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Full-Text Articles in Mechanical Engineering
Vibration Bending Fatigue Analysis Of Additively Repaired Ti-6al-4v Airfoil Blades, Lucas Jordan Smith
Vibration Bending Fatigue Analysis Of Additively Repaired Ti-6al-4v Airfoil Blades, Lucas Jordan Smith
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Repairing airfoil blades is necessary to extend the life of turbine engines. Directed energy deposition (DED) additive manufacturing (AM) provides the ability to add material at a specific location on an existing component. In this work, AM repairs on Ti-6Al-4V airfoil blades were analyzed to determine what effect the repair will have on the blade performance in high cycle vibration fatigue testing. Targeted sections were cut out of airfoil blades near high stress locations and repaired using DED. To understand the defects that arose with this type of repair, computed tomography imaging was used to quantify the defects from the …
Defect Modeling And Vibration-Based Bending Fatigue Of Additively Manufactured Inconel 718, Wesley Earl Eldt
Defect Modeling And Vibration-Based Bending Fatigue Of Additively Manufactured Inconel 718, Wesley Earl Eldt
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Additive manufacturing (AM) is convenient for building components with complex features. However, the long-term integrity of these components is uncertain, since AM parts have defects such as pores and rough surfaces. In this work, an analytical model was developed to determine the impact of defects, and a novel bending fatigue test was used to determine the fatigue life of channeled specimens. The analytical model, based off the theory of critical distances, investigates coupled pores and predicts their potential for fatigue failure. This resulted in a maximum allowable pore size and spacing recommendation for coupled defects. Additionally, specimens with through channels …
Elucidating The Role Of Microstructure, Texture, And Microtexture On The Dwell Fatigue Response Of Ti-6al-4v, Alec Mitchell Blankenship
Elucidating The Role Of Microstructure, Texture, And Microtexture On The Dwell Fatigue Response Of Ti-6al-4v, Alec Mitchell Blankenship
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Ambient temperature dwell sensitivity is known to be deleterious to the fatigue response of near-alpha titanium alloys. Dwell fatigue refers to the presence of a sustained hold at peak stress as opposed to the continuous variation of normal cyclic fatigue loading. This reduction in failure life-times from dwell loading is attributed to early crack nucleation and faster crack propagation. The degradation is the result of plastic anisotropy on the microstructural scale along with tendency of titanium alloys to creep at low temperatures at stresses well below the 0.2% offset yield strength. Despite being the most widely used titanium alloy, Ti-6Al-4V …
Locally Optimized Covariance Kriging For Non-Stationary System Responses, Daniel Lee Clark Jr.
Locally Optimized Covariance Kriging For Non-Stationary System Responses, Daniel Lee Clark Jr.
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In this thesis, the Locally-Optimized Covariance (LOC) Kriging method is developed. This method represents a flexible surrogate modeling approach for approximating a non-stationary Kriging covariance structures for deterministic responses. The non-stationary covariance structure is approximated by aggregating multiple stationary localities. The aforementioned localities are determined to be statistically significant utilizing the Non-Stationary Identification Test. This methodology is applied to various demonstration problems including simple one and two-dimensional analytical cases, a deterministic fatigue and creep life model, and a five-dimensional fluid-structural interaction problem. The practical significance of LOC-Kriging is discussed in detail and is directly compared to stationary Kriging considering computational …
Effect Of A Graded Layer On The Plastic Dissipation During Mixed-Mode Fatigue Crack Growth On Plastically Mismatched Interfaces, Craig M. Baudendistel
Effect Of A Graded Layer On The Plastic Dissipation During Mixed-Mode Fatigue Crack Growth On Plastically Mismatched Interfaces, Craig M. Baudendistel
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Recent work has proposed a dissipated energy theory of fatigue crack growth in layered materials under mixed-mode loading. An inherent assumption of this prior work is that a perfect crack exists along the interface joining the top and bottom layers. The current work extends the approach of previous studies to incorporate a grading of plastic properties between the two layers through parametric finite element modeling with ABAQUS. An elastic-plastic 2D model using 8-node biquadratic elements was used to map the plastic dissipation of a two layer specimen with a grading of plastic properties parallel to the crack face. This property …