Page 350 - Marine Structural Design
P. 350
326 Part III Fatigue and Fracture
no =411110 1 -0.3523
Example 16.2: Fracture Mechanics Based Crack Growth Life Integration
Problem: Assuming that a very wide plate is subjected to a contact amplitude uniaxial cyclic
loading that produces nominal varying stresses between 200 MPa and -100 MPa, Critical
stress intensity factor is K, =lo4 MPa & . Material constants m=3, C=7.1E-12
in /(MPa&)' . What is the fatigue life if the initial crack length is less than 2.5 mm?
Solution:
Crack growth can be predicted using Paris Equation. Integration of this equation involves
numerical methods unless F is independent of crack length. In an infinite plate under uniform
tension, F is constant (16.12). The compressive stress of -100 MPa may be ignored in the
fracture calculation. The critical crack length at final fracture can be obtained from Eq.( 16.9),
Integrating the Pans equation @.( 16. lo), the constant amplitude fatigue life can be estimated
as
16.8 References
1. Almar-Naess, A. (1 985), "Fatigue Handbook, Offshore Steel Structures", Tapir, Norway.
