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1 – 10 of over 12000Richard Walls, Celeste Viljoen and Hennie de Clercq
This paper aims to provide a parametric investigation into the behaviour of steel, concrete and composite beams exposed to fire. This investigation gives insight into the…
Abstract
Purpose
This paper aims to provide a parametric investigation into the behaviour of steel, concrete and composite beams exposed to fire. This investigation gives insight into the structural behaviour of elements experiencing thermal and mechanical loading illustrating reasons for observed global structural behaviour, and identifying how selected design parameters influence results obtained. Non-linear heating/thermal bowing behaviour is specifically considered.
Design/methodology/approach
Cross-sectional stresses and strains, resultant thermal forces, bending stiffness, axial stiffness and deflections are plotted for beams subjected to different fire regimes or input values. The impact of changes in input parameters on beam section properties is illustrated. Unusual structural responses, localised effects and general trends are identified in relation to variations in thermal gradients, concrete tensile capacity, standard fire exposure time and the assumed concrete flange widths of composite beams.
Findings
Stress-strain plots highlighting cross-sectional structural behaviour, trends in beam properties and the influence of design parameters are provided. Some counter-intuitive behaviour is explained, such as increased member stiffness being offset by increased thermal effects, leading to this parameter having negligible impact on global behaviour but a significant effect on local stresses and strains. Increased concrete strengths may lead to increased thermal deformations, whilst the inclusion of concrete tensile capacity typically has a minimal influence.
Research limitations/implications
The research focusses on cross-sectional properties, although results generated illustrate how global behaviour is affected.
Practical implications
Design engineers are made aware of how selected input values influence predicted structural response. Also, localised stress and strain behaviour relative to imposed loads and thermal effects can be identified.
Originality/value
This paper provides novel insight into the (sometimes counter-intuitive) behaviour of beams exposed to fire, highlighting trends and the influence of important input parameters on predicted response.
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This paper gives a bibliographical review of the finite element methods (FEMs) applied to the analysis of ceramics and glass materials. The bibliography at the end of the paper…
Abstract
This paper gives a bibliographical review of the finite element methods (FEMs) applied to the analysis of ceramics and glass materials. The bibliography at the end of the paper contains references to papers, conference proceedings and theses/dissertations on the subject that were published between 1977‐1998. The following topics are included: ceramics – material and mechanical properties in general, ceramic coatings and joining problems, ceramic composites, ferrites, piezoceramics, ceramic tools and machining, material processing simulations, fracture mechanics and damage, applications of ceramic/composites in engineering; glass – material and mechanical properties in general, glass fiber composites, material processing simulations, fracture mechanics and damage, and applications of glasses in engineering.
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N. Keerthi Reddy, Aejung Yoon, Sankar Mani and H.A. Kumara Swamy
Natural convection in finite enclosures is a common phenomenon in various thermal applications. To provide the thermal design guidelines, this study aims to numerically explore…
Abstract
Purpose
Natural convection in finite enclosures is a common phenomenon in various thermal applications. To provide the thermal design guidelines, this study aims to numerically explore the potential of using internal baffles and nanofluids to either enhance or suppress heat transport in a vertical annulus. Furthermore, the annular-shaped enclosure is filled with aqueous-silver nanofluid and the effects of five distinct nanoparticle shapes are examined. In addition, the influence of baffle design parameters, including baffle position, thickness and length, is thoroughly analyzed.
Design/methodology/approach
The finite difference method is used in conjunction with the alternating direction implicit and successive line over relaxation techniques to solve nonlinear and coupled partial differential equations. The single phase model is used for nanofluid which is considered as a homogeneous fluid with improved thermal properties. The independence tests are carried out for assessing the sufficiency of grid size and time step for obtaining results accurately.
