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Author: Edgar Streit Publisher: ISBN: Category : Bearing repair Languages : en Pages : 13
Book Description
Refurbishment of aerospace gas turbine engine bearings is a well established process regularly used to ensure asset availability. Repairs typically follow four well established basic levels. Level one generally requires detailed inspection in accordance with agreed criteria. Level two commonly involves replacement of rolling elements, refinishing of raceway surfaces and re-plating of bearing cages as appropriate. Level three involves the use of raceway grinding in the event that standard honing is insufficient to achieve required product quality. Level four is reserved for cases where one of the bearing rings is replaced. Results from detailed study of product following completion of full scale testing, repair per levels two and four, and continued testing is presented herein. Results demonstrate the absence of subsurface fatigue propagation. Test results conclude the commonly recognized acceptability of the repair methods noted and further support previously published theories regarding infinite fatigue theory. Reference to previously published findings describing expected symptoms of subsurface fatigue propagation are reviewed to support findings.
Author: Edgar Streit Publisher: ISBN: Category : Bearing repair Languages : en Pages : 13
Book Description
Refurbishment of aerospace gas turbine engine bearings is a well established process regularly used to ensure asset availability. Repairs typically follow four well established basic levels. Level one generally requires detailed inspection in accordance with agreed criteria. Level two commonly involves replacement of rolling elements, refinishing of raceway surfaces and re-plating of bearing cages as appropriate. Level three involves the use of raceway grinding in the event that standard honing is insufficient to achieve required product quality. Level four is reserved for cases where one of the bearing rings is replaced. Results from detailed study of product following completion of full scale testing, repair per levels two and four, and continued testing is presented herein. Results demonstrate the absence of subsurface fatigue propagation. Test results conclude the commonly recognized acceptability of the repair methods noted and further support previously published theories regarding infinite fatigue theory. Reference to previously published findings describing expected symptoms of subsurface fatigue propagation are reviewed to support findings.
Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781722393229 Category : Languages : en Pages : 58
Book Description
The results of an investigation are described for fatigue reliability in engine structures. The description consists of two parts. Part 1 is for method development. Part 2 is a specific case study. In Part 1, the essential concepts and practical approaches to damage tolerance design in the gas turbine industry are summarized. These have evolved over the years in response to flight safety certification requirements. The effect of Non-Destructive Evaluation (NDE) methods on these methods is also reviewed. Assessment methods based on probabilistic fracture mechanics, with regard to both crack initiation and crack growth, are outlined. Limit state modeling techniques from structural reliability theory are shown to be appropriate for application to this problem, for both individual failure mode and system-level assessment. In Part 2, the results of a case study for the high pressure turbine of a turboprop engine are described. The response surface approach is used to construct a fatigue performance function. This performance function is used with the First Order Reliability Method (FORM) to determine the probability of failure and the sensitivity of the fatigue life to the engine parameters for the first stage disk rim of the two stage turbine. A hybrid combination of regression and Monte Carlo simulation is to use incorporate time dependent random variables. System reliability is used to determine the system probability of failure, and the sensitivity of the system fatigue life to the engine parameters of the high pressure turbine. 'ne variation in the primary hot gas and secondary cooling air, the uncertainty of the complex mission loading, and the scatter in the material data are considered. Cruse, Thomas A. and Mahadevan, Sankaran and Tryon, Robert G. Glenn Research Center...
Author: Paul F. Brown Publisher: ISBN: Category : Ball-bearings Languages : en Pages : 76
Book Description
Rolling element fatigue life testers, as well as full-scale bearing testers, were used to develop a highly rolling contact fatigue resistant powder processed material (P/M) for use in aircraft turbine engine bearings. Ball and rod elemental tests were conducted, for screening purposes, on three P/M alloys; M-50, T-15 and CRB-7. The best results were realized with the P/M CRB-7 material, a 14 percent chrome corrosion resistant alloy, which demonstrated a B10 life almost twice that of the baseline, conventionally processed VIM-VAR M-50. Twenty full-scale 140 mm ball bearings were subsequently fabricated from P/M CRB-7 alloy. The B10 life realized with these bearings was equivalent to that expected from these same bearings had they been made from conventional VIM-VAR M-50 material. This good result was achieved in spite of an inner ring land wear problem which was alleviated by plating the lands with hard nickel. (Author).
Author: S. Gray Publisher: ISBN: Category : Languages : en Pages : 108
Book Description
A study was performed for a high temperature solid lubricated ball bearing under conditions representative of a gas turbine engine. The performance predictions were compared to the experimental test behavior of complete ball bearings and showed good correlation. In the pin on disc type material sliding tests, the friction and wear performance of M-50, NC-132, and alpha silicon carbide pairs with HAC-1 type lubricant composite were determined. In the first test mode -- to simulate the interactions between the cage material and other bearing elements -- the pairing of HAC-1 with M-50 and NC-132 at conditions up to 30,000 rpm and 316 C showed that the HAC-1 and NC-132 pair gave the lowest friction and wear and more stable temperatures. In the second test mode--to simulate low speed skidding which occurs between the ball and race materials--rapid wear was found and friction was high. This test data was used to prepare traction coefficient models as input to the ADORE computer program for bearing performance simulation. The analysis predicted that due to the high traction coefficients, the interactive forces are quite large, erratic, and inducive to cage wear and breakage. The good agreement with full scale testing of bearings demonstrated the significance of this combined material evaluation computer modeling technique. Keywords: solid lubricant composites; high temperature ceramics.
