The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
M.j. Caton - One of the best experts on this subject based on the ideXlab platform.
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Effect of Aging Treatment on Fatigue Behavior of an Al-Cu-Mg-Ag Alloy
Metallurgical and Materials Transactions A, 2013Co-Authors: M. E. Burba, S.k. Jha, M.j. Caton, C. J. SzczepanskiAbstract:An investigation of the fatigue properties of an Al-Cu-Mg-Ag alloy with two different heat treatments—peak aged (T6), and peak aged interrupted (T6I4)—has been conducted. While the strength levels resulting from the two heat treatments were similar, the main difference between the microstructures was that the peak aged interrupted material contained a higher volume fraction of the θ ′ precipitates. This study specifically focused on the effects of these treatments on the fatigue lifetime distribution, and the role of crack initiation vs the small crack Growth behavior. Several total fatigue lifetime tests were completed at room temperature and at a given stress level to characterize the distribution in fatigue lifetimes. Fatigue results indicate that there is almost no difference in the mean lifetime for either heat treatment, but there is a significant difference in the minimum lifetimes, where the peak aged condition exhibited a higher propensity for life-limiting failure mechanisms. The small crack Growth behavior of the two aging treatments was studied both at room temperature and elevated temperature by means of a standard acetate replication method. The small crack Growth rates at both temperatures were largely unaffected by the different aging treatments. Based on the given number of tests, results suggest that the life-limiting fatigue failures of the two aging treatments are primarily governed by different crack initiation mechanisms due to the differences seen in the density of θ ′ precipitates.
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Stress ratio effects on small fatigue crack Growth in Ti–6Al–4V
International Journal of Fatigue, 2012Co-Authors: M.j. Caton, Reji John, W.j. Porter, M. E. BurbaAbstract:Abstract A systematic study of the effects of stress ratio on small fatigue crack Growth in Ti–6Al–4V was conducted. Cylindrical fatigue specimens were tested axially at room temperature under a maximum stress of 690 MPa and with stress ratios (R) of 0.5, 0.1, and −1. Tests were periodically interrupted and a standard replication technique was used to monitor the Growth of cracks artificially initiated from 30 to 40 μm micro-notches, which were milled into the specimen surface with a focused ion beam (FIB). Measurement of striation spacing from fracture surfaces was evaluated for determining small crack Growth rates and showed good agreement with replication data, but is only possible for relatively high stress intensity factor ranges, ΔK, on the order of 10 MPa√m or greater. A significant small crack effect is observed in this alloy, consistent with previous observations, where small cracks grew at stress intensity factor ranges below the long crack threshold and at higher rates than long cracks for equivalent ΔK levels. While a modest effect of stress ratio is seen on small crack Growth rates when plotted as a function of crack size (faster Growth at lower mean stresses for a given maximum stress), no discernable effect of R is seen when plotting as a function of ΔK. Significant scatter is observed in the small crack Growth rates, and the implications of data reduction methods are discussed.
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Small fatigue crack Growth and failure mode transitions in a Ni-base superalloy at elevated temperature
International Journal of Fatigue, 2010Co-Authors: M.j. Caton, S.k. JhaAbstract:Abstract A study of the long and small fatigue crack Growth behavior in IN100 tested at 650 °C both with and without dwell periods is summarized. A significant small crack effect is evident in this alloy, and it is observed that the influence of loading variables on small crack behavior is profoundly different from that on long cracks. While a 6 s dwell has negligible effect on long crack Growth rates, it results in more than an order of magnitude faster Growth for small cracks (∼30 μm to 1 mm). Long crack Growth is dominated by intergranular cracking both with and without 6 s dwell. Small crack Growth mode depends on numerous factors including crack size, dwell time, exposure to environment, and character of initiation site. Transitions in small crack Growth modes and the operative crack Growth mechanisms are discussed.
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Mean vs. Life-Limiting Fatigue Behavior of a Nickel-Based Superalloy (Postprint)
2008Co-Authors: S.k. Jha, M.j. Caton, J. M. LarsenAbstract:Abstract : The mean and the life-limiting behavior under fatigue of the nickel-based superalloy, IN100, separated (or converged) as a function of stress level and dwell loading. This behavior was related to the control of the life-limiting behavior by the Small-Crack Growth regime, producing its much slower response to stress level and dwell-time, relative to the mean-lifetime behavior. The lifetime probability density is therefore, modeled as a superposition of the crack Growth lifetime density and a mean-lifetime density. The crack Growth density is calculated with the help of Small-Crack Growth data and the distribution in the crack initiation size. The mean-lifetime density is estimated from a relatively small number of total lifetime fatigue tests. In IN100, we apply this approach to predict the effects of stress level and dwell time on the lifetime distribution and the B0.1 (1 in 1000 probability of failure) lifetime limit.
