Browse Topic: Imaging and visualization
g-C₃N₄, a metal-free semiconductor photocatalyst, demonstrates remarkable potential, but its practical application in pollutant degradation is significantly limited by the rapid recombination of photogenerated electron-hole pairs and low photocatalytic efficiency. To address this, a series of magnetic recyclable g-C₃N₄/CoFe₂O₄ composite photocatalysts with different CoFe₂O₄ doping ratios were innovatively designed and prepared via thermal polymerization, sol- gel, and combined with ultrasonic and heat treatment processes. The novelty of this composite design lies in the effective integration of magnetic CoFe₂O₄ with g-C₃N₄ through a heterojunction structure. It substantially boosts the absorption of visible light. Concurrently, it effectively fosters the separation and mobility of photo-induced charge carriers. The composite materials were systematically characterized by X-ray diffraction, thermogravimetric analysis, scanning electron microscopy with energy-dispersive X-ray spectroscopy, photoluminescence spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy. Using tetracycline hydrochloride as the target pollutant, the photocatalytic activity of the composites was evaluated under visible light irradiation, and the effects of initial concentration, catalyst dosage, and the influence of solution pH on degradation efficiency were also examined. The results indicated that the composite with a CoFe₂O₄ to g-C₃N₄ mass ratio of 1:3 (denoted as 3-CN/CFO) exhibited the optimal performance: a TCH degradation rate of 80.29 % within 105 minutes and a total organic carbon removal rate of 61.63 %. After five consecutive cycling experiments, the degradation efficiency remained above 70 %, demonstrating good reusability and stability. The performance improvement is attributed to the formation of heterojunctions in the composite, which effectively facilitates charge separation, inhibits carrier recombination, and enhances visible light absorption. Furthermore, the inherent magnetism of the composite permits efficient recovery, streamlining its integration into practical applications. Toward the purification of antibiotic-contaminated water, this research proposes a viable method for fabricating highly effective and recyclable photocatalysts.
In order to reduce traffic accidents caused by cars straying from lanes, a lane line recognition and deviation warning system based on machine vision is designed. It mainly includes image preprocessing, lane line detection, and the design of a deviation warning model. “In this study, an ROS-based intelligent vehicle-mounted camera is adopted for road image collection. To reduce the computational load of data processing while guaranteeing the algorithm’s accuracy and reliability, grayscale conversion and region of interest (ROI) extraction are implemented to finish the image preprocessing stage. Additionally, a fusion strategy of global and local thresholds is introduced to enhance both the operational speed and detection accuracy of the algorithm” use the Canny operator for the edge feature extraction; and complete the fitted lane lines with the improved Hough transform. Finally, based on the Kalman filter and camera viewpoint conversion coefficient algorithm, the lane line offset is detected in real time, and the deviation is judged in combination with the monitoring interface. Simulation experiments show that the system is able to effectively recognize the lane line and judge the deviation status under the condition of setting the offset threshold of 70 pixels, which significantly improves the accuracy and real-time performance of the lane deviation warning and provides effective technical support for reducing traffic accidents.
Compliance verification in aerospace systems often relies on labor-intensive workflows that demand extensive manual effort to produce structured review documentation and requirement matrices. These processes can span dozens of hours per review, are vulnerable to inconsistencies due to non-standardized annotations, and depend heavily on individual interpretation of fragmented technical sources. With a growing backlog of review tasks and a steady influx of new requests, the need for scalable automation has become increasingly important. This study presents a modular automation framework designed to streamline compliance assessments through intelligent document parsing, requirement extraction, and matrix generation. The system integrates optical character recognition, computer vision, and natural language processing techniques to process both scanned and digital documents. By digitizing data across multiple hardware configurations and automating extraction from diverse technical records, the framework enables consistent evaluation across a broad spectrum of requirement categories. Automation scripts and standardized templates facilitate rapid population of compliance matrices, reducing manual hand-offs and minimizing reliance on specialized expertise. Implementation led to a 39% reduction in turnaround time and a 62% increase in monthly throughput, demonstrating measurable efficiency gains in the compliance review process. This framework exemplifies how intelligent automation can drive operational efficiency, deliver measurable cost savings, and pioneer data-driven and scalable innovation in aerospace compliance engineering.
Under a microscope, a bouquet of lollipop-like structures, each smaller than a grain of sand, waves gently in a petri dish of liquid. Suddenly, they snap together, like the jaws of a Venus flytrap, as a scientist waves a small magnet over the dish. What was previously an assemblage of tiny passive structures has transformed instantly into an active robotic gripper.
