Wednesday, November 10, 2004

Engineering Perspectives

The quote below is from a fellow Mechanical Engineering major, from a different year than I am. It's a good commentary on the major of Engineering here, seeing as sometimes it seems easier to actually sit down and figure out how to build a robot rather than actually try to sort through the latest homework and tests.
Seeing as I am an Engineering Major and all, and this week has a lot of homework, I thought I'd stay in the spirit of things and post a semi-technical entry here. If nothing else, the non-poetic Engineers in the world can understand at least one of my posts here. =)
These are just some notes on my views of life, with a corresponding correlation to Engineering information.

Materials Science: Nowadays perfection seems to be a big goal with people. As if you have to be perfect to be worthwhile knowing or something. Well, my friends, it's just not practical. Sometimes it isn't even desirable. I will illustrate with information from Materials Science.
Everybody's different. Different metals have different properties. Titanium is really strong but can't withstand high temperatures. Aluminum is strong for its weight and is extremely resistant to rust. Gold is not only a very precious metal, but is also an extremely good conductor. We need all these different metals. Not everyone can be gold, we'd have no airplanes or bridges of strong structures. Gold is extremely malleable, and can't hold much weight. Each metal has it's own strengths and weaknesses, just as each person does. And besides, if everyone were the same this world would be a pretty lonely place.
Perfection is impossible. Even the most time-consuming processes can't achieve a metal that's 100% pure, there are always imperfections. Even a metal that's 99.99% pure has many imperfections on the atomic level, especially if your sample is large enough that you can actually use it for something. There's always going to be a few different elements interspersed throughout the sample. And even assuming that those could be removed, there's still the imperfections in the crystallization to worry about. You can't get rid of every defect and dislocation.
Imperfections are stronger. Yes, that's right, I typed that correctly. For example, which is stronger: steel or iron? Steel. Steel, by the way, is an alloy of Iron and Carbon. Alloys are stronger than pure metal because you can mix the two properties together, plus the sizes of the atoms makes it more difficult for the material to fracture. Imperfections make things stronger, both metals and people. Defects and dislocations also strengthen the material. The more dislocations there are, the less they can move, and hence to higher shearing forces the material can withstand.
What some see as a weakness, others see as a strength. There are two big properties when dealing with metals that cannot coexist. The stronger and harder a metal is, the more brittle and less ductile it is. That means that while it may hold more weight, it won't bend before breaking. In many cases the metal will just fracture, and there's the end of it. Ductile materials can hold on long after they have yielded to the pressure.

Mechanics of Solids:
In everyday life there's some stress involved. Mechanics of Solids is the study of stresses, tensions, compressions, shears, torsions, and other forces in different materials. It analyzes the strengths and weaknesses of each material and determines if the material is strong enough for the job at hand.
Know your weaknesses, and counterbalance them. Concrete is an extremely strong material under compressive loads. Build a column out of concrete and it can withstand great forces pushing downward -- but come at it from the side and it'll fracture easily. Or even more threatening, apply a tension force to both sides and the concrete will pull apart. Concrete hates tension. So why are bridges built out of it? Because the concrete doesn't do the job alone. Steel does very well in tension. Pull it apart and it can withstand huge tension forces, especially compared to concrete. Put it in compression, however, and the concrete will last longer. If you mix the two materials together the steel will carry the tension forces and the concrete will carry the compressive forces. Concrete bridges have bars of reinforcement steel at the bottom of each beam, the spot where the tension builds. Some bridges even use prefabricated prestressed concrete beams, which means that the steel is put in tension, then the concrete poured around it. When the concrete dries the tension forces are released, causing the steel to release some of it's tension forces by putting the concrete into compression. The two materials complement each other well. Yet the steel is only placed where it is needed. Steel isn't applied to the entire beam, only to the bottom. Know your weaknesses, know them well, and counteract them only as necessary.
Know when you cannot counterbalance your weaknesses. Sometimes a material just isn't the right one for the job. Don't be afraid to say "no" if you know someone could do it better. Doing your best doesn't mean that you should take a job larger than you can handle. Stick to your own strengths, and delegate the rest.
Know your limiting factors. Sometimes a material can withstand huge shear loads, but add a little torsion (twisting) and the material will fail. Know your strengths and weaknesses, know your limiting factors, and be sure to check out all your limits before determining if something is inside or outside your range of abilities. A material, once it has yielded, will never return to its original shape.
Sometimes solutions that seem like they will work actually have the opposite effect. An example of this would be a nonuniform circular shaft under torsion. If one metal fails under the torsion, logic would dictate that you make the shaft thicker, right? Wrong. Making it thicker only makes the system send more torsion to that part of the shaft. If you make it thinner then the other section will take more of the torsion, and the member will be less likely to fail.

