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This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems. Although we discuss the main points in the application of the finite element method to electromagnetic design, including formulation and implementation, those who seek deeper understanding of the finite element method should consult some of the works listed in the bibliography section.

Introduction to the Finite Element Method

In this study, smart cement with a 0.38 water-to-cement ratio was modified with iron oxide nanoparticles (NanoFe2O3) to have better sensing properties, so that the behavior can be monitored at various stages of construction and during the service life of wells. A series of experiments evaluated the piezoresistive smart cement behavior with and without NanoFe2O3 in order to identify the most reliable sensing properties that can also be relatively easily monitored. Tests were performed on the smart cement from the time of mixing to a hardened state behavior. When oil well cement (Class H) was modified with 0.1% of conductive filler, the piezoresistive behavior of the hardened smart cement was substantially improved without affecting the setting properties of the cement. During the initial setting the electrical resistivity changed with time based on the amount of NanoFe2O3 used to modify the smart oil well cement. A new quantification concept has been developed to characterize the smart cement curing based on electrical resistivity changes in the first 24 h of curing. Addition of 1% NanoFe2O3 increased the compressive strength of the smart cement by 26% and 40% after 1 day and 28 days of curing respectively. The modulus of elasticity of the smart cement increased with the addition of 1% NanoFe2O3 by 29% and 28% after 1 day and 28 days of curing respectively. A nonlinear curing model was used to predict the changes in electrical resistivity with curing time. The piezoresistivity of smart cement with NanoFe2O3 was over 750 times higher than the unmodified cement depending on the curing time and nanoparticle content. Also the nonlinear stress–strain and stress–change in resistivity relationships predicated the experimental results very well. Effects of curing time and NanoFe2O3 content on the model parameters have been quantified using a nonlinear model.

https://iopscience.iop.org/article/10.1088/0964-1726/24/12/125020/pdf

Smart cement modified with iron oxide nanoparticles to enhance the piezoresistive behavior and compressive strength for oil well applications

Vipulanandan models to predict the electrical resistivity, rheological properties and compressive stress-strain behavior of oil well cement modified with silica nanoparticles

The main objective of this campbell systematic review was to provide a systematic review of the evidence on the effects of microcredit on women's control over household spending in developing countries. More specifically, we aimed to answer two related research questions: 1) what does the impact evaluative evidence say about the causal relationship between microcredit and specific dimensions of women's empowerment (women's control over household spending); and 2) what are the mechanisms which mediate this relationship. We prioritise depth of analysis over breadth, thus the scope of this review is narrower than previous systematic reviews on microfinance (stewart et al., 2010; duvendack et al. 2011; stewart et al., 2012). We focused on specific aspects of women's empowerment which allowed us to combine statistical meta-analysis and realist (context-mechanism-outcome) synthesis. From the different searches we identified an initial number of 310 papers that were selected for full text examination. Eventually, 29 papers were retained for further analysis, corresponding to 25 unique studies. In line with three recent other reviews on microfinance (stewart et al., 2010; duvendack et al., 2011; stewart et al. 2012) we found that the microcredit evidence base is extensive, yet most studies are weak methodologically. From those studies deemed comparable and of minimum acceptable quality, we concluded that overall there is no evidence for an effect of microcredit on women's control over household spending.

https://onlinelibrary.wiley.com/doi/pdf/10.4073/csr.2014.8

The Effects of Microcredit on Women's Control over Household Spending in Developing Countries: A Systematic Review and Meta‐analysis

Development of high early-age compressive strength oil well cement is an important task in the oil well cement design. Achievement of suitable early-age compressive strength of oil well cement ensures both the structural support for the casing and hydraulic/mechanical isolation of borehole intervals. Holding this issue in mind, in this research, the effect of pressure and temperature changes inside the borehole on the class G oil well cement compressive strength has been studied. In the proposed work, in contrast to the mostly previous studies which considered some certain temperatures and atmospheric pressure in their tests, the effects of contemporary pressure and temperature changes on the early-age compressive strength of oil well cement have been investigated. Using a non-destructive method, the compressive strength of 48 hours cured cement samples under progressive changing of simultaneously pressures and temperatures coincident to a real oil well data were measured and recorded continuously at predefined intervals during this 48 hours period time. The case study was an oil well located in Darquain region of Khuzestan province in Iran. Obtained results showed that 8 and 12 hours aged samples have a maximum compressive strength in a certain combination of pressure and temperature, 51.7 MPa and 121°C, whereas 24, 45 and 48 hours aged samples have a minimum point in their compressive strength curve at 17.2 MPa and 68°C and a maximum point at 41.4 MPa and 82°C. All the samples show the significant reduce (up to approximately 70%) in compressive strength after the 51.7 MPa and 121°C point. Considering the case study oil well profile of borehole pressure and temperature changes, this tested class G cement is recommended to use in cementing job from ground level down to the almost 4000 m below the surface. (Journal of American Science 2010;6(7):38-47). (ISSN: 1545-1003).