Author: P. F. Brown Publisher: ISBN: Category : Languages : en Pages : 90
Book Description
Work under this contract has demonstrated that powder processed bearing steels can be prepared to cleanliness standards consistent with the quality attainable in conventionally vacuum melted bearing steels, and that these alloys can be heat treated and processed into balls of aircraft quality. Rolling contact fatigue testing of three powder processed alloys in laboratory test devices has been completed and results revealed that an experimental alloy, EX00007, essentially a stainless steel composition, exhibited a fatigue life that was 2.2 times greater than that obtained in tests of powder processed M-50 alloy and 1.8 times the life observed for similar tests of VIM-VAR M-50 steel. On the basis of this performance, a recommendation has been made that a sufficient quantity of powder processed EX00007 alloy be procured for fabrication into aircraft gas turbine mainshaft bearings for subsequent endurance testing. (Author).
Author: Kendall R. Swenson Publisher: ISBN: Category : Languages : en Pages : 58
Book Description
The report contains a summary of the design analysis, development testing, and demonstration testing performed to demonstrate the feasibility of using gas lubricated hydrodynamic bearings in a gas turbine environment. The gas generator portion of the jet fuel starter used on the A7D aircraft was modified to incorporate compliant-foil gas bearings and subjected to varied demonstration test. In addition, engine starts were made under conditions which simulated normal starting gear loads. Results of the testing were very satisfactory. It is concluded that gas lubricated bearings can be used in a gas turbine application and further testing is encouraged. (Author).
Author: Publisher: ISBN: Category : Languages : en Pages : 10
Book Description
Development of practical and verifiable prognostic approaches for gas turbine engine bearings will play a critical role in improving the reliability and availability of legacy and new acquisition aircraft engines. In addition, upgrading current United States Air Force (USAF) engine overhaul metrics based strictly on engine flight hours (EFH) and total accumulated cycles (TAC) with higher fidelity prognostic models will provide an opportunity to prevent failures in engines that operate under unusually harsh conditions, and will help avoid unnecessary maintenance on engines that operate under unusually mild conditions. A comprehensive engine bearing prognostic approach is presented in this paper that utilizes available sensor information on-board the aircraft such as rotor speed, vibration, lube system information and aircraft maneuvers to calculate remaining useful life for the engine bearings. Linking this sensed data with fatigue-based damage accumulation models based on a stochastic version of the Yu-Harris bearing life equations with projected engine operation conditions is implemented to provide the remaining useful life assessment. The combination of health monitoring data and model-based techniques provides a unique and knowledge rich capability that can be utilized throughout the bearing's entire life, using model-based estimates when no diagnostic indicators are present and using the monitored features such as oil debris and vibration at later stages when failure indications are detectable, thus reducing the uncertainty in model-based predictions. A description and initial implementation of this bearing prognostic approach is illustrated herein, using bearing test stand run-to-failure data and engine test cell data.
Author: Publisher: ISBN: Category : Languages : en Pages : 56
Book Description
The Bulletin of the Atomic Scientists is the premier public resource on scientific and technological developments that impact global security. Founded by Manhattan Project Scientists, the Bulletin's iconic "Doomsday Clock" stimulates solutions for a safer world.
Author: Povl Brondsted Publisher: Elsevier ISBN: 0857097288 Category : Technology & Engineering Languages : en Pages : 485
Book Description
Wind energy is gaining critical ground in the area of renewable energy, with wind energy being predicted to provide up to 8% of the world’s consumption of electricity by 2021. Advances in wind turbine blade design and materials reviews the design and functionality of wind turbine rotor blades as well as the requirements and challenges for composite materials used in both current and future designs of wind turbine blades. Part one outlines the challenges and developments in wind turbine blade design, including aerodynamic and aeroelastic design features, fatigue loads on wind turbine blades, and characteristics of wind turbine blade airfoils. Part two discusses the fatigue behavior of composite wind turbine blades, including the micromechanical modelling and fatigue life prediction of wind turbine blade composite materials, and the effects of resin and reinforcement variations on the fatigue resistance of wind turbine blades. The final part of the book describes advances in wind turbine blade materials, development and testing, including biobased composites, surface protection and coatings, structural performance testing and the design, manufacture and testing of small wind turbine blades. Advances in wind turbine blade design and materials offers a comprehensive review of the recent advances and challenges encountered in wind turbine blade materials and design, and will provide an invaluable reference for researchers and innovators in the field of wind energy production, including materials scientists and engineers, wind turbine blade manufacturers and maintenance technicians, scientists, researchers and academics. Reviews the design and functionality of wind turbine rotor blades Examines the requirements and challenges for composite materials used in both current and future designs of wind turbine blades Provides an invaluable reference for researchers and innovators in the field of wind energy production
Author: Edgar Streit
Author: Edgar Streit
Author: National Aeronautics and Space Administration (NASA)
Author: Paul F. Brown
Author: 
Author: S. Gray
Author: P. F. Brown
Author: Kendall R. Swenson
Author: 
Author: 
Author: Povl Brondsted