Non-uniform Pitch Research Articles

Methodology of design and research of vibration stability of cylindrical milling cutters with non-uniform tooth inclination angle

The сalculation and construction of a structural scheme of a cylindrical milling cutter with different pitch and non-uniform angle of inclination of teeth, with increased vibration resistance, are considered. The dependence of the forced oscillation frequency of the milling cutter on the milling modes, pitch and inclination angle of the teeth is obtained, which makes it possible to study the vibration resistance of the milling cutter in comparison with a non-uniform pitch milling cutter with a constant inclination angle of the teeth. The "resistance" of the studied cutter to resonances arising during milling is shown. Keywords:cylindrical milling cutter, tooth inclination angle, resonance, milling mode Yakov_Liberman@List.ru, ovsiannikovavaleriya@mail.ru, Lubov202055@yandex.ru

Employing uniform and non-uniform inner twisted elliptical tubes in a double-pipe heat exchanger

Turbulent hydrothermal characteristics in a double-pipe heat exchanger with an internal twisted elliptical tube (TET) are investigated. The impacts of aspect ratio (AR = 1.4–2), uniform twist pitch (p = 100 mm-400 mm), and non-uniform twist pitch (five cases) on flow stream characteristics and heat transfer of parallel and counter-flows are investigated numerically. Utilizing a TET with a non-uniform twist pitch as an innovative approach yields noteworthy results, particularly in contrast to the traditional use of TETs with uniform twist pitch, owing to the longitudinal asymmetry. The outcomes depict that the pressure drop and heat transfer augment as the uniform twist pitch declines and the AR rises. The counter-flow has a more significant average Nusselt number than the parallel-flow by about 2–4 % without increasing the friction factor. Still, in some cases of non-uniform twist pitch, the average Nusselt number of the parallel flow is even 4 % higher than the counter-flow. The case with p = 100–200–400 mm (three parts with various twist pitches) and parallel-flow exhibits the most significant performance evaluation criterion (PEC) among the non-uniform twist pitch. As the aspect ratio increases from AR = 1.4 to AR = 2, the PEC factor in the counter-flow mode increases; however, there is an out-of-trend point at AR = 2 for the parallel-flow mode. The PEC factor augments about 8.47 % and 6.16 % for the counter-flow and the parallel-flow modes, respectively. The growth of TET twist pitch by 300 % reduces PEC by about 13.3 % in the counter-flow. The most significant PEC value is 1.166, which belongs to the case with the counter-flow condition and p = 100 mm.

Modeling of the unsteady aerodynamic force of turbine blades considering nonuniform vane pitch

Modeling of the unsteady aerodynamic force of turbine blades considering nonuniform vane pitch

Performance investigation and optimization of latent heat exchanger with pin fins based on non-uniform deployment strategy

Latent heat storage technology is an essential way of efficiently utilizing industrial residual heat, which helps to the objective of carbon neutrality in all countries. In this work, latent heat exchangers with pin fins are numerically investigated based on non-uniform deployment strategy and then optimized according to response surface method. The influences of rotation angle, non-uniform fin pitch, non-uniform fin length and combination of phase change materials with different melting temperatures on thermal storage performance are studied. Results show that the increment of rotation angle facilitates the reduction of complete melting time, and the optimal angle accelerates the melting speed by 10.3% compared to the 0° angle. The arrangements of gradually decreasing fin pitch and gradually increasing fin length along flow direction of heat transfer fluid improve the heat storage performance, which can reduce the complete melting time by 7.3% and 22.2% respectively, compared to the uniform arrangement. The multiple phase change materials latent heat exchanger with high melting temperature phase change material placed in high temperature region and low melting temperature phase change material in low temperature region can make better utilization of heat from heat transfer fluid, which can improve the melting speed by 16.8% compared with the single phase change material latent heat exchanger. The optimized latent heat exchanger based on response surface method reduces the complete melting time by 23.4% compared to the original model. In conclusion, the heat storage performance of latent heat exchanger with pin fins effectively improved by adopting the non-uniform deployment strategy.

