Mechanical Failure Modes Fracture Fatigue Creep An oil tanker - - PowerPoint PPT Presentation
Kasetsart University 213211: Mechanical Failure Mechanical Failure Modes Fracture Fatigue Creep An oil tanker that fractured in a brittle manner by crack propagation around its girth. 144 Dr.Peerapong Triyacharoen Department of
Dr.Peerapong Triyacharoen Department of Materials Engineering
213211: Mechanical Failure
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An oil tanker that fractured in a brittle manner by crack propagation around its girth.
Dr.Peerapong Triyacharoen Department of Materials Engineering
213211: Mechanical Failure
145
Ductile: warning before fracture Brittle: No warning
Dr.Peerapong Triyacharoen Department of Materials Engineering
213211: Mechanical Failure
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Dr.Peerapong Triyacharoen Department of Materials Engineering
213211: Mechanical Failure
147
necking void nucleation void growth and linkage shearing at surface fracture
50 mm
Particles serve as void nucleation sites.
50 µm
100 µm
Dr.Peerapong Triyacharoen Department of Materials Engineering
213211: Mechanical Failure
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3µm 4 mm 160µm 1 mm
304 S. Steel 316 S. Steel Polypropylene Al Oxide
Dr.Peerapong Triyacharoen Department of Materials Engineering
213211: Mechanical Failure
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Dr.Peerapong Triyacharoen Department of Materials Engineering
213211: Mechanical Failure
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Ductile to Brittle Transition Temperature More Ductile Brittle
Dr.Peerapong Triyacharoen Department of Materials Engineering
213211: Mechanical Failure
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Dr.Peerapong Triyacharoen Department of Materials Engineering
213211: Mechanical Failure
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tension on bottom compression on top counter
motor
flex coupling bearing bearing specimen
σmax σmin
time σm S
Dr.Peerapong Triyacharoen Department of Materials Engineering
213211: Mechanical Failure
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Sfat case for steel (typ.) N = Cycles to failure 103 105 107 109 unsafe safe S = stress amplitude
case for Al (typ.) N = Cycles to failure 103 105 107 109 unsafe safe S = stress amplitude
Dr.Peerapong Triyacharoen Department of Materials Engineering
213211: Mechanical Failure
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(to suppress surface cracks from growing)
bad bad better better
C-rich gas put surface into compression shot
N = Cycles to failure moderate tensile σm larger tensile σm S = stress amplitude near zero or compressive σm
Dr.Peerapong Triyacharoen Department of Materials Engineering
213211: Mechanical Failure
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elastic primary secondary tertiary T < 0.4 Tm INCREASING T
t