Influence Of Helix Angle Research Articles

Computational fluid dynamics analysis of the airflow field inside a cyclone of a combine harvester with adjustable blocks

Existing combine harvesters used for rapeseed still have challenges. To simplify the structure of the harvester and reduce losses a new type of cyclone is proposed as a cleaning device. It has several spiral arranged adjustable magnetic blocks fitted at the bottom of the cyclone to disrupt and reduce any dead zone in the airflow field. To establish the effect of altering the dead zone of the airflow field, the motion of a single rapeseed in the cyclone was analysed based on the kinematics and dynamics. A simulation model of the cyclone, based on computational fluid dynamics, was established to optimise the arrangement of the magnetic blocks within the cyclone. The influences of helix angle, distance and spiral number of the magnetics blocks on the airflow were explored through a single-factor simulation experiment, which determined the optimal number of spirals as 4. Subsequently, the air velocity of the inlet and materials other than grain (MOG) at the outlet were added as factors to carry out the Box-Behnken designed experiment. Results showed the optimal combination of parameters were an inlet air velocity 4.2 m s−1, a MOG outlet air velocity 27.4 m s−1, a helix angle 64.2° and distance between magnetics blocks 52.4 mm. Bench tests and field experiment were conducted to validate the performance of the cleaning device under the optimum conditions. The results showed that the average cleaning ratio and loss ratio of the rapeseed were 88.96% and 4.12%, respectively.

Influence of helix angle on flow and heat transfer characteristics of lead–bismuth flow in helical-coiled tube bundles

The SST k-ω model and turbulent Prandtl number model are used in this paper to simulate liquid lead–bismuth cross-flow and heat transfer in helical-coiled tube bundles with different helix angles. The numerical method is validated using relevant experimental data from previous research. The helix angle significantly influences the flow and heat transfer due to the flow pattern transition and continuously changing tube arrangements. The friction factor and Nusselt number both increase firstly and then decrease with the increase of the helix angle. The flow fields are analyzed from the perspective of velocity magnitudes, streamlines, vortex structures and turbulence intensities. The complicated flow structure induced by the helix angle significantly impacts the flow and heat transfer performance. The field synergy principle is applied to analyze the enhancement of heat transfer. The achievement in this paper can be a reference for numerical methods and design optimization of liquid metal H-OTSG.

Influence of Helix Angle on Flow and Heat Transfer Characteristics of Lead-Bismuth Flow in Helical-Coiled Tube Bundles

Influence of Helix Angle on Flow and Heat Transfer Characteristics of Lead-Bismuth Flow in Helical-Coiled Tube Bundles

Analysis of transient mixed elastohydrodynamic lubrication in planetary roller screw mechanism

Previous lubrication studies for planetary roller screw (PRSM) are mainly concentrated on steady-state condition without the consideration of entrainment angle. However, PRSM always operates in transient situations with frequent startup and shutdown process. In this paper, uneven friction distribution, the influence of helix angle on lubricating properties and transient behavior in the roller-screw interface are analyzed comprehensively based on transient mixed-EHL model, which considers real three-dimensional (3D) machined roughness and arbitrary entrainment velocity. The results show that smaller helix angle is beneficial to improve the lubrication performance. Increasing the rotating speed and declining axial load can moderate the uneven friction distribution. Besides, a relatively large angular acceleration may enlarge the film thickness and reduce the friction at the shut down status. The numerical simulation model can be utilized as a design optimization tool for the PRSM.

The influence of helix angle of router bits on chip flow, roughness and noise level in milling different grain angle orientation of teak wood

ABSTRACT This study was done to investigate surface roughness, noise level, chip shapes and chip flows characteristic in milling teak wood by conventional and helical router bits. Down-milling process compared to up-milling process produced better surface roughness, lower noise level, and flow chip. Better surface roughness (R a value) was produced by the router bits with higher helix angle compared to lower helix angle. Noise level decreased with increasing in the helix angle of the router bits. The increasing in the angle of the wood grain would increase the values of surface roughness and noise level. With increasing helix angle of the bits the amount of spiral and flow chips increased and granule chips were reduced. The investigations have clearly confirmed that the helical edge is considered to be a valuable design to improve upon the performance of the straight edge for wood milling applications.

Analysis of mesh stiffness of herringbone gear considering modification

Herringbone gear is a key component in the reducer. Its mesh stiffness is an important parameter in gear dynamics research. In this paper, an improved Velex method is proposed to calculate the mesh stiffness of herringbone gears, and compared with Weber method and Finite Element Method (FEM), the accuracy of the method is proved. Meanwhile, the influence of helix angle and modification coefficient on the stiffness of the gear is analyzed by Weber method. The results show that the two parameters have different degrees of influence on the mesh stiffness of the herringbone gear, which provide a theoretical basis for the design of the herringbone gear transmission. Finally, by the calculation of the stiffness of the herringbone gear, the difference between the herringbone gear and the helical gear is compared and analyzed, and the conclusion that the herringbone gear is not a simple superposition of the helical gear is obtained. Because of the difference between the helical gear and the herringbone gear, it is of great value to the stiffness analysis of the herringbone gear.

