Duane Miller is the Manager of Engineering Services for the Lincoln Electric Company, but he is probably better known as the "Nation's Leading Authority on Structural Welding". The titled of his speech is a reference to the 40 years he has spent working at Lincoln Electric. During that time, he worked as the protege to the formal Leading Authority on Structural Welding, the late Omer Blodgett. Mr. Blodgett passed down his wealth of structural welding knowledge to Mr. Miller in a mentoring relationship that harkens the book The Giver by Lois Lowry. In this keynote speech, Mr. Miller shared 5 technical lessons and 5 personal lessons.
1. Welding gives you so much freedom that you can make poor connections. I.e., just because you can make a weld in a certain way, doesn't mean you should. Load always wants to go into the member parallel to the load, so arrange your members and welds to provide a direct path into parallel members.
2. When welds are well specified, welds are cost effective. Both material (i.e. volume of weld) and labor contribute to the cost of a weld. Designing welds that minimize the size of the weld (and thus the number of passes the welder needs to make) will decrease the cost of the weld. One example of this is using a double bevel groove weld (triangular weld from each side of a member) to connect thick members instead of a single bevel weld (triangular weld from one side of a member).
3. Notches and constraint are the key contributors to structural failure. While using tougher welding material, will improve the strength of a weld, this effect is far outweighed by the geometry of the weld. Notches, such as the unfused region adjacent to a partial-joint-penetration weld or the sharp crack behind a backing bar that is left in place cause stress concentrations at the root of the weld that make it vulnerable to fracture. When thick/wide materials connected by welds are subjected to tension in the longitudinal direction (perpendicular to the weld), the material tends to want to contract in the thickness/width directions due to the Poisson effect. The thicker/wider the material, the more the surrounding material prevents that contraction, causing a biaxial or triaxial stress state, which increasing the tendency to fracture. Engineers should be highly cognizant of notches and constraint in their weld designs.
4. Shear stresses are essential for ductility. Although we typically speak about the normal yield stress as the indicator of yield, it is technically shear stress that dictates whether a material will yield. If a material experiences hydrostatic pressure (equal stresses in all directions), no shear stresses will occur and the material will never yield. It will remain elastic until it eventually fractures. As the difference between the principle stresses grows, the shear stress experienced grows, eventually reaching a critical stress state that causes yielding. Mr. Miller illustrated this through a series of Mohr's Circles. For anyone whose taken my CE 121 course, you should know how much this point warmed my heart.
5. The role of carbon and alloys are key to understanding welding thermal cycles. Low carbon steel (including A992, which is a common structural steel) is more ductile when heated and quenched that high carbon steal. This is relevant for the heat affected zone that surrounds weld.
6. Leadership is causing people to do something they wouldn't have done without you. A leader must know where to lead people, how to get there, and how to influence people.
7. Elements of persuasion include Ethos (credibility of speaker), Logos (the message), and Pathos (emotional appeal).
8. Mr. Miller discussed the joy of mentoring for both the mentor and mentee. He encouraged people to seek out mentors and to be open to mentoring others. He advised mentees to ask their mentor questions, but not to question their mentor. He benefitted richly from his relationship with his mentor. From my own experience as both a mentee and a mentor, I highly echo his comments. A mentor is essential to help you see your full potential and navigate your career. Had it not been for my mentor, Amit Kanvinde, I would not have applied for my current position as Assistant Professor at Fresno State. As a mentor, I understand Mr. Miller's warning not to question your mentor. It's a subtle difference between asking questions and questioning someone, but a potential mentor is more inclined to want to mentor someone or continue to mentor them if they feel the individual values their advise, which is hard to feel if the mentee questions what they have to say.
9. When problem solving, get all the facts. By the way, you will never get all the facts. And when you get the facts, be aware that some of the facts aren't actually facts. (Isn't problem solving fun?)
10. And lastly, to develop customers for life, you need to exceed expectations. Apparently research indicates that if you do not meet expectations, then on average a customer will tel 20 people. If expectations are met, customers don't tell anyone. They got what they paid for, which isn't something worth raving about. However, when expectations are exceeded, customers tell everyone (this number could probably be refined through research). I'm not sure how the internet may have affected these numbers, but the point is that exceeding expectations is the key to keeping customers.
No comments:
Post a Comment