Evaluation of Fracture Toughness by Chevron V-Notch Method

The chevron notch (CN) method has an advantage that the crack length need not be measured to estimate fracture toughness. The crack, however, should grow stably until the critical length to get the valid fracture toughness value, which was hardly attained by a conventional CN method. Therefore, a chevron V-notch (CVN) method has been developed to assure the stable crack growth by using a sharp V-notch technique. The sharp V-notch was machined by a V-shaped diamond cutting wheel. The results obtained are: (1) A stable crack extension was observed throughout until unstable crack extension occurs. (2) The fracture toughness values evaluated by the CVN technique coincided very well with those by the single edge V-notched beam (SEVNB) method and those by the single edge precracked beam (SEPB) method. (3) The fracture toughness evaluated by the CVN technique showed quite narrow scatter, whereas those by the conventional CN method with the notch width of 0.1mm showed wide scatter.