Milling force is a parameter affecting wood processing quality, tool life, and energy consumption, and its variation is influenced by the multi-factor coupling of cutting parameters and tool geometric factors. This study systematically investigates milling forces during the processing of pine wood (Pinus sylvestris var. mongholica Litv.) using a hybrid modeling approach combining principal component analysis (PCA) and multiple linear regression (MLR). Firstly, PCA was employed to reduce the dimensionality of the tool rake angle (γ), helix angle (λ), cutting depth (h), feed per tooth (Uz), and triaxial milling forces (Fx, Fy, Fz); this eliminated the multicollinearity among variables and extracted the integrated features. Subsequently, an MLR model was constructed using the principal components as independent variables to quantitatively evaluate the contribution of each factor to milling forces. The results support the conclusion that PCA successfully extracted the first four principal components (cumulative variance contribution rate: 92.78%), with PC1 (49.16%) characterizing the comprehensive milling force effect and PC2 (15.03%) primarily reflecting the characteristics of the tool geometric parameters. The established MLR model demonstrated a high significance (R2: Fx = 0.915, Fy = 0.907, Fz = 0.852). The cutting depth exerted a significant positive driving effect on the triaxial milling forces via PC1 (each 1 mm increase in depth increased the PC1 score by 0.64 units, resulting in increases of 27.2%, 26.6%, and 21.8% for Fx, Fy, and Fz, respectively). The helix angle significantly suppressed Fy through PC2 (β = −0.090, p < 0.001), whereas the rake angle exhibited a weak negative effect on Fx via PC3 (β = −0.015). Parameter optimization identified the combination γ = 25°, λ = 30°, h = 0.5 mm, and Uz = 0.1 mm∙z−1 as optimal, which reduced the triaxial milling forces by 62.3% compared to the experimental maximum. This study provides a theoretical foundation and novel parameter optimization strategy for the efficient, low-damage processing of wood materials.

Cardiac Diffusion Tensor Imaging May Detect Early Cardiac Amyloidosis in Carpal Tunnel Syndrome

Dynamic model of ultrasonic assisted milling for aluminum alloy with Variable helix angle milling cutter and chatter suppression

The Wind Wall is a symmetric multi-VAWT system designed for efficient wind energy harvesting using Ugrinsky-type blades that are arranged in a compact, geometrically balanced layout to improve flow uniformity and torque stability and reduce pulsating loads. This study uses CFD simulations to determine the optimal helix angle and turbine spacing by analyzing the aerodynamic moment coefficient (Cm), effective velocity (Ve), and corresponding pressure-induced torque trends for stationary turbine configurations and proposes a simplified correlation linking Ve, turbine diameter, and spacing. The results show that a helix angle of 20–30° and symmetric spacing yield the highest performance, with the optimal angle increasing the time-averaged Cm by approximately 831% compared to the closest-packed case. These findings address the critical impact of improper spacing and sub-optimal twist angles in compact multi-turbine systems and provide the first combined CFD-based assessment of the helix angle and spacing for a symmetric Ugrinsky-blade Wind Wall, contributing a practical spacing–velocity relationship for future design and deployment.

To meet the demands of helicopter transmission systems characterized by diverse configurations and high-speed, heavy-load operating conditions, the meshing characteristics of helical face gears integrated non-orthogonal, offset, and profile-shifted were studied. Geometric contact and load contact analysis models suitable for such non-orthogonal, offset, and profile-shifted helical face gears were established. Combined with Blok’s flash temperature formula, a tooth surface flash temperature analysis model was developed. The influences of installation errors, offset distance, profile-shifted coefficient, and helix angle on the meshing characteristics of the tooth surface were analyzed. The results show that among installation errors, the shaft angle error is the most sensitive. As the offset distance increases, the tooth surface contact stress decreases, while the root bending stresses of both gears initially increase and then decrease. When the profile-shifted coefficient increases, the root bending stress of the profile-shifted pinion decreases, whereas that of the INOPS helical face gear increases. Increasing the helix angle reduces both the tooth surface contact stress and the root bending stress of the profile-shifted pinion, but increases the root bending stress of the INOPS helical face gear. The flash temperature exhibits an increasing trend with distance along the meshing line and is significantly affected by the profile-shifted coefficient and the offset distance.

