General procedure of failure analysis: DT, selection, preservation, cleaning & sectioning of samples — Lesson 3

This lesson covers the subject of failure analysis and prevention, focusing on the steps involved in the general procedure for analysis. It discusses destructive tests and their limitations, particularly the tensile test. The lesson also explains how to preserve samples of failed components, perform cleaning, and sectioning for further analysis. It highlights the importance of considering the ductility of a material, the role of tensile properties in failure, and the impact of service conditions. The lesson also provides an example of a crankshaft failure due to a minor difference in ductility percentage. It concludes with a detailed explanation of sample selection, preservation, cleaning, and sectioning in failure analysis.

Video Highlights

00:18 - Introduction to the subject of failure analysis and prevention, and the general procedure for analysis.
08:51 - Discussion on the importance of considering the behavior of materials in different directions (anisotropy) in failure analysis.
19:59 - Explanation of the importance of preserving samples from any kind of damage, including chemical, mechanical, and thermal damage.
22:40 - Discussion on the process of sectioning, including the selection of the location for sample collection and the methods of sectioning.
26:59 - Explanation of the potential damages that can occur during sectioning and how to avoid them.

Key Takeaways

- Destructive tests, such as the tensile test, provide valuable information for failure analysis but have certain limitations.
- The ductility of a material, indicated by percentage reduction in cross-sectional area, can be a better indicator of failure than simple percentage elongation.
- Service conditions often play a significant role in component failure, sometimes overriding good tensile properties.
- Sample selection, preservation, cleaning, and sectioning are crucial steps in failure analysis. These steps ensure that the sample remains intact and representative of the failed component for accurate analysis.