Constitutive modeling of indentation cracking in fused silica
Constitutive modeling of indentation cracking in fused silica
复制标题
DOI：
10.1111/jace.14734
复制
发表时间：
2017-05-01
影响因子：
3.9
通讯作者：
Durst, Karsten
中科院分区：
文献类型：
--
作者：
Bruns, Sebastian;Johanns, Kurt E.;Durst, Karsten
熔融石英在纳米压痕过程中表现出三种不同的机制，即塑性变形、非弹性致密化和开裂。凝聚区有限元法被用来研究这些制度不同的压头几何形状。在三维模型中，通过引入沿沿着垂直于压痕表面的压头边缘对齐的粘性单元平面来考虑中值/径向裂纹。除了比较压痕开裂数据与实验数据，致密化的压痕裂纹扩展的作用是严格审查使用压力独立冯米塞斯和压力依赖Drucker-Prager帽本构模型。结果表明，Drucker-Prager帽模型提供了一个准确的描述所有检查压头的几何形状的弹塑性变形条件。材料致密化导致较短的裂纹长度，因此Lawn等人的方法（J Am Ceram Soc，1980;63：574-581）导致较大的基于压痕的断裂韧性值。一旦裂纹开始，其扩展与钝头压头几何形状（Berkovich）相当，而致密化导致更尖锐压头几何形状的裂纹扩展较慢。
Fused silica shows three distinct regimes during nanoindentation, that is, plastic deformation, inelastic densification, and cracking. Cohesive zone FEM is used to study these regimes for different indenter geometries. In a three-dimensional model, the median/radial cracking is considered by introducing cohesive element planes that are aligned along the indenter edges perpendicular to the indented surface. In addition to comparing indentation cracking data with experimental data, the role of densification on indentation crack growth is critically examined using a pressure independent von Mises and a pressure dependent Drucker-Prager Cap constitutive model. The results show that the Drucker-Prager Cap model delivers an accurate description of the elastic-plastic deformation conditions for all examined indenter geometries. Material densification leads to shorter crack lengths and thus the approach by Lawn et al. (J Am Ceram Soc, 1980;63:574-581) results in larger indentation-based fracture toughness values. Once the crack was initiated its propagation is comparable for blunt indenter geometries (Berkovich), while densification leads to a slower crack propagation for sharper indenter geometries.