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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

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Microscopy in the Physical Sciences - Fractography

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  1. 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.

  2. 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

  3. Some Never Grow Up (Mini-Baja)

  4. Crack at Weld in Swing Arm

  5. 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

  6. More Serious Motivation

  7. 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?

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

  9. 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

  10. Ranges of Magnification

  11. Microstructural Features in Metals

  12. Microstructural Scale

  13. 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

  14. Dimple Formation (Ductile)

  15. Cup and Cone Fracture (Ductile)

  16. Polished Copper Cross Section

  17. Dimpled Fracture (Ductile)

  18. Cleavage Features

  19. River Patterns (brittle materials)

  20. Quasi-Cleavage Fracture

  21. Fatigue Striations

  22. 6061-T6 Notched Round Bar

  23. Carbon Fiber-Polymer Matrix

  24. 0-45 Interface in IM6/3501-6

  25. Ply Rupture Outer Layer

  26. Bleed-out from Natural Pore

  27. Microballoon Experiments • Mimic natural porsity using glass microballoons • Sizes 5 to 60 m • Effect of microballoons on interface strength and stiffness unknown

  28. Microballoons in IM6/3501-6

  29. Filled vs. Broken Microballoons

  30. 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

  31. Project Ideas • Component failure investigations • Fabrication of fiberglass composites • Statistics of failure • Connections with literature and history • ???

  32. 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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