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 T05: Strength IIIRecordings Available
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Chair: Hye-Sook Park, Lawrence Livermore Natl Lab Room: Anaheim Marriott Platinum 3 |
Thursday, July 14, 2022 9:15AM - 9:30AM |
T05.00001: Dynamic strength characterization of phase transformed iron using pressure shear plate impact experiments Vatsa B Gandhi, Suraj Ravindran, Guruswami Ravichandran Understanding plasticity behavior of iron in its high pressure ε-phase is important to develop accurate models for hypervelocity impacts and to understand deformation mechanisms of planetary cores. Additionally, martensitic phase transformations, of iron and its alloys, provide a unique opportunity to study strength behavior as they play a crucial role in enhanced material properties and expand the material design space for various load-bearing applications. In this study, we investigate the pressure dependent dynamic strength behavior of both the ambient α-phase and high pressure ε-phase of iron at strain-rates of 105 s-1 and pressures to 42 GPa. High pressure - pressure shear plate impact experiments are conducted using a sandwich configuration to decouple the effect of pressure and shear thereby allowing us to probe strength once the sample reaches an equilibrated state of stress. We report the strength of ε-iron to be more than double the strength of α-iron potentially due to microstructural evolution during phase transition. Additionally, we present the evolution of yield strength with pressure, temperature, and strain for the first time, enabling more accurate modeling of extreme deformation phenomena associated with iron-rich celestial bodies such as planetary collisions. |
Thursday, July 14, 2022 9:30AM - 9:45AM |
T05.00002: Experimental investigation and modelling of mechanical strength and damage evolution of fully martensitic wrought and Additive Manufactured Ti6Al4V-grade 5 Gianluca Iannitti, Vittorio Di Cocco, Mirko Sgambetterra, Sara Ricci In this work the experimental investigation and constitutive modelling of wrought and additively manufactured Ti6Al4V (TI64), both having a similar microstructure predominantly consisting of acicular martensitic (α′) phase, are presented. |
Thursday, July 14, 2022 9:45AM - 10:00AM |
T05.00003: Influence of additive manufacturing process on the impact strength of Ti-6Al-4V Gabriel Testa, Nicola Bonora, Andrew Ruggiero, Gianluca Iannitti Understanding the role of process-related defects on material strength is of critical importance for developing safe and affordable acceptance criteria for additively manufactured components. Testing at high strain rates can reveal much more about the effect of defects on the fracture resistance of the material. In this work, material response and ductility of wrought and additive manufactured Ti-6Al-4V, fabricated by selective laser melting (SLM) and sintering (SLS), under uniaxial and multiaxial stress state, were characterized at low and high strain rates. Taylor cylinder impact tests were performed to determine the velocity at onset damage development. Despite small differences in the uniaxial response, results show that SLS and SLM fractured at impact velocity 60% and 20% lower than that of wrought. Microscopy investigation revealed that the presence of voids reduces the shear resistance anticipating the formation of shear bands. |
Thursday, July 14, 2022 10:00AM - 10:15AM |
T05.00004: Shock response of cobalt-based tungsten carbide cermet Bingsen Wang, Vikas Prakash Cemented tungsten carbides are metal matrix composites in which a large fraction of hard tungsten carbide (WC) grains are embedded in a soft transition metal matrix, e.g., cobalt, nickel, iron, etc., commonly referred to as the binder. Because of their high density and hardness, these composites have been particularly attractive in applications where high-rate mechanical loading, high hardness, and high wear resistance is important. In the present study, shock wave experiments are conducted to better understand the structure of shock waves and their associated thermodynamic states in shock-compressed cemented WC with 3 wt. percent Co binder. The peak shocked state of interest to this study is up to 90 GPa, which is more than ten times the Hugoniot Elastic Limit reported for WC ceramics in the literature. The measured wave profiles indicate the cermet to undergo elastic-plastic deformation during its shock compression. A three-stage particle velocity profile is observed in the experiments -- an initial elastic-rise to the (HEL), an elastic-plastic ramp indicating substantial post-yield hardening, and finally a rise to the peak shocked Hugoniot state. Besides calculation of in-material quantities in the elastic-limit and the peak shocked Hugoniot states, Hugoniot relations for the WC sample in terms of the shock velocity vs. particle velocity and longitudinal stress vs specific volume are determined over the stress range of interest. The results indicate the WC cermet samples to preserve substantial shear strength in the post-yield deformation regime up to 90 GPa. No phase transformation was observed up to 90 GPa. |
Thursday, July 14, 2022 10:15AM - 10:30AM |
T05.00005: Imaging Defects in Diamond during Shock Compression Cara Vennari, Dimitri Khaghani, Eric Folsom, Kento Katagiri, Arturas Vailionis, Chris McGuire, Raymond F Smith, Richard Briggs, Bernard Kozioziemski, Leora E Dresselhaus-Marais, Jon H Eggert Diamond is well established to have strong resistance to plastic deformation and it’s Hugoniot Elastic Limit (HEL) is large relative to other materials. The HEL of single crystal diamond has orientation dependance: diamonds shocked in the <100> and <110> directions have been shown to have higher HEL than the <111> direction. Grain size of and impurities in diamond are thought to affect the HEL. Additionally, when diamond is shocked to stresses beyond the HEL, its strength drops (like a brittle material). To investigate the wide range of reported diamonds strength, we conduct X-ray topography experiments during laser shock loading at the MEC beamline at LCLS. X-ray topography is a near field imaging technique that images defects by observing contrast in the intensity of the diffracted X-ray beam. By using a line focused X-ray beam coupled with a thick diffracting region, we generate 2D images where defect derived intracrystalline rotations generate a diffraction intensity contrast compared to the defect free regions. We shock <100>, <110> and <111> oriented diamonds that are type Ia, Ib and IIa over a range of stresses to view dislocation avalanches in order to visualize the physics behind the onset of plasticity. |
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