Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session K4: Inelastic Deformations, Fracture and Spall VIII |
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Chair: Vasily Bulatov, Lawrence Livermore National Laboratory Room: Regency Ballroom A |
Tuesday, July 11, 2017 2:15PM - 2:30PM |
K4.00001: Fundamental considerations in dynamic fracture in nuclear materials Carl Cady, David Eastwood, Neil Bourne, Ruizhi Pei, Paul Mummery, Christoph Rau The structural integrity of components used in nuclear power plants is the biggest concern of operators. A diverse range of materials, loading, prior histories and environmental conditions, leads to a complex operating environment. An experimental technique has been developed to characterize brittle materials and using linear elastic fracture mechanics, has given accurate measurements of the fracture toughness of materials. X-ray measurements were used to track the crack front as a function of loading parameters as well as determine the crack surface area as loads increased. This X-ray tomographic study of dynamic fracture in beryllium indicates the onset of damage within the target as load is increased. Similarly, measurements on nuclear graphite were conducted to evaluate the technique. This new, quantitative information obtained using the X-ray techniques has shown application in other materials. These materials exhibited a range of brittle and ductile responses that will test our modelling schemes for fracture. Further visualization of crack front advance and the correlated strain fields that are generated during the experiment for the two distinct deformation processes provide a vital step in validating new multiscale predicative modelling. [Preview Abstract] |
Tuesday, July 11, 2017 2:30PM - 2:45PM |
K4.00002: A study on high rate deformation of additively manufactured lattice structures Hossein Sadeghi, Joseph Abraham, Joseph Magallanes, Dhruv Bhate Due to recent advances in additive manufacturing (AM), parts with complex geometries which were not possible to fabricate through traditional manufacturing techniques, can now be fabricated. Specifically, AM has enabled fabrication of structures with architected lattice structure to design parts with optimized mechanical performance and reduced weight. However, the mechanical performance of parts created by AM under dynamic loads is not well-understood and further studies are needed to characterize such materials at various loading rates. In this study, high rate deformation of stainless steel lattice structures fabricated by AM is studied. Cylindrical samples with internal lattice structure are fabricated by a powder bed fusion system. Hollow cylindrical samples with the same length, outer diameter, and mass but with larger wall thicknesses are also fabricated. Samples are tested under high rate deformation using a split Hopkinson bar equipment. It is observed that the lattice structure exhibits a better performance compared to an equivalent hollow cylinder with a thicker wall but the same length, diameter, and mass. Finite element simulation of the specimen under the dynamic loads are also performed and the results are compared with experimental measurements. [Preview Abstract] |
Tuesday, July 11, 2017 2:45PM - 3:00PM |
K4.00003: Mechanical and Microstructural Investigation of Dual Phase Stainless Steel (LDX2101) under a wide range of strain rates Ali Ameri, Juan Escobedo-Diaz, Mahmud Ashraf, Andrew Brown, Paul Hazell, Wayne Hutchison, Zakaria Quadir The mechanical response and the microstructural evolution of lean duplex stainless steel 2101 (LDSS 2101) under a wide range of strain rates has been investigated. Experimental testing spanned from quasistatic, high strain-rate (Split Hopkinson Pressure Bar) and shock loading. The microstructural changes, e.g. phase transformation and grain rotation, texture and substructure evolution, were investigated by optical microscopy, X-ray diffraction (XRD) and electron-backscattered diffraction (EBSD). A significant increase in the yield stress with increasing strain rate was observed. The plastic deformation, e.g. work hardening rate, was also depended on the strain-rate. The threshold stress for the iron-epsilon phase transformation was obtained from free surface velocity measurements and the retained high pressure phase was assessed by XRD measurements. [Preview Abstract] |
Tuesday, July 11, 2017 3:00PM - 3:15PM |
K4.00004: Experimental implementation of shock waves propagation within multi-materials stacks -- Application to bonded assemblies' evaluation by laser adhesion test Simon Bardy, Emilien Lescoute, Laurent Videau, Bertrand Aubert, David Hebert, Laurent Berthe, Sondes Metoui, Tomas Bergara, Mathieu Ducousso, Romain Ecault, Didier Zagouri The Laser Adhesion Test (LASAT) process is based on propagating calibrated shock waves generated by laser within a multi-material stack to evaluate interface mechanical strength. In this work we present results from laser shocks experiments led recently on various multi-material stacks. Experiments were realized on two different laser-shock facilities in order to study the response of above-mentioned assemblies under 7-40 ns pulses in direct irradiation and water-confined irradiation. Free-Surface Velocity (FSV) monitoring was achieved with Velocity Interferometer System for Any Reflector (VISAR) or Photonic Doppler Velocimetry (PDV) system. Various post-shocks diagnostics such as ultrasonic testing, tomography and micrographs were also employed to give complementary information on debonding or substrates fracturation. The aim of this work is to propose an interpretation of the resulting FSV curves in terms of shock waves propagation, transmission, reflection and eventual fracturing of substrates or epoxy layer. Further discussion should then describe the results of LASAT characterization of these samples, emphasizing the correlation between debonding thresholds and bonding quality. [Preview Abstract] |
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