1
00:00:15,960 --> 00:00:17,733
Ok. Why does this matter?

2
00:00:17,733 --> 00:00:19,250
Well, this is one reason.

3
00:00:19,250 --> 00:00:23,816
If you don't plan your
cold work carefully,

4
00:00:23,816 --> 00:00:26,083
you might make the
material too brittle.

5
00:00:26,083 --> 00:00:27,983
You wanted it to be
so hard because this

6
00:00:27,983 --> 00:00:31,783
was such an important ship and
it was going to be a big deal

7
00:00:31,783 --> 00:00:33,233
and the launch was
really exciting.

8
00:00:33,233 --> 00:00:36,900
And then it cracks in
half, the entire ship.

9
00:00:36,900 --> 00:00:37,533
Why?

10
00:00:37,533 --> 00:00:41,300
Because you didn't look
up what dislocations mean.

11
00:00:41,300 --> 00:00:46,800
You didn't take
3.091, that's why.

12
00:00:46,800 --> 00:00:47,883
That's a pretty big crack.

13
00:00:50,933 --> 00:00:52,316
The main why this matters--

14
00:00:52,316 --> 00:00:54,133
oh, I couldn't help it.

15
00:00:54,133 --> 00:00:57,950
I am a big fan of wind.

16
00:00:57,950 --> 00:01:00,150
Wind energy is
growing and growing

17
00:01:00,150 --> 00:01:04,450
and it's such a great
national resource.

18
00:01:04,450 --> 00:01:07,016
Here's the global capacity.

19
00:01:07,016 --> 00:01:12,333
This is install capacity
for wind turbines.

20
00:01:12,333 --> 00:01:17,183
But see, this is a
mechanical materials problem

21
00:01:17,183 --> 00:01:24,383
that you are now equipped
to think about more deeply.

22
00:01:24,383 --> 00:01:29,050
Because, you see, you can do
a lot of different experiments

23
00:01:29,050 --> 00:01:29,800
on those turbines.

24
00:01:29,800 --> 00:01:32,783
So the blades here are critical.

25
00:01:32,783 --> 00:01:35,850
You can imagine that you
want them to be light,

26
00:01:35,850 --> 00:01:38,583
but if they're too light,
they may not be strong enough.

27
00:01:38,583 --> 00:01:40,200
And then how do they
need to be strong?

28
00:01:40,200 --> 00:01:45,083
Because you've got huge
amounts of wind coming at them.

29
00:01:45,083 --> 00:01:48,666
And it turns out, you need
to hit just the right balance

30
00:01:48,666 --> 00:01:54,583
of elastic deformation before it
goes into some plastic regime.

31
00:01:54,583 --> 00:01:57,133
You need to hit just the
right balance of ductility.

32
00:01:57,133 --> 00:01:58,700
So here's, for example--

33
00:01:58,700 --> 00:01:59,850
these are some simulations.

34
00:01:59,850 --> 00:02:03,300
Here are some experiments on a
new material for a wind turbine

35
00:02:03,300 --> 00:02:04,233
blade.

36
00:02:04,233 --> 00:02:08,583
And then you put it out there
and look at what happens-- ice.

37
00:02:08,583 --> 00:02:12,183
By the way, this ice comes off
at hundreds of miles an hour

38
00:02:12,183 --> 00:02:13,200
in chunks.

39
00:02:13,200 --> 00:02:16,200
These farmers are
not happy about that.

40
00:02:16,200 --> 00:02:17,650
Seriously.

41
00:02:17,650 --> 00:02:18,483
And those are bugs.

42
00:02:21,100 --> 00:02:24,366
Actually, bugs in wind turbine
blades is a serious problem.

43
00:02:24,366 --> 00:02:26,733
How do you clean bugs off of it?

44
00:02:26,733 --> 00:02:29,250
Because it dramatically
changes the aerodynamics

45
00:02:29,250 --> 00:02:30,300
and the efficiency.

46
00:02:30,300 --> 00:02:33,550
It also can damage
the blade itself.

47
00:02:33,550 --> 00:02:35,383
So there's all sorts
of work going on.

48
00:02:35,383 --> 00:02:38,600
How do you make bug-proof
wind turbine blades?

49
00:02:38,600 --> 00:02:39,100
OK.

50
00:02:39,100 --> 00:02:40,716
Well, now just spray
it with something.

51
00:02:40,716 --> 00:02:43,566
Ah, but then does it have
the right plastic deform--

52
00:02:43,566 --> 00:02:45,200
does it have the
right yield point

53
00:02:45,200 --> 00:02:46,416
or is it just going to crack?

54
00:02:49,133 --> 00:02:53,200
And by the way, it's got to
have 5 times 10 to the 9 cycles

55
00:02:53,200 --> 00:02:54,516
before it can fail.

56
00:02:54,516 --> 00:02:56,000
That's the metric.

57
00:02:56,000 --> 00:02:58,200
So that's a pretty
big ask of a material.

58
00:02:58,200 --> 00:03:01,233
It all comes down to
understanding this curve.

59
00:03:01,233 --> 00:03:05,500
And in the broader sense
of materials, this to me

60
00:03:05,500 --> 00:03:08,400
is a very exciting ask.

61
00:03:08,400 --> 00:03:09,850
Why?

62
00:03:09,850 --> 00:03:15,283
Because if you look at a plot
of the density of materials--

63
00:03:15,283 --> 00:03:16,700
heavy, light.

64
00:03:16,700 --> 00:03:17,533
Good.

65
00:03:17,533 --> 00:03:18,850
Kilograms per meter cubed.

66
00:03:18,850 --> 00:03:20,783
And the Young's modulus--

67
00:03:20,783 --> 00:03:25,483
now, this is a measure of
the strength of the material.

68
00:03:25,483 --> 00:03:28,750
It's a measure of
how much strain

69
00:03:28,750 --> 00:03:31,850
you could put on the material
before it breaks or goes

70
00:03:31,850 --> 00:03:32,683
through deformation.

71
00:03:32,683 --> 00:03:34,033
But look at this.

72
00:03:34,033 --> 00:03:36,466
Different materials are here--

73
00:03:36,466 --> 00:03:38,316
rubbers, foams.

74
00:03:38,316 --> 00:03:42,250
OK, foams have relatively
low Young's modulus,

75
00:03:42,250 --> 00:03:43,300
but they're really light.

76
00:03:43,300 --> 00:03:44,783
That could be good.

77
00:03:44,783 --> 00:03:48,733
Up here you've got metals
and alloys, ceramics,

78
00:03:48,733 --> 00:03:50,650
you've got polymers in here.

79
00:03:50,650 --> 00:03:54,550
But notice, I've got so
many different applications

80
00:03:54,550 --> 00:03:57,133
and needs in the
applications and I've

81
00:03:57,133 --> 00:04:01,333
got this plot where I've got
nothing here and nothing here,

82
00:04:01,333 --> 00:04:05,883
even though, if I could
fill this out and dial up

83
00:04:05,883 --> 00:04:11,650
any stress/strain curve for
any density or Young's modulus,

84
00:04:11,650 --> 00:04:13,233
you can make a big
difference in a lot

85
00:04:13,233 --> 00:04:14,300
of different applications.

86
00:04:14,300 --> 00:04:16,882
So I think this is
a great challenge.