多重线性软化材料的拉伸应变局部化及力学行为分析

峰后线性应变软化本构关系的拉伸局部化带内部的塑性应变分布及试样的峰后应力—应变关系的理论解答不适用于复杂情形,在双线性应变软化条件下,得到了拉伸局部化带内部的塑性拉伸应变分布及试样的峰后应力—应变关系的理论表达式,又将其推广为多重线性应变软化情形,这在一定程度上拓展了考虑峰后应变局部化的单向拉伸试样力学行为模型的适用范围。拓展后的模型具有广泛的适用性,可模拟峰后的Ⅰ类及Ⅱ类(回跳)行为。通过选择适当的塑性模量(依赖于应力水平)与拉伸局部化带宽度的比值,本文的模型可以精确地模拟多种准脆性材料(例如岩石及混凝土)在单向拉伸条件下的复杂的峰后力学行为。

Analysis of Strain Localization and Stress-strain Curve of Multi-linear Strain-softening Materials in Uniaxial Tension

The analytical solutions of the plastic strain distribution in the tensile strain localization zone and the post-peak stress-strain relation of a straight bar in uniaxial tension,undergoing the linear strain-soft- ening behavior in the post-peak range,are not applicable to complex cases.In the paper,the analytical so- lutions are derived for bilinear strain-softening materials in the post-peak range.And these analytical solu- tions are also extended to the case of muhi-linear strain-softening.The applicability of the modified model considering strain localization in the post-peak range is wide.The model can model ClassⅠbehavior and ClassⅡbehavior(snap-back)in the post-peak range.If a proper value for the ratio of the plastic modulus (dependent on tensile stress level)to the thickness of the tensile strain localization zone is selected,then the complex mechanical behavior in the post-peak range of quasi-brittle materials in uniaxial tension,such as rock and concrete,can be accurately modeled by the present model.