Before we move on, let’s be clear: Doubt being the essence of critical thinking does not mean paralysis. At some point the thinker makes a choice to move forward. 

A related topic is critical thinking. Over the years, I have come to define critical thinking as the ability to confirm that the proper context has been defined. In more technical language, critical thinking is the process of selecting the most appropriate and useful boundary conditions.

In engineering school, we have laboratory classes so that we can also learn from our own experience. Is the iron crystal structure really cubic? We might be given a chance to perform X-ray diffraction in a lab and be required to work out the angles between the planes of the crystal from the dot patterns on an X-ray detector.

For those of us who would like to gain high-level competence in any profession, it’s helpful – at the least, and perhaps critical – to explore many of the branches of the tree of knowledge.

Finally, the technician may examine the fracture surfaces to determine the “% shear.” Shear technically implies ductility at both macro and micro scales, although the test method does not require anything more than a visual check using the eyeballs.

One of most important technical issues that a fracture analyst must deal with is evaluating whether the crack was ductile or brittle. Here we are talking about visible characteristics revealed to the human eye, and we are strictly discussing structures with features that are readily viewed with the human eye.

When I teach people how to do visual examinations as part of the original stage of a failure investigation, I remind them of a very basic group of things that are truly facts.

From last time, what is the fact there? We no longer have a simple fact that is a simple carbon content read off a simple list of elemental concentration values. We have results from a sequence of tests that were determined to be suspicious by the chemist who was performing the work.

What is a fact? Since people generally come to failure analysts when they can’t figure things out for themselves, I have come to believe that it is important to not only have reliable facts but to be able to explain to people why our facts are indeed reliable!

The indigenous inhabitants of what is now called Northern Michigan used the metallic copper they found at or near the earth’s surface for at least 6,000 years to make tools and ornaments. There was no need for what we today call mining, with its implications of underground digging, explosives and other modern technological innovations.