超高速撞击下碎片云的 OTM 分析

The hypervelocity impact (HVI) of space debris is a typical extreme mechanics problem at high temperature, high pressure and high strain rate. The HVI involves the complex dynamic response of materials. Numerical methods have become very useful and important tools to predict the complex phenomena and look into the details of the entire process. However, the accurate simulation of the HVI is a grand challenge in scientific computing that places exacting demands on physics models, numerical solvers and computing resources. The optimal transportation meshfree (OTM) method is a meshfree updated-Lagrangian methodology for fluid and solid dynamic flows, possibly involving multiple phases, viscosity and general equations of state, general inelastic and history-dependent constitutive relations, arbitrary variable domains and boundary conditions and the interaction between fluid flows and highly deformable structures. The rationale behind the approach is combining concepts from the optimal transportation (OT) theory with material-point sampling, local maximum entropy (LME) approximation, the seizing contact, variational material point failure algorithm, and overcomes the essential difficulties in grid-based numerical methods like Lagrangian and Eulerian finite element method. Owing to those advantages, the OTM method provides an efficient and accurate solution for HVI simulation. In this paper, large scale three-dimensional numerical simulations on the HVI of the copper projectiles with different thicknesses (3.45, 5.13 mm), different masses (3, 10 g), different impact angles (5.4°, 11.7°) and different impact velocities (5.55, 5.12 km/s) impacting the Al6061-T6 plate with different thicknesses (2.87, 4.39 mm) were performed within the software ESCAAS based on the OTM method using a dynamic load balancing MPI/Pthreads parallel implementation. The dynamic response of material including phase transition in the high strain rate, high pressure and high temperature regime expected in this paper was described by the use of a variational thermomechanical coupling constitutive model with the SESAME equation of state, Grüneisen equation of state, rate-dependent J2 plasticity with power law hardening and thermal softening. The simulation results are in good agreement with the experimental measurements, which indicates the capacity of the OTM method and the ESCAAS software for HVI simulation.