Microscopy in the physical sciences fractography
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Microscopy in the Physical Sciences - Fractography. A Workshop for Middle and High School Teachers sponsored by Tennessee Technological University Center for Manufacturing Research Departments of Chemical, Mechanical, Earth Sciences and Curriculum and Instruction

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Microscopy in the physical sciences fractography

Microscopy in the Physical Sciences - Fractography

A Workshop for Middle and High School Teachers

sponsored by

Tennessee Technological University

Center for Manufacturing Research

Departments of Chemical, Mechanical, Earth Sciences and Curriculum and Instruction

and The National Science Foundation

Faculty

Chris Wilson (Mechanical Engineering)

June 19, 2003

“It’s all a hoax, but

it 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.

Falling Down is Part of Growing Up


Some never grow up mini baja

Some Never Grow Up (Mini-Baja)


Crack at weld in swing arm

Crack at Weld in Swing Arm


Not quite the deacon s masterpiece

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

More Serious Motivation


What will we learn

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

Fracture Mechanics is…

…an engineering discipline describing the behavior of cracks or crack-like flaws in materials and structures under loading.


Fractography

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

Ranges of Magnification


Microstructural features in metals

Microstructural Features in Metals


Microstructural scale

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

Mechanisms of Fracture


Dimple formation ductile

Dimple Formation (Ductile)


Cup and cone fracture ductile

Cup and Cone Fracture (Ductile)


Polished copper cross section

Polished Copper Cross Section


Dimpled fracture ductile

Dimpled Fracture (Ductile)


Cleavage features

Cleavage Features


River patterns brittle materials

River Patterns (brittle materials)


Quasi cleavage fracture

Quasi-Cleavage Fracture


Fatigue striations

Fatigue Striations


6061 t6 notched round bar

6061-T6 Notched Round Bar


Carbon fiber polymer matrix

Carbon Fiber-Polymer Matrix


0 45 interface in im6 3501 6

0-45 Interface in IM6/3501-6


Ply rupture outer layer

Ply Rupture Outer Layer


Bleed out from natural pore

Bleed-out from Natural Pore


Microballoon experiments

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

Microballoons in IM6/3501-6


Filled vs broken microballoons

Filled vs. Broken Microballoons


Some texts

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

Project Ideas

  • Component failure investigations

  • Fabrication of fiberglass composites

  • Statistics of failure

  • Connections with literature and history

  • ???


A final thought

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 When

And 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


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