Abstract CW511L lead-free brass is a newly developed alloy that has found widespread application across various industrial sectors. It is particularly preferred as a raw material for watering and pumping components, which typically require machining before use. This study investigates the influence of cutting tool geometry on drilling performance, focusing on critical parameters such as radial rake angles, axial rake angles, tip radius, and helix angle. An L27 Taguchi experimental design was employed using the following levels: radial rake angle (4°, 8°, 12°), axial rake angle (−2°, 0°, 2°), tip radius (10, 20, 30 µm), and helix angle (0°, 5°, 10°). Drilling experiments were performed in accordance with this design to evaluate cutting forces, chip breakability, burr height, and surface quality. The effects of tool geometry were analyzed using three-dimensional surface plots and a correlation matrix to reveal significant relationships between input variables and drilling responses.

ABSTRACTPurposeCardiac diffusion tensor imaging (cDTI) is signal‐to‐noise ratio (SNR)‐limited due to diffusion signal attenuation, long echo times from gradient moment nulling, and moderate myocardial T. Increasing voxel volume improves SNR but reduces spatial sensitivity and introduces physiological bias. This work aimed to identify the voxel configuration (volume and shape) yielding the most precise cDTI metrics.MethodsSpin‐echo cDTI protocols spanning nine voxel volumes were evaluated in healthy subjects (N = 11) at 3T. A gel phantom was scanned to compare SNR in a non‐physiologic environment. Temporal SNR and regression fits were computed. Mean diffusivity (MD), fractional anisotropy (FA), bootstrapped uncertainties (dMD, dFA), Helix angle pitch (HAP), and the primary eigenvector's uncertainty (de→1) were then calculated, and significant (p<0.05) differences were assessed. Technique for order preference by similarity to ideal solution (TOPSIS) ranked configurations by uncertainties.ResultsPhantom SNR trends corresponded to theory, with consistent SNR increases. In vivo SNR increases differed between in‐plane resolutions, in which 2×2 mm in‐plane resolutions had the steepest slope. Higher in‐plane resolutions (2×2 mm) yielded lower MD than lower resolutions (3×3 mm). Higher in‐plane resolutions with thicker slices produced higher FA (2×2×8 mm). HAP was steepest at moderate voxel sizes (2.5×2.5×5 mm). All uncertainties decreased with 8 mm slices. TOPSIS ranked 2.5×2.5×8 mm highest (0.91), then 2.0×2.0×8 (0.83).ConclusionIn vivo differences in SNR slopes suggest a physiological bias‐dominated environment. The 2.5×2.5×8 mm voxel configuration had the lowest uncertainties (highest TOPSIS score), followed by 2.0×2.0×8 mm. This work provides a framework for evaluating the best cDTI voxel configuration.

Translational Insights Into Myocardial Deformation and Fibrosis in Hypertrophic Cardiomyopathy Using Diffusion Tensor MRI

Tool geometry assessment is essential in machining processes to ensure the accuracy of manufactured parts. Tool presetters such as laser beam interruption systems and camera-based systems are optical systems used to determine the tool geometry and are considered a prerequisite for machining operations. Tool geometry can be measured both on- and off-machine; however, on-machine tool presetting is preferred as the interfaces between the tool holder and the machine tool spindle can introduce unquantified clamping errors that affect the precision of machining processes. In this work, we compare the effect of high angular resolution on the performance evaluation of a camera-based tool presetting optical system for on-machine measurement of ball end mills. The validation process follows the guidelines stated in ISO 15530 part 3 and is established using a calibrated artefact which resembles a ball end mill (without the helix angle), whilst the reference measurements are performed using a coordinate measurement machine, and the task-specific uncertainty is determined. Experimental results have shown that the tool geometry measurement process (tool radius, runout) performs better when using the high angular resolution of the camera-based tool presetting system.

Micro-drilling in ballpoint pen tip production faces persistent challenges of tool wear and premature breakage, which limit manufacturing efficiency and dimensional accuracy. In this study, an integrated framework combining finite element simulation (FEM) and orthogonal experimental design was developed to optimize the geometry of micro twist drills. A three-dimensional FEM model was established in Deform‑3D to analyze the effects of apex angle, helix angle, chisel edge length, and chisel edge angle on cutting force and torque. Range analysis of the orthogonal design revealed that chisel edge length and apex angle were the most influential parameters. The optimal configuration (b = 0.05 mm, 2Φ = 135°, Ψ = 76.5°, β = 3°) reduced average torque by 22.2% and extended tool life by 43.9% compared with the original design, while maintaining hole dimensional accuracy within ± 0.01 mm. These results confirm FEM as a reliable predictive tool and demonstrate that the proposed FEM–orthogonal framework provides a structured and cost-effective strategy for micro-tool geometry optimization, with direct industrial applicability to precision manufacturing of ballpoint pen tips.