Performance regulation of high-precision wireless passive yarn sensor based on normal mode helical dipole antenna

Stable and reliable sensing performance was required for high-precision wireless passive yarn sensor based on normal mode helical dipole antenna (NMHDA). The actual helical pitch of NMHDA was non-uniform due to manufacturing process, and the previous equivalent impedance model for uniform NMHDA, i.e., wire-loop model, was oversimplified, resulting in inaccurate predicted reactance and sensing performance of yarn sensor. This work combined the circular polarization principle and the asymmetric structure of non-uniform NMHDA to build the wire-loop-wire model. Based on the wire-loop-wire model, the parametric expression of NMHDA impedance and resonant frequency were obtained, and the results predicted by wire-loop model and wire-loop-wire model were compared with the measured one. Furthermore, to demonstrate the practicality of wire-loop-wire model and parametric resonant frequency expression, the impact of helical pitch uniformity on resonant frequency was discussed in terms of the statistical characteristics of prototype helical pitch, and also the parametric expression was applied to design wireless passive yarn sensors with expected working property. It was found that the wire-loop-wire model incorporating the asymmetric structure accurately described the impedance characteristics of the NMHDA with non-uniform helical pitches, and the maximum predicted deviation of resonant frequency was reduced to 1 MHz. The steady long reading range (19.42 ± 0.09 m) of wireless passive yarn sensors prototype demonstrated the capacity of wire-loop-wire model in designing high-precision sensor. Generally, this paper successfully built the wire-loop-wire model for NMHDA with non-uniform helical pitches, and provided a practical tool for designing e-textile devices with NMHDA.

A pre-correction method for oblique projection of grating fringes in a phase measuring profilometry system

In a phase measuring profilometry system, while the camera optical axis is perpendicular to the reference plane and the projector is installed obliquely, the sinusoidal characteristic of the grating fringes is lost (i.e., non-uniform pitch and amplitude), thus affecting the measurement accuracy. In this paper, a universal correction method for grating fringes is proposed, in the case where the projector optical axis is not perpendicular to the reference plane. This method includes pose correction (i.e., uniform pitch) and light intensity correction (i.e., uniform amplitude) of grating fringes. The pose transformation model, which is used to convert the pixel coordinates from the projector coordinates system into the camera coordinates system, is established by projecting a single image. Next, the digital grating fringes pattern with pre-corrected pose can be obtained, according to the established pose transformation model and the projector resolution. Regarding the light intensity correction, after capturing a projected blank pattern with pre-corrected pose, the light intensity correction coefficients on the reference plane are quantified by iteration method, and they can be used to correct the light intensity of grating fringes. The experimental results show that the presented method can effectively realize the sinusoidal correction of grating fringes.

The effect of non-uniform pitch length and spiraling pathway on the mechanical properties of coiled carbon nanotubes

Coiled carbon nanotubes (CCNTs) exhibit exceptional mechanical, electrical, and thermal properties, making them suitable for diverse applications such as nanoelectromechanical devices. Here, classic molecular dynamics (MD) simulations were employed to investigate the coil morphology and the uniaxial tensile characteristics of thirteen CCNTs that were constructed by twisting carbon nanotube (CNT) segments of toroid formed by six identical CNT segments, with intricate effects of coil spacing and twist-induced spiraling pathway. The MD results showed that the coil morphology and stretching properties of CCNTs are greatly dictated by pitch length and spiraling pathway. All CCNTs showed unique characteristics of sawtooth-like patterns in the tensile stress-strain curves, originating from the separation of van der Waals (vdW) attracted coils, strain-induced buckling of CNT segments and nanohinge-like plastic deformations. Depending on the non-uniform pitch length and spiraling pathway of twisted CCNT segments, CCNTs exhibit different mechanical properties including Young's modulus, elastic limit, tensile strength, fracture strain, stiffness coefficient and distinguishing deformation mechanisms. Particularly, the fracture strain and tensile strength are significantly dictated by the pitch length and spiraling pathway, respectively. The elastic proprieties of finite element (FE) models scaled to CCNTs were established for comparison with the case of CCNTs with symmetrical spiraling. Moreover, CCNTs show high toughness that can be controlled by the pitch length and spiraling pathway. This study provides new insights and perspectives into the mechanical properties of nanocoils, which is of help to designing optimal nanocoils for nano-device systems.

3D surface topography prediction in the five-axis milling of plexiglas and metal using cutters with non-uniform helix and pitch angles combining runout

3D surface topography prediction in the five-axis milling of plexiglas and metal using cutters with non-uniform helix and pitch angles combining runout

Crosstalk prediction and statistical properties of transmission line

In this paper, for the crosstalk error problem of multi-core stranded wires caused by non-uniform pitch, the Monte Carlo method is used to establish the probability distribution model of non-uniform pitch of stranded wires. For stranded wire crosstalk prediction, a transmission line pa-rameter prediction model is constructed using the BSO-BP neural network algorithm, and the effec-tiveness of the algorithm in this paper is verified by simulation. The final calculation gives the statis-tical characteristics of crosstalk on multicore stranded wires.

