Robert Tryon - Academia.edu (original) (raw)
Papers by Robert Tryon
Volume 3B: General, 1993
The reliability of a gas turbine engine structure is affected by the uncertainties in the operati... more The reliability of a gas turbine engine structure is affected by the uncertainties in the operating environment (speed, temperature etc.) as well as in the structural properties (material properties, geometries, boundary conditions etc.). A computational method for accurate reliability estimation under such uncertainties is described in this paper. Reliability computation for individual failure modes (burst, LCF etc.) as well as overall system failure is addressed. System failure probability is computed through the union of individual mode failures. The method also provides precise sensitivity information about the effect of each uncertain parameter on the individual failure probabilities as well as on the system failure probability. Such quantitative information helps rational design decisions as well as risk assessment and certification.
Electron beam melting (EBM) is a powder-bed fusion metal additive manufacturing technique that pr... more Electron beam melting (EBM) is a powder-bed fusion metal additive manufacturing technique that produces fully dense and complex parts directly from a computer aided design (CAD) model and was originally developed by Arcam AB. Unique to this additive manufacturing method, the Arcam EBM systems use a high powered electron beam to selectively melt powder to build a part layer-by-layer. The EBM technology is of particular interest to the aerospace [1], biomedical [2], and automotive [3] industries for its ability to create highly complex parts with high resolution and low lead times with goals of increasing efficiency and reducing part counts. According to Arcam, the EBM system is capable of processing a variety of alloys including Inconel 718, Cobalt-Chrome, and Ti-6Al-4V. The majority of research is devoted to Ti-6Al-4V. Ti-6Al-4V is a commonly used Ti alloy for its combination of strength, corrosion resistance, toughness, and workability [4]. Ti-6Al-4V is often used in aerospace applications, like wing attachments [5] where high strength and fatigue-damage tolerance are needed. Despite the outstanding mechanical properties, Ti-6Al-4V is difficult to machine and process so the costs limit its use in industry. With the ever-present push towards lighter and more efficient aircraft, reducing the cost of Ti-6Al-4V components is a priority for the aerospace industry. A promising method is additive manufacturing, specifically EBM. The EBM manufacturing is well suited for Ti-6Al-4V because of its processing conditions. EBM is under rough vacuum during the build process and because Ti-6Al-4V is highly reactive with elements in air, melt related defects can be avoided. In addition, EBM is capable of producing near-net shape components directly so that possible machining defects and scrap material can be reduced and nearly eliminated. The elevated build chamber temperature acts as an in-situ anneal reducing residual stresses to only 5-10% of the ultimate tensile strength [6] and effectively decomposing the hard but brittle α´ martensite phase produced by a rapid cooling rate [7], both of which are present in the as-built Ti-6Al-4V processed by laser AM systems [8]. Because residual stresses, machining defects, and melt defects can all negatively affect fatigue behavior, EBM appears to be a viable alternative to traditional manufacturing methods for Ti-6Al-4V fatigue critical components. However, because it is a new technology, a number of novel variables, process conditions, settings, and their effects on microstructure and then fatigue behavior must be understood before the widespread use. Process parameters have an impact on the microstructure of the finished parts and then corresponding mechanical properties. Research has shown that tensile properties and hardness can vary depending on the build height [9] and x-y location on the build plate [10]. In addition, process parameters like scan length [11] and scan speed [12] can affect the porosity and microstructure in the build. Although EBM can produce near-net shaped parts, post-process machining or heat treatments like hot isostatic pressing (HIP) are often necessary to eliminate the varying microstructural features and porosity that arise from different process conditions. For increased Contributed Papers from Materials Science and Technology 2017 (MS&T17)
Structural Integrity of Additive Manufactured Parts, 2020
International Journal of Fatigue, 2010
Effects of grain orientation on fatigue crack nucleation in Waspaloy were investigated. Fatigue t... more Effects of grain orientation on fatigue crack nucleation in Waspaloy were investigated. Fatigue testing was carried out at 8599% of the yield stress of the material, at R= 0.1 using electropolished specimens extracted from the web of a forged aircraft engine compressor ...
