A. Huerta and F. Casadei
The arbitrary Lagrangian—Eulerian (ALE)formulation, which is already well established in the hydrodynamics andfluid‐structure interaction fields, is extended to materials…
Abstract
The arbitrary Lagrangian—Eulerian (ALE) formulation, which is already well established in the hydrodynamics and fluid‐structure interaction fields, is extended to materials with memory, namely, non‐ linear path‐dependent materials. Previous attempts to treat non‐ linear solid mechanics with the ALE description have, in common, the implicit interpolation technique employed. Obviously, this implies a numerical burden which may be uneconomical and may induce to give up this formulation, particularly in fast‐transient dynamics where explicit algorithms are usually employed. Here, several applications are presented to show that if adequate stress updating techniques are implemented, the ALE formulation could be much more competitive than classical Lagrangian computations when large deformations are present. Moreover, if the ALE technique is interpreted as a simple interpolation enrichment, adequate—in opposition to distorted or locally coarse—meshes are employed. Notice also that impossible computations (or at least very involved numerically) with a Lagrangian code are easily implementable in an ALE analysis. Finally, it is important to observe that the numerical examples shown range from a purely academic test to real engineering simulations. They show the effective applicability of this formulation to non‐linear solid mechanics and, in particular, to impact, coining or forming analysis.
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A finite element procedure is presented for refined transient analysis of two‐dimensional (plane or axisymmetric) non‐linear structures involving arbitrarily large displacements…
Abstract
A finite element procedure is presented for refined transient analysis of two‐dimensional (plane or axisymmetric) non‐linear structures involving arbitrarily large displacements, rotations and strains. The finite element model is based on the biquadratic nine‐node element of the Lagrange family. The relevant points pertaining to the equations of motion and their integration and to the spatial description, including geometrical and material non‐linearities, are considered. In particular, stress and strain rates are discussed. Finally, significant numerical applications show the effectiveness of the proposed method.
Yuri Merizalde, Luis Hernández-Callejo, Oscar Duque-Pérez and Víctor Alonso-Gómez
Despite the wide dissemination and application of current signature analysis (CSA) in general industry, CSA is not commonly used in the wind industry, where the use of vibration…
Abstract
Purpose
Despite the wide dissemination and application of current signature analysis (CSA) in general industry, CSA is not commonly used in the wind industry, where the use of vibration signals predominates. Therefore, the purpose of this paper is to review the use of generator CSA (GCSA) in the online fault detection and diagnosis of wind turbines (WTs).
Design/methodology/approach
This is a bibliographical investigation in which the use of GCSA for the maintenance of WTs is analyzed. A section is dedicated to each of the main components, including the theoretical foundations on which GCSA is based and the methodology, mathematical models and signal processing techniques used by the proposals that exist on this topic.
Findings
The lack of appropriate technology and mathematical models, as well as the difficulty involved in performing actual studies in the field and the lack of research projects, has prevented the expansion of the use of GCSA for fault detection of other WT components. This research area has yet to be explored, and the existing investigations mainly focus on the gearbox and the doubly fed induction generator; however, modern signal treatment and artificial intelligence techniques could offer new opportunities in this field.
Originality/value
Although literature on the use of GCSA for the detection and diagnosis of faults in WTs has been published, these papers address specific applications for each of the WT components, especially gearboxes and generators. For this reason, the main contribution of this study is providing a comprehensive vision for the use of GCSA in the maintenance of WTs.
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There are still many different theoretical approaches and practical interpretations about what an integrated report is. Starting from this premise, the overall purpose of this…
Abstract
There are still many different theoretical approaches and practical interpretations about what an integrated report is. Starting from this premise, the overall purpose of this chapter is to critically analyze the relationship between integrated reporting (IR) and social/sustainability disclosure. Indeed, although some scholars considered IR as a tool to improve the sustainability approach of the companies allowing to disclose more relevant social information, others are more critical about the potentiality of IR to improve social disclosure. Therefore, the general research question is: Is there a natural link between IR and social disclosure (true love) or is the IR a practice to “normalize” the social disclosure and accounting (forced marriage)?
