발간논문

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Vol.34, No.11, 1436 ~ 1441, 1996
Title
A Numerical Investigation of Elastic and Plastic Properties in Nanocrystalline Materials
김형섭 Hyoung Seop Kim , 홍순직 Soon Jik Hong
Abstract
In order to investigate the effect of grain size on the overall elastic and plastic properties of nanocrystalline materials in which the grain size ranges typically from a few nanometers to a few tens of nanometers, the elasto-plastic finite element method was used. The tensile deformation behaviors of the unit cell composite materials composed of crystalline of various sizes and grain boundary region of 1 nm width have been analyzed. The grain boundary region had a lower elastic modulus and a higher yield strength than the crystalline and the materials were assumed to be elastic-perfect-plastic because of the small grain size. According to the calculated results, a drop in the grain size from 100 nm to 2 nm increased the yield stress and decreased the elastic modulus. The yield stress-(grain size) -1/2 shape is S curve which fitted well with the mixture rule based on the volume fraction. Therefore, the exponent of Hall-Petch equation can be - 1 or -1/2, and the gradient of the curve can undergo a change according to the range of the grain size.
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