727 変位の 2 次勾配を考慮したひずみ勾配理論による軸対称圧子押込みの弾塑性解析

Abstract

Dislocation theory suggests that the plastic flow strength of solid depends on strain gradients in addition to strains. Recent nanoindentation tests at scales on the order of one micron have shown that measured hardness increases significantly with decreasing indent depth. It may be due to the collective mechanical behavior of dislocations which can be represented by the strain gradient effect. In this report, we suggest the simple finite element scheme including second gradient of displacement and investigate the effects of stretch and rotation gradients to hardness.