The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform

A. Loghman - One of the best experts on this subject based on the ideXlab platform.

  • Non-stationary electro-thermo-Mechanical Creep response and smart deformation control of thick-walled sphere made of polyvinylidene fluoride
    Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2016
    Co-Authors: A. Loghman, H. Tourang
    Abstract:

    This paper describes an analytical–numerical model developed for non-stationary electro-thermo-Mechanical Creep response of a smart sphere made of polyvinylidene fluoride (PVDF) using Burgers’ Creep model. The piezoelectric properties of the PVDF are used to control Creep deformation of the sphere. Time-dependent stresses, displacements, electric potential and strains are calculated using Mendelson’s method of successive approximation. The vessel is subjected to internal and external pressures, distributed temperature fields and an applied electric potential. Two loading combinations have been considered in this study. All Mechanical, thermal and piezoelectric properties are selected from the experimental data existed in the literature. All Creep parameters for Burgers’ model are functions of time, temperature and stress. Their functional relationship is obtained using a nonlinear regression. Therefore, this study is a nonlinear time-dependent analysis. Total strains are assumed to be the sum of elastic, thermal, electrical and Creep strains. Creep strains are time, temperature and stress dependent. Using the equations of equilibrium, compatibility, Maxwell’s equation for free electric charge and stress–strain relations, a differential equation, containing Creep strains, for spherical vessel is obtained. A new semi-analytical solution has been developed to find displacement, stresses, strains and electric potential in terms of time-dependent Creep strains. Creep strain rates are related to the Burgers’ Creep model and current stresses with the Prandtl–Reuss relations. Using Mendelson’s method of successive approximation, the histories of electric potential, radial, circumferential and effective stresses and strains are calculated. It has been found that by applying a suitable electric potential deformation of the sphere can be controlled.

  • Effect of particle content, size and temperature on magneto-thermo-Mechanical Creep behavior of composite cylinders
    Journal of Mechanical Science and Technology, 2013
    Co-Authors: A. Loghman, A. Askari Kashan, M. Younesi Bidgoli, A. R. Shajari, A. Ghorbanpour Arani
    Abstract:

    The effects of particle content, particle size, operating temperature and magnetic field on steady-state Creep behavior of thick-walled rotating cylinders made of Al-SiC composites have been investigated. Loading is composed of a uniform magnetic field in axial direction, steady-state heat conduction in radial direction and an inertia body force due to rotation. The composite Creep constitutive equation has been described by Norton’s law in which the Creep parameters are functions of particle size, temperature and particle content. The composite properties are radial dependent based on volume fraction of SiC reinforcement. It has been found that the minimum effective Creep strain rate belongs to a composite identified by 25% SiC at the inner and 5% at the outer surfaces. Therefore this composite has been selected for the design of the cylinder. It has been concluded that increasing particle size and operating temperature significantly increases the effective Creep strain rates. It has also been illustrated that magnetic field decreases the stresses and the effective Creep strain rates.

  • semi analytical solution of time dependent electro thermo Mechanical Creep for radially polarized piezoelectric cylinder
    Computers & Structures, 2011
    Co-Authors: Ghorbanpour A Arani, Reza Kolahchi, A.a. Mosallaie Barzoki, M R Mozdianfard, A. Loghman
    Abstract:

    History of strains, stresses, deformations and electric potentials of hollow cylinders made from PZT_5 have been investigated using successive elastic solution method. A differential equation containing Creep strains for displacement is obtained. Since Creep strains are time, temperature and stress dependent, the closed form solution cannot be found for this constitutive differential equation. Hence, a semi-analytical method is proposed. Electric potentials increase with time (similar to the radial stress histories), since it is induced by the radial stress histories during Creep deformation of the cylinder, justifying industrial application of such a material as efficient actuators and sensors.

Pavel Kudinov - One of the best experts on this subject based on the ideXlab platform.

