Seunghwa Ryu

Stress-strain curves are an important representation of a material's mechanical properties, from which important properties such as elastic modulus, strength, and toughness, are defined. However, generating stress-strain curves from numerical methods such as finite element method (FEM) is computationally intensive, especially when considering the entire failure path for a material. As a result, it is difficult to perform high throughput computational design of materials with large design spaces,

Dislocation nucleation is essential to our understanding of plastic deformation, ductility, and mechanical strength of crystalline materials. Molecular dynamics simulation has played an important role in uncovering the fundamental mechanisms of dislocation nucleation, but its limited timescale remains a significant challenge for studying nucleation at experimentally relevant conditions. Here we show that dislocation nucleation rates can be accurately predicted over a wide range of conditions by

While the classical nucleation theory (CNT) is widely used to predict the rate of first-order phase transitions, its validity has been questioned due to discrepancies with experiments. We systematically test the individual components of CNT by computer simulations of the Ising models and confirm its fundamental assumptions under a wide range of conditions ( h=0.01-0.13J , T=0.44-0.84Tc in two-dimensions and h=0.30-0.60J , T=0.48-0.62Tc in three dimensions). First, CNT accurately predicts the nuc

Due to the difficulty of performing uniaxial tensile testing, the strengths of graphene and its grain boundaries have been measured in experiments by nanoindentation testing. From a series of molecular dynamics simulations, we find that the strength measured in uniaxial simulation and the strength estimated from the nanoindentation fracture force can differ significantly. Fracture in tensile loading occurs simultaneously with the onset of crack nucleation near 5-7 defects, while the graphene she

We report melting points and other thermal properties of several semiconducting and metallic elements as they are modeled by different empirical interatomic potential models, including the Stillinger–Weber, the embedded-atom method, the Finnis–Sinclair and the modified-embedded-atom method. The state-of-the-art free energy methods are used to determine the melting points of these models within a very small error bar, so that they can be cross-compared with each other. The comparison reveals seve

The modified embedded-atom method interatomic potentials for pure gold and pure silicon are improved in their melting point and latent heat predictions, by modifying the multi-body screening function and the equation of state function. The fitting of the new parameters requires rapid calculations of melting point and latent heat, which are enabled by efficient free-energy methods. The results provide the basis for constructing a cross-potential that will be fitted to the binary gold–silicon phas

Over the past few years, considerable effort has been directed toward the development and improvement of mechanoluminescence (ML)-based stress sensing as an efficient nondestructive inspection technique. One of the challenges in ML stress sensing is the limited luminescent intensity and sensitivity of the ML-epoxy composite film to the local stress field. Herein, we present a novel approach for increasing the sensitivity of ML composites made of an epoxy resin matrix and SrAl₂O<sub>4<