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1 – 10 of over 6000Jing-feng Wang, Hai-Tao Wang, Wei-Wei Shi and Hong-Yu Sheng
This paper aims to obtain fire resistance of semi-rigid joints for concrete-filled steel tubular (CFST) composite frames and temperature filed distribution of composite joints in…
Abstract
Purpose
This paper aims to obtain fire resistance of semi-rigid joints for concrete-filled steel tubular (CFST) composite frames and temperature filed distribution of composite joints in fire.
Design/methodology/approach
The temperature filed model of semi-rigid joints to CFST columns with slabs was made by using ABAQUS finite element (FE) software, in considering temperature heating-up stage of fire modelling. The effects of composite slab, fire type and construction location were discussed, and the model was verified by the test results. The temperature distribution of composite joint under three-side or four-side fire condition was studied by the sequentially coupled thermal analysis method. The temperature versus time curves and temperature distribution of various construction and location were analyzed.
Findings
The paper provides FE analysis and numerical simulation on temperature field of semi-rigid joints for CFST composite frames in fire. The effects of composite slab, fire type and construction location were discussed, and the model was verified by the test results. It suggests that the temperature distribution of composite joint in three- or four-side fire condition showed a different development trend.
Research limitations/implications
Because of the chosen FE analysis approach, the research results may lack generalizability. Therefore, researchers are encouraged to test the proposed propositions further.
Practical implications
The research results will become the scientific foundation of mechanical behavior and design method of semi-rigid CFST composite frames in fire.
Originality/value
This paper fulfils an identified need to study the temperature field distribution of the semi-rigid joints to CFST columns and investigate the mechanical behavior of the semi-rigid CFST joints in fire.
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Zhangxin Guo, Zhiqiang Yu, Shiyi Wei, Guoliang Qi, Yongcun Li and Yunbo Luan
The cure simulation of composite structures with arbitrary geometry can be investigated by the finite element program.
Abstract
Purpose
The cure simulation of composite structures with arbitrary geometry can be investigated by the finite element program.
Design/methodology/approach
Finite element method is employed in this work.
Findings
The simulated results match the experimental results well, which demonstrates the finite element analysis models are reliable. Compared with the one- and two-dimensional finite element analysis, temperature and degree of cure can be calculated at any point within composite structures in the present simulation analysis. The cure simulation of composite structures with arbitrary geometry can be investigated by the finite element program.
Originality/value
A coupled thermokinetic simulation of the liquid composite molding process based on a three-dimensional finite element method is presented. The cure simulation of composite structures with arbitrary geometry can be investigated by the finite element program.
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Huaqing Hu, Ketai He, Tianlin Zhong and Yili Hong
This paper aims to propose a method to diagnose fused deposition modeling (FDM) printing faults caused by the variation of temperature field and establish a fault knowledge base…
Abstract
Purpose
This paper aims to propose a method to diagnose fused deposition modeling (FDM) printing faults caused by the variation of temperature field and establish a fault knowledge base, which helps to study the generation mechanism of FDM printing faults.
Design/methodology/approach
Based on the Spearman rank correlation analysis, four relative temperature parameters are selected as the input data to train the SVM-based multi-classes classification model, which further serves as a method to diagnose the FDM printing faults.
Findings
It is found that FDM parts may be in several printing states with the variation of temperature field on the surface of FDM parts. The theoretical dividing lines between different FDM printing states are put forward by traversing all the four-dimensional input parameter combinations. The relationship between the relative mean temperature and the theoretical dividing lines is found to be close and is analyzed qualitatively.
Originality/value
The multi-classes classification model, embedded in FDM printers as an adviser, can be used to prevent waste products and release much work of labors for monitoring.
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Jianjun Zhang, Qibo Ni, Jing Wang and Feng Guo
Vibration exists widely in all machineries working under high speed. The unpredictability of vibration and the change of the relative surface speed may result in difficulties in…
Abstract
Purpose
Vibration exists widely in all machineries working under high speed. The unpredictability of vibration and the change of the relative surface speed may result in difficulties in the elastohydrodynamic lubrication (EHL) analysis. By far, few studies on EHL relating to vibration have been published. The purpose of the present study is to investigate the effect of the vertical vibrations and the influence of temperature on the thermal EHL contacts.
Design/methodology/approach
The lubricant was assumed to be Newtonian fluid. The time-dependent numerical solutions were achieved instant after instant in each period of the vibration. At each instant, the pressure field was solved with a multi-level technique, the surface deformation was solved with a multi-level multi-integration method and the temperature filed was solved with a finite different scheme through a sweeping progress. The periodic error was checked at each end of the vibration period until the responses of pressure, film thickness and temperature were all periodic functions with the frequency of the roller’s vibrations.