Manufacturing Engineering: There are many different methods to use to get to your final goals, and not all are fit for every situation. Sometimes care must be taken to pick the right method.
Different methods work for different subjects. There is no single process that can be used in all cases to get the desired final result. Iron is good for casting but bad for machining. Titanium is tricky to machine and insane to cast. Complex structures are better for casting, but only certain types of casting and materials will work. Sometimes you only want to take little bites of metal off at a time; sometimes you can take big chunks. Aluminum is tricky to machine cut because of its ductility, leading the shaved shards to collect in long streams that may clog machinery. Dies, on the other hand, can be used quite effectively. Each material has its own set of preferences for methods of forming, machining, and manufacturing in general. I won't even get into welding. No metal has the same properties, so all processes are different. The lesson here? Just because something works for one person doesn't mean you should be upset when it doesn't work for you. Find your own manufacturing process.
Yielding isn't a bad thing. Breaking can make you stronger. There is an entire process for strengthening materials called "Cold Working." This process deforms the metal permanently into the desired shape by stressing it beyond its yield point. The final product is stronger than the original. Just like scar tissue is stronger than regular tissue, sometimes a little stress and some permanent deformation isn't necessarily a bad thing. (Even though it may not be fun at the time.)
Turning up the heat makes things get done faster. No one likes to hear this one, but it's true. The higher the heat is turned up the faster a product can be made. Caution must be used, however. Unless the heat is turned down towards the end, when the product is almost in its desired final shape, the final product will also be weaker. Other methods must be used, and care must be taken, or projects done under high temperatures / elevated important deadlines will be inferior to those done more slowly, no matter how much care was taken at the time.

Dynamics: In a world that's constantly changing, it's good to have a basic understanding of Dynamics and how things change with relation to you. This subject involves a large collection of equations that can be used to describe simple motion (a bungie-jumper) to more complex systems (a satellite's motion around the moon of a planet, calculated based on the view from the sun).
Sometimes one perspective isn't enough. Some things are too complex to determine with regards to only your own personal view. Viewpoints can be cumulative. In Dynamics, adding the motion of the block on the spring to the motion of the pendulum with relation to the block will yield the motion as seen from the base of the spring. Which is a much better option than trying to determine the final motion on your own. Figure out where someone else stands with relation to you, and then ask how they see a certain subject.
Sometimes switching the way you view things makes life easier. Sometimes in order to solve a complex Dynamics problem you have to switch your coordinate system. The familiar x,y,z coordinate system is all well and good, but circular motion looks best when viewed in cylindrical coordinates. Don't be afraid to convert your coordinate system to a different one more suited to the problem at hand.
Just because someone's perspective is different than yours doesn't mean one of you is wrong. You might be standing on different spots, using different coordinates. People on earth used to thing the sun rotated about the earth instead of the other way around. Which was right -- from their point of view. Someone in freefall who drops a quarter will say the quarter is floating, while someone on the ground will say the quarter is falling. Different perspectives all add up to the big picture.

Thermodynamics: Thermodynamics is a complex subject dealing mainly with heat transfer. There is one key point in Thermo that applies to life in general.
Nothing is 100% efficient. No matter how hard you try there will always be some wasted energy. So don't get frustrated. Do your best, but don't be afraid to take a little time off for something relaxing if you think you can still get everything done that needs done. Less stress helps you think better, anyway.

Computer Engineering: In this day and age, computers are everywhere. They're inescapable. Unlike human beings, computers need to be told exactly what to do; they can't be creative and think up things on their own. The creativity is left up to us.
There is more than one way to accomplish anything. In designing computers, some ways are faster, some slower, some less efficient. Sometimes you can make things more complicated, sometimes less complicated, and the thing that works best for one situation may not always be the best choice for the next. If you're adding two numbers just add them, if you're adding ten use a loop with an array. When using logic AND and OR gates may be used, or NAND and NOR. One is easier to design, the other computes faster. BLT (Branch if Less Than) and BNE (Branch if Not Equal) can sometimes be used interchangeably, other times one works and the other doesn't. There are many roads to the same destination, and the route you pick depends mainly on what's important about how you get there.

So that's how Engineering Principles can relate to real life.



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