Probability of ship fracture John Kent

3 Contents 1What is brittle fracture 2Material fracture toughness 3Calculation overview 4Results

4 Recent ship fracture

5 What is fracture toughness? a  ?

6 Load displacement trace – no fracture Load Displacement Plasticity and stable tearing

7 Load displacement trace - fracture Load Displacement Brittle fracture

8 Material fracture toughness

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10 Material fracture toughness

11 Material fracture toughness

12 Material fracture toughness

13 Material fracture toughness

14 Calculating fracture probability Limit state function Where K applied comprises: –Wave induced vertical bending stress; –Still water bending stress; –Residual stress.

15 Calculation overview Starting crack, a 0 Propagate to new length,  +a 0 Calculate N Still water distribution

16 Calculation overview Starting crack, a 0 Still water distribution Combine to give load distribution Propagate to new length,  +a 0 Calculate N

17 Calculation overview Starting crack, a 0 Still water distribution Combine to give load distribution Propagate to new length,  +a 0 Calculate N Calculate p f for time step

18 Probability as a function of grade of plate

19 Crack safety - bridge display

20 Bridge display – stresses as a function of ship heading

21 Summary Statistical distributions of material fracture toughness and applied loading Benchmark with observed failure statistics Provide understandable advice for ship’s crew Provide risk reduction methods which crew can implement