Browse Topic: Parts and Components

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Modeling and Analysis of Mechanical-Electrical Coupling in Flywheel Systems Considering Faults2026-99-292310/19/2026
Spacecraft flywheel systems are critical actuators for attitude control and stability maintenance, and their operating reliability is strongly affected by the health state of the supporting bearings. When local defects occur on the bearing raceway or rolling elements, the rolling contact state changes abruptly, which leads to time varying contact deformation, fluctuating support reaction force, and additional rotational resistance. Unlike many ground based rotating machines, spacecraft flywheel systems usually operate in compact and highly integrated configurations, where direct vibration measurement is difficult in practice. In contrast, motor current, voltage, and speed signals are easier to acquire and are therefore more suitable for condition monitoring. To describe how bearing defects propagate from the mechanical domain to electrical responses, a simplified electromechanical coupling model is developed for a flywheel rotor motor system with local bearing defects. First, a rolling element contact model is established using the defect induced deformation relation and Hertzian contact theory to derive the time varying bearing support force. Second, the fluctuating support force is mapped to an equivalent time varying load torque to represent the dominant pathway through which bearing defects influence the motor side. Third, the derived load torque disturbance is coupled with the transverse rotor dynamic equations, the rotational motion equation, and the motor dq axis model to obtain a simplified electromechanical coupling equation set. The proposed model preserves the main physical transmission chain from bearing defect to electrical response. The model provides a clear theoretical basis for analyzing fault propagation mechanisms and for developing current based diagnostic methods for spacecraft flywheel systems.
Wu, Haolong, Li, Yuqing
A Multi-Platform Bearing-Only Localization Method Based on Confidence Interval and Error Compression Iteration2026-99-294610/19/2026
Due to the fact that passive underwater acoustic signals can usually only obtain the bearing information of the target and are subject to complex ocean environmental interference, which poses significant obstacles to target localization using a single platform, this study intends to employ multiple unmanned underwater vehicles for cooperative localization of underwater targets. To address the issues of systematic bias in bearing measurements, high nonlinearity, and unknown target motion states in complex underwater acoustic environments, this paper proposes a bearing-only localization method based on confidence interval and error compression iteration. The unknown motion process of the target is mapped into a region expansion process in space, and the cooperative localization of multiple platforms is used to finely compress the regional error, achieving bearing-only localization of underwater targets through gradual region compression. The core idea of the proposed method is to map the unknown motion state of the target into an expansion process of an uncertainty region. First, bearing-only measurements obtained by multiple platforms at different time instants are used to construct sector regions with systematic bias. Then, a likelihood function is employed to update the probability distribution over the spatial grid, enabling iterative error compression. Meanwhile, the 95% highest posterior density interval is introduced as the statistical output of the localization results. Simulation experiments were conducted under three different initial scenarios. The results show that, with bounded bearing measurement errors, the proposed method can compress the area of the 95% HPD region from approximately 107 m2 to the order of 104 m2 within 120 seconds, while the localization error converges from several kilometers to less than 40 meters.
Huang, Fengfeng, Wang, Yuxuan, She, Tao
Fault Diagnosis Study of MCSECNN Model Integrating MK-MMD and DANN under Variable Operating Conditions2026-99-297210/19/2026
Bearing signals measured under different loads rarely keep the same waveform characteristics. Their amplitudes, spectral components, and statistical properties may change at the same time, which makes a classifier trained on one load condition less reliable on another. This study investigates a cross-load diagnosis method that trains a multi-scale convolutional squeeze-excitation network (MCSECNN) with multi-kernel maximum mean discrepancy (MK-MMD) and a domain-adversarial neural network (DANN). The convolutional branch captures vibration patterns over several temporal ranges, and the SE unit adjusts the importance of the channels generated by the parallel kernels. MK-MMD penalizes the distance between load-dependent feature distributions, whereas DANN weakens the load identity retained in the features. Tests using CWRU bearing data show that the integrated model gives better accuracy than the basic MCSECNN and the two single-adaptation variants. Ablation results indicate that the statistical and adversarial constraints contribute to transfer performance in different ways.
Ming, Mei, Ai, Yumei, Li, Shengnan, Wan, Haozheng, Sang, Shentian, Zhang, Haifeng
Research on Nonlinearity of Interface ASIC for MEMS Accelerometer with Switched-Capacitor Closed-Loop Feedback2026-99-296910/19/2026
This paper investigates the nonlinearity issues in the interface ASIC system for capacitive MEMS accelerometers. First, the sources of nonlinearity in the mechanical structure of the accelerometer and the switched-capacitor interface circuit are analyzed, including the nonlinearity of mechanical displacement-to-capacitance conversion, harmonic distortion caused by parasitic capacitance, and the contradiction between range and linearity due to a low-stiffness proof mass in open-loop mode. To suppress the nonlinearity, PID control is adopted to realize closed-loop electrostatic force feedback, a loop error model is established, and a capacitor array compensation circuit is introduced to eliminate the output offset caused by parasitic capacitance. The interface ASIC is designed in a 0.18 μm BCD process, and the layout design and tape-out are completed. Pre-simulation results show a nonlinearity of 0.0124% within a 0–50 g range; post-simulation nonlinearity is 0.0657%. In actual tests, the accelerometer achieves a scale factor of 0.091 V/g over the 0–50 g range, the maximum residual of the least-squares fitting is 0.000645 V, and the nonlinearity is 0.0728%, approximately 160 ppm. This study verifies the effectiveness of closed-loop PID control and capacitance compensation in suppressing nonlinearity, providing a theoretical basis and engineering reference for the design of high-linearity MEMS accelerometers.
