Cracks 1 Flashcards
Why is ductile failure preferable to brittle failure?
Ductile = lots of warning
Brittle = sudden & catastrophic
How does toughness relate to brittleness/ductility?
Low toughness = brittle
High toughness = ductile
What is toughness?
A material’s ability to resist a crack
What do brittle/ductile fractures look like?
Brittle: flat
Ductile: cup-and-cone
What must be known about applied loads?
-Magnitude
-Static or cyclic
-Orientation (especially for anisotropic materials)
What methods can be used to calculate loads?
-Analytical
-Numerical
-Experimental
What is the critical load?
The smallest load which can cause failure
What is included in ‘geometry’?
-Shape of the component
-Stress concentrations
-Size, shape and position of any defects
What causes breakages at lower loads than expected after a long usage period?
Fatigue
What are welds sensitive to?
Fatigue- they are fine under static loading
Why are welds difficult to predict?
-Large number of different defects
-Not uniform in geometry
What does critical load calculation depend on?
-Failure mechanism
-Fracture mechanics parameters
-Manufacturing defects