Non-Uniform Pitch Helical Resonators for Dual-Passband Filter Design

This paper presents a study of a non-uniform pitch helical resonator (NPHR) structure and the coupling mechanisms to design dual-passband filters. The previous research analyzes NPHR as a type of step impedance resonator (SIR), however, it does not give analytical equations or prediction for the dual-resonance characteristics of the NPHR structure discussed in this paper. Consequently, a circuit model is proposed to analyze the dual-resonance characteristics of NPHRs. Analytical equations are derived, showing that the frequency ratio of a dual-band NPHR can be determined by the ratio of turns. EM simulation and experimental results have shown good agreement with the circuit analysis. The derived analytical equations from circuit model can be used for fast design of NPHRs. A step-width aperture is proposed to independently control the coupling coefficients at the each band of NPHRs. A third order dual-passband filter has been designed and fabricated. The filter has 3.3% and 3% fractional bandwidths at 789 MHz and 2402 MHz, respectively. The designed prototype filter shows that NPHRs can be utilized to realize compact filters with dual-band characteristics. The filter design can be extended from engineering perspective for application in wireless communication systems.

Wide-steering-angle high-resolution optical phased array

Optical phased array (OPA) technology is considered a promising solution for solid-state beam steering to supersede the traditional mechanical beam steering. As a key component of the LIDAR system for long-range detection, OPAs featuring a wide steering angle and high resolution without beam aliasing are highly desired. However, a wide steering range requires a waveguide pitch less than half of the wavelength, which is easily subjected to cross talk. Besides, high resolution requires a large aperture, and it is normally achieved by a high count number of waveguides, which complicates the control system. To solve the mentioned issues, we design two high-performance 128-channel OPAs fabricated on a multilayered SiN-on-SOI platform. Attributed to the nonuniform antenna pitch, only 128 waveguides are used to achieve a 4 mm wide aperture. Besides, by virtue of innovative dual-level silicon nitride ( Si 3 N 4 ) waveguide grating antennas, the fishbone antenna OPA achieves a 100 ° × 19.4 ° field of view (FOV) with divergence of 0.021 ° × 0.029 ° , and the chain antenna OPA realizes a 140 ° × 19.23 ° FOV with divergence of 0.021 ° × 0.1 ° . To our best knowledge, 140° is the widest lateral steering range in two-dimensional OPA, and 0.029° is the smallest longitudinal divergence. Finally, we embed the OPA into a frequency-modulated continuous-wave system to achieve 100 m distance measurement. The reflected signal from 100 m distance is well detected with 26 dBm input transmitter power, which proves that OPA serves as a promising candidate for transceiving optical signal in a LIDAR system.

Crosstalk Prediction between Single Wire and Non-uniform Twisted-wire Pair

ABSTRACT Aiming at the crosstalk error of twisted-wire pair (TWP) caused by nonuniform pitch, this article innovatively uses Monte Carlo (MC) method to establish the probability distribution model of TWP with nonuniform pitch, and genetic algorithm-back propagation neural network is used to extract the unit length parameter of the transmission line. The chain parameter method is used to solve the multi-conductor transmission line equation based on the idea of cascade. Finally, the CST simulation results show that near-end and far-end crosstalk can be predicted effectively. In TWP modeling process, according to the probability distribution existing in the principle of stranding, the MC method is used to correct the probability distribution of the nonuniform pitch on TWP into a normal distribution.

Rapid stability analysis of serrated end mills using graphical-frequency domain methods

Serrated tools result in an irregular distribution of chip thickness and varying time delays along their flutes that disturb the regenerative chatter mechanism and maximize productivity in rough machining operations. The chatter stability simulation with such tools is complex due to the delay differential equations with multiple and distributed delays. Although the time domain numerical integration methods and the semi-discretization method are accurate, they are computationally expensive and hence inhibit the optimal design of serrated cutters. Despite the advantages that serrated tools offer, there has been little attention paid to rapidly predict stability lobes diagram for these tools to help instruct their optimal designs. To address this need, new graphical-frequency methods are presented to solve for stability of serrated tools with arbitrary geometry. The graphical method averages the number of teeth in cut to make the system time-invariant and results in a closed-form analytical solution. It reduces the simulation time by up to ∼99% compared to the semi-discretization method. Generalized solutions to the classical zero-order approximation and the multi-frequency methods are also presented by using the Nyquist stability criterion. The use of the zero-order approximation method and the multi-frequency method reduces simulation times by up to ∼97% and ∼79% respectively compared to the semi-discretization method. These are significant improvements over reports in the previous literature. Stability predictions are validated experimentally and benchmarked with high-fidelity time domain methods. The presented methods are general and can be applied to any end mill with non-uniform pitch and helix angles as well.

