Abstract
Crotch corner zones are of considerable concern in investigating the margin of safety against brittle fracture for tee intersections of nozzles with vessels and branch pipes with run pipes. This requires an estimate of stress intensity factor, i.e. K-factor for either postulated or detected cracks in this region. The high computational costs involved in using three dimensional finite elements suggests the development of a simple and accurate method to calculate K-factors for such cracks. In this paper, existing solutions for corner cracks at the intersections of nozzles with plates or vessels are reviewed and an empirical relationship is developed for K-factors of such cracks.
In addition, a general method is proposed to predict K-factors of corner cracks using stress concentration. This method gives results, which are in good agreement with existing data for nozzle corner cracks and is used to predict K-factor for tee-intersections of pipes. The loading considered was internal pressure only.
Résumé
Les zônes de raccordement de coin sont d'un intérêt considérable lors des investigations sur la marge de sécurité contre la rupture fragile d'intersections en T de piètements avec des réservoirs ainsi que de connections de tuyaux latéraux à un tuyau principal. Ceci requiert une estimation du facteur d'intensité de contrainte, à savoir le facteur K, aussi bien pour des défauts supposés que pour des défauts détectés dans ces régions. Les coûts élevés des calculs que comporte l'utilisation d'éléments finis à 3 dimensions suggèrent le développement d'une méthode simple et précise pour le calcul et les facteurs de contrainte K pour ces fissures. Dans ce mémoire, les solutions existantes pour les fissurations de coin aux intersections de piètements avec des tôles et avec des réservoirs sont passées en revue et une relation empirique est proposée pour des facteurs K caractérisant ces fissures.
En outre, une méthode générale est proposée pour prédire les facteurs K de fissures de coin en utilisant la concentration des tensions. Cette méthode fournit des résultats qui sont en bon accord avec les données existantes pour les fissures de coin relatives à des piètements et est utilisée pour prédire le facteur K dans le cas d'intersections en T de tubes. On a considéré comme mise en charge seulement la pression interne.
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Mohamed, M.A., Schroeder, J. Stress intensity factor solution for crotch-corner cracks of tee-intersections of cylindrical shells. Int J Fract 14, 605–621 (1978). https://doi.org/10.1007/BF00115999
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DOI: https://doi.org/10.1007/BF00115999