Medical imaging technology is advancing rapidly, bringing new opportunities and challenges for machine designers. Systems that once required dedicated hospital rooms and significant floor space are becoming more compact, faster, mobile and capable of delivering increasingly detailed clinical insight. From advanced CT scanners to imaging platforms integrated with surgical robotics, imaging equipment is evolving toward more point-of-care (POC) solutions to meet rising expectations for diagnostic accuracy, procedural guidance and operational efficiency.
Space vehicle and satellite development programs are driving demand for new small- and medium-sized satellites across commercial and defense imaging, data collection, and other space-based applications.
As satellites take on more onboard processing - from Earth imaging to autonomy - spacecraft computing designers are pushing for higher performance under tight thermal and radiation constraints. Here's how suppliers are approaching heat removal, radiation mitigation and production-scale space-grade computing for LEO and beyond.
The aging of the population has been a key issue worldwide, with mobility and fall of the elderly an important problem to be solved. In this paper, we propose an elderly mobility assist system based on the intelligent power-assisted device consisting of an assistive cane and an intelligent companion. It has the functions of standing support after falling, daily support and on-site rest. The assistive cane adopts a two-stage expansion mechanism of crank and slider structure, which forms a stable triangular support after unfolding, so that the patient can stand safely. The intelligent companion platform is driven by drive wheels, equipped with pushrod motors and vacuum suction devices, it can automatically approach the user and form an stable support column when the cane is in the out-of reach range; the control system is designed by combining microcontroller, camera object recognition, wristband remote control, to realize automatic steering and autonomous navigation at differential speed. The overall design satisfies the requirements of safety and strength through mechanical verification and stress analysis. The proposed system can help the elderly people to recover from falls better and enhance their independence and safety in their daily walks.
The Army requires rotorcraft drive systems to operate for 30 minutes following a loss of lubrication event to make an emergency landing. Coatings research has shown great promise for loss of lubrication, but coating repeatability and quality control is a primary hurdle. The Army partnered with Acree Technologies via a Small Business Innovation Research (SBIR) effort to develop an optimized gear coating for loss of lubrication. The research culminated in a system level transmission experiment that maintained flight relevant torque and speed through a helicopter gearbox without oil for three hours. The authors decided to shutdown the experiment for inspection after three hours of operation without oil because the temperature and vibration signals maintained steady state conditions without signs of failure. Teardown analysis showed the transmission gear surfaces did not scuff, scanning electron microscope analysis showed coating remained on the gear teeth, and cross-sectional SEM analysis showed a measurable coating thickness remaining on the gear teeth after three-hours of operation without oil.
This study investigates the aerodynamic response of a small-scale UAV propeller under steady and transient conditions at low Reynolds numbers (104–105;). In this regime, phenomena such as laminar separation, transition, and the formation of recirculation bubbles strongly influence airfoil performance. In addition, the flow response to rapid changes in rotational speed is still poorly understood, as most existing models assume quasi-steady behavior. Experiments were conducted in a low-speed wind tunnel using a commercially available 10-inch class propeller (X500 V2 1045). The propeller was subjected to controlled rotor speed ramps, and phase-locked particle image velocimetry (PIV) was combined with synchronized load measurements to track the flow evolution during acceleration and deceleration. A hysteresis was observed in the thrust response when comparing increasing and decreasing rotational speed at identical operating conditions. At the same time, the PIV measurements reveal that the inflow field and the effective angles of attack at the blade scale evolve dynamically throughout the transient. These findings highlight the importance of transient trajectories in low-Reynolds-number propeller operation and show that quasi-steady models are insufficient to describe the observed aerodynamic behavior.
