Composite Cylindrical Shell Buckling: Simulation & Experimental Correlation

Guidelines dating back 50 years, NASA SP-8007, are employed today in the design of thin-walled launch vehicle structures. Due to advances in materials, structural designs, and manufacturing techniques since the publication of SP-8007, the development of new knockdown factors for contemporary launch vehicle structures is an ongoing subject of...

A Machine Learning Approach to Unresolved-Scale Modeling for Burgers’ Equation

This thesis is part of a greater effort to use machine learning for the development of flexible and universal unresolved-scale models in large eddy simulation (LES). The novelty in the current work is that a neural network learns to predict the integral forms of the unresolved-scale terms directly without a priori assumptions on the underlying...

Simulation of thermal cycle aging process on fiber-reinforced polymers by extended finite element method

The simulation of long life behavior and environmental aging effects on composite materials are subjects of investigation for future aerospace applications (i.e. supersonic commercial aircrafts). Temperature variation in addition to matrix oxidation involves material degradation and loss of mechanical properties. Crack initiation and growth...

Multiscale computational modeling of size effects in carbon nanotube-polymer composites

The development of carbon nanotube(CNT)-polymer composites advocates for a better understanding of their physical and mechanical properties that depend on the diameter of the embedded CNTs. Given that the experimental assessment of size effects is extremely difficult, the use of numerical models can be enormously helpful. However, since size...

Detection of early squats by axle box acceleration

This thesis discusses a new method for detection of short track irregularities, particularly squats, with axle box acceleration (ABA) measurements. A squat is a surface initiated short track defect, associated with high frequency vibrations of the wheel-rail system. High stresses in the contact patch at squats cause accumulation of plastic...

A numerical investigation of the boundary commutation error in large eddy simulation

The boundary commutation error in large eddy simulation is studied numerically. It is shown that an accurate representation of the boundary commutation error has an important role in a reliable large eddy simulation of wall bounded flows. The numerical experiments in this paper are conducted for a 2D channel flow.

Space-time multiscale methods for Large Eddy Simulation

The Variational Multiscale (VMS) method has appeared as a promising new approach to the Large Eddy Simulation (LES) of turbulent flows. The key advantage of the VMS approach is that it allows different subgrid-scale (SGS) modeling assumptions to be made at different ranges of the resolved scales. Typically, in the VMS method, SGS modeling is...

Dynamics of belt systems

Towards digital computer simulation of the dynamics of flexible spacecraft

Software design for digital computer simulation of the dynamics of flexible spacecraft equipped with actuators and sensors, should take into account two properties of the overall system: (i) s.ampled-data control of the spacecraft leads to discontinuous inputs (forcing functions) in the differential equations of motion, thereby requiring...