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카테고리
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학습트랜스크립트
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00:26heav입니다.
00:32θ의 파악,
00:36불소bar,
00:40동기만 파악하는 것
00:44문제를 ing кл veut
00:50っち iç 내일의 과학과
00:54슬프로더의 차단의 차단의 차단을 보였습니다.
00:59왜 이 차단의 차단이 필요가 중요합니다?
01:03왜냐하면 지자도 차단의 차단이 필요가 없습니다.
01:08이 차단의 차단의 차단이 중요합니다.
01:12이 차단의 차단은 회사와 기술의 차단을 보였습니다.
01:19이 시각 세계는 세계적으로 위험한 것입니다.
01:24하지만 이 시각 세계적으로 위험한 것입니다.
01:32우리가 이 시각 세계적으로 위험한 것입니다.
01:38우리가 위험한 것입니다.
01:43works or studies if we can do so engineers are trying to figure out the mechanism of this failure
01:52and we are going to do learn how to protect our material from this failure
02:03so by doing this by the end of this lecture
02:07We should be able to explain ductile and brittle fracture mechanism and appearances
02:15And then understand why real strengths are lower than theoretical values due to all these flaws
02:24And a lot of things
02:27And here's the issues to address
02:30Then how do cracks that lead to failure form
02:37And how is fracture resistance quantified
02:42And how do the fracture resistances of the different material classes compare
02:48And then how do we estimate the stress to fracture
02:53And how the loading rate and loading history and the temperature affect the failure behavior of materials
03:02So based on this
03:05I can say we have to do some sort of like a numbering
03:11You know, so I mentioned that before
03:14If we cannot explain it with numbers
03:17That's not a science, right?
03:19So we will do some quantification
03:23And then based on that numbers
03:27We will figure out how we can prevent this kind of failure and how
03:33You know, like
03:36This looks quite large shape
03:41It has failure
03:43So this normal failure occurs at some lower temperature or some strange situation
04:03Okay, let's begin with the basic fracture mechanism
04:09Here like
04:11There are two kinds of the basic mechanism
04:15The fracture is the separation
04:17This is the fracture is the separation of a body into two or more pieces under stress
04:23We will focus on simple fracture under tensile loads at relatively low temperature
04:30Then later expand to fatigue and creep
04:34So I mentioned that like
04:38There are two primary fracture mechanism
04:41The first one is the ductile fracture
04:44Involves that significant plastic deformation prior to fracture
04:49It's a slower and tends to be stable
04:54Meaning crack growth requires increasing stress
04:57So accompanied by significant plastic deformation
05:02That's the main issue
05:08And brittle fracture
05:10Involves little to no plastic deformation
05:16With like a rapid unstable crack propagation
05:20It's a sudden and often catastrophic
05:23In practice
05:25The same and the metal can behave ductile or brittle
05:31So you have the same material
05:34But that shows like a ductile fracture
05:37And sometimes brittle fracture
05:39When?
05:40Depending on temperature, strain rate, and stress state
05:45This is why the conditions are affecting the matter very importantly
05:53A ductile material at room temperature may turn brittle at low temperatures
05:59Or under high loading rates
06:03Under high loading rates
06:05So that's the main thing we should go
06:27And also we can just contrast this behavior
06:34Ductile material absorb high energy
06:37So ductile material absorb high energy before fracture occurs
06:44And then showing large percent elongation
06:48Large percent of elongation
06:51Because it's survived for that long time
06:55And the reduction in area
06:58Brittle materials absorb relatively little energy
07:02And fail abruptly
07:04Abruptly
07:05It looks like a little abrupt
07:10But it's moderately ductile
07:12And in the case of brittle
07:14It's like a sudden one
07:16So it's ductile
07:19And this is also ductile
07:22Moderately ductile
07:23But this is like brittle
07:25The important thing is here
07:29Like no warning
07:30We cannot guess where this brittle fracture occurs
07:35We know that
07:37We are engineers
07:38But I mean
07:39It doesn't show any warnings here
07:44Like a warning before fracture
07:47You know
07:48It gets some necks
07:50It's thinner
07:51It's getting thinner
07:53And elongated a little bit
07:59So
08:00Which one do you prefer?
08:03If you have a material
08:05And
08:06We don't know yet
08:08It's ductile
08:09Or it's brittle
08:11Which one do you want it to be?
08:13Like
08:14So
08:18Let's say
08:19You have a car
08:20Or you have a chair
08:21Then
08:24If it's ductile
08:26You sit it there
08:27And then
08:28Stand up
08:29All the time
08:30And suddenly
08:31It breaks down
08:33That's
08:34Kind of brittle
08:35Then
08:37You may collapse
08:38Right?
