Applicability of advanced digital image correlation techniques in integrity assessment codes of safety sensitive industries.

该项目的目的是通过提高对薄壳部件两种失效机制的理解来支持R6评估程序的开发。这些机制是断裂和塑性塌陷。这将增加对快速断裂发生的限制和条件的认识。为了确定测试条件，例如加载，将使用有限元分析（FEA）。这将确保研究稳定和不稳定断裂之间的相关区域。将沿着应力-应变数据表格生成材料的JR曲线。这些数据将确定该项目与核工业的相关性。在此初始阶段之后，将制备厚度在0.5-1 mm之间的样品。此类材料的相关加载条件是压力下的圆柱体。这将在布里斯托大学使用已经建造的双轴试验台进行模拟。可引入代表腐蚀和刺穿的缺陷。在样品中产生缺陷的方法仍在考虑中，可以扩展到研究焊接以及材料本身。数字图像相关（DIC）可以用来找到表面应力场，并输出一个值K，应力强度因子。部分在布里斯托大学开发的方法是新颖的，它涉及使用DIC自主测量位移场，并识别已发生的裂缝。然后，为紧邻裂纹的区域自动生成有限元（FE）网格。被称为相位一致性的技术用于自动分割裂纹，以给出小于一个像素的固有分辨率。将在不同的条件下进行一些测试，包括一系列压力和材料特性。这将有助于理解破坏的方法，例如塑性破坏、快速断裂和混合模式破坏。R6评估方法将在项目开始时使用，用于对薄壳样品进行评估，将培养对该评估方法的技能和理解，并成为项目的有用部分。

The aim of the project is to support the development of the R6 assessment procedure by improving the understanding of two failure mechanisms of thin shell components. These mechanisms are fracture and plastic collapse. It will add to knowledge of limits and conditions for the occurrence of fast fracture. To decide the conditions for testing, for example loading, Finite Element Analysis (FEA) will be used. This will ensure that the relevant region between stable and unstable fracture is investigated. The JR curve of the material will be generated along with a tabulation of stress-strain data. The data will establish relevance for the project to the nuclear industry. After this initial stage samples will be prepared with thickness between 0.5-1 mm. The relevant loading conditions for this type of material is a cylinder under pressure. This will be simulated at the University of Bristol using the biaxial testing rig that has been constructed. Defects to represent corrosion and puncturing can be introduced. The method of creating the defect in the sample is still being considered and could be extended to study a weld as well as the material itself. Digital Image Correlation (DIC) can be used to find surface stress field and output a value of K, the stress intensity factor. The method developed in part at the University of Bristol is novel, it involves autonomously measuring the displacement field using DIC and identifies cracks which have occurred. A Finite Element (FE) mesh is then automatically generated for the area in close proximity to the crack. The technique known as phase congruency is used to automatically segment the crack to give an intrinsic resolution less than a pixel. A number of tests will be performed under different conditions including a range of pressures and material properties. This will enable understanding of methods of failure, for example plastic collapse, fast fracture and mixed mode failure. The R6 assessment method that will be used at the start of the project, to perform an assessment for the thin shell samples, will develop skills and understanding of this assessment method as well as being a useful part of the project.