lecture 18 - ME 330 Engineering Materials Lecture 18...

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Lecture 18 Fracture Case Studies Stephen D. Downing Mechanical Science and Engineering © 2001 - 2010 University of Illinois Board of Trustees, All Rights Reserved ME 330 Engineering Materials
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ME 330 - Lecture 18 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 1 of 51 This Lecture . .. ± Silver Bridge Disaster ± Fuel Pipeline Failure ± Monitoring with Wireless Sensors
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ME 330 - Lecture 18 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 2 of 51 Silver Bridge
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ME 330 - Lecture 18 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 3 of 51 What’s Different About Silver Bridge? ± First “eyebar” suspension bridge in the U.S. ± First bridge that used high-strength, heat-treated carbon steel ± High Risk: new structure on a new scale, using new materials.
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ME 330 - Lecture 18 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 4 of 51 Silver Bridge Collapse Collapse, Wearne, P. TV Books, NY 1999
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ME 330 - Lecture 18 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 5 of 51 Eyebar 330 Failure Sketch 12” wide 2” thickness 12 6 Brittle Appearance Ductile Appearance 1/8” corroded crack
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ME 330 - Lecture 18 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 6 of 51 Conditions of Failure ± Crack formed by original forging operation ± Quenched and tempered steel ± Stress corrosion cracking ± 32 o F ambient temperature
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ME 330 - Lecture 18 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 7 of 51 In Class Assignment Make an estimate of the maximum allowable flaw size in the eyebar.
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ME 330 - Lecture 18 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 8 of 51 Material Properties σ u = 100 ksi σ y = 75 ksi Ε = 29,000 ksi CVN = 2.6 ft-lb at 32° F CVN = 8.6 ft-lb at 165° F Working stress 50 ksi Charpy V-notch Tests ⎛⎞ =σ π ⎜⎟ ⎝⎠ IC a Ka Y b
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ME 330 - Lecture 18 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 9 of 51 Estimate K IC F at in ksi lb ft in CVN E K o IC 32 6 . 15 ) ( 2 2 3 = F at in ksi lb ft CVN in ksi K o IC 32 0 . 25 ) ( 5 . 15 ) ( = F at in ksi lb ft CVN in ksi K o IC 32 2 . 45 ) ( 35 . 9 ) ( 65 . 1 = Barsom-Rolfe Corten-Sailors Roberts-Newton
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ME 330 - Lecture 18 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 10 of 51 Assume Flaw Geometry π π ⎛⎞ == ⎜⎟ π ⎝⎠ 2 2 2 K (1.12) a a2 Y 0.799 b Two free edges Semicircular shape Corner crack a a
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ME 330 - Lecture 18 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 11 of 51 Critical Crack Size (Best Case) 2 IC critical applied K 1 a 0.799 ⎛⎞ = ⎜⎟ πσ ⎝⎠ = 0.045 in (using Barsom-Rolfe K IC at 32 o F) = 0.407 in (using Roberts-Newton K IC at 32 o F) = 0.125 in (using Corten-Sailors K IC at 32 o F)
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ME 330 - Lecture 18
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This note was uploaded on 10/03/2011 for the course ME 350 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.

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lecture 18 - ME 330 Engineering Materials Lecture 18...

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