08:39On the
08:40On the floor
08:41If it's ductile
08:43We know
08:44It's
08:45That
08:46The chair
08:47Is changing
08:48So we can take a look
08:49What's gonna happen
08:50Then
08:51If that looks
08:52Pretty severe
08:53Then
08:54We can
08:55Replace the chair
08:56Or
08:57Repair the chair
08:59To avoid
09:00That kind of
09:01Situation
09:02But
09:03In the case of
09:04Brittle
09:05We don't know
09:06The warning sign
09:07So
09:08We don't prefer
09:09That
09:10To the other
09:11One
09:12So
09:13Remember
09:14That
09:15The same
09:16Alloy
09:17Can shift along
09:18The ductile
09:19To brittle
09:20Spectrum
09:21In temperature
09:22Or strain rate
09:23Or
09:24Contraint
09:25Later
09:27We will see
09:28The ductile
09:29So
09:30Ductile
09:31To
09:32Brittle
09:34Transition
09:35Temperature
09:36So
09:38We
09:39We skip
09:40This one
09:41DBTT
09:42DBTT
09:45Ductile
09:46To
09:47Brittle
09:48Transition
09:49Temperature
09:50So
09:51Maybe
09:52Somehow
09:53Temperature
09:54Is
09:55More
09:56Important
09:57For
09:58Regular
09:59Material
10:00Right
10:01So
10:02That's
10:03Why
10:04It has
10:05Some sort
10:06Of
10:07This
10:08Name
10:09So
10:10For
10:11The
10:12Visualization
10:13Ductile
10:14Fracture
10:15Often
10:16Show
10:17Like
10:18A
10:19We will see
10:20Granular
10:21Shape
10:22There too
10:23With
10:24Facets
10:25Or
10:26Intergranular
10:27Features
10:28We will see
10:29Images
10:30Right
10:31Next
10:32So
10:33Here are
10:34Examples
10:35The
10:36Ductile
10:37Failure
10:38One
10:39Piece
10:40Large
10:41Deformation
10:42See
10:43And
10:44You see
10:45Some
10:46Bulging
10:47This is
10:48Bulging
10:49And
10:50This
10:51Could
10:52Be
10:53Necking
10:54So
10:55Necking
10:56Is
10:57Kind
10:58Like
10:59This
11:00And
11:01The
11:02Slow
11:03Lick
11:04Before
11:05Final
11:06Rupture
11:07And
11:08Brittle
11:09Failure
11:10Multiple
11:11Pieces
11:12And
11:13Minimal
11:14Deformation
11:15Small
11:16Deformation
11:17And
11:19In
11:20Most
11:21Cases
11:22We
11:23See
11:24Both
11:25When
11:26You
11:27I hope
11:28You
11:29Don't
11:30See
11:31This
11:32Kind
11:33Of
11:34Accidents
11:35Scene
11:36From
11:37The
11:38News
11:39Or
11:40Any
11:41Video
11:42Clip
11:43And
11:44Pictures
11:45Then
11:46We
11:47See
11:48Any
11:49Fractures
11:50Around
11:51The
11:52Car
11:53And
11:54But
11:55Also
11:56Some
11:57Of
11:58The
11:59Car
12:00Parts
12:01Are
12:02Just
12:04So
12:05Why
12:06Do We
12:07See
12:08Both
12:09Thinking
12:10Operating
12:11Temperature
12:12And
12:13Strain
12:14Rate
12:15And
12:16Something
12:17Like
12:18Pressure
12:19Surge
12:20Or
12:21Slow
12:22Pressurization
12:23And
12:24Stress
12:25Concentration
12:26In
12:27ducts
12:28Or
12:29Pipelines
12:30Corrosion
12:31Can
12:34So
12:37Here
12:38Are
12:39The
12:40Mechanism
12:41Let's
12:42See
12:43Like
12:44Some
12:45Failure
12:46Stage
12:47In
12:48Sequence
12:49So
12:50The
12:51Necking
12:52Occurs
12:53Tensile
12:54Strength
12:55Sigma
12:56Occurs
12:57Then
12:58Necking
12:59Initiates
13:00Local
13:01Region
13:02Nucleates
13:03The
13:04Microvoid
13:05You
13:06See
13:07Like
13:08A
13:09Very
13:10Small
13:11Voids
13:12Inside