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The influence of heat treatment and solidification time on the behavior of small-fatigue-cracks in a cast aluminum alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2001Co-Authors: M.j. Caton, J. W. Jones, John E. AllisonAbstract:Abstract For a wide range of stress amplitudes, the fatigue life of cast aluminum specimens is dominated by propagation of small cracks that initiate predominantly from microshrinkage pores. Therefore, an understanding of the Small-Crack behavior and knowledge of the pore size distribution enables the prediction of fatigue properties. In order to understand the influence of processing parameters on fatigue performance, Small-Crack Growth was monitored for three different solidification times in both peak-aged (T6) and over-aged (T7) conditions of cast W319 aluminum, a commercial Al–Si–Cu alloy used in automotive castings. Results indicate that small cracks in the T6 microstructures grow only slightly slower than those in the T7 material. A correlating parameter of the form [( eσ / σ y ) n a ] is shown to effectively characterize Small-Crack Growth rates in both the T6 and T7 conditions for a wide range of applied stresses and solidification times.
Nima Shamsaei - One of the best experts on this subject based on the ideXlab platform.
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Modeling fatigue crack Growth behavior in rolled AZ31 magnesium alloy using CTOD based strip yield modeling
International Journal of Fatigue, 2017Co-Authors: Cole Cauthen, Steven R Daniewicz, Nima ShamsaeiAbstract:Abstract Fatigue crack Growth behavior of a rolled AZ31 magnesium plate is investigated and modelled in this study. Fatigue crack Growth tests were performed on compact tension specimens at load ratios of R = 0.1 and R = 0.7 to provide data for a strip-yield based fatigue crack Growth model. Minimal differences in crack closure were observed between the two load ratios. Threshold values for the stress intensity factor range were found to be often less than those reported in previous literature. The reason for lower threshold values could be related to the nontraditional compression pre-cracking method used in this study, which was employed in an attempt to produce a more accurate measurement of the fatigue crack threshold. In addition to the long crack fatigue crack Growth testing using compact tension specimens, load controlled fatigue tests were conducted on flat, reduced gage specimens at load ratios of R = 0.1 and R = −1.0 to study the microstructurally small crack Growth behavior and to extend the model capability to predict the microstructurally small crack Growth behavior. The reduced gage specimens were found to spend the majority of their life in the crack Growth stage. Cracks primarily grew in a planar fashion other than where multiple cracks coalesced. The microstructurally small crack Growth data from these experiments were also compared with predictions from the fatigue crack Growth model. Crack Growth modeling revealed that traditional calculations using plasticity-induced crack closure concepts and an effective stress intensity factor range were not able to predict the microstructurally small crack Growth behavior of these specimens. In contrast, computing crack Growth rate from crack tip opening displacement was shown to give satisfactory results. Crack opening stresses for the fully reversed tests revealed that the compressive loading largely nullified the effect of the plastic wake on fatigue crack Growth.
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Small fatigue crack Growth under multiaxial stresses
International Journal of Fatigue, 2014Co-Authors: Nima Shamsaei, Ali FatemiAbstract:Abstract A significant portion of the fatigue life is typically spent in Growth of small cracks. In addition, the stress state in many structures and components is multiaxial. Therefore, the study of small crack Growth behaviour with regards to its Growth path as well as Growth rate under combined stresses can be of great importance in many applications. This study investigates small crack Growth behaviour of several steels under multiaxial states of stress. Experimental observations from solid and thin-walled tubular round specimens under various multiaxial cyclic loadings including in-phase and out-of-phase, tension–torsion and tension–tension, and with or without mean stresses are used to characterise small crack Growth behaviour. The steels used include 1045 and 1050 medium carbon steels, 304L stainless steel, and Inconel 718. Effects of load non-proportionality, mean stresses, and friction-induced closure on small fatigue crack Growth behaviour are discussed. Critical plane analysis and an effective strain intensity factor are used to predict crack Growth path as well as to correlate crack Growth rates under various combined stress conditions.