  • Assessment with Coupled Thermo-Mechanical Creep Analysis of Combined CRGT and External Vessel Cooling Efficiency for a BWR
    2020
    Co-Authors: Walter Villanueva, Chi Thanh Tran, Pavel Kudinov
    Abstract:

    Assessment with Coupled Thermo-Mechanical Creep Analysis of Combined CRGT and External Vessel Cooling Efficiency for a BWR

  • coupled thermo Mechanical Creep analysis for boiling water reactor pressure vessel lower head
    Nuclear Engineering and Design, 2012
    Co-Authors: Walter Villanueva, Chi Thanh Tran, Pavel Kudinov
    Abstract:

    In this paper we consider a hypothetical severe accident in a Nordic-type boiling water reactor (BWR) at the stage of relocation of molten core materials to the lower head and subsequent debris bed ...

  • coupled thermo Mechanical Creep analysis for boiling water reactor pressure vessel lower head
    8th International Topical Meeting on Nuclear Thermal-Hydraulics Operation and Safety (NUTHOS-8) Shanghai China October 10-14, 2010
    Co-Authors: Walter Villanueva, Chi Thanh Tran, Pavel Kudinov
    Abstract:

    a b s t r a c t In this paper we consider a hypothetical severe accident in a Nordic-type boiling water reactor (BWR) at the stage of relocation of molten core materials to the lower head and subsequent debris bed and then melt pool formation. Nordic BWRs rely on reactor cavity flooding as a means for ex-vessel melt coolability and ultimate termination of the accident progression. However, different modes of vessel failure may result in different regimes of melt release from the vessel, which determine initial conditions for melt coolant interaction and eventually coolability of the debris bed. The goal of this study is to define if retention of decay-heated melt inside the reactor pressure vessel is possible and investigate modes of the vessel wall failure otherwise. The mode of failure is contingent upon the ultimate Mechanical strength of the vessel structures under given Mechanical and thermal loads and applied cooling measures. The influence of pool depth and respective transient thermal loads on the reactor vessel failure mode is studied with coupled thermo-Mechanical Creep analysis. Efficacy of control rod guide tube (CRGT) cooling and external vessel wall cooling as potential severe accident management measures is investigated. First, only CRGT cooling is considered in simulations revealing two different modes of vessel failure: (i) a ‘ballooning’ of the vessel bottom and (ii) a ‘localized Creep’ concentrated within the vicinity of the top surface of the melt pool. Second, possibility of in-vessel retention with CRGT and external vessel cooling is investigated. We found that the external vessel cooling was able to suppress the Creep and subsequently prevent vessel failure for the considered pool depths.

T Egami - One of the best experts on this subject based on the ideXlab platform.

  • Mechanical rejuvenation in bulk metallic glass induced by thermo Mechanical Creep
    Acta Materialia, 2018
    Co-Authors: Yang Tong, W Dmowski, Yoshihiko Yokoyama, T Egami
    Abstract:

    Abstract Using high energy X-ray diffraction we studied the temperature, stress, and time effect on structural changes in a Zr-based bulk metallic glass induced by thermo-Mechanical Creep. Pair distribution functions obtained from two-dimensional diffraction patterns show that thermo-Mechanical Creep induces structural disordering, but only when the stress beyond a threshold is applied. A similar threshold behavior was observed for anelastic strain. We conclude that anelastic Creep strain induces rejuvenation, whereas plastic strain does not.

Walter Villanueva - One of the best experts on this subject based on the ideXlab platform.

  • Assessment with Coupled Thermo-Mechanical Creep Analysis of Combined CRGT and External Vessel Cooling Efficiency for a BWR
    2020
    Co-Authors: Walter Villanueva, Chi Thanh Tran, Pavel Kudinov
    Abstract:

    Assessment with Coupled Thermo-Mechanical Creep Analysis of Combined CRGT and External Vessel Cooling Efficiency for a BWR

  • Coupled Thermo-Mechanical Creep Analysis For A Nordic BWR Lower Head Using Non-Homogeneous Debris Bed Configuration From MELCOR
    2020
    Co-Authors: Peng Yu, Walter Villanueva, Sergey Galushin, Weimin Ma, Sevostian Bechta
    Abstract:

    We present a coupled thermo-Mechanical Creep analysis for a Nordic BWR lower head with a non-homogeneous debris bed configuration generated with MELCOR code. A one-way coupling approach was adopted ...

