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    <title>Transport Research International Documentation (TRID)</title>
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    <atom:link href="https://trid.trb.org/Record/RSS?s=PHNlYXJjaD48cGFyYW1zPjxwYXJhbSBuYW1lPSJkYXRlaW4iIHZhbHVlPSJhbGwiIC8+PHBhcmFtIG5hbWU9InN1YmplY3Rsb2dpYyIgdmFsdWU9Im9yIiAvPjxwYXJhbSBuYW1lPSJ0ZXJtc2xvZ2ljIiB2YWx1ZT0ib3IiIC8+PHBhcmFtIG5hbWU9ImxvY2F0aW9uIiB2YWx1ZT0iMCIgLz48L3BhcmFtcz48ZmlsdGVycz48ZmlsdGVyIGZpZWxkPSJpbmRleHRlcm1zIiB2YWx1ZT0iJnF1b3Q7SHlkcmF1bGljIGZsdWlkcyZxdW90OyIgb3JpZ2luYWxfdmFsdWU9IiZxdW90O0h5ZHJhdWxpYyBmbHVpZHMmcXVvdDsiIC8+PC9maWx0ZXJzPjxyYW5nZXMgLz48c29ydHM+PHNvcnQgZmllbGQ9InB1Ymxpc2hlZCIgb3JkZXI9ImRlc2MiIC8+PC9zb3J0cz48cGVyc2lzdHM+PHBlcnNpc3QgbmFtZT0icmFuZ2V0eXBlIiB2YWx1ZT0icHVibGlzaGVkZGF0ZSIgLz48L3BlcnNpc3RzPjwvc2VhcmNoPg==" rel="self" type="application/rss+xml" />
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    <language>en-us</language>
    <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>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
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    <item>
      <title>Investigation of Fatigue Failure Mechanisms in High-Pressure Hydraulic Pipes of Power Steering Systems</title>
      <link>https://trid.trb.org/View/2663464</link>
      <description><![CDATA[The high-pressure steering hose in a hydraulic steering system carries pressurized hydraulic fluid from the power steering pump to the steering gear (or steering rack). Its main function is to transmit the force generated by the pump so that the hydraulic pressure assists the driver in turning the wheels more easily. The high-pressure hydraulic pipeline in the power steering system is a vital component for ensuring optimal performance. During warranty analysis, leakage incidents were observed at the customer end within the warranty period. The primary factors contributing to these failures include pipe material thickness, material composition, mechanical properties, and engine-induced vibrations. This study investigates fatigue-related failures through detailed material characterization and Computer-Aided Engineering (CAE) based on real world usage road load data collected. The objective is to identify the root causes by examining the influence of varying pipe thickness on fatigue life.The investigation discovered that crack initiation predominantly occurred on the concave side of bent pipe sections, specifically on the engine-side high-pressure steering line, which is connected to the power steering pump mounted on the engine. Fracture surfaces exhibited characteristics consistent with fatigue failure, with crack propagation primarily oriented longitudinally along the pipe. The highest tangential stresses were observed on the out word, resulting from the combined effects of internal hydraulic pressure and vibrational loads. Fatigue cracks originated from the inner surface and propagated outward under cyclic stresses induced by pressure fluctuations and engine vibrations during vehicle operation on the road.Computer-Aided Engineering (CAE) simulations indicated that the failure mechanism was primarily attributable to an incorrect material thickness selection during the development phase. Modifications to the pipe design, including increased material thickness, were implemented, leading to improved performance in subsequent testing. The high-pressure hydraulic pipeline exhibits decreased failure rates and improved reliability and durability following the implementation of the revised design.]]></description>
      <pubDate>Mon, 02 Feb 2026 16:36:56 GMT</pubDate>
      <guid>https://trid.trb.org/View/2663464</guid>
    </item>
    <item>
      <title>The Method of Thermal Calculation of the Aircraft Hydraulic System, Taking into Account Heat Losses at the Power Unit</title>
      <link>https://trid.trb.org/View/2407949</link>
      <description><![CDATA[In this paper, the authors propose the method for thermal calculation of the hydraulic system of a combat aircraft. This method takes into account the heating of hydraulic fluid in spool valves of control system actuators, depending on external load on actuators and the control surfaces slew rate. In contrast to the existing methods, the change in pump heat rejection is determined depending on the aircraft engine rotor speed.]]></description>
      <pubDate>Mon, 14 Jul 2025 12:53:28 GMT</pubDate>
      <guid>https://trid.trb.org/View/2407949</guid>
    </item>
    <item>
      <title>Aircraft Air Quality and Bleed Air Contamination Detection [supporting datasets]</title>
      <link>https://trid.trb.org/View/2543096</link>
