Engineering Science 1021A/B Lecture Notes - Lecture 18: Fracture, Fracture Toughness
17 May 2018
School
Department
Professor
How do materials fail?
Plastically deform
Accumulate damage
•
Reduce in area
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fracture
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Fracture due to existing loads
Cyclic Loading
Propagate cracks by fatigue
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fracture
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Deform by creep at elevated temperatures
Accumulate damage
•
Reduce in area
•
fracture
•
Summary
Toughness refers to the ability of materials to absorb energy before they
fracture
Tensile toughness is equal to the area under the true stress–true strain
curve
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The impact toughness is measured using the impact test
○
Fracture toughness describes how easily a crack or flaw in a material
propagates.
○
•
Weibull statistics are used to describe and characterize the variability in the
strength of brittle materials
The Weibull modulus is a measure of the variability of the strength of a
material.
○
•
The fatigue test permits us to understand how a material performs when a
cyclical stress is applied
Knowledge of the rate of crack growth can help determine fatigue life
○
•
Microstructural analysis of fracture surfaces can lead to better insights into the
origin and cause of fracture
Different microstructural features are associated with ductile and brittle
fracture as well as fatigue failure
○
•
The creep test provides information on the load-carrying ability of a material at
high temperatures
Creep rate and rupture time are important properties obtained from
these tests.
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•
Failure
Document Summary
Toughness refers to the ability of materials to absorb energy before they fracture. Tensile toughness is equal to the area under the true stress true strain curve. The impact toughness is measured using the impact test. Fracture toughness describes how easily a crack or flaw in a material propagates. Weibull statistics are used to describe and characterize the variability in the strength of brittle materials. The weibull modulus is a measure of the variability of the strength of a material. The fatigue test permits us to understand how a material performs when a cyclical stress is applied. Knowledge of the rate of crack growth can help determine fatigue life. Microstructural analysis of fracture surfaces can lead to better insights into the. Microstructural analysis of fracture surfaces can lead to better insights into the origin and cause of fracture. Different microstructural features are associated with ductile and brittle fracture as well as fatigue failure.