Findings
The baffle dimension parameters and nanoparticle shape exhibit significant impact on the convective flow and heat transfer characteristics, leading to the following results: sphere- and blade-shaped nanoparticles demonstrate around 30% enhancement in the heat transport capability compared with platelet-shaped nanoparticles, which exhibit the least. When considering the baffle design parameter, either a decrease in the baffle length and thickness or an increase in baffle height leads to an improvement in heat transport rate. Consequently, a threefold increase in baffle height yields a 40% improvement in thermal performance.
Originality/value
Understanding the impact of nanoparticle shapes and baffle design parameters on flow and thermal behavior will enable engineers to provide valuable insight on thermal management and overall system efficiency. Therefore, the current work focuses on exploring buoyant nanofluid flow and thermal mechanism in a baffled annular-shaped enclosure. Specifically, an internal baffle that exhibits conductive heat transfer through it is considered, and the impact of baffle dimensions (thickness, length and position) on the fluid flow behavior and thermal characteristics is investigated. In addition, the current study also addresses the influence of five distinct nanoparticle shapes (e.g. spherical, cylindrical, platelet, blade and brick) on the flow and thermal behavior in the baffled annular geometry. In addition to deepening the understanding of nanofluid behavior in a baffled vertical annulus, the current study contributes to the ongoing advancements in thermal applications by providing certain guidelines to design application-specific enclosures.
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Kaiçar Ammous, Slim Abid and Anis Ammous
The paper aims to focus on the semiconductor temperature prediction in the multichip modules by using a simplified 1D model, easy to implement in the electronic simulation tools.
Abstract
Purpose
The paper aims to focus on the semiconductor temperature prediction in the multichip modules by using a simplified 1D model, easy to implement in the electronic simulation tools.
Design/methodology/approach
Accurate prediction of temperature variation of power semiconductor devices in power electronic circuits is important for obtaining optimum designs and estimating reliability levels. Temperature estimation of power electronic devices has generally been performed using transient thermal equivalent circuits. This paper has studied the thermal behaviour of the power modules. The study leads to correcting the junction temperature values estimated from the transient thermal impedance of each component operating alone. The corrections depend on multidimensional thermal phenomena in the structure.
Findings
The classic analysis of thermal phenomena in the multichip structures, independently of powers’ dissipated magnitude and boundary conditions, is not correct. An advanced 1D thermal model based on the finite element method is proposed. It takes into account the effect of the heat‐spreading angle of the different devices in the module.
Originality/value
The paper focuses on mathematical model of the thermal behaviour in the power module. The study leads to a correction of the junction temperature values estimated from the transient thermal impedance of each component given by manufacturers. The proposed model gives a good trade‐off between accuracy, efficiency and simulation cost.
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This paper aims to develop an assembly behaviour dynamic model of reheat stop valve assembly under run‐time situations and combined (assembly error, friction, fluid dynamics and…
Abstract
Purpose
This paper aims to develop an assembly behaviour dynamic model of reheat stop valve assembly under run‐time situations and combined (assembly error, friction, fluid dynamics and thermal load behaviour) and to carry out assembly process evaluation and optimisation.
Design/methodology/approach
The fluid dynamic behaviour analysis is carried out for the dynamic torque characteristics of reheat stop valve and for the thermal load distribution of the valve shaft‐bush subassembly, which is used for evaluating the thermal deformation of valve shaft by using of finite elements method. The assembly behaviour dynamic model is developed by multibody dynamics theory, which is as the basis of developing virtual prototyping platform for analysing and evaluating the current assembly process.
Findings
It is revealed that the deformation (ε) of valve shaft due to the thermal load, and the assembly coaxial error (e) can change the motion clearance remarkably, which lead the dynamic properties and performance of reheat stop valve changed greatly. The current assembly behaviour variable are not optimum and the initial design clearance between valve shaft and bush 4# can be optimised by the developed virtual prototyping platform on the basis of ADAMS® API. The results of evaluation for the assembly behaviour reveal the well dynamic characteristics of reheat stop valve with the optimum assembly behaviour variable. This will be useful for improving the current assembly process of reheat stop valve.
