Heterogeneous deformation and spall of an extruded tungsten alloy: plate impact experiments and crystal plasticity modeling

Abstract

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The effect of shockwave profile shape on dynamic brittle failure

“…These spall strength values are consistent with the majority of values reported in the literature review in the introduction. It is worth noting that the difference between the two specimens is less than the sample-to-sample scatter generally reported for WHA and is consistent with the statistical variation within a given sample reported by Vogler and Clayton [14], therefore being statistically insignificant for this brittle material. Moreover, this difference is an order of magnitude less than reported for the spall strength dependence on wave profile observed in ductile metals.…”

“…As discussed by Vogler and Clayton [14], the stress levels calculated are below the ideal tensile strength (∼30 GPa) of a perfect tungsten lattice [23], but microscopic flaws within the W grains or along their edges may enable cleavage under the present loading conditions, particularly along {1 0 0} and {1 1 0} planes known to be preferred orientations for grain cleavage [24]. Such flaws may be created during processing or during the initial shock loading of the material.…”

“…The compite displays improved ductility under compression and tension in comparison to that of pure polycrystalline tungsten. The shock response based on plate impact square-wave loading has been extensively reported in the literature for pure polycrystalline tungsten [5][6][7][8] and tungsten heavy alloys [9][10][11][12][13][14].…”

“…Dandekar and Weisgerber [11] reported the spall strength and Hugoniot elastic limit (HEL) of WHA to be 1.7-2.0 GPa and 2.8 GPa, respectively for plate impact. Vogler and Clayton [14] employed line-VISAR to spatially resolve statistics on the spall strength of WHA based on plate impact, fitting their measurements to both normal and Weibull distributions. Across five WHA samples with different material processing and sample orientation, the average spall strength within a given sample varied from 1.66 to 2.13 GPa with standard deviations from 0.31 to 0.61 GPa.…”

“…Bless reported the spall strength for WHA to be 2.6 GPa but did not observe an HEL. Vogler and Clayton [14] reported that higher velocity impacts produce EPJ Web of Conferences a higher spall strength, suggesting that the regions where failure occurs (e.g., W-matrix interfaces and W-W grain boundaries) are preconditioned to a more durable state by the initial compressive pulse. Dandekar also showed some variation of spall strength with impact velocity for WHA [11], as well as in other brittle materials [15].…”