      <description><![CDATA[The purpose of this project was to provide a data-driven process to identify sensing technology with good potential for detecting bleed air contamination from engine oil, hydraulic fluid, or deicing fluid. Reports from major aircraft cabin air studies were reviewed to identify the range of constituents that can be expected in cabin air, especially as they pertain to the aforementioned contaminants and their potential markers. One of the projects was the National Aeronautics and Space Administration Vehicle Integrated Propulsion Research (NASA-VIPR) project where controlled amounts of engine oil were injected into the engine compressor of a C-17 transport aircraft and the resulting contaminants in the bleed air measured. Three additional cabin air quality studies conducted on revenue flights were reviewed. These three studies provide data for a combined total of 249 flights on a variety of makes and models of aircraft. These studies provide adequate documentation of typical aircraft cabin air. Information from this review was used to identify potential markers of the bleed air contaminants. Additionally, collaboration was established with several technical committees from the Society of Automotive Engineers (SAE), American Society of Heating, Air- Conditioning and Refrigerating Engineers (ASHRAE), and American Society for Testing and Materials (ASTM) technical committees and with project personnel from the prior European Union Aviation Safety Administration (EASA)-funded cabin air study. There was extensive interaction with SAE E31b and a formal collaboration agreement was established between ASHRAE research project 1830-RP and Kansas State University. Two industry webinars where held to obtain industry input and participation in the industry working group that was formed. Key objectives of the project were to identify sensors and sensing technology with potential for detection of one or more of the three aforementioned bleed air contaminants and to develop a plan for test stand engine experiments to evaluate the sensors with controlled amounts of the three contaminants. Sensors and instruments were identified and a test plan was developed. The detailed plan describing contaminants, rates, and operating conditions is presented in Section 4.11 of this report and instruments recommended for testing are described in Section 5.2. Additionally, through the collaboration with ASHRAE 1830 and the support of the industry working group, many of the experiments identified in the test plan were completed.]]></description>
      <pubDate>Wed, 23 Apr 2025 14:47:34 GMT</pubDate>
      <guid>https://trid.trb.org/View/2543096</guid>
    </item>
    <item>
      <title>Design and Diagnostics Features of Automatic Transmissions of the GM 6T Family</title>
      <link>https://trid.trb.org/View/2539493</link>
      <description><![CDATA[Automatic transmission (AT) is a complex hydroelectromechanical system, since it consists of hydraulic, electrical and mechanical parts.On cars produced by “UzAuto Motors” mainly AT of the 6T family, 6-speed AT family GM: 6T30, 6T40, 6T45, 6T50 “Hydra-Matic” are used.Production of parts of these transmissions is carried out both at American GM plants and at GM plants in China and Korea.The differences between AT 6T30/6T40/6T45/6T50 are in the thickness of the output chain and in the planetary gear, in the sizes of some other units and the housing itself. But the differences are much more influenced by the settings of the transmission unit, which select operating modes with different engines so as not to overload the thinnest places of the automatic transmission.Automatic transmissions 6T30, 6T40, 6T45, 6T50 have the ability to manually shift gears and activate the “kickdown” mode (for quick acceleration of the car, when you sharply press the gas “all the way” it makes the automatic transmission downshift, and sometimes by two steps).The operation of the transmission is controlled by various electronic systems that are responsible for the operability and structural integrity of the gearbox.Failure of the automatic transmission can occur as a result of one or a combination of malfunctions of the following parts: in the torque converter; in the mechanical part of the gearbox; in the hydraulic part of the control system; one or more clutches of the gearbox; in the electrical part of the control system; in the electronic control unit.The authors of the work investigated and determined the occurrence of malfunctions and failures depending on the temperature of the working fluid of the automatic transmission of a passenger car.Also, the dependence of the resource of the automatic transmission on the temperature of the hydraulic fluid was obtained. High-quality diagnostics of the automatic transmission and its control system can in many cases save the car owner from expensive repairs:]]></description>
      <pubDate>Tue, 15 Apr 2025 13:56:50 GMT</pubDate>
      <guid>https://trid.trb.org/View/2539493</guid>
    </item>
    <item>
      <title>Experimental Approach to Water Hammer Phenomenon</title>
      <link>https://trid.trb.org/View/2407961</link>
      <description><![CDATA[The paper indicates the frequent occurrence of transient states in hydraulic systems. Particular attention was paid to the phenomenon of water hammer - the causes and effects of this phenomenon. The necessity to modify the theoretical description of this phenomenon was indicated. The work focuses on the presentation of the development of the structure of experimental stands to study the phenomenon of water hammer. The research results obtained on the presented experimental stands were used to verify the theoretical considerations presented in other papers by the authors. The presented successive concepts of the test stand enable the research to be carried out to a greater extent and at the same time eliminate the disadvantages of the previous versions of the test stand. The stand presented as the final one also allows the testing of transients in hydraulic lines for various types of working fluid (oil, emulsion, distilled water).]]></description>