Research limitations/implications
The present assembly behaviour dynamic model based on virtual prototyping for optimum assembly process design uses only single objective optimisation (the most important clearance between valve shaft and bush 4#). For a complete optimum assembly process design has to be carried out with other three clearance variables (the clearance between valve shaft and bush 1#, bush 2# and bush 3#) together.
Practical implications
The present analysis provides some benchmarks for improving the current assembly process. In practice, the assembly coaxial tolerance of valve shaft‐bush subassembly and the initial design clearances must be limited strictly.
Originality/value
This paper provides a methodology for analysis and evaluation of reheat stop valve assembly behaviour with the consideration of combined environmental behaviours. Based on this methodology, it is possible to develop an assembly behaviour dynamic model, and further, to develop a virtual prototyping platform for analysing and evaluating the assembly process which will offer help to designers for improving the reheat stop valve assembly process.
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The purpose of this study is to investigate the unstable propagation of parallel hydraulic fractures induced by interferences of adjacent perforation clusters and thermal…
Abstract
Purpose
The purpose of this study is to investigate the unstable propagation of parallel hydraulic fractures induced by interferences of adjacent perforation clusters and thermal diffusion. Fracture propagation in the process of multistage fracturing of a rock mass is deflected owing to various factors. Hydrofracturing of rock masses in deep tight reservoirs involves thermal diffusion, fluid flow and deformation of rock between the rock matrix and fluid in pores and fractures.
Design/methodology/approach
To study the unstable propagation behaviours of three-dimensional (3D) parallel hydraulic fractures induced by the interferences of adjacent perforation clusters and thermal diffusion, a 3D engineering-scale numerical model is established under different fracturing scenarios (sequential, simultaneous and alternate fracturing) and different perforation cluster spacings while considering the thermal-hydro-mechanical coupling effect. Stress disturbance region caused by fracture propagation in a deep tight rock mass is superimposed and overlaid with multiple fractures, resulting in a stress shadow effect and fracture deflection.
Findings
The results show that the size of the stress shadow areas and the interaction between fractures increase with decreasing multiple perforation cluster spacing in horizontal wells. Alternate fracturing can produce more fracture areas and improve the fracturing effect compared with those of sequential and simultaneous fracturing. The larger the temperature gradient between the fracturing fluid and rock matrix, the stronger the thermal diffusion effect, and the effect of thermal diffusion on the fracture propagation is significant.
Originality/value
This study focuses on the behaviours of the unstable dynamic propagation of 3D parallel hydraulic fractures induced by the interferences of adjacent perforation clusters and thermal diffusion. Further, the temperature field affects the fracture deflection requires could be investigated from the mechanisms; this paper is to study the unstable propagation of fractures in single horizontal well, which can provide a basis for fracture propagation and stress field disturbance in multiple horizontal wells.
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Anne-Charlotte Goupil, Jean-Charles Craveur, Benjamin Mercier and Philippe Barabinot
This paper aims to deal with numerical modelling of composite panels of naval industry exposed to fire. Finite element (FE) analyses have been used to study the thermomechanical…
Abstract
Purpose
This paper aims to deal with numerical modelling of composite panels of naval industry exposed to fire. Finite element (FE) analyses have been used to study the thermomechanical behaviour of structures. This paper focuses more particularly on assumptions used to model and evaluate design performance of sandwich panels made of E-Glass vinyl ester and balsawood cored submitted to a certification fire test.
Design/methodology/approach
The methodology consisted of having an advanced understanding of phenomena occurring in both thermal and mechanical behaviours when large structures are degraded under thermal solicitation. Then, properties measuring methods were explored and studied in relation with the size of the structure they are used to describe. Finally, several modelling strategies were compared and applied to large-size panels under ISO 834 fire conditions.
Findings
Research studies and comparisons showed that for these types of material and these types of structure, non-linear thermomechanical behaviour can be performed with a so-called “reduced” thermal model, provided that properties are measured in an appropriate way. “Reduced” model was compared with “full” model, and results were close to experimental measures. A mechanical properties’ review allowed selecting only necessary material FE analysis of large panels under ISO 834 fire.
