IMPACT SIMULATIONS WITH FRACTURE .1. METHOD AND TESTS

We describe a new numerical tool based on the smooth particle hydrodyn amics (SPH) method which is aimed at modeling impacts and collisions i nvolving small solid objects. Our goal is to develop a suitable tool f or the study of strength-dominated interactions between solid bodies. Although giant impacts have recently received most of the attention, c ollisions and/or impacts involving small (less-than-or-equal-to 50 km) objects are (and have been) the most frequent ones. We intend to appl y this model to such studies as the formation of asteroid families, th e disruption of ringmoons, the accretion of planetesimals, and spallat ion from large cratering events. In this first paper in a series, we p resent all physical and numerical aspects of our model as well as a nu mber of tests performed in order to validate our method. We adopt a st rength model and implement a von Mises yielding relation for stresses beyond the Hugoniot elastic limit. At the lower stresses associated wi th brittle failure, we use a rate-dependent strength based on the nucl eation of Weibull flaws. Our model propagates statistical cracks at th e subparticle scale based on the model of Grady and Kipp (1980) and re solves real cracks in a resolution-independent manner. Our method ensu res that increases in resolution do not alter the fracture physics, on ly the accuracy. The resulting system predicts the shapes, locations, and velocities of the largest fragments in simulated laboratory impact events with unprecedented accuracy. (C) 1994 Academic Press, Inc.