The Discrete Element Method (DEM) has become a cornerstone for analysing granular flow and mixing phenomena in static mixers. This review provides a comprehensive synthesis that distinguishes it from previous studies by: (i) covering a broad range of static mixer geometries, including Kenics, SMX, and Sulzer designs; (ii) integrating experimental validation methods, such as particle tracking, high-speed imaging, Particle Image Velocimetry (PIV), and X-ray tomography, to assess DEM predictions; and (iii) systematically analyzing computational strategies, including advanced contact models, hybrid DEM-CFD/FEM frameworks, machine learning surrogates, and GPU-accelerated simulations. Recent advances in contact mechanics—such as improved cohesion, rolling resistance, and nonspherical particle modelling—have enhanced simulation realism, while adaptive time-stepping and coarse-graining improve computational efficiency. DEM studies have revealed several non-obvious relationships between mixer geometry and particle dynamics. Variations in blade pitch, helix angle, and element arrangement significantly affect local velocity fields, mixing uniformity, and energy dissipation. Alternating left–right element orientations promote cross-sectional particle exchange and reduce stagnant regions, whereas higher pitch angles enhance axial transport but can weaken radial mixing. Particle–wall friction and surface roughness strongly govern shear layer formation and segregation intensity, demonstrating the need for geometry-specific optimization. Comparative analyses elucidate how particle–wall interactions and channel structure influence segregation, residence time, and energy dissipation. The review also identifies current limitations, highlights validation and scale-up challenges, and outlines key directions for developing faster, more physically grounded DEM models, providing practical guidance for industrial mixer design and optimization.

Abstract Due to their lightweight, high strength, and excellent corrosion resistance, aluminum alloys are widely used in many industries. Focusing on the geometric angles of tungsten steel milling cutters, this study employed common end milling cutters to simulate the machining of aluminum alloys and determine the optimal tool geometry angles. The Taguchi experimental method and the finite element analysis software DEFORM™ 3D were used for simulation analysis. Key geometric parameters affecting tool performance, such as helix angle, radial cutting angle, axial cutting angle, and other related angles, were identified. To evaluate the tool geometry results, this study examined tool geometry setup angles and tool wear, based on which quality characteristics were assessed. The optimal combination of tool geometry angles was effectively identified, and the ideal signal-to-noise (S/N) ratio was predicted. The simulation can be replicated using the predicted ideal values.

Abstract. Existing research on tooth surface wear of helical gears has insufficiently considered the complex and variable lubrication conditions between meshing tooth surfaces. This study constructed a mixed elastohydrodynamic lubrication (EHL) model based on the meshing characteristics of helical gears, analyzed the lubrication characteristics between the meshing tooth surfaces and the temperature changes induced by asperity contact and oil film shear, and introduced them into the improved Archard wear model to construct the surface wear calculation model under the mixed EHL conditions. Taking the changes in meshing characteristics of tooth profile during the tooth surface wear accumulation process as a connecting bridge, the mutual influence relationships among the tooth surface wear, lubrication characteristics, and tooth surface temperature rise were systematically clarified. The cumulative distribution law of tooth surface wear and the influence of tooth surface roughness, working conditions, and tooth profile parameters on the tooth surface wear depth were explored. The research indicates that the wear depth at the tooth root and top is deeper than that at the pitch position, the pinion's surface wear depth is greater than that of the gear, and the maximum wear appears at the pinion's tooth root. The wear depth under mixed EHL conditions is nearly 4 orders of magnitude lower than that under dry friction conditions. Reducing the magnitude of tooth surface roughness can effectively decrease the tooth surface wear depth. Appropriately increasing the velocity, module, tooth width, helix angle and tooth surface hardness is beneficial to improving the anti-wear ability of tooth surfaces. This study can provide a reliable theoretical basis for predicting and optimizing the tooth surface wear of helical gears under complex lubrication conditions.