This paper presents an experimental investigation of ship airwake-rotor interaction under cruise-only and longitudinal gust conditions (cruise + gust). A model-scale NATO Generic Destroyer and rotorcraft were tested using time-resolved stereoscopic particle image velocimetry, a six-axis force/torque load cell, and flush pressure sensors. Flow structures, pressure distributions, and spectral energy within the pilot workload-relevant frequency bands were analyzed. High-pressure regions on the ship deck surface show the interactions between the ship recirculation region and rotor ground effects from downwash. The reduced forward velocity within the airwake leads to decreased thrust and a nose-down pitching moment across the ship deck. For high-disk-loading rotorcraft, the rotor ground effects are less important than the ship airwake effects. The power spectral densities of CT, CMx, and CMy decrease toward higher frequencies, while the PSDs of CFx and CFy retain comparatively higher energy at the upper end of the full-scale pilot workload frequency band. A maximum increase of 54.3% in the CMy pilot workload factor in the cruise + gust conditions is observed at Ldeck, which denotes a significant rise in the demand of pilot inputs near the ship stern. The overall pilot workload factor in the cruise + gust case increased by 35.6% compared to cruise-only at 1.5Ldeck, and decreases into the deck. Overall, gust-driven airwake dynamics intensify rotor loading and increase pilot workload demands during shipboard helicopter operations.
Stacked co-rotating rotors offer a mechanically simple alternative to conventional coaxial counter-rotating systems, but their aerodynamic performance is strongly dependent on both axial and azimuthal blade spacing. This study experimentally and numerically investigates the effects of rotor spacing on the performance and wake structure of model-scale stacked rotors in hover. A dedicated test platform was developed to measure thrust, power, and phase-resolved 2D-3C particle image velocimetry flow fields for two-bladed stacked rotors over axial spacings of Δz/c=0.75 to 5 and azimuthal spacings of ϕ = 0° and 90°. Relative to isolated two- and four-bladed baseline rotors, the stacked configurations exhibited measurable variations in total hub loading and induced flow structure as a function of spacing. The flow field results show that changes in axial spacing alter the relative position of the lower rotor within the convected wake of the upper rotor, producing corresponding changes in inflow, effective angle of attack, and total thrust. Azimuthal spacing further modifies these trends by shifting the phase relationship between upper- and lower-rotor blade passages. To interpret these effects, a coupled blade element momentum theory and Blade Interaction Prediction model was developed. The model captures the primary trends in measured thrust and sectional loading, demonstrating that both wake convection and chordwise blade interaction are required to predict the aerodynamic behavior of closely spaced stacked rotors.
Helicopter tail shake constitutes a significant limitation to both passenger comfort and aircraft stability. Under powered descent conditions, elevated Angle of Attack (AoA) cause flow separation around the rotor hub and engine cowling, leading to the development of an unsteady wake dominated by large-scale turbulent structures. To support the helicopter tail shake phenomenon investigation, a dedicated Particle Image Velocimetry (PIV) experimental setup was designed in this work, together with four aerodynamic devices aimed at mitigating tail shake. These components were then tested through a wind tunnel campaign with the PIV setup. The proposed aerodynamic components were conceived to either deflect the hub wake away from the tail empennages or to decrease the Turbulent Kinetic Energy (TKE) within the wake. To achieve these objectives, a dorsal fin, a horse-collar, and two spoiler configurations inspired by automotive applications were designed and experimentally evaluated. The devices were tested both as standalone solutions and in combined arrangements on a scaled helicopter wind tunnel model featuring a rotating hub and blade shanks. The vertical velocity component, was used as an indicator of wake deflection, and the Turbulent Kinetic Energy was used as an indicator of wake turbulence. The Horse Collar and the Large Spoiler showed a reduction in both indicators suggesting possible tail shake mitigating capabilities, and additional improvements were achieved when the two devices were deployed in combination.
This study presents subscale wind tunnel experiments investigating the transient aerodynamic interactions of a rotor during a continuous relative-wind approach toward the landing deck of the NATO Generic Destroyer. Time-resolved rotor loads and stereoscopic particle image velocimetry measurements were used to characterize the interacting ship-rotor flow field under headwind and quartering wind-over-deck conditions. The measurements captured the evolving influence of ship airwake, ground effect, and superstructure-induced recirculation as the rotor moved from downstream to the final hover position over the deck. The results show that rotor thrust, rolling moment, and pitching moment underwent distinct changes throughout the approach, with the loading trends varying significantly with wind-over-deck angle. Time-frequency analysis further reveals that the unsteady rotor response was concentrated in a limited band of frequencies associated with various coherent flow structures shed from the ship superstructure. Spectral proper orthogonal decomposition was used to identify the dominant airwake features responsible for these fluctuations at specific frequencies, including large-scale structures originating from the radar and hangar region. These findings demonstrate that the dynamic approach resolved both slow- and fast-changing transient aerodynamic effects along the approach path that cannot be captured with static hovering measurements.