Gao, Zhi, Li, Zhaohan, Hao, Zhiwen, Liu, Guowen, Gao, Naikun, Zhang, Wenbo, Fu, Qiang, Yin, Liang
An Integrated Fault Diagnosis and Prediction Method for Planetary Gears Based on Ensemble Learning2026-99-294410/19/2026
Planetary gears are key transmission components in spacecraft drive systems and are prone to failures under long-term operation in harsh environments. To address the problem that fault diagnosis and life prediction are treated separately in existing research, this paper proposes an integrated diagnosis-prediction method. First, order tracking and time synchronous averaging are used to preprocess vibration signals, eliminating speed fluctuations and noise interference. Then, fault features are extracted via VMD/EEMD decomposition, and the gear health condition is identified through a deep convolutional neural network. Finally, ensemble learning prediction models are established separately for different fault states to realize life prediction. Experimental results show that the VMD+CNN method achieves higher diagnostic accuracy than traditional methods for gears in healthy, cracked, spalled, and pitted conditions. The ensemble prediction models matched with different states can further reduce the life prediction error. This method provides effective technical support for condition-based maintenance of spacecraft planetary gears.
Liu, Yanyan, Gao, Tongxin, Zhu, Yangsong
BEARING, BALL, AIRFRAME, ANTIFRICTION, SELF-ALIGNING, DOUBLE ROW, HEAVY DUTYAS27643E (Current)10/9/2026
ACBG Rolling Element Bearing Committee
PIN, FEMALE COUPLINGAS7365/1A (Current)10/9/2026
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, CLOSE TOLERANCE SHANK UNS S66286, 130 KSI MIN, .2500-28 UNJF-3AAS91111E (Current)10/9/2026
E-25 General Standards for Aerospace and Propulsion Systems
ADAPTER, ASSEMBLY - PORT CONNECTION RING LOCKED TO 60° FLARELESS TUBE END, METRICMA2119C (Current)10/2/2026
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
BEARING, BALL, AIRFRAME ANTIFRICTION, PULLEYAS21443D (Current)10/2/2026
ACBG Rolling Element Bearing Committee
FITTING END, INTEGRAL WELD, LIP, DESIGN STANDARDAS1579E (Current)10/2/2026
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
Screw Threads - UNJ Profile, Inch, Controlled Radius Root with Increased Minor DiameterAS8879E (Current)9/25/2026
This SAE Aerospace Standard (AS) specifies the characteristics of screw threads - UNJ profile, inch, series, including a mandatory controlled radius as specified in Table 1 at the root of the external thread. The minor diameter of both external and internal threads provides a basic thread height of .5625H to accommodate the external thread maximum root radius. The following detailed design requirements are included: Screw threads - UNJ basic profile and design profiles. Standard series of diameter-pitch combinations for nominal thread diameters from 0.060 to 6.000 inches. Standard thread classes and form tolerances. Formulae for thread dimensions and tolerances. Method of designating UNJ threads. Tables for selected diameter-pitch combinations for close tolerance mechanical thread applications. Tables for screw thread - UNJ profile thread limit dimensions.
E-25 General Standards for Aerospace and Propulsion Systems
WASHER, FLARED TUBE FITTING ADJUSTABLE END, DEFINITION AND INSTALLATIONAS4324B (Current)9/25/2026
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, DRILLED, PD SHANK, BLACK OXIDE, STEEL, UNS G87400, 125 KSI MIN .2500-28 UNF-3AAS91701C (Current)9/25/2026
E-25 General Standards for Aerospace and Propulsion Systems
BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, DRILLED, PD SHANK, SILVER PLATED, NICKEL ALLOY, UNS N07718, 185 KSI MIN, .1900-32 UNJF-3AAS3250E (Current)9/25/2026
E-25 General Standards for Aerospace and Propulsion Systems
Hybridnav: A Hybrid Approach to Zero-Shot Object Detection with Adaptive Exploration for Autonomous Reconnaissance2026-01-75179/22/2026
Autonomous reconnaissance in unknown or contested environments demands robust perception systems capable of identifying diverse objects without prior training data. This paper presents HybridNAV, a hybrid framework that combines multiple foundation models with an adaptive navigation system for zero-shot object detection and autonomous exploration. Unlike monolithic detection models, HybridNAV’s multi-model fusion achieves balanced precision (0.60) and recall (0.58) with a macro F-score of 0.59, representing a 24% improvement over single-model baselines. The adaptive navigation system reduces scan time by 25% and path length by 30% compared to static waypoint approaches, while operating in real-time at 3.2 Hz with sub-100 msec latency on resource-constrained hardware. All processing is performed locally on the robotic platform, eliminating reliance on external communication infrastructure—a critical requirement for operations in communication-denied environments. We evaluate HybridNAV in both simulated indoor scenes and physical robot trials, demonstrating its effectiveness for intelligence gathering in unknown environments.
