NEW ADVANCEMENT OF NANOMECHANICS-EXISTENCE OF LOWER LIMIT OF APPLICATION OF CLASSIC CONTINUUM MECHANICS IN NANOREGION-

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The present study is to reveal the applicable range of nanomechanics through the classic continuum mechanics and the effect of surface stress on stress singular region in focusing on the stress singular field at a nano region in a three-dimensional joint.1. Strain distribution in the stress singular field of the joint composing of Silicon and resin could be obtained by means of a digital image correlation method. Data were obtained through a digital microscope. The order of singularity of strain singular fields was agreed with the value obtained by eigenanalysis of 3D joint.2. In the present study, singular stress fields in a nanoscaled joint under an external force were investigated using molecular dynamic(MD) method. The atomic stress fields had a singularity even if the size of joint was in nanoscale. Characteristic equation for determining the order of stress singularity was derived using a boundary condition with surface/interface mechanical properties. From the result of the MD analysis, interface mechanical properties were a function of the distance from the edge of interface. Then, the order of stress singularity increased with approaching to the edge of interface. The atomic stress distribution near the edge of interface could be well expressed using the order of stress singularity obtained from the characteristic equation. This indicates the validity and usefulness of nanomechanics at the objective of this project and the results which extend the applicability of continuum mechanics.3. Green's functions for anisotropic-anisotropic materials and isotropic-anisotropic materials were newly derived on the basis of Stroh's formalism and incorporated into the boundary element program. Furthermore, it was shown that the solutions for isotropic-anisotropic materials could be smoothly derived from those for anisotropic-anisotropic materials.