纳晶材料剪切带的演化机制与模型

项目名称： 纳晶材料剪切带的演化机制与模型

项目编号： No.10872087

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 生物科学

项目作者： 周剑秋

作者单位： 南京工业大学

项目金额： 38万元

中文摘要： 本项目采用实验、理论和数值模拟研究结合为一体的方式系统研究纳晶材料剪切带的演化行为。在实验方面：分别选择从商业公司购买的高致密度电沉积方法制备的纳晶镍片和利用等离子蒸发结合热压烧结制备的含孔隙纳晶镍块体作为拉伸和压缩试样，测试了这两种试样在准静态下拉伸和压缩力学性能。在理论方面：在全面理解其小塑性均匀和大塑性非均匀变形行为的基础上，完整地构建了纳晶金属小塑性均匀变形 （剪切带形式）和局部非均匀大塑性变形的理论模型，讨论了纳晶材料断裂失效模式及剪切带演化发展的影响因素，并建立了相应的断裂失效模型. 在数值模拟方面：在建立基于纳米晶粒晶界层次的有限元模型的基础上，模拟研究剪切带的演化情况，量化分析晶粒尺寸分布、晶粒转动与各相异性等对剪切带演化的影响，全面揭示纳晶材料剪切带的演化机制.在以上基础上提出将纳晶材料剪切带的演化过程分为启动、发展和失稳三个阶段。 这一系列工作不仅具有十分重要的科学理论价值，而且为寻求定量设计既有高强度又具备高延性的纳晶材料奠定了很好的理论基础，有助于推动纳晶材料的进一步研发并克服纳晶材料的工程应用障碍。

中文关键词： 纳米晶体； 力学行为； 塑性变形机理； 本构模型； 剪切带

英文摘要： By adopting the experimental, theoretical and numerical methods, this project has studied the evolution behavior of the share band in nanocrystalline (NC) materials. In the aspect of experiments: full dense, commercially available NC electrodeposited Ni sheets and porous, bulk NC Ni prepared by plasma evaporation method combined with hot pressure sintering were treated as tensile and compressive samples respectively. First, tensile and compressive mechanical properties of the two sorts of NC sample were tested respectively under quasi-static strain rates at room temperature. In the aspect of theory: based on deformation behaviors of the tensile and compressive samples at small plastic and large plastic stages, theoretic models of homogenous deformation at small plastic stage and non-homogenous deformation (in the form of shear bands) at large plastic deformation were established completely. Finally, the failure mode of NC sample and the factors affecting the shear bands development were discussed in detail. In the aspect of numerical simulation: On the basis of the finite element model of the nanocrystalline at the level of grain and grain boundary, we simulated the evolution of the shear band in NC materials. In addition, the effects of grain size distribution and grain rotation on the evolution of shear bands were quntitatively analyzed, and the mechanism of shear bands evolution in nanocrystalline materials was fully revealed. Based the above results，we proposed that the evolution of shear bands were divided into three stages：initiation,development and instability. Obviously, a series of programs in this project not only presents very important scientific value, but also provides a solid theoretical foundation for designing ideal NC materials with high strength and good ductility. These constitutive models and relative deductions will impulse the development of mechanical theory and engineering application of NC materials.

英文关键词： Nanocrystalline; Mechanical behaviors; Plastic deformation mechanisms; Constitutive modeling;shear bands