Johnson & Ettinger模型和Volasoil模型在污染物室内挥发风险评价中的应用和比较

在土壤污染和地下水污染的现场,挥发过程是挥发性污染物暴露的重要途径.设置典型土壤污染场景作为研究对象,选取Johnson&Ettinger模型和Volasoil模型进行室内挥发过程的模拟和暴露浓度的计算.对两个模型中污染物的运移机理进行了比较和分析.尽管方法和参数选择有所不同,二者对污染源处三相平衡浓度的计算本质上是一致的.暴露浓度的计算结果表明,两个模型对室内挥发过程的模拟可能会有较大差异,与污染现场的具体情况有关.参数影响的分析表明,污染源顶部埋深对二者暴露浓度的影响一致,Johnson&Ettinger模型对污染土壤含水率的大小非常敏感.建议考虑房屋结构的实际情况,选用或者改进模型进行室内挥发过程的评价.     

Numerical modelling of electrohydraulic free-forming and die-forming of DP590 steel

Electrohydraulic forming (EHF) is a high energy rate forming process in which the strain rate in the sheet metal can vary from 5 × 10² to 10⁵ s⁻¹ depending on various factors. Several mechanisms have been reported to cause an improvement in formability in EHF such as material deformation mechanisms, inertial effects and the dynamic impact of the sheet against the die. EHF is a complex high speed forming process and experimental work alone is not sufficient to properly understand this process. To understand the variation of some influential variables in EHF, electrohydraulic die-forming (EHDF) and free-forming (EHFF) of DP590 dual phase steel were simulated in ABAQUS/Explicit by considering the fluid/structure interactions. Three-dimensional finite element simulations were conducted by modelling the water with Eulerian elements with a view to investigating the effect of released energy on the sheet deformation profile history, strain distribution, loading path and damage accumulation type. The Johnson–Cook constitutive material model was used to predict the sheet behaviour and the parameters in this model were calibrated based on experimental test results available for DP590 at various strain rates. The Johnson–Cook phenomenological damage model was also used to predict the ductile failure (damage accumulation) in both EHDF and EHFF. Predicted final strain values and damage accumulation type showed good agreement with the experimental observations.