Papers by Keyword: Strain Gradient Elasticity

Abstract: Cyclic delamination experiments with multilayered structures were performed in four point bending mode using a central notch for crack initiation. In a preceding study, the propagation of the delaminating cracks could be interpreted on the basis of the Paris law. In order to obtain more insight into the mechanisms of fatigue and crack propagation, FEM simulations of the experiments were conducted. The material models used in the simulation involve strain gradient elasticity, kinematic hardening plasticity and creep. Following the concept of damage mechanics, the crack propagation rate of delamination was related to the inelastic strain accumulated per loading cycle. Thereby, singularities of stresses and strain at the crack tip were suppressed by the regularizing effect of strain gradient elasticity.

Abstract: The aim of the paper is quantify the material length scale parameter of the simplified form of the strain gradient elasticity theory (SGET) using first principles density-functional theory (DFT). The single material length scale parameter l is extracted from phonon-dispersions generated by DFT calculations and, for comparison, by adjusting the analytical SGET solution for the displacement field near the screw dislocation with the DFT calculations of this field. The obtained results are further used in the SGET modeling of cracked nanopanel formed by the single tungsten crystal where due to size effects and nonlocal material point interactions the classical fracture mechanics breaks down.

Abstract: The paper investigates the limits of applicability of the critical energy release rate for predicting the growth of a crack in nanoscale materials applying the strain gradient elasticity theory (SGET) capable to capture size effects, nonlocal material point interactions and surface effects in the form of (phenomenological) higher-order stress/strain gradients.

Abstract: The goal of the contribution is to develop an asymptotic interface crack-tip solution under conditions of plane strain for a bi-material that obeys a special form of linear isotropic gradient elasticity. Several fracture mechanics problems have been solved in the past within the framework of strain gradient elasticity which is capable to capture additional length/size parameters. However to our best knowledge no solution concerning an interface crack is available in the literature.

Abstract: In this paper, a strain gradient model is constructed to predict the bending size dependence of the elastic property of nanofibers under three-point tests. The model prediction shows that there are two kinds of size dependency for the bending tests: one is related to the diameter of the nanofiber, which can be named as Diameter Size Dependency (D-SD), the other is related to the length of the nanofiber, which can be termed as Length Size Dependency (L-SD). Mechanical testing on PCL nanofibers was performed to verify the model for D-SD, and good agreement is found between the model prediction and the data obtained in the experiment. The model can be applied to explain the size dependency in bending test for polymeric nanofibers.

Abstract: Structures are assemblies of planar and three-dimensional objects. Planar components and parts are commonly because the deformation behaviors of plates and beams can be analyzed within the plane problem framework. For micron-scale structures, patterning processes in microfabrications are intrinsically planar and the resulting fabricated structures are also planar. These planar micron-scale structures have been designed and analyzed using conventional mechanics, but increasingly as the sizes of these structures become smaller, higher order effects become significant. In nanometer-scale, surfaces were recognized to play significant roles in affecting the physical behavior. Size dependent elastic and plastic deformation behaviors in micron-scale structures were also observed. Size dependence is an intrinsic part of higher order theory of mechanics and has been used successfully to explain scale dependent behavior in threedimensional structures. In this paper, two-dimensional higher order elastic relations in plane stress and plane strain for compressible solids are developed. The difference between the higher order and conventional elasticity theories is compared