Ludwik-Davidenkov-Orowan

Tihe brittle-ductile transition of metals as reported by Orowan (I) is explained on the basis that brittle fracture occurs when the yield stress exceeds a critical value. This is based on the Ludwik-Davidenkov-Orowan hypothesis that brittle fracture and plastic flow are independent processes yielding separate curves as a function of temperature and strain rate. Therefore, the operative deformation process is the one occurring at the lower stress. The intersection of the brittle stress and yield stress curves therefore defines the brittle-ductile transition. 

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