Indurthi, Hemanth, Martinson, Eric
Counterfeit Avoidance and Quality Assurance: Supply Chain Screening of Cots Microelectronics in Tactical System2026-01-75239/22/2026
This paper details the successful scaling demonstration of a comprehensive supply chain screening process for commercial off-the-shelf (COTS) motherboard subassemblies used in tactical servers for naval applications. Our approach leverages Power Fingerprinting (PFP) technology, which uses unintended analog emissions and machine learning to provide independent, non-destructive, and scalable integrity assessment of microelectronics. The primary goal of the effort was to demonstrate the effectiveness and scalability of the PFP screening process without disrupting or delaying the manufacturing workflow. The screening successfully detected hardware and firmware modifications and identified two cases of abnormal behavior: unusual BIOS power reset and elevated CPU sensor readings on two motherboard subassemblies. Following our quality control forensic analysis, we determined the root cause of these anomalies and their potential impact on the host platform.
Aguayo Gonzalez, Carlos R., Roberson, Ken
Decision-Centric Virtual Metrology for Geometric Deviation via Foundation-Embedding Retrieval2026-01-75549/22/2026
Modern defense manufacturing and sustainment require timely engineering decisions (e.g., inspection triage, rework/accept decisions, and process adjustment) based on the as-built geometric quality. Advanced machining systems generate rich multichannel controller and sensor streams, yet accurate geometric deviation labels remain costly and delayed because they depend on downstream metrology. This paper introduces ChronosGD, a retrieval-based virtual metrology framework. ChronosGD predicts pointwise geometric deviation from multichannel time series data by: (1) retrieving the most similar historical process windows in a frozen Chronos-2 embedding space, and (2) transferring deviation information through similarity-weighted aggregation. ChronosGD avoids plant-specific gradient retraining during deployment; adaptation is achieved by refreshing a labeled historical memory as new inspected parts become available, while preserving traceability through explicit neighbor provenance.
Hoang, Danny, Matthiessen, Ryan, Miller, Christopher, Mannan, Nasir, ElKharboutly, Ruby, Gorsich, David, Castanier, Matthew P., Imani, Farhad
Methods for Designing Rotating Components for Compliance to ISO 1940 Balance Requirements using Generic 3D CAD Software2026-01-75659/22/2026
The benefits of specifying balance requirements in terms of an ISO 1940 balance quality grade instead of traditional mass-distance based requirements are discussed along with methods to convert ISO 1940 balance quality grades into permissible imbalance limits at the bearing supports. Methods are developed to determine the expected imbalance values at bearing supports using mass property data from generic 3D CAD software packages without the need for Finite Element Analysis. Practical exercises are presented using these methods to assess a part’s compliance to ISO 1940 while still in the conceptual 3D CAD design stage. These practical exercises cover the selection of appropriate geometric tolerances to ensure part balance without the need for post fabrication balancing as well as the design of nonsymmetrical components for ISO 1940 balance compliance. Citation: J. Srodawa, “Methods for Designing Rotating Components for Compliance to ISO 1940 Balance Requirements Using Generic 3D CAD Software,” In Proceedings of the Ground Vehicle Systems Engineering and Technology Symposium (GVSETS), NDIA, Novi, MI, Aug. 11-13, 2026.
Srodawa, John
BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, DRILLED, PD SHANK, NICKEL ALLOY, UNS N07718, 185 KSI MIN, .3750-24 UNJF-3AAS3246F (Current)9/22/2026
E-25 General Standards for Aerospace and Propulsion Systems
BOLT, MACHINE - DOUBLE HEX EXTENDED WASHER HEAD, DRILLED, CLOSE TOL SHANK, AMS5643 (UNS S17400), 140 KSI, .5625-18 UNJF-3AAS3180C (Current)9/22/2026
E-25 General Standards for Aerospace and Propulsion Systems
Steel, Maraging, Bars, Forgings, Mechanical Tubing, Rings, and Forging Stock, 18.5Ni - 9.0Co - 4.9Mo - 0.65Ti - 0.10Al (Maraging 300), Premium Aircraft Quality, Consumable Electrode Vacuum Remelted, AnnealedAMS6514L (Current)9/22/2026
This specification covers a premium aircraft-quality steel in the form of bars, forgings, mechanical tubing, flash-welded rings up through 10.000 inches (254.00 mm), inclusive, in diameter or least distance between parallel sides, and stock of any size for forging or flash-welded rings.
