indicators, the seed metering performance is tested by JPS-12 metering device test bench. The test data are analyzed by using Design-Expert 6.0.10 software to obtain a mathematical model between the factors and indicators. The test results show that when the spiral groove rise angle is 71.0°, the spiral groove length is 10.8mm, and the working speed of the metering wheel is 23.2r/min, the qualified rate of hill diameter, qualified rate of hill grains and miss-seeding rate are 91.06%, 94.64% and 3.64% respectively. The seeding performance meets the agronomic requirements of rice field seeding.