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1 – 10 of over 2000Batuhan Özakın, Bilal Çolak and Naci Kurgan
The last stage of the cold rolling process is skin-pass rolling and one of its most significant goals is to obtain appropriate topography on the surface of the sheet steel used…
Abstract
Purpose
The last stage of the cold rolling process is skin-pass rolling and one of its most significant goals is to obtain appropriate topography on the surface of the sheet steel used extensively such as in automotive industry. The purpose of this paper is to investigate the effect of thickness change and various reduction ratios on roughness transfer of DC04 grade sheet material.
Design/methodology/approach
DC04 grade sheet materials with different reduction ratios and several thicknesses were subjected to skin-pass rolling process in the rolling equipment with a two-high roll. Some roughness parameters were determined as a result of roughness measurements from the surfaces of roughened sheet materials.
Findings
While the roughness transfer is higher in 1-mm thick material in reduction ratios up to 430 micrometers; in reduction ratios above 430 micrometers, it is higher for 1.5-mm thick materials. As the reduction ratio increases in DC04 grade sheet materials, the homogeneity of the roughness distribution in 1-mm thickness sheet material deteriorates, while the roughness distribution in 1.5-mm thickness sheet material is more homogeneous.
Originality/value
This paper demonstrates how material thickness and reduction ratio affect the roughness transfer in skin-pass rolling. The results obtained can be used by optimizing in manufacturing processes.
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Ting Xie, Junjie Lai and Huaping Yang
This paper aims to simulate the effect of counterface roughness on the friction transfer and wear of the polymer material sliding against steel.
Abstract
Purpose
This paper aims to simulate the effect of counterface roughness on the friction transfer and wear of the polymer material sliding against steel.
Design/methodology/approach
The dynamic process of friction transfer and wear of polytetrafluoroethylene (PTFE) sliding against steel 45 was simulated by the software of particle flow code in two dimensions and a discrete element method. The effect of the counterface roughness was considered in the simulation. The definitions of the transferred particle and worn particle were given.
Findings
The simulation results showed that a transferred particle layer was formed on the surface of steel 45 during friction. The wear rate of PTFE can be effectively reduced by the formation of the transferred particle layer. The formation and stability of this particle layer is certainly affected by the counterface roughness (Rz). In this paper, the transferred particle numbers increased with Rz increase. And so did the worn particle numbers. However, there was little effect of Rz on the wear rate of PTFE.
Originality/value
The dynamic process of the friction transfer and wear of the PTFE/ steel 45 friction pair was reproduced at the micro-level. Then, the transfer and wear were quantitatively exhibited. The relations between the transfer or wear and counterface roughness was simulated and discussed. It will be meaningful for the optimization and effective control of friction and wear of polymer/metal sliding system.
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Prabhugouda Mallanagouda Patil, S.H. Doddagoudar and P.S. Hiremath
The purpose of this paper is to present the surface roughness effects on mixed convection nanofluid flow with liquid hydrogen/liquid nitrogen diffusion.
Abstract
Purpose
The purpose of this paper is to present the surface roughness effects on mixed convection nanofluid flow with liquid hydrogen/liquid nitrogen diffusion.
Design/methodology/approach
The small parameter (α) is considered along with the frequency parameter n to study the surface roughness. The non-similar transformations are used to reduce the dimensional non-linear partial differential equations into dimensionless form, and then, the resulting equations are solved with the help of Newton’s Quasilinearization technique and the finite difference scheme.
Findings
The impacts of several dimensionless parameters such as Brownian diffusion parameter (Nb), thermophoresis parameter (Nt), small parameter (α), etc., are analyzed over various profiles as well as gradients. Also, the investigation is carried out for in presence and absence of nanoparticles. The influence of surface roughness is sinusoidal in nature and is more significant near the origin in case of skin-friction coefficient. The addition of nanoparticles enhances the skin-friction coefficient and reduces the Nusselt number, while its effects are not noticeable in case of mass transfer rates. The presence of suction/blowing, respectively, enhances/decreases the Sherwood number pertaining to the liquid hydrogen.
Practical implications
The results of the present analysis are expected to be useful for the design engineers of polymer industries in manufacturing good quality polymer sheets.
Originality/value
To the best of the author’s knowledge, no such investigation has been carried out in the literature.
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Zheng Bo, Qi Zhao, Xiaorui Shuai, Jianhua Yan and Kefa Cen
– The purpose of this paper is to provide a quantitative assessment on the effect of wall roughness on the pressure drop of fluid flow in microchannels.
Abstract
Purpose
The purpose of this paper is to provide a quantitative assessment on the effect of wall roughness on the pressure drop of fluid flow in microchannels.
Design/methodology/approach
The wall roughness is generated by the method of random midpoint displacement (RMD) and the lattice Boltzmann BGK model is applied. The influences of Reynolds number, relative roughness and the Hurst exponent of roughness profile on the Poiseuille number are investigated.
