Increase Of Helix Angle Research Articles

Influence of helix angle on heat transfer characteristics of regenerative cooling in spiral channel

A rapid solution method for spiral line and a one-dimensional (1-D) heat transfer calculation model for spiral regenerative cooling channels (RCCs) are proposed to clarify the influence of the helix angle on the heat transfer characteristics of spiral RCCs in thrust chambers. The method based on the projection principle is characterized by a simple model and the ability to generate variable helix angles spiral line. The calculation model is characterized by high accuracy, with coolant pressure drop errors of less than 5 % coolant and coolant temperature errors of less than 20 % compared to experimental data. Utilizing the calculation model, research on the heat transfer characteristics of RCCs with varying helix angles is conducted. Results indicate that the coolant temperature rise and pressure drop increase as the helix angle increases. The peak values of the gas-side wall temperature occur at the throat and the contraction section. The throat peak value decreases with an increase in the helix angle, while the contraction section peak value increases. When the helix angle is 30°, the two peak values are close as well as the highest gas-side wall temperature is minimized. The highest wall temperature is only 1111K. The research results can provide guidance for the design and processing of spiral RCCs.

Parametric analysis of the mechanical behavior of Cu-Al-Be shape memory alloy strands for applications in self-centering systems

In this work, the mechanical behavior of Cu-Al-Be shape memory alloy (SMA) strands for applications in self-centering systems is discussed. The influence of the mechanical response from the wire level to the strand level is evaluated in order to define the strand configurations that provide the best mechanical properties for seismic control applications. Therefore, a comprehensive numerical analysis of 1 × 7 and 1 × 19 strand typology constructions is performed. Two boundary conditions and two different core materials are assessed: ends fixed or free to rotate; and strand core made of SMA or a soft material. A multilinear flag-shaped model is used as SMA constitutive law, which is integrated into four different linearized cable models. To validate the numerical analysis, four 1 × 7 strand specimens are fabricated and subjected to cyclic tensile tests with strain amplitudes of 3.5% and 5.5%. The results show that the cable models considering the Poisson effect are the most stable numerically, although they rely on asymmetric stiffness matrices. The energy dissipation capacity is controlled by the material damping ratio (3.2%) regardless of the strand configuration. Therefore, optimum conditions are obtained when most layers develop the maximum strain capacity of the material. Thus, the fixed ends condition is the best choice if maximum strength is desired, since the ductility gained by increasing the helix angle is negligible regardless of the core material. For this condition, the helix angle must be the same for all the layers. On the other hand, the free ends condition is the best choice if maximum strain is desired, since the strength decays rapidly as the helix angle increases. A self-centering device based on CuAlBe SMA strands has been modeled, obtaining promising results for seismic protection of structures.

A generalized closed-form model of cutting energy for arbitrary-helix cylindrical milling tools and its applications

The knowledge of energy consumption of different machine tool production processes leading to products is necessary for energy labeling of machined parts in the increasingly sustainability-aware world thus the need for better machining energy modeling techniques. The milling process dynamics is complicated thus numerical and averaging techniques are hitherto usually applied in the cutting energy modeling thus limiting decision-making. This work proposes a generalized force-based closed-form model for the milling process cutting energy. To the best of the author’s knowledge, the model is the first closed-form cutting energy model for milling which not only applies to the conventional cylindrical milling tools with constant helix angle but also to cylindrical milling tools with any helix angle variation. The demonstrated applications of the proposed model include modeling of milling machine electrical energy consumption, modeling/optimization of milling project energy/efficiency and helix angle optimization for passive reduction of cutting energy. The proposed model is checked with experimentally-verified results in literature. For example, the model agrees with numerically computed cutting energy in literature by absolute error of 0.0320%–0.4025% and modeling of milling machine electrical energy consumption using the proposed model recorded the goodness-of-fit indices of 0.9980 [Formula: see text]-value and −0.1271 mean percentage error compared to a published experimental data. A parametric plot and an optimization based on genetic algorithm showed that increase of helix angle increases cutting energy due to increased influence of edge forces, and the effect is more pronounced at higher helix angles. Various potential applications of the presented model are highlighted in the concluding section.