A Monte Carlo analysis method combining the models of dislocation theory with random variable sta... more A Monte Carlo analysis method combining the models of dislocation theory with random variable statistics is used to predict the fatigue response scatter due to the random nature of the physical microstructure. The microstructure is modeled using the appropriate statistical distributions for high strength materials typical of those used in propulsion structures. The method simulates crack growth through the random microstructure using the appropriate fracture mechanics processes. The method allows for three stages of damage accumulation and simulates the transition from one stage to the next using the proper mechanistic linkages. The method is general and considers the entire range of damage accumulation sequences; from crack nucleation of the initially unflawed structure to final fast fracture
Many sound and vibration applications have adopted signal processing. FFT-based signal processing... more Many sound and vibration applications have adopted signal processing. FFT-based signal processing algorithms might not help in some applications. Several advanced signal processing algorithms beyond the FFT such as Time-Frequency Analysis, Order Analysis, Quefrency and Cepstrum, wavelet analysis, and AR Modeling uses are outlined. These advanced algorithms can solve sound and vibration challenges that FFTbased algorithms cannot solve. This presentation will introduce the background of these algorithms and their application examples, such as bearing fault detection, motor testing and turbomachinery monitoring. Topic: 1B Health Management for Turbomachinery Thursday, September 02, 2010 Page 2 of 69 MFPT 2009 Paper Abstracts Listing Presenting Author: Richard Holmes Organization: VEXTEC Corporation Country: Paper Title: Scaled Turbine Engine Testing for Cost-effective Health Prognosis Co Authors: Thomas Brooks, Robert Tryon Abstract: Full scale gas turbine engine testing is expensive a...
ECS Meeting Abstracts, 2011
not Available.
Materials Science and Engineering: A, 2019
Build orientation, surface roughness, and scan path influence on the microstructure, mechanical p... more Build orientation, surface roughness, and scan path influence on the microstructure, mechanical properties, and flexural fatigue behavior of Ti-6Al-4V fabricated by electron beam melting,
High strength components exposed to cyclic loading such as gas turbine disks fail in an insidious... more High strength components exposed to cyclic loading such as gas turbine disks fail in an insidious manner, giving no prior indication that damage has occurred. Cracking takes place on a very small scale and the critical damage state is reached when the crack is very small. Unfortunately, cracks of these sizes are difficult to detect. Often, long crack damage is considered when performing fatigue diagnostics. However, an accurate onboard prognostic capability should consider total life as initiation and long crack growth. Prognostication of small cracks requires simulating fatigue damage accumulation from the evolution of micro scale damage initiation. This paper discusses methods for predicting the probability of fatigue failure from cracks starting on the micro scale. These methods predict the variation in fatigue life based on the statistical variation in the microstructure of the material. Material parameters at the metallic grain level are integrated with fundamental physics-based models to predict the damage as it accumulates.
SAE Technical Paper Series, 2007
International Journal of Fatigue, 1998
Fatigue Asbstracts lation was performed as a function of depth below the surface on samples from ... more Fatigue Asbstracts lation was performed as a function of depth below the surface on samples from two orthogonal orientations. The slip band type and density was determined as a function of the resolved shear stress acting on the slip planes and their proximity to the surface. In the primary-o, fatigue damage accumulation occurred primarily by slip on basal planes. Evidence of cc+0 and prism slip was also found, but only where the resolved shear stress on the basal planes was low. Significantly, basal slip was identified on planes on which the resolved shear stress was low. In the transformed-/.I phase strain accumulation was wbstantially greater and was accommodated approximately equally on both basal and prism planes. In all cases, strain was a maximum in the surface grains and decreased with depth at a greater rate than the applied stress. Direct TEM evidence of crack nuclei was found. Cracks formed subsurface at stress concentrations on basal planes and grew along the basal plane towards the surface. The crack initiation mechanism is discussed in relation to strain discontinuities, resolved shear and tensile stresses, chemical composition and slip band length. Photomicrographs, 50 ref. Aging effects on the cyclic deformation mechanisms of a duplex stainless steel.