13:13And
13:14Then
13:15Second
13:16Phase
13:17Particles
13:18Or
13:19The
13:20Interfaces
13:21That
13:22Becomes
13:23Seeding
13:24For
13:25This
13:26Kind
13:27Of
13:28Void
13:29Growth
13:30Gets
13:31Like
13:32One
13:33Piece
13:34And
13:35Shearing
13:36At
13:37Surface
13:38Shearing
13:39Is
13:40Like
13:41A
13:42Pressure
13:43Parallely
13:44To
13:45The
13:46Tensile
13:47Strength
13:48And
13:49Finally
13:50Fracture
13:51Curls
13:52So
13:53If
13:54We
13:55Take
13:56A
13:57Look
13:58The
13:59Shape
14:00And
14:01Then
14:02We
14:03See
14:04Many
14:05Dimples
14:06On
14:07It
14:08And
14:09Also
14:10Like
14:11Some
14:12Particles
14:13Serve
14:14As
14:15Void
14:16Nucleation
14:17Site
14:18So
14:19Under
14:20This
14:21Microscope
14:22And
14:23Footprints
14:24Of
14:25Those
14:26Microbots
14:27So
14:28For
14:29The
14:30Polis
14:31Forensic
14:32Situation
14:33They
14:34Are
14:35Looking
14:36At
14:37All
14:38These
14:39Facets
14:40To
14:41See
14:42If
14:43This
14:44Is
14:45Related
14:46To
14:47Any
14:48Kind
14:49Of
14:50So
14:51Like
14:52Visually
14:53Moderately
14:54Ductile
14:55And
14:56Brittle
14:57Failure
14:58Curb and
14:59Cone
15:00Fracture
15:01And
15:02Brittle
15:03Fracture
15:04You
15:05See
15:06Just
15:07Facet
15:08Flat
15:09But
15:10That's
15:11Normally
15:12Like
15:13If
15:14We
15:15Have
15:16A
15:17Single
15:18Photo
15:19Stable
15:20Growth
15:21And
15:22Flat
15:23Granular
15:24Texture
15:25Implies
15:26Sudden
15:27Brittle
15:28Crack
15:29Advance
15:30In
15:33Brittle
15:34Fracture
15:36Cracks
15:38Provocates
15:39Rapidly
15:40With
15:41Minimal
15:42Plasticity
15:43The
15:44Fracture
15:45Surface
15:46Is
15:47Perpendicular
15:48To
15:49Applied
15:50Tensile
15:51Stress
15:52Maybe
15:53In
15:54This
15:55Case
15:56Tensile
15:57Goes
15:58That
15:59Way
16:00And
16:01Then
16:02Normally
16:03Occurs
16:04Perpendicular
16:05To
16:06That
16:07Applied
16:08Tensile
16:09Stress
16:10Is
16:11The
16:12V
16:13Shape
16:14Like
16:15Mountain
16:16Shape
16:17And
16:18Radial
16:19Ridges
16:20And
16:21They
16:22Help
16:23Locate
16:24Where
16:25Crack
16:26Really
16:27Started
16:28Open
16:29Notch
16:30And
16:31Surface
16:32Defect
16:33And
16:34The
16:35Toe
16:36Or
16:37Corrosion
16:38So
16:39This
16:40Is
16:41Very
16:42Important
16:43For
16:44Forensics
16:45Crack
16:46Initiation
16:47Poets
16:48Metaphor
16:49Forensics
16:50They
16:51Guide
16:52Corrective
16:53Actions
16:54Improves
16:55Surface
16:56Finish
16:57And
16:58Removes
16:59Sharp
17:00Corners
17:01Polishing
17:02Short
17:03Pin
17:04Crickle
17:05Zones
17:06The
17:07Inclusions
17:13So
17:14Also
17:15In
17:16Bridal Fracture
17:17Surfaces
17:18There
17:19Are
17:20Like
17:21The
17:22Either
17:23Bridal Fracture
17:24Can
17:25Be
17:26Intergranular
17:27Or
17:28Transgranular
17:30So
17:31They
17:32Have
17:33Same
17:34Images
17:35To
17:36See
17:37The
17:38Difference
17:39Between
17:40Intergranular
17:41And
17:42Transgranular
17:43Fracture
17:44See
17:45Both
17:46Of
17:47Them
17:48Are
17:49Like
17:50Steel
17:51316304
17:52This
17:53Number
17:54Tells
17:55Us
17:56Some
17:57Dopant
17:58Material
17:59So
18:00They
18:01Are