Parametric Studies of Mechanical Power Loss for Helical Gear Pair Using a Thermal Elastohydrodynamic Lubrication Model

In this study, a comprehensive mechanical efficiency model based on the thermal elastohydrodynamic lubrication (TEHL) is developed for a helical gear pair. The tribological performance of the helical gear pair is evaluated in terms of the average film thickness, friction coefficient, mechanical power loss, mechanical efficiency, etc. The influence of basic design parameters, working conditions, thermal effect, and surface roughness are studied under various transmission ratios. Results show that the contribution of thermal effect on the tribological performance is remarkable. Meanwhile, the rolling power loss constitutes an important portion of the total mechanical power loss, especially around the meshing position where the pitch point is located in the middle of contact line and the full elastohydrodynamic lubrication (EHL) state with the friction coefficient less than 0.005. The proper increase of normal pressure angle and number of tooth can improve the tribological performance. The influence of helix angle on the mechanical efficiency is less significant. A positive addendum modification coefficient for pinion and a negative addendum modification coefficient for wheel are good for improving the mechanical efficiency. The results provide the tribological guidance for design of a helical gear pair in engineering.

Influence of helix angle on bending fatigue strength of case-carburized helical gears

Influence of helix angle on bending fatigue strength of case-carburized helical gears

Wpływ kąta pochylenia linii zęba na wytrzymałość kół zębatych wykonanych metodą MEM

Wpływ kąta pochylenia linii zęba na wytrzymałość kół zębatych wykonanych metodą MEM

On the influence of helix angle and face width on gear windage losses

This paper investigates the windage power losses generated by helical gears rotating in pure air based on experimental results and a computational fluid dynamic code. It is found that the simulated flow patterns are totally different from those calculated for spur gears and that both tooth face width and helix angle are influential. The windage losses derived from Dawson’s and Townsend’s formulae are critically assessed using computational fluid dynamic results thus highlighting the limits of a unique formulation for accurate windage loss prediction. Finally, an analytical approach is suggested which gives good results providing that the flow rates at the boundaries of the inter-tooth domains can be estimated.

Performance analysis of micro drill bit with asymmetric helix groove

Purpose – The purpose of this paper is to present a new method to optimize the micro drill bit based on finite element analysis, and analyze the performance of the asymmetric helix groove micro drill bit and provide a way to conduct the optimization of micro drill bits. Design/methodology/approach – First, the stress and deform of the micro drills were analyzed in ANSYS. Second, the influence of helix angle, web thickness and ratio of flute to land on stiffness was explored. Combining the former two results, a better set of parameters were optimized. Third, the modal analysis and harmonic response analysis of the optimized micro drill bit were analyzed in ANSYS. Finally, an experiment was carried out to verify the performance of the asymmetric helix groove micro drill bit. Findings – The stress and deform of the asymmetric helix groove micro drill bit are not symmetric. The rigidity is getting better with the web thickness increasing in the selected range; while, the rigidity is getting worse with the helix angle and ratio of flute to land increasing in the selected range. The natural frequencies of the optimized micro drill bit are far away from the excitation frequency, and the response displacement is very small under the excitation of the spindle. In the drilling experiment, the optimized micro drill bit performs well. Research limitations/implications – In this paper, the diameter of the asymmetric helix groove micro drill bit was 0.3 mm and the cross-section shape was not considered. The future research work should consider different diameters and cross-section shapes. Originality/value – Analyzing the influence of three main geometry parameters on the rigidity in ANSYS, a better set of parameters were optimized from the analysis results. The drilling experimental results show that this method is of great significance for obtaining the appropriate parameters of asymmetric helix groove micro drill bits.

An Investigation of Wear of Ball End Milling Cutter for High-Speed Milling of Hardened Cr12MoV Steel

The high-speed milling experiments on hardened Cr12MoV steel were carried out with ball end milling cutter of different edge parameters. The influences of helix angle and rake angle on tool life and surface roughness were focused on. Meanwhile, the impacts of edge parameters on cutting edge stiffness and flank wear were analyzed on the condition of high-speed milling. It carried out that smaller helix angle and negative rake angle selected during high speed milling can guarantee quality of surface manufactured as well as longer tool life.

