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Article
Publication date: 26 December 2023

Yangtao Xing, Fugang Zhai, Shengnan Li and Peng Gui

This paper aims to study the deformation mechanism of polytetrafluoroethylene (PTFE) oil seal under a wide temperature range cycle.

Abstract

Purpose

This paper aims to study the deformation mechanism of polytetrafluoroethylene (PTFE) oil seal under a wide temperature range cycle.

Design/methodology/approach

This study categorizes the oil seal operation into three states: assembly, heating-up and cooling. The deformation equation for the oil seal is developed for each state, considering the continuity between them. The investigation of the oil seal’s deformation trends and mechanisms is performed using the ANSYS Workbench.

Findings

The assembling process results in a radial shrinkage of the skeleton, causing the centroid to move toward the axis. During heating-up, the outer diameter of the skeleton slightly expands, whereas the inner diameter sharply contracts toward the axis, leading to a further reduction in the centroid’s distance from the axis. Upon cooling, both the inner and outer diameters continue to contract toward the axis, causing the centroid to persist in its movement toward the axis. Consequently, after undergoing a heating-up and cooling cycle ranging from 20°C to 180°C, the outer diameter of the PTFE oil seal reduces by 0.92 mm from its original deformation, ensuring minimal contact between the skeleton and housing. As a result of the reduced static friction torque at the skeleton, the oil seal rotates along the shaft.

Originality/value

The deformation mechanism of PTFE oil seals under a wide temperature range cycle was investigated, aiming to address the concerns related to the rotation along the shaft and leakage.

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2023-0142/

Details

Industrial Lubrication and Tribology, vol. 76 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 4 August 2023

Zhiqi Liu, Tanghong Liu, Hongrui Gao, Houyu Gu, Yutao Xia and Bin Xu

Constructing porous wind barriers is one of the most effective approaches to increase the running safety of trains on viaducts in crosswinds. This paper aims to further improve…

Abstract

Purpose

Constructing porous wind barriers is one of the most effective approaches to increase the running safety of trains on viaducts in crosswinds. This paper aims to further improve the wind-sheltering performance of the porous wind barriers.

Design/methodology/approach

Improved delayed detached eddy simulations based on the k-ω turbulence model were carried out, and the results were validated with wind tunnel tests. The effects of the hole diameter on the flow characteristics and wind-sheltering performance were studied by comparing the wind barriers with the porosity of 21.6% and the hole diameters of 60 mm–360 mm. The flow characteristics above the windward and leeward tracks were analyzed, and the wind-sheltering performance of the wind barriers was assessed using the wind speed reduction coefficients.

Findings

The hole diameters affected the jet behind the wind barriers and the recirculation region above the tracks. Below the top of the wind barriers, the time-averaged velocity first decreased and then increased with the increase in the hole diameter. The wind barrier with the hole diameter of 120 mm had the best wind-sheltering performance for the windward track, but such barrier might lead to overprotection on the leeward track. The wind-sheltering performance of the wind barriers with the hole diameters of 240 mm and 360 mm was significantly degraded, especially above the windward track.

Originality/value

The effects of the hole diameters on the wake and wind-sheltering performance of the wind barriers were studied, by which the theoretical basis is provided for a better design of the porous wind barrier.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 11
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 10 May 2013

Xiong Liang, Bing Li, Xiaoyu Wu, Hongyan Shi, Kun Zeng and Yatao Wang

The purpose of this paper is to present a method for ultrasonically molding polymer powder in a micro plastic part mold. In the method, a printed circuit board (PCB) in which…

Abstract

Purpose

The purpose of this paper is to present a method for ultrasonically molding polymer powder in a micro plastic part mold. In the method, a printed circuit board (PCB) in which micro‐hole arrays are drilled is used as a micro cavity insert. With the utilization of ultrasonic vibration, the polymer powder, which is prefilled and compacted in a micro cavity, mutually generates great sliding friction heat so as to be rapidly plasticized and molded.

Design/methodology/approach

Micro carbide drill bits of which the diameters are 100.0 μm, 150.0 μm and 200.0 μm, respectively, are used for drilling the PCB to form a micro‐hole array insert. Next, two kinds of various ultra‐high molecule weight polyethylene (UHMW‐PE) powder with various grain diameters are directly filled into a charging barrel and a mold cavity with the micro‐hole array insert. Proper process parameters are set on ultrasonic plasticizing and molding equipment so that a molding test can be performed. The melt of UHMW‐PE can be rapidly filled into the cavity. Finally, micro‐column array plastic parts are successfully prepared.