Harmonic Analyses of Periodic Milling Forces and Vibrations

The milling process is a materials processing method of economic importance. This work discusses and illustrates the application of harmonic analysis in the modeling of cutting forces and periodic vibrations of the milling process. The interest in periodic forces and vibrations of the milling process is motivated by the fact that they are always present because of the inevitability of structural flexibility, unlike the regenerative forces and vibrations, which can be avoided. However, they are more destructive when they occur. These vibrations leave machined parts with vibration marks and form error compromising geometrical integrity. There is a pressing need to minimize or pre-empt the costly remedial finishing processes through modeling and simulation of the problem. Illustrations are presented for a cutting tool with uniform pitches and a cutting tool with non-uniform pitches. Simulations indicate the need to avoid spindle speeds corresponding to tool passing frequency because they induce destructive resonant conditions in milling processes.

Miniaturized Dual-Resonant Helix/Spiral Antenna System at MHz-Band for FSK Impulse Radio Intrabody Communications

In this article, a miniaturized dual-resonant antenna system at MHz-band operating at around 20 and 50 MHz is proposed for frequency-shift keying impulse radio (FSK-IR) intrabody communications. This antenna system comprises a swallowable helix-coil in-body antenna with a hollow cylindrical shape of 10 mm diameter and 30 mm length, and two single band on-body matched planar spiral-coil antennas with a compact size of 79 mm $\times\,\,72$ mm $\times\,\,2.8$ mm. For in-body antenna design, a nonuniform helical pitch structure is utilized to produce dual-resonant frequencies. The soft ferrite magnetic sheet with high relative permeability and low dissipation factor is used as a flexible conformal substrate to realize antenna miniaturization without lumped element loading. Simulation results for antenna performance, electromagnetic field distribution, and specific absorption rate are presented with different tissue-type phantoms, as well as an anatomical numerical human model. In addition, experimental verification of antenna performance and implant transmission characteristics is also conducted in a liquid phantom. At an implant depth of 50 mm, the measured maximum transmission coefficients are −33 and −45 dB at the dual-resonant frequency bands, respectively. Simulation and measurement results demonstrate that the proposed dual-resonant antenna is suitable for the FSK-IR system and can be expected to realize a data rate as high as 10 Mb/s for biomedical implant applications at MHz-band.

Study on the stability for non-uniform helix angle tools in the milling process

ABSTRACT Uniform helix angle tools cannot effectively suppress the chatter in the high machining process. Consequently, cutters with non-uniform helix and pitch angles are more and more common in various milling operations. To suppress the regeneration chatter, it is crucial to study the stable behavior of the tools. Therefore, this paper considers the relationship between the pitch angle and the chatter stability defined by the regeneration factor (RF). Further, the governing equation of the machining system with non-uniform helix angle cutters is formulated. Based on this model, the Enhanced Multistage Homotopy Perturbation Method (EMHPM) is used to compute the stability lobes. To validate the theory in this paper, the stability lobes are predicted and compared with the results in the literature. The results show that the rational helix and pitch angle cutters exhibit increases stability in the milling process.

Investigation on Sensorless Estimating Method and Characteristics of Friction for Ball Screw System

In this study, a novel sensorless method is developed to estimate the friction in a ball screw system using asynchronous experimental data for a worktable position (WP) and the servo motor torque current (SMTC), which is collected by the FOCAS library functions from a FANUC digital control system. The corresponding time stamps are retrieved by a high-resolution performance counter in Windows. The fluctuations in friction over the whole travel distance of the worktable (WTDOW) are analyzed using a piecewise polynomial fitting algorithm to extract the instantaneous average friction value (IAFV) and the friction fluctuating signal (FFS). The IAFVs can describe the effect of the WP and the pitch errors of the shaft on the friction. The FFT results of the FFS show that the friction depends on the rolling tool, the pitch of the shaft and the refeeding of the balls in the ball screw and linear ball rail guides. The experimental results show that the estimated friction can capture the characteristic spectra of the FFS. The effects of the feed velocity and direction, the effects of the WP on the IAFV, and the frequencies and amplitudes of the significant FFT components are discussed. The nonuniform pitch errors of the shaft impact the repeatability of the IAFVs at a given WP. The variations in the mean value of the IAFVs with the feed velocity for tests at a fixed WP show nonconventional Stribeck behavior. These results also demonstrate that the friction force varies with the WP, which is not captured by Stribeck characteristics. This study provides an effective method to evaluate the performance of a ball screw system and to predict the friction in that system without the use of sensors.