Findings
The results reveal that normal vibration produces little drastic change of pressure, film thickness and temperature in EHL. Under some conditions, the vibrations of the roller can produce transient dimples within the contact conjunction. It is also showed that the lubrication in the same sliding is better than the opposite sliding.
Research limitations/implications
For the unpredictability of vibration, it is not easy to do the experiment to realize a real comparison with numerical results. The reach does not show any verification and consider the effect of non-Newtonian fluid.
Originality/value
The effect of the vertical vibrations on the thermal EHL point contact hast been studied. The effects of both the amplitude and the frequency on the predicted load-carrying capacity, minimum film thickness, center pressure and center temperature and the coefficient of friction were investigated. The role of the thermal effect was given.
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Zihao Shen, Yang Li, Kuizhou Liu, Jin Zhang and Yu Su
The coefficient of thermal expansion (CTE) and modulus of elasticity (ME) values of mortar and stone from room temperature to cryogenic temperatures provide an experimental basis…
Abstract
Purpose
The coefficient of thermal expansion (CTE) and modulus of elasticity (ME) values of mortar and stone from room temperature to cryogenic temperatures provide an experimental basis for the design of liquefied natural gas (LNG) storage tanks.
Design/methodology/approach
The CTE and ME of mortar and limestone were measured by resistance strain gauge testing technology at cryogenic temperatures.
Findings
The test results showed that CTE values of mortar and stone decreased with the decrease of temperature and CTE values of mortar was greater than that of stone from 0 °C to −165 °C. The ME values of mortar increased significantly at cryogenic temperatures, and less change in stone.
Originality/value
The material at cryogenic temperatures may continue to work in the elastic phase due to the continuous increase of elastic modulus. Therefore, the study of material in the elastic stage may be more important than in the ultimate bearing capacity stage, and it is necessary to carry out further study surrounding the deformation properties of materials at cryogenic temperatures. The CTE and ME values of mortar and stone from room temperature to cryogenic temperatures provide an experimental basis for the design of LNG storage tanks.
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Alireza Rahimi, Abbas Kasaeipoor, Emad Hasani Malekshah and Lioua Kolsi
This paper aims to perform the lattice Boltzmann simulation of natural convection heat transfer in cavities included with active hot and cold walls at the side walls and internal…
Abstract
Purpose
This paper aims to perform the lattice Boltzmann simulation of natural convection heat transfer in cavities included with active hot and cold walls at the side walls and internal hot and cold obstacles.
Design/methodology/approach
The cavity is filled with double wall carbon nanotubes (DWCNTs)-water nanofluid. Different approaches such as local and total entropy generation, local and average Nusselt number and heatline visualization are used to analyze the natural convection heat transfer. The cavity is filled with DWCNTs-water nanofluid and the thermal conductivity and dynamic viscosity are measured experimentally at different solid volume fractions of 0.01 per cent, 0.02 per cent, 0.05 per cent, 0.1 per cent, 0.2 per cent and 0.5 per cent and at a temperature range of 300 to 340 (K).
Findings
Two sets of correlations for these parameters based on temperature and solid volume fraction are developed and used in the numerical simulations. The influences of different governing parameters such as Rayleigh number, solid volume fraction and different arrangements of active walls on the fluid flow, heat transfer and entropy generation are presented, comprehensively. It is found that the different arrangements of active walls have pronounced influence on the flow structure and heat transfer performance. Furthermore, the Nusselt number has direct relationship with Rayleigh number and solid volume fraction. On the other hand, the total entropy generation has direct and reverse relationship with Rayleigh number and solid volume fraction, respectively.
Originality/value
The originality of this work is to analyze the two-dimensional natural convection using lattice Boltzmann method and different approaches such as entropy generation and heatline visualization.
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Zhenyang Zhu, Yi Liu, Zhe Fan, Sheng Qiang, Zhiqiang Xie, Weimin Chen and Congcong Wu
The buried pipe element method can be used to calculate the temperature of mass concrete through highly efficient computing. However, in this method, temperatures along cooling…
Abstract
Purpose
The buried pipe element method can be used to calculate the temperature of mass concrete through highly efficient computing. However, in this method, temperatures along cooling pipes and the convection coefficient of the cooling pipe boundary should be improved to achieve higher accuracy. Thus, there is a need to propose a method for improvement.
