Investigations of size effects in tensile tests based on a nonlocal micro-mechanical damage model

Size effects have been observed in most engineering materials. In this work we report a systematic study using a nonlocal damage model based on experiments with size-scaled specimens of a German reactor pressure vessel steel. It is shown that reducing the specimen size will increase the specific material strength in small specimens, which cannot be predicted using a conventional damage model. The nonlocal damage model based on a strain gradient-dependent constitutive plasticity theory reproduces the experimental records. Detailed computations predict, furthermore, that the size effect to the local displacement at specimen failure is correlated with the inverse of the square of the specimen size, O(l2/D2).