00:01
So in the first part of this problem, we're going to talk about crystal and material physics and how they relate to engineering.
00:15
So in some of the first engineering courses you take, you may have something like a trust bridge.
00:28
And by the rules of mathematics, we can tell things like how much force is in this member, what are the forces on the reactions, and things like that.
00:39
So that's an analysis problem.
00:41
But engineering wants to take that a step farther.
00:42
We have this member f and let's say we know it's going to be a tube well how big does that tube need to be to support the load so we have our force f each way let's say it's under compression here what's the radius on the outside and what would be the radius on the inside so that this does not fail so we want to prevent failure and to do this we need to know about the material so this is normal stress sigma equals p over a and when we look up the material we would find some sigma maximum or sigma allowable depending on specifically what you're doing and this kind of data comes for materials so a lot of the engineering analysis we do is could more precisely be described as science or mathematics because it doesn't really it is pure in that it's just like with statics we don't even know anything about materials.
01:56
But you take solid mechanics, then you do need to know materials.
02:00
But at the end of the process to complete a design to complete the part, we need to know about what material we choose, and we choose materials based on their material properties.
02:11
And so we need to know materials to understand their properties.
02:16
Crystals is in that same way, because it is just a property of materials.
02:21
But more specifically, for something like crystals, lots of materials have a grain direction.
02:27
So for a bar of aluminum that has been, say, rolled out, the strength this way, vertically is higher than the strength otherwise through the material.
02:43
So to do that, we need to know its crystal structure how the layers of atoms line up or how the individual components stack together to then tell us these kind of maximum stresses that we can have, which is basically just a subset of materials.
03:02
Another important engineering concept is viscosity, which is we have a fluid and it has some friction interior to it so that it tends to stick together as it flows and that there is a resistance as we move through it.
03:20
So there are tons of applications to this.
03:23
A big one is aerodynamics.
03:30
I missed the letter in there, but so any kind of airplane, you know, needs to deal with viscosity to get the most accurate explanation of the drag.
03:45
And even things like cars or trains or anything else that moves through air is going to need to worry about drag a lot.
03:52
That's why lots of cars have a very streamlined shape, right, to minimize drag.
04:00
It's also useful for internal flows.
04:04
So water flowing through a pipe, for example, in a house.
04:09
There is the viscosity so that there is drag in the pipe.
04:13
So the velocity at the wall is less.
04:18
And at the middle, it flows faster...