Chapter 9- Failure

Chapter 9- Failure - c09cof01 Chapter 9: Mechanical Failure...

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Chapter 9 - c09cof01 c09cof01 Chapter 9: Mechanical Failure
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Chapter 9 - 2 ISSUES TO ADDRESS. .. How do cracks that lead to failure form? How is fracture resistance quantified? How do the fracture resistances of the different material classes compare? How do we estimate the stress to fracture? How do loading rate, loading history, and temperature affect the failure behavior of materials? Ship-cyclic loading from waves. Computer chip-cyclic thermal loading. Hip implant-cyclic loading from walking. Adapted from Fig. 22.30(b), Callister 7e. (Fig. 22.30(b) is courtesy of National Semiconductor Corporation.) Adapted from Fig. 22.26(b), Callister 7e. Chapter 9: Mechanical Failure Adapted from chapter-opening photograph, Chapter 9, Callister & Rethwisch 3e. (by Neil Boenzi, The New York Times .)
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Chapter 9 - 3 Fracture mechanisms Ductile fracture Accompanied by significant plastic deformation Brittle fracture Little or no plastic deformation Catastrophic
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Chapter 9 - 4 Ductile vs Brittle Failure Very Ductile Moderately Ductile Brittle Fracture behavior: Large Moderate % AR or % EL Small Ductile fracture is usually more desirable than brittle fracture! Adapted from Fig. 9.1, Callister & Rethwisch 3e. • Classification: Ductile: Warning before fracture Brittle: No warning
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Chapter 9 - 5 Ductile failure: -- one piece -- large deformation Figures from V.J. Colangelo and F.A. Heiser, Analysis of Metallurgical Failures (2nd ed.), Fig. 4.1(a) and (b), p. 66 John Wiley and Sons, Inc., 1987. Used with permission. Example: Pipe Failures Brittle failure: -- many pieces -- small deformations
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Chapter 9 - 6 • Evolution to failure: • Resulting fracture surfaces (steel) 50 mm particles serve as void nucleation sites. 50 mm From V.J. Colangelo and F.A. Heiser, Analysis of Metallurgical Failures (2nd ed.), Fig. 11.28, p. 294, John Wiley and Sons, Inc., 1987. (Orig. source: P. Thornton, J. Mater. Sci ., Vol. 6, 1971, pp. 347-56.) 100 mm Fracture surface of tire cord wire loaded in tension. Courtesy of F. Roehrig, CC Technologies, Dublin, OH. Used with permission. Moderately Ductile Failure necking σ void nucleation void growth and linkage shearing at surface fracture
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Chapter 9 - 7 Ductile vs. Brittle Failure Adapted from Fig. 9.3, Callister & Rethwisch 3e. cup-and-cone fracture brittle fracture
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Chapter 9 - c09f04 c09f04 Ductile failure
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Chapter 9 - 9 Brittle Failure Arrows indicate point at which failure originated Adapted from Fig. 9.5(a), Callister & Rethwisch 3e.
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Chapter 9 - c09f06ab c09f06ab Intra-granular crack propagation
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Chapter 9 - c09f07ab c09f07ab Inter-granular crack propagation
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Chapter 9 - 12 Inter granular ( between grains) 304 S. Steel (metal) Reprinted w/permission from "Metals Handbook", 9th ed, Fig. 633, p. 650. Copyright 1985, ASM
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This note was uploaded on 09/05/2011 for the course EMA 3010 taught by Professor Unknown during the Summer '08 term at University of Florida.

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Chapter 9- Failure - c09cof01 Chapter 9: Mechanical Failure...

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