Experiments and Modeling of the Effect of Heat Exposure on Fatigue of 6061 and 7075 Aluminum Alloys PDF Download
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Author: Andrew T. Brammer Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 73
Book Description
Strain-controlled fatigue tests were performed on 6061-T6 and 7075-T651 aluminum alloys as well as additional specimens of the same materials after exposure to a temperature of 538oC for 1 hour and cooling to room temperature. The fatigue behavior of all four materials was characterized using traditional strain-life analysis. The fatigue data was found to show no appreciable effect of the heat exposure in low cycle fatigue, and a decrease in fatigue life in high cycle fatigue in both 6061 and 7075. In addition, scanning electron microscopy was employed to determine that crack initiation occurred at Fe-rich particles and subsequence analysis was used to measure crack growth rates. The fatigue cracks were found to initiate at cracked intermetallic particles in the peak-aged alloys and at de-bonded particles in the heat exposed alloys. Using standard metallographic techniques, microstructural characterization including grain size, intermetallic particle size, and nearest neighbor distance were quantified. As such, this characterization data was implemented into a microstructure-sensitive fatigue model resulting in a unique set of modeling parameters to capture the experimental results of both the peak-aged and thermally-affected 6061 aluminum alloy and 7075 aluminum alloy data.
Author: Andrew T. Brammer Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 73
Book Description
Strain-controlled fatigue tests were performed on 6061-T6 and 7075-T651 aluminum alloys as well as additional specimens of the same materials after exposure to a temperature of 538oC for 1 hour and cooling to room temperature. The fatigue behavior of all four materials was characterized using traditional strain-life analysis. The fatigue data was found to show no appreciable effect of the heat exposure in low cycle fatigue, and a decrease in fatigue life in high cycle fatigue in both 6061 and 7075. In addition, scanning electron microscopy was employed to determine that crack initiation occurred at Fe-rich particles and subsequence analysis was used to measure crack growth rates. The fatigue cracks were found to initiate at cracked intermetallic particles in the peak-aged alloys and at de-bonded particles in the heat exposed alloys. Using standard metallographic techniques, microstructural characterization including grain size, intermetallic particle size, and nearest neighbor distance were quantified. As such, this characterization data was implemented into a microstructure-sensitive fatigue model resulting in a unique set of modeling parameters to capture the experimental results of both the peak-aged and thermally-affected 6061 aluminum alloy and 7075 aluminum alloy data.
Author: James Brian Jordon Publisher: ISBN: Category : Aluminum alloys Languages : en Pages :
Book Description
In this work, understanding the microstructural effects of monotonic and cyclic failure of wrought 7075-T651 and cast A356 aluminum alloys were examined. In particular, the structure-property relations were quantified for the plasticity/damage model and two fatigue crack models. Several types of experiments were employed to adapt an internal state variable plasticity and damage model to the wrought alloy. The damage model was originally developed for cast alloys and thus, the model was modified to account for void nucleation, growth, and coalescence for a wrought alloy. In addition, fatigue experiments were employed to determine structure-property relations for the cast alloy. Based on microstructural analysis of the fracture surfaces, modifications to the microstructurally-based MultiStage fatigue model were implemented. Additionally, experimental fatigue crack results were used to calibrate FASTRAN, a fatigue life prediction code, to small fatigue-crack-growth behavior. Lastly, a set of experiments were employed to explore the damage history effect associated with cast and wrought alloys and to provide motivation for monotonic and fatigue modeling efforts.
Author: C. M. Hudson Publisher: ISBN: Category : Aluminum alloys Languages : en Pages : 28
Book Description
A series of fatigue tests with specimens subjected to constant amplitude and two-step axial loads were conducted on 12-inch-wide sheet specimens of 2024-T3 and 7075-T6 aluminum alloy to study the effects of a change in stress level on fatigue-crack propagation. Comparison of the results of the tests in which the specimens were tested at first a high and then a low stress level with those of the constant-stress-amplitude tests indicated that crack propagation was generally delayed after the transition to the lower stress level. In the tests in which the specimens were tested at first a low and then a high stress level, crack propagation continued at the expected rate after the change in stress levels.
Author: Rodney L. Wilkinson Publisher: ISBN: Category : Aluminum alloys Languages : en Pages : 68
Book Description
Changes in the crack growth behavior of 7075-T651 aluminum specimens which has been exposed to temperatures between 150 degrees and 355 degrees F (66 deg and 179 deg C) were evaluated. Specimens were fatigue tested at room temperature under flight-by-flight loading conditions. Results from these tests were then compared with data from the baseline (as received) material. Exposure to 250 deg F (121 deg C) or more produced a definite increase in speciment life, apparently due to a decrease in crack growth rates.
Author: Andrew T. Brammer
Author: Andrew T. Brammer
Author: James Brian Jordon
Author: C. M. Hudson
Author: Richard A. Everett
Author: Eugene C. Naumann
Author: Alfred M. Freudenthal
Author: 
Author: Rodney L. Wilkinson
Author: Robert Spitzer
Author: William Nichols Findley