§1. Logistics: student presentations [00:03]
There are seventeen students, and I don't yet know which days in April I'll be away. Right now I'm not away any day in April, but it won't stay that way, I guarantee you. So I figured I'd schedule up to six students each week for the first three weeks, and we'll keep a makeup week in reserve. I don't want anybody signing up for the makeup week — that's there in case someone can't make it, or in case I can't make it. We ought to be able to do six students in three days each week. Which three days, I don't know yet. If I tell you ten minutes, you'll take fifteen, and then we still want another five or ten minutes to discuss things.
If you don't care which week, that's fine. I would like everyone to come to class so that the people presenting have an audience besides myself and Dr. Bhamra. Any questions on the presentation? Most people will do it in PowerPoint. Some people could just use the board, the way I do — but I'm the dinosaur around here. Most people know how to use PowerPoint.
§2. The evils of PowerPoint [01:25]
Have I told you about the evils of PowerPoint? The Gettysburg Address in PowerPoint — okay. PowerPoint can be wonderful, but it also can be very sadly abused. The Navy calls it viewgraph engineering. What do you call it in the Air Force? Yeah, viewgraph engineering. So I may critique you on your viewgraphs, not to be mean — although I enjoy ridiculing PowerPoint, not you, but really the mode of PowerPoint.
I was watching one of these faculty candidates the other day. She had these little click buttons on her slides, and when she mentioned something it would wiggle — you know, like on your iPhone app where the icon wiggles when something's having a problem, and it just bounced a couple of times. I thought: tacky. I do like animations in the middle of PowerPoint, though. To me that's one of the values — you can show a short movie clip for ten seconds.
§3. Lester Thurow and the sound-bite revelation [02:40]
I haven't told you about Lester Thurow, have I? In 1988, Lester Thurow taught me to completely revise the way I made presentations at conferences, and it has also influenced the way I teach. I've always known that you can only get two or three ideas across in an hour, and that was a revelation for me in my junior year at MIT. I was taking a course I didn't have to take. I was a materials scientist, and there was a course called 8.211 in the Physics Department, Introduction to Quantum Mechanics. Well, if you're going to understand how a semiconductor works you need to know something about quantum mechanics, so I thought, okay, I'll take this course.
It was taught by Vera Kistiakowsky, whose father George was at Harvard and had won the Nobel Prize in chemistry. Vera was a very strong-willed woman faculty member who always brought this big dog to class with her. She was actually a pretty good lecturer. But I didn't have a clue what was going on in this class. I was getting 15 out of 100 on homework when everybody else was getting 85, and I barely passed a couple of the quizzes. So the night before the final, I just took the book — Eisberg, Fundamentals of Modern Physics — and I decided, okay, I'm just going to pick out the highlights of this course. I sat down for a couple of hours, picked out the highlights, went to the final exam, finished the three-hour final in an hour and fifteen minutes, checked it over the next half hour, walked out, and got an A in the course.
And suddenly — oh, all that other stuff is just fluff. All you need to do is learn the high points. For the rest of my MIT career as an undergraduate, I never really took a lot of notes. And I don't really encourage you to take notes either. If I can't remember something, it's not worth remembering, and it's better to pay attention rather than sitting there scribbling notes and not paying attention. So I would just sit and try to figure out the professor's lecture outline, which was not always the easiest thing to do. A lot of times the professors are trying to hide what's important from you.
I didn't have to study for quizzes anymore because I figured out that at each lecture there are only two or three key points. The last lecture I gave in here, I was talking about anisotropy — that you can have a different strength in plane strain than in uniaxial tension, and that yield leads to yield loci that are not a perfect Tresca or even Von Mises condition, and that leads to differences in drawability. So there are about three points in that whole lecture, if you can boil it down to the two or three key points.
But usually the professors don't tell you what the two or three key points are. My problem in this class is I haven't lectured it for thirty years, and I don't know what the two or three key points are. I'm doing this by feel. The next time I lecture this, I'll look through my notes and they'll be in a more organized fashion, and I'll actually put on the board at the beginning of each day — last time, these were the key points. You might see this in the welding lectures, which I've given for many years.
You need to figure out what the key points are. If you're going to be quizzed in this course — you're not even going to be quizzed, so who cares. But the point is, you can only get one key point across in ten or fifteen minutes, which is why I want you to do a simple project. Don't pick something too complex.