This paper presents a wind tunnel investigation on the interactional aerodynamics of a slowed-rotor lift- and thrust-compounded helicopter model in high-speed forward flight. A systematic configuration study was conducted to isolate the aerodynamic contributions of the main rotor, wings, fuselage, and pusher propeller to the aft flowfield, measured using phase-resolved 2D-3C particle image velocimetry. Measurements were acquired at an advance ratio of 0.5 across multiple rotor thrust levels, lift offset trim states, and propeller rotational speeds. The fuselage induces a streamwise velocity deficit of nearly 50% of the freestream near the tail boom due to oncoming flow blockage. This deficit is modulated by the main rotor and wing configurations. The rotor slipstream partially alleviates the deficit by convecting high-speed freestream flow downwards. Lift offset in the asymmetric half-wing configuration suppresses the rotor wake influence, deepening the velocity deficit relative to a conventional rotor trim state. The pusher propeller partially recovers the streamwise velocity deficit, with propeller performance improving in proportion to the magnitude of the deficit due to reduced climb inflow and increased blade sectional angle of attack. These findings demonstrate that the velocity gradient aft of a compound rotorcraft impacts pusher propeller performance, highlighting the importance of flowfield-informed propeller design for improved performance in high-speed forward flight.
Ultrasonic welding (UW) provides a rapid and efficient method for joining composite components by inducing resin flow through thermally driven diffusion and crystallization at the bonded interface. However, in the absence of a multiphysics modeling framework or a digital twin approach, current practice still depends on extensive trial-and-error testing to determine key welding parameters such as vibration amplitude, weld time, weld pressure, hold time, and downspeed. While in-situ thermal cameras can monitor surface temperatures, the internal temperature at the bonded interface is often significantly higher, introducing the risk of thermal degradation and inconsistent bond quality. To overcome these limitations, GEM developed a high-fidelity multiphysics model to establish a quantitative relationship between process parameters and the evolving temperature field within welded thermoplastic parts. The model integrates coupled mechanical, thermal, and acoustic physics to simulate high-frequency vibrations and static pressure, capture the generation and spatial distribution of heat, and represent the temperature-dependent viscoelastic response that governs bond formation. A validation test matrix was designed by systematically varying weld time and vibration amplitude. Through-thickness temperature distributions were measured using infrared thermal imaging, enabling direct comparison with model predictions. Upon validation, the model was applied for process tailoring, allowing precise control of temperature distribution to achieve target bond strength. This integrated modeling and validation approach demonstrated substantial benefits, including reduced design iterations, accelerated process optimization, and improved quality and performance of welded composite structures.
This study examines the aerodynamic interactions between rotors in quadrotor vehicles and their impact on forward-flight stability and performance. Through wind tunnel testing of plus and cross configurations, individual rotor forces and moments were measured across varying hub spacings and advance ratios. Results indicate that rotor-rotor interference significantly alters thrust distribution, inducing unintended rolling and pitching moments. Furthermore, Particle Image Velocimetry (PIV) identified asymmetrical inflow distributions as the primary physical driver of these interactions. While increased hub spacing was found to mitigate aerodynamic coupling. These findings highlight the importance of accounting for aerodynamic interactions in multirotor vehicle design and control, particularly for trimming and optimizing forward-flight performance.
A novel airfoil was designed at a Reynolds number (Re) of 50,000 using a multi-objective, multi-fidelity framework based on unsteady Reynolds-averaged Navier-Stokes (URANS) simulations and a gradient-free optimization approach, and compared with the DEA-11 airfoil. Aerodynamic performance and flow physics were investigated through water tunnel experiments, two-dimensional and three-dimensional URANS simulations, and microscopic particle image velocimetry (Micro-PIV), with numerical results validated against experimental data. At Re = 50,000, the optimized airfoil achieves approximately 60% drag reduction at matched lift coefficient, a reduced extent of flow separation, lower pitching moment, with comparable maximum lift coefficient relative to the DAE-11 baseline. In the three-dimensional setting, a classical aspect ratio correction recovers the finite-wing lift closely, while three-dimensional URANS consistently under-predicts drag at positive angles of attack. Measurements and computations confirm that trailing-edge laminar separation bubbles play a significant role in the observed nonlinearity in the lift curve by inducing a virtual camber and effective incidence change. Consequently, airfoil performance in terms of lift-to-drag ratio (L/D) is highly dependent on Reynolds number in the range of Re = 104-105.
