Marc A. Meyers

Bio: Marc A. Meyers is an academic researcher from University of California, San Diego. The author has contributed to research in topics: Deformation (engineering) & Dislocation. The author has an hindex of 85, co-authored 487 publications receiving 36646 citations. Previous affiliations of Marc A. Meyers include University of California & Instituto Militar de Engenharia.

Defect Substructures in Plate Impacted and Laser Shocked Monocrystalline Copper

Abstract: Monocrystalline copper samples with orientations of [001] and [221] were shocked at pressures ranging from 20 GPa to 60 GPa using two techniques: direct drive lasers and explosively driven flyer plates. The pulse duration for these techniques differed substantially: 40 ns for the laser experiments at 0.5 mm into the sample and 1.1 ∼1.4 μs for the flyer‐plate experiments at 5 mm into the sample. The residual microstructures were dependent on orientation, pressure, and shocking method. For the flyer‐plate experiments, the longer pulse duration allow shock‐generated defects to reorganize into lower energy configurations. Calculations show that the post shock cooling for laser shock is 103 ∼ 104 faster than that of the plate‐impact shock, propitiating recovery and recrystallization conditions for the latter. At the higher pressure level extensive recrystallization was observed in the plate‐impact samples. An effect to contribute significantly to the recrystallization is the existence of micro‐shearbands, which increase the local temperature.

Laser Shock Compression and Spalling of Reactive Ni-Al Laminate Composites

Abstract: Reactive laminates produced by successive rolling and consisting of alternate layers of Ni and Al (with bi‐layer thicknesses of 5 and 30 μm) were investigated by subjecting them to laser shock‐wave loading. The laser intensity was varied between ∼2.68×1011 W/cm2 (providing an initial estimated pressure P∼25 GPa) and ∼1.28×1013 W/cm2 (P∼333 GPa) with two distinct initial pulse durations: 3 ns and 8 ns. Hydrodynamic calculations (using commercial code HYADES) were conducted to simulate the behavior of shock‐wave propagation in the laminate structures. SEM, and XRD were carried out on the samples to study the reaction initiation, and the intermetallic compounds. It was found that the thinner bilayer thickness (5 μm) laminate exhibited the most intensive localized interfacial reaction at the higher laser intensity (1.28×1013 W/cm2); the reaction products were identified as NiAl and other Al‐rich intermetallic compounds. The reaction front and the formation of intermetallic compounds extend into the sample wit...

Shear localization in granular and comminuted alumina

Abstract: Granular alumina with two different particle sizes and densified to 85% of the theoretical value was subjected to deformation in compression by means of the radial collapse of a thick-walled cylinder. Fully dense alumina that had been pre-comminuted in a separate event was subjected to same process. The overall strains were in the 0.2–0.4 range, and the strain rate was on the order of 104 s−1. Profuse shear localization was observed, which is interpreted in terms of hardening and softening mechanisms in the granular material. The structure of the bands for the two particle sizes (0.4 and 4 μm) was quite different, but the band thicknesses were approximately equal (10–20 μm). The comminuted alumina exhibited narrower bands (2–10 μm) developed by crack bridging.

JMRT in ISI Web of Science

Abstract: We are elated to announce that JMRT has been approved by Science Citation Index and that its articles published from 2013 on (volumes 2–6) are already listed in the Web of Science. This approval follows a rigorous process in which the journal was evaluated sequentially; only the leading journals are included. This auspicious news is enhanced by the ISI Impact Factor received for 2016, a most impressive 2.359. This number puts JMRT among the elite materials journals, ahead of many traditional venues known in the community. JMRT is also an open access journal and this enhances the visibility of the contributions. This wonderful trajectory, which started in 2012 with the founding of the journal by Horacídio Leal Barbosa Filho (CEO of the Brazilian Metallurgical, Materials and Mining Association, ABM) and Nelson Guedes de Alcântara (its first Editor-inChief), is a reflection of the dedicated and competent work by our Editors, Area Editors and Advisory Board. A special appreciation is due to Mirian Chakkour Nunes, who was involved with the journal all the way from its inception. JMRT is now the highest-ranking Latin-America-originated materials journal and is a truly global venue, with over 50% of the articles from the US, Europe and Asia. We stated in the 2013 editorial entitled ‘Global Science and Technology: Past, Present and Future,’ which marking JMRT’s founding (2013, vol. 2, p. 1): The proud tradition of Materials Science in Brazil is well served by this new journal. As Brazil emerges as a leading global nation, the necessity for a journal of global reach was clear. This initial goal has been reached and we feel that our mission is accomplished. The Brazilian Company of Metallurgy and Mining, CBMM, and the ABM have played a pivotal and visionary role by supporting the journal since its inception. Many challenges lie ahead but this transformative moment reinforces the role of Brazil as an emerging country with a splendid materials tradition and future.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Using Multivariate Statistics

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Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Strength and breaking mechanism of multiwalled carbon nanotubes under tensile load

Abstract: The tensile strengths of individual multiwalled carbon nanotubes (MWCNTs) were measured with a “nanostressing stage” located within a scanning electron microscope. The tensile-loading experiment was prepared and observed entirely within the microscope and was recorded on video. The MWCNTs broke in the outermost layer (“sword-in-sheath” failure), and the tensile strength of this layer ranged from 11 to 63 gigapascals for the set of 19 MWCNTs that were loaded. Analysis of the stress-strain curves for individual MWCNTs indicated that the Young's modulus E of the outermost layer varied from 270 to 950 gigapascals. Transmission electron microscopic examination of the broken nanotube fragments revealed a variety of structures, such as a nanotube ribbon, a wave pattern, and partial radial collapse.