AMS E Carbon and Low Alloy Steels Committee
BOLT, MACHINE - DOUBLE HEXAGON, EXTENDED WASHER HEAD, PD SHANK, DRILLED, NICKEL ALLOY (UNS N07001), .1900-32 UNJF-3AAS9705F (Current)9/22/2026
E-25 General Standards for Aerospace and Propulsion Systems
BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, DRILLED, PD SHANK, NICKEL ALLOY, UNS N07718, 185 KSI UTS MIN, .1900-32 UNJF-3AAS3243F (Current)9/22/2026
E-25 General Standards for Aerospace and Propulsion Systems
BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, DRILLED, FULL SHANK, STEEL AMS6322, CADMIUM PLATED, .3750-24 UNJF-3AAS9944C (Current)9/22/2026
E-25 General Standards for Aerospace and Propulsion Systems
BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, DRILLED, PD SHANK, CADMIUM PLATED, STEEL, (UNS G87400), 125 KSI MIN, .1900-32 UNJF-3AAS9923D (Current)9/22/2026
E-25 General Standards for Aerospace and Propulsion Systems
BOLT, MACHINE - DOUBLE HEX EXTENDED WASHER HEAD, CLOSE TOLERANCE SHANK, UNS S66286 - 160 KSIAS3530D (Current)9/21/2026
E-25 General Standards for Aerospace and Propulsion Systems
Fittings, Tube, Fluid System, 3000 psig (21000 kPa) Rated Pressure, Externally Swaged, Specification ForAS4459C (Current)9/21/2026
This SAE Aerospace Standard (AS) establishes the requirements for externally swaged tube-fitting assemblies used in aircraft fluid systems in the following pressure classes: B (1500 psi or 10500 kPa), and D (3000 psi or 21000 kPa), and in temperature types I (-65 to 160 °F or -55 to 70 °C), and II (-65 to 275 °F or -55 to 135 °C) of AS2001. This specification covers a common Cres, titanium, and aluminum fittings that may be used for a range of operating pressures up to 3000 psi with different tubing materials and tubing wall thicknesses, and is assembled with the same tooling in accordance with AS5902. Table 11 shows applicable aerospace fitting part number standard and tubing materials and operating pressures.
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
Plain Spherical Bearing Radial and Axial Clearance MeasurementARP5448/8B (Current)9/21/2026
This test method provides a guidance for determining the total free play between the ball and outer ring of a spherical bearing when measured in both the radial and axial directions. Bearings covered by this test method include all plain spherical-type bearings, both self-lubricated (lined) and metal-to-metal.
ACBG Plain Bearing Committee
CRIMPING TOOL AND ACCESSORIES, REMOTE CRIMP HEAD, HYDRAULIC, WIRE SIZE 8 TO 0000 FOR INSULATED AND UN-INSULATED CRIMP BARRELSAS5259/1C (Current)9/20/2026
AE-8C2 Terminating Devices and Tooling Committee
Effect of Annular Gap Variation in Coaxial Jets2026-01-50759/17/2026
A numerical study on the influence of annular gap variation in correctly expanded sonic coaxial jets, focusing on its effect on mixing characteristics and jet symmetry, is presented in this paper. The computational simulations were conducted using a three-dimensional steady-state compressible Reynolds-Averaged Navier–Stokes (RANS) framework with the Spalart–Allmaras (SA) turbulence model. Both symmetric (uniform gap) and asymmetric (nonuniform gap) configurations were simulated. Eccentricity was introduced by offsetting the secondary nozzle by 2 mm downward from the center of the primary nozzle. In symmetric configurations with uniform annular gaps, the jet exhibited balanced shear-layer development, uniform entrainment, and symmetric Mach decay characteristics. However, the asymmetric annular gap configuration exhibited approximately 25–30% earlier potential core breakdown, 30–35% greater radial jet spreading, and nearly 6–10% faster centerline velocity decay compared with the symmetric configuration. The streamline analysis revealed enhanced entrainment, localized recirculation regions, asymmetric vortex generation, and accelerated momentum diffusion caused by unequal shear-layer interaction. These results demonstrate that annular gap asymmetry can serve as an effective passive flow control strategy for enhancing jet mixing and directional momentum redistribution. Such configurations may be useful in practical applications including exhaust gas dilution, fuel–air mixing enhancement in combustors, thrust vectoring, and jet-noise suppression systems.
