General procedure of failure analysis: Determination of type of fracture I — Lesson 5

This lesson covers the fundamental aspects of failure analysis and prevention. It delves into the general procedure of failure analysis, focusing on how to determine the type of fracture. The lesson discusses the role of non-destructive testing in identifying discontinuities, the importance of destructive testing in evaluating mechanical properties, and the significance of macroscopic and microscopic analysis in understanding the origin and direction of crack growth. It also highlights the role of metallography in determining the phase and grain structure of the failed component. For instance, if a material has high strength but low ductility and toughness, it will tend to fail in a brittle manner. The lesson also explains the different types of fractures such as fatigue fracture, tensile brittle fracture, and ductile fracture.

Video Highlights

01:16 - Description of non-destructive testing used for determining discontinuities.
05:14 - Explanation of the origin and direction of crack growth.
09:51 - Explanation of the formation of voids and their role in ductile fracture.
19:10 - Explanation of the different types of fractures based on crack propagation.
31:27 - Discussion on the evolution of failure in a tensile test.

Key Takeaways

- Understanding the sources of failure and the general procedure of failure analysis is crucial in preventing future failures.
- Non-destructive testing helps in identifying discontinuities, whether they are present at the surface or within the component.
- Destructive testing is important in evaluating mechanical properties such as hardness, toughness, and tensile strength.
- Macroscopic and microscopic analysis help in understanding the origin and direction of crack growth.
- Metallography plays a crucial role in determining the phase and grain structure of the failed component.
- The type of fracture (fatigue, tensile brittle, or ductile) can be determined by analyzing the mechanical properties and the conditions under which the failure occurred.