Originality/value
The research was conducted on real-size structures taking into account the real conditions in which structures are tested when passing certification. Work was carried out on reducing numerical model size without neglecting phenomenon or losing accuracy.
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Improper evaluation and information mismanagement concerning thermal comfort appears to negatively affect occupants' satisfaction and building energy consumption in precast…
Abstract
Purpose
Improper evaluation and information mismanagement concerning thermal comfort appears to negatively affect occupants' satisfaction and building energy consumption in precast concrete (PC) building contexts. Predictive models are particularly problematic in PC building construction projects where natural ventilation levels do not coincide with occupants' thermal comfort and thermal sensation specifications.
Design/methodology/approach
A systematic literature review is undertaken to explore the viability and benefits of a new ICT-based approach for meeting social and environmental objectives.
Findings
Sophisticated thermal comfort system solutions are essential for optimising thermal comfort and saving energy in PC building construction projects.
Originality/value
It is imperative that designers and manufacturers are kept up-to-date with the possibilities and potentials associated with new and nascent technologies so that building projects can meet key sustainability criteria.
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The purpose of this study was to investigate the thermal deformation effect of a machine tool frame on hole registration accuracy. Hole registration accuracy represents the…
Abstract
Purpose
The purpose of this study was to investigate the thermal deformation effect of a machine tool frame on hole registration accuracy. Hole registration accuracy represents the drilling performance of a machine tool, and it greatly depends on the thermal deformation of the machine frame structures in practical engineering. Reducing thermally induced errors is crucial to improve the hole quality.
Design/methodology/approach
First, the thermal design of the machine frame was performed via an optimization procedure to reduce the thermal deformation at an early stage. Then, a thermal–mechanical coupling finite element method model was established to quantify the thermal deformation of the machine tool under environmental temperature fluctuations, and the validity of the presented model was confirmed experimentally using laser interferometry. Finally, a series of drilling tests, including micro-holes and medium holes, was carried out to practically investigate the hole drilling registration accuracy of the machine with a mineral casting frame under different thermal conditions.
Findings
Hole registration accuracy showed positional dependency and distinctly non-linear behaviour at different drilling axes which was closely related with the thermal conditions. The positional deviations of medium holes and micro-holes all showed an increasing trend in different degrees under the same temperature fluctuations, and the former were more sensitive to the latter. Therefore, keeping the drilling workshop under thermally stable conditions is crucial for improving the drilling performance of the machine.
Originality/value
The goal of this paper is to reveal the mechanism of hole registration accuracy variations with thermal fluctuations and to provide a strategy for the machine tool industry to further improve the drilling performance during the machining process.
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Kamel Ettaieb, Sylvain Lavernhe and Christophe Tournier
This paper aims to propose an analytical thermal three-dimensional model that allows an efficient evaluation of the thermal effect of the laser-scanning path. During manufacturing…
Abstract
Purpose
This paper aims to propose an analytical thermal three-dimensional model that allows an efficient evaluation of the thermal effect of the laser-scanning path. During manufacturing by laser powder bed fusion (LPBF), the laser-scanning path influences the thermo-mechanical behavior of parts. Therefore, it is necessary to validate the path generation considering the thermal behavior induced by this process to improve the quality of parts.
Design/methodology/approach
The proposed model, based on the effect of successive thermal flashes along the scanning path, is calibrated and validated by comparison with thermal results obtained by FEM software and experimental measurements. A numerical investigation is performed to compare different scanning path strategies on the Ti6Al4V material with different stimulation parameters.
Findings
The simulation results confirm the effectiveness of the approach to simulate the thermal field to validate the scanning strategy. It suggests a change in the scale of simulation thanks to high-performance computing resources.
Originality/value
The flash-based approach is designed to ensure the quality of the simulated thermal field while minimizing the computational cost.
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