The Experts below are selected from a list of 1935 Experts worldwide ranked by ideXlab platform
George J Simitses - One of the best experts on this subject based on the ideXlab platform.
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Theory of Cylindrical Sandwich Shells with Dissimilar Facings Subjected to Thermomechanical Loads
AIAA Journal, 2000Co-Authors: Victor Birman, George J SimitsesAbstract:Atheory is outlined of sandwich box-typecomposite shells designed to withstand a combination ofthermalloading,internalpressure,torsionalandaxialLoads.Acrosssectionoftheshellrepresentsa rectangularboxwithcurved cylindrical sections at the corners. The facings of the shell are dissimilar to maximize their efe ciency, according to the Loads acting on each facing. This approach enables a designer to optimize the structure by maximizing the load-carrying capacity or minimizing the weight. The formulation includes the following developments: 1 ) global theory of a sandwich shell composed ofrectangular and cylindrical sections, where equationsof motion are formulated based on a e rst-order shear deformable version of Sanders’ s shell theory; 2 ) theory for local deformations and stresses in the facings, where the facing is treated as a thin geometrically nonlinear plate or shell on an elastic foundation using von K´
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elastoviscoplastic snap through behavior of shallow arches subjected to Thermomechanical Loads
Finite Elements in Analysis and Design, 1991Co-Authors: George J Simitses, Yuzhao Song, Izhak SheinmanAbstract:Abstract The problem of snap-through buckling of clamped shallow arches under Thermomechanical Loads is investigated. The analysis is based on nonlinear kinematic relations and nonlinear rate-dependent unified constitutive equations. A finite element approach is employed to predict the, in general, inelastic buckling behavior. The construction material is alloy B1900+Hf, which is commonly utilized in high-temperature environments. The effect of several parameters is assessed. These parameters include the rise parameter and temperature. Comparison between elastic and elastoviscoplastic responses is also presented.
Michael Spottswood - One of the best experts on this subject based on the ideXlab platform.
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a lower bound on snap through instability of curved beams under Thermomechanical Loads
International Journal of Non-linear Mechanics, 2012Co-Authors: Ilinca Stanciulescu, Toby J Mitchell, Yenny Chandra, Thomas Eason, Michael SpottswoodAbstract:Abstract A non-linear finite element formulation (three dimensional continuum elements) is implemented and used for modeling dynamic snap-through in beams with initial curvature. We identify a non-trivial (non-flat) configuration of the beam at a critical temperature value below which the beam will no longer experience snap-through under any magnitude of applied quasi-static load for beams with various curvatures. The critical temperature is shown to successfully eliminate snap-through in dynamic simulations at quasistatic loading rates . Thermomechanical coupling is included in order to model a physically minimal amount of damping in the system, and the resulting post-snap vibrations are shown to be thermoelastically damped. We propose a test to determine the critical snap-free temperature for members of general geometry and loading pattern; the analogy between mechanical prestress and thermal strain that holds between the static and dynamic simulations is used to suggest a simple method for reducing the vulnerability of thin-walled structural members to dynamic snap-through in members of large initial curvature via the introduction of initial pretension.
S I Kundalwal - One of the best experts on this subject based on the ideXlab platform.
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Interfacial characteristics of hybrid nanocomposite under Thermomechanical loading
Journal of the mechanical behavior of materials, 2017Co-Authors: Vijay Choyal, S I KundalwalAbstract:AbstractIn this work, an improved shear lag model was developed to investigate the interfacial characteristics of three-phase hybrid nanocomposite which is reinforced with microscale fibers augmented with carbon nanotubes on their circumferential surfaces. The shear lag model accounts for (i) radial and axial deformations of different transversely isotropic constituents, (ii) Thermomechanical Loads on the representative volume element (RVE), and (iii) staggering effect of adjacent RVEs. The results from the current newly developed shear lag model are validated with the finite element simulations and found to be in good agreement. This study reveals that the reduction in the maximum value of the axial stress in the fiber and the interfacial shear stress along its length become more pronounced in the presence of applied Thermomechanical Loads on the staggered RVEs. The existence of shear tractions along the RVE length plays a significant role in the interfacial characteristics and cannot be ignored.
