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 P05: Damage and Spall IFocus Recordings Available
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Chair: Vasant Joshi, NSWC Crane Room: Anaheim Marriott Platinum 3 |
Wednesday, July 13, 2022 11:00AM - 11:30AM |
P05.00001: Role of Microstructure in the High Strain Rate Shear Response of 316L SS Invited Speaker: Veronica Anghel Shear localization is characterized by the concentration of plastic deformation within narrow bands of material and constitutes the precursor to failure in materials subjected to high strain rates. These bands have been observed experimentally but classical continuum material models have not been able to capture their development. The ability to predict this material response mechanism and accurately represent the associated deformation modes in numerical simulations is a significant undertaking from both the application and numerical method development perspectives. The aim of this research is to investigate the role of microstructure in the dynamic shear response of 316L SS, looking at natural sources of perturbation in material response such as grain structure and dislocation densities. For that purpose, CFSS-DIC samples of wrought and additively manufactured 316L SS were tested on a Split Hopkinson Pressure Bar in conjunction with in-situ high-speed infrared thermometry measurements at different strains and strain rates. The shear response of 316L SS will be discussed taking into consideration differences in starting microstructure between the wrought and additively manufactured 316L SS. Microstructure characterization and temperature measurements provided important input for the calibration of a thermodynamically-consistent dynamic recrystallization model and shed light on the energy distribution in the material during deformation, which is key for successfully modeling shear deformation. |
Wednesday, July 13, 2022 11:30AM - 11:45AM |
P05.00002: Dynamic Indentation of Fatigue Samples Christopher H Braithwaite, David M Williamson, Pietro Villa, Valerio Carollo Understanding the effect of damage on fatigue life of aerospace components is of significant industrial and economic importance. This damage can often occur through dynamic loading. This paper looks at methods for producing controlled levels of dynamic damage in specimens that are subsequently able to be used for fatigue tests. It discusses many of the difficulties that arise in trying to achieve this using a Hopkinson Bar set-up including wave reflections, impedance mismatches and eliminating multiple impacts and bending of samples. The repeatability of the damage is demonstrated, along with methods for characterisation though 3D optical microscopy techniques. |
Wednesday, July 13, 2022 11:45AM - 12:00PM |
P05.00003: Observation of shear band localization in Ti-64 through in-situ imaging under dynamic compression conditions Jonathan Lind, Matthew Nelms, Mukul Kumar, Nathan R Barton Severe deformation of materials can lead to inhomogeneous intense zones of localized strain, typically called shear bands, serving as the precursor to failure. It has been observed in the past that Ti-64 readily shear bands under dynamic compression conditions. We performed a series of plate-impact hole closure experiments with in-situ X-ray radiography imaging to visualize the inhomogeneous response. Observed regions of sharp discontinuity indicate formation of shear banding. The addition of a low-density filler material in the hole produces a more homogeneous closure response indicating inhibition of shear banding. Fully intact samples were recovered, and a series of post-mortem characterizations is performed with results discussed. |
Wednesday, July 13, 2022 12:00PM - 12:15PM |
P05.00004: The Effect of Second-Phase Fraction on the Spall Properties of Ferrite-Pearlite Steels Virginia K Euser, Daniel Martinez, James Valdez, Carl P Trujillo, Carl Cady, David R Jones, Saryu J Fensin 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. |
Wednesday, July 13, 2022 12:15PM - 12:30PM |
P05.00005: Shear localization in pore collapse as a damage mechanism under shock compression Zev Lovinger, Roman Kositski In this work, we explore the role of porosity under shock compression, to drive damage or failure in the loaded material. Shear localization, resulting from pore collapse is suggested and studied as the damage mechanism. Ti-6Al-4V specimens, with cylindrical and spherical pores were manufactured using additive manufacturing (AM). The specimens were loaded by plate impact using a gas gun, and a soft catch set-up enabled their post-mortem analysis. Under plate impact experiments conducted at shock pressures of 3-8 GPa, the 1-2 mm voids demonstrated collapse and the evolution of shear bands (SB), emanating from the void surface. Varying the impact velocity and corresponding impact pressures, different states of SB evolution were studied. Specimens with multiple pores allowed also to examine the interaction of localization between adjacent pores, creating extended states of joint damage. Numerical simulations were used to reproduce the measured phenomena, and extent the discussion to real micro-meter sized pores at elevated pressures. |
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