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Article
Publication date: 5 March 2018

Ling Weng, Ting Wang, Pei-Hai Ju and Li-Zhu Liu

This paper aims to develope the electromagnetic interference shielding materials with high performance. To develop advanced polymer-based electromagnetic interference…

Abstract

Purpose

This paper aims to develope the electromagnetic interference shielding materials with high performance. To develop advanced polymer-based electromagnetic interference shielding materials with rather high temperature stability, good processability and moderate mechanical properties, the authors chose the polyimide (PI) foam as matrix and ferriferrous oxide (Fe3O4) as fillers to prepare the composite foams with lightweight and rather good electromagnetic interference shielding performance.

Design/methodology/approach

Some polyimide nanocomposite foams with Fe3O4 as fillers have been prepared by in situ dispersion and foaming with pyromellitic dianhydride (PMDA) and isocyanate (PAPI) as raw materials and water as foaming agent. By varying the Fe3O4 contents, a series of PI/Fe3O4 nanocomposite foams with fine microstructures and high thermal stability were obtained. The structure and performances of nanocomposite foams were examined, and the effects of Fe3O4 on the microstructure and properties of composite foams were investigated.

Findings

This work demonstrates that PI/Fe3O4 foams could be fabricated by thermally treating the polyimide foam intermediates with Fe3O4 nanoparticles through a blending reaction of precursors. The final PI/Fe3O4 composite foams maintained the excellent thermal property and showed a super paramagnetic behaviour, which has a positive effect on the improvement of electromagnetic shielding performance.

Research limitations/implications

In this paper, the effects of Fe3O4 on the performances of PI/Fe3O4 composite foam were reported. It provided an effective methodology for the preparation of polymer/Fe3O4 nanocomposite foams, which hold great promise towards the potential application in the areas of electromagnetic shielding materials.

Originality/value

A series of PI/Fe3O4 composite foams with different contents of Fe3O4 were prepared by blending reaction of the precursors. The effects of Fe3O4 on the structures and properties of PI/Fe3O4 composite foam were discussed in detail.

Details

Pigment & Resin Technology, vol. 47 no. 2
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 1 June 2005

O.A. Mohammed, Z. Liu, S. Liu and N.Y. Abed

The purpose of this research is to develop new techniques for component physical modeling for the dynamic simulation of integrated power systems.

Abstract

Purpose

The purpose of this research is to develop new techniques for component physical modeling for the dynamic simulation of integrated power systems.

Design/methodology/approach

A FE‐based phase variable model is proposed so as to achieve fast and accurate simulation. Such a model is established based on the nonlinear transient FE analysis, in order to take into consideration the harmonic effects due to the nonlinear magnetization property, magnetic circuit geometry as well as other design variations.

Findings

In the FE‐based phase variable model, the inductances are described as functions of the phase angle and the magnitude of winding currents, the rotor position and other operational parameters. They are obtained from the transient FE solutions, stored in tables, and retrieved during the simulation. The FE‐based phase variable model is implemented in Simulink in two ways. The first is the equation‐based block and the second is the circuit component‐based block. The FE‐based phase variable models of various electrical components in the power system were studied. This includes various types of rotating machines and transformers. Examination and application examples show the correctness and effectiveness of the proposed operational modeling procedures.

Originality/value

The developed FE‐based physical phase variable model is as accurate as the full FE model with much faster simulation speed. It will benefit the dynamic simulation of integrated power system. This combination of physical modeling and integrated dynamic simulation is original and represents an added value to the state‐of‐the‐art in this field.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 24 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 9 August 2013

M.A. Maleque and S. Sugrib

The aim of this paper is to study the tribological behaviour of Fe‐C‐Al cast iron at different temperatures using universal pin‐on‐disk machine.

Abstract

Purpose

The aim of this paper is to study the tribological behaviour of Fe‐C‐Al cast iron at different temperatures using universal pin‐on‐disk machine.

