In this article, we computed the spall strength of polyurethane samples by following two methods:
(1) The indirect method (from the free surface velocity history, which is commonly used in experiments)
(2) A direct method (from the atomic stresses in the spall region, which is possible only in MD)
The results reveal that the tensile strength computed from the indirect method is consistently smaller than the value obtained from the direct method. Moreover, the strength computed from the indirect method shows an excellent agreement with the fracture nucleation stress.
The MD model we used in this paper is available here