      <pubDate>Wed, 20 Nov 2024 13:08:59 GMT</pubDate>
      <guid>https://trid.trb.org/View/2407961</guid>
    </item>
    <item>
      <title>Aircraft Air Quality and Bleed Air Contamination Detection: Engine Stand Tests, Sensor Technologies and Chemical Sampling (Phase 2, Volume 1)</title>
      <link>https://trid.trb.org/View/2371292</link>
      <description><![CDATA[The purpose of this project was to provide a data-driven process to identify sensing technology with good potential for detecting bleed air contamination from engine oil, hydraulic fluid, or deicing fluid. An on-wing test was conducted in February 2022. A test on an engine test bed was conducted in May 2022. Sensors and instruments were identified, and a test plan was developed. Testing was conducted over a period of approximately one week. Results from this test with respect to sensor ability to detect bleed air contaminants was used on-wing tests performed in 2023. Data analysis for the testing in 2023 is ongoing and will appear in a separate report. Key objectives of the project are to identify sensors and sensor technology with the potential to detect one or more of the three aforementioned bleed air contaminants. Supporting data for this report can be accessed with the following link: https://doi.org/10.21949/1528260.]]></description>
      <pubDate>Mon, 29 Apr 2024 09:08:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2371292</guid>
    </item>
    <item>
      <title>Design and Development of Base Valve for a Semi-Active Damper</title>
      <link>https://trid.trb.org/View/2367888</link>
      <description><![CDATA[A semi-active suspension system provides superior safety, ride, and handling performance for a vehicle by continuously varying the damping based on vehicle motions, where semi-active hydraulic damper (SAHD) is the most critical component. Today, SAHD’s are standard in most of the premium segments of vehicles and optional extras in mid-size and compact vehicle segments. Electric vehicles require larger sized SAHD’s to meet heavier vehicle loads and meet ride and handling requirements. The aim of this paper is to highlight the design and development methodology of a base valve for larger bore-size for semi-active hydraulic damper. The workflow follows to present a process for base valve design to meet structural strength and, the key steps of design calculations of the hydraulic performance. The design of the base valve and suction disks architecture was engineered with the aid of Computer Aided simulations. The structural performance was analyzed using the Finite Element Analysis (FEA) and valve hydraulic performance factors were obtained by using Computational Fluid Dynamics (CFD) methods to simulate the physics of hydraulic fluid flow around the base valve assembly using the de-coupled fluid /structure interaction (FSI) method. In this effort, the analytical study was reinforced to identify the critical performance parameters such hydraulic pressure (P) - oil discharge (Q) curve generation and understand the base valve design performance. Furthermore, valve characterization using flow bench testing was conducted to validate and correlate the simulation predictions with prototype samples to increase the confidence level in computer aided simulations.]]></description>
      <pubDate>Tue, 16 Apr 2024 09:52:56 GMT</pubDate>
      <guid>https://trid.trb.org/View/2367888</guid>
    </item>
    <item>
      <title>Analysis of low frequency response characteristics of multi-inertia channel hydraulic mounts</title>
      <link>https://trid.trb.org/View/2232121</link>
      <description><![CDATA[This paper investigates the effects of the number and length of inertia channels and different cross-sectional areas on the low-frequency characteristics of hydraulic mounts. Firstly, it analyses the isolation of low frequency-large amplitude excitation hydraulic mounts relying mainly on inertial channels. Secondly, nine different structures of inertia channels are proposed and the mathematical model of hydraulic mounts is obtained using an equivalent mechanical method. Finally, the hydraulic mounts system model of the 1/4 vehicle model is built to analyse the effect of different inertia channels on the mounts' vibration isolation performance under road excitation. It has been shown that changing the number of inertia channels as well as the cross-sectional area can regulate the peak and peak frequency of the dynamic stiffness and loss angle of the hydraulic mounts.]]></description>
      <pubDate>Mon, 25 Sep 2023 14:46:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/2232121</guid>
    </item>
    <item>
      <title>1D Modelling of Thermal Management of a Jet Trainer
                    Aircraft</title>
      <link>https://trid.trb.org/View/2140062</link>
