Since we started this series of posts, we have been focused on providing information on how we can learn to better see what is out there so that we can understand the interactions between different aspects of reality. People say that “seeing is believing,” but if you have been following this blog for a while, you will understand that our eyes can fool us. Having our eyes fool us is only the tiniest part of what causes us to make mistakes that lead to failures. The bigger issue is whether we know how to give each thing that comes into our field of view (hearing, taste, emotional field, etc.) the proper amount of importance. I think it would be impossible to overstate the significance of this issue in general, especially so when trying to understand a failure.
Some time ago, a client brought some small parts that had been found by their customer (prior to assembly in final products) to have objectionable discontinuities. Some of the discontinuities were clearly cracks. Some looked like surface scratches or tool marks. Since the parts were supposed to contain pressure, there was probably a legitimate concern about the discontinuities that were actually cracks.
I looked at about a half dozen parts. The discontinuities were found at every location along the length of the part. Some were near End A and others were in the middle. Some were near End B. Some were in straight portions of the component, while others were at bends. It became clear to me that it was most likely that the discontinuities were present in the raw material. If the discontinuities were being introduced by the part manufacturer, then there would be more discontinuities where the manufacturing stresses were higher. This was clearly not the case. (To protect the innocent, I have not given all the details that would allow you to conclude that I am right or wrong about this particular case. It is given as an example only!)
Sometime later, I was given the supplier’s findings to review. The supplier talked about the cracks and the cause of the cracks being due to hydrogen embrittlement. They had nice photos and showed the brittle microscale features of the crack surfaces. They did metallographic cross sections and showed how the cracks were propagating with respect to the microstructure. There was nothing wrong with the work that they did, but they missed the point entirely, if their point was a “corrective action” to avoid recurrence.
Why? Because knowing all about the brittle crack and trying to totally prevent the parts from ever getting wet so that no hydrogen will be diffused into the metal is not very practical. The parts are exposed to multiple types of fluids in the manufacturing process. I suppose that it is possible that someone could come up with the idea of a thermal stress relief to minimize the stresses that have to be present to allow the hydrogen to become a problem. But that idea is unlikely to go far in a commodity product that has never required heat treating in the past.
In order to solve the real problem, we have to be able to see the real problem. We have to be able to sit back and look at the big picture. We have to be sure we don’t get lost in the forest because we are paying too much attention to the trees. The problem with the failure-analysis forest is that it is populated with so many different kinds of trees, many of which don’t even look like trees.
So, how do we become someone who is able to see the big picture? Either you are born with the ability, which I was not, or you learn to see a bigger and bigger picture. It’s not so much just moving your eyeballs around, although that is a useful first step. It is very clearly associated with learning to see connections between little facts that other people miss. This comes from practice at seeing connections between things that don’t at first appear connected. Maybe most people would rather just go to the expert who can see those connections for a type of situation they deal with once in a while. But these same connection circuits can be used to deal with everyday aspects of life.
We';; continue our thought-provoking discussion next time.