University of Connecticut University of UC Title Fallback Connecticut



National Science Foundation (NSF): Faculty Early Career Development (CAREER) Award

“Mesoscale Modeling of Defect Structure Evolution in Metallic Materials”

The five year CAREER grant supports research on advancing the understanding of the factors that control the evolution of defects and their structure, the micromechanisms for their evolution, and their collective influence on material performance. The objective of this research is to establish insight into the effects of microstructure and loading conditions on the micromechanisms responsible for the nucleation, accumulation, and interaction of defect structures (dislocations, twins, interfaces) as well as nucleation, growth, and coalescence of voids to form cracks (damage). The research employs a newly developed ‘quasi-coarse-grained dynamics’ (QCGD) method that is able to retain the atomic scale physics of processes involved during deformation and failure but extends the time and length scale capabilities of molecular dynamics simulations. algorithms will be used to map the evolution and distribution of defect structures to the macroscale stress-strain response and identify the distributions that trigger critical events such as damage initiation. This will allow direct connections between the microstructural evolution during deformation and the strength and toughness response for structural metallic materials.

US Army Research Laboratory (ARL): Cold Spray Modeling Program

“Mesoscale Modeling of Single Particle Impact induced Microstructural Evolution during Cold Spray of Aluminum Powders”

The cold spray process involves acceleration of metal particles at supersonic velocities on to a metal substrate. The impact results in severe plastic deformation of the particle and the substrate, and in-turn, bonding of the particle to the substrate. This impact-induced bonding of metal particles forms the basis of the process for coating, repair and additive manufacturing technologies. A critical challenge in the development and optimization of the cold spray process is the current understanding of the dynamic evolution of the microstructure during particle impact. The short time scales (microseconds) and length scales (tens of microns) involved make it extremely challenging to characterize these mechanisms using experiments. The focus of this program aims to model the impact of Al particles with sizes up to tens of microns on to a metal substrate and enable the investigation of the dynamic evolution of microstructure during impact using a newly developed ‘quasi-coarse-grained dynamics’ (QCGD) method. This effort is combined with experimental approaches to investigate the cold spray of precipitation-hardened Al alloys from gas atomized powder feedstocks. This is part of a major multi-institution ARL-funded program aim of this program is to develop robust processing-microstructure-property models for cold-sprayed Al alloys.

US Army Research Laboratory (ARL): Computational & Information Sciences Directorate

“Computational Design of Stacked 2D Layered Materials”

The goal of this program is to gain a fundamental understanding of the relationship between the atomic scale structure, chemistry, strain and the electronic properties of various configurations of stacked 2D materials using atomistic simulations (density functional theory and mole. The proposed research program aims to investigate the electronic properties of various 2D layered nanostructures using density functional theory (DFT) calculations so as to investigate the strain response of monolayer and few-layered structures of 2D materials (MoS2, ReS2, HfS2). In addition, the role of edges is being investigated on the observed electronic response of CVD-grown structures under applied strain. In addition, the molecular dynamics simulations are being carried out to investigate the strain relaxation behavior of CVD-growth structures.

US Army Research Office (ARO): Solid Mechanics Program

“Scaling Relationships for Mesoscale Modeling of Dynamic Failure in Titanium and Titanium Alloys”

The goal of the proposed research program is to develop microstructure-failure-strength relationships at mesoscales in lightweight metallic systems under dynamic loading conditions and bridge the gap between atomistic and continuum simulations. To achieve this goal, a novel mesoscale modeling method called quasi-coarse-grained dynamics (QCGD) is developed that extends the time and length scale capabilities of MD simulations in the mesoscales. The mesoscale behavior is enabled by choosing representative atoms to model the dynamics of several atoms in an atomic scale microstructure. Scaling relationships are used to retain the energetics and the atomic scale degrees of freedom for these representative atoms as well as the missing atoms. The proposed quasi-coarse-grained (QCG) method allows larger size systems and improved time-steps for simulations and is thus able to extend the capabilities of MD simulations to model materials behavior at mesoscales. The proposed research will develop a computationally efficient mesoscale model capable of reproducing the thermodynamic, mechanical, and wave propagation behavior in polycrystalline α-Ti and Ti alloys (Ti-6Al-4V) and identify the links between microstructure and failure-strength at mesoscales and bridge the gap between atomic simulations and continuum simulations.



Pratt & Whitney: UConn Additive Manufacturing Innovation Center

“Computational and Experimental Studies of Laser-Powder Interactions for Additive Manufacturing”

  The proposed research addressed the question how variations in powder pedigree and temperature maxima during additive manufacturing affect the melting behavior of Ti-6Al-4V powder beds. The melting and fusion stage during which the powder bed locally transforms into a liquid pool largely determines the formation of defects such as voids, pores, or un-melted regions in the final product. The fusion of powder particles depends on the viscosity of the liquid alloy, the surface energies, capillary effects, and hence implicitly on the composition, temperature, and atmosphere. Alloy powder compositions, including impurities, change with the number of recycles, but also due to batch-to-batch variations and differences in composition specifications from different powder vendors. Large scale molecular dynamics simulations were carried out to compute the viscosity of Ti powder particles as well as to investigate the phenomena of melting and the propagation of the melt-front.