An assessment of the probability of root failures in load carrying cruciform joints of duplex stainless steel 2205 R. F. Martins1 and C. M. Branco2 1 New University of Lisbon, FCT/DEMI, 2829 Monte de Caparica, Portugal 2 ICEMS/IST, Avda. Rovisco Pais, 1049-001 Lisbon, Portugal ABSTRACT: Fatigue life data and failure probability assessments in these types of joints, fabricated from duplex stainless steel 2205, are comparatively scarce and, therefore, a research study was initiated to assess the fatigue behaviour of load carrying joints of this material and to obtain probability of failure data using the methods of Probabilistic Fracture Mechanics (PFM). Probability of failure results was obtained both for the situations of unstable fracture and fatigue crack growth. For fatigue crack growth, the parameters used were the design stresses for three values of fatigue life (105, 2x106 and 107 cycles), using design curves of two codes, and also experimental S-N curve obtained by the authors in the duplex 2205 material and corresponding to the lower fatigue curve for 95% confidence interval. The K solutions were 2dFE J integral analysis, obtained by the authors, and the BS7910 formulation. Sensitivity analysis of the probability of failure results is presented in the paper. 1. INTRODUCTION Due to high safety and operating costs related with a structural failure, reliability studies of welded structures were published recently [1]. Probabilistic Fracture Mechanics can be used to quantify the probability of failure of a structure. As referred in [1], the application of PFM requires a considerable level of experience, since incorrect failure predictions can happen, due to non-adequate valuable data values, such as fracture toughness and other materials data, and also defect size and distribution in the structure. 2. FUNDAMENTALS DEFINITIONS OF PFM A structural failure is due to occur when the defect sizes in the structure are greater than the safe values calculated with Fracture Mechanics. Assuming a
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