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Record 37 of 11192
Explicit 3D continuum fracture modeling with smooth particle hydrodynamics
Author and Affiliation:
Benz, W.(Arizona Univ., Tucson, AZ, United States)
Asphaug, E.(Arizona Univ., Tucson, AZ, United States)
Abstract: Impact phenomena shaped our solar system. As usual for most solar system processes, the scales are far different than we can address directly in the laboratory. Impact velocities are often much higher than we can achieve, sizes are often vastly larger, and most impacts take place in an environment where the only gravitational force is the mutual pull of the impactors. The Smooth Particle Hydrodynamics (SPH) technique has been applied in the past to the simulations of giant impacts. In these simulations, the colliding objects were so massive (at least a sizeable fraction of the Earth's mass) that material strength was negligible compared to gravity. This assumption can no longer be made when the bodies are much smaller. To this end, we have developed a 3D SPH code that includes a strength model to which we have added a von Mises yielding relation for stresses beyond the Hugoniot Elastic Limit. At the lower stresses associated with brittle failure, we use a rate-dependent strength based on the nucleation of incipient flaws whose number density is given by a Weibull distribution. Following Grady and Kipp and Melosh et al., we introduce a state variable D ('damage'), 0 less than D less than 1, which expresses the local reduction in strength due to crack growth under tensile loading. Unfortunately for the hydrodynamics, Grady and Kipp's model predicts which fragments are the most probable ones and not the ones that are really formed. This means, for example, that if a given laboratory experiment is modeled, the fragment distribution obtained from the Grady-Kipp theory would be equivalent to a ensemble average over many realizations of the experiment. On the other hand, the hydrodynamics itself is explicit and evolves not an ensemble average but very specific fragments. Hence, there is a clear incompatibility with the deterministic nature of the hydrodynamics equations and the statistical approach of the Grady-Kipp dynamical fracture model. We remedy these shortcomings by making the incipient flaw distribution explicit, i.e., particles carry activation strains which are distributed at random with a probability of occurrence given by the Weibull distribution. If the local principal axis strain exceeds this limit, damage starts to grow. By growing explicit cracks together with statistical cracks (damage) at the sub-particle scale, we ensure that material strength and fragmentation is independent of model resolution. We tested our scheme by simulating laboratory impact experiments on basalt spheres.
Publication Date: Jan 01, 1993
Document ID:
19940007590
(Acquired Dec 28, 1995)
Accession Number: 94N12062
Subject Category: ASTROPHYSICS
Coverage: Abstract Only
Document Type: Conference Paper
Publication Information: Lunar and Planetary Inst., Twenty-fourth Lunar and Planetary Science Conference. Part 1: A-F; p 99-100
Publisher Information: United States
Financial Sponsor: NASA; United States
Organization Source: Arizona Univ.; Observatory and Lunar Planetary Lab.; Tucson, AZ, United States
Description: 2p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright
NASA Terms: CONTINUUM MODELING; FRACTURE MECHANICS; HYDRODYNAMICS; HYPERVELOCITY IMPACT; METEORITE COLLISIONS; GRAVITATIONAL EFFECTS; IMPACT TESTS; MATHEMATICAL MODELS; SCALE EFFECT; SIMULATION; SOLAR SYSTEM
Imprint And Other Notes: In Lunar and Planetary Inst., Twenty-fourth Lunar and Planetary Science Conference. Part 1: A-F p 99-100 (SEE N94-12015 01-91)
Availability Source: Other Sources
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