In the attempt to provide a preliminary answer to the research question, the chapter analyzes what is the approach of three categories: (1) academics; (2) soft-regulators; and (3) companies. From the methodological point of view, a mixed method of analysis has been adopted.
From the analysis of the three different points of view, IR can be considered as a “contested concept” because of the heterogeneous and sometimes conflicting interpretations and implementation that are done on this type of report. This leads to relevant theoretical and practical implications.
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Q.M Mehran, A.R Bushroa, M.A Fazal and M.M. Quazi
– The purpose of this study is to design and develop a new functional coating system for aerospace AL7075-T6 alloy that would evaluate the mechanical properties of the coating.
Abstract
Purpose
The purpose of this study is to design and develop a new functional coating system for aerospace AL7075-T6 alloy that would evaluate the mechanical properties of the coating.
Design/methodology/approach
This paper outlines the scratch adhesion characterisation of Cr/CrAlN coating using a combination of radio frequency (RF) and direct current (DC) physical vapour deposition (PVD) magnetron sputtering. The surface morphology, microstructure and chemical composition of the Cr/CrAlN film were evaluated by optical microscopy (OM), field emission scanning electron microscopy (FESEM) integrated with energy-dispersive X-Ray spectroscopy (EDX) and atomic force microscopy (AFM). The film-to-substrate adhesion was measured by a scratch test machine manufactured with a detection system, motorized stages, penetration depth sensors, optical microscope and tangential frictional load sensors.
Findings
The AFM and ultra-micro hardness results showed an increase in surface roughness to about 20 per cent and hardness to about 74 per cent. Moreover, the film-to-substrate adhesion strength of 1,814 mN was obtained with PVD deposition process.
Research limitations/implications
The main limitation of this work is caused by PVD deposition process. Besides, surface defects such as pinholes contribute to a decrease in adhesion strength.
Practical implications
The higher hardness of CrAlN coating is used to improve the properties of softer aluminium substrates. This hardness prevents ploughing-induced wear and provides greater adhesion strength by preventing coating delamination.
Originality/value
Until now, CrAlN is coated only on ferrous alloys. It has not yet been tried on aluminium alloys. Moreover, coating functionality depends on higher adhesion and failure mechanisms involved in the film-to-substrate system, which is significant in aerospace applications.
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Etienne Muller, Dominique Pelletier and André Garon
This paper aims to focus on characterization of interactions between hp-adaptive time-integrators based on backward differentiation formulas (BDF) and adaptive meshing based on…
Abstract
Purpose
This paper aims to focus on characterization of interactions between hp-adaptive time-integrators based on backward differentiation formulas (BDF) and adaptive meshing based on Zhu and Zienkiewicz error estimation approach. If mesh adaptation only occurs at user-supplied times and results in a completely new mesh, it is necessary to stop the time-integration at these same times. In these conditions, one challenge is to find an efficient and reliable way to restart the time-integration. The authors investigate what impact grid-to-grid interpolation errors have on the relaunch of the computation.
Design/methodology/approach
Two restart strategies of the time-integrator were used: one based on resetting the time-step size h and time-integrator order p to default values (used in the initial startup phase), and another designed to restart with the time-step size h and order p used by the solver prior to remeshing. The authors also investigate the benefits of quadratically interpolate the solution on the new mesh. Both restart strategies were used to solve laminar incompressible Navier–Stokes and the Unsteady Reynolds Averaged Naviers-Stokes (URANS) equations.
Findings
The adaptive features of our time-integrators are excellent tools to quantify errors arising from the data transfer between two grids. The second restart strategy proved to be advantageous only if a quadratic grid-to-grid interpolation is used. Results for turbulent flows also proved that some precautions must be taken to ensure grid convergence at any time of the simulation. Mesh adaptation, if poorly performed, can indeed lead to losing grid convergence in critical regions of the flow.