Findings
Unlike the smooth channel flow, Reynolds number, relative roughness and the Hurst exponent of roughness profiles play critical roles on the Poiseuille number Po in rough microchannels. Modeling results indicate that, in rough microchannels, the rough surface configuration intensifies the flow-surface interactions and the wall conditions turn to dominate the flow characteristics. The perturbance of the local flows near the channel wall and the formation of recirculation regions are two main features of the flow-surface interactions.
Research limitations/implications
The fluid flow in parallel planes with surface roughness is considered in the current study. In other words, only two-dimensional fluid flow is investigated.
Practical implications
The LBM is a very useful tool to investigate the microscale flows.
Originality/value
A new method (RMD) is applied to generate the wall roughness in parallel plane and LBM is conducted to investigate the pressure drop characteristics in rough microchannels.
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This paper aims to investigate the effect of paper properties (whiteness, gloss and roughness) on colour laser printing quality. Paper characteristics have a significant influence…
Abstract
Purpose
This paper aims to investigate the effect of paper properties (whiteness, gloss and roughness) on colour laser printing quality. Paper characteristics have a significant influence on print quality and are crucial variables for predicting and reproducing colour.
Design/methodology/approach
Six kinds of paper with different properties were selected and the effects of the paper characteristics on the printed paper were studied. Samples were printed with cyan, magenta and yellow toner with a laser printer under identical conditions. The papers and printed papers were evaluated with atomic force microscope, scanning electron microscope, gloss-meter, spectrophotometer and densitometer.
Findings
Results showed that print quality is statistically dependent on paper type, and the average optical density of printed paper varied for different papers. Furthermore, the increase in the roughness and gloss of the papers in comparison to whiteness more significantly affected the optical density of paper by reducing it.
Practical implications
To achieve high-quality print, laser printing paper and toner require controlled characteristics.
Originality/value
For the first time, the present study evaluated the influence of paper properties on the quality of colour laser printing.
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Nandkishor Sah and Mohan Jagadeesh Kumar Mandapati
Use of packed beds, enhanced tubes, nano-fluids and artificial ribs are few passive techniques to increase heat transfer in solar air heaters (SAHs). Artificial ribs attached to…
Abstract
Purpose
Use of packed beds, enhanced tubes, nano-fluids and artificial ribs are few passive techniques to increase heat transfer in solar air heaters (SAHs). Artificial ribs attached to the absorber plate of the SAH will enhance the turbulence near the plate. Experimental analyses are conducted to find the thermal performance of SAH with ribs of regular geometries including rectangular, semi-circular and triangular in cross section. This paper aims to present the improvement in thermal performance of SAH with modified-arc.
Design/methodology/approach
Absorber plates are designed with ribs of rectangular, triangular, semi-circular and modified-arc in cross-section using existing data in literature. Physical dimensions of the ribs are designed by adapting procedure from literature. Absorber plates are manufactured with ribs and coated with blackboard paint and fixed to the existing SAH. Experiments are conducted with a variable-speed blower fixed to the inlet section of the SAH, which is used to supply air at different mass flow rates in a range between 0.495 and 0.557 kg/min.
Findings
Efficiency is found to be a strong function of mass flow rate of air through the SAH from the present experimental investigations. It was found that use of modified-arc ribs enhanced the efficiency of SAH by 105.35 per cent compared to SAH with plane absorber plate. Efficiency of SAH with modified-arc ribs is found to be higher by 24.43, 45.61 and 63.21 per cent, respectively, for SAH with semi-circular, rectangular and triangular arc ribs on its absorber plate.
Research limitations/implications
Experiments on SAH are conducted during daytime from 9:00 am to 5:00 pm in open atmospheric conditions. Solar intensity is continuously changing during the experimentation from morning to evening. Calculations are made based on the observations with average values of solar intensity and temperature readings. More accurate values of SAH efficiency can be obtained with constant heat supply to the absorber plate by simulating the experimental setup in indoor conditions. Temperature and flow rate observations could be more accurate with sophisticated instrumentation rather than using simple thermocouples and orifice meters.
Social implications
SAHs are basically used to supply hot air for both rural and industrial applications. These are used for crop drying, preheating of air, removal of moisture from leather, chemicals, etc. Conventionally, formers in India are using open sun drying to remove moisture from agricultural products. In this method, the moisture can be removed up to a level of 20 to 25 per cent. Use of SAH can remove moisture up to below 5 per cent and process is clean without reducing the quality of agricultural products. Enhancing the efficiency of SAHs will surely increase its usage by formers for crop drying.
Originality/value
Use of artificial ribs on absorber plate of SAH is most economical among many of the active and passive techniques. Numerical and experimental investigations are found in literature with regular cross-sectional ribs, including rectangular, triangular and semi-circular. The present work proposed new shape of the ribs named as modified-arc, which was not presented in the literature. Experimental analysis proved that the use of modified-arc makes the SAH more efficient in heat transfer.
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Xiping Yang, Yonghong Fu and Jinghu Ji
The purpose of this paper is to find the influence of surface bump texture combination characteristics on friction-wear properties so as to provide a basis for the selection of…
Abstract
Purpose
The purpose of this paper is to find the influence of surface bump texture combination characteristics on friction-wear properties so as to provide a basis for the selection of the bump texture combination scheme on the surface of the roll.