Findings

The micro‐hole array PCB is a mold insert which is quite applicable for the ultrasonic molding of the powder in the mold. When a molding material is the coarse UHMW‐PE powder with the grain diameter of about 350 μm, the diameter replication rates of the micro‐column array plastic parts become good in order with the increased micro‐hole diameter of the PCB. When the fine UHMW‐PE powder with the grain diameter of about 80 μm is adopted, the diameter replication rates of the micro‐column array plastic parts become good in order with the decreased micro‐hole diameter of the PCB.

Originality/value

In this paper, the micro‐column array plastic parts with good replicability are successfully prepared by a technique for ultrasonically plasticizing and molding in the cavity. The technique can be applied to the fields of medical treatment, communication, optics, chemistry and so on, such as biological micro needle arrays, micro biological chips, optical memories, and micro chemical reaction chips.

Article
Publication date: 5 May 2015

Rafal P. Wojda and Marian K. Kazimierczuk

The purpose of this paper is threefold. First, an analytical model based on one-dimensional Dowell’s equation for computing ac-to-dc winding resistance ratio FR of litz wire is…

Abstract

Purpose

The purpose of this paper is threefold. First, an analytical model based on one-dimensional Dowell’s equation for computing ac-to-dc winding resistance ratio FR of litz wire is presented. The model takes into account proximity effect within the bundle and between bundle layers as well as the skin effect. Second, low- and medium-frequency approximation of Dowell’s equation for the litz-wire winding is derived. Third, a derivation of an analytical equation is given for the optimum strand diameter of the litz-wire winding independent on the porosity factor.

Design/methodology/approach

The methodology is as follows. First, the model of the litz-wire bundle is assumed to be a square shape. Than the effective number of layers in the litz wire bundle is derived. Second, the litz-wire winding is presented and an analytical equation for the winding resistance is derived. Third, analytical optimization of the strand diameter in the litz-wire winding is independent on the porosity factor performed, where the strand diameter is independent on the porosity factor. The boundary frequency between the low-frequency and the medium-frequency ranges for both solid-round-wire and litz-wire windings are derived. Hence, useful frequency range of both windings can be determined and compared.

Findings

Closed form analytical equations for the optimum strand diameter independent of the porosity factor are derived. It has been shown that the ac-to-dc winding resistance ratio of the litz-wire winding for the optimum strand diameter is equal to 1.5. Moreover, it has been shown that litz-wire winding is better than the solid-round-wire winding only in specific frequency range. At very high frequencies the litz-wire winding ac resistance becomes much greater than the solid-round-wire winding due to proximity effect between the strands in the litz-wire bundle. The accuracy of the derived equations is experimentally verified.

Research limitations/implications

Derived equations takes into account the losses due to induced eddy-currents caused by the applied current. Equations does not take into account the losses caused by the fringing flux, curvature, edge and end winding effects.

Originality/value

This paper presents derivations of the closed-form analytical equations for the optimum bare strand diameter of the litz-wire winding independent on the porosity factor. Significant advantage of derived equations is their simplicity and easy to use for the inductor designers.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 3
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 7 November 2019

William Pao and Zeeshan Qadir Memon

Excessive liquid carryover in T-junction presents a serious operational issue in offshore production platform. Slug flow and diameter ratio of T-junction are considered as two…

Abstract

Purpose

Excessive liquid carryover in T-junction presents a serious operational issue in offshore production platform. Slug flow and diameter ratio of T-junction are considered as two major factors causing liquid carryover. Regular and reduced T-junction are being used as partial phase separator but their efficiency is low. Converging T-junction with two distinct diameters (primary and secondary) in branch arm is used to improve the phase separation efficiency. The motivation is to combine specific feature of regular and reduced T-junction to increase separation efficiency of existing T-junction without involving too much operational workover. The purpose of this paper is to numerically evaluate the separation efficiency of a converging T-junction design. The present model and its methodology was validated with in-house experimental data for 3 inches diameter flow loop.

Design/methodology/approach

The slug flow regime was simulated using incompressible Eulerian mixture model coupled with volume of fluid method to capture the dynamic gas-liquid interface.

Findings

The analyses concluded that T-junction with primary-secondary branch arm diameters combination of 1.0-0.5 and 0.67-0.40 managed to achieve 95 per cent separation efficiency. The research also confirmed that over reduction of T-junction secondary diameter ratio below 0.2 will lead to decrease in separation efficiency.

Research limitations/implications

The present research is limit to air/water two-phase flow but the general results should be applicable for wider application.

