High-Rate Crystal/Polycrystal Dislocation Dynamics

• Published in: Crystals (Basel) Vol. 12; no. 5; p. 705
• Main Author: Armstrong, Ronald W.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 16.05.2022
• Subjects: constitutive equation predictions; Crystal dislocations; dislocation mechanics parameters; Experiments; Mechanics; Mechanics (physics); Parameter sensitivity; Polycrystals; Sensitivity analysis; Shear strain; Shear tests; Shock loading; shock waves in plate impact and gas-gun impact measurements; shock-front dislocation model generations; Split Hopkinson pressure bars; split-Hopkinson pressure bar measurements; Strain hardening; Strain rate sensitivity; strain rate sensitivity parameters; Tantalum; Thermal stress; Yield strength
• DOI: 10.3390/cryst12050705
• ISSN: 2073-4352

The present report builds upon work recently published on crystal and polycrystal dislocation mechanics behaviors assessed, in part, in split-Hopkinson pressure bar (SHPB) and shock loading investigations. A connection between the flow stress dependencies on strain rate in the different tests had been established in the previous report, whereas additional results are assessed here for (1) relationship of the measurements to a nano-scale prismatic dislocation structure proposed to be generated at a propagating shock front and (2) further relationships between the modeled structure and corresponding thermal stress and strain rate sensitivity computations, including new evaluations of the engineering rate sensitivity parameter, m = [∆lnσ/∆ln(dε/dt)]T. A comparison is made of m values approaching 1.0 for simulated dislocation mechanics results computed for tantalum crystals. Other (lower) m value comparisons involve recently determined higher shock stress measurements made on copper material at higher temperatures.