Chandra Bose, Gurusamy, Sudalaimuthu, Ganesan
FITTING END, STANDARD DIMENSIONS FOR BULKHEAD FLARELESS TUBE CONNECTIONSAS33515E (Current)9/17/2026
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
FITTING END, ACORN, SHORT FLARELESS, DESIGN STANDARDAS4703B (Current)9/17/2026
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
FITTING END, FLARELESS, BLUNT NOSE, DESIGN STANDARDAS4458C (Current)9/17/2026
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
A Study on the Development of Brake Moan Analysis for CTBA Vehicles Using Simulation2026-01-08149/14/2026
Moan noise is a low-frequency noise occurring in the 170–500 Hz frequency ranges. While it frequently appears in vehicles equipped with a rear Coupled Torsion Beam Axle (CTBA), the exact cause, generation mechanism and clear solutions remain unidentified. For those reasons, we have developed a moan noise analysis method capable of representing the moan noise phenomenon in vehicles with rear CTBA along with an automation tool. From these results, we can use moan analysis models to reduce real moan noise problems. Consequently, this not only enhances customer satisfaction and vehicle quality but also significantly increases the work efficiency of vehicle designers through design modification in the preliminary stages of vehicle development
Kim, Sungho, Kim, Jeongkyu, Hwang, Jaekeun, Kang, Donghoon
Further Investigation of Brake Squeal: Effect of (Inboard/Outboard) Pads Property Differential2026-01-07999/14/2026
It was reported earlier that the wear differential between the inboard pad and the outboard pad leads to brake squeal generation. The (inboard/outboard) pads wear differential can occur due to hardware issues such as brake pad drag and/or two different wear rates of the (I/O) pads, which is caused by two different material properties of the pads although the pad formula may be the same. It is found that (I/O) pads compressibility differential/hardness differential/friction differential are all interrelated and that they contribute to brake squeal generation in addition to the inboard pad tangential/radial taper wear. A method has been found to separate the inboard pad friction and the outboard pad friction and to estimate each friction coefficient.
Liu, Richard, Wu, Shane, Wu, Godot, Zou, Tianlang
Design Considerations for Optimizing the Wheel Bearing Outer Ring Bolt-Mounting Pattern for Reduced Drag2026-01-08309/14/2026
Electric vehicles (EVs) impose more demanding operating conditions on wheel bearing systems due to increased vehicle mass, higher drive torque, and the need to maximize energy efficiency and driving range. These factors elevate the loads transmitted through the bearing to knuckle joint and often require higher clamp loads to ensure joint integrity. However, higher clamp loads amplify distortion of the wheel bearing outer ring, increasing rotational drag and reducing bearing durability. Controlling outer ring distortion is therefore critical for EV wheel bearing design, as well as for high performance vehicles that experience severe lateral loads at the hub to knuckle interface. This paper investigates key design considerations for optimizing the wheel bearing outer ring and its mounting interface to minimize distortion under elevated clamp loads. A comprehensive CAE-based Design of Experiments (DOE) is used to evaluate the influence of multiple bolt-mounting patterns including rectangular, square, and trapezoidal configurations and the relative alignment of the bolt pattern between the outer ring and knuckle. The study also compares the performance of M12 and M14 fastener variants across loading conditions representative of EV and high-performance applications. The results identify geometric and interface design parameters that significantly reduce outer ring out of roundness, thereby lowering drag torque and improving long-term bearing life.
Mandhadi, Chaitanya Reddy, Lee, Seungpyo, Bovee, Benjamin, Callaghan, Kevin
FITTING ASSEMBLY, 45° ELBOW, EXTERNAL SWAGE TO FEMALE FLARELESS, HYDRAULICAS6468A (Current)9/11/2026
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
FITTING ASSEMBLY, TEE, FEMALE FLARELESS TO EXTERNAL SWAGE ON RUN, EXTERNAL SWAGE ON BRANCH, HYDRAULICAS6471A (Current)9/11/2026
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
Ultrasonic Frequency-Domain Reverse-Time Migration Imaging Incorporating Element Directivity Correction2026-99-14199/11/2026
The finite width of ultrasonic array elements results in a non-uniform angular radiation pattern of elastic waves in solids, deviating from the ideal point-source assumption commonly adopted in reverse-time migration (RTM). This angular radiation non-uniformity produces a crack tip-dominated imaging amplitude with weak crack flank representation, manifesting as a pronounced depth-dependent amplitude imbalance along vertically oriented defects. As a result, cracks may be misinterpreted as point reflectors, which compromises the reliability of characterization in ultrasonic nondestructive testing (NDT). This study proposes an ultrasonic frequency-domain reverse-time migration (FDRTM) imaging method incorporating element directivity correction. A longitudinal-wave directivity model in solids is formulated in the frequency domain and normalized at each frequency to ensure consistent scaling during multi-frequency stacking. During backward wavefield reconstruction using full matrix capture (FMC) data, the angular-dependent energy distribution associated with the receiving direction is explicitly corrected, rebalancing the angular energy distribution in the reconstructed wavefield. Defect imaging is then performed using a frequency-domain cross-correlation imaging condition, followed by stacking over frequency and normalization. Validation experiments were conducted on an artificially manufactured vertical crack in a 7075 aluminum alloy specimen. The results indicate that, relative to conventional RTM, the proposed method reduces crack tip dominance and enhances the relative visibility and continuity of crack flanks. Compared with conventional RTM, the peak imaging amplitude increases by 22.44%, and the amplitude at a depth of 6.8 mm is enhanced by 24.39%. In addition, the proposed method outperforms the total focusing method (TFM) in crack profile continuity and the relative visibility of crack flanks. The results confirm that incorporating element directivity correction into frequency-domain RTM mitigates depth-dependent amplitude imbalance and restores crack flank visibility, thereby improving the reliability of crack defect characterization in ultrasonic NDT.