Multi-axis and cornering stiffness properties of non-pneumatic wheels with symmetric helical honeycomb spokes

Current non-pneumatic wheel (NPW) designs with non-helical honeycomb spokes generally show too high cornering stiffness and thereby rapid saturation of the cornering force, which may lead to inferior handling and directional control of the vehicle, particularly under high operating speeds. The design concept of NPWs with symmetric helical honeycomb spokes is thus proposed in this paper. Three-dimensional (3D) finite element (FE) models of a honeycomb NPW with symmetric helical spokes configurations of different cell and helix angles were developed in order to fundamentally study its multi-axis and cornering stiffness properties under a constant normal load. The validities of the developed NPW models with 0° helix angle and three different cell angles were demonstrated through comparisons of predicted wheel responses with results available in published studies. 3D simulations were conducted under two design constraints in terms of identical cell-wall thickness and identical load carrying capacity. The results suggest that increasing helix angle results in significantly greater in-plane shear stiffness of the honeycomb spokes and thus could effectively yield higher longitudinal and vertical stiffness of the NPW. An increase in helix angle also causes lower lateral stiffness for the wheel designs with 15.8° and 31.5° cell angles resulting from increases in the out-of-plane compliance of the spokes, apart from the notably lower cornering stiffness, particularly when it is increased to 30° and 45°. The cell-wall thickness, however, shows positive influences on multi-axis stiffness of the honeycomb wheel but negative effects on its cornering stiffness. The design concept of helical honeycomb spokes could offer better vehicle performances than the current designs in terms of braking/traction and handling characteristics. These are particularly important for promoting applications of the NPW in high-speed vehicles.

An analytical method for the meshing characteristics of asymmetric helical gears with tooth modifications

This paper establishes a time-varying meshing stiffness (TVMS) analytical method for asymmetric helical gear pairs based on the potential energy principle and slice method. The method considers the adjacent teeth' influence on the deformation of the gear body part. The proposed method is verified the reasonableness by finite element (FE) analysis. The basic parameters of asymmetric helical gear such as helical angle, pressure angle and tooth width are estimated for the meshing characteristics. The results show that the increase of helix angle, pressure angle of the driving side, normal modulus and tooth width will affect the contact ratio and maximum meshing stiffness of helical gears. The variation of these parameters can minimize the fluctuation of the TVMS curve when the overlap contact ratio reaches an integer. The variation trend of the loaded-static transmission error (LSTE) is opposite to that of the TVMS curve. The load share ratio (LSR) on a pair of gear pairs will decrease with the increase of the degree of reattachment. Furthermore, the influence of tooth modifications on TVMS is estimated by using the proposed method. The mean value of stiffness is reduced after the tooth modifications. The TVMS curve changes more gently after the tooth tip modification.

Influence of structural parameters of unbonded flexible pipes on bending performance

Unbonded flexible pipes have complex structural forms and numerous structural parameters. There are different degrees of contact and slip between the structural layers under bending loads, which brings challenges to the structural design and bending characteristics analysis of flexible pipes. In this paper, according to the law of energy conservation and deformation geometry theory, the mechanical equilibrium equation of each layer of unbonded flexible riser under bending load is established and the contact condition between layers is introduced in the first step. According to the slip state of the spiral strip, the response of the flexible riser under bending load was divided into three stages: no slip, partial slip and complete slip. The expressions of bending moment and bending stiffness were derived. The influence of structural parameters of tensile armor layer of unbonded flexible pipes on its bending performance under bending load is studied by using MATLAB software to compile the corresponding calculation program. The results show that the increase of friction coefficient between layers of tensile armor will improve the bending resistance of flexible pipes. The increase of helix angle will reduce the bending stiffness of flexible pipes in the initial stage. The increase of the number of spiral strips will increase the bending stiffness of flexible pipes in the initial stage. In the process of structural design of flexible pipes, the influence of the above structural parameters on the bending characteristics of flexible pipes should be taken into account.

Numerical simulation on coal loading process of shearer drum based on discrete element method

The drum is the working mechanism of the coal shearer, and the coal loading performance of the drum is very important for the efficient and safe production of coal mine. In order to study the coal loading performance of the shearer drum, a discrete element model of coupling the drum and coal wall was established by combining the results of the coal property determination and the discrete element method. The movement of coal particles and the mass distribution in different areas were obtained, and the coal particle velocity and coal loading rate were analyzed under the conditions of different helix angles, rotation speeds, traction speeds and cutting depths. The results show that with the increase of helix angle, the coal loading first increases and then decreases; with the increase of cutting depth and traction speed, the coal loading rate decreases; the increase of rotation speed can improve the coal loading performance of drum to a certain extent. The research results show that the discrete element numerical simulation can accurately reflect the coal loading process of the shearer drum, which provides a more convenient, fast and low-cost method for the structural design of shearer drum and the improvement of coal loading performance.

