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High Magnification Surface Topography Based Digital Image Correlation (Dic) For Identifying Damage Accumulation And Crack Growth In Polycrystalline Nickel, Arash Valiollahi
High Magnification Surface Topography Based Digital Image Correlation (Dic) For Identifying Damage Accumulation And Crack Growth In Polycrystalline Nickel, Arash Valiollahi
Mechanical and Aerospace Engineering Dissertations
Damage index parameters that have been formulated to identify damage localization in plastically deformed materials typically require all six stress or strain components. Recently, simulations through Crystal Plasticity Finite Element Method (CPFEM) have been widely used to extract damage initiation parameters. However, these models are rarely verified due to the challenges in measuring the out-of-plane deformation/strain experimentally. A damage index combining the effective plastic strain and surface roughness change is investigated for identifying damage accumulation sites and predicting crack propagation path in polycrystalline pure Nickel. A novel Digital Image Correlation (DIC) technique is developed to measure both in-plane and out-of-plane …
Fatigue Performance Modeling In Advanced Out-Of-Autoclave Composites For Aerospace Applications, Grayson Reid Curry
Fatigue Performance Modeling In Advanced Out-Of-Autoclave Composites For Aerospace Applications, Grayson Reid Curry
Mechanical and Aerospace Engineering Theses
Increased application of composite materials in the military and civil applications renewed the interest to development of high-fidelity methodologies for predicting their performance characteristics. Besides the traditional autoclave processed structural composites such as IM7/8552 and IM7/977-3 widely used on various platforms, novel materials such IM7/5320-1 suitable for Out-of-Autoclave (OoA) cure became of interest. Static and fatigue performance prediction of Open-Hole quasi-isotropic laminates made from IM7/5320-1 was performed in this work by using the Finite Element Analysis software BSAM. Progressive failure simulation including delaminations, matrix cracks and fiber failure was performed. Regularized eXtended Finite Element Methods (RXFEM) was used for mesh …
Characterization Of Fatigue Strength Of Additively Manufactured Ti-6al-4v With Recoater Blade Interference Flaws And Residual Stresses Towards An Enhanced Fatigue Substantiation Methodology For Aerospace Structures Applications, Joshua Manyara Mochache
Mechanical and Aerospace Engineering Dissertations
This research characterized the fatigue strength of additively manufactured (AM) Ti-6Al-4V, through fatigue and static tests conducted using specimens with and without recoater blade interference flaws (RBIF), and thus further enhanced the fatigue substantiation methodology for AM parts by using combined fatigue strength knock-down-factors (KDF) developed from this study. Qualification and certification (Q&C) of metallic AM parts, through acceptable methods for fatigue and damage tolerance (F&DT) substantiation, is an area where significant gaps still exist. While progress has been made in design as well as materials and process standardization, Q&C of additively manufactured metallic structural parts, especially those in civil …
Characterization And Enhancement Of Fatigue And Fracture Properties In Thermoplastic Fff Parts Using In-Situ Annealing, Manjarik Mrinal
Characterization And Enhancement Of Fatigue And Fracture Properties In Thermoplastic Fff Parts Using In-Situ Annealing, Manjarik Mrinal
Mechanical and Aerospace Engineering Dissertations
Fused filament fabrication (FFF) show high anisotropy and reduced mechanical properties as compared to conventional manufacturing techniques. This happens due to the poor interlaminar bonding between the layers, as a result of premature halt of bond healing process. Previous research works show multiple approaches to improve the bond quality to enhance the mechanical properties of FFF parts, however these are complex and expensive techniques. In this work a novel print head assembly is presented to offer a simple and effective solution by applying a thermal field to the part as it is being printed to preheat the previously deposited layer, …
Prediction Of Solder Joint Fatigue Life Of Photonic Package Using ?-? Materials, Ojas Tyagi
Prediction Of Solder Joint Fatigue Life Of Photonic Package Using ?-? Materials, Ojas Tyagi
Mechanical and Aerospace Engineering Theses
Fatigue life prediction has become very important factor in reliability of any electronic components to withstand extreme thermal stresses in industrial standard. Hence, photonic packages are widely used in telecommunication and computer applications. The primary focus of this study is to determine the thermal cycles to crack initiation of solder bump used in laser array waferboard for telecommunication applications. This includes GaAs Laser chip on waferboard and Si substrate with pure Indium solder balls in between. Indium has proved higher fatigue life in various experimental studies in the field of reliability and lead-free material. Therefore, a solder ball was designed …
An Analytical Design Of Experiments Method For Fatigue Constrained Design Optimization Of A 3d Printed Structure, Ashish Pokharel
An Analytical Design Of Experiments Method For Fatigue Constrained Design Optimization Of A 3d Printed Structure, Ashish Pokharel
Mechanical and Aerospace Engineering Theses
A design of experiments approach has been used to analytically determine a low cycle fatigue (LCF) constraint for use in design optimization of 3D printed structures. In context of metal additive manufacturing, the process of melting, solidification and consolidation of metal powder introduces very high temperature gradient field within the build which in turn results in high compressive stresses at the core and tensile stresses at the outer surface of the part after it has cooled down to room temperature post build. An approach of finite element modeling in ANSYS Additive has been used to develop a residual stress profile …