A5076922387- Numerical methods in engineering
- Microstructure and mechanical properties
- Tribology and Lubrication Engineering
- Structural Response to Dynamic Loads
- Silicone and Siloxane Chemistry
- Composite Material Mechanics
- Aluminum Alloys Composites Properties
- High-Velocity Impact and Material Behavior
- Bladed Disk Vibration Dynamics
- Turbomachinery Performance and Optimization
- Advanced ceramic materials synthesis
- Computational Fluid Dynamics and Aerodynamics
- Energetic Materials and Combustion
- Fatigue and fracture mechanics
- Polymer Nanocomposites and Properties
- Adhesion, Friction, and Surface Interactions
- Elasticity and Material Modeling
- Gas Dynamics and Kinetic Theory
- Polymer crystallization and properties
- Advanced Mathematical Modeling in Engineering
- Polynomial and algebraic computation
- Surface and Thin Film Phenomena
- Block Copolymer Self-Assembly
- Laser and Thermal Forming Techniques
- Machine Learning in Materials Science
Arizona State University
2013-2024
Université d'Évry Val-d'Essonne
2017
Technical Solutions (United States)
2005-2013
Arianespace (France)
2012
Northwestern University
2007-2011
Applied Technical Services (United States)
2005
Case Western Reserve University
2004
Polyurea is an alternating copolymer with excellent viscoelastic properties for dissipating shock and impact loads; however, a molecular-level understanding of how its chemistry relates to performance remains elusive. While molecular dynamics simulations can in theory draw connections between structure properties, practice the long relaxation times associated polymer make such calculations prohibitively expensive. To address this issue, we have developed coarse-grained (CG) model polyurea...
ABSTRACT To explore the relationship between microscopic structure and viscoelastic properties of polyurea, a coarse‐grained (CG) model is developed by matching method validated against experiments conducted on controlled, benchmark material. Using Green‐Kubo method, relaxation function computed from autocorrelation stress tensor, sampled over equilibrium MD simulations, mapped to real time scale established self‐diffusion rates atomistic CG models. Master curves predicted are then compared...
We investigate the thermomechanical response of semi-crystalline polyethylene under shock compression by performing molecular dynamics (MD) simulations using a new coarse-graining scheme inspired embedded atom method. The combines iterative Boltzmann inversion method and least squares optimization to parameterize interactions between coarse-grained sites, including many-body potential energy designed improve representability model across wide range thermodynamic states. demonstrate that...
In this work we apply a material-frame, kernel-based estimator of continuum fields to atomic data in order estimate the J-integral for analysis an atomically sharp crack at finite temperatures. Instead potential energy appropriate zero temperature calculations, employ quasi-harmonic free as Helmholtz required by Eshelby stress isothermal conditions. We simplest models, local harmonic model LeSar and co-workers, verify that it is adequate correction expression various deformation states our...
SUMMARY An adaptive atomistic‐to‐continuum method is presented for modeling the propagation of material defects. This extends bridging domain to allow atomic dynamically conform evolving defect regions during a simulation, without introducing spurious oscillations and requiring mesh refinement. The expands as defects approach coupling by fine graining nearby finite elements into equivalent atomistic subdomains. Additional algorithms coarse grain portions continuum scale, reducing degrees...
A dual-bell nozzle has been tested in the ONERA-R2Ch wind tunnel within CNES PERSEUS program. The wall pressure distributions and thrust for two flow regimes have characterized ratio (NPR) range from 51 up to 597. hysteresis on transition NPR between observed according evolution of NPR. duration switch is less than 10 ms. about 20% also a direct effect thrust. total becomes higher isolated base without extension > 1500. phenomenon modeled with use supersonic separation criteria by making...
Summary A numerical scheme based on the eXtended Finite Element Method (XFEM) is proposed to simulate complex fluid flow in a fractured porous reservoir. By enriching elements fully cut by fracture and near‐tip region, mechanism including tip flux singularity can be exactly represented XFEM formulation. Fluid transfer between matrix fractures easily coupled, also overcomes sensitivity mesh used traditional unstructured discretizations, regardless of complexity network. The method validated...
Polyurea, an elastomer with a phase-segregated microstructure, has been proven as effective coating in defense applications. To gain more complete understanding of the high-pressure atomic-level morphology these phases and to validate molecular dynamics (MD) simulations, multi-angle energy-dispersive X-ray diffraction experiments were performed situ up pressures ∼6 GPa at room temperature. Structure factors obtained compared MD simulations average error less than 5% between major peak...
We combine the extended finite element method with simulations of diffracted x-ray intensities to investigate diffusely scattered intensity due dislocations. As a model system thin PbSe epitaxial layer grown on top PbTe buffer CdTe substrate was chosen. The film shows periodic dislocation network where dislocations run along orthogonal ⟨110⟩ directions. array within this can be described by short range order narrow distribution.
ABSTRACT In an effort to accelerate simulations exploring deformation mechanisms in semicrystalline polymers, we have created structure‐based coarse‐grained (CG) models of polyethylene and evaluated the extent which they can simultaneously represent its amorphous crystalline phases. Two CG were calibrated from target data sampled atomistic supercooled oligomer melts that differ how accurately distribution bond lengths between sites. Both yield morphology when are performed at ambient...
Mechanical degradation due to brittle intermetallic compounds (IMCs) formed at the faying interface is a predominant deficiency in dissimilar metal joints. In copper/aluminum (Cu/Al) joints, additional defects (such as partially-bonded interfaces, porosity and cracks) lead further weakened strength lowered electrical conductivity. this study, nickel‑phosphorus (Ni-P) coatings are deposited on Al address these issues. With aid of Ni-P coatings, detrimental Cu-Al IMC eliminated, donut-shaped...
Abstract This paper presents a higher‐order method for modeling dislocations with the extended finite element (XFEM). is applicable to complex geometries, interfaces lattice mismatch strains, and both anisotropic spatially non‐uniform material properties. A numerical procedure computing J‐integral around dislocation core determine energy release rate virtual advance of line described. Several examples in three dimensions illustrate applicability this semiconductor heterostructures,...
A universal docking and berthing system is being developed by the National Aeronautics Space Administration (NASA) to support all future space exploration missions low-Earth orbit (LEO), Moon, Mars. An investigation of compression set two seals mated in a seal-on-seal configuration force required separate after periods mating was conducted. The leakage rates made from silicone elastomer compounds, S0383-70 S0899-50, configured were quantified. test specimens sub-scale with representative...
A simplified implementation of the conventional extended finite element method (XFEM) for dynamic fracture in thin shells is presented. Though this uses same linear combination XFEM, it allows considerable simplifications discontinuous displacement and velocity fields shell elements. The proposed implemented discrete Kirchhoff triangular (DKT) element, which one most popular elements engineering analysis. Numerical examples failure under impulsive loads including implosion explosion are...
The application of computational modeling to design can greatly reduce the expense and development time engineered components. success a model in representing correct behavior components is contingent on accuracy material models used. In this work, constitutive three space-grade silicone elastomers, Esterline ELA-SA-401, Parker Hannifln S0383-70 S0899-50, flt hyperelastic from experimental data. properties these materials are presented along with friction, thermal, other bulk properties....