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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.


Papers
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Book ChapterDOI
01 Jan 2008
TL;DR: In this article, the degradation undergone by materials in these extreme conditions can be classified into two groups: Mechanical degradation and Chemical degradation, which is due to the reaction of the material with the chemical environment and to the diffusion of external elements into the materials.
Abstract: Introduction The technological developments wrought since the early twentieth century have required materials that resist higher and higher temperatures. Applications of these developments lie mainly in the following areas: Gas turbines (stationary and on aircraft), whose blades operate at temperatures of 800–950 K. The burner and afterburner sections operate at even higher temperatures, viz. 1,300–1,400 K. Nuclear reactors, where pressure vessels and piping operate at 650–750 K. Reactor skirts operate at 850–950 K. Chemical and petrochemical industries. All of these temperatures are in the range (0.4–0.65) T m , where T m is the melting point of the material in kelvin. The degradation undergone by materials in these extreme conditions can be classified into two groups: Mechanical degradation . In spite of initially resisting the applied loads, the material undergoes anelastic deformation; its dimensions change with time. Chemical degradation . This is due to the reaction of the material with the chemical environment and to the diffusion of external elements into the materials. Chlorination (which affects the properties of superalloys used in jet turbines) and internal oxidation are examples of chemical degradation. This chapter deals exclusively with mechanical degradation. The time-dependent deformation of a material is known as creep . A great number of high-temperature failures can be attributed either to creep or to a combination of creep and fatigue. Creep is characterized by a slow flow of the material, which behaves as if it were viscous.

7 citations

Journal ArticleDOI
TL;DR: In this article, a detailed microstructural analysis and evaluation of the mechanical properties of titanium aluminides consolidated by novel shock processes is presented, and the fracture modes are correlated with the micro-structural observations.
Abstract: A detailed microstructural analysis and evaluation of the mechanical properties of titanium aluminides consolidated by novel shock processes[13] are presented. Successful consolidation was obtained and was evidenced by strong bonding between individual particles. Additions of Nb and Ti and Al elemental powders resulted in enhanced interparticle bonding through intense plastic deformation of Nb and shock-induced reactions between Ti and Al. Rapid cooling of interparticle molten layers yielded amorphous Ti-Al alloys; this interparticle melting and rapid cooling are a unique feature of shock processing. Embrittlement of individual particles of Ti3Al-based alloy after exposure to 550 °C and 750 °C was observed. There is evidence of phase transformation after preheating the powder, and this fact can explain the high density of cracks obtained with this alloy after high-temperature shock consolidation. Mechanical properties of the Ti3Al-based alloy were determined at room temperature and the fracture modes were studied. The microstructural observations are correlated with the mechanical properties.

7 citations

Journal ArticleDOI
TL;DR: Varied amounts of Ti, Al, and V were detected in the tested groups proving that diffusion of these metals from Ti-6Al-4V orthodontic mini-implants exists.
Abstract: Ti-6Al-4V orthodontic mini-implants may release metallic ions to the human body due to the in vivo corrosion of the alloy in body fluids. The corrosion products can elicit undesirable effects in the human body. The purpose of this study was to measure the concentration of titanium, aluminum, and vanadium in rabbits’ tissues (kidney, liver and lungs) after the insertion of Ti-6Al-4V alloy orthodontic mini-implants. Eighteen New Zealand rabbits had four mini-implants inserted in their left tibia and five rabbits were used as control. After 1, 4, and 12 weeks the rabbits were euthanized, the selected tissues were extracted, and prepared to analysis by graphite furnace atomic absorption spectrometry. Varied amounts of Ti, Al, and V were detected in the tested groups proving that diffusion of these metals from Ti-6Al-4V orthodontic mini-implants exists. Despite of the tendency of ion release when using the titanium alloy, the amount of metals detected were very low. Then, Ti-6Al-4V orthodontic mini-implants are safe auxiliary orthodontic anchorage devices.

7 citations

Journal ArticleDOI
TL;DR: In this article, several rapidly solidified Al-Li-based alloy powders were successfully consolidated into crack-free compacts by explosively generated shock waves, and the microstructures of the compacts were evaluated by optical and electron microscopy.
Abstract: Several rapidly solidified AlLi-based alloy powders were successfully consolidated into crack-free compacts by explosively generated shock waves. Both flyer plate and direct contact techniques were applied in cylindrical and plate configurations. Densities of the compacted powders reach over 97% of their theoretical values. The microstructures of the compacts were evaluated by optical and electron microscopy. Crack-free compacts were produced by using the flyer tube technique in the cylindrical separated by random stacking faults or several atomic layers of f.c.c. structure. A high density of hot-extruded alloys. Compacts of Al3wt.%Li1wt.%Cu1wt.%Mg0.2wt.%Zr alloy powders exhibited the highest tensile strength (282 MPa). The optical micrographs showed that the crack-free compacts had considerable interparticle melting. The interparticle melting regions were analyzed by X-ray diffraction and transmission electron microscopy and had a microcrystalline structure with precipitates of δ′-Al 3 Li and δ-AlLi. Fractographs of tensile specimens revealed that the compacts having high tensile strength had strong interparticle bonding; their rupture surface exhibited transparticle fracture.

6 citations

Book ChapterDOI
01 Jan 2008
TL;DR: In this article, a simplified treatment of elasticity is presented, in a manner so as to treat problems in an undergraduate course, and a graphical method for the solution of two-dimensional stress problems (the Mohr circle) is described.
Abstract: Introduction Elasticity deals with elastic stresses and strains, their relationship, and the external forces that cause them. An elastic strain is defined as a strain that disappears instantaneously once the forces that cause it are removed. The theory of elasticity for Hookean solids – in which stress is proportional to strain – is rather complex in its more rigorous treatment. However, it is essential to the understanding of micro- and macromechanical problems. Examples of the former are stress fields around dislocations, incompatibilities of stresses at the interface between grains, and dislocation interactions in work hardening; examples of the latter are the stresses developed in drawing, and rolling wire, and the analysis of specimen–machine interactions in testing for tensile strength. This chapter is structured in such a way as to satisfy the needs of both the undergraduate and the graduate student. A simplified treatment of elasticity is presented, in a manner so as to treat problems in an undergraduate course. Stresses and strains are calculated for a few simplified cases; the tridimensional treatment is kept at a minimum. A graphical method for the solution of two-dimensional stress problems (the Mohr circle) is described. On the other hand, the graduate student needs more powerful tools to handle problems that are somewhat more involved. In most cases, the stress and strain systems in tridimensional bodies can be better treated as tensors, with the indicial notation.

6 citations


Cited by
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01 May 1993
TL;DR: 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.
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.

29,323 citations

01 Jan 2016
TL;DR: The using multivariate statistics is universally compatible with any devices to read, allowing you to get the most less latency time to download any of the authors' books like this one.
Abstract: Thank you for downloading using multivariate statistics. As you may know, people have look hundreds times for their favorite novels like this using multivariate statistics, but end up in infectious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they juggled with some harmful bugs inside their laptop. using multivariate statistics is available in our digital library an online access to it is set as public so you can download it instantly. Our books collection saves in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Merely said, the using multivariate statistics is universally compatible with any devices to read.

14,604 citations

Journal ArticleDOI
01 Apr 1988-Nature
TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
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

9,929 citations

Journal ArticleDOI
28 Jan 2000-Science
TL;DR: The tensile strengths of individual multiwalled carbon nanotubes (MWCNTs) were measured with a "nanostressing stage" located within a scanning electron microscope and a variety of structures were revealed, such as a nanotube ribbon, a wave pattern, and partial radial collapse.
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.

5,011 citations