Three-Dimensional Characterization and Modeling of Microstructural Weak Links for Spall Damage in FCC Metals
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Local microstructural weak links for spall damage were investigated using three-dimensional (3-D) characterization in multicrystalline copper samples (grain size ≈ 450 µm) shocked with laser-driven plates at low pressures (2 to 4 GPa). The thickness of samples and flyer plates, approximately 1000 and 500 µm respectively, led to short pressure pulses that allowed isolating microstructure effects on local damage characteristics. Electron Backscattering Diffraction and optical microscopy were used to relate the presence, size, and shape of porosity to local microstructure. The experiments were complemented with 3-D finite element simulations of individual grain boundaries (GBs) that resulted in large damage volumes using crystal plasticity coupled with a void nucleation and growth model. Results from analysis of these damage sites show that the presence of a GB-affected zone, where strain concentration occurs next to a GB, correlates strongly with damage localization at these sites, most likely due to the inability of maintaining strain compatibility across these interfaces, with additional effects due to the inclination of the GB with respect to the shock. Results indicate that strain compatibility plays an important role on intergranular spall damage in metallic materials.
KeywordsCrystal Plasticity Resolve Shear Stress Void Nucleation Damage Site Void Volume Fraction
This work was funded by LANL under the Laboratory Directed Research and Development (LDRD) program, award # 20060021DR, and by the Department of Energy, National Nuclear Security Administration (NNSA), under Grants # DE-FG52-06NA26169, DE-FG52-10NA29653, and DE-NA0002005. Eric Loomis, Pat Dickerson (LANL), Damian Swift (LLNL), David Wright, Karl Weiss, and Dallas Kingsbury (ASU) are thanked for their help during research work. Access to TRIDENT and the Electron Microscopy Lab at LANL, and the Center for High Resolution Electron Microscopy at ASU is gratefully acknowledged.
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