Design/methodology/approach

The cold set resin bonded sand mould casting process was employed to develop Fe‐C‐Al cast iron and Fe‐C‐Si cast iron. The microstructures of materials were studied using field emission scanning electron microscope. The wear and friction tests were conducted using universal pin‐on‐disk machine at 25°C, 100°C, 200°C and 300°C temperature. The worn surface was characterized using scanning electron microscopy.

Findings

The lower wear rate was found for Fe‐C‐Al cast iron compared to Fe‐C‐Si cast iron and delamination type wear morphology was observed in both types of cast iron materials. The results also showed that the friction coefficient value of Fe‐C‐Al cast iron was lower than that of Fe‐C‐Si cast iron at different temperatures. It can be concluded that the overall tribological behaviour of Fe‐C‐Al cast iron at higher temperatures was better than conventional Fe‐C‐Si cast iron.

Originality/value

The information on the development and tribological properties of the Fe‐C‐Al cast iron at different temperatures is scarce in the literature. The special type of cold set resin bonded sand mould was used for casting this Fe‐C‐Al cast iron material. Therefore, the current study is quite new and it is hoped that it will provide a high value to the automotive and other engineering researchers for the application of this material.

Details

Industrial Lubrication and Tribology, vol. 65 no. 5
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 19 September 2019

Kemin Li, Zhifu Huang, Hanwen Ma, Shaofei Wang, Chaofeng Qin and Pengcheng Liu

The purpose of this study was to investigate the tribological properties of bulk Fe2B with pre-oxidation treatment.

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Abstract

Purpose

The purpose of this study was to investigate the tribological properties of bulk Fe2B with pre-oxidation treatment.

Design/methodology/approach

Bulk Fe2B was oxidized in an electric box furnace with a soaking time of 9 min under 750°C in air. Then, the tribological experiments were carried out on an UMT-Tribolab tester.

Findings

The oxide layer was composed of Fe, Fe2O3, Fe3O4, B2O3 and H3BO3. The oxidative direction of bulk Fe2B was perpendicular to the sample surface. But, the oxidative direction of Fe2B crystals was irregular. At 0.1 m/s, the friction coefficient was the lowest. The effects of shortening the running-in period of friction and reducing the friction coefficient by pre-oxidation treatment at 0.1 m/s were remarkable. Nevertheless, the effect of pre-oxidation treatment was futile at 0.2 m/s. Wear mechanisms of oxidized Fe2B mainly were adhesive and abrasive wear.

Originality/value

The effects of shortening the running-in period of friction and reducing the friction coefficient by pre-oxidation treatment were remarkable.

Details

Industrial Lubrication and Tribology, vol. 72 no. 1
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 4 January 2022

Pandimani, Markandeya Raju Ponnada and Yesuratnam Geddada

The partially prestressed concrete beam with unbonded tendon is still an active field of research because of the difficulty in analyzing and understanding its behavior…

Abstract

Purpose

The partially prestressed concrete beam with unbonded tendon is still an active field of research because of the difficulty in analyzing and understanding its behavior. The finite-element (FE) simulation of such beams using numerical software is very scarce in the literature and therefore this study is taken to demonstrate the modeling aspects of unbonded partially prestressed concrete (UPPSC) beams. This study aims to present the three-dimensional (3-D) nonlinear FE simulations of UPPSC beams subjected to monotonic static loadings using the numerical analysis package ANSYS.

Design/methodology/approach

The sensitivity study is carried out with three different mesh densities to obtain the optimum elements that reflect on the load–deflection behavior of numerical models, and the model with optimum element density is used further to model all the UPPSC beams in this study. Three half-symmetry FE model is constructed in ANSYS parametric design language domain with proper boundary conditions at the symmetry plane and support to achieve the same response as that of the full-scale experimental beam available in the literature. The linear and nonlinear material behavior of prestressing tendon and conventional steel reinforcements, concrete and anchorage and loading plates are modeled using link180, solid65 and solid185 elements, respectively. The Newton–Raphson iteration method is used to solve the nonlinear solution of the FE models.