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065 Small Crack Growth Path and Rate under Combined Stresses
2013Co-Authors: Nima Shamsaei, Ali Fatemi, Leonid KrenevAbstract:A significant portion of the fatigue life is typically spent in Growth of small cracks. In addition, the stress state in many structures and components is multiaxial. Therefore, the study of small crack Growth behavior with regards to its Growth path as well as Growth rate under combined stresses can be of great importance in many applications. This study investigates small crack Growth behavior of several steels under multiaxial states of stress. Experimental observations from solid and thinwalled tubular round specimens under various multiaxial cyclic loadings including inphase and out-of-phase, tension-torsion and tension-tension, and with or without mean stresses are used to characterize small crack Growth behavior. The steels used include 1045 and 1050 medium carbon steels, 304L stainless steel, and Inconel 718. Effects of load non-proportionality, mean stresses, and friction-induced closure on small fatigue crack Growth behavior are discussed. Critical plane analysis and an effective strain intensity factor are used to predict crack Growth path as well as to correlate crack Growth rates under various combined stress conditions.
Cole Cauthen - One of the best experts on this subject based on the ideXlab platform.
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Characterization of Surface Fatigue Crack Nucleation and Microstructurally Small Crack Growth in High Strength Aluminum Alloys
Frontiers in Materials, 2021Co-Authors: Robert Fleishel, Steven R Daniewicz, Cole Cauthen, J.b. Jordon, Andrew Baker, Stephanie TermaathAbstract:It is well established that fatigue crack nucleation and small crack Growth in high strength aluminum alloys are highly influenced by the surrounding microstructure including grain boundaries, texture, inclusion barriers, among other factors. As such, specific and targeted experimental and computational methods are necessary to accurately capture and predict the discrete behavior of microstructurally small fatigue cracks. In this study, surface fatigue crack nucleation and microstructurally small crack Growth in high strength aluminum alloys, commonly used in aerospace applications, are evaluated through a holistic approach encompassing fatigue testing, crack measurement, and computational prediction of crack Growth rates. During fatigue testing, crack shapes and Growth are quantified using a novel surface replication technique that is applied to investigate crack nucleation, as well as to collect validation data that includes an accurate description of crack shape during crack propagation, a challenging and essential component in predicting crack Growth. Computational simulation of fatigue crack Growth in non-straight, complex surface crack arrays typically requires high fidelity analysis using computationally expensive methods to account for the mathematical and geometrical complexities inherent in the solution. A dislocation distribution based technique has been previously demonstrated to rapidly and accurately predict the stress intensity factors for through cracks of complex shape. This method was expanded and investigated as an approach for rapidly predicting the crack Growth rate of kinked and tortuous surface crack arrays, using the crack configuration and bulk material properties as inputs. To investigate the accuracy and effectiveness of this characterization approach, surface crack Growth in AA7075-T7351 was experimentally analyzed and modeled under high cycle and low cycle fatigue conditions. This comprehensive approach was determined to be an expedient and applicable method for characterizing and evaluating the nucleation and crack Growth rate of non-planar microstructurally small and short crack configurations.
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Fatigue crack nucleation and microstructurally small crack Growth mechanisms in high strength aluminum alloys
International Journal of Fatigue, 2020Co-Authors: Cole Cauthen, Steven R Daniewicz, K.v. Anderson, D.z. Avery, Andrew H. Baker, C.j. Williamson, J.b. JordonAbstract:Abstract Characterization of microstructurally small fatigue crack Growth behavior for two aluminum alloys, AA7065 and AA2099, were quantified using a surface replication process for the first time. In addition, scanning electron microscopy analysis revealed that for AA7065, crack initiation was caused by either voids or intermetallic particles. Whereas, for the AA2099, crack initiation was caused by persistent slip bands and intermetallic particles. From electron backscatter diffraction results, the grains at the crack initiation site for the AA7065 exhibited high misorientation boundaries, while the grains at the crack initiation sites for the AA2099 exhibited both high and low misorientation boundaries.
