EGN3365-8

EGN3365-8 - Chapter 8 Mechanical Failure ISSUES TO ADDRESS How do flaws in a material initiate failure How is fracture resistance quantified how do

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 8 - 1 ISSUES TO ADDRESS. .. • How do flaws in a material initiate failure? • How is fracture resistance quantified; how do different material classes compare? • How do we estimate the stress to fracture? • How do loading rate, loading history, and temperature affect the failure stress? 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 8: Mechanical Failure Adapted from chapter-opening photograph, Chapter 8, Callister 7e. (by Neil Boenzi, The New York Times .)
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Chapter 8 - 2 Fracture mechanisms • Ductile fracture – Occurs with plastic deformation • Brittle fracture – Little or no plastic deformation – Catastrophic strain engineering stress TS Typical response of a metal
Background image of page 2
Chapter 8 - 3 Ductile vs Brittle Failure Very Ductile Moderately Ductile Brittle Fracture behavior: Large Moderate % AR or % EL Small • Ductile fracture is usually desirable! Adapted from Fig. 8.1, Callister 7e. • Classification: Ductile: warning before fracture Brittle: No warning
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Chapter 8 - 4 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: Failure of a Pipe Brittle failure: --many pieces --small deformation
Background image of page 4
Chapter 8 - 5 • 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
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Chapter 8 - 6 Stress-Strain Behavior versus Temperature • Ductility is reduced with temperature reduction. So, Ambient and Operating temperatures can affect failure mode of materials. Such an effect shows Ductile to Brittle Transition. Adapted from D. Johnson choose materials with D-B transition T far away from its usage T
Background image of page 6
Chapter 8 - 7 Ductile vs. Brittle Failure Adapted from Fig. 8.3, Callister 7e. cup-and-cone fracture brittle fracture
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Chapter 8 - 8 Chevron marks From brittle fracture Origin of crack Fan-shaped ridges coming from crack Brittle Fracture Surface Adapted from D. Johnson
Background image of page 8
Chapter 8 - 9 Inter granular ( between grains) Intra granular ( within grains) Al Oxide (ceramic) Reprinted w/ permission from "Failure Analysis of Brittle Materials", p. 78. Copyright 1990, The
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/03/2011 for the course EGN 3365 taught by Professor Jiuhuachen during the Fall '09 term at FIU.

Page1 / 31

EGN3365-8 - Chapter 8 Mechanical Failure ISSUES TO ADDRESS How do flaws in a material initiate failure How is fracture resistance quantified how do

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online