18:02Based
18:03On
18:04Some
18:05Different
18:06Different
18:07Kinds
18:08Of
18:09Small
18:10Amount
18:11Of
18:12The
18:13Other
18:14Materials
18:15Inside
18:16Chromium
18:17Or
18:18Nickel
18:19Mangan
18:20So
18:21I
18:22Don't
18:23Know
18:24Percentile
18:25Of
18:26Those
18:27Additives
18:28So
18:29Here
18:30Intergranular
18:31You
18:32See
18:33Intergranule
18:34So
18:35The
18:36Granule
18:37Looks
18:38Like
18:39All
18:40This
18:41Grain
18:42Between
18:43Grains
18:44So
18:45The
18:46Bridal
18:47Goes
18:48Through
18:49This
18:50Inside
18:51Grains
18:52Through
18:53Grains
18:54Through
18:55Grains
19:02Along
19:03This
19:04Grains
19:05That
19:06Bridal
19:07Fracture
19:08Occurs
19:09So
19:10In
19:11Aluminum
19:12Oxide
19:13Most
19:14Ceramic
19:15Like
19:16Material
19:17Goes
19:18For
19:19Transgranular
19:20Or
19:21Some
19:22Still
19:23This
19:24One
19:25Goes
19:26For
19:27Intergranular
19:28Law
19:29Why
19:30Are
19:31Like
19:32Measured
19:33Strengths
19:34So
19:35Much
19:36Lower
19:37Than
19:38Theoretical
19:39Strengths
19:40Here
19:41This
19:42Is
19:43Theoretical
19:44Strengths
19:45When
19:46It
19:47Shows
19:48Should
19:49Survive
19:50A Lot
19:51Of
19:52Work
19:53For
19:54This
19:55High
19:56Number
19:57Perfect
19:58Material
19:59With
20:00No
20:01Flaws
20:02This
20:03Is
20:04The
20:05Perfect
20:06Material
20:07Trend
20:08Tensile
20:09Strengths
20:10But
20:11In
20:12Real
20:13Cases
20:15Theoretical
20:16Strengths
20:17Is
20:18Much
20:19Much
20:20Higher
20:21Than
20:22Engineering
20:23Strengths
20:24These
20:25Flows
20:26Concentrate
20:27Stress
20:28Tips
20:29Or
20:30Some
20:31Dramatically
20:32Reducing
20:33The
20:34Stress
20:35Need
20:36For
20:37Crack
20:38Propagation
20:39So
20:40Leonardo
20:41Da Vinci
20:42Noticed
20:43Centuries
20:44Ago
20:45Longer
20:46On
20:47It
20:48But
20:49Shorter
20:50Wires
20:51Maybe
20:52The
20:53Density
20:54Might
20:55Be
20:56The
20:57Same
20:58But
20:59Smaller
21:00Number
21:01Of
21:02Defects
21:03So
21:04Larger
21:05Volumes
21:06Statistically
21:07Contain
21:08Larger
21:09Floors
21:10This
21:11Is
21:12The
21:13Essence
21:14Floors
21:15Here
21:16Floors
21:17Cause
21:18Premature
21:19Failure
21:20So
21:21More
21:23Floors
21:24Mean
21:25More
21:26Failures
21:27Large
21:28Samples
21:29Contain
21:30Longer
21:31Or
21:32More
21:33Amount
21:34Of
21:35Floors
21:36So
21:38Let's
21:39Formalize
21:40The
21:41Idea
21:42A
21:43Floor
21:44Act
21:45Like
21:46Stress
21:47Razor
21:48So
21:49Here
21:50Is
21:51Some
21:52Void
21:53Inside
21:54Material
21:55By
21:56Using
21:57It
21:58And
21:59The
22:00Local
22:01Maximum
22:02Stress
22:03Sigma
22:04M
22:05At
22:06This
22:07Condition
22:08And
22:09Here
22:10The
22:11What is
22:12That
22:13Peak
22:14Stress
22:15Scales
22:16With
22:17Given
22:18D
22:19As
22:20Show
22:21Here
22:22And
22:23The
22:25Small
22:26Tip
22:27Radius
22:28Ro
22:29T
22:30And
22:31It
22:32Has
22:33A
22:34Lot
22:35Of
22:36The
22:37Labeling
22:38That's
22:392A
22:40It
22:41Means
22:42This
22:43If
22:44We
22:45Take
22:46A
22:47That's
22:48A
22:49And
22:50Then
22:51You
22:52Know
22:53Where
22:54Ro
22:55T
22:56That's
22:57Related