This paper experimentally investigates the effect of positioning of individual blades of a two bladed propeller around the rotor hub on overall noise generated by it. An experimental setup was created to measure noise and performance in an anechoic chamber to carry out parametric study in which axial and azimuthal separations between the two blades were introduced through a custom built rotor hub and balancing weight. The propeller noise that is dominated by tonal components associated with blade passage frequency appears to be influenced by azimuthal separation between individual blades and the broadband components generated by turbulent blade-wake interactions is primarily affected by the axial separation between individual blades. From the present study, it is identified that the rotor configurations with 60° azimuthal and 6 mm (3.2% of rotor radius) axial separation resulted in up to 4.4 dB reduction in Overall Sound Pressure Level (OASPL) and 63.9% reduction in acoustic energy, while the 120° configuration with 6 mm (3.2% of radius) axial separation showed up to 3.8 dB reduction in OASPL and 58.7% reduction in acoustic energy through redistribution in acoustic energy across wider frequency range. Flow-field measurements using Particle Image Velocimetry (PIV) revealed that these improvements are associated with merging of tip vortices, thereby reducing blade-wake interactions, demonstrating that controlled blade spacing through hub modification is an effective passive strategy for reducing UAV propeller noise without affecting the performance significantly.
A wind tunnel investigation to assess the impact of rotor-fuselage spacing on the development of the Vortex Ring State and flow topology is presented. Particle Image Velocimetry was utilised to investigate flow mechanisms across a range of rotor-fuselage spacings and descent ratios, which were compared to that of an isolated rotor configuration. Mean flow data was used to identify coherent flow structures, whilst flow unsteadiness was investigated through statistical analysis of the velocity fluctuations. It was found at cases of Vortex Ring State onset, the presence of the fuselage delays the development of the Vortex Ring State for all rotor-fuselage separation distances tested. Furthermore, certain cases of rotor-fuselage spacings display a rotor-fuselage aerodynamic interaction that results in an increased effective descent ratio.
Metal-elastomer bonded components can suffer from manufacturing defects such as porosity and bond-line voids. Nondestructive evaluation (NDE) methods can replace or supplement existing destructive tests; however, implementation can be challenging for manufacturers due to the initial equipment cost, time required per test, and imaging quality. These criteria were used to evaluate shearography, high-resolution ultrasound testing (UT), 2D projection X-ray, computed tomography (CT), and acoustic emission (AE) testing, culminating in trade studies for different sample part types. Experimental work was performed on three samples of varying geometries and sizes with seeded defects, applying feasible NDE methods to each. Shearography succeeded in detecting void defects and flow fronts. X-ray and CT failed to detect flaws in 2 out of 3 part types due to energy and time constraints. UT could not reliably detect defects in parts with complex geometries because of scatter. Acoustic emission reliably detected a seeded knit-line defect.
Accurate monitoring of helicopter operational usage relies heavily on robust regime recognition algorithms. How-ever, evaluating these approaches is challenging when they operate as opaque, "black boxes", as in the case of machine learning-based models. This paper introduces a comprehensive evaluation framework designed to assess regime recog-nition models from a number of perspectives and investigate anomalies in the predicted regimes. Centered around a high-fidelity data set derived from scripted flight tests covering a complete usage spectrum, the developed method-ology provides a comparative baseline. The analytical suite includes 3D spatial visualization tools for flight path mapping, sequential anomaly detection, and confusion matrix metrics. While applying the labeled data set to other platforms presents inherent limitations in terms of mapping features and regimes appropriately, the integrated toolset successfully exposes weaknesses in the model and highlights gaps in training data. Ultimately, this evaluation frame-work enhances the interpretability of model outputs and builds confidence in the use of regime recognition algorithms.
The objective of this study is to experimentally determine the effect a compound helicopter fuselage has on the forward flight performance of a pusher propeller through wind tunnel testing in the Glenn L. Martin Wind Tunnel (GLMWT). This systematic test campaign builds off of previous compound helicopter test campaigns at the University of Maryland (UMD) where various vehicle configurations have been tested at high advance ratios. Present wind tunnel tests were carried out with three distinct vehicle configurations: isolated propeller, isolated fuselage, and finally fuselage with propeller. The effects of fuselage placement on propeller performance are investigated through measuring propeller loads along with two-dimensional three-component phase-resolved particle image velocimetry (PIV) measurements. The PIV measurements are used to inform two different climb velocity models used in Blade Element Momentum Theory (BEMT) to predict the effects of the fuselage on the pusher propeller's performance. Flow field measurements showed a reduction in axial flow velocity closer to the propeller root with the addition of the fuselage, whereas at the outboard 20% of the propeller's radius, the flow remained close to freestream velocity. The thrust over power ratio of the propeller increased in this configuration compared with the isolated propeller, while overall propulsive efficiency remained similar when computed with the scaled climb velocity.
