Font Size: 

In the aeronautic field, the most frequent locations of MSD (Multi Site Damage) are fuselage lap and butt joints. For such components a great part of the fatigue life is related to crack initiation times whilst in comparison propagation times are generally less relevant, so that great interest arises in forecasting the initiation times of fatigue cracks. Most of such initiation numerical models are based on a statistic approach. In this work, which rely on the results of the European research project SMAAC (Structural Maintenance of Ageing Aircraft), ome fatigue initiation models, to be applied to thin or thick section complex structural components, will be reviewed. Analytical expression and numerical results are derived from two different approaches: Order Statistics and Monte Carlo Procedure. Such models are checked by comparing numerical predictions against data coming from experimental tests on a range of specimens, starting with those relatively simple but gradually increasing their complexity. Most of the specimen tested were simulating fuselage structures and were designed in such a way to reproduce the most important phenomena affecting the real items.