Engineering Fracture Mechanics, 1996
This paper presents a case study in which structural reliability-based methodologies are used to ... more This paper presents a case study in which structural reliability-based methodologies are used to assess cyclic fatigue life. The study involves the high pressure turbine of a turboprop engine. 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 NASA/USRA/ADP Design Projects from Vanderbilt University, Department of Mechanical Engineerin... more The NASA/USRA/ADP Design Projects from Vanderbilt University, Department of Mechanical Engineering (1994) are enclosed in this final report. Design projects include: (1) Protein Crystal Growth, both facilities and methodology; (2) ACES Deployable Space Boom; (3) Hybrid Launch System designs for both manned and unmanned systems; (4) LH2 Fuel Tank design (SSTO); (5) SSTO design; and (6) Pressure Tank Feed System design.
2005 IEEE Aerospace Conference
ABSTRACT
AIAA SCITECH 2022 Forum, 2022
52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, 2011
This work developed and applied a probabilistic microstructure-sensitive fatigue analysis of Wasp... more This work developed and applied a probabilistic microstructure-sensitive fatigue analysis of Waspaloy to a turbine disk with realistic processing and in-service loads. Processing residual stresses predicted by a gas turbine OEM were applied to a cyclic symmetry finite element model of a Waspaloy turbine disk. Centrifugal loads and thermal gradients were applied to the model to determine in-service loads. These loads were supplied as inputs to a microstructurally-based probabilistic fatigue model to simulate disk lifetimes. A series of trade studies were performed to determine the effect of varying microstructure (grain and precipitate sizes) in the disk bore, web, and rim on the fatigue life distributions.
Engineering Design Reliability Handbook, 2004
Volume 3B: General, 1993
The reliability of a gas turbine engine structure is affected by the uncertainties in the operati... more The reliability of a gas turbine engine structure is affected by the uncertainties in the operating environment (speed, temperature etc.) as well as in the structural properties (material properties, geometries, boundary conditions etc.). A computational method for accurate reliability estimation under such uncertainties is described in this paper. Reliability computation for individual failure modes (burst, LCF etc.) as well as overall system failure is addressed. System failure probability is computed through the union of individual mode failures. The method also provides precise sensitivity information about the effect of each uncertain parameter on the individual failure probabilities as well as on the system failure probability. Such quantitative information helps rational design decisions as well as risk assessment and certification.
Electron beam melting (EBM) is a powder-bed fusion metal additive manufacturing technique that pr... more Electron beam melting (EBM) is a powder-bed fusion metal additive manufacturing technique that produces fully dense and complex parts directly from a computer aided design (CAD) model and was originally developed by Arcam AB. Unique to this additive manufacturing method, the Arcam EBM systems use a high powered electron beam to selectively melt powder to build a part layer-by-layer. The EBM technology is of particular interest to the aerospace [1], biomedical [2], and automotive [3] industries for its ability to create highly complex parts with high resolution and low lead times with goals of increasing efficiency and reducing part counts. According to Arcam, the EBM system is capable of processing a variety of alloys including Inconel 718, Cobalt-Chrome, and Ti-6Al-4V. The majority of research is devoted to Ti-6Al-4V. Ti-6Al-4V is a commonly used Ti alloy for its combination of strength, corrosion resistance, toughness, and workability [4]. Ti-6Al-4V is often used in aerospace applications, like wing attachments [5] where high strength and fatigue-damage tolerance are needed. Despite the outstanding mechanical properties, Ti-6Al-4V is difficult to machine and process so the costs limit its use in industry. With the ever-present push towards lighter and more efficient aircraft, reducing the cost of Ti-6Al-4V components is a priority for the aerospace industry. A promising method is additive manufacturing, specifically EBM. The