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    <title>Transport Research International Documentation (TRID)</title>
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
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      <link>https://trid.trb.org/</link>
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    <item>
      <title>Performance prediction and parametric study of the combined axial-centrifugal compressor</title>
      <link>https://trid.trb.org/View/2696122</link>
      <description><![CDATA[Axial and centrifugal compressors are essential components in gas turbine engines, effectively serving various applications such as aircraft propulsion, marine and land transportation, and power generation. A combined axial-centrifugal compressor stands out as an effective solution, harnessing the advantages of both compressor types. This research delivers a thorough examination of the energy loss correlations associated with these compressors. A carefully selected configuration for the combined compressor is established, leading to the development of a one-dimensional (1D) mean line model. This robust model is employed to accurately predict the performance of the axial, centrifugal, and combined axial-centrifugal compressors. The predictions generated by this model align remarkably well with experimental data from a gas turbine engine operating line. The average discrepancies in pressure ratio and isentropic efficiency predictions for the axial compressor are impressively low at 0.6% and 4.5%, respectively. For the centrifugal compressor, the average differences are also minimal, sitting at 3.4% for pressure ratio and 3.5% for efficiency. Furthermore, the average discrepancy in pressure ratio prediction for the combined compressor reaches just 3.4%. Additionally, the performance curves for the axial, centrifugal, and combined compressors are calculated utilizing the developed model. Finally, an in-depth parametric study is conducted to systematically investigate how various factors such as the solidities of the axial rotor and stator, the axial length of the impeller, and the tip clearance values of the axial rotor and impeller impact the performance of the combined compressor.]]></description>
      <pubDate>Fri, 31 Jul 2026 09:23:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/2696122</guid>
    </item>
    <item>
      <title>Hybrid uncertainty analysis of the nozzle guide vane surface temperature in hydrogen-fueled gas turbine</title>
      <link>https://trid.trb.org/View/2696118</link>
      <description><![CDATA[Hydrogen has the advantages of zero-carbon emission, high heating value per mass, and wide distribution. Hydrogen-fueled gas turbines represent a highly promising way to take advantage of hydrogen energy. The components in the gas turbines are subject to variabilities which can make a significant influence. Therefore, uncertainty analysis is essential. This paper investigates the surface temperature profile of a nozzle guide vane in a hydrogen-fueled gas turbine by considering both stochastic and interval uncertain parameters. The Polynomials Chaos Expansion (PCE)-Chebyshev method is applied to execute the hybrid uncertainty analysis. Coolant flow rate is considered as stochastic uncertain parameter and turbine inlet temperature profile is considered as interval uncertain parameter. A new reliability index is defined and compared with the conventional failure probability. The statistical moments of the interval bounds and the interval bounds of the statistical moments are estimated. The numerical results indicate that the results of PCE-Chebyshev method are in good agreement with the results of Scanning-Monte Carlo simulation method. The global bounds of vane surface temperature are assessed to examine the scope of the impact of uncertainties. Reliability analysis points out that under the influence of uncertainties, the locations with the highest safety on the vane are at the relative radial positions of 0.0 and 0.7, while the locations with the highest risk are at the relative radial positions of 0.4 and 1.0, which constitutes a foundation for the safety design of vane structures and provides a reference for subsequent robust optimization and refined design.]]></description>
      <pubDate>Fri, 31 Jul 2026 09:23:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/2696118</guid>
    </item>
    <item>
      <title>A Study on the Future of Battery Based Electric Aircraft Propulsion</title>
      <link>https://trid.trb.org/View/2712167</link>
