Abstract
The thumb-nail shape of a crack front has been observed in a compact tension (CT) specimen, when a fatigue crack is formed ahead of the machined notch in the course of preparation for the fracture toughness testing. Assuming that the distribution of the stress intensity factor K I along the crack front line is equal to that corresponding to the original straight crack front, a slightly curved crack front is obtained with the aid of Paris' law for the fatigue crack growth rate. Comparing the calculated results with the experimental observation in the 10 T CT specimens, whose thickness is 247 mm, it is found that the effect of the stress singularities at the intersection of the crack front line and the free surface can be disregarded and that they show extremely good agreement with each other.
Résumé
On a procédé à l'observation de la forme en ongle que prend le front de la fissure de fatigue que l'on réalise au droit de l'entaille usinée des éprouvettes de traction compactes destinées aux essais de ténacité à la rupture. En supposant que la distribution du facteur d'intensité de contrainte K I le long du front de la fissure est égale à celle correspondant à un front de fissure originalement droit, on obtient un front de fissure légèrement incurvé grâce au recours à la loi de Paris sur la vitesse de croissance d'une fissure de fatigue. En comparant les résultats calculés et les observations expérimentales sur des éprouvettes 10 TCT, dont l'épaisseur atteint 247 mm, on trouver que l'effet de singularités des contraintes à l'intersection de la ligne de front de la fissure et des surfaces libres peut être négligé et que l'accord est extrêmement satisfaisant.
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Yamamoto, Y., Sumi, Y., Shimoyama, T. et al. On thumb-nail pattern of fatigue crack front observed in standard compact tension specimen. Int J Fract 34, 149–157 (1987). https://doi.org/10.1007/BF00019769
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DOI: https://doi.org/10.1007/BF00019769