Numerical investigation on cooling heat transfer and flow characteristics of supercritical CO2 in spirally fluted tube at various inclination angles

The convective flow and heat transfer characteristics of supercritical carbon dioxide cooling in various inclined spirally fluted tubes, which is used under high pressure conditions for power plants, are investigated by numerical simulation in this study. Using the examined computational model, the distributions of the turbulent kinetic energy and the fluid velocity in each side of the groove varied with the inclination angles δ range from −90° to 90° are analyzed. The results show that the components of the buoyancy force in the mainstream and perpendicular to the mainstream have different effects on the flow behavior, especially near the cooling surface. The variation of the local heat transfer coefficient is also issued. In the gas-like region, the fluid velocity plays the main role, and the heat transfer coefficient increases with the decreasing δ. In the liquid-like region, the dominant impact factor is the velocity gradient, and the variation of the heat transfer coefficient with δ is opposite to that in the gas-like region, where the buoyancy has a more significant effect. The buoyancy effect will be more important with the increase of the helix angle and increase as the inclined upward flow. The optimal inclination angle corresponding to the maximum heat transfer coefficient is obtained, and it varies from −45° to 45° as the helix angle increases.

Meshing efficiency analysis of double helical gears considering tribo-dynamic coupling effect

In order to obtain accurate meshing efficiency of double helical gears, a calculation method of sliding friction power loss is proposed considering the tribo-dynamic coupling effect. Based on the mixed elastohydrodynamic lubrication (EHL) theory, the initial friction coefficient of tooth surface is obtained and the friction excitation is calculated. Considering the tribo-dynamic coupling effect, a sixteen-degree-of-freedom tribo-dynamic model of double helical gear pair is established, including time-varying mesh stiffness, friction excitation, backlash and transmission error. The tribo-dynamic behaviours of gear pair are analysed before and after coupling, and then the sliding friction power loss and meshing efficiency of double helical gears are obtained. The research results show that after tribo-dynamic coupling, the friction coefficient and friction excitation of double helical gear pair increase, and the meshing efficiency decreases. The meshing efficiency of gear pair increases with the increase of helix angle and pressure angle, and decreases with the increase of surface roughness.

The researches concern the influence of the helix angle on the composite machining process

Magnesium oxide-reinforced wood fiber composites (MgO/WF) are a new type of multifunctional material, which can be used in different occasions, such as shopping malls, hotels, and residential buildings. Referring to the relevant literature, there is no research on the milling performance of MgO/WF. In order to better understand the relevant knowledge of the processability of MgO/WF, three cutters with different helix angles were used in this experiment to carry out the cutting of MgO/WF, and the variation trend of its cutting force, tool wear, and surface roughness was measured. The results are as follows: First, under the same cutting parameters, the resultant force decreases with the increase of helix angle. Second, with the increase of helix angle, the tool wear was slightly improved. Third, the surface roughness (Ra) showed an increasing trend with the decrease of helix angle. In the end, when milling MgO/WF, better machined surface quality and less tool wear can be obtained by selecting the tool with larger helix angle.

Experimental Study on the Effect of Cutting Tool Geometry in Micro-Milling of Inconel 718

In this study, the effect of tool geometry on the cutting forces, surface roughness, and burr formation in the micro-milling process is investigated. Three different geometric parameters (helix angle, number of cutting edges, and axial rake angle) that may affect the machining performance are taken into account. Inconel 718 superalloy was used as workpiece material, and the tests were performed under dry cutting conditions. According to the results obtained, the minimum cutting forces were obtained at a helix angle of 45°. The increase in the helix angle causes the forces in the Fz direction to increase. For the new cutting tool, increasing number of cutting edges and axial rake angle has little effect on cutting forces. For the worn tool, the cutting forces are lower in the four-edges cutting tool, and the cutting forces obtained in the negative axial rake angle are also higher. The dominant damage types in the cutting tool are abrasive wear and chipping. Increased cutting distance causes the edge and corner radii of the tool to increase. As a result, cutting forces, surface roughness, and burr formation also increase. Generally, the maximum top-burr width is obtained on the up-milling side for the new cutting tool. Maximum top-burr width occurs on the down-milling side in the worn tools. Increasing helix angle causes burr width to increase. It has been determined that low number of cutting edge and negative rake angle cause smaller burr width.

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.

