Spacecraft structures rely on honeycomb panels to provide a light weight means to support the vehicle. Honeycomb panels can carry significant load but are most vulnerable to structural failure at their joints where panels connect. This research shows that predicting sandwich panel joint capability using finite element analysis (FEA) is possible. This allows for the potential elimination of coupon testing early in a spacecraft design program to determine joint capability. Linear finite element analysis (FEA) in NX Nastran was used to show that adhesive failure can be predicted with reasonable accuracy by including a fillet model on the edge of the fitting. Predicting the ultimate failure of a joint using linear FEA requires that engineering judgment be used to determine whether failure of certain bonds in a fitting will lead to ultimate joint failure or if other bonds will continue to carry the joint's load. The linear FEA model is also able to predict when the initiation of core failure will begin. This has the limitation that the joint will still be able to continue to carry significantly more load prior to joint ultimate failure even after the core has begun to buckle. A nonlinear analysis is performed using modified Riks' method in Abaqus FEA to show that this failure mode is predictable. The modified Riks' analysis showed that nonlinear post-buckling analysis of a honeycomb coupon can predict ultimate core failure with good accuracy. This solution requires a very high quality mesh in order to continue to run after buckling has begun and requires imperfections based on linear buckling mode shapes and thickness tolerance on the honeycomb core to be applied. / Master of Science / Spacecraft structures rely on honeycomb panels to provide a light weight means to support the vehicle. Honeycomb panels consist of two thin metal sheets separated by a light weight honeycomb grid. The panels operate in a similar way to how an I-Beam works on a bridge. These panels can carry significant load but are susceptible to failure because the panels must be glued together when they are built. This research shows that predicting honeycomb panel joint capability using finite element analysis (FEA) is possible. FEA allows the engineer to model and predict failure in complex structures by mathematically combining many small shapes called elements which have known behaviors and properties into the shape of the actual tested article. The elements deflect in a known manner based on the load applied to the model. The honeycomb panel joint is predicted to break when the deflection in a particular element is higher than the element’s material capability. Obtaining the load where the panel breaks is critical information to have during the design of a spacecraft structure. Using the techniques presented in this thesis allows for the potential elimination of coupon testing early in a spacecraft design program to determine joint capability. Coupon testing is where honeycomb panels are built and tested to failure. This testing is very expensive in terms of both cost and program schedule and therefore using analysis to eliminate its need or to reduce its scope provides significant benefit to the spacecraft program.

No description available.

Thesis (M.App.Sc.) - Carleton University, 2002. / Includes bibliographical references (p. 90-94). Also available in electronic format on the Internet.

The purpose of this paper is to develop a general method for using Finite Elements in the Steepest Descent Method. The main application is to a partial differential equation for a Transonic Flow Problem. It is also applied to Burger's equation, Laplace's equation and the minimal surface equation. The entire method is tested by computer runs which give satisfactory results. The validity of certain of the procedures used are proved theoretically. The way that the writer handles finite elements is quite different from traditional finite element methods. The variational principle is not needed. The theory is based upon the calculation of a matrix representation of operators in the gradient of a certain functional. Systematic use is made of local interpolation functions.

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No description available.

This research investigation explores the feasibility of implementing a laser welded sandwich steel panel bridge deck system as a viable alternative to standardized reinforced concrete bridge decks. Generally used in naval ship building applications, steel sandwich panels possess attractive characteristics towards the integration with bridge infrastructure such as service life in excess of 100 plus years, dead load reduction, rapid construction, decreased closure time, and automated mass production. The lack of fatigue data for the laser "stake" welds used to create the enclosed sandwich panel geometry raised concerns with respect to fatigue life. The primary focus of this study was to determine whether or not infinite fatigue life was possible. Two different laser welding technologies were investigated, Laser Beam Welding (LBW) and Hybrid-Laser Arc Welding (HLAW). Test specimens were fabricated and tested in order to examine fatigue resistance based on a localized load effect between adjacent core stiffeners. Finite element models were used to obtain the stress range for each individual test due to complex geometry and partially restrained boundary conditions. In order to assess the fatigue performance of the overall deck system, additional finite element models were created to study the local and global behavior of different sandwich panel configurations. As a whole the investigation yielded promising results. Infinite fatigue life is achievable due to outstanding fatigue performance. The HLAW stake welds demonstrated superior fatigue resistance in comparison to the LBW process. Localized load effects can be minimized through the modification of different panel parameters. Pushing forward, full scale testing is essential to the future employment of this innovative bridge deck system. / Master of Science

This thesis develops an immersed finite element (IFE) space for numerical simulations arising from beam design with multiple materials. This IFE space is based upon meshes that can be independent of interface of the materials used to form a beam. Both the forward and inverse problems associated with the beam equation are considered. The order of accuracy of this IFE space is numerically investigated from the point of view of both the interpolation and finite element solution of the interface boundary value problems. Both single and multiple interfaces are considered in our numerical simulation. The results demonstrate that this IFE space has the optimal order of approximation capability. / Master of Science

Thesis: B.S., Massachusetts Institute of Technology, Department of Mechanical Engineering, 1978 / Includes bibliographical references. / by Arthur P. Cimento. / B.S. / B.S. Massachusetts Institute of Technology, Department of Mechanical Engineering

A direct solution procedure is proposed and developed which exploits the parallelism that exists in current symmetric multiprocessing (SMP) multi-core processors. Several algorithms are proposed and developed to improve the performance of the direct solution of FE problems. A high-performance sparse direct solver is developed which allows experimentation with the newly developed and existing algorithms. The performance of the algorithms is investigated using a large set of FE problems. Furthermore, operation count estimations are developed to further assess various algorithms. An out-of-core version of the solver is developed to reduce the memory requirements for the solution. I/O is performed asynchronously without blocking the thread that makes the I/O request. Asynchronous I/O allows overlapping factorization and triangular solution computations with I/O. The performance of the developed solver is demonstrated on a large number of test problems. A problem with nearly 10 million degree of freedoms is solved on a low price desktop computer using the out-of-core version of the direct solver. Furthermore, the developed solver usually outperforms a commonly used shared memory solver.