      <description><![CDATA[Today the aviation industry is witnessing a paradigm shift in the propulsion technology which has been unseen since the 1930s, when the gas turbine took over from the more established piston engines. For the emerging electric propulsion to survive and flourish, it must demonstrate clear superiority over the mature baseline technology of the gas turbine. It is a fact that the current battery technology is a limiting factor as it is not competitive compared to a gas turbine that is 30-50 times more energy dense. Naturally, the present electric propulsion developments concentrate on smaller aircraft applications and use on a large aircraft is possibly decades away. Apart from the energy density, from a thermal perspective the architectures are vastly different from each other. A conventional aircraft fitted with a gas turbine has readily available heat sinks in fuel and air that aids in heat transfer. Compressed air bleeds from the engine manage the thermal demands of the engine itself plus the aircraft systems. On the other hand, a battery-based aircraft does not have this advantage and therefore must deploy dedicated thermal management systems for cooling and heating demands, and that drains energy from the battery. This paper summarizes a study of the Electric Propulsion Systems’ (EPS) Technology Readiness Level (TRL), a Theory of Inventive Problem Solving (TRIZ) trends of engineering system evolution, comparison with conventional aircraft/gas turbine configuration including their thermal management systems, and the impacts on type certification regulations. TRL shows hybrid-electric leads as a bridge between gas turbines and electric systems, followed by electric only propulsion due to slower battery technology breakthroughs, while distributed propulsion lags due to novel airframe and thermal challenges. TRIZ analysis suggests that integrating self-cooling, structural composite batteries, and distributed propulsion with intelligent thermal management can propel EPS to new heights. A comparison of the propulsion systems showed that the thermal management and materials selection will be the key focus areas. The regulatory authorities are adapting the airworthiness regulations to the ongoing changes, and more regulatory evolution is likely to keep up with these technological trends.]]></description>
      <pubDate>Tue, 23 Jun 2026 10:38:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2712167</guid>
    </item>
    <item>
      <title>AIA Recommendations for Ultrasound Inspection of New-Make Turbine Engine, Life-Limited Rotating Parts</title>
      <link>https://trid.trb.org/View/2663112</link>
      <description><![CDATA[The aero gas turbine industry has collaborated with the Federal Aviation Administration (FAA) to study and provide guidance regarding the inspection process for the subsurface volume of critical nickel-based engine hardware, through the Aerospace Industries Association (AIA) team AIA A-18-003. Data from across a broad spectrum in the industry is needed for this work since the probability of an uncontained rotor event from any cause has proven to be extremely low. Following an uncontained event from a melt anomaly in a nickel high pressure turbine (HPT) disk in 2016, industry teams including this team AIA A-18-003, team AIA A-18-004, the AIA Jet Engine Nickel Quality Committee (JENQC), and the AIA Rotor Integrity Steering Committee (RISC) have collected data and considered ways to improve rotor damage tolerance through improvements in inspection technologies, melting and manufacturing practices, and part design and lifing. This report documents the findings from the evaluation of Ultrasonic (UT) forging inspections. The inspection guidance and recommendations provided here are integral components of a broader damage tolerance strategy for critical parts. A comprehensive damage tolerance strategy includes part manufacturing, service management, and engineering design characteristics to effectively minimize potential threats. The position of AIA A-18-003 Team is that aircraft safety is enhanced by the inclusion of subsurface UT inspections. The most effective and desirable method to detect subsurface anomalies and remove defective material from the supply chain is through original equipment manufacturer (OEM) UT inspections of billets and forgings prior to finished part machining. Focusing on the UT inspection of forgings, anomaly detection capability could be enhanced beyond the current baseline by adopting a Multi Zone Multi Angle (MZMA) inspection approach. Evaluation and recommendations for the UT inspection of billets will be addressed in a separate report to be published later. Additionally, another opportunity to detect anomalies is visual inspection of the etched surface of forging and/or finish machined parts, as part of a series of inspection processes.]]></description>
      <pubDate>Thu, 12 Feb 2026 08:52:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/2663112</guid>
    </item>
    <item>
      <title>In-Service Ultrasonic Inspections for Turbine Engine, Life-Limited Rotating Parts</title>
      <link>https://trid.trb.org/View/2663111</link>
      <description><![CDATA[The aero gas turbine industry has collaborated with the Federal Aviation Administration (FAA) to study and provide guidance and make recommendations about the implementation of requirements for in-service, sub-surface inspections through the Aerospace Industries Association (AIA) team AIA A-18-004. Data from across a broad spectrum in the industry is needed for this work since the probability of an uncontained rotor event from any cause has proven to be extremely low. Following an uncontained event from a melt anomaly in a nickel high pressure turbine (HPT) disk in 2016, industry teams including this team, team AIA A-18-003, the AIA Jet Engine Nickel Consortium (JENQC), and the AIA Rotor Integrity Steering Committee (RISC) have collected data and considered ways to improve rotor damage tolerance through improvements in inspection technologies, melting and manufacturing practices, and