Heat transfer of nanofluid through helical minichannels with secondary branches

Heat transfer, fluid flow characteristics and entropy generation of water-Al2O3 nanofluid for cylindrical heat sinks with helical minichannels that have secondary branches are investigated experimentally. The minichannels helix angles are 45, 60 and 90 degrees; the volume fraction of nanoparticles variation is 0.05% – 0.1%; the Reynolds number range is between 113 to 478. The effects of the helix angle of minichannels, Reynolds number and nanoparticle volume fraction are studied. The heat transfer enhances with increasing Reynolds number, decreasing helix angle and increasing volume fraction of nanoparticles. However, with increasing Reynolds number, increasing helix angle and decreasing nanoparticles volume fraction, the friction factor decreases. The experimental results show that the secondary branches decreased the friction factor and Nusselt number. The maximum enhancement of Nusselt number in helix angle 60 and 45 for pure water are 31.1% and 51.3% greater in comparing with the straight minichannel, respectively; moreover, maximum enhancement of the Nusselt number of nanofluid compared with the pure water was about 14.3% for 0.1% vol. The thermal entropy generation rate decreases and, the frictional entropy generation rate increases with increasing the nanoparticles volume fraction and decreasing the helix angle. Furthermore, two new correlations are obtained for the Nusselt number and friction factor.

Performance of helical router bit in milling of composite boards

An extreme inclination angle of helical cutting tool edge has been developed in milling of new commercially composite boards. The purpose of this research was to investigate wear resistance, chip formation, surface roughness, and noise level of helical edge router bits in milling composite boards. The composite boards of wood plastic composite, laminated veneer lumber, and strand board were cut by the helical edge router bits (helical angle 15°, 30°, 45°, 60°, and 75°) in a computer numerical control router. The results show that the helical edges provide better wear resistance, smoother surface of machined composite boards, and lower noise emission compared to the conventional edge (0°). Edge wear, surface roughness, and noise level decreased with increasing helix angle of the edge router bits. The differences in structure among the composite boards resulted in the difference in cutting tool wear, chip formation, surface roughness, and noise level phenomenon. The 75° inclination angle of router bit provided the highest wear resistance, better surface of machined composite board, and the lowest noise level.

Mechanical properties of the grooved-wheel drilling particles under multivariate interaction influenced based on 3D printing and EDEM simulation

The grooved-wheel drilling device is one of the most widely used seeding and fertilizing equipment in developing countries. In the drilling process of the grooved wheel, the particles (fertilizers or seeds) are subject to great force which easily causes the particles broken or the grooved wheel stuck. Therefore, in this paper, the EDEM simulation software was used to analyze the velocity of and force on the particles in the drilling process, to obtain the maximum discharging velocity of and the force on the particles at different helix angles in the drilling process. With the 3D printing technology, a brand new grooved wheel was designed and produced. The response surface methodology was adopted to analysis of the influence of multiple factors on indicators in the grooved-wheel fertilizing process to build a multivariate regression model to obtain the best working parameters. The accuracy of the simulation and regression models was verified with fertilizer amount as an indicator. The simulation and experimental results show that in static and dynamic conditions, the force on the particles decreases first and then increases with the increase of helix angle. In static condition, discharging velocity of the particles increases first and then decrease with the increase of helix angle, followed by fluctuations in a small range. In dynamic condition, discharging velocity of the particles first decreases and then increases with the increase of helix angle, and finally fluctuates in a small range. The best parameters for fertilizing are as follows: groove radius of 13.5 mm, helix angle of 62°, rotational speed of 29.4r/min, tilt angle of fertilizer feeder of 5°, fertilizer amount of 17.810 g, and variation coefficient of fertilizer amount of 5.60%. The relative errors between the EDEM simulation and the regression model and the experiments are 0.90% and 3.55%, respectively. The simulation model and the regression model were built with practical engineering application value.

Characterizing Mist Distribution in Through-Tool Minimum Quantity Lubrication Drills

Abstract The mist distribution is a critical factor in through-tool minimum quantity lubrication (MQL) drilling since a small amount of lubricant is used. However, it has rarely been discussed because of the difficulty in measuring the mist flow experimentally. In this paper, an optical approach is developed to approximate the mist distribution by using high-speed images from multiple angles. Drill bits with two through-tool channel shapes (circle and triangle) and three helix angles (0 deg, 30 deg, and 45 deg) are 3D printed for mist distribution analysis. Furthermore, computational fluid dynamics (CFD) is conducted to investigate the underlying physics behind mist flow variations. The results show that, in the circular channel, the mist is concentrated near the periphery; the low concentration region shifts away from the chisel point as the helix angle increases. For the triangular channel, the mist is concentrated near three vertices but is less affected by the helix angle. Furthermore, based on the CFD solution, high mist concentration tends to be in low-velocity regions and vice versa. This study confirms a noticeable difference of mist flow distribution in different through-tool channel designs.