EBM manufacturing is well suited for Ti-6Al-4V because of its processing conditions. EBM is under rough vacuum during the build process and because Ti-6Al-4V is highly reactive with elements in air, melt related defects can be avoided. In addition, EBM is capable of producing near-net shape components directly so that possible machining defects and scrap material can be reduced and nearly eliminated. The elevated build chamber temperature acts as an in-situ anneal reducing residual stresses to only 5-10% of the ultimate tensile strength [6] and effectively decomposing the hard but brittle α´ martensite phase produced by a rapid cooling rate [7], both of which are present in the as-built Ti-6Al-4V processed by laser AM systems [8]. Because residual stresses, machining defects, and melt defects can all negatively affect fatigue behavior, EBM appears to be a viable alternative to traditional manufacturing methods for Ti-6Al-4V fatigue critical components. However, because it is a new technology, a number of novel variables, process conditions, settings, and their effects on microstructure and then fatigue behavior must be understood before the widespread use. Process parameters have an impact on the microstructure of the finished parts and then corresponding mechanical properties. Research has shown that tensile properties and hardness can vary depending on the build height [9] and x-y location on the build plate [10]. In addition, process parameters like scan length [11] and scan speed [12] can affect the porosity and microstructure in the build. Although EBM can produce near-net shaped parts, post-process machining or heat treatments like hot isostatic pressing (HIP) are often necessary to eliminate the varying microstructural features and porosity that arise from different process conditions. For increased Contributed Papers from Materials Science and Technology 2017 (MS&T17)
Structural Integrity of Additive Manufactured Parts, 2020
International Journal of Fatigue, 2010
Effects of grain orientation on fatigue crack nucleation in Waspaloy were investigated. Fatigue t... more Effects of grain orientation on fatigue crack nucleation in Waspaloy were investigated. Fatigue testing was carried out at 8599% of the yield stress of the material, at R= 0.1 using electropolished specimens extracted from the web of a forged aircraft engine compressor ...
A Monte Carlo analysis method combining the models of dislocation theory with random variable sta... more A Monte Carlo analysis method combining the models of dislocation theory with random variable statistics is used to predict the fatigue response scatter due to the random nature of the physical microstructure. The microstructure is modeled using the appropriate statistical distributions for high strength materials typical of those used in propulsion structures. The method simulates crack growth through the random microstructure using the appropriate fracture mechanics processes. The method allows for three stages of damage accumulation and simulates the transition from one stage to the next using the proper mechanistic linkages. The method is general and considers the entire range of damage accumulation sequences; from crack nucleation of the initially unflawed structure to final fast fracture
Many sound and vibration applications have adopted signal processing. FFT-based signal processing... more Many sound and vibration applications have adopted signal processing. FFT-based signal processing algorithms might not help in some applications. Several advanced signal processing algorithms beyond the FFT such as Time-Frequency Analysis, Order Analysis, Quefrency and Cepstrum, wavelet analysis, and AR Modeling uses are outlined. These advanced algorithms can solve sound and vibration challenges that FFTbased algorithms cannot solve. This presentation will introduce the background of these algorithms and their application examples, such as bearing fault detection, motor testing and turbomachinery monitoring. Topic: 1B Health Management for Turbomachinery Thursday, September 02, 2010 Page 2 of 69 MFPT 2009 Paper Abstracts Listing Presenting Author: Richard Holmes Organization: VEXTEC Corporation Country: Paper Title: Scaled Turbine Engine Testing for Cost-effective Health Prognosis Co Authors: Thomas Brooks, Robert Tryon Abstract: Full scale gas turbine engine testing is expensive a...
ECS Meeting Abstracts, 2011
not Available.
