General procedure of failure analysis: Macroscopy of fracture surfaces-II — Lesson 5

This lesson covers the general procedure of failure analysis, focusing on the use of Factography in determining environmental and loading conditions under which a component's fracture has occurred. It discusses how Factography helps rule out possibilities such as overloading, material properties, and the role of discontinuities in fracture. The lesson also explains specific features observed on the fracture surface, which are used to make useful inferences about the fracture. For instance, it elaborates on how the stress state under which the fracture has occurred, the crack initiation site, and the direction of crack growth can be determined. The lesson further delves into the identification of stress conditions, fracture initiation sites, and the interpretation of fracture surfaces.

Video Highlights

01:31 - Explanation of how to gather information from various features present on the fracture surface.
05:56 - Discussion on the extent of particular operational mechanism leading to the fracture.
07:38 - Explanation of the difference between plane strain conditions and plane stress conditions.
15:17 - Discussion on how to identify the fracture initiation site.
21:54 - Explanation of how the fracture surface orientation can indicate whether the fracture is ductile or brittle.
26:25 - Explanation of how to identify the type of fracture based on the fracture surface.

Key Takeaways

- Factography is a crucial tool in failure analysis, helping determine the conditions under which a component's fracture has occurred.
- The stress state under which a fracture has occurred can be determined by observing the fracture surface.
- The crack initiation site can be identified through unique features on the fracture surface.
- The direction of crack growth can be determined using features such as chevron marks and crack arrest lines.
- The interpretation of fracture surfaces can provide information about the stress conditions under which failure has occurred and whether the failure is ductile or brittle.