塑性梯度体元及应变局部化启动机制分析

Study of plasticity gradient volume element and start-up mechanism of strain localization

利用代表性体元可较好地反映出并非理想连续均匀的岩土介质破坏前强度和变形行为。但当材料出现高的应变梯度(应变局部化)时,在体元上的应力、应变呈现高次非线性变化,代表性体元不能如实地反映出介质的力学性能。提出一种可包含局部化变形的研究基元——塑性梯度体元(Plasticity Gradient Volume Element),塑性应变在其内可用微分形式表达。该体元不但可反映介质的平均力学响应,而且可反映应变呈高次非线性变化时的影响。随着硬(软)化模量从正值变为负值,变形模式将由均匀变形模式变为局部化变形模式,这就是应变局部化的启动机制。

The behaviors of geomaterials before destroy can be reflected by the representative volume element;but when the high strain gradient occurs（such as the strain localization occurs）,the representative volume element in which the strain and stress ate nonlinear,cannot reflect the mechanical character of geomaterials entirely.A plasticity gradient volume element（PGVE） which can describe the local deformation is proposed.The start-up mechanism of strain localization is analyzed;when the hardening modulus（or softening modulus） changes from positive to negative,the deformation pattern will change from uniform pattern to localization pattern.