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Articles 1 - 8 of 8
Full-Text Articles in Engineering Science and Materials
Nonlinear Acoustics Of Piston-Driven Gas-Column Oscillations, Andrew William Wilson
Nonlinear Acoustics Of Piston-Driven Gas-Column Oscillations, Andrew William Wilson
Masters Theses
The piston-driven oscillator is traditionally modeled by directly applying boundary conditions to the acoustic wave equations; with better models re-deriving the wave equations but retaining nonlinear and viscous effects. These better models are required as the acoustic solution exhibits singularity near the natural frequencies of the cavity, with an unbounded (and therefore unphysical) solution. Recently, a technique has been developed to model general pressure oscillations in propulsion systems and combustion devices. Here, it is shown that this technique applies equally well to the piston-driven gas-column oscillator; and that the piston experiment provides strong evidence for the validity of the general …
Design, Fabrication, Structural Testing, And Numerical Analysis Of A Small Scale Composite Wing, Jacob David Gaunt, Juan Carlos Flores, Vincent Andrew Perry
Design, Fabrication, Structural Testing, And Numerical Analysis Of A Small Scale Composite Wing, Jacob David Gaunt, Juan Carlos Flores, Vincent Andrew Perry
Aerospace Engineering
A small scale composite wing based on a design found on an experimental aircraft was designed, constructed, and tested dynamically and statically. The wing was constructed similarly to an experimental aircraft wing. The performed static test was intended to produce pure bending. Strain gages were used to measure strains on the wing structure. The strains were converted to stresses to aid in analysis. The static test results suggested that the wing was actually under torsion. Four structural modes were found from the static test. A finite element analysis model was made to compare experimental results to numerical analytical results. The …
Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D.
Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D.
Department of Engineering Mechanics: Faculty Publications
In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement (m-convergence) and under decreasing the peridynamic horizon (δ-convergence). Comparisons with experimentally obtained values are made for the crack-tip propagation speed with three different peridynamic horizons.We also analyze the influence of the particular shape of themicro-modulus function and of different materials (Duran 50 glass and soda-lime glass) on the crack propagation behavior. We show that the peridynamic solution for this problem captures all the main features, observed experimentally, of dynamic crack propagation and branching, as well …
Multiscale Transformation Field Analysis Of Progressive Damage In Fibrous Laminates, Yehia Bahei-El-Din, Ritesh Khire, Prabhat Hajela
Multiscale Transformation Field Analysis Of Progressive Damage In Fibrous Laminates, Yehia Bahei-El-Din, Ritesh Khire, Prabhat Hajela
Centre for Advanced Materials
As part of an ongoing effort to model uncertainty propagation across multiple scales in fibrous laminates, this paper presents a deterministic transformation field analysis for modeling damage progression under membrane forces and bending moments. In this approach, equivalent eigenstresses are computed in the phases and/or plies such that their respective stress components that satisfy the underlying failure criteria are reduced to zero. Superposition of the solutions found for the undamaged laminate under applied loads and under the eigenstress field provide the entire response. Failure criteria are based on stress averages in the fiber and matrix. Damage mechanisms considered are frictional …
Modified Sandwich Structures For Improved Impact Resistance Of Wind Turbine Blades, Yehia Bahei-El-Din, Mostafa Shazly, I. El-Habbal, Y. Elbahy
Modified Sandwich Structures For Improved Impact Resistance Of Wind Turbine Blades, Yehia Bahei-El-Din, Mostafa Shazly, I. El-Habbal, Y. Elbahy
Centre for Advanced Materials
Wind turbine blades are susceptible to damage due to fatigue as well as impact by flying objects and parts broken off failed blades of nearby wind towers. Localized, permanent compression of the foam core and delamination of the fibrous composite face sheets are typical damage modes and can lead to progressive structural failure. Sandwich structures modified by inclusion of flexible polyurethane (PU) layers within the cross section are examined under both impact and dynamic loads. Finite element models of sandwich structures with conventional and modified designs show that sandwich designs modified with PU interlayes exhibit reduced foam core crushing and …
Adaptive Pid Control Based On Rbf Network Approximating The Satellite Clock Thermal Model, Bin Xu
Adaptive Pid Control Based On Rbf Network Approximating The Satellite Clock Thermal Model, Bin Xu
Bin Xu
The accuracy o f t ime information prov ided by sate llite clock g reat ly depends on its frequency stab ili ty, w hich is up to the stability o f the co re tempera ture. Th is paper introduces an adaptive PID control for the sate llite c lock system whose mode l is approx imated based on RBF neural netw orks. Simu lation resu lts demonstrate the va lid ity o f the proposed contro.l
Processing Of Zrb2-Zrc-Zrxsiy Ceramic By Reactive Metal Penetration, Nischel B. Maheswaraiah
Processing Of Zrb2-Zrc-Zrxsiy Ceramic By Reactive Metal Penetration, Nischel B. Maheswaraiah
Open Access Theses & Dissertations
The processing of ZrB2-ZrC-ZrxSiy composite by reactive metal penetration was investigated as a successor to the ZrB2-SiC composites for hypersonic vehicles application, which cannot be used for extended time at temperatures greater than 1600C due to formation of SiO and CO gases. Zirconium (Zr), zirconium disilicide (ZrSi2), and boron carbide (B4C) were reacted in graphite crucibles for 60, 120, 180, and 240 minutes. Microscopy and x-ray diffraction (XRD) deduced the formation of a heterogeneous microstructure of ZrB2-ZrC-ZrxSiy precipitates surrounded by a solidified Zr-Si melt. Unreacted boron carbide was observed in samples held at 1860C for 60 minutes and 120 minutes, …
Microstructure Investigation Of Al-Rich Titanium Aluminum Alloys, David Pham
Microstructure Investigation Of Al-Rich Titanium Aluminum Alloys, David Pham
Open Access Theses & Dissertations
The microstructures of Ti-Al alloys with 70-80 wt% Al were investigated. Aluminum wire (99.999%) and TiH2 powder (99.7%) were used to produce the sample compositions inside a vertical tube furnace at 1600oC in an Ar atmosphere. Argon is purified through a dehumidification and deoxidation system. Magnesium perchlorate Mg(ClO4)2 acts as a desiccant and titanium sponge pulls oxygen from the Ar in furnaces operating at 800oC and 750oC. X-ray diffraction and an optical microscope are used to identify phases and compositions