part design and lifing. This report documents the data collected and the findings from the evaluation of in-service inspections. The inspection guidance and recommendations provided here are considered as part of a larger critical part damage tolerance strategy. A comprehensive damage tolerance strategy considers the part manufacture, service management, and engineering design characteristics in order to minimize threats. The position of AIA A-18-004 is that aircraft safety is augmented by the inclusion of subsurface, ultrasonic (UT) inspections. The most effective and desirable means to detect subsurface anomalies and cull suspect material is by original equipment manufacturer (OEM) UT inspection of the billet and forging prior to finished part machining. However, industry field experience suggests in-service UT inspection, implemented at piece part opportunity exposure, may also be helpful. Such in-service inspections provide the most value on large blade carrying HPT disks and some intermediate pressure turbine (IPT) disks while other component types are currently well served by the surface inspections already in place. For some specific applications, a part may be available for piece part inspection at multiple times within its service life. The in-service inspections should be conducted each time one of these safety critical parts is completely disassembled, unless otherwise agreed to with the Authority.]]></description>
      <pubDate>Thu, 12 Feb 2026 08:52:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/2663111</guid>
    </item>
    <item>
      <title>In-Flight Evaluation of Sustainable Hydrocarbon Fuels in Compression Ignition Aircraft Engines</title>
      <link>https://trid.trb.org/View/2639321</link>
      <description><![CDATA[As global air traffic is expected to increase significantly in the coming decades, reducing the associated climate impact requires scalable solutions. While alternative propulsion technologies such as electric and hybrid-electric systems might offer long-term potential, their current applicability remains limited due to low energy density, limited range and scalability, and system complexity. Consequently, thermodynamic propulsion systems – such as gas turbines and piston engines – are expected to remain dominant in the medium term. In this context, sustainable hydrocarbon-based aviation fuels represent a practical and necessary solution. Certified sustainable aviation fuel (SAF) pathways are currently approved exclusively for use in gas turbines, with certification standards tailored to turbine-specific requirements. Consequently, fuel properties such as cetane number and evaporation behavior are not included in existing specifications. However, when SAF-kerosene blends are used in compression ignition engines, the impact of these properties on ignition quality, combustion behavior, and emissions must be specifically evaluated. For this purpose, a flight test campaign was conducted using a fully instrumented Diamond DA42 aircraft, configured as a flying laboratory and equipped with serial-production piston engines. Two synthetic fuel variants were evaluated: one certified according to ASTM D7566-23a Annex A2 (HEFA SPK) and a second, Tall Oil derived fuel with a distinctly different molecular composition – characterized by an increased content of cycloparaffins and low aromatics content. The aircraft as a flying air lab was equipped with special engine measurement technology including high-pressure in-cylinder indication to analyze the impact of these differing fuel compositions on engine efficiency and combustion characteristics, including ignition delay and peak pressure. Furthermore, a mobile emission and particle number measurement system enabled the assessment of environmental performance under real flight conditions. Both fuels demonstrated significant reductions in thermal NOx formation due to their low aromatics content. However, no clear benefit was observed in total particle number (PN), likely due to a shift in the particle size distribution towards the nanoparticle regime.]]></description>
      <pubDate>Wed, 10 Dec 2025 16:10:06 GMT</pubDate>
      <guid>https://trid.trb.org/View/2639321</guid>
    </item>
    <item>
      <title>An Improved Cox Proportional Hazards Model for Reliability Analysis of Aviation Gas Turbines Considering Varying Environmental Conditions and Operational Settings</title>
      <link>https://trid.trb.org/View/2577342</link>
      <description><![CDATA[A reliable aviation gas turbine reduces maintenance costs and improves efficiency in the aerospace industry. The Cox proportional hazards model is widely used in reliability analysis to study the effect of multiple covariates on failure. Recent studies combine this model with machine learning to enhance gas turbine reliability analysis, often using environmental conditions, operational settings, and gas path parameters as covariates. However, these direct covariates may not fully capture gas turbine degradation due to the effects of fluctuating environmental conditions and operational settings. To address this issue, this paper proposes a method that employs machine learning to develop new covariates for the Cox proportional hazards model. Machine learning models a healthy turbine, generating covariates less affected by varying environmental conditions and operational settings, better representing gas turbine degradation. This approach addresses limitations in using traditional covariates and enhances the Cox model's ability to analyze reliability under varying working conditions. The method is validated with data from NASA’s C-MAPSS dataset, showing improved accuracy compared to the traditional Cox model.]]></description>