Originality/value
This study exhibits the benefits and difficulty of assessing both spatial error estimates and local error estimates to enhance the efficiency of unsteady computations.
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Isabel Coenen, Thomas Herold, Christelle Piantsop Mbo'o and Kay Hameyer
Manufacturing tolerances can result in an unwanted behavior of electrical machines. A quality control of machines subsequent to manufacturing is therefore required in order to…
Abstract
Purpose
Manufacturing tolerances can result in an unwanted behavior of electrical machines. A quality control of machines subsequent to manufacturing is therefore required in order to test whether the machines comply with its specifications. This paper aims to describe the consideration of rotor tolerances due to non-ideal manufacturing processes.
Design/methodology/approach
Various fault scenarios are studied employing numerical field simulations focusing the influence of rotor tolerances on current and back-EMF of the studied machine.
Findings
This analysis shows that electrical quantities are applicable to realize tolerance diagnosis by evaluating the influence of non-ideal manufactured rotor components on the back-EMF and current characteristics of the studied machine.
Practical implications
This study provides an approach how to estimate the influence of the manufacturing tolerances for realization of a reliable quality control. This is useful to ensure a high reliability of the manufactured machines.
Originality/value
This paper gives a close insight on how to investigate non-ideal manufacturing and in particular its influence on the stator current.
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Andrzej Sikorski and Marek Korzeniewski
The aim of the paper is to conduct an analytical study of a new method of induction motor torque and flux direct control with nonlinear controllers.
Abstract
Purpose
The aim of the paper is to conduct an analytical study of a new method of induction motor torque and flux direct control with nonlinear controllers.
Design/methodology/approach
The method is based on the inverter state predictive determination in order to minimize the torque and flux errors.
Findings
The proposed method allows one to eliminate known DTC disadvantages, i.e. the hexagonal flux shape and nonsinusoidal current at a low motor speed, and also secures a decrease of torque and flux pulsation.
Practical implications
This new method enables a more precise reproduction of the motor torque and flux command signals, working with the same sampling frequency of the control processor as in the case of the standard DTC method. The decreased torque pulsations cause a decrease of the motor speed pulsation.
Originality/value
An innovative optimal control method is presented. The correctness of the initial assumptions as well as the expected final results have been verified in practice.
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This paper aims to propose an improved direct torque control (DTC) for the induction motor’s performance enhancement using dual nonlinear techniques. The exact feedback…
Abstract
Purpose
This paper aims to propose an improved direct torque control (DTC) for the induction motor’s performance enhancement using dual nonlinear techniques. The exact feedback linearization is implemented to create a linear decoupled control. Besides, the fuzzy logic control approach has been inserted to generate the auxiliary control input for the feedback linearization controller.
Design/methodology/approach
To improve the DTC for induction motor drive, this work suggests the incorporation of two nonlinear approaches. As the classical feedback linearization suffers while the presence of uncertainties and modeling inaccuracy, it is recommended to be associated to another robust control approach to compensate the uncertainties of the model and make a robust control versus the variations of the machine parameters. Therefore, fuzzy logic controllers will be integrated as auxiliary inputs to the feedback linearization control law.
Findings
The simulation and the experimental validation of the proposed control algorithm show that the association of dual techniques can effectively achieve high dynamic behavior and improve the robustness against parameters variation and external disturbances. Moreover, the space vector modulation is used to preserve a fixed switching frequency, reduce ripples and low switching losses.
Practical implications
The theoretical, simulation and experimental studies prove that the proposed control algorithm can be used on different AC machines for variable speed drive applications such as oil drilling, traction systems and wind energy conversion systems.
Originality/value
The proposed DTC strategy has been developed theoretically and realized through simulation and experimental implementation. Different operation conditions have been conducted to check the ability and robustness of the control strategy, such as steady state, speed reversal maneuver, low-speed operation and parameters variation test with load application.