General procedure of failure analysis: Macroscopy of fracture surfaces-III — Lesson 1

This lesson covers the general procedure of failure analysis, focusing on the macroscopy of fracture surfaces. It discusses the process of failure analysis, including the collection of background information, preliminary examination, non-destructive testing, and destructive testing of the failed component. The lesson also explains the importance of macroscopy in identifying the location and direction of failure, the type of loading conditions, and the stress state during failure. It further delves into the features that help identify whether the failure is ductile or brittle, the presence of beach marks, and the stages of fatigue fracture. The lesson also discusses the impact of high temperature on failure, the formation of circumferential cracks, and the significance of chevron marks and radial marks on the fracture surface.

Video Highlights

0:19 - Introduction to the general procedure of failure analysis, including collection of background information, preliminary examination, non-destructive testing, destructive testing, and selection preservation and cleaning sectioning of samples.
03:14 - Detailed explanation of the three stages of fatigue fracture: crack nucleation, steady growth of crack, and sudden fracture.
09:36 - Discussion on the effects of high temperature exposure on the fracture surfaces, including the formation of concentric circles or beach marks.
19:37 - Explanation of the effects of internal pressure and high temperature on the fracture of components, leading to the formation of I shape fractures.
29:22 - Discussion on the identification of the direction of crack growth and initiation site through chevron marks and radial marks.

Key Takeaways

- Failure analysis involves a systematic approach to understand the cause of failure in a component.
- Macroscopy of fracture surfaces provides valuable information about the failure, including its location, direction, and the type of loading conditions.
- Beach marks on a failed component indicate the second stage of fatigue fracture.
- High temperature can lead to different types of failures, including stress rupture and thinning of the component.
- Chevron marks and radial marks on the fracture surface provide insights into the direction of crack growth and the initiation site of the failure.