Materials Science and Engineering: A, 2019
Build orientation, surface roughness, and scan path influence on the microstructure, mechanical p... more Build orientation, surface roughness, and scan path influence on the microstructure, mechanical properties, and flexural fatigue behavior of Ti-6Al-4V fabricated by electron beam melting,
High strength components exposed to cyclic loading such as gas turbine disks fail in an insidious... more High strength components exposed to cyclic loading such as gas turbine disks fail in an insidious manner, giving no prior indication that damage has occurred. Cracking takes place on a very small scale and the critical damage state is reached when the crack is very small. Unfortunately, cracks of these sizes are difficult to detect. Often, long crack damage is considered when performing fatigue diagnostics. However, an accurate onboard prognostic capability should consider total life as initiation and long crack growth. Prognostication of small cracks requires simulating fatigue damage accumulation from the evolution of micro scale damage initiation. This paper discusses methods for predicting the probability of fatigue failure from cracks starting on the micro scale. These methods predict the variation in fatigue life based on the statistical variation in the microstructure of the material. Material parameters at the metallic grain level are integrated with fundamental physics-based models to predict the damage as it accumulates.
SAE Technical Paper Series, 2007
International Journal of Fatigue, 1998
Fatigue Asbstracts lation was performed as a function of depth below the surface on samples from ... more Fatigue Asbstracts lation was performed as a function of depth below the surface on samples from two orthogonal orientations. The slip band type and density was determined as a function of the resolved shear stress acting on the slip planes and their proximity to the surface. In the primary-o, fatigue damage accumulation occurred primarily by slip on basal planes. Evidence of cc+0 and prism slip was also found, but only where the resolved shear stress on the basal planes was low. Significantly, basal slip was identified on planes on which the resolved shear stress was low. In the transformed-/.I phase strain accumulation was wbstantially greater and was accommodated approximately equally on both basal and prism planes. In all cases, strain was a maximum in the surface grains and decreased with depth at a greater rate than the applied stress. Direct TEM evidence of crack nuclei was found. Cracks formed subsurface at stress concentrations on basal planes and grew along the basal plane towards the surface. The crack initiation mechanism is discussed in relation to strain discontinuities, resolved shear and tensile stresses, chemical composition and slip band length. Photomicrographs, 50 ref. Aging effects on the cyclic deformation mechanisms of a duplex stainless steel.
Engineering Fracture Mechanics, 1996
This paper presents a case study in which structural reliability-based methodologies are used to ... more This paper presents a case study in which structural reliability-based methodologies are used to assess cyclic fatigue life. The study involves the high pressure turbine of a turboprop engine. 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 NASA/USRA/ADP Design Projects from Vanderbilt University, Department of Mechanical Engineerin... more The NASA/USRA/ADP Design Projects from Vanderbilt University, Department of Mechanical Engineering (1994) are enclosed in this final report. Design projects include: (1) Protein Crystal Growth, both facilities and methodology; (2) ACES Deployable Space Boom; (3) Hybrid Launch System designs for both manned and unmanned systems; (4) LH2 Fuel Tank design (SSTO); (5) SSTO design; and (6) Pressure Tank Feed System design.
2005 IEEE Aerospace Conference
ABSTRACT
AIAA SCITECH 2022 Forum, 2022
52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, 2011
This work developed and applied a probabilistic microstructure-sensitive fatigue analysis of Wasp... more This work developed and applied a probabilistic microstructure-sensitive fatigue analysis of Waspaloy to a turbine disk with realistic processing and in-service loads. Processing residual stresses predicted by a gas turbine OEM were applied to a cyclic symmetry finite element model of a Waspaloy turbine disk. Centrifugal loads and thermal gradients were applied to the model to determine in-service loads. These loads were supplied as inputs to a microstructurally-based probabilistic fatigue model to simulate disk lifetimes. A series of trade studies were performed to determine the effect of varying microstructure (grain and precipitate sizes) in the disk bore, web, and rim on the fatigue life distributions.
Engineering Design Reliability Handbook, 2004