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 J02: Spall Nucleation IIRecordings Available
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Chair: Paul Specht, Sandia National Laboratories Room: Anaheim Marriott Platinum 6 |
Tuesday, July 12, 2022 11:00AM - 11:15AM |
J02.00001: Analysis of Spall Damage Mechanisms in LPBF SS316L with Manufactured Porosity Katie D Koube, Kevin Lamb, Taylor Sloop, Joshua Kacher, Suresh Babu, Gregory B Kennedy, Naresh N Thadhani The spall and alternative strain accommodation mechanisms associated with shock compression of Stainless Steel 316L (SS316L) fabricated with intentional porosity using Laser Powder Bed Fabrication (LBPF) will be described in this presentation. 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, 3, and 5 vol.% of the printed material. For each selected pore volume and size, one sample backed with PDV probes was used to capture free surface velocity profiles, while a second similar 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 was used to determine the role of porosity on spall initiation and strain accommodation. Effects of porosity on shock and elastic wave transit time, and locally altered spall failure response due to presence of powder-filled pores were clearly observed through analysis of velocity risetime, pull-back and recompression signatures captured by the PDV profiles. |
Tuesday, July 12, 2022 11:15AM - 11:30AM |
J02.00002: Dynamic Behavior of Repaired metals using Electron Beam Additive Manufacturing Saryu J Fensin, David R Jones, Daniel Martinez, George T Gray, Samantha Lawrence, Amber N Black It is well-known that additive manufacturing alters the microstructure of materials and can lead to varying damage morphologies in spall recovery experiments. While there have been many works to investigate the dynamic response of components/coupons metals that are manufactured completely using additive manufacturing, there are almost no studies to investigate the dynamic response of a hybrid component/coupon built using traditional techniques and repaired using additive manufacturing. In this work, indents of different depths were systematically manufactured on the surface of wrought 316L SS plate. These defects were then repaired using 304L SS wire with the electron beam additive manufacturing technique and subjected to spall recovery experiments. The results highlight minor changes in the spall strength but a larger effect of the repaired region on the overall damage morphology. |
Tuesday, July 12, 2022 11:30AM - 11:45AM |
J02.00003: Mitigating Spall Fracture of Ductile Materials by Introducing Porosity Edwin Chiu, Shmuel Osovski, Alan Needleman, Ankit Srivastava A material when subjected to shock/impact loading conditions can undergo spall fracture, when the compressive waves reflect off interfaces and free surfaces as tensile waves. Experiments have shown that in ductile materials, spall fracture is induced by the growth of pre-existing pores and/or nucleation and growth of new pores. However, porosity in ductile materials also introduces plastic compressibility that may lead to energy absorption and thus mitigate spall fracture. Following this, we investigate the role of initial porosity and nucleation of new pores on the spall fracture of porous ductile materials subjected to flyer plate impact loading conditions using finite element analysis. Our results show that porosity in ductile materials under certain circumstances can indeed mitigate spall fracture by attenuating stress waves. In this presentation we will focus on the results correlating impact velocity, initial porosity, and nucleation of new pores on the propensity of spall fracture of ductile materials. |
Tuesday, July 12, 2022 11:45AM - 12:00PM |
J02.00004: Spall Failure of Additively Manufactured Two-Layered Cu-Ni Bimetallic Alloys Andrew Boddorff, Sungwoo Jang, Gregory B Kennedy, Karen M Taminger, Naresh N Thadhani The dynamic tensile spall failure of additively manufactured (AM) two-layered bimetallic GRCop-84 – Inconel® 625 alloys, with planar and slanted interfaces is investigated using uniaxial-strain plate-impact gas gun experiments. Multiple Photon Doppler Velocimetry (PDV) are used to monitor the back (free) surface velocity profiles and to determine the influence of the interface geometry on the spall failure. Micrographs of cross-sections of recovered impacted samples reveal failure along the interface as well as in-material regions. Spall strengths determined from pull-back signals captured with the use of the multiple PDV probes illustrate different location-specific values for the same sample, corresponding to failure occurring in Inconel® 625, or GRCop-84, or along their interface, depending on the geometry of the interface. The results obtained from the experiments employing multiple PDV probes correlated with microstructural observations of cross-sections of recovered impacted samples, provide a useful method for determining the complex spall failure response of two-layered bimetallic alloys, including the differentiation of the response of the respective alloy materials relative to that of the interface, in the same experiment. |
Tuesday, July 12, 2022 12:00PM - 12:15PM |
J02.00005: Dynamic Mechanical Testing of Nanoporous Gold Using a Shock-Tube Bulge Test Jasdeep Singh, Hooman Rahmani, UmairBin B Asim, Sean P Cooper, Eric L Petersen, Ankit Srivastava, Michael J Demkowicz We investigate the behavior of two nanopourous gold (NPG) thin films with different ligament diameters under dynamic bulge testing to understand the effect of ligament diameter on strength. NPG films were prepared by electrochemical dealloying of the surface of a white gold membrane followed by annealing to modify ligament diameters. Bulge tests were carried out using a shock tube, which generates a uniform pressure with a 1ms rise time, causing the thin film to deflect outwards. The NPG film with larger ligament diameter delaminates on the pressure-facing side of the membrane, whereas the film with smaller ligaments remains attached to the membrane. Finite element analysis (FEA) shows that, in addition to deforming in biaxial strain, the membrane also exhibits a transient tensile stress in the direction normal to the membrane surface. We propose that this stress is responsible for the observed delamination and infer that NPG with larger ligaments is weaker under dynamic tensile loading than the NPG with smaller ligaments. Our analysis permits us to estimate an upper bound for the strength of the large ligament NPG sample and a lower bound for the small ligament sample. We compare these findings to the ligament size-dependent mechanical behavior of NPG under quasistatic loading. |
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