      <pubDate>Fri, 26 Sep 2025 13:39:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/2577342</guid>
    </item>
    <item>
      <title>Research on marine gas turbine acoustic signals anomaly detection method based on physical prior knowledge and spatial-temporal graph neural network</title>
      <link>https://trid.trb.org/View/2589504</link>
      <description><![CDATA[As a vital power system for modern vessels, the marine gas turbine requires intelligent condition monitoring to ensure safe and reliable navigation. Acoustic pressure signals, which serve as key health condition indicators of the gas turbine, are strongly influenced by operating conditions and environmental factors, exhibiting high temporal dependency and structural coupling-posing significant challenges for accurate modeling and anomaly detection. This paper proposes a novel health benchmark model (HBM) and anomaly detection method for acoustic pressure signals, which is based on physical prior knowledge and a spatio-temporal graph convolutional network (PPK-STGCN). The proposed framework integrates thermodynamic principles with deep learning techniques by constructing a hybrid graph architecture that combines a static structure derived from physical priors with a learnable, adaptive adjacency matrix. A Transformer encoder is employed to capture node-level temporal evolution patterns, while a graph convolutional network extracts spatial correlations among variables. Additionally, a composite loss function incorporating sparsity and information entropy regularization is designed to enhance the discriminative capability of the learned graph structure, improving both interpretability and generalization. The proposed method was validated using real marine gas turbine operation data. The results indicated that PPK-STGCN accurately predicted acoustic pressure under various operating conditions, with a mean absolute error of 0.98, a root mean square error of 1.18, and a mean absolute percentage error of 2.03 %. In terms of fault detection, the method demonstrated strong engineering applicability and fault detection capability, achieving an average accuracy of 99.96 % on the test set.]]></description>
      <pubDate>Wed, 24 Sep 2025 15:31:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/2589504</guid>
    </item>
    <item>
      <title>Investigation of Micro Gas Turbines Topped with Wave Rotors for a Hybrid Vehicle Range Extender Engine</title>
      <link>https://trid.trb.org/View/2600489</link>
      <description><![CDATA[Micro gas turbines are gaining renewed interest as range-extender engines in hybrid vehicles due to their superior power-to-weight ratio, fuel flexibility, and robust steady-state performance. However, their widespread adoption is hindered by modest efficiency and high component costs, particularly from recuperators. This study investigates the thermodynamic performance enhancement of two commercial micro gas turbines, the Capstone C-30 and C-60, through wave rotor integration as a topping device. Using Aspen Plus and Aspen Custom Modeler, three configurations were analyzed: a recuperated engine with a single wave rotor, and unrecuperated engines with a single and two cascaded wave rotors, respectively. Key performance metrics—including brake thermal efficiency, specific fuel consumption, and specific work—were evaluated across a range of wave rotor pressure ratios.Results show that the wave rotor significantly improves power output and pressure ratio while maintaining or improving thermal efficiency. The cascaded wave rotor configuration delivered the highest gains, with power output increased by up to 80–95% and BTE reaching 32.4%. However, this also introduced challenges such as high combustor outlet temperatures (>1400 K), raising the potential for NO? formation and increased system complexity. A detailed sensitivity analysis confirmed that the thermodynamic benefits scale with pressure ratio up to a threshold (WR ˜ 2.6–3.0), beyond which gains diminish. The study concludes that wave rotor-enhanced MGTs, particularly when coupled with catalytic combustors, present a potentially promising solution for high-performance, low-emission hybrid vehicle range extender applications.]]></description>
      <pubDate>Tue, 16 Sep 2025 11:12:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/2600489</guid>
    </item>
    <item>
      <title>Practical semi-supervised learning framework for real-time warning of aerodynamic instabilities: Applications from compressors to gas turbine engines</title>
      <link>https://trid.trb.org/View/2562671</link>
