Inspection Planning for Surface Fatigue Cracks

by P. Friis-Hansen, Technical Univ of Denmark, Lyngby, Denmark,
H. O. Madsen, Technical Univ of Denmark, Lyngby, Denmark,

Document Type: Proceeding Paper

Part of: Probabilistic Mechanics and Structural and Geotechnical Reliability


A reliability based method for planning of inspections to detect surface fatigue cracks is presented. Cracks are described as semi-elliptical surface cracks. The conditions governing fatigue crack growth are uncertain, and the probabilistic method handles uncertainties in e.g. materials properties, initial defect characteristics and loading conditions. The design criterion is expressed through a limiting value for the probability that the crack depth exceeds a critical value during the design life time or between two inspections. Fulfillment of this criterion is obtained by a combination of design specification and in service inspection to detect possible growing cracks. Inspection methods aiming at detecting surface breaking cracks are considered, and the reliability of an inspection method is expressed through the probability of detecting a crack of a certain length. The inspection plan is updated after each inspection to take account of the additional information gained.

Subject Headings: Cracking | Inspection | Fatigue (material) | Probability | Material properties | Detection methods | Defects and imperfections

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