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MEKANIKA PATAHAN

DAN ANALISAKEGAGALAN

(Fracture Mechanics and Failure Analys

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F111 cracks

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During word war II 2700 Libertyships built

400 fracture 90 serious 20 total failure 10 broke completely in two

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What is engineering fracture mecha

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Fracture mechanics???

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Correlation between strength of matand fracture mechanics

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Correlation between strength of matand fracture mechanics

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Crack growth and residual strength

crack si ze

cycles

time

residual

strength

c

design strength

expected highes t

service load

normal service

loadfailure

may

occurfailure

a b

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Question ??

What is the residual stress as function of crack size? What is critical crack size?

How long does it take for a crack to grow from certain initialthe critical size?

What size of pre-existing flaw can be permitted at the mom

structure starts its service life?

How often should the structure be inspected for cracks?

(ref: D. Broek, Elementary engineering fracture mechanics)

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Mechanical Behaviour of Materials

Basics (stress & strain, elasticity)

Plasticity (yield criteria, hardening, instability)

Fracture Mechanics

KI, crack tip plasticity, G,J integral, CTOD

Fracture Toughness

ductile & brittle fracture, effect of microstructure

Fatigue (crack propagation & initiation)

Environment-Assisted Cracking (mechanisms in metals & polymers, te

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The broad field of fracture mechanic

10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 10-0

T

T

T

T

f racture f racture processes

and criteriaplast icity test ing a

meters

materials science engineering

applied mechanics

f racture mechanics

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Historical review of fracture mechananalysis

1920 Energy Balance (Griffith)

1944 Application to brittle fracture of metals (Zener & Ho 1948 Energy Release Rate (Irwin)

1955 Stress-Intensity approach (Irwin)

1960 Correction for plasticity (Irwin, Dugdale)

1961 Crack Opening Displacement (COD) concept (Wells)

1968J integral (Rice)

1969 Local fracture criteria (Rice)

1979 Description of crack growth (Paris)

1983 Failure Assessment Diagram (Bloom)

1993 Constraint-based fracture mechanics

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Fracture mechanics concept

The flaw concept was suggested by Griffith and although it pmajor conceptual advance, it still did not adequately describcracking process.

The Inglis solutionthe stress, , at the tip of an elliptical

Habibie:

Retardation factor to predi

propagation (stress intensit

and material properties)

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Fracture mechanics

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Fracture mechanics

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Fracture mechanics

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Fracture Mechanics and Failure Ana