Practical implications

The proposed design limited excessive workover and installation for current and existing T-junction. Hence, cutting down installation cost while improving the separation efficiency.

Social implications

The present research resulted in higher separation efficiency, cutting down production down time and lead to operational cost saving.

Originality/value

The present research proposes an original and new T-junction design that can increase phase separation efficiency to over 90 per cent. The finding also confirmed that there is a limitation whereby smaller diameter ratio T-junction does not always resulted in better separation.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 4 January 2016

Hui Yuen Peng, Mutharasu Devarajan, Teik Toon Lee and David Lacey

The purpose of this paper is to investigate the reliability of wire bonds with three varying ball bond diameters, which are ball bonded with three different sizes of gold wires in…

Abstract

Purpose

The purpose of this paper is to investigate the reliability of wire bonds with three varying ball bond diameters, which are ball bonded with three different sizes of gold wires in light-emitting diode (LED) package under high-temperature environment. In automotive applications, “lifted ball bond” issue is a potential critical point for LED device reliability, as the wire bonds are usually stressed under high operating temperature during their lifetime. Moreover, the reliability of wire bonds in recent LED production has fallen under scrutiny due to the practice of reducing wire diameters to cut down production costs.

Design/methodology/approach

Three gold wires with sizes of 2, 1.5 and 1 mm were ball bonded on the LED chip bond pad via thermosonic wire bonding method to produce three different ball bond diameters, that is, 140, 120 and 100 μm, respectively. The reliability of these wire bond samples was then studied by performing isothermal aging at 200°C for the time interval of 30, 100 and 500 hours. To validate hypotheses based on the experimental data, COMSOL Multiphysics simulation was also applied to study the thermal stress distribution of wire bond under an elevated temperature.

Findings

Experimental results show that the interfacial adhesion of wire bond degrades significantly after aging at 200°C for 500 hours, and the rate of interfacial degradation was found to be more rapid in the wire bond with smaller ball bond diameter. Experimental results also show that ball bonds randomly elongate along an axis and deforms into elliptical shapes after isothermal aging, and ball bonds with smaller diameters develop more obvious elongations. This observation has not been reported in any previous studies. Simulation results show that higher thermal stress is induced in the wire bond with the decrease of ball bond diameter.

Practical implications

The reliability study of this paper provides measurements and explanation on the effects of wire diameter downsizing in wire bonds for automotive application. This is applicable as a reliability reference for industries who intend to reduce their production costs. Other than that, the analysis method of thermal stresses using COMSOL Multiphysics simulations can be extended by other COMSOL Multiphysics users in the future.

Originality/value

To resolve “lifted ball bond” issue, optimization of the bond pad surface quality and the wire bond parameter has been studied and reported in many studies, but the influence of ball bond diameter on wire bond reliability is rarely focused. Moreover, the observation of ball bonds randomly elongate and deform more into elliptical shape, and ball bond with smaller diameter has the highest elongation after isothermal aging also still has not been reported in any previous studies.

Article
Publication date: 17 May 2021

Jesús Miguel Chacón, Miguel Ángel Caminero, Pedro José Núñez, Eustaquio García-Plaza and Jean Paul Bécar

Fused filament fabrication (FFF) is one of the most popular additive manufacturing (AM) technologies due to its ability to build thermoplastic parts with complex geometries at low…

Abstract

Purpose

Fused filament fabrication (FFF) is one of the most popular additive manufacturing (AM) technologies due to its ability to build thermoplastic parts with complex geometries at low cost. The FFF technique has been mainly used for rapid prototyping owing to the poor mechanical and geometrical properties of pure thermoplastic parts. However, both the development of new fibre-reinforced filaments with improved mechanical properties, and more accurate composite 3D printers have broadened the scope of FFF applications to functional components. FFF is a complex process with a large number of parameters influencing product quality and mechanical properties, and the effects of the combined parameters are usually difficult to evaluate. An array of parameter combinations has been analysed for improving the mechanical performance of thermoplastic parts such as layer thickness, build orientation, raster angle, raster width, air gap, infill density and pattern, fibre volume fraction, fibre layer location, fibre orientation and feed rate. This study aims to assess the effects of nozzle diameter on the mechanical performance and the geometric properties of 3D printed short carbon fibre-reinforced composites processed by the FFF technique.

Design methodology approach

Tensile and three-point bending tests were performed to characterise the mechanical response of the 3D printed composite samples. The dimensional accuracy, the flatness error and surface roughness of the printed specimens were also evaluated. Moreover, manufacturing costs, which are related to printing time, were evaluated. Finally, scanning electron microscopy images of the printed samples were analysed to estimate the porosity as a function of the nozzle diameter and to justify the effect of nozzle diameter on dimensional accuracy and surface roughness.

