For those of you who have been following along with this blog recently, or the magazine, you have seen my previous writings about how to recognize fatigue cracks when they do not have obvious beach marks. This time we will start with a couple of images where the classical fatigue features known as beach marks are very obvious.

Detailed inspection of the upper portion of the crack (Figure 2, rotated to an orientation about halfway between the left and right views of Figure 1) revealed a ridge pattern with finer steps merging to coarser ones from bottom to top (equivalent to left to right on Figure 1).

Tooling failure analysis can be very challenging. Frequently, we have to deal with complex loading and multiple simultaneous damage processes.

Tooling failure analysis can be very challenging. Frequently, we have to deal with complex loading and multiple simultaneous damage processes. Because the tools are so hard, fracture surface features are often very faint.

The purpose of science is to reveal how the physical world works. The human world, including psychology and other social sciences, is part of the physical world. The human experience of consciousness, including our ability to experience aspects of the physical world through our sensory apparatus, is part of science.

This is the second part of Debbie Aliya’s blog “Why did the part fail?”

Speaking with greater clarity, why did the subject of the investigation deform or break? Why did some of its material disappear? Why have the strength characteristics become degraded?

As I plug away at writing the materials-engineering-informed failure-analysis book that has been on and off my “Get it Done!” list since 2003, I have at last come to the part about writing the report.

Failure is a loaded word. It implies fault. But the type of failure analysis engineers usually work on is of things.

So, why did it fail? If the failure is due to mechanical causes, including fracture, wear and deformation, a true answer is always “because the stress exceeded the strength.”