Dynamic ductile evolution and tensile fracture: new experimental insights for models evaluation

摘要

Under dynamic loading conditions, the rapid nature of the fracture process may simultaneously activate a considerable number of nucleation sites for void formation at the region of the tensile stress field. The growth and coalescence of these voids forms the deformation plane and eventually the fracture surface. Attempts to quantify damage evolution during fracture using microstructural observations, specifically for spallation, were pioneered by Seaman and his coworkers. They performed incipient spaliation experiments in which they imposed a peak stress below the spall strength of the material, thereby developing an incipient spallation zone rather than complete separation. When this experimental methodology is applied, recovery techniques are utilized to recover the deformed samples without introducing any additional damage. Seaman and his coworkers, and later Lacomme, et al., developed damage quantification techniques based on area measurements of incipient fracture. However, measuring the area of a fracture opening with a certain degree of precision from a two dimensional image can be extremely inaccurate due to the irregular shape of the image. In recent years several techniques have been developed, or improved, that may allow a better and more accurate quantification of image features observed in metallographic analyses in incipient damage of fracture surfaces. Many of these measured quantities are essential towards developing a solid, robust understanding necessary for a good constitutive model.