/pdf/early-age-compressive-strength-assessment-of-oil-well-class-1ib1sziyut.pdf

Early-age compressive strength assessment of oil well class G cement due to borehole pressure and temperature changes

Purpose




The purpose of this paper is to present a new method for determining the input parameters of the concrete damaged plasticity (CDP) model of ABAQUS standard software. The existing available methods in the literatures are case sensitive, i.e., they give different input parameters of CDP for a unique concrete class used in different finite element (FE) simulation of concrete structures. In this study, the authors attempt to introduce a new approach for the identification of the input parameters of the CDP model, which guarantees the uniqueness and precision of the model. In other words, by this method, the input parameters obtained for a specific concrete class with a unique characteristic strength can be used for FE simulation of the different concrete structures which were constructed by this concrete without the need to additional modifications raised from any new application.




Design/methodology/approach




For the input parameter identification of the CDP model, different standard tests of plain concrete are simulated by the ABAQUS standard software. These test simulations are performed for various set of input parameters. In the end, those set of input parameters which represents the best curve fitting with the experimental results is chosen as the optimum parameters.




Findings




By comparison of the FE simulation results obtained from the ABAQUS for two different concrete structures using the proposed input parameters for the CDP model with the experimental results, it was shown that the presented method for determining those parameters can guarantee the uniqueness and precision of the CDP model in simulation.




Originality/value




The method described for determining the input parameters of the CDP model of the ABAQUS standard software has not been previously presented.

A new method for CDP input parameter identification of the ABAQUS software guaranteeing uniqueness and precision

In this research, the effect of the lateral and corner openings as well as the impact of using a kind of FRP sheets known as Carbon Fibre-Reinforced Polymer sheets (CFRPs) as a retrofitting approach on the RC two-way slabs' bearing capacity was investigated. To this end, at first, an enhanced finite-element (FE) model of an actual laboratory sample of a reinforced concrete slab with central opening was simulated using well-known Abaqus software and verified using available experimental results. For concrete behaviour simulation, concrete-damaged plasticity (CDP) material model of Abaqus standard code which can predict well the nonlinear behaviour of concrete from the initial steps of loading scenario up to the failure state was used and its parameters were identified for this particular application. For verifying the identification, two concrete beam test set-up were simulated and the obtained results were compared with the laboratory test results. The reason of implementing such a constitutive model is t...

The numerical simulations of the strengthened RC slabs with CFRPs using standard CDP material model of Abaqus code

Analysis and prediction of structural response to static or dynamic loading requires prediction of concrete response tovariable load histories. The constitutive equations for the mechanical behavior of concrete capable of seeing damage effects or crack growth procedure under loading/unloading/reloading was developed upon micro-plane framework. The proposed damage formulation has been built on the basis of five fundamental types of stress/strain combinations, which essentially may occur on any of micro-planes. Model verification under different loading/unloading/reloading stress/strain paths has been examined. The proposed model is capable of presenting pre-failure history of stress/strain progress on different predefined sampling planes through material. Many of mechanical behavior aspects happen during plasticity such as induced anisotropy, rotation of principal stress/strain axes, localization of stress/strain, and even failure mechanism are predicted upon a simple rational way and can be presented.

/pdf/a-continuum-discontinuum-micro-plane-damage-model-for-vybsvk9u6p.pdf

A Continuum/Discontinuum Micro Plane Damage Model for Concrete

The constitutive equations for the mechanical behavior of concrete capable of seeing damage effects or crack growth procedure under loading/unloading/reloading was developed upon microplane framework. The proposed damage formulation has been built on the basis of five fundamental types of stress/strain combinations, which essentially may occur on any of microplanes. Model verification under different loading/unloading/reloading stress/strain paths has been examined. The proposed model is capable of presenting pre-failure history of stress/strain progress on different predefined sampling planes through material. Many of mechanical behavior aspects happen during plasticity such as induced anisotropy, rotation of principal stress/strain axes, localization of stress/strain and even failure mechanism are predicted upon a simple rational way and can be presented.

Mojtaba Labibzadeh

Papers

Early-age compressive strength assessment of oil well class G cement due to borehole pressure and temperature changes

A new method for CDP input parameter identification of the ABAQUS software guaranteeing uniqueness and precision

The numerical simulations of the strengthened RC slabs with CFRPs using standard CDP material model of Abaqus code

A Continuum/Discontinuum Micro Plane Damage Model for Concrete

Mesoscopic Damage Based Model for Plane Concrete under Static and Dynamic Loadings