An accurate instantaneous uncut chip thickness model combining runout effect in micro-milling using cutters with the non-uniform helix and pitch angles

As a key factor, the accuracy of the instantaneous undeformed thickness model determines the force-predicting precision and further affects workpiece machining precision in the micro-milling process. The runout with five parameters affects the machining process more significantly compared with macro-milling. Furthermore, modern industry uses cutters with non-uniform pitch and helix angles more and more common for their excellent properties. In this article, an instantaneous undeformed thickness model is presented regarding cutter runout, variable pitch, and helix angles in the micro-milling process. The cutter edge with the cutter runout effect is modeled. Then, the intersecting ellipse between the plane vertical to the spindle axis and the cutter surface which is a cylinder can be gained. Based on this, the points, which are used to remove the material, on the ellipse as well as cutter edges are calculated. The true trochoid trajectory for each cutting point along the tool path is built. Finally, the instantaneous undeformed thickness values are computed using a numerical algorithm. In addition, this article analyzes runout parameters’ effects on the instantaneous undeformed thickness values. After that, helix and pitch angles’ effects on the instantaneous undeformed thickness are studied. Ultimately, the last section verifies the correctness and validity of the instantaneous undeformed thickness model based on the experiment conducted in the literature.

Fabrication of integrated spectrometer module based on optical waveguide platform with planar nano diffraction grating using UV imprint lithography

We proposed a simple and attractive integrated polymeric spectrometer module based on a planar optical waveguide platform that can be easily manufactured at a low cost. The proposed integrated spectrometer module comprises a planar optical waveguide with a concave mirror, a planar nano diffraction grating with a non-uniform pitch, an optical fiber, and a photodiode array. The nano diffraction grating and optical waveguide platform were precisely fabricated using the UV imprint lithography suitable for mass production. To provide uniform diffraction efficiency in the wavelength range of 400–650 nm, the nano diffraction grating had a quasi-three-dimensional V-shaped groove with a blazing angle of 22.5° and non-uniform pitches, maximum of 0.406 μm and minimum of 0.393 μm. In addition, the optical waveguide platform focuses the optical source to the nano diffraction grating using the concave mirror. The alignment guide pattern is used to align the nano diffraction grating and optical fiber. Through the packaging process of nano grating device, photo diode array and fiber on the planar optical waveguide platform, we manufactured the polymeric integrated polymeric spectrometer module. We confirmed that the fabricated planar spectrometer module had a resolution of 5 nm or less for spectral bandwidth of 250 nm, and it can be used widely in portable spectrometer sensors.

Nonuniform sampling pitch acquisition method in myocardial single-photon emission computed tomography.

Single-photon emission computed tomography is a tomographic imaging method that acquires a projection image by rotating a gamma camera around by 380° or 180°. For myocardial single-photon emission computed tomography, 180° acquisition is common, but it has limitations including an incomplete reconstruction, which can distort the resulting image. It is possible to produce a complete reconstruction using 360° acquisition, but the testing time is long and is burdensome to patients. The nonuniform sampling pitch acquisition (NUSPA) method devised in this study involves reducing the total sampling count using NUSPA that reduces the sampling pitch in the range in which the gamma cameras are closer to the myocardium (RAO45-LPO45) and increases it elsewhere. The NUSPA-1 method based on a 6° sampling pitch had 20 views fewer than 360° acquisition. In addition, the NUSPA-2 method based on a 3.75° sampling pitch had 60 views fewer than 360° acquisition, considerably reducing the testing time. The acquired sinograms from the NUSPA methods were subjected to nonuniform rational B-spline surface interpolation processing, producing data with a uniform sampling pitch, after which image reconstruction was performed. The images after nonuniform rational B-spline interpolation for both the line sources and heart-liver phantom investigated in this study were not found to have the distortion observed from 180° acquisition or a count decrease at the center, resulting in image quality nearly equivalent to 360° acquisition. This method enabled a reduction in testing time without impacting image quality.