With the frequent occurrence of stuck pipe incidents during the ultra-deep well drilling operation, the hydraulic-while-drilling (HWD) jar has become a critical component of the bottom hole assembly (BHA). However, during jarring operations for stuck pipe release, the drill string experiences severe vibrations induced by the impact loads from the jar, which significantly alter the stress state and dynamic response of the threaded connections—the structurally weakest elements—under cyclic dynamic loading, often leading to fracture failures. here, a thread failure incident of a hydraulic jar in an ultra-deep well in the Tarim Basin, Xinjiang, is investigated. A drill string dynamic impact model incorporating the actual three-dimensional wellbore trajectory is established to capture the time-history characteristics of multi-axial loads at the threaded connection during up and down jarring. Meanwhile, a three-dimensional finite element model of a double-shouldered threaded connection with helix angle is developed, and the stress distribution of the joint thread is analyzed on the boundary condition acquired from the time-history characteristics of multi-axial loads. Numerical results indicate that the axial compression induces local bending of the drill string during down jarring, resulting in significantly greater bending moment fluctuations than in up jarring and a correspondingly higher amplitude of circumferential acceleration at the thread location. Among all thread positions, the first thread root at the pin end consistently experiences the highest average stress and stress variation, rendering it most susceptible to fatigue failure. This study provides theoretical and practical insights for optimizing drill string design and enhancing the reliability of threaded connections in deep and ultra-deep well drilling.

Hybrid ball bearings with rolling elements made of silicon nitride show important friction, temperature, and power loss benefits compared to full steel bearings under mixed lubrication. This is of particular interest for electrical vehicle (EV) range extension in the automotive industry, where hybrid bearings are used in the electric motor with integrated gearbox to avoid electrical erosion damage. Same benefits can be obtained for industrial electric motors with high frequency variable speed drives where the hybrid bearing acts as an insulator against electrical currents. In this study bearing temperatures and system torque are measured in a modified FZG gearbox for both hybrid and steel ball bearings. The gear set was designed with a small helix angle to create an axial preload to the sets of 6306 deep groove ball bearings with C3 clearance. To reach mixed lubrication conditions, a small amount of low viscous oil was used operating at high temperatures up to a maximum of 100°C. Results in this study show that for mixed lubrication the hybrid bearings run 2-4°C cooler compared to steel ones, while the temperature gradient is similar. Due to lower friction in the hybrid bearings, the FZG test box efficiency is on average improved with 3%.

This study aims to address the problem that traditional helical gears generate significant axial forces during transmission and innovatively proposes a design scheme of double helical face gears (DHFG). An accurate mathematical model of the tooth surface is established using spatial meshing theory and coordinate transformation. A systematic investigation using the orthogonal test method is then conducted to analyze the influence of key parameters, such as the pinion tooth number, transmission ratio, and helix angle, on gear performance. The finite element analysis results show that the overlap degree of this double helical tooth surface gear pair in actual transmission can reach 2–3, demonstrating excellent transmission smoothness. More importantly, its unique symmetrical tooth surface structure successfully achieves the self-balancing effect of axial force. Simulation verification shows that the axial force is reduced by approximately 70% compared to traditional helical tooth surface gears, significantly reducing the load on the bearing. Finally, the prototype gear is successfully trial-produced through a five-axis machining center. Experimental tests confirmed that the contact impressions are highly consistent with the simulation results, verifying the feasibility of the design theory and manufacturing process.

Cutting force modeling of the Gradient Helix Edge end mill based on Helix Angle Differentiation

As a core component of high-speed trains, the traction drive system is also one of the main sources of both pass-by noise and interior noise. Current research primarily focuses on the modeling and design of its dynamic characteristics, while studies on its sound radiation remain relatively scarce. Existing investigations mainly rely on experimental and finite element methods. This paper proposes a rapid modeling method for the sound radiation of traction drive systems and analyzes the acoustic characteristics under different train speeds and gear helix angles. Taking an electric freight locomotive operating on China’s railways as the subject, the primary noise sources were identified through real-vehicle testing, thereby simplifying the non-dominant noise sources. By integrating a gear system dynamic model with theoretical models of gear meshing noise and motor noise, the proposed approach avoids the complexity and high computational cost associated with traditional finite element methods. The results show that at lower train speeds, the main noise source is the motor, while at higher speeds, it is the gearbox. As the train speed and helix angle increase, the radiated sound pressure of the traction drive system first increases and then decreases, though the sound field distribution and directivity remain largely unchanged.

