Evaluation of Fracture Strength for Ceramics with Defects by Numerical Simulation (1st Report, Fundamental Theory and Application to Alumina Ceramics)

Kazuya Mori, Hiroshi Noguchi, Berouz Tabarrok

Research output: Contribution to journalArticle

Abstract

It is well known that the fracture strength of ceramics with small defects is lower than the strength estimated by linear fracture mechanics, based on the strength of a large defect. This phenomenon can be explained by the increase in the crack resistance with crack propagation. This R-curve behavior is caused mainly by grain bridging in the wake of the crack. Recently the grain-bridging stresses for alumina and silicon nitride have been measured experimentally. In this study, the fracture strength is estimated by numerical simulation, based on grain-bridging stresses. In the simulation, the effective stress intensity factor at the crack tip, Kup, and the effective fracture toughness at the crack tip, KuP, are used for the conditions of stable and unstable crack propagation. It is found that the fracture toughness for long cracks, Kup, depends on specimen geometries, and the maximum values of Kc approach (Kup)c as the initial crack length approaches the width of the specimen. Furthermore a convenient method to evaluate (Kup)c experimentally is discussed.

Original languageEnglish
Pages (from-to)984-991
Number of pages8
JournalTransactions of the Japan Society of Mechanical Engineers Series A
Volume60
Issue number572
DOIs
Publication statusPublished - Jan 1 1994

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Aluminum Oxide
Fracture toughness
Alumina
Cracks
Defects
Computer simulation
Crack tips
Crack propagation
Silicon nitride
Fracture mechanics
Stress intensity factors
Geometry

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

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title = "Evaluation of Fracture Strength for Ceramics with Defects by Numerical Simulation (1st Report, Fundamental Theory and Application to Alumina Ceramics)",
abstract = "It is well known that the fracture strength of ceramics with small defects is lower than the strength estimated by linear fracture mechanics, based on the strength of a large defect. This phenomenon can be explained by the increase in the crack resistance with crack propagation. This R-curve behavior is caused mainly by grain bridging in the wake of the crack. Recently the grain-bridging stresses for alumina and silicon nitride have been measured experimentally. In this study, the fracture strength is estimated by numerical simulation, based on grain-bridging stresses. In the simulation, the effective stress intensity factor at the crack tip, Kup, and the effective fracture toughness at the crack tip, KuP, are used for the conditions of stable and unstable crack propagation. It is found that the fracture toughness for long cracks, Kup, depends on specimen geometries, and the maximum values of Kc approach (Kup)c as the initial crack length approaches the width of the specimen. Furthermore a convenient method to evaluate (Kup)c experimentally is discussed.",
author = "Kazuya Mori and Hiroshi Noguchi and Berouz Tabarrok",
year = "1994",
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AU - Mori, Kazuya

AU - Noguchi, Hiroshi

AU - Tabarrok, Berouz

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N2 - It is well known that the fracture strength of ceramics with small defects is lower than the strength estimated by linear fracture mechanics, based on the strength of a large defect. This phenomenon can be explained by the increase in the crack resistance with crack propagation. This R-curve behavior is caused mainly by grain bridging in the wake of the crack. Recently the grain-bridging stresses for alumina and silicon nitride have been measured experimentally. In this study, the fracture strength is estimated by numerical simulation, based on grain-bridging stresses. In the simulation, the effective stress intensity factor at the crack tip, Kup, and the effective fracture toughness at the crack tip, KuP, are used for the conditions of stable and unstable crack propagation. It is found that the fracture toughness for long cracks, Kup, depends on specimen geometries, and the maximum values of Kc approach (Kup)c as the initial crack length approaches the width of the specimen. Furthermore a convenient method to evaluate (Kup)c experimentally is discussed.

AB - It is well known that the fracture strength of ceramics with small defects is lower than the strength estimated by linear fracture mechanics, based on the strength of a large defect. This phenomenon can be explained by the increase in the crack resistance with crack propagation. This R-curve behavior is caused mainly by grain bridging in the wake of the crack. Recently the grain-bridging stresses for alumina and silicon nitride have been measured experimentally. In this study, the fracture strength is estimated by numerical simulation, based on grain-bridging stresses. In the simulation, the effective stress intensity factor at the crack tip, Kup, and the effective fracture toughness at the crack tip, KuP, are used for the conditions of stable and unstable crack propagation. It is found that the fracture toughness for long cracks, Kup, depends on specimen geometries, and the maximum values of Kc approach (Kup)c as the initial crack length approaches the width of the specimen. Furthermore a convenient method to evaluate (Kup)c experimentally is discussed.

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