Chen, Si, Zhang, Yifeng, Ma, Tengfei, Xu, Zheng, Jiang, Jiansheng, Gao, Jiaqi
An Improved Multi-Object Vehicle Detection Algorithm Based on YOLOv11s2026-99-11299/11/2026
For object detection in complex road situations, such as inadequate detection performance and difficulties caused by vehicle occlusion and cluttered environments, this paper pursues a YOLOv11s-based object detection framework. The algorithm successfully designed a novel PEConv module. This module integrates a partial convolutional network with an efficient multi-head attention mechanism. Through a Split operation, the input image is divided into locally enhanced channels and original channels. The locally enhanced channels undergo partial convolution and feature weight allocation via the efficient multi- head attention mechanism for feature extraction. Finally, these channels are fused with the original channels before undergoing convolution. This approach preserves the original features while minimising feature loss caused by the series of operations. Therefore, the PEConv module is based on a partially convolutional network and efficient multi-head attention. It improves the detection ability by precisely giving more weight to small objects and occluded parts with augmented partial channel attention and original channel fusion. This study further enhances the model’s detection precision and improves its performance in addressing small target vehicles and severe occlusion issues by refining and upgrading the original C3K2 architecture. The LSBlock is integrated into the original model’s bottleneck structure, replacing the traditional 3x3 convolution to create the C3K2 - LSBlock module. Experimental results show that on the UA - DETRAC dataset, compared with the original YOLOv11s, the optimized YOLOv11s has improved the original mAP @ 50 by 3.4%, reaching 61.3%, and improved the original mAP @ 50: 95 by 2%, which verifies the correctness of it.
Chen, Yulin, Wang, Yini, Wang, Jianwei, Zhang, Xin
Structural Design and Stability Research of a Two-DOF Transformable Wheel for Enhanced Obstacle-Crossing Performance on Complex Terrain2026-99-11309/11/2026
Under the constraints of conventional chassis layouts, traditional wheeled vehicles struggle to maintain stable obstacle-crossing performance on complex terrain. This study aims to enhance both the obstacle-crossing capability and stability of such vehicles. First, a transformable wheel capable of varying its effective radius and actively adjusting the wheel–ground contact configuration is designed, and its degrees of freedom are analyzed using screw theory. Next, based on screw theory and Lie group theory, position-level and velocity-level kinematic models of the transformable wheel are established, and system-level performance indices—including workspace, singular configurations, and force-transmission characteristics—are formulated. Finally, taking these performance indices as optimization objectives, a constrained optimization model of the mechanism’s geometric parameters is constructed, from which an optimal dimension set for the transformable wheel is obtained. The results show that the optimized transformable wheel has significantly improved minimum singularity and dexterity. The designed transformable wheel can achieve changes in wheel radius and wheel rim inclination angle, improving the vehicle's passability in complex terrain.
Lu, Shichuang, Wang, Tie
Loosening Behavior of Flared Tube Fittings under Transversal Vibration Conditions2026-99-11139/11/2026
Flared tube fittings are extensively utilized in pipeline systems due to their effective connection and sealing capabilities. However, during practical service conditions, transversal vibration frequently induces thread loosening, subsequently leading to seal failure and other malfunctions. Current research lacks a systematic investigation into the loosening behavior of flared tube fittings under transversal vibration conditions. This study establishes a precise finite element model of the flared tube fitting and systematically examines its loosening behavior under stress redistribution, plastic deformation, and fretting wear conditions by simulating the assembly process and applying cyclic transversal vibration loads. The research findings demonstrate that the loosening process of flared tube fittings occurs in two distinct stages. The initial stage primarily involves preload reduction caused by non-rotational factors such as stress redistribution, while the subsequent stage features continuous preload attenuation resulting from relative rotation between internal and external threads. Notably, a critical amplitude has been identified. When the actual transversal amplitude remains below this critical value, only non-rotational loosening occurs in the flared tube fitting, with no rotational loosening taking place. Further investigation into factors affecting the critical amplitude, including preload, friction coefficient, material properties, and thread type, reveals that preload, friction coefficient, and material elastic modulus significantly influence the critical amplitude, whereas thread type demonstrates a negligible impact. These findings provide valuable insights for enhancing the reliability of flared tube fittings in vibration-prone applications.