Design/methodology/approach
In this paper, six groups of different bump texture combination characteristics and their processing methods are introduced, of which three groups are regular distribution with different spacing and three groups are random distribution with different spacing. Then the effect of bump textures with different spacing, regular and random distribution on friction-wear properties was studied by ring block friction-wear experiments.
Findings
The results show that the friction coefficient of random distribution texture surface is lower than that of regular texture surface under the same spacing condition. In the regular distribution, the friction coefficient decreases with the increase of texture spacing. In the random distribution, the friction coefficient increases at first and then decreases with the increase of texture spacing. In addition, the wear resistance of textured surface is significantly higher than that of smooth surface because of the higher microhardness of the textured area. The attenuation ratio of textured surface roughness decreases with the increase of the distance between adjacent textures.
Originality/value
At present, the research on roller surface friction-wear is mainly based on the change of the overall surface roughness. However, there are few reports on the influence of the combination characteristics of laser bump texture on friction-wear from the microscopic scale.
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Matthew Wong, Sozon Tsopanos, Chris J. Sutcliffe and Ieuan Owen
To fabricate and characterise novel heat sinks manufactured by selective laser melting (SLM). The investigation explores features of SLM produced heat sinks that may be exploited…
Abstract
Purpose
To fabricate and characterise novel heat sinks manufactured by selective laser melting (SLM). The investigation explores features of SLM produced heat sinks that may be exploited to improve their heat transfer capability.
Design/methodology/approach
The study was conducted on heat sinks manufactured from 316L stainless steel and aluminium 6061. The heat transfer devices' thermal and pressure drop performances were determined by experimental test.
Findings
The research demonstrates the performance enhancements that can be realised by using novel heat sink designs, fabricated by SLM, over conventional pin fin arrays. aluminium 6061 is used with the process to illustrate the improvement in heat transfer provided by higher conductivity feedstock materials.
Research limitations/implications
Although the manufacturing technique is still in the development stage and the heat transfer devices that have so far been manufactured should not be considered optimal, the potential for creative new designs and applications is clear. This study highlights the need to develop the SLM process parameters to allow the repeatable production of heat transfer devices from higher conductivity metals with controllable surface finishes.
Originality/value
This paper outlines the design issues and performance of novel heat transfer devices fabricated using SLM. A new material, aluminium 6061, is introduced to the family of materials that can be processed with SLM and example heat sinks are tested.
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Rongguang Jia, Masoud Rokni and Bengt Sundén
A numerical investigation to determine the velocity and heat transfer characteristics of multiple impinging slot jets in rib‐roughened channels in the presence of cross‐flow has…
Abstract
A numerical investigation to determine the velocity and heat transfer characteristics of multiple impinging slot jets in rib‐roughened channels in the presence of cross‐flow has been carried out. Fluid flow is modeled using an explicit algebraic stress model. A simple eddy diffusivity and a generalized gradient diffusion hypothesis are applied for the modeling of turbulent heat fluxes. The computations are validated against available experimental fluid flow and heat transfer data. Different size and arrangement of jets and ribs are considered in detail, while the Reynolds numbers of a jet and the channel inlet are fixed at 6,000 and 14,000, respectively. Results show that the ratio (B/W) between the size of the jets and ribs is most important. An explanation is that the ribs inhibit the motion of eddies by preventing them from coming very close to the surface when B/W is low, e.g. B/W = 1, although the ribs will increase the turbulence intensity. This blockage limited the heat transfer enhancement effect of the ribs and impinging jets.
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Jung Hwan Park, Jin Oh Chung and Hyang Rae Kim
The purpose of this paper is to investigate the friction coefficients of aramid and acrylic fibers on brake pads.
Abstract
Purpose
The purpose of this paper is to investigate the friction coefficients of aramid and acrylic fibers on brake pads.
Design/methodology/approach
Fiber components used in the present pads are aramid and acrylic fibers, respectively, while keeping other components, such as binders, lubricants, abrasives, fillers the same. Disk FC25 and disk FC17 are used for rotor rubbing test to investigate the friction coefficients with brake pads. The pads are tested by 1/5 scale brake dynamometer, and test mode is modified JASO C406‐P1. The results are analyzed with the friction coefficient and the temperature, transfer film, roughness, and photomicrograph of worn surface on rotors.
Findings
The friction coefficient was mainly determined by the pad material rather than the rotor material, and pads made of aramid fiber had high‐friction coefficient, while pads made of acrylic fiber had low‐friction coefficient, especially under high temperature. Temperature change during braking process was directly related to the initial speed only, and was indifferent to materials or decelerations imposed. In the fade test, the reversal of friction coefficients between the aramid fiber and acrylic fiber pads is determined by the amount of remained amount of respective fiber above 520°C.
Originality/value
Effect of different fiber components, aramid and acrylic fibers, on friction characteristics of pad is sought. Reversal of friction coefficients is determined by the thermal stability of fibers used for pads.
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