Findings

The evolution of concrete cracking at critical loadings, yielding of nonprestressed steel reinforcements, stress increment in the prestressing tendon, stresses in concrete elements and the complete load–deflection behavior of the UPPSC beams are well predicted by the proposed FE model. The maximum discrepancy of ultimate moments and deflections of the validated FE models exhibit 13% and −5%, respectively, in comparison with the experimental results.

Practical implications

The FE analysis of UPPSC beams is done using ANSYS software, which is a versatile tool in contrast to the experimental testing to study the stress increments in the unbonded tendons and assess the complete nonlinear response of partially prestressed concrete beams. The validated numerical model and the techniques presented in this study can be readily used to explore the parametric analysis of UPPSC beams.

Originality/value

The developed model is capable of predicting the strength and nonlinear behavior of UPPSC beams with reasonable accuracy. The load–deflection plot captured by the FE model is corroborated with the experimental data existing in the literature and the FE results exhibit good agreement against the experimentally tested beams, which expresses the practicability of using FE analysis for the nonlinear response of UPPSC beams using ANSYS software.

Details

Journal of Engineering, Design and Technology , vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1726-0531

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Article
Publication date: 20 August 2021

Pandimani, Markandeya Raju Ponnada and Yesuratnam Geddada

This paper aims to present nonlinear numerical simulations using the versatile finite element (FE) analysis tool ANSYS and theoretical analysis based on code provisions to…

Abstract

Purpose

This paper aims to present nonlinear numerical simulations using the versatile finite element (FE) analysis tool ANSYS and theoretical analysis based on code provisions to assess the load-carrying capacity of reinforced concrete (RC) beams under two-point monotonic static loadings.

Design/methodology/approach

Four quarter-size FE models with load and geometry symmetry conditions were constructed, the load-bearing capacity and associated mid-span deflections at critical points are verified against the full-scale experimental RC beams available in the literature. These developed FE models incorporated the tension stiffening effects and bond–slip behaviour. Theoretical analyses based on Indian standard code IS: 456–2000 and ACI 318–19 were also carried to verify the experimental and numerical predicted moments at critical loading points.

Findings

The load-deflection curves predicted through FE models exhibit closer corroboration with the experimental curves throughout the loading history. The contour plots for deflections, concrete principal stresses, reinforcement yield stresses are satisfactorily predicted by the FE models, which reveal the complete information of nonlinear behaviour of RC beams. The developed model well captured the initial and progressive crack patterns at each load increments.

Practical implications

The FE modelling is an efficient, valid and economical tool that is an alternative to the expensive experimental program and can be used to explore, analyse and fully understand the nonlinear response of RC beams under static loadings.

Originality/value

The ultimate moment capacity evaluated based on ACI 318–19 code provision show a better correlation with the experimental data as compared to the IS: 456–2000 code provision. The ultimate loads and associated centre-span deflections predicted by RN-2, RN-3, RB-12 and RB-16 FE model show a discrepancy of 1.66 and –0.49%, –4.68 and –0.60%, –9.38 and –14.53% and –4.37 and 4.21%, respectively, against the experimental results, which reveals that the developed ANSYS FE models predict consistent results and achieved a reasonable agreement with the experimental data.

Details

Journal of Engineering, Design and Technology , vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1726-0531

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Article
Publication date: 4 August 2021

Pandimani, Markandeya Raju Ponnada and Yesuratnam Geddada

This study aims to present comprehensive nonlinear material modelling techniques and simulations of reinforced concrete (RC) beams subjected to short-term monotonic static…

Abstract

Purpose

This study aims to present comprehensive nonlinear material modelling techniques and simulations of reinforced concrete (RC) beams subjected to short-term monotonic static load using the robust and reliable general-purpose finite element (FE) software ANSYS. A parametric study is carried out to analyse the flexural and ductility behaviour of RC beams under various influencing parameters.

