Browsing by Author "Brake, Matthew RW"
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Item Dissipative Dynamics of Bolted Joints(2021-08-11) Balaji, Nidish; Brake, Matthew RWBolted Joints finds ubiquitous applications in mechanical and allied industries, spanning from household appliances to advanced aerospace applications. The currently prevalent practice in the design industry, when it comes to bolted joints, is to over-design these components to a very large extent so one needs not pay too much attention to the exact physical properties of these joints, which are fundamentally nonlinear. The current study seeks to advance understanding of the fundamental physical phenomena typifying bolted joints through a two-pronged approach: theoretical and modeling. In the theoretical portion of the work, advances in computational modeling techniques pertinent to the nonlinear characterization of such structures, including a novel Nonlinear Modal Analysis (NMA) approach and interface reduction approaches, are presented which enable the studies in the final portion of the work. In the Modeling portion of the work, two approaches, an empirical and a physics-based approach, are presented. While in the former, the exact form of the contact representation is of secondary importance and the parameters are optimized against experimental data, the latter is an attempt at making blind predictions of the dynamics of a structure assembled through bolted joints. Additionally, the physics-based model is studied using an uncertainty quantification approach in order to throw light on the exact manner in which each parameter of the model influences the predictions. Finally, the thesis closes with recommendations for future work based on the investigations undertaken herein.Item Dissipative Dynamics of Bolted Joints(2021-08-11) Balaji, Nidish; Brake, Matthew RWBolted Joints finds ubiquitous applications in mechanical and allied industries, spanning from household appliances to advanced aerospace applications. The currently prevalent practice in the design industry, when it comes to bolted joints, is to over-design these components to a very large extent so one needs not pay too much attention to the exact physical properties of these joints, which are fundamentally nonlinear. The current study seeks to advance understanding of the fundamental physical phenomena typifying bolted joints through a two-pronged approach: theoretical and modeling. In the theoretical portion of the work, advances in computational modeling techniques pertinent to the nonlinear characterization of such structures, including a novel Nonlinear Modal Analysis (NMA) approach and interface reduction approaches, are presented which enable the studies in the final portion of the work. In the Modeling portion of the work, two approaches, an empirical and a physics-based approach, are presented. While in the former, the exact form of the contact representation is of secondary importance and the parameters are optimized against experimental data, the latter is an attempt at making blind predictions of the dynamics of a structure assembled through bolted joints. Additionally, the physics-based model is studied using an uncertainty quantification approach in order to throw light on the exact manner in which each parameter of the model influences the predictions. Finally, the thesis closes with recommendations for future work based on the investigations undertaken herein.Item Investigating the Influence of the Radius of Curvature in Elastic-Plastic Spherical Contact(2020-04-23) ONeill, Eoghan Oisin; Brake, Matthew RWThe study of elastic-plastic contact mechanics is fundamental in understanding the multi-scale behavior of mechanical systems. The e ects of the varying the radius of curvature in elastic-plastic asperity contact, and resulting impact on contact parameters, has been largely neglected in previous studies. A typical approach for elastic-plastic contact models is to assume the equivalent radius of curvature from Hertzian theory is valid in this regime. To assess the applicability of this assumption, contact between two spheres is modeled with FEA. For two elastic- plastic spheres, the ratio of the radii of curvature and material models are varied to encompass the range of flattening to indentation scenarios. Comparisons to contact models are shown and trends are observed indicating the significance of the effect of the radius of curvature on elastic-plastic contact. Finally, a formulation for contact parameters as a function of radii of curvature during contact is proposed.Item Thermal Spray Coating Characterization via Higher Dimensional Surfaces(2022-12-02) Ahadzie, Senyo Evan; Brake, Matthew RWThermal spray coatings are microscale coatings used to improve the surface properties of surfaces they are applied to. Statistical quantification can improve understanding of a thermal coating's microstructure; however, doing so in an automatic and autonomous manner from image data is non-trivial. A new methodology is developed to characterize thermal spray coatings from serial sectioning images (or other analogous image data) using manifold surfaces in higher dimensions, as well as associated operators on such data.