Microscopy in the Physical Sciences - Fractography A Workshop for Middle and High School Teachers...
-
Upload
clemence-welch -
Category
Documents
-
view
215 -
download
0
Transcript of Microscopy in the Physical Sciences - Fractography A Workshop for Middle and High School Teachers...
Microscopy in the Physical Sciences - Fractography
A Workshop for Middle and High School Teachers
sponsored byTennessee Technological UniversityCenter for Manufacturing ResearchDepartments of Chemical, Mechanical, Earth
Sciences and Curriculum and Instructionand The National Science Foundation
FacultyChris Wilson (Mechanical Engineering)
June 19, 2003
“It’s all a hoax, butit pays the bills.”
My wife.
Falling Down is Part of Growing Up
Rock-a-bye baby
In the tree top.
When the wind blows,
The cradle will rock.
When the bough breaks,
The cradle will fall.
And down will come baby,
Cradle and all.
Jack and Jill went up the hill
To fetch a pail of water,
Jack fell down and broke his crown
And Jill came tumbling after.
Some Never Grow Up (Mini-Baja)
Crack at Weld in Swing Arm
Not Quite The Deacon’s Masterpiece!
Have you heard of the wonderful one-hoss shay,
That was built in such a logical way
It ran a hundred years to a day,
And then, of a sudden, it—ah, but stay,
I’ll tell you what happened without delay,
Scaring the parson into fits,
Frightening people out of their wits—
Have you ever hear of that, I say?
excerpt from Oliver Wendell Holmes
More Serious Motivation
What Will We Learn
How does breaking things make the world better?
What is fracture mechanics? What is fractography? How is microscopy used in understanding
material and structural failure?
Fracture Mechanics is…
…an engineering discipline
describing the behavior of
cracks or crack-like flaws
in materials and
structures under loading.
Fractography
Fracture surface topography Both macroscopic and microscopic features Wide range of magnification and instruments Much work is done with unaided eye or hand
lens
Ranges of Magnification
Microstructural Features in Metals
Microstructural Scale
Mechanisms of Fracture
Transgranular Fracture Ductile fracture by
microvoid coalescence Brittle fracture (cleavage) Fatigue crack initiation
and growth
Intergranular Fracture Grain boundary
separation with microvoid coalescence
Grain boundary separation without microvoid coalescence
Dimple Formation (Ductile)
Cup and Cone Fracture (Ductile)
Polished Copper Cross Section
Dimpled Fracture (Ductile)
Cleavage Features
River Patterns (brittle materials)
Quasi-Cleavage Fracture
Fatigue Striations
6061-T6 Notched Round Bar
Carbon Fiber-Polymer Matrix
0-45 Interface in IM6/3501-6
Ply Rupture Outer Layer
Bleed-out from Natural Pore
Microballoon Experiments
Mimic natural porsity using glass microballoons
Sizes 5 to 60 m Effect of microballoons
on interface strength and stiffness unknown
Microballoons in IM6/3501-6
Filled vs. Broken Microballoons
Some Texts
Understanding How Components Fail by Donald J. Wulpi
The New Science of Strong Materials (or Why You Don’t Fall through the Floor) by J. E. Gordon
The Science of Structures and Materials by J. E. Gordon
Fractography by Derek Hull To Engineer is Human by Henry Petroski
Project Ideas
Component failure investigationsFabrication of fiberglass compositesStatistics of failureConnections with literature and history???
A Final Thought
"I Keep Six Honest..."
I keep six honest serving-men(They taught me all I knew);Their names are What and Why and WhenAnd How and Where and Who.I send them over land and sea,I send them east and west;But after they have worked for me,I give them all a rest.
Excerpt from Kipling’s The Elephant's Child