Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session 1G: Advances in Experimental Techniques and Diagnostics (Including SEB)Student Symposium
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Room: Anaheim Marriott Platinum 5-6 |
Sunday, July 10, 2022 1:00PM - 1:15PM |
1G.00001: Analysis of Spall Damage Mechanisms in LPBF SS316L with Manufactured Porosity Katie D Koube This presentation will describe spall and alternative strain accommodation mechanisms present in Stainless Steel 316L (SS316L) fabricated with intentional porosity using Laser Powder Bed Fabrication (LBPF). Spall failure is locally altered through the interaction of powder filled pores with reflected shock waves. LPBF manufactured cylinders were impacted at velocities of 250 m/s in a series of symmetric plate impact experiments. Randomly distributed pores were either 200 350, or 500 microns in size and were present in up to 1, 2, and 5 vol.% of the printed material. For each selected pore volume and size, one instrumented sample backed with PDV probes was used to capture free surface velocity profiles, while a second sample was soft recovered in the catch tank for postmortem microstructure characterization. Electron Backscatter Diffraction (EBSD) in combination with Scanning Electron Microscopy (SEM), and optical microscopy is used to determine the role of porosity on spall initiation and strain accommodation. Effects of porosity on shock and elastic wave arrival time and resulting spall response were clearly observed through slope analysis of velocity profiles. |
Sunday, July 10, 2022 1:15PM - 1:30PM |
1G.00002: The Effect of Second-Phase Fraction on the Spall Properties of Ferrite-Pearlite Steels Virginia K Euser Two ferrite-pearlite steels (1045 and A283) were subjected to spall recovery experiments to reveal the influence of pearlite fraction on spall strength and total damage. The A283 (20 % pearlite) alloy exhibited a higher Hugoniot elastic limit (HEL) and spall strength compared to 1045 (60 % pearlite). Post-mortem characterization of recovered samples revealed cementite lamellae cracking within the pearlite of 1045, suggesting that pearlite reduces spall strength by providing low-energy damage nucleation sites. The rate of damage growth and coalescence, as inferred from free surface velocity histories, was similar between the two alloys. However, 1045 exhibited more continuous cracks compared to a greater prevalence of discrete voids in A283. This work reveals the role of pearlite in the spall behavior of ferrite-pearlite steels, and further elucidates the influence of relatively brittle, second-phase particles on dynamic deformation. |
Sunday, July 10, 2022 1:30PM - 1:45PM |
1G.00003: An analysis of the potential for gravity-induced grading in epoxy interlayers in ceramic armours Daniel Powell Functionally graded materials (FGMs) have great potential in controlling the passage of shock through them and in the distribution of energy through an adhesive interlayer. An adhesive FGM with specific 'grades' to match both the adherend acoustic impedances could prevent the passage of a destructive tensile wave through an armour system, ensuring the ceramic outer layer remains intact and overmatches an incoming projectile for a greater duration prior to failure. However, as FGMs are typically complex and challenging to create, they are often costly and are rarely considered for use in vehicle armours. Gravitational settling of dense powdered particles inside a comparatively viscous epoxy creates an adhesive solution that contains various but predictable quantities of powder at different layers, creating a cheap and controllable FGM. Manipulation of this process through varying powder percentage volumes, alternative materials, powder characteristics and epoxy choices allows for a wide range of FGMs to be created, providing a solution that can be applied to a range of adhesive solutions where shockwaves are a threat. Non-destructive characterisation of the created FGM can be achieved through ultrasonic testing, CT scanning and x-ray radiography. Destructive sectioning of the FGM provides further confidence in the characterisation of the gravitational segregation within the regions with a greater volume of tungsten particles present. Understanding the FGM allows for simulations to be validated, enabling the future rapid determination of the optimum FGM solution with any combination of materials, saving time and money through reducing experimental setups. |
Sunday, July 10, 2022 1:45PM - 2:00PM |
1G.00004: Fragmentation Behavior of Aluminum Powder Swaged Metal Compacts under High Velocity Impact Gary F Simpson The room temperature mechanical swaging of metallic powders to form near fully consolidated, dense alloys, has allowed the synthesis of highly reactive composite metal powder compacts that retain nearly the full strength, toughness, density, and machinability of their bulk parent elements. These compositionally tailorable, swaged metal compacts can serve as structurally sound kinetic projectiles capable of contributing additional chemical energy release. However, the effectiveness of the reaction and subsequent material combustion depends upon the mechanical deformation, failure, and fragmentation of the body during impact. By means of in situ optical visualization of 2 km/s impacts on anvil targets, laser-sheet based fragment tracking, UV/VIS emission spectroscopy, and post-mortem fragment capture and recovery, this work evaluates the potential to control and influence—through input powder size and degree of mechanical swaging—the fragmentation behavior of swaged commercially pure Al projectiles, a well characterized and common material component of metal reactive systems. |
Sunday, July 10, 2022 2:00PM - 2:15PM |
1G.00005: Break II
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