Design/methodology/approach

To develop and validate the numerical FE models, a total of four experimentally tested simply supported RC beams are taken from the available literature and two beams are selected from each author. The concrete, steel reinforcements, bond-slip mechanism, loading and supporting plates are modelled using SOLID65, LINK180, COMBIN39 and SOLID185 elements, respectively. The validated models are then used to conduct parametric FE analysis to investigate the effect of concrete compressive strength, percentage of tensile reinforcement, compression reinforcement ratio, transverse shear reinforcement, bond-slip mechanism, concrete compressive stress-strain constitutive models, beam symmetry and varying overall depth of beam on the ultimate load-carrying capacity and ductility behaviour of RC beams.

Findings

The developed three-dimensional FE models can able to capture the load and midspan deflections at critical points, the accurate yield point of steel reinforcements, the formation of initial and progressive concrete crack patterns and the complete load-deflection curves of RC beams up to ultimate failure. From the numerical results, it can be concluded that the FE model considering the bond-slip effect with Thorenfeldt’s concrete compressive stress-strain model exhibits a better correlation with the experimental data.

Originality/value

The ultimate load and deflection results of validated FE models show a maximum deviation of less than 10% and 15%, respectively, as compared to the experimental results. The developed model is also capable of capturing concrete failure modes accurately. Overall, the FE analysis results were found quite acceptable and compared well with the experimental data at all loading stages. It is suggested that the proposed FE model is a practical and reliable tool for analyzing the flexural behaviour of RC members and can be used for performing parametric studies.

Details

World Journal of Engineering, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1708-5284

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Abstract

Details

Contingent Valuation: A Critical Assessment
Type: Book
ISBN: 978-1-84950-860-5

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Book part
Publication date: 18 January 2022

Artūras Juodis

This chapter analyzes the properties of an alternative least-squares based estimator for linear panel data models with general predetermined regressors. This approach uses…

Abstract

This chapter analyzes the properties of an alternative least-squares based estimator for linear panel data models with general predetermined regressors. This approach uses backward means of regressors to approximate individual specific fixed effects (FE). The author analyzes sufficient conditions for this estimator to be asymptotically efficient, and argue that, in comparison with the FE estimator, the use of backward means leads to a non-trivial bias-variance tradeoff. The author complements theoretical analysis with an extensive Monte Carlo study, where the author finds that some of the currently available results for restricted AR(1) model cannot be easily generalized, and should be extrapolated with caution.

Details

Essays in Honor of M. Hashem Pesaran: Panel Modeling, Micro Applications, and Econometric Methodology
Type: Book
ISBN: 978-1-80262-065-8

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Book part
Publication date: 17 May 2021

Sarah Cooper and Sara Pearman

This chapter explores the numerous considerations that an external examiner (EE) of an undergraduate degree within a further-education (FE) college must be mindful. There…

Abstract

This chapter explores the numerous considerations that an external examiner (EE) of an undergraduate degree within a further-education (FE) college must be mindful. There may be the perception that our academic experience of lecturing within a university equips us with the knowledge to collaborate with colleagues within an FE institution. However, this is valid only to a certain point. There is a spectrum of contrasts between the higher education (HE) and FE environments that are reflected within the comparisons that this chapter highlights between the teaching-and-learning experiences. If we think back to the original purpose of an EE (where Oxford scholars were invited by Durham University to provide external guidance in the nineteenth century), we can appreciate the key task of an EE and its aim: to assess the comparability of student achievement. The landscape of HE has changed considerably since then, and now undulates with numerous opportunities for learners to gain a HE qualification. It is this difficulty in assessing comparability that an EE of a HE course within an FE environment must be willing to acknowledge. The fact that the student-and-learning experience varies wildly in HE and FE muddies the waters for the EE: how can comparableness be assessed?

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