Kim K, Graham S, Pierron O N
George Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, USA.
Rev Sci Instrum. 2017 Mar;88(3):036102. doi: 10.1063/1.4977473.
We introduce an external-load-assisted thin film channel crack growth technique to measure the subcritical crack growth properties of thin films (i.e., crack velocity, v, versus the strain energy release rate, G), and demonstrate it using 250-nm-thick SiN films on poly(ethylene terephthalate) substrates. The main particularity of this technique is that it requires a polymer substrate to allow loading to large strains (in order to induce channel cracking) without substrate fracture. Its main advantages are to provide a full v-G curve with a single specimen while relying on a simple specimen preparation and straightforward crack growth characterization. Importantly, the technique can be employed for a much larger range of thin films compared to the residual-stress-driven, thin film channel crack growth tests, including ultrathin films and thin film with residual compressive stresses. The restrictions to a proper use of this technique, related to the (visco)plastic deformation of the substrate, are discussed.
我们引入了一种外部负载辅助的薄膜通道裂纹扩展技术，以测量薄膜的亚临界裂纹扩展特性（即裂纹速度v与应变能释放率G的关系），并在聚对苯二甲酸乙二酯基板上的250纳米厚的氮化硅薄膜上进行了演示。该技术的主要特点是，它需要一个聚合物基板，以便在不使基板断裂的情况下加载到较大应变（以引发通道开裂）。其主要优点是，在依赖简单的样品制备和直接的裂纹扩展表征的同时，用单个样品就能提供完整的v-G曲线。重要的是，与残余应力驱动的薄膜通道裂纹扩展测试相比，该技术可用于范围更广的薄膜，包括超薄膜和具有残余压应力的薄膜。文中讨论了与基板（粘）塑性变形相关的正确使用该技术的限制。
