A higher strain rate would correspond to a shorter loading time,
equivalent to lower temperatures causing the ductile-to-brittle
transition of the specimen. This ductile-to-brittle transition may
be due to the significant influence of strain rate effect. With
strain rate and multiaxiality increasing, the local stress peaks
become so high that
they can reach the microscopic cleavage fracture strength oj of the
material. Brittle
fracture is expected, when the local value of the maximum principal
stress exceeds aJ
over a characteristic distance X, which depends on the
microstructure of the material.
