research

We formulate a geometric theory of nonlinear morphoelastic shells that can model the time evolution of residual stresses induced by bulk growth. We consider a thin body and idealize it by a representative orientable surface. In this geometric theory, bulk growth is modeled using an evolving referential configuration for the shell (material manifold). We consider the evolution of both the first and second fundamental forms in the material manifold by considering them as dynamical variables in the variational problem.

Since real specimens deform three-dimensionally, 2D modeling approaches cannot predict the flow curve of the material precisely. The predicted flow curves obtained from 2D modeling can, however, be correlated to the 3D ones by introducing a correlation factor, We quantified by the stress ratio (σ_3D/σ_2D) based on the 2D and 3D RVE calculations for DP600 steels with various martensite phase fractions (V_m=0–50%) at different equivalent plastic strains varying from ε^p_eq=0 to 0.1.

Recent literature suggests that nano-twinned materials posses both high strength and ductility. Such unusual properties have been attributed to the unique ability of coherent twin boundaries in affecting dislocation slip transfer mechanisms unlike other types of grain boundaries of lesser symmetry. A combination of experimental and theoretical studies is presented to rationalize the macroscale attributes of nano-twinned NiCo alloys of four different compositions (please see the attached pdf below for the paper). 

A new perspective on model reduction for nonlinear multi-scale analysis of heterogeneous materials. In this work, we seek meaningful low-dimensional structures hidden in high-dimensional multi-scale data.

Recently, unusually high detachment rates of a myosin from actin were reported with a force spectroscopy technique. Here, we show that these high rates may be due to the coupling between bond breaking and state transition. Based on a kinetic model for single myosin, rates of bond breaking between myosin and actin at different nucleotide states are systematically extracted for the first time. Our results clearly indicate that myosins may adopt much higher transition rates than bond breaking rates at different nucleotide states at relatively low forces.

The presence of nano-sized coherent precipitates is well known to have crucial impact on the mechanical behaviors of a broad class of shape memory alloys. The local stress gradient at the matrix-precipitate interface is predicted as induced by inter-lattice atomic disregistry. Due to the presence of the local disturbance fields, the preference for activating different martensitic variants, given the uni-directionality thereof, is influenced substantially.