      <description><![CDATA[Most of current jet aircraft circulate fuel on the airframe to match heat loads                     with available heat sink. The demands for thermal management in wide range of                     air vehicle systems are growing rapidly along with the increased mission power,                     vehicle survivability, flight speeds, and so on. With improved aircraft                     performance and growth of heat load created by Aircraft Mounted Accessory Drive                     (AMAD) system and hydraulic system, effectively removing the large amount of                     heat load on the aircraft is gaining crucial importance. Fuel is becoming heat                     transfer fluid of choice for aircraft thermal management since it offers                     improved heat transfer characteristics and offers fewer system penalties than                     air. In the scope of this paper, an AMESim model is built which includes                     airframe fuel and hydraulic systems with AMAD gearbox of a jet trainer aircraft.                     The integrated model will be evaluated for thermal performance. JP-8 fuel is                     recirculated on the airframe to maintain cooling the oil for AMAD gearbox and                     the hydraulic fluid for the hydraulic systems. A Fuel/Oil Heat Exchanger (FOHE)                     is integrated on the airframe main fuel line with a thermally actuated valve                     located at the fuel outlet port, which prevents fuel temperature from exceeding                     limitations at the airframe/engine fuel interface. The valve opens at a                     specified fuel temperature allowing excessive fuel to return to main fuel tank                     that increase fuel flow through the heat exchanger. AMAD and hydraulic systems                     also have their own thermal by-pass valves to adjust fluid quantity to be sent                     to the heat exchanger for cooling.]]></description>
      <pubDate>Mon, 20 Mar 2023 16:14:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/2140062</guid>
    </item>
    <item>
      <title>Aircraft contaminated air: a brief outline</title>
      <link>https://trid.trb.org/View/2011862</link>
      <description><![CDATA[Aircraft bleed air supplies contaminated by engine oil dates back to the early 1950s. Aircraft and engine/APU design utilising unfiltered bleed air to supply the breathing air in aircraft explains the mechanism by which the air supply routinely becomes contaminated with low levels of a complex mixture of jet oils and hydraulic fluids in normal operation. Exposure to these contaminants is increasingly recognised as a flight safety issue as well as an occupational health problem, with impairment in flight not uncommon. Maintenance investigation techniques are less effective in identifying the more frequent low level oil leakage events with repeat events occurring. Over the last two decades, there have been an increasing number of international activities looking into bleed air contamination. It is necessary for the aviation industry to take a closer look at fume events linked to the supply air and introduce mitigating strategies.]]></description>
      <pubDate>Thu, 27 Oct 2022 13:47:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/2011862</guid>
    </item>
    <item>
      <title>Study of Low Viscosity ATF with Extending Gear Fatigue Life</title>
      <link>https://trid.trb.org/View/1812897</link>
      <description><![CDATA[Although it has been reported that the increase of base oil viscosity and the selection of suitable VII (Viscosity Index Improver) are key factors to improve metal fatigue life for the development of low viscosity ATF, the problem of gear fatigue life has not been perfectly solved. In this study, the effect of VII on gear fatigue life was evaluated by using EHD film thickness measurement and the block on ring friction tester. Based on the study, the low viscosity ATF that has good anti-pitting performance in gears can be proposed by optimizing the combination of base oil and VII.]]></description>
      <pubDate>Mon, 26 Sep 2022 09:12:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/1812897</guid>
    </item>
    <item>
      <title>Improving Spool Valve Operating Effort Using CFD</title>
      <link>https://trid.trb.org/View/1802147</link>
      <description><![CDATA[Hydraulic oil flow and flow induced forces inside hydraulic spool valves have been studied using a commercially available Computational Fluid Dynamics (CFD) software package with an aim of improving hydraulic spool valve operating efforts. The main objective is to investigate flow induced forces on the spool with a range of different geometries or operating conditions and therefore to minimize or utilize their effect on spool effort. This CFD problem was treated as incompressible, turbulent, steady and adiabatic or isothermal. Integration of solved pressure field from a commercial CFD solution over related a valve component surface area was used to integrate the desirable flow induced forces. Additional viscous drag forces on the spool effect on total spool operating effort have also been investigated. The focus in this article is mainly based on studies for open center flow type four-way spool valves in cases such that the hydraulic oil flow direction towards spool. Some other spool metering cases will also be presented. CFD results are compared to experimental results with overall good correlation.]]></description>
