Toughness measurements are needed to assess the risk of brittle fracture in warship bulls under operational conditions. This demands laboratory testing at minimum service temperatures and loading rates equivalent to hull impact events. However plate thickness is insufficient to permit valid K_Ic determinations at the required sttrength and toughness levels. The master curve approach specified in ASTM Standard E1921 provides an alternative means of quantifying the cleavage fracture resistance in the brittle-to-ductile transition temperature regime. Limited specific fracture toughness master curve, adn a lower bound failure probability, which can be applied to material selection and structural integrity analyses. The determination of T_o and master curves for a 400 MPa yield strength stele plate is described. Variations in speciment orientation and test loading rate have been investigated, and comparisons are made betwen the reference temperature results and those from other standardized fracture tests. It is concluded that the master curve approach is a useful way of quantifying hull toughness for warship fracture control.
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