基于上下负荷面的弹黏塑性本构模型及应力积分算法实现

An elasto-viscoplastic constitutive model and its stress integration algorithm based on super-subloading yield surface

为了描述天然软土的时间相依以及结构性特征,提出了一种能考虑土体超固结和结构性的实用弹黏塑性本构模型。它以Asaoka和Hashiguchi的上下负荷面作为某一应变速率下的参考屈服面,按照相对过应力的基本思路,新引入了两个能通过不同应变速率三轴压缩试验测定的率敏性参数c_0和m',建立了以当前应力、黏塑性应变以及黏塑性应变速率为状态变量的动屈服准则函数,并给出了基于Newton-Raphson迭代的应力积分算法,且成功地将其嵌入到大型有限元软件ABAQUS中。最终通过数值算例来验证模型的正确性以及应力积分算法的可靠性。结果表明:该模型能同时描述土体的率敏性、蠕变以及结构性特征,模型参数物理意义明确、易懂可测,预测结果与试验数据吻合良好,可用于复杂边值问题的有限元计算。

To describe the time-dependent, over-consolidated and structural characteristics of natural soft clay, a simple elasto-viscoplastic constitutive model including the influence of structural behavior of clay is proposed. In the new model, the Asaoka＇s superloading and Hashiguchi＇s subloading yield surface is used as a reference yield surface at a specified strain rate. A relative overstress relation is used to obtain the dynamic loading surface at any strain rate based on the reference yield surface. A dynamic equilibrium condition, using the current stress, viscoplastic strain and viscoplastic strain rate as state variables, is adopted as a convergence criterion. Two material parameters c_0 and m＇ about the rate sensitivity are added into the new model, which can be determined by triaxial compression tests with different strain rates. The new model has been implemented into ABAQUS by a stress integration algorithm using Newton-Raphson iteration. The validity of the model and the reliability of the stress integration algorithm are verified by numerical calculation. The numerical results show that the model can describe the time-dependent behavior of clay such as rate sensitivity, structural characteristics and creep. The material parameters are easy to understand and measure with clear physical meaning. Furthermore, the prediction results of the model are in good agreement with experimental data. The model can be used in a finite element calculation under the complex boundary value problem.