      <pubDate>Mon, 29 Aug 2022 11:32:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/1802147</guid>
    </item>
    <item>
      <title>Dynamic Characteristics of a Full Car Fitted with Torsion-Eliminating Hydraulically Interconnected Suspension</title>
      <link>https://trid.trb.org/View/1829813</link>
      <description><![CDATA[In this paper, a torsion-eliminating Hydraulically Interconnected Suspension (THIS) is proposed for the first time to reduce the undesired articulation (warp) stiffness of a two-axis vehicle. The dynamic characteristics of a typical sport utility vehicle (SUV) fitted with the THIS is investigated in the frequency domain. The equations of motion of the coupled mechanical and hydraulic sub-systems are presented. The vehicle basic mechanical sub-system is modeled as a 7 degrees of freedom (DOF) mass-spring-damper system. The hydraulic impedance method is employed to model the fluid sub-system. The relationships between the dynamic fluid states, i.e. pressures and flows, are determined by transfer matrices. Then the mechanical and hydraulic sub-systems are coupled through the mechanical-fluid boundary conditions. Based on fluid hydraulic impedance method, the characteristic equations of this mechanically and hydraulically coupled system are derived with a state vector including the displacements and velocities of mechanical system and the pressure at the mechanical-hydraulic boundary section.]]></description>
      <pubDate>Mon, 25 Apr 2022 10:07:37 GMT</pubDate>
      <guid>https://trid.trb.org/View/1829813</guid>
    </item>
    <item>
      <title>Novel, Compact Devices for Reducing Fluid-Borne Noise</title>
      <link>https://trid.trb.org/View/1823445</link>
      <description><![CDATA[Hydraulic systems pose a particular problem for noise control. Due to the high speed of sound in hydraulic fluids, components typically designed to reduce fluid-borne noise can easily exceed practical size constraints. This paper presents novel solutions to creating compact and effective noise control devices for fluid power systems. A hydraulic silencer is presented that utilizes a voided polymer lining in lieu of a pressurized bladder. Theoretical modeling is developed which predicts device performance and can assist in future design work. Experimental results are presented to demonstrate the performance of the device. Both voided and non-voided liners are tested to show the effect of the voiding on the performance. In addition, theoretical modeling and experimental results are presented for a prototype Helmholtz resonator that is two orders of magnitude smaller than previously developed devices.]]></description>
      <pubDate>Wed, 23 Feb 2022 16:16:11 GMT</pubDate>
      <guid>https://trid.trb.org/View/1823445</guid>
    </item>
    <item>
      <title>Optimum Solution for Reduction of Clutch Pedal Vibration and Groan Noise Observed During Clutch Pedal Actuation</title>
      <link>https://trid.trb.org/View/1889452</link>
      <description><![CDATA[In emerging markets like India, manual transmission vehicles are still most preferred & contributes to 85% of passenger vehicle sales due to its cost benefit. However, customer expects good NVH behavior for comfortable driving experience in the vehicle to maneuver effortlessly in the highly congested traffic conditions in India. Clutch & its hydraulic release system in manual transmission of IC engines are the significant components which affects the NVH behavior & maneuverability of the vehicle and the driver comfort significantly. This paper focuses on the clutch pedal vibration & groan noise concern observed during clutch pedal actuation in high power density SUV vehicle developed for Indian market. The vehicle had highly efficient & light weight engine which has high engine axial vibrations. Axial vibrations are caused due to engine firing impulses & crankshaft bending causes flywheel axial movement. This movement in turn leads to vibrations in clutch cover diaphragm fingers which are transmitted to clutch pedal through hydraulic fluid pulsation via clutch release system which comprises of CSC, bleeder, clutch high pressure pipe & CMC. Engine vibrations which are transferred through clutch system to clutch pedal is felt on driver foot and causing discomfort during clutch pedal actuation/modulations while launching, creeping and for shifting of the gears in the vehicle. During pedal actuations at higher rpm for shifting gears, low frequency vibrations becomes high frequency and heard as groan noise inside the passenger cabin which results in uneasiness to driver and passengers. This paper describes the literature available, root cause analysis of the concern, effect of clutch disc, cover assembly, hydraulic release system design variables and the optimum solution which does not affect the other performance of the clutch function while reducing the clutch pedal vibration & groan noise concern through simulation & vehicle measurement results.]]></description>
      <pubDate>Thu, 09 Dec 2021 10:39:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/1889452</guid>
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