Findings

The effect of nozzle diameter on the mechanical and geometric quality of 3D printed composite samples was significant. In addition, large nozzle diameters tended to increase mechanical performance and enhance surface roughness, with a reduction in manufacturing costs. In contrast, 3D printed composite samples with small nozzle diameter exhibited higher geometric accuracy. However, the effect of nozzle diameter on the flatness error and surface roughness was of slight significance. Finally, some print guidelines are included.

Originality value

The effect of nozzle diameter, which is directly related to product quality and manufacturing costs, has not been extensively studied. The presented study provides more information regarding the dependence of the mechanical, microstructural and geometric properties of short carbon fibre-reinforced nylon composite components on nozzle diameter.

Article
Publication date: 3 September 2019

Ansar Ali Sk, Pardeep Kumar and Sandeep Kumar

The purpose of the study is to developed the effect of Nusselt number on impeller diameter in agitated vessel, which is beneficial to find out the heat transfer coefficient in the…

Abstract

Purpose

The purpose of the study is to developed the effect of Nusselt number on impeller diameter in agitated vessel, which is beneficial to find out the heat transfer coefficient in the process industry. A comparison has been done between the experimental and calculated Nusselt numbers with standard deviation found to be 8.03 per cent.

Design/methodology/approach

For studying the effect of impeller diameter on Nusselt Number, the heat transfer measurements were made with three different impellers of diameter. Although the diameter of impeller, Da shows its effect in Reynolds number, an attempt has been made to find the relationship between the impeller diameter and Nusselt number. A correlation between (NNuj/NPra1/3 NRea2/3) vs Da/DT and (NNuoc/NPra1/3 NRea2/3) vs Da/Dc in which data of three fluids [1, 2 and 4 per cent carboxy methyl cellulose solution of A type (CMC-A) solutions] have been plotted.

Findings

The heat transfer data for agitated Newtonian and non-Newtonian fluids have been successfully correlated by using the viscosity of the fluid evaluated at the impeller tip assuming a cylinder of diameter equal to that of impeller rotating in an infinite fluid. Data of 1, 2 and 4 per cent CMC-A, for three impeller diameters, have been correlated by equations. Using the above concepts of Reynolds and Prandtl numbers, Nusselt Numbers and Da/DT, it is also possible to correlate the available published data for other non-Newtonian fluids obtained with different impeller geometries.

Originality/value

A set up was made for studying the effect of impeller diameter, the heat transfer measurements were made with three impellers of diameter 7.5, 12.7 and 18.35 cm respectively. Although the diameter of impeller, Da shows its effect is Reynolds number, an attempt has been made to find the effect of Da/DT ratio on Nusselt number.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 18 June 2019

Ozge Celik and Recep Eren

Yarns of different types are unwound from bobbins in different processes like warping, weaving, doubling and re-winding. It is required that yarn tension remains constant during…

Abstract

Purpose

Yarns of different types are unwound from bobbins in different processes like warping, weaving, doubling and re-winding. It is required that yarn tension remains constant during unwinding in all these processes. Otherwise, it ends with product quality and process efficiency problems. The purpose of this paper is to investigate experimentally the effect of balloon length on yarn tension change with respect to bobbin diameter during unwinding in an attempt to obtain a minimum yarn tension variation.

Design/methodology/approach

An experimental set up was built. Bobbin diameter was measured by a laser sensor and yarn tension was measured by a single yarn tension sensor. Both sensor outputs were interfaced to a PC via a DAQ cad. A software program was developed in C programming language to read and record the tension and bobbin diameter simultaneously. Experimental study was conducted with three different balloon lengths for both continuous filament and spun yarns of four different yarn numbers and five different unwinding speeds.

Findings

Results showed that yarn tension change with bobbin diameter was affected in different ways with balloon length depending on yarn number, unwinding speed and yarn type.

Originality/value

Available literature on the effect of balloon length on yarn tension bobbin diameter relation is limited and measurements were generally conducted for three different bobbin diameters. Yarn tension bobbin diameter relation is obtained in this research for at least eight different diameters and more for three different balloon lengths covering practical application ranges. The results obtained can be used in the design of tension control system for warping and winding machines as well as for setting these machines for optimum efficiency.

Details

International Journal of Clothing Science and Technology, vol. 31 no. 4
Type: Research Article
ISSN: 0955-6222

Keywords

Article
Publication date