Author: W. M. McGee
Publisher:
ISBN:
Category : Mathematical models
Languages : en
Pages : 588
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The effects of single overload-underload interaction on constant amplitude crack growth in 2219-T851 aluminum alloy are characterized in terms of delay cycles, affected zone sizes and overload shut-off ratios. Data are presented showing the effects of overload-underload/underload-overload sequences, overload magnitude, underload magnitude, and the constant amplitude maximum and minimum. The effects of hold periods in both tension and compression are also experimentally investigated. Delay cycle data are correlated with predictions from three different crack growth retardation models; namely the generalized Wheeler model, the generalized Willenborg model and the Grumman closure model. For each model, predictions are made using an assumed plastic zone radius and diameter for both plane stress and plane strain conditions and model comparisons are made. Correlations of measured affected zone sizes with the four different assumed plastic zone sizes are also presented. Sensitivities of the generalized Wheeler and generalized Willenborg models to overload shut- off ratio and threshold stress intensity factor are determined. Prediction sensitivity to three different crack growth equations for the 2219-T851 aluminum alloy is also evaluated. Recommendations for future work in development of crack growth retardation models are presented.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 585
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Book Description
The effects of single overload-underload interaction on constant amplitude crack growth in 2219-T851 aluminum alloy are characterized in terms of delay cycles, affected zone sizes and overload shut-off ratios. Data are presented showing the effects of overload-underload/underload-overload sequences, overload magnitude, underload magnitude, and the constant amplitude maximum and minimum. The effects of hold periods in both tension and compression are also experimentally investigated. Delay cycle data are correlated with predictions from three different crack growth retardation models; namely the generalized Wheeler model, the generalized Willenborg model and the Grumman closure model. For each model, predictions are made using an assumed plastic zone radius and diameter for both plane stress and plane strain conditions and model comparisons are made. Correlations of measured affected zone sizes with the four different assumed plastic zone sizes are also presented. Sensitivities of the generalized Wheeler and generalized Willenborg models to overload shut- off ratio and threshold stress intensity factor are determined. Prediction sensitivity to three different crack growth equations for the 2219-T851 aluminum alloy is also evaluated. Recommendations for future work in development of crack growth retardation models are presented.
Author: W. M. McGee
Publisher:
ISBN:
Category : Mathematical models
Languages : en
Pages : 125
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Book Description
The effects of single overload-underload interaction on constant amplitude crack growth in 2219-T851 aluminum alloy are characterized in terms of delay cycles, affected zone sizes and overload shut-off ratios. Data are presented showing the effects of overload-underload/underload-overload sequences, overload magnitude, underload magnitude, and the constant amplitude maximum and minimum. The effects of hold periods in both tension and compression are also experimentally investigated. Delay cycle data are correlated with predictions from three different crack growth retardation models; namely the generalized Wheeler model, the generalized Willenborg model and the Grumman closure model. For each model, predictions are made using an assumed plastic zone radius and diameter for both plane stress and plane strain conditions and model comparisons are made. Correlations of measured affected zone sizes with the four different assumed plastic zone sizes are also presented. Sensitivities of the generalized Wheeler and generalized Willenborg models to overload shut- off ratio and threshold stress intensity factor are determined. Prediction sensitivity to three different crack growth equations for the 2219-T851 aluminum alloy is also evaluated. Recommendations for future work in development of crack growth retardation models are presented.
Author: Stephan M. Russ
Publisher:
ISBN:
Category :
Languages : en
Pages : 271
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Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 1100
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Author: F. Romeiro
Publisher:
ISBN:
Category : Materials
Languages : en
Pages : 15
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Under constant amplitude loading, a single variable (?K) is required in crack growth relationships. The transferability of fatigue laws, determined under constant amplitude loading, to variable amplitude fatigue requires at least an additional variable, whose evolution with crack length accounts for the interaction effects between cycles of different types. The crack opening level (Kop) is usually employed for this purpose because it can be determined from the experiments and compared with predictions from models or FEM analyses. This paper presents an analysis of fatigue crack growth on M(T) specimens of medium carbon steel specimens and using FEM analyses. The specimens are subjected to repeated blocks of cycles made up of one or several overloads separated by a variable number of baseline cycles. The experiments are simulated by FEM analyses, taking into account the cyclic plastic behavior of the low carbon steel. The main objective of this study is to better understand the mechanisms at the origin of interactions effects due to the presence of overloads (or underloads) at different locations of the block loading. It is concluded that the interaction effects are closely related to the cyclic plastic behavior of the material and namely to the Bauschinger effect.
Author: WX. Alzos
Publisher:
ISBN:
Category : Crack propagation
Languages : en
Pages : 20
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Tests, represented in a three-dimensional matrix, were performed to investigate the effects of a single overload/underload sequence on the fatigue crack-growth rate in 2024-T3 aluminum alloy. Three different stress intensity ratios were studied to investigate the delay phenomenon: (1) overload level to maximum cyclic level, Kol/Kmax; (2) underload level to overload level, Kul/Kol; and (3) minimum cyclic level to overload level, Kmin/Kol. These ratios ranged from 1.6 to 3.0, -1.0 to +0.3, and 0.11 to 0.3, respectively. All tests had the same overload stress intensity level. Sufficient data were recorded to accurately determine the crack-growth rate through the overload affected zone. The crack length versus number of cycles data for each test were represented by a spline function which was then analytically differentiated to obtain the growth rate. The number of delay cycles was found to be directly related to the minimum growth rate following the overload/underload sequence. The ratios Kol/Kmax and Kul/Kol were shown to be of particular significance to the delay while the ratio Kmin/Kol was shown to be of less significance. The results were correlated with an extended crack closure concept. From this the maximum value of the opening stress intensity level following the overload/underload sequence can be determined and used to predict the number of delay cycles.
Author: S. J. Hudak
Publisher: ASTM International
ISBN: 9780803107175
Category : Technology & Engineering
Languages : en
Pages : 384
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Author: National Aeronautics and Space Adm Nasa
Publisher: Independently Published
ISBN: 9781792718212
Category :
Languages : en
Pages : 28
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Book Description
Fatigue crack growth tests were conducted on 0.09 inch thick, 3.0 inch wide middle-crack tension specimens cut from sheets of 2024-T3 aluminum alloy. The tests were conducted using a load sequence that consisted of a single block of 2,500 cycles of constant amplitude loading followed by an overload/underload combination. The largest fatigue crack growth life occurred for the tests with the overload stress equal to 2 times the constant amplitude stress and the underload stress equal to the constant amplitude minimum stress. For the tests with compressive underloads, the fatigue crack growth life decreased with increasing compressive underload stress. Dawicke, David S. Langley Research Center NASA-CR-201668, NAS 1.26:201668 NAS1-96014; RTOP 538-02-10-01...
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 38
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