      <description><![CDATA[This study introduces a semi-supervised learning framework for the aerodynamic instability warning in gas turbine engines, emphasizing effectiveness, generalization, and practicality. The initial preprocessing involves low-pass filtering and downsampling to mitigate noise and high-frequency disruptions in the pressure signal at the compressor outlet. A 5 ms sliding time window then segments the pressure data, followed by the adaptive wavelet synchrosqueezed transform (AWSST) for sample labeling. To address significant dataset imbalance, an anomaly detection approach is adopted, incorporating feature selection with ReliefF and mutual information, a sparse autoencoder with bidirectional gated recurrent units (BiGRU-SAE), and a warning logic based on reconstruction errors and pressure drop amplitudes. The framework's effectiveness and generalization are evaluated across all datasets and validated through real-time warning experiments on a hardware-in-the-loop (HIL) simulation platform. Results show that this method detects instabilities 20 to 45 ms earlier than monitoring the pressure change rate, with a single-step computation time of approximately 3 ms, well within the requirements for real-time processing. This improvement in early detection can significantly enhance engine safety and performance. Notably, the method demonstrates generalizability across different states of the same engine and between different engines, suggesting its potential for developing a widely applicable warning model with limited data.]]></description>
      <pubDate>Thu, 14 Aug 2025 17:11:37 GMT</pubDate>
      <guid>https://trid.trb.org/View/2562671</guid>
    </item>
    <item>
      <title>AIA Recommendations Related to Gas Turbine Engine Overspeed Events from High Pressure Turbine Shaft Loss-of-Load</title>
      <link>https://trid.trb.org/View/2561911</link>
      <description><![CDATA[In 2015, the Federal Aviation Administration (FAA) requested the Aerospace Industries Association (AIA) form a voluntary advisory group related to gas turbine overspeed events resulting from shaft loss-of-load. Motivating the request at the time were engine applicant’s requests to be relieved of considering certain elements of the shaft system from failure consideration in determining the rotor terminal speed and rotor overspeed capability. These requests were based on the applicant’s assessment that the probability of these elements failing was extremely remote. The AIA advisory group formed under the Civil Aviation Regulatory & Safety (CARS) Committee consisted of seven major engine manufacturers, a major aircraft manufacturer along with the FAA, EASA, and Transport Canada Civil Aviation (TCCA). The group compiled high pressure turbine shaft failure data from 1970 to 2015 including primary cause of failure, type of failure, and several other data categories that helped inform the group’s recommendations regarding consideration of shaft element exclusion.]]></description>
      <pubDate>Tue, 17 Jun 2025 09:43:50 GMT</pubDate>
      <guid>https://trid.trb.org/View/2561911</guid>
    </item>
    <item>
      <title>Dynamics modeling and impact resistance study of the marine gas turbine isolation system</title>
      <link>https://trid.trb.org/View/2549432</link>
      <description><![CDATA[The isolation system, which protects the gas turbine by isolating the impact from the ship's hull when the ship is impacted, consists of a steel frame and isolation elements. A rate-dependent generalized Prandtl-Ishlinskii model is proposed and the mechanical models of the isolation elements are developed, which are verified by impact tests and found to have a maximum error of 3.05 % in relative displacement and 9.75 % in acceleration. The steel frame is discretized into multiple Timoshenko beam cells, and a stiffness matrix establishment method for spatial rigid-flexible coupling unit is proposed to establish the dynamics model of the isolation system. The maximum error in the natural frequency of the steel frame is found to be 8.44 % by comparing with the simulation results, and the maximum error in the natural frequency of the steel frame-gas turbine system is found to be −10.62 %. The impact dynamics calculations are completed based on the pseudo-force method, and the influence of the isolation elements arrangement on the isolation performance is analyzed in conjunction with the energy transfer between modes. The isolation system has the highest energy share for the 7th, 8th, and 11th order modes, and it does affect the energy share of each order mode when changing the number, position, and spacing of the isolation elements.]]></description>
      <pubDate>Tue, 27 May 2025 09:33:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/2549432</guid>
    </item>
    <item>
      <title>More Electric Engine Technologies towards the 2040s</title>
      <link>https://trid.trb.org/View/2552250</link>