22:58To
22:59All
23:00These
23:01Numbers
23:02So
23:04Actually
23:05We
23:06Gave
23:07Only
23:08This
23:09Amount
23:10Of
23:11Stress
23:12But
23:13The
23:14Real
23:15Stress
23:16Is
23:17Much
23:18Higher
23:19Than
23:20What
23:21We
23:22Actually
23:23Applied
23:24For
23:25The
23:26So
23:27If
23:28We
23:29Know
23:30This
23:31Kind
23:32Of
23:33Effect
23:34Then
23:35We
23:36Can
23:37Design
23:38How
23:39We
23:40Can
23:41Avoid
23:42This
23:43Kind
23:44Of
23:45Fracture
23:46So
23:47Schematically
23:48Here
23:49If
23:50You
23:51Plot
23:52Stress
23:53Along
23:54So
23:55Sigma
23:56M
23:57Is
23:58Applied
23:59At
24:00The
24:01Void
24:02Tip
24:03That's
24:04The
24:05Maximum
24:06Stress
24:07Far
24:08From
24:09The
24:10Tip
24:11Stress
24:12Returns
24:13To
24:14The
24:15Normal
24:16Sigma
24:17Zero
24:18And
24:19In
24:20A
24:21In
24:22Brittle
24:23Materials
24:24Little
24:25Yielding
24:26Occurs
24:27So
24:28The
24:30Theoretical
24:31Concentration
24:32Is
24:33Realized
24:34So
24:35Let's
24:36Say
24:37We
24:39Have
24:40Some
24:41Engineering
24:42Fracture
24:43Design
24:44To
24:45Avoid
24:46Sharp
24:47Corners
24:48This
24:49Kind
24:50Of
24:51Fillet
24:52And
24:53Then
24:54Width
24:55And
24:56The
24:57Sigma
24:59Max
25:00Can
25:01Be
25:02Given
25:03Here
25:04And
25:05The
25:06Sharp
25:07Fillet
25:08Radius
25:09So
25:10If
25:11We
25:12Can
25:13Design
25:14This
25:15Way
25:16So
25:17The
25:18Sharper
25:19Fill
25:20Means
25:21This
25:22Edge
25:23Is
25:24Going
25:25This
25:26One
25:27This
25:28Way
25:29Which
25:30One
25:31Is
25:32Better
25:33So
25:34Here
25:35The
25:36Stress
25:37Concentrate
25:38Factor
25:39Becomes
25:40This
25:41Way
25:42The
25:43Blue
25:44Graph
25:45Width
25:46And
25:47The
25:48Width
25:49And
25:50This
25:51Is
25:52Just
25:53H
25:54It's
25:55Not
25:56Height
25:57So
25:58Imagine
25:59That
26:00We
26:01Can
26:02Have
26:03Either
26:04This
26:05One
26:06Or
26:07This
26:08One
26:09Can
26:10You
26:11Guess
26:12Which
26:13One
26:14Is
26:15Up
26:16Right
26:17So
26:18If
26:19We
26:20Increase
26:21This
26:22W
26:23That
26:24Means
26:25The
26:26It
26:27Goes
26:28This
26:29Way
26:30And
26:31Concentrate
26:32The
26:33Factor
26:34K
26:35T
26:36Is
26:37Higher
26:38So
26:39That
26:40Means
26:41It
26:42May
26:43Failure
26:44Right
26:45That
26:47Is
26:48Also
26:49Occurs
26:50Depending
26:51On
26:52The
26:53Sharper
26:54Radius
26:55If
26:56It
26:57Sharp
26:58Or
26:59This
27:00Way
27:01This
27:02One
27:03Might
27:04Be
27:05Much
27:06Better
27:07Than
27:08This
27:09One
27:10One
27:11So
27:12It
27:13Says
27:14It's
27:15Quite
27:16Obvious
27:17To
27:18Explain
27:19This
27:20Kind
27:21Of
27:22Thing
27:23So
27:24Maybe
27:25I'd like
27:26To
27:27Put
27:28This
27:29One
27:30This
27:31Graph
27:32To
27:33Figure
27:34Out
27:35Okay
27:36Let
27:40Let
27:41Stop
27:42Here
27:43And
27:44Then
27:45I
27:46Will
27:47Come
27:48Back
27:49With
27:50The
27:51Next
27:52Video
27:53Clip
27:54Thank
27:55You
추천
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다음 순서
20:43
21:57
48:13
43:07
32:58
46:48
21:20
40:13
47:27
33:04
38:05
49:26
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