Liu, Chang, Li, Muxiao, Chen, Hanlin, Xu, Dong, Gong, Zhengchao
Mechanical Properties and Freeze-Thaw Resistance of Modified Portland Cement-Stabilized Soil for Road Engineering2026-99-15809/11/2026
Subgrade soil is related to the load on the upper part of the road, and its properties will affect the road surface conditions. Frost-thaw action will damage the soil in cold regions. This study focuses on the fine-grained sand in Jilin affected by seasonal frost-thaw, and explores the effects of mixing amount (0% - 6%), curing time (7 days, 28 days), and frost-thaw cycle times (0, 5, 10, 20 times) on the DRM (dynamic resilient modulus) and UCS (unconfined compressive strength) of Portland cement-stabilized soil. The results are: the increase of mixing amount and the extension of curing time will both increase the UCS and DRM; frost-thaw cycles will reduce the UCS and DRM. Roads in cold regions need to use 4% modifier mixture for maintenance for 28 days to achieve strength stability. Heavy subgrades use 6% modifier to obtain the best stiffness load - bearing. This study has insightful guidance for subgrade material improvement in seasonal frozen soil regions.
Wang, Shujuan, Duan, Yonggang, Qin, Weijun, Shen, Ruoting, Jin, Chenguang
Aerodynamic Design and Optimization Study of a Ma 0-5 Two-Dimensional Wide-Range Adjustable Nozzle2026-99-14039/11/2026
To address the thrust requirements across multiple operating conditions of hypersonic vehicles during wide-speed-range flight (Ma 0–5), this paper presents the design of a two-dimensional adjustable nozzle with a circular-to-rectangular cross-section. A maximum-thrust contour was constructed using the method of characteristics, and the aerodynamic performance and structural features of this rotation-based adjustment approach were systematically analyzed. The results demonstrate that the nozzle achieves a thrust coefficient between 0.951 and 0.992 across the entire flight envelope, with a thrust vector angle consistently maintained at 0°, indicating excellent thrust performance and flow-field symmetry. Furthermore, by introducing a biaxial transition segment and optimizing its tangent angle (θ = 130°) alongside fillet rounding (R = 30 mm), unsteady flow oscillations and separation at high Mach numbers were effectively eliminated, enhancing both structural durability and aerodynamic stability.
Feng, Fan, Lv, Zheng, Xu, Jinglei
Real-time Vehicle Speed Detection Based on YOLOv11 and DeepSORT2026-99-15959/11/2026
The technology of real-time and effective vehicle speed detection is considered a key technology to improve traffic monitoring efficiency and traffic safety management grade. To address the limitations of traditional speed detection schemes—including reliance on dedicated hardware, poor environmental adaptability, and high construction and maintenance costs—this paper proposes a r10eal-time vehicle speed detection system based on YOLOv11 and the DeepSORT algorithm. The proposed system uses the YOLOv11 target detection algorithm as its primary model. DeepSORT multi-target tracking technology is integrated to enhance tracking performance. Speed measurement is implemented using a virtual detection line. This approach enables accurate vehicle detection, continuous tracking, and real-time speed measurement within video frames. Through the experiments, the result shows that the improved YOLOv11n model reaches mAP@0.5 of 0.982 and a recall rate of 0.956 in the test set, higher than the YOLOv8n and YOLOv5s models. The speed detection error can be restricted to 3 km/h, satisfying the real-time detection need. There is no need for road surface modification, and the detection system has a flexible layout, providing a dynamic basis for traffic law enforcement and traffic data support for road construction and traffic control optimization.
Jin, Guowei, Ma, Wenlong, Jiang, Dali, Li, Nan
Study on Low-Velocity Impact Damage of Glass Fiber Reinforced Composite Pipeline2026-99-14169/11/2026
Through low-velocity impact testing, the effects of punch shape (conical, hemispherical, and cylindrical) and impact energy (5, 10, and 15 J) on damage characteristics in glass fiber composite pipes were investigated. Ultrasonic A-scan inspection was employed to detect internal delamination damage at the impact points within the composite pipes. Test results indicate that the contact area between the punch and the pipe is a key factor influencing the severity of pipe damage. A smaller contact area results in a higher energy absorption rate, greater punch displacement, larger area under the load-displacement curve, and longer contact time, leading to more severe damage characteristics. When the conical punch delivered 15 J of impact energy, the energy absorption rate of the glass fiber composite pipe reached 91.6%, exhibiting multiple damage characteristics, including pitting, penetration, and cross-shaped cracks. As impact energy increases, the area of internal delamination damage caused by the three punch shapes exhibits near-linear growth. The conical punch induces severe damage characteristics in the thickness direction but results in the smallest delamination area. Blunt-shaped punches (hemispherical and cylindrical) disperse impact energy over a wider region, leading to increased delamination damage area.