Design/methodology/approach
According to the principle of heat balance and the temperature gradient characteristics of concrete around cooling pipes, a method to calculate the water temperature along cooling pipes using the buried pipe element method is proposed in this study. By comparing the results of a discrete algorithm and the buried pipe element method, it was discovered that the convection coefficient of the cooling pipe boundary for the buried pipe element method is only related to the thermal conductivity of concrete; therefore, it can be calculated by inverse analysis.
Findings
The results show that the buried pipe element method can achieve the same accuracy as the discrete method and simulate the temperature field of mass concrete with cooling pipes efficiently and accurately.
Originality/value
This new method can improve the calculation accuracy of the embedded element method and make the calculation results more reasonable and reliable.
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Alireza Rahimi, Abbas Kasaeipoor, Emad Hasani Malekshah, Mohammad Mehdi Rashidi and Abimanyu Purusothaman
This study aims to investigate the three-dimensional natural convection and entropy generation in a cuboid enclosure filled with CuO-water nanofluid.
Abstract
Purpose
This study aims to investigate the three-dimensional natural convection and entropy generation in a cuboid enclosure filled with CuO-water nanofluid.
Design/methodology/approach
The lattice Boltzmann method is used to solve the problem numerically. Two different multiple relaxation time (MRT) models are used to solve the problem. The D3Q7–MRT model is used to solve the temperature field, and the D3Q19 is used to solve the fluid flow of natural convection within the enclosure.
Findings
The influences of different Rayleigh numbers (103 < Ra < 106) and solid volume fractions (0 < f < 0.04) on the fluid flow, heat transfer, total entropy generation, local heat transfer irreversibility and local fluid friction irreversibility are presented comprehensively. To predict thermo–physical properties, dynamic viscosity and thermal conductivity, of CuO–water nanofluid, the Koo–Kleinstreuer–Li (KKL) model is applied to consider the effect of Brownian motion on nanofluid properties.
Originality/value
The originality of this work is to analyze the three-dimensional natural convection and entropy generation using a new numerical approach of dual-MRT-based lattice Boltzmann method.
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Alireza Rahimi, Aravindhan Surendar, Aygul Z. Ibatova, Abbas Kasaeipoor and Emad Hasani Malekshah
This paper aims to investigate the three-dimensional natural convection and entropy generation in the rectangular cuboid cavities included by chamfered triangular partition made…
Abstract
Purpose
This paper aims to investigate the three-dimensional natural convection and entropy generation in the rectangular cuboid cavities included by chamfered triangular partition made by polypropylene.
Design/methodology/approach
The enclosure is filled by multi-walled carbon nanotubes (MWCNTs)-H2O nanofluid and air as two immiscible fluids. The finite volume approach is used for computation. The fluid flow and heat transfer are considered with combination of local entropy generation due to fluid friction and heat transfer. Moreover, a numerical method is developed based on three-dimensional solution of Navier–Stokes equations.
Findings
Effects of side ratio of triangular partitions (SR = 0.5, 1 and 2), Rayleigh number (103 < Ra < 105) and solid volume fraction (f = 0.002, 0.004 and 0.01 Vol.%) of nanofluid are investigated on both natural convection characteristic and volumetric entropy generation. The results show that the partitions can be a suitable method to control fluid flow and energy consumption, and three-dimensional solutions renders more accurate results.
Originality/value
The originality of this work is to study the three-dimensional natural convection and entropy generation of a stratified system.
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Yanzhong Wang and Bin Wei
The purpose of this study is to investigate wet multi-disc brake temperature field and optimal oil supply under continuous braking condition. The oil supply of wet multi-disc…
Abstract
Purpose
The purpose of this study is to investigate wet multi-disc brake temperature field and optimal oil supply under continuous braking condition. The oil supply of wet multi-disc brake has a direct impact on the drivability and fuel economy for tracked vehicles. Too small flow will result in the higher temperature and failure of brake while excessive one will lead to slow engagement increasing disengaged torque and the transmission efficiency could decline notably. The optimal oil supply and brake temperature field were obtained in this research.
Design/methodology/approach
This article investigated on the heat dissipation capability and optimal oil supply of the brake by the means of CFX model. The working condition was continuous braking and the lubricating and cooling factors were included in the model.
Findings
That the complex trends with increased oil flow is inconsistent with the traditional formula in which the effects of grooves were neglected. The fitting curve of optimal oil supply can predict various needed oil flow in various rotating speed and it provides a theoretical guidance for oil supply design.
Originality/value
Traditional empirical formula of heat transfer coefficient and Reynolds equation solved by different methods could be difficult to deal with the complex boundary conditions of wet multi-disc brake. CFX model can solve the problem of complex boundary condition. The optimal oil supply curve can provide a theoretical guidance for oil supply design.
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