Wednesday, December 6, 2017

We are carried along by our mentors

Recently I was listened to one of AlejAndro Anastasio’s One Hand Speaks podcasts titled The difference a few kind words can make in a person’s life. He described how his high school art teacher inspired his career in art. That got me thinking about some similar mentoring experiences I had. My first also happened in high school. I had blogged about it in a March 1, 2013 post titled Does your speaking voice sound like a little girl? One of my dad’s old friends, Dr. John F. Kahles, had visited us and after dinner told me a fascinating story about metallurgical engineering. It started me toward majoring in metallurgy at Carnegie-Mellon University. (His memorial tribute is at the National Academy of Engineering).

John told us about selecting materials for the teeth on the bottom of the scoop to a front end loader or bulldozer. Those teeth have to deal with contacting both sand and rocks. Sand is abrasive and will rub and wear away material.

Repeatedly hitting rocks causes cracking (impact fatigue) at the surface, and the cracks can grow inward until a tooth breaks off.  An obvious solution for reducing the abrasive wear rate from the sand would be to make the teeth harder, so they would wear out less rapidly.

But if that’s all that is changed, then you just switch failure modes. The impact fatigue cracks were not a problem before because they grew so slowly that they just were worn away. When you just increase the hardness, the cracks can grow faster until the teeth now can break off rather than wear out. So, before you can raise the hardness, you need to think about how to change the impact fatigue behavior. 

Another experience happened when I was a junior, and finally got to choose a metallurgy course as an elective. Our class advisor, professor Robert Dunlap, told Bob McIntyre and I to take a big leap and enroll in the graduate course on Alloy Steels. It was taught by the department head, Harold W. Paxton, using  E. C. Bain and H. W. Paxton’s book, Alloying Elements in Steel. Professor Dunlap said that a lot of the course will probably go right over your heads, but it might be the only chance you get to learn that topic from a true master. I struggled to get a B, but was fascinated. Six years later I got a job doing applied research on alloy steels at the Climax Molybdenum Company lab in Ann Arbor, Michigan.     

Much later I got to be the mentor. On April 28, 2009 I blogged about the Joy of teaching college students – talking about corrosion and materials selection in a guest lecture at Boise State University.

Ernst Nowak’s painting of a piggyback ride, and a photo of a front end loader both came from Wikimedia Commons.

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