Wang, Xuan, Cao, Yanzhen
Intelligent Mold Library System for Copper Tube Drawing Process2026-99-11089/11/2026
With the continuous and in-depth advancement of automotive lightweighting, the quality issues of automotive components have become increasingly prominent. Copper tubes, as an important component of automotive air conditioners, also need to ensure their quality level. In the production process of copper tubes, the multi- pass moving core head disc drawing process is one of the commonly used processing techniques. The relevant drawing dies determine the drawing effect and the quality of the finished copper tubes, so it is necessary to make a reasonable combination of drawing dies. At present, many copper tube processing enterprises overly rely on manual experience for mold matching work. Moreover, mold inventory information, usage records of matching molds, and mold size measurements are all completed by different operators. The operation procedures are not standardized, the standardization of mold matching operations is insufficient, there are too many uncertain factors, and the degree of human influence is too high. The intelligent mold library system for copper tube drawing process is designed to address the problems of weak stability, poor reproducibility, and insufficient precision in the existing manual mold matching. It facilitates accurate computation and control of process parameters. Compared with the estimation and rough adjustment based on manual experience, it can more accurately achieve the best parameter combination required by the process, thereby improving product quality and production efficiency. By integrating the mold matching methods of drawing pass process parameters such as the double decreasing method, the minimum pass method, the empirical pass method, the ZBL method, and the KD-KS coefficient method, and combining the inventory information in the system, it is ensured that the mold matching scheme generated by the algorithm is the best one, thereby improving the production level of the production process.
Yue, Fengli, Meng, Dezhi, Cui, Haitao, Zhang, Jiakun, Sun, Hongyun
Data-Driven Design of Copper Tube Drawing Algorithm for Automotive Air Conditioning Systems2026-99-11109/11/2026
As a critical component in thermal management systems, copper tubes are widely used in automotive radiators, condensers, and other parts. In copper tube production, the drawing process is essential for achieving target dimensions and performance specifications. However, as the copper tube industry evolves, nowadays manual drawing process design and traditional drawing algorithms struggle to meet increasingly diverse finished product specifications and complex manufacturing requirements. To address this issue, this study developed an intelligent drawing process design algorithm suitable for automotive copper tube production. This algorithm builds upon existing drawing without plug algorithms, floating plug drawing algorithms, and manually compiled drawing process sheets. It first learns the fundamental principles of drawing without plug algorithms, then derives the relationship between wall thickness changes before and after drawing using mathematical formulas. Subsequently, by analyzing the enterprise’s existing 297 drawing process sheets, the design principles of the drawing without plug algorithm were extracted. This established the number and positioning of required drawing without plug processes within different drawing procedures as the design principles for drawing without plug. Then, using the ‘Double decrement method’ from the floating plug drawing algorithm as an example and integrating the design principles of drawing without plug processes, we developed an intelligent drawing process design algorithm suitable for automotive copper tube production. Furthermore, we selected a typical drawing process sheet for comparison. Through comparative analysis of key parameters such as processing rate and relative wall thickness reduction coefficient, we validated that this algorithm yields more rational results compared to traditional methods. Utilizing this algorithm not only significantly reduces the workload for drawing process designers but also produces more optimal drawing process design outcomes. Compared to other floating plug drawing algorithms, this algorithm also demonstrates greater universality.
Yue, Fengli, Zhang, Jiakun, Liu, Jinsong, Meng, Dezhi
Experimental Analysis of Tube Temperature and Heat Transfer Performance of L-Shaped Gravity Heat Pipes2026-99-15119/11/2026
Gravity heat pipes achieve efficient energy transfer through the evaporation and condensation of their internal working fluid, which steadily conducts underground heat to the surface and thereby provides a continuous and stable heat source for road pavements in winter. Considering the snow and ice melting demand of road surfaces in winter, this paper establishes an indoor environmental simulation experimental platform to systematically investigate the influence laws of different working fluids on the start-up temperature, start-up pressure, heat transfer power, and other key performance indicators of L-shaped gravity heat pipes. Through experimental research and analysis, it is revealed that heat pipes with R-134a and R245fa working fluids can operate stably at a shallow geothermal temperature of about 25 °C, while the acetone working fluid heat pipe operates unstably under this condition. The heat pipe filled with R-134a working fluid achieves the maximum heat transfer power under shallow geothermal conditions, followed by the heat pipe filled with R245fa. Although the heat transfer power of the acetone-filled heat pipe is generally relatively low, its heat transfer power increases most significantly with the rise of the evaporation section temperature. Under low-temperature conditions, the thermal conductivity of the evaporation section increases with the rise in the heating temperature of the evaporation section, while that of the condensation section decreases with the increase in the heating temperature of the evaporation section. Through experimental research and comparative analysis, this paper deeply explores the application potential of gravity heat pipe technology in green highway construction, and evaluates the feasibility and economic benefits of its engineering implementation, which provides a scientific basis and engineering guidance for the selection of green energy in future infrastructure construction.
Wang, Zhen-kun, Yuan, Zhi-ming, Wang, Kang, Zhang, Wen-jun, Wu, Xiang-song, Liu, Guang-bo
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