The objective of the proposed research is to establish a new atomistic-to-continuum thermomechanical model for describing the relation between atomistic (microscopic) quantities and continuum (macroscopic) quantities in solids. The proposed model allows the development of novel multiscale denoising (averaging) method employed to decompose the dynamical quantities obtained from nonequilibrium molecular dynamics (MD) simulations into their respective local thermal and mechanical contributions. In the proposed research, the thermomechanical model will be established by 1) testing the Gaussian approximation and temperature estimation, 2) developing a multiscale spatial-temporal thresholding estimator, 3) testing the thermomechanical additive model with the new multiscale averaging method, and 4) estimating the continuum stress using the new averaging method.
The successful completion of the proposed research will impact a number of disciplines that include mechanics, heat transfer, signal processing, and nonparametric statistics. For example, new multiscale method coupling MD and finite element methods for simulating nonequilibrium thermomechanical processes will be made possible to extend the time and spatial scale of MD simulation. Nanotechnology applications such as laser ablation for nanoscale patterning and laser-assisted imprinting will be benefited tremendously from the proposed research. Efforts to broaden the participation of students including the underrepresented ones include 1) organizing ?nanotechnology visualization? workshops for high schools students in the larger Pittsburgh area, 2) building an interaction platform for high school students in San Francisco, and 3) introducing a new course in computational nanomechanics. These activities will integrate new research results and concepts from this proposal.
The objective of the proposed research is to establish a new atomistic-to-continuum thermomechanical model for describing the relation between atomistic (microscopic) quantities and continuum (macroscopic) quantities in solids. The major activities include: 1) Obtained continuum mechanical/thermal displacement and velocity based on a thermomechanical model using different linear and non-linear denosing methods, 2) Employed ensemble averaging method to obtain continuum mechanical/thermal displacement and velocity, 3) Computed macroscopic thermomechanical quantities from atomistic level information using Hardy’s expressions, and apply the ensemble averaging method to obtain the expectation values of Hardy’s thermomechanical quantities, and 4) Organized nanoengineering workshops and lectures for underrepresented high school students. The key results from this research included: 1) Showed that nonlinear wavelet-based estimators are more accurate than linear filters for computing continuum thermomechanical quantities from MD simulations, 2) Demonstrated that ensemble averaging of MD simulations is capable of determining the thermomechanical state of an atom in a nonequilibrium solid system, 3) Made modifications to Hardy’s thermomechanical theory so that it conserves various fundamental properties more accurately, and 4) Demonstrated that the modified Hardy’s thermomechanical quantities computed from the atomistic quantities can obey continuum conservation equations regardless of characteristic volume size, atomic potential form and crystal structure. For education, this project has provided research and training opportunities for the two graduate students and four undergraduate students, which include a female and an African American student. Both of these graduate students have obtained their PhDs. Two of these undergraduate researchers have authored two journal publications together with the PI. The nanoengineering workshop has benefited a total of ~50 high school students from underrepresented groups. Besides, the graduate students and undergraduate students who participated in this activity also gained valuable teaching experience. Lectures on nanotechnology at the PI's alma mater have benefited a total of ~300 high school students. The outcome of the proposed research will impact a number of disciplines that include mechanics, heat transfer, signal processing, and nonparametric statistics. For example, new multiscale method coupling MD and finite element methods for simulating nonequilibrium thermomechanical processes will be made possible to extend the time and spatial scale of MD simulation. Nanotechnology applications such as laser ablation for nanoscale patterning and laser-assisted imprinting will be benefited tremendously from the proposed research. The integrated research and educational program ensures the US’s continued leadership in simulation-based engineering and science. The outreach activities helps address the wide wealth gap in the US by improving the educational level of underrepresented minority high school students from low income families.
