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The purpose of this study is to quantify the influence of textural and microstructural anisotropy on spallation. This includes the influence of anisotropically-oriented MnS inclusion stringers in the HY-100 and 1080 steels on spallation, within two crystallographically-isotropic steels, and the influence of strong, anisotropic crystallographic texture in high-purity polycrystalline Ta and Zr materials to assess the role of texture on damage evolution and spallation responses. The effect of anisotropic crystallographic texture on the spallation response of Ta and Zr is shown to play a minimal role in the spallation response of each material, as seen in wave profile pull-back signals, compared to the effect of texture on the shock arrival time and the Hugoniot elastic limit that reflects strength in these two high-purity materials. In the case of both the 1080 and HY-100 steels, the influence of elongated MnS stringers, resident within the essentially crystallographically isotropic steels, was found to be dominated by the heterogeneous nucleation of damage orthogonal to the MnS stringers. Delamination between the pearlitic matrix microstructure and the MnS stringers in the 1080 steel, or inclusions and the martensitic matrix in the HY-100 steel, was seen to correlate to a lower pull-back signal during transverse loading than to that parallel to the stringer axis in each steel. [ABSTRACT FROM AUTHOR]

We present a series of experiments on the response of additive manufactured (AM) tantalum to dynamic loading, specifically the spall strength. Rectangular plates of AM tantalum were produced, with subsequent characterization revealing a highly anisotropic microstructure. Samples were taken from these plates to investigate the effect of anisotropy on the spall strength: the resistance to high strain-rate tensile damage. A conventional, wrought tantalum sample, possessing an equiaxed microstructure, was also tested to serve as a control. Shock loading was performed via light gas-gun flyer-plate impact experiments, with laser velocimetry on the rear of the samples to record the shock wave profiles and soft-recovery techniques to allow post-mortem analysis. In general, the AM samples were found to have a higher Hugoniot elastic limit, the dynamic yield strength under shock loading, while having a reduced spall strength, when compared to the wrought tantalum samples. [ABSTRACT FROM AUTHOR]

For ductile metals, dynamic fracture occurs principally through void nucleation, growth, and coalescence at heterogeneities in the microstructure. Previous experimental research on high purity metals has shown that microstructural features, such as grain boundaries, inclusions, vacancies, and heterogeneities, can act as initial void nucleation sites. In addition, other research on two-phase materials has also highlighted the importance of the properties of a second phase itself in determining the dynamic response of the overall material. However, previous research has not investigated the effects of the distribution of a second phase on damage nucleation and evolution. To approach this problem in a systematic manner, two copper alloys with 1% lead materials, with the same Pb concentration but different Pb distributions, have been investigated. A new CuPb alloy was cast with a more homogeneous distribution of Pb as compared to a CuPb where the Pb congregated in large "stringer" type configurations. These materials were shock loaded at ~1.2 GPa and soft recovered. In-situ free surface velocity information, and post mortem metallography, reveals that even though the spall strength of both the materials were similar, the total extent and details of damage in the materials varied by 15%. This suggests that altering the distribution of Pb in the Cu matrix leads to the creation of more void nucleation sites and also changed the rate of void growth. [ABSTRACT FROM AUTHOR]

Previous experimental research has shown that microstructural features such as interfaces, inclusions, vacancies, and heterogeneities can all act as void nucleation sites. However, it is not well understood how important these interfaces are to damage evolution and failure as a function of the surrounding parent materials. In this work, we present results on three different polycrystalline materials: (1) Cu, (2) Cu-24 wt. %Ag, and (3) Cu-15 wt.%Nb which were studied to probe the influence of bi-metal interfaces on void nucleation and growth. These materials were chosen due to the range of difference in structure and bulk properties between the two phases. The initial results suggest that when there are significant differences between the bulk properties (for example: stacking fault energy, melting temperature, etc.) the type of interface between the two parent materials does not principally control the damage nucleation and growth process. Rather, it is the "weaker" material that dictates the dynamic spall strength of the overall two-phase material. [ABSTRACT FROM AUTHOR]