7.0 - σ F ♦ true strain at failure ε F Ceramics are more brittle than metals Typically their TS<<<<< CS The Griffith crack model

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fracture toughness, K 1c – related to toughness, a material property from Fracture Mechanics. Whereas toughness is a measure of ductility on a macroscopic scale, fracture toughness can be thought of as a measure of ductility on a microscopic scale. resilience – the elastic strain energy that a material absorbs per unit volume. modulus of resilience, U r = y d ε σ 0 The area under the linear portion of the s- e curve. true stress at failure,
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Unformatted text preview: σ F ♦ true strain at failure, ε F Ceramics are more brittle than metals. Typically their TS <<<<< CS. The Griffith crack model explains why: All materials have elliptical cracks that experience a stress intensification at the crack tip given by: σ m = 2 σ (c/ ρ ) 1/2 Ceramics and glasses have a lot of these. A compressive load tends to close, not open the Griffith flaws. Hence, the CS is not affected, only the TS....
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This note was uploaded on 08/10/2009 for the course ENGN 45 taught by Professor Wendy during the Spring '09 term at City College of San Francisco.

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