Effect of helical micro-fins on two-phase flow behavior of R410A evaporating in horizontal round tubes obtained through visualization

This paper presents a new approach in visualization of the evaporation mechanism and the two phase flow. The visualization test section is a transparent micro-fin tube made by 3D printing. The 3D printing technology helps reproduce the real geometry in commercial metal micro-fin tubes. Even though the wall material is different from the real metal, this new method provides a more complete understanding of the mechanisms of flow boiling and the heat transfer enhancement due to micro-fin geometry. To investigate the effect of micro-fin geometries on two-phase flow behavior, R410A flow boiling experiments are conducted at 10 °C saturation temperature and visualized through a clear smooth tube and micro-fin tubes of 0°, 10° and 18° helix angles. The results showed that the annular flow pattern in the helical micro-fin tube occurred at a lower vapor quality than the smooth and axial micro-fin tubes. Helix angle affects the transition boundary of stratified wavy flow to wavy annular flow, which shifts downward (to lower mass flux and vapor quality conditions) as the helix angle increases. Other transitions are not significantly affected by the helix angle. Helical micro-fin tubes with different groove directions were made to understand the flow behavior on the upward side and downward side of the tube.

Experimental and numerical study on swirlmeter with different helix angles of swirler

Swirlmeters are widely used to measure the flowrate in engineering due to its simple structure, stable operation stability, and accurate measuring precision. In this paper, in order to disclose the influence of different helix angles of swirler on the metering characteristics of the swirlmeter, the metrological performance and internal unsteady flow of a swirlmeter assembled with three swirlers with different helix angles were studied through physical experiments and numerical calculations. The results show that with the increasing helix angle of swirler, the pressure loss of swirlmeter and meter factor K decrease almost linearly, the vortex core center at throat of the swirlmeter is gradually off-center. In the direction of central axis of the throat, the amplitude of dominant frequency of pressure pulsation increases with the increasing helix angle of swirler.

Helical Extrusion Process of General Polygonal Section Shapes through Curved Dies

Practically, the helical products used as a mechanical part to satisfy the needs of mechanical strength and artistic appearance. In addition, during recent 5 years it used to produce an ultra-fine grain metal structure. However, there are very little works regarding this type of extrusion so far. This work proposed a new formulation for helical deformation zone to produce general helical polygonal shapes through a streamlined die that are usually made by hot extrusion through taper die. The general die surface was represented analytically. The velocity and strain rate fields are derived depending on the volume constancy and the velocity boundary conditions. The upper bound forming pressure was obtained for various frictional conditions, area reduction, helix angle, and die length. The results show that the axis of the product does not rotate through the helical extrusion. The peak value of the strain rate is located close to the die outlet and decreases as the helix angle increases. The optimum die length becomes high as the helix angle increases. The forming pressure increases with increasing helix angle, area reduction, factor of friction, while decreases when the number of sides increases. The theoretical results were verified with previous work of zero twist and showed completely compatible. A finite element solution was done using hardening material model to verify the analytical results and metal flow and to examine the strain and stress fields in the product.

Effect of helix angle on residual stress in the spiral welded oil pipelines: Experimental and finite element modeling

This paper studied the distribution of weld residual stress in a spiral welded pipeline by finite element method (FEM) and experimental measurements, and the effect of helix angle on residual stress has also been investigated. Both the FEM and experiment results show that the residual stresses in HAZ are larger than those in weld. The error between FEM and experiment results is within 14%, proving that our FEM is correct. There is a peak-shape stress distribution through the weld thickness and the residual stresses in the inner surface are larger than those in the outer surface. Different helix angle has a different equivalent weld length along the hoop and axial directions, which generates different hoop and axial plastic strains, leading to different hoop and axial residual stresses. As the increase of the helix angle, both the radial and hoop residual stresses decrease, while the axial residual stresses increase. As the helix angle increases from 20° to 50°, the hoop stresses in HAZ decrease by 65%, while the axial stresses increase by 120%. The residual stresses are influenced by the pipe dimension (pipe diameter, thickness, weld profile), welding technology (heat input, welding speed) and material grade. When the helix angle is between 40° and 45°, both the hoop and axial residual stresses are reduced to the minimum. The most suitable helix angle is suggested to design around 40°–45°.