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Multiscale modeling of Thermomechanical behaviour of three-phase nanocomposite
arXiv: Materials Science, 2016Co-Authors: S I Kundalwal, Shaker A. MeguidAbstract:In this work, we developed an improved shear lag model to investigate the load transfer characteristics of three-phase nanocomposite which is reinforced with microscale fibers augmented with carbon nanotubes on their circumferential surfaces. The shear lag model accounts for (i) radial and axial deformations of different transversely isotropic constituents, (ii) Thermomechanical Loads on the representative volume element (RVE), and (iii) staggering effect of adjacent RVEs. The results from the current newly developed shear lag model are validated with the finite element simulations and found to be in good agreement. Our study reveals that the reduction in the maximum value of the axial stress in the fiber and the interfacial shear stress along its length become more pronounced in the presence of applied Thermomechanical Loads on the staggered RVEs. The existence of shear tractions along the RVE length plays a significant role in the load transfer characteristics and cannot be ignored.
V Novak - One of the best experts on this subject based on the ideXlab platform.
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on the r phase transformation related phenomena in niti polycrystals subjected to Thermomechanical Loads
Journal De Physique Iv, 2004Co-Authors: P Sittner, D Lugovyy, D Neov, Michal Landa, P Lukas, V NovakAbstract:Results of in-situ neutron diffraction studies of the B2↔R transformation and R-phase reorientation processes in thermal, mechanical and Thermomechanical Loads on NiTi alloy polycrystals are presented. It is discussed how the crystallographic features and structure instability of R-phase affects the macroscopic Thermomechanical σ - e - T response of NiTi when the R-phase is involved.
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anisotropy of martensitic transformations in modeling of shape memory alloy polycrystals
International Journal of Plasticity, 2000Co-Authors: P Sittner, V NovakAbstract:Based on the knowledge of the anisotropy associated with the martensitic transformations obtained from tension/compression experiments with oriented CuAlNi single crystals, a simple constant stress averaging approach is employed to model the SMA polycrystal deformation behaviors. Only elastic and inelastic strains due to the martensitic transformation, variant reorientations in the martensite phase and martensite to martensite transformations in Thermomechanical Loads are considered. The model starts from theoretical calculation of the stress-temperature transformation conditions and their orientation dependence from basic crystallographic and material attributes of the martensitic transformations. Results of the simulations of the NiTi, NiAl, and Cu-based SMA polycrystals in stress–strain tests are shown. It follows that SMA polycrystals, even with randomly oriented grains, typically exhibit tension/compression asymmetry of the shape of the pseudoelastic σ−e curves in transformation strain, transformation stress, hysteresis widths, character of the pseudoelastic flow and in the slope of temperature dependence of the transformation stresses. It is concluded that some macroscopic features of the SMA polycrystal behaviors originate directly from the crystallography of the undergoing MT's. The model shows clearly the crystallographic origin of these phenomena by providing a link from the crystallographic and material attributes of martensitic transformations towards the macroscopic σ−e−T behaviors of SMA polycrystals.
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anisotropy of cu based shape memory alloys in tension compression Thermomechanical Loads
Journal of Engineering Materials and Technology-transactions of The Asme, 1999Co-Authors: P Sittner, V NovakAbstract:Tension/compression Thermomechanical experiments were performed on oriented CuAlNi shape memory alloy single crystals and CuAlZnMn single and polycrystals. Response of the single crystals in Thermomechanical Loads was strongly anisotropic, dependent on the orientation of the load axis and sense of the load. Tension/compression stress-temperature diagrams were constructed from experimentally determined transformation stresses and temperatures. It was shown that the history dependent strain response of the single crystal in a complex tension/compression Thermomechanical cycle could be predicted from the diagram. Thermomechanical behaviors of the CuAlZnMn polycrystal under tension/compression were reported and discussed on the basis of the knowledge of the single crystal anisotropy.
Izhak Sheinman - One of the best experts on this subject based on the ideXlab platform.
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elastoviscoplastic snap through behavior of shallow arches subjected to Thermomechanical Loads
Finite Elements in Analysis and Design, 1991Co-Authors: George J Simitses, Yuzhao Song, Izhak SheinmanAbstract:Abstract The problem of snap-through buckling of clamped shallow arches under Thermomechanical Loads is investigated. The analysis is based on nonlinear kinematic relations and nonlinear rate-dependent unified constitutive equations. A finite element approach is employed to predict the, in general, inelastic buckling behavior. The construction material is alloy B1900+Hf, which is commonly utilized in high-temperature environments. The effect of several parameters is assessed. These parameters include the rise parameter and temperature. Comparison between elastic and elastoviscoplastic responses is also presented.