Mechanical Engineering Commons^™

Modeling The Effects Of Manufacturing Geometric Imperfections In The Buckling Analysis Of Three-Dimensional Structures, Juan Carlos Salcido

Open Access Theses & Dissertations

Reticulated three-dimensional structures follow design practices based on the common assumption that joints are either rigid, or pinned. However, the actual non-linear behavior of the jointing system interaction is required to be incorporated into the analysis of the structure to accurately predict its buckling stability. Besides, currently, there is a concern on how manufacturing imperfections of these jointing systems affect the global behavior of three-dimensional structures. This Dissertation incorporates and captures the effect that manufacturing geometric imperfections in the fir-tree jointing system produce in the non-linear buckling behavior of three-dimensional structures.

To understand the effect that initial manufacturing imperfections of …

Comparison Study Between Fem And Sem For Wave Propagation Models Applied To Solids, Shaddy Roberto Castillo Ponton

Open Access Theses & Dissertations

Wave propagation is a field whose application has spread across many disciplines. In the field of structural engineering, wave propagation methods have focused their attention specifically in the area of structural health monitoring and active control of vibrations and noise. Likewise, the development of new methods and their application have been successful in the area of material science with a special emphasis on the field of structural integrity evaluation of anisotropic and inhomogeneous structures (laminated composite structures). The current available analysis tools are inadequate to handle the modeling of complex structures. One-dimensional wave propagation problems in solids are still a …

Improved Joining Method For Segmental Prestressed Structures, Ralph Warren Jensen

Open Access Theses & Dissertations

This dissertation addresses the need for more robust and materially efficient structures, specifically structures that absorb higher levels of energy, can self-erect and which have variable reaction capabilities. These structures can take much higher levels of strain and loading compared to current technologies in reinforced concrete and carbon fiber composites. These structures are made using a novel method of joining segmental elements. A great advantage with this segmental structural system is it's survivability under overloaded conditions. During an impact, or concentrated pressure load, the structure will wrap around the impact zone thereby widely distributing the contact stresses. This function or …

Study Of Probabilistic Approach For Structural Health Assessment Of Aerospace Structures, Jose Antonio Garcia

Open Access Theses & Dissertations

Current practical approaches used in structural health assessment programs of aerospace structures involve performing a fracture mechanics analysis to verify the safe life of structural components. The analysis typically makes several conservative assumptions implemented by NASA fracture control standard practices for critical structural components. This well-established paradigm for fracture control follows a deterministic approach and, in some cases, the calculations may produce overly conservative remaining life estimates.

This thesis describes the results of a study to approach the health assessment challenge of several critical components using probabilistic methods. The probabilistic analysis takes the current deterministic model and identifies variables that …

Evaluation Methods For Health Monitoring Of Aerospace Structure Rotary Joints, Sergio Armando Navarro

Open Access Theses & Dissertations

In September 2007, the excessive vibrations played a significant role in the station operation since one of the rotary joints, which provides the station electrical energy, presented an anomaly. The replacement of its bearing components and re-lubrication were necessary to reduce the problem. To avoid a new anomaly, the inspection of the rotary joints performance continues by using the accelerometers data. This thesis presents three new approaches to monitor the vibrations at the International Space Station based on Root-Mean-Square, kurtosis, and Approximate Entropy (ApEn). MATLAB functions and codes were necessary to implement the three monitoring techniques results from the provided …