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Modeling fatigue crack Growth behavior in rolled AZ31 magnesium alloy using CTOD based strip yield modeling
International Journal of Fatigue, 2017Co-Authors: Cole Cauthen, Steven R Daniewicz, Nima ShamsaeiAbstract:Abstract Fatigue crack Growth behavior of a rolled AZ31 magnesium plate is investigated and modelled in this study. Fatigue crack Growth tests were performed on compact tension specimens at load ratios of R = 0.1 and R = 0.7 to provide data for a strip-yield based fatigue crack Growth model. Minimal differences in crack closure were observed between the two load ratios. Threshold values for the stress intensity factor range were found to be often less than those reported in previous literature. The reason for lower threshold values could be related to the nontraditional compression pre-cracking method used in this study, which was employed in an attempt to produce a more accurate measurement of the fatigue crack threshold. In addition to the long crack fatigue crack Growth testing using compact tension specimens, load controlled fatigue tests were conducted on flat, reduced gage specimens at load ratios of R = 0.1 and R = −1.0 to study the microstructurally small crack Growth behavior and to extend the model capability to predict the microstructurally small crack Growth behavior. The reduced gage specimens were found to spend the majority of their life in the crack Growth stage. Cracks primarily grew in a planar fashion other than where multiple cracks coalesced. The microstructurally small crack Growth data from these experiments were also compared with predictions from the fatigue crack Growth model. Crack Growth modeling revealed that traditional calculations using plasticity-induced crack closure concepts and an effective stress intensity factor range were not able to predict the microstructurally small crack Growth behavior of these specimens. In contrast, computing crack Growth rate from crack tip opening displacement was shown to give satisfactory results. Crack opening stresses for the fully reversed tests revealed that the compressive loading largely nullified the effect of the plastic wake on fatigue crack Growth.
John E. Allison - One of the best experts on this subject based on the ideXlab platform.
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Effects of alloying and processing on ultrasonic fatigue behavior in binary Ti-Al alloys
Materials Science and Engineering: A, 2019Co-Authors: Qianying Shi, J. Wayne Jones, Sinsar A. Hsie, John E. AllisonAbstract:Abstract Three model binary Ti-Al alloys with single α phase were investigated in this study to develop a fundamental understanding of high cycle and very high cycle fatigue behavior in α-titanium alloys. Ultrasonic fatigue instrumentation with a cyclic frequency of nominally 20 kHz was used for fully reversed loading fatigue testing and combined with customized optical microscopy to study small crack Growth from artificial cracks initiated at micro-notches produced by focused ion beam. Fractography showed the formation of low ΔK facets with different features near the crack initiation sites. Micro-beach marks were observed to form on some facets which could be correlated with the spatial angle between facet normal and loading direction. Aluminum content and processing (forging/rolling history) were found to have no significant effect on the small crack Growth behavior of the studied alloys. Different crack Growth models were compared and discussed to estimate the fatigue performance, especially for cross-rolled Ti-4Al alloy with void-type defects.
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The influence of heat treatment and solidification time on the behavior of small-fatigue-cracks in a cast aluminum alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2001Co-Authors: M.j. Caton, J. W. Jones, John E. AllisonAbstract:Abstract For a wide range of stress amplitudes, the fatigue life of cast aluminum specimens is dominated by propagation of small cracks that initiate predominantly from microshrinkage pores. Therefore, an understanding of the Small-Crack behavior and knowledge of the pore size distribution enables the prediction of fatigue properties. In order to understand the influence of processing parameters on fatigue performance, Small-Crack Growth was monitored for three different solidification times in both peak-aged (T6) and over-aged (T7) conditions of cast W319 aluminum, a commercial Al–Si–Cu alloy used in automotive castings. Results indicate that small cracks in the T6 microstructures grow only slightly slower than those in the T7 material. A correlating parameter of the form [( eσ / σ y ) n a ] is shown to effectively characterize Small-Crack Growth rates in both the T6 and T7 conditions for a wide range of applied stresses and solidification times.
Steven R Daniewicz - One of the best experts on this subject based on the ideXlab platform.
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Characterization of Surface Fatigue Crack Nucleation and Microstructurally Small Crack Growth in High Strength Aluminum Alloys
Frontiers in Materials, 2021Co-Authors: Robert Fleishel, Steven R Daniewicz, Cole Cauthen, J.b. Jordon, Andrew Baker, Stephanie TermaathAbstract:It is well established that fatigue crack nucleation and small crack Growth in high strength aluminum alloys are highly influenced by the surrounding microstructure including grain boundaries, texture, inclusion barriers, among other factors. As such, specific and targeted experimental and computational methods are necessary to accurately capture and predict the discrete behavior of microstructurally small fatigue cracks. In this study, surface fatigue crack nucleation and microstructurally small crack Growth in high strength aluminum alloys, commonly used in aerospace applications, are evaluated through a holistic approach encompassing fatigue testing, crack measurement, and computational prediction of crack Growth rates. During fatigue testing, crack shapes and Growth are quantified using a novel surface replication technique that is applied to investigate crack nucleation, as well as to collect validation data that includes an accurate description of crack shape during crack propagation, a challenging and essential component in predicting crack Growth. Computational simulation of fatigue crack Growth in non-straight, complex surface crack arrays typically requires high fidelity analysis using computationally expensive methods to account for the mathematical and geometrical complexities inherent in the solution. A dislocation distribution based technique has been previously demonstrated to rapidly and accurately predict the stress intensity factors for through cracks of complex shape. This method was expanded and investigated as an approach for rapidly predicting the crack Growth rate of kinked and tortuous surface crack arrays, using the crack configuration and bulk material properties as inputs. To investigate the accuracy and effectiveness of this characterization approach, surface crack Growth in AA7075-T7351 was experimentally analyzed and modeled under high cycle and low cycle fatigue conditions. This comprehensive approach was determined to be an expedient and applicable method for characterizing and evaluating the nucleation and crack Growth rate of non-planar microstructurally small and short crack configurations.