The aerodynamics of propeller--wing interactions during a dynamic tiltrotor conversion maneuver were experimentally studied. This investigation builds upon previous work studying the conversion maneuver as a series of discrete tilt angles. This study varied the freestream velocity, rotational frequency, number of proprotors, proprotor spacing, and conversion time period. Wing loads, surface pressures, and particle image velocimetry were used to investigate tiltrotor aerodynamics. For the multi-proprotor configuration, as the conversion period decreased, wing performance increasingly deviated from quasi-static measurements. Dynamic effects decreased as the freestream velocity increased. Minimal dynamic effects were observed when only one proprotor was used. The greatest dynamic wing performance effects resulted from proprotor-proprotor interactions in proximity to the wing. Several nondimensional parameters including the Transition Number and reduced frequency were evaluated to assess how the dynamic effects observed in the wind tunnel may scale to full-size aircraft.
This experimental study showcases the aeroacoustic sources measured on a NACA0012 airfoil subjected to dynamic stall due to sinusoidal plunging motions. The flow fields are measured on the upper surface of the airfoil using time-resolved particle image velocimetry (PIV), and the broadband surface pressure fluctuations were measured using a flush-mounted microphone probe and the reconstructed pressure field from PIV. Boundary layer separation occurs as the plunging airfoil approaches the maximum plunging velocity. A dynamic stall vortex (DSV) forms on the upper surface near the leading edge. Pressure distribution over the upper surface evolves in response to the movement of the DSV, with the lowest surface pressure observed at the DSV location. Full boundary layer separation results in a temporary reversal of the adverse pressure gradient, and the lowest pressure during moments of full detachment is at the trailing edge. The overall magnitude of the power spectral density (PSD) of the surface pressure fluctuations increases during the stages near the maximum plunging speed, with greater increases observed for the downstroke phase where the DSV is proceeding over the surface. The low-frequency tonal peaks observed at both the DSV location during downstroke and the maximum velocity during upstroke. However, high-frequency broadband fluctuations were measured from the DSV passage during downstroke. These variations of the surface pressure and its broadband components indicate significant unsteady loading and broadband noise sources from a plunging wing.
This study experimentally examines the effect of forced boundary layer (BL) transition on the aerodynamic and aero-acoustic performance of a low Reynolds number rotor in hover. An APC 15×4E two-bladed rotor was tested in three configurations: clean, upper-surface trip (U.S.T.), and combined upper- and lower-surface trip (U.S.T./L.S.T.). Surface oil flow visualization was used to characterize the BL structure. A hover test rig was used to measure the static thrust and torque. Acoustic measurements were conducted in an anechoic chamber, with tonal and broadband noise components separated during post-processing. Results show that surface trips effectively force BL transition, increasing turbulent attachment over the blade. Tripped configurations reduced thrust and increased torque but mitigated Reynolds-number sensitivity. Forced transition reduced the tonal noise for all but one case. For the broadband noise, the forced transition increased the noise in the frequency range where turbulent boundary layer-trailing edge (TBLTE) mechanisms dominate, while decreasing the noise in the frequency range where laminar boundary layer vortex shedding (LBL-VS) occurs.
Bench-level boundary-lubricated fretting experiments were conducted to compare the relative wear of all-steel and hybrid material pairs. Roller-on-raceway contacts were simulated using both AISI M50 steel and Si3N4 cylindrical rollers on flat AISI M50 steel disks. The rollers were 9 mm long with a 9 mm diameter. Tests were conducted with constant amplitude, oscillation frequency, and load. All tests were boundary-lubricated with 0.1 ml of DOD-PRF-85734, MIL-PRF-32538, MILPRF-23699, or unclassified ISO VG 68 aviation gear oil. Wear volume was calculated from 3D measurements on the roller and disk samples after each test. Wear tracks were inspected with light and scanning electron microscopy. It was concluded that hybrid pairs exhibited less wear than all-steel pairs when boundary-lubricated with three of the four aviation gear oils. Both hybrid and all-steel pairs exhibited similar wear when boundary-lubricated with MIL-PRF-23699 oil.
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