  • coupled thermo Mechanical Creep analysis for boiling water reactor pressure vessel lower head
    Nuclear Engineering and Design, 2012
    Co-Authors: Walter Villanueva, Chi Thanh Tran, Pavel Kudinov
    Abstract:

    In this paper we consider a hypothetical severe accident in a Nordic-type boiling water reactor (BWR) at the stage of relocation of molten core materials to the lower head and subsequent debris bed ...

  • coupled thermo Mechanical Creep analysis for boiling water reactor pressure vessel lower head
    8th International Topical Meeting on Nuclear Thermal-Hydraulics Operation and Safety (NUTHOS-8) Shanghai China October 10-14, 2010
    Co-Authors: Walter Villanueva, Chi Thanh Tran, Pavel Kudinov
    Abstract:

    a b s t r a c t In this paper we consider a hypothetical severe accident in a Nordic-type boiling water reactor (BWR) at the stage of relocation of molten core materials to the lower head and subsequent debris bed and then melt pool formation. Nordic BWRs rely on reactor cavity flooding as a means for ex-vessel melt coolability and ultimate termination of the accident progression. However, different modes of vessel failure may result in different regimes of melt release from the vessel, which determine initial conditions for melt coolant interaction and eventually coolability of the debris bed. The goal of this study is to define if retention of decay-heated melt inside the reactor pressure vessel is possible and investigate modes of the vessel wall failure otherwise. The mode of failure is contingent upon the ultimate Mechanical strength of the vessel structures under given Mechanical and thermal loads and applied cooling measures. The influence of pool depth and respective transient thermal loads on the reactor vessel failure mode is studied with coupled thermo-Mechanical Creep analysis. Efficacy of control rod guide tube (CRGT) cooling and external vessel wall cooling as potential severe accident management measures is investigated. First, only CRGT cooling is considered in simulations revealing two different modes of vessel failure: (i) a ‘ballooning’ of the vessel bottom and (ii) a ‘localized Creep’ concentrated within the vicinity of the top surface of the melt pool. Second, possibility of in-vessel retention with CRGT and external vessel cooling is investigated. We found that the external vessel cooling was able to suppress the Creep and subsequently prevent vessel failure for the considered pool depths.

Soumya Gupta - One of the best experts on this subject based on the ideXlab platform.

  • ‘Tension Tile System’ (TTS): a simple innovative wound closure device
    European Journal of Plastic Surgery, 2015
    Co-Authors: Sunil Choudhary, Raghav Mantri, Prateek Arora, Rohit Jain, Ovais Habib, Soumya Gupta
    Abstract:

    Wounds closed under severe tension often result in breakdown due to skin necrosis and suture cheese wiring causing both physical and financial morbidity. Although a few commercial wound closure systems have been described in the literature, but they are all expensive and not readily available. We have designed a simple and inexpensive system called ‘Tension Tile System’ (TTS) which utilizes plastic casing found in most sterile surgical suture packs. The device is easy to construct, sterile, inexpensive, easily available, and based on already proven principles of Mechanical Creep and stress relaxation. Large wounds in five patients were closed with the help of TTS system with no complications. We believe that this system will find wide application in all surgical fields where the wound encounters tension during closure. Level of Evidence: Level V, therapeutic study

  • ‘Tension Tile System’ (TTS): a simple innovative wound closure device
    European Journal of Plastic Surgery, 2015
    Co-Authors: Sunil Choudhary, Raghav Mantri, Prateek Arora, Rohit Jain, Ovais Habib, Soumya Gupta
    Abstract:

    Wounds closed under severe tension often result in breakdown due to skin necrosis and suture cheese wiring causing both physical and financial morbidity. Although a few commercial wound closure systems have been described in the literature, but they are all expensive and not readily available. We have designed a simple and inexpensive system called ‘Tension Tile System’ (TTS) which utilizes plastic casing found in most sterile surgical suture packs. The device is easy to construct, sterile, inexpensive, easily available, and based on already proven principles of Mechanical Creep and stress relaxation. Large wounds in five patients were closed with the help of TTS system with no complications. We believe that this system will find wide application in all surgical fields where the wound encounters tension during closure.