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Fatigue crack nucleation and microstructurally small crack Growth mechanisms in high strength aluminum alloys
International Journal of Fatigue, 2020Co-Authors: Cole Cauthen, Steven R Daniewicz, K.v. Anderson, D.z. Avery, Andrew H. Baker, C.j. Williamson, J.b. JordonAbstract:Abstract Characterization of microstructurally small fatigue crack Growth behavior for two aluminum alloys, AA7065 and AA2099, were quantified using a surface replication process for the first time. In addition, scanning electron microscopy analysis revealed that for AA7065, crack initiation was caused by either voids or intermetallic particles. Whereas, for the AA2099, crack initiation was caused by persistent slip bands and intermetallic particles. From electron backscatter diffraction results, the grains at the crack initiation site for the AA7065 exhibited high misorientation boundaries, while the grains at the crack initiation sites for the AA2099 exhibited both high and low misorientation boundaries.
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Modeling fatigue crack Growth behavior in rolled AZ31 magnesium alloy using CTOD based strip yield modeling
International Journal of Fatigue, 2017Co-Authors: Cole Cauthen, Steven R Daniewicz, Nima ShamsaeiAbstract:Abstract Fatigue crack Growth behavior of a rolled AZ31 magnesium plate is investigated and modelled in this study. Fatigue crack Growth tests were performed on compact tension specimens at load ratios of R = 0.1 and R = 0.7 to provide data for a strip-yield based fatigue crack Growth model. Minimal differences in crack closure were observed between the two load ratios. Threshold values for the stress intensity factor range were found to be often less than those reported in previous literature. The reason for lower threshold values could be related to the nontraditional compression pre-cracking method used in this study, which was employed in an attempt to produce a more accurate measurement of the fatigue crack threshold. In addition to the long crack fatigue crack Growth testing using compact tension specimens, load controlled fatigue tests were conducted on flat, reduced gage specimens at load ratios of R = 0.1 and R = −1.0 to study the microstructurally small crack Growth behavior and to extend the model capability to predict the microstructurally small crack Growth behavior. The reduced gage specimens were found to spend the majority of their life in the crack Growth stage. Cracks primarily grew in a planar fashion other than where multiple cracks coalesced. The microstructurally small crack Growth data from these experiments were also compared with predictions from the fatigue crack Growth model. Crack Growth modeling revealed that traditional calculations using plasticity-induced crack closure concepts and an effective stress intensity factor range were not able to predict the microstructurally small crack Growth behavior of these specimens. In contrast, computing crack Growth rate from crack tip opening displacement was shown to give satisfactory results. Crack opening stresses for the fully reversed tests revealed that the compressive loading largely nullified the effect of the plastic wake on fatigue crack Growth.
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Simulating small crack Growth behaviour using crystal plasticity theory and finite element analysis
Fatigue & Fracture of Engineering Materials & Structures, 2004Co-Authors: Gabriel P. Potirniche, Steven R Daniewicz, James C. NewmanAbstract:Predictions of small crack Growth under cyclic loading in aluminium alloy 7075 are performed using finite element analysis (FEA), and results are compared with published experimental data. A double-slip crystal plasticity model is implemented within the analyses to enable the anisotropic nature of individual grains to be approximated. Small edge-cracks in a single grain with a starting length of 6 μm are incrementally grown following a node-release scheme. Crack-tip opening displacements (CTOD) and crack opening stresses are calculated during the simulated crack Growth, and da/dN against ΔK diagrams are computed. Interactions between the crack tip and a grain boundary are also considered. The computations are shown to accurately capture the magnitude and the variability normally observed in small crack fatigue data.