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Full-Text Articles in Engineering
Evolution Of The Pore Size Distribution In Sheared Binary Glasses, Nikolai V. Priezjev, Maxim A. Makeev
Evolution Of The Pore Size Distribution In Sheared Binary Glasses, Nikolai V. Priezjev, Maxim A. Makeev
Mechanical and Materials Engineering Faculty Publications
Molecular dynamics simulations are carried out to investigate mechanical properties and porous structure of binary glasses subjected to steady shear. The model vitreous systems were prepared via thermal quench at constant volume to a temperature well below the glass transition. The quiescent samples are characterized by a relatively narrow pore size distribution whose mean size is larger at lower glass densities. We find that in the linear regime of deformation, the shear modulus is a strong function of porosity, and the individual pores become slightly stretched while their structural topology remains unaffected. By contrast, with further increasing strain, the shear …
Wettability Tailoring Of Nanotube Carpets: Morphology-Chemistry Synergy For Hydrophobic–Hydrophilic Cycling, Lymeng He, Anil Karumuri, Sharmila M. Mukhopadhyay
Wettability Tailoring Of Nanotube Carpets: Morphology-Chemistry Synergy For Hydrophobic–Hydrophilic Cycling, Lymeng He, Anil Karumuri, Sharmila M. Mukhopadhyay
Mechanical and Materials Engineering Faculty Publications
Carpet-like arrays of carbon nanotubes (CNTs) on graphitic carbon materials have been investigated in order to understand all-carbon hierarchical structures for multifunctional surface-active devices. Pure CNT carpets are seen to be super-hydrophobic as long as they are well aligned. For future applications involving aqueous environments, the ability to tailor the surface wettability and switch it on demand can be very useful, and enable unprecedented devices related to microfluidics, catalysis and sensing/detection systems. In this study, microwave plasma treatments were used to functionalize CNT carpets for a progressive increase in wettability so that they could eventually become super-hydrophilic. This change could …
Collective Nonaffine Displacements In Amorphous Materials During Large-Amplitude Oscillatory Shear, Nikolai V. Priezjev
Collective Nonaffine Displacements In Amorphous Materials During Large-Amplitude Oscillatory Shear, Nikolai V. Priezjev
Mechanical and Materials Engineering Faculty Publications
Using molecular dynamics simulations, we study the transient response of a binary Lennard-Jones glass subjected to periodic shear deformation. The amorphous solid is modelled as the three-dimensional Kob-Andersen binary mixture at a low temperature. The cyclic loading is applied to slowly annealed, quiescent samples, which induces irreversible particle rearrangements at large strain amplitudes, leading to stress-strain hysteresis and a drift of the potential energy towards higher values. We find that the initial response to cyclic shear near the critical strain amplitude involves disconnected clusters of atoms with large nonaffine displacements. In contrast, the amplitude of shear stress oscillations decreases after …
Identifying Two Regimes Of Slip Of Simple Fluids Over Smooth Surfaces With Weak And Strong Wall-Fluid Interaction Energies, Haibao Hu, Luyao Bao, Nikolai V. Priezjev, Kai Luo
Identifying Two Regimes Of Slip Of Simple Fluids Over Smooth Surfaces With Weak And Strong Wall-Fluid Interaction Energies, Haibao Hu, Luyao Bao, Nikolai V. Priezjev, Kai Luo
Mechanical and Materials Engineering Faculty Publications
The slip behavior of simple fluids over atomically smooth surfaces was investigated in a wide range of wall-fluid interaction (WFI) energies at low shear rates using non-equilibrium molecular dynamics simulations. The relationship between slip and WFI shows two regimes (the strong-WFI and weak-WFI regimes): as WFI decreases, the slip length increases in the strong-WFI regime and decreases in the weak-WFI regime. The critical value of WFI energy that separates these regimes increases with temperature, but it remains unaffected by the driving force. The mechanism of slip was analyzed by examining the density-weighted average energy barrier (∆E) encountered by fluid atoms …
Four-Terminal Square Piezoresistive Sensors For Mems Pressure Sensing, Awlad Hossain, Ahsan Mian
Four-Terminal Square Piezoresistive Sensors For Mems Pressure Sensing, Awlad Hossain, Ahsan Mian
Mechanical and Materials Engineering Faculty Publications
The sensitivity of four-terminal piezoresistive sensors commonly referred to as van der Pauw (VDP) structure is investigated. The VDP sensor is considered to be fabricated on (100) silicon due to its potential application in MEMS (microelectromechanical systems) pressure sensors. The sensitivity of the VDP sensor may be affected by misalignment during the etching/diffusion process, the nonuniformity of piezoresistive coefficients through the sensor thickness, and pad size with respect to the sensor size. For this particular analysis, the effect of VDP stress sensitivity on variations in pad sizes and through-the-thickness -coefficient variation are studied as the effect of misalignment has already …
Defect Engineering: A Path Toward Exceeding Perfection, Hamed Attariani, Kasra Momeni, Kyle R. Adkins
Defect Engineering: A Path Toward Exceeding Perfection, Hamed Attariani, Kasra Momeni, Kyle R. Adkins
Mechanical and Materials Engineering Faculty Publications
Moving to nanoscale is a path to get perfect materials with superior properties. Yet defects, such as stacking faults (SFs), are still forming during the synthesis of nanomaterials and, according to common notion, degrade the properties. Here, we demonstrate the possibility of engineering defects to, surprisingly, achieve mechanical properties beyond those of the corresponding perfect structures. We show that introducing SFs with high density increases the Young’s Modulus and the critical stress under compressive loading of the nanowires above those of a perfect structure. The physics can be explained by the increase in intrinsic strain due to the presence of …