Experimental study on micro EDM-drilling of Ti6Al4V using helical electrode

There is a growing interest in the machining of micro-holes with high aspect-ratio in difficult-to-machine alloys for the aerospace industry. Processes based on electro discharge machining (EDM) and developed for the manufacture of both micro-electrode and micro-hole are actually used, but most of them involve micro-EDM machines. In this work, the influence of EDM parameters on material removal rate, electrode wear, machining time and micro-hole quality when machining Ti6Al4V is studied. Due to an inefficient removal of debris when increasing hole depth, a new strategy based on the use of helical-shaped electrodes has been proposed. The influence of helix angle and flute depth with respect to process performance has been addressed. Main results include 37% reduction in machining times (hole diameter 800μm) when using electrode helix angle of 45° and flute-depth of 50μm, and an additional 19% with flute-depth of 150μm. Holes of 661μm diameter and as much as 6.81mm depth, which yields in aspect ratio of 10:1, have successfully been machined in Ti6Al4V.

Influence of Helix Angle in Low Immersion Milling Forces and Stability Analysis: down-Milling, up-Milling and Slotting

Chatter is the most obscuring phenomenon and significant amount of research has been documented regarding prediction, control and elimination of chatter. Chatter is still a main hindrance in achieving good surface finish and productivity. This paper presents the influence of helix angle of milling cutter in down-milling, up-milling and slotting operation. Altintas multi-frequency solution (MFS) is advanced by adding the impact of helix angle in milling forces. A comparison is made for stability lobes diagram based on the helix angle model for different helix angles against the Altintas multi-frequency solution model (MFS) and zero order approximation (ZOA) model. The comparison shows that for small helix angle the stability lobes follow the Altintas (MFS) model and for high helix angle the stability lobes follow the Altintas (ZOA) model. The experimental results prove the simulations. Introduction

Vibration Analysis of Gear Transmission System in Electric Vehicle

This paper presents a systematic research on the gear transmission system of the electric vehicle. An accurate 3-D model of the gear transmission system is established in UG (Unigraphics NX) using software Gearwizard, and then imported to ADAMS/View environment. Based on the contact force of ADAMS, the vibration at 3 different test points of the model are simulated. The simulation results seem to be in good accordance with the test results, which proved the validity of the gear transmission model. Finally, the influence of helix angle on vibration at 3 different test points are also researched. The results of the total analysis can be used further to optimize the gear transmission system of the electric vehicle.

Analysis of the Influence of Mill Helix Angle on Chatter Stability

Current methods for estimating chatter stability limits for milling do not consider the influence of the helix angle and the consequent phase lag between the forces appearing at different sections of the mill. Budak and Altintas' multifrequency solution is extended to include the helix effect, and results are compared with results of semi-discretization and experiments. As a conclusion, the helix has an important influence on the areas of added lobes (flip lobes), while the influence on the traditional lobes is negligible. Flip lobes become closed curves separated by horizontal lines where the depth of cut equals a multiple of the helix pitch.

An investigation into the influence of helix angle on the torque-thrust coupling effect in twist drills

This paper presents an experimental investigation into the torque-thrust coupling effect in twist drills. A set of cross-coupling stiffness coefficients (Kft and Ktf) are defined. The influence of helix angle on torsional and the cross-coupling stiffnesses is studied. The coupling interaction (as measured by Kft and Ktf) is strongly influenced by the helix angle and has a distinct maxima around 28°. Also, the magnitudes of the coefficients increase parabolically with drill diameter. The pure torsional stiffness also has a maxima around the same helix angle. Under axial restraint, the torsional stiffness increases by 10 to 25% owing to the coupling effect. The larger the torque-thrust interaction, the larger is this increase in torsional stiffness. The findings of this investigation is proposed as a probable basis for the traditional popularity of a 28 to 30° helix angle for drills.

Influence of Helix Angle. Load and Speed on Noise of a Helical Gear

Influence of Helix Angle. Load and Speed on Noise of a Helical Gear

On Milling Process Using a Plain Milling Cutter with Helix Angle

In milling process using a plain milling cutter with helix angle, three components of cutting force corresponding to the varying undeformed chip thickness are measured simultaneously and precisely by unique optical method, and the influences of helix angle on the variational configuration of cutting force in up milling and in down milling are discussed in detail. Based on the experimental results, the mechanics of milling process using a plain milling cutter with helix angle is discussed from the viewpoints of apparent friction angle on tool face, chip flow direction and effective rake angle, and the role of helix angle of a cutter in milling process is clarified experimentally.

On the Drilling of Metals: 2—The Torque and Thrust in Drilling

Abstract The problem of computing the torque and thrust developed on a drill is approached from dimensional reasoning and the rules of cutting-force development in two-dimensional cutting. The drill quantity equivalent to the feed in ordinary machining is found to be the product of feed and diameter. General equations are derived for drill torque and thrust and found to be in good agreement with experimental data obtained by use of a drill dynamometer. The web thickness of the drill is found to influence thrust and torque significantly, but the influence of helix angle is found to be relatively unimportant.