Cardiac diffusion tensor imaging (cDTI) is susceptible to image distortion while using an echo planar imaging (EPI) readouts. FSL TOPUP and TORTOISE DR-BUDDI are image distortion correction techniques that have been implemented to correct EPI distortion in neurological applications. We sought to establish which EPI-based distortion correction technique is most suitable for cDTI. Using a free-breathing second-order moment-compensated spin-echo technique, cDTI was acquired in healthy volunteers (N = 10) using both blip-up (BU) and blip-down (BD) EPI readouts. These datasets were then distortion corrected using the TOPUP and DR-BUDDI software packages. BU, BD, TOPUP, and DR-BUDDI images were then characterized by (1) geometric fidelity using the Dice Similarity coefficient (DSC), epicardial average Hausdorff distance (AHD ), and endocardial average Hausdorff distance (AHD ); (2) quantitative parametric maps: mean diffusivity (MD), fractional anisotropy (FA), and helix angle pitch (HAP); and (3) 95% confidence intervals in uncertainty measurements for MD ( ), FA ( ), and the primary eigenvector ( ). Distortion correction displayed improved geometric fidelity for both median DSC (BU = 0.77, BD = 0.81, DR-BUDDI = 0.85, and TOPUP = 0.86) and median AHD (BU = 2.19 mm, BD = 1.94 mm, DR-BUDDI = 1.46 mm, and TOPUP = 1.33 mm). Decreases in median FA were observed for distortion correction data (BU = 0.30, BD = 0.28, DR-BUDDI = 0.27, and TOPUP = 0.26), while median MD fell between conventional BU and BD encoding (BU = 1.58 μm2/ms, BD = 1.70 μm2/ms, DR-BUDDI = 1.65 μm2/ms, and TOPUP = 1.64 μm2/ms). There was little to no change in median HAP between distorted and distortion-corrected data (BU = -0.41, BD = -0.40, DR-BUDDI = -0.41, and TOPUP = -0.36). Distortion correction increased the median for (BU = 0.32, BD = 0.32, DR-BUDDI = 0.36, and TOPUP = 0.41), (BU = 0.18, BD = 0.17, DR-BUDDI = 0.24, and TOPUP = 0.23), and (BU = 22°, BD = 22°, DR-BUDDI = 44°, and TOPUP = 41°). EPI distortion correction techniques improved geometrical characterization (DSC and ), but decreased precision in measuring uncertainty ( , , and ) when compared to conventional (distorted) BU and BD acquisitions. When comparing the two distortion correction techniques, TOPUP provides improved results for cDTI applications.

Abstract In recent years, the continuous breakthrough of high magnetic field records has imposed increasingly stringent requirements on high-temperature superconducting (HTS) cables for the preparation of magnets, particularly regarding cooling efficiency, bending flexibility, and mechanical strength. To address these challenges, novel CORC cable designs featuring advanced core structures-including conductor-on-round-tube (CORT) and conductor-on-spiral-tube (HFRC)-have been developed. Although these designs enhance cooling efficiency and cable flexibility through modifications to the core structure, their impact on mechanical performance has not yet been thoroughly characterized. This paper systematically investigates the mechanical behavior of CORC cables with diverse core structures under axial tensile, torsion, and bending loads through a combination of theoretical analysis, FE simulation, and experimental validation. The research proposes optimization strategies focusing on two key aspects: (1) the winding parameters of HTS tapes, and (2) the geometric configuration of the core structure. Theoretical analyses demonstrate that variations in HTS tape winding angle and core radius significantly affect the axial strain in the tapes. The FE model evaluates three critical parameters: core outer radius, inner-toouter radius ratio, and helix angle of the spiral tube core. The numerical results indicate that the ratio between the inner and outer radii of the winding core should be maintained below 0.7, considering both the axial strain distribution of the HTS tapes and the deformation of the cable. Furthermore, the influence of the spiral tube core's helix angle on cable performance is strongly dependent on the applied mechanical load. These findings offer both theoretical insights and practical guidelines for the design, fabrication, and engineering implementation of HTS CORC cables.