      <description><![CDATA[Improvement and evolution of all aircraft technologies and the commercialization of new technologies are essential to the carbon-net-zero goal of air mobility. Passenger aircraft are required to provide the ultimate in comfort, economy, and safety, and gas turbine engines will not disappear, while promoting the conversion to SAF and hydrogen fuels. The More Electric Engine (or MEE) concept, which has been proposed since the late 2000s, is one alternative. This paper focuses on the electrification of engine accessories. When the concept of electrification of engine accessories was first presented at Aerotech 10 years ago, the discussion at Aerotech seemed to be negative. Attaching a motor to conventional engine accessories would obviously increase the weight. Next, the conventional engine accessories are centrally controlled and only FADEC is in command, but electrification of engine accessories will increase the cost by adding intelligence to all the accessories. On a more academic level, a complete solution for the multiplicity required to ensure safety has not yet been clearly defined. Currently, electrification of engine accessories is not on the list of practical scenarios as far as the authors are aware. MEE is not only a technology that simply replaces power with electricity but is also a necessary technology to improve performance while keeping up with the latest technologies. Electrification and intelligence are inseparable due to their physical characteristics, and various industrial machinery systems and mobility systems have been innovated to take advantage of this relationship. This paper summarizes the concept of MEE technology required for aircraft in the 2040s and beyond, and the research results necessary to realize it. Finally, the background of how MEE can be used as a useful technology in the practical application of SAF and hydrogen-based fuels, which are realistically required in the 2040s and beyond, is summarized.]]></description>
      <pubDate>Tue, 13 May 2025 10:20:04 GMT</pubDate>
      <guid>https://trid.trb.org/View/2552250</guid>
    </item>
    <item>
      <title>Morphologies and Structures of Liquid Fragments Derived from the Near-Field Zone of a Twin-Orifice Swirl Atomizer</title>
      <link>https://trid.trb.org/View/2539459</link>
      <description><![CDATA[Aviation gas turbine engines typically utilize twin-orifice swirl atomizers to achieve a fine spray, widen the spray cone angle, and shorten spray penetration. However, using twin-orifice atomizers complicates the spray structure, and knowledge of the spray, especially in the near-field nozzle zone, remains limited. This study experimentally investigates the morphologies and structure of liquid fragments in the near-field nozzle of a twin-orifice atomizer. A high-speed backlit experimental system was developed to examine the liquid fragment morphologies and structures. The fragments are classified into spherical droplets, ligaments, and other irregular structural fragments. Results show that with increasing the pressure in the near field of the nozzle, the proportion of nearly round fragments decreases with increasing pressure. In contrast, the proportion of ligament-like fragments tends to increase. Besides, the particle size distribution did not change significantly within the 10 to 50-bar pressure range. Understanding these morphologies and structures could aid in developing a secondary atomization model suitable for predicting the droplet size distribution generated by twin-orifice atomizers.]]></description>
      <pubDate>Tue, 15 Apr 2025 13:56:50 GMT</pubDate>
      <guid>https://trid.trb.org/View/2539459</guid>
    </item>
    <item>
      <title>Lattice Structure and Strut Thickness Optimization for Turbine Blade
                    Modal Parameters</title>
      <link>https://trid.trb.org/View/2511031</link>
      <description><![CDATA[
                
                This article explores the utilization of simple-cubic, diamond, octet-truss, and
                    X-type lattice structures for low-pressure turbine blades in engine turbines to
                    enhance natural frequency and decrease overall engine weight while maintaining
                    structural integrity. The research method involves analyzing polylactic acid
                    (PLA) hollow T106C blades with fully infilled and 50–80 location-based lattice
                    arrangements. The study modifies the strut thickness of lattice structures using
                    both constant and variable-based approaches and applies a generalized formula
                    based on relative density to evaluate how changes in lattice thickness and
                    arrangements influence natural frequencies. Furthermore, the investigation
                    extends to multi-lattice configurations, introducing a parameter ?? to
                    signify the transition between different lattices. The modified blades were 3D
                    printed using PLA and tested for natural frequencies through modal testing. The
                    results demonstrate that location-based 50–80 exponential-based lattice
                    structures combining octet-truss and X-type lattices yield the best performance,
                    achieving a 15% increase in the first mode and 14.6% in the second mode when
                    compared to hollow blade. In comparison, fully infilled 50–80 exponential-based
                    lattice structures with a combination of octet-truss and X-type lattices achieve
                    a 9.4% increase in the first mode and 12.7% in the second mode. These findings
                    highlight that lattice structures can effectively improve natural frequencies
                    across all modes.
            ]]></description>
      <pubDate>Tue, 18 Feb 2025 14:55:37 GMT</pubDate>
      <guid>https://trid.trb.org/View/2511031</guid>
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