The Experts below are selected from a list of 2478 Experts worldwide ranked by ideXlab platform

L Schachter - One of the best experts on this subject based on the ideXlab platform.

  • analytic method for evaluation of the field of a charge traversing a Geometric Discontinuity
    Applied Physics Letters, 2002
    Co-Authors: Samer Banna, L Schachter
    Abstract:

    An analytic time-domain method is developed for the electromagnetic field generated by a charge traversing a Geometric Discontinuity. The essence of the method employed here is to use the linear independence of the exponential functions, that control the temporal behavior of the field. As a result, we avoid the large (“infinite”) matrix inversion necessary for a frequency-domain solution. This method was utilized for the investigation of the wake generated by electrons in an optical accelerator as well as evaluation of the emittance growth and energy spread.

R E Rowlands - One of the best experts on this subject based on the ideXlab platform.

  • smoothing finite element and experimental hybrid technique for stress analyzing composites
    Computers & Structures, 1991
    Co-Authors: Z Feng, R E Rowlands
    Abstract:

    Abstract A smooth two-dimensional numerical technique is presented for representing and differencing discrete moire data. The concept extends a previous approach to enable simultaneous processing of both in-plane measured displacements and thereby obtain smooth displacement functions and continuous strains full-field. A cluster of positive definite functionals is formulated and minimized to best approximate the experimental data. This variational problem is solved by a finite-element method. Arbitrarily shaped regions can be fitted with relatively few elements, neither boundary displacements nor their derivatives need to be specified, and experimental data locations may occur in any configuration. Little experimental input data are needed, and the inherent smoothing reduces the effects of experimental scatter. The technique is particularly effective for determining shear strains, and/or strains along a curved line such as the edge of a Geometric Discontinuity. The method is demonstrated by the moire strain analysis of a tensile composite plate containing a hole.

Roham Rafiee - One of the best experts on this subject based on the ideXlab platform.

  • fracture investigation of wood under mixed mode i ii loading based on the maximum shear stress criterion
    Strength of Materials, 2013
    Co-Authors: Mahdi Fakoor, Roham Rafiee
    Abstract:

    The main objective of this article is to present a new fracture criterion for predicting both crack growth initiation and crack propagation direction in wood specimens under mixed mode I/II loading. This criterion is based on distribution of the maximum shear stress in the crack tip vicinity. An accurate estimation of the damage zone effect in wood is the main advantage of this criterion in comparison with available ones. The variation compliance of damaged material due to growth of microcracks is considered by a suitable damage factor. This criterion is extended for specimens with arbitrarily oriented cracks with respect to the orthotropic axes. It is revealed that developed approach is more compatible with the nature of the fracture phenomena in wood. The superiority of proposed method has been shown by some verification cases for several available fracture test data. Introduction. Wood is a natural orthotropic material which is broadly used in civil and construction fields. Different factors like easy accessibility, high ratio of mass to strength, remarkable durability and performance, absorbing and dissipating of vibrations under some conditions of use and also good insulating properties of dry wood against heat, sound and electricity of wood made it a good candidate for structural elements in construction (1). But the most important parameter which plays a key role in growing demand for the application of wood is its availability in many species, sizes and shapes. Moreover, the simple manufacturing process of wood from renewable sources is another factor encouraging industry to employ it. Efficient and safe design of timber structures necessitates the proper understanding of behavior of wood fracture which is a complicated issue attributed to the inherent variability, heterogeneity and anisotropy of wood. Wood elements are either most likely to experience damages during service, or contain Geometric Discontinuity. Subjected to the mixed mode I and II of loading, intrinsic damages in wood are identified as cracks with various sizes (2). The mechanism of wood fracture can be hardly distinguished with linear elastic fracture mechanics (LEFM) principles due to the damage zone around the crack tip and development of microcracks in the crack tip vicinity resulted in wood specimens' fracture (3). Almost all proposed criteria for fracture investigations of wood specimens under mixed mode I/II loading are developed for the specimens with initial notches along the wood fibers. The complicated mechanism of wood fracture has hindered different researchers from studying this phenomenon theoretically and limited most studies to curve fitting of the experimental data (4, 5). Recently, Jernkvist (6) tried to develop a criterion for wood structures under mixed mode I/II loading by extending the well-known isotropic fracture criteria, namely the maximum strain energy release rate (7) and the minimum strain energy density criteria (8). The obtained results are conservative and are not in agreement with experimental data (9). This inconsistency is originated from neglecting the wasted energy caused by microcrack formation and their growth in fracture process zone. Therefore, the theoretical investigations of wood fracture require a robust and general criterion especially for mixed mode fracture. The main objective of this article is to develop a general criterion to study mixed mode fracture

  • fracture investigation of wood under mixed mode i ii loading based on the maximum shear stress criterion
    Strength of Materials, 2013
    Co-Authors: Mahdi Fakoor, Roham Rafiee
    Abstract:

    The main objective of this article is to present a new fracture criterion for predicting both crack growth initiation and crack propagation direction in wood specimens under mixed mode I/II loading. This criterion is based on distribution of the maximum shear stress in the crack tip vicinity. An accurate estimation of the damage zone effect in wood is the main advantage of this criterion in comparison with available ones. The variation compliance of damaged material due to growth of microcracks is considered by a suitable damage factor. This criterion is extended for specimens with arbitrarily oriented cracks with respect to the orthotropic axes. It is revealed that developed approach is more compatible with the nature of the fracture phenomena in wood. The superiority of proposed method has been shown by some verification cases for several available fracture test data. Introduction. Wood is a natural orthotropic material which is broadly used in civil and construction fields. Different factors like easy accessibility, high ratio of mass to strength, remarkable durability and performance, absorbing and dissipating of vibrations under some conditions of use and also good insulating properties of dry wood against heat, sound and electricity of wood made it a good candidate for structural elements in construction (1). But the most important parameter which plays a key role in growing demand for the application of wood is its availability in many species, sizes and shapes. Moreover, the simple manufacturing process of wood from renewable sources is another factor encouraging industry to employ it. Efficient and safe design of timber structures necessitates the proper understanding of behavior of wood fracture which is a complicated issue attributed to the inherent variability, heterogeneity and anisotropy of wood. Wood elements are either most likely to experience damages during service, or contain Geometric Discontinuity. Subjected to the mixed mode I and II of loading, intrinsic damages in wood are identified as cracks with various sizes (2). The mechanism of wood fracture can be hardly distinguished with linear elastic fracture mechanics (LEFM) principles due to the damage zone around the crack tip and development of microcracks in the crack tip vicinity resulted in wood specimens' fracture (3). Almost all proposed criteria for fracture investigations of wood specimens under mixed mode I/II loading are developed for the specimens with initial notches along the wood fibers. The complicated mechanism of wood fracture has hindered different researchers from studying this phenomenon theoretically and limited most studies to curve fitting of the experimental data (4, 5). Recently, Jernkvist (6) tried to develop a criterion for wood structures under mixed mode I/II loading by extending the well-known isotropic fracture criteria, namely the maximum strain energy release rate (7) and the minimum strain energy density criteria (8). The obtained results are conservative and are not in agreement with experimental data (9). This inconsistency is originated from neglecting the wasted energy caused by microcrack formation and their growth in fracture process zone. Therefore, the theoretical investigations of wood fracture require a robust and general criterion especially for mixed mode fracture. The main objective of this article is to develop a general criterion to study mixed mode fracture

Fathy Abdelmoniem Abdelfattah - One of the best experts on this subject based on the ideXlab platform.

  • fatigue strength of steel plate girders with notched dapped end
    International Review of Civil Engineering, 2019
    Co-Authors: Fathy Abdelmoniem Abdelfattah
    Abstract:

    This study examines numerically the stress concentrations and the fatigue strength of steel plate girders with notched ends. The Geometric Discontinuity of the notch gives rise to the stress concentrations in the web plate and makes it vulnerable to the formation of fatigue cracks under cyclic loading. The finite element analysis and the hot spot stress method have been employed. The implemented approach has been verified against experimental results in literature. The effects of using notched end have been studied considering the girder strength, the failure mode, the deflection and the cross section distortion. Two areas of stress concentrations and three hot spots have been detected. The dimensions of the notch details have been found to have significant effects on the magnitude of stress concentrations and fatigue strength. For future works, the obtained conclusions provide guidance for the design of notched ends details in steel plate girders against fatigue and they can be considered as a basis for design standards. For already existing girders, a strengthening method has been proposed against fatigue. This study applies as far as no out of plane deformation and/or buckling occurred in the web plate.

Sundararajan Natarajan - One of the best experts on this subject based on the ideXlab platform.

  • stress diffusion interactions in an elastoplastic medium in the presence of Geometric Discontinuity
    Mechanics of Advanced Materials and Structures, 2020
    Co-Authors: Rupesh Kumar Mahendran, Sundararajan Natarajan
    Abstract:

    This paper aims to study the effect of stress-diffusion interactions and its effect on the localization of the plastic strain in an elastoplastic material using a fully coupled chemo-mechanical sys...

  • continuum modelling of stress diffusion interactions in an elastoplastic medium in the presence of Geometric Discontinuity
    arXiv: Computational Engineering Finance and Science, 2020
    Co-Authors: Rupesh Kumar Mahendran, Ratna Kumar Annabattula, Sundararajan Natarajan
    Abstract:

    Chemo-mechanical coupled systems have been a subject of interest for many decades now. Previous attempts to solve such models have mainly focused on elastic materials without taking into account the plastic deformation beyond yield, thus causing inaccuracies in failure calculations. This paper aims to study the effect of stress-diffusion interactions in an elastoplastic material using a coupled chemo-mechanical system. The induced stress is dependent on the local concentration in a one way coupled system, and vice versa in a two way coupled system. The time-dependent transient coupled system is solved using a finite element formulation in an open-source finite element solver FEniCS. This paper attempts to computationally study the interaction of deformation and diffusion and its effect on the localization of plastic strain. We investigate the role of Geometric discontinuities in scenarios involving diffusing species, namely, a plate with a notch/hole/void and particle with a void/hole/core. We also study the effect of stress concentrations and plastic yielding on the diffusion-deformation. The developed code can be from this https URL