土体双屈服面模型的塑性功方程

根据双屈服面模型的概念,塑性应变增量可以看成是2个分部塑性应变增量的合成.作者通过研究,指出塑性功也可以看成是有效应力分别在2个分部塑性应变增量上进行的塑性功分量的合成;使用热力学方法,将每个塑性功分量都转化为自由能增量和耗散能2个部分,因此双屈服面模型的塑性功方程由4个能量分量组成,通过合理确定或假定用分部塑性应变增量表示的塑性功方程就可以得到双屈服面模型的屈服面方程.以改进的椭圆-抛物双屈服面模型为例,认为塑性功方程由体积硬化引起的自由能增量和耗散能以及剪切硬化引起的自由能增量和耗散能4个能量分量组成,从2个屈服面方程推导了用分部塑性应变增量表示的塑性功方程,对塑性功方程反映的能量转化关系进行了分析,将自由能释放解释为剪胀时的能量来源,并从该塑性功方程推导出双屈服面模型的2个屈服面方程.

Plastic work equation of double-yield-surface model for soils

On the basis of the concept of double-yield-surface model, plastic strain increment could be seen as the combination of two plastic strain increment components. It is pointed out that the plastic work could be regarded as the sum of the plastic work components done by effective stress on the two plastic strain increment components respectively. The plastic work components both transform into free energy increments and dissipated energy in accordance with thermomechanics. Therefore the plastic work equation of double-yield-surface model is composed of four energy components. Yield functions of double-yield-surface model could be deduced through a reasonable plastic work equation denoted by plastic strain increment components. As for the improved elliptic-parabolic double-yield-surface model, the plastic work equation is composed of free energy increment and dissipative energy caused by volume hardening and shear hardening respectively. The plastic work equation of the model is deduced from the two yield functions; and then the plastic work equation is analysed, in which the release of free energy is interpreted as the energy source in the case of dilation. Finally the two yield functions of the model are deduced from the plastic work equation.