A study of the stretch-induced softening behavior of particle filled elastomers/

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (leaf 61).Elastomers are able to undergo relatively large deformations in an elastic manner, which makes them the material of choice for a wide range of applications. In some cases, filler particles, such as carbon black, are added to the elastomer to alter the mechanical behavior when subjected to different loading conditions. When subjected to cyclic loading conditions, elastomers undergo stress-induced softening, known as the Mullins effect, and this softening behavior is influenced by the amount of filler particle present. The softening is considered to be an evolution of the soft and hard domain microstructure of the material, with the effective soft domain increasing with stretch. In this study, finite element analysis will be used to understand the softening behavior of particle reinforced elastomers. The softening behavior of the parent elastomer will be modeled using a constitutive model proposed by Qi and Boyce (2004). Nonlinear finite element analysis using the ABAQUS code was used to model elastomers with various volume fractions of filler particles, and the stress-strain behavior of the composite and evolution of the soft domain within the matrix is computed. The addition of filler particles was found to increase the overall stiffness of the elastomer, but also to increase the stretch-induced softening, and to alter the distribution of soft domains within the material. The presence of occluded regions of matrix material was also found to have a significant effect on softening behavior.by Andrea Greb.S.B

Motor Qualification for Long-Duration Mars Missions

Qualification of motors for deep space under extreme thermal environments to be encountered during the Mars Science Laboratory (MSL) mission is required to verify the reliability and validate mission assurance requirements. The motor assembly must survive all ground operations, plus the nominal 670 Martian-day (or sol) mission that includes summer and winter seasons of the Mars environment. The motor assembly was tested and characterized under extreme temperature conditions with reference to hardware requirements. The motor assembly has been proved to be remarkably robust and displayed no sign of degradation due to the 3 X (three times per JPL design principles) thermal environmental exposure to the punishing Mars surface operations cycles. The motor characteristics obtained before, during, and post-test comparisons for the surface operations cycles are within measurement error of one another. The motors withstood/survived 2,010 extreme temperature cycles with a Delta T of 190 C deep temperature cycles, representing three times the expected thermal cycling exposure during the MSL surface operations. The qualification test hardware elements (A200 motor assembly, encoders, and resolver) have not shown any signs of degradation due to the PQV (Package Qualification and Verification) testing. The test hardware has demonstrated sufficient life to survive the deep thermal cycles associated with MSL mission surface operations for three lives

Facies heterogeneity and source potential of carbonate-mudstone-dominated distal ramp deposits, Agrio Formation, Neuquén Basin, Argentina

The carbonate-mudstone-dominated Lower Cretaceous Agrio Formation is the youngest marine source rock of the hydrocarbon-prolific Neuquen Basin in Argentina, yet its facies variability and unconventional ´ hydrocarbon potential remains relatively understudied. Detailed studies of mudstone facies variability in thick, carbonate mudstone successions deposited largely below storm wave base (i.e., chalk–marl, black shale, limestone), like the Agrio Formation, are rare and instead commonly focus on biostratigraphy or organic geochemistry alone. A continuous northern section of the Agrio Formation and a southern composite section of the lower Pilmatué and middle Avilé members, totaling ~ 1,200 m of outcrop, were measured. From these measured sections, programmed pyrolysis (n = 339 samples), X-ray diffraction (XRD; n = 69), and thin sections (n = 69) were used to develop a high-resolution integrated macrofacies and microfacies scheme. The four most volumetrically abundant facies include detrital-quartz-silt-bearing fine mudstone (facies 1), radiolarian-bearing calcareous fine mudstone (facies 2), detrital-quartz-silt- and shell-bearing calcareous fine mudstone (facies 3), and calcareous wackestone (facies 4). All four facies are volumetrically dominated by carbonate mud matrix (i.e., micrite) that represents either 1) original pelagic coccolithophore deposition modified by diagenesis, 2) transported carbonate mud (i.e., bottom currents like contour currents or sediment gravity flows), or 3) a combination of both. Outcrop observations, XRD mineralogic trends, and petrographic variations in grain composition between detrital quartz silt, radiolarian and microfossil to macrofossil content (mainly benthic foraminifera and bivalves) distinguish the four mudstone facies. The facies scheme indicates distinctly more heterogeneous and current-influenced sedimentation in the downdip sub-storm wave base than previously described in the Agrio and in carbonate-dominated basinal settings in general. A depositional model is proposed for further testing that may prove valuable towards re-evaluating basinal carbonate mudstone successions worldwide. Utilizing TOC, S2, and HI value cutoffs, this study defines five discrete stratigraphic packages in the Agrio Formation that have the highest source potential, collectively totaling ~ 140 m thick. The novel integration of macrofacies and microfacies analysis, stratigraphy, and a geochemical analysis allow both depositional insights and the assessment of a potential source rock. The study adds to a growing body of literature on 1) carbonate ramp (or slope) to basinal processes and 2) facies models for organic-rich, carbonate-dominated mudstone successions that are unconventional hydrocarbon systems.Fil: Moore, Shawn A.. State University Of Utah. Energy Of Geoscience Institute; Estados UnidosFil: Birgenheier, Lauren P.. State University Of Utah. Energy Of Geoscience Institute; Estados UnidosFil: Greb, Matthias D.. State University Of Utah. Energy Of Geoscience Institute; Estados UnidosFil: Minisini, Daniel. Shell Exploration and Production; Estados Unidos. Shell Houston Technology Center; Estados UnidosFil: Tunik, Maisa Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Omarini Fernández, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentin

25 Signatures

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