§4. Lester Thurow at Endicott House [07:06]
So the story with Lester Thurow. I was taking — the MIT Sloan School had a Senior Executives program, and Lester Thurow had just become the dean at the Sloan School. A couple of days before the Christmas holidays he sent around an email to all the faculty in the School of Engineering: any engineering faculty member who wanted to take this nine-week intensive course starting in February could take one of the $50,000 tuition slots. This is 1988, so $50,000 tuition was a lot of money for a nine-week course. These would be CEO Type-A-level people coming, and you'd live down at MIT Endicott House. Anybody ever been to Endicott House? It's this big mansion from the 1920s, a French Renaissance mansion that someone donated to MIT.
As far as I could tell, I was the only faculty member in the School of Engineering, out of 350, who applied to do this. My department head was not happy at all, because I was going to have to give up teaching my welding course that fall. But I kept my research going — I'd come in at 4:00 in the morning, get that stuff done, and drive down to Endicott House for the full day. They actually went from about 8:00 in the morning to 8:00 at night, and sometimes I would sleep down there rather than drive home. We also had to spend a week in Washington, D.C. I got to tour the Executive Office Building, and you had people who were assistants to the president giving talks about economics. It was a crash MBA — a nine-week. Harvard had a thirteen-week and still does. MIT now does little two- and three-day things.
Lester Thurow came in to give a talk to us — he actually came in twice. The first time, everyone knew Lester was this great speaker. He called himself an economics educator. He wrote books that came in number two on the New York Times bestseller list. The one person who was ahead of him was Lady Di. "Never compete with a princess" was his catchphrase. Lester was getting $30,000 a lecture to go to some boardroom and give a talk to the board of directors of some company. That's pretty good money in 1988. Not bad today, for a one-hour lecture. He was just a very engaging speaker. He never used overheads or anything else. He'd have a little 3x5 card with a few words written on it, and he'd just talk from whatever he knew. He had his little outline. So to a certain extent, I now use Lester's technique.
The first time Lester came in, all fifty of us — and many of the people in the room were CEOs of billion-dollar companies. Two of them were not CEOs, they were managers. They worked for General Motors, and at General Motors, if your title was manager, you ran a billion-dollar business. One of the guys was in charge of all the lights in automobiles. His part of Delco made all the lights for all the General Motors vehicles. That was a multi-billion-dollar business, but he was a manager at General Motors. He didn't have a big title, but he had a lot of responsibility. I was thirty-eight years old. There was one guy from Xerox who was thirty-three; everybody else was probably post-forty-five. Lester came in, gave this wonderful talk, everybody was just enthralled, including me.
About four or five weeks later, Lester came in a second time, and everybody else was just enthralled again. But I'm the engineer sitting in the back, and I'm trying to figure out: why was Lester so effective as a speaker? After it was all done, I realized he didn't say anything I didn't know — but it was the way he said it. And I realized that going to conferences, and in class, I was doing it the wrong way. You've got to say things in nice little sound bites that people will remember.
The example: a few years later I was listening to Lester talk over at the Marriott Hotel to a bunch of people. He was still the dean, and he was lamenting that the business school up the river, with all their money, tends to hire away some of the best faculty from MIT. Everyone sort of knew he was talking about Robert Merton. Anybody know who Robert Merton was at the time? Robert Merton worked for Black and Scholes, who came up with the algorithm for derivatives — which also brought down the world economy. That's another story if you want to talk about the 2008 crash and why it occurred. Derivatives are a way mathematically to predict what you expect the value of something to be in the future, and we can talk about how they were abused by all the people on Wall Street and in London and elsewhere, and that was what caused the financial collapse. It's not that derivatives are a bad thing — but it had changed the whole world of finance. Black and Scholes were the faculty; they passed away, but Merton won the Nobel Prize when he was at Harvard for this. So it's a fairly well-respected thing.
Lester was describing how Harvard hires away some of our best faculty, but he said, "but fortunately, they tend to hire our extinct volcanoes." Isn't that a great metaphor? No one has to explain what you mean by an extinct volcano when you're talking about some academic, right? So I learned from Lester that sound bites were good. Now, you also have to understand: Lester's colleagues at the Sloan School and in the Department of Economics used to call him Less Than Thorough. Because he didn't really worry about all the facts. He just told a good story — very engaging storyteller. I actually thought it would be even better if I had sound bites with some content. Lester wrote some great books. His other great love was hiking in the mountains.
About a year later, around 1990, I was at a conference and I had to give the keynote speech at some welding conference. I was talking about resistance spot welding, and I said: they put 3,000 spot welds in the average automobile because they need 2,000 good ones. I had a nice slide of that — it wasn't PowerPoint back then. A year later I'm at a welding conference, at the cocktail party, and I hear someone behind me say, "Did you know they put 3,000 spot welds in the average automobile because—" They're quoting the sound bite. If you can learn to speak in sound bites, you can be President of the United States. And you don't even have to have content to your sound bites. Mine actually had some content. It changed the way I gave talks, it changed the way I taught.
No one ever explained to me as a student how important being able to get those things across is. I was talking to one of you about this the other day. I don't spend a lot of time on math, because I told you at the beginning of the class: you're MIT students, I can assume you can do the math. What you need to know is the physics. And most of you had never thought about biaxial loading before. So we're going to talk about biaxial loading today. I just killed the first twenty minutes of class talking about other things — but actually it was probably more useful to your future career than if we had talked about biaxial loading. Because, come on, give me a break, how often are most of you going to have to worry about biaxial loading? But that's what this part of the course is about, so we will talk about biaxial loading.
§5. Earing and the anisotropy ratio [15:41]
We had started to talk about deep drawing, because the R value — the anisotropy ratio — determines whether you get a shallow draw or a deeper draw before you start to get fracturing down here. If you don't have enough pressure on the top, you can get wrinkling, you can get earing. We were starting to talk about earing. Earing can occur at 45 degrees or at 90 degrees to the rolling direction. This is 45, this is no earing, and this is 90 degrees. I showed you those before.
This is what I would have shown you if we hadn't run out of time. This is out of Hosford's book. For steel, copper, and aluminum, all these things are plotted as percent mean ear heights. Some of them are taken as negative because they're ears at 45 degrees, and the ears at 90 degrees are considered positive and the ears at 45 are considered negative. If you plot it as 2ΔR over R-bar, there is a very good correlation between the anisotropy ratio and the extent of earing. We talked about that in terms of the texture that's developed in sheets.
So that finishes us on earing. You want a big R value, but you don't want an R value that's too asymmetric in different directions, or you just end up with ears. You can draw, but you're going to have to cut off the top portion because of the ears. Unless you like ears — but that's a different type of ear.
§6. The forming limit diagram [17:31]
Now I want to talk about the limiting drawing ratio, and tell you the story I said I'd tell you about an auto crash in California. The limiting drawing ratio: you plot the major engineering strain versus the minor engineering strain. This is the strain in the one direction versus the strain in the two direction, so we're talking biaxial loading here. Uniaxial loading would be zero on the E2 axis, and this would be your typical maximum value. For steel, you might get about 30% — this is about 28% elongation before the thing starts to neck down and create problems. Don't worry about diffuse necking; this comes out of Hosford. We're going to go over necking theory probably next week.
This is the experimental forming limit. If they do things well, they can actually get more than the uniaxial tensile elongation ductility. You can get up to over 40% stretch even uniaxially, as you're bending over corners and getting work hardening. But in fact, if you add some biaxial side strain in tension, this thing goes up to almost 50, over 55%. If you give it some squeeze toward plane strain, you can start getting very high effective strains. So your drawability is much different from what you would get predicting ductility from a uniaxial tensile test. Remember, I showed you that on the flanges of the draw you might have plane strain, and then down in the wall you have a different condition. I can't even remember what it is right now, but you have different biaxial loading conditions on the wall versus on the flange. I gave you a picture of that, and I'm sure it's in Hosford. This is what's called the limiting drawing ratio, or the forming limit diagram.
Again, this is low-carbon steel. Why does everybody do low-carbon steel? That's what you make automobiles out of in general. So you can see again a little over 30%, and you can go up to over 100% strain if you give a little side squeeze. If you give a little side tension, you still get an improvement. The worst condition is the uniaxial condition. So the tensile test is giving you the worst thing. The open circles are successful draws, and the closed circles are unsuccessful draws where you got necking and things started to break on you. That's the forming limit diagram.
§7. California ternplate gas tanks [20:43]
Now let me tell you a story about the forming limit diagram. California has much more stringent environmental laws than most of the rest of the country, because — let's face it — they are 18% of the US economy. Some people say, well, if they were a nation unto themselves, which they sort of think they are if you've ever talked to some people from California, they would be the eighteenth largest country in the world economically. So they're pretty dominant in many ways. And California will lead the nation as environmentalists, with things like saying we want partial zero-emission vehicles.
In the early 2000s, California had requirements that were stiffer than the federal government requirements for the total hydrocarbon emissions from a gas tank on a vehicle. Back in the 1980s, people used to use ternplate for making gas tanks. This was low-carbon steel. Anybody know what ternplate is? It's lead-coated steel, just like galvanized steel is zinc-coated steel. If you lead-coat it, same type of thing — just pull it through a lead bath, and if you do it with the right flux you can get a lead coating. Lead has outstanding corrosion resistance in hydrocarbons, in water, and everything else. The roof at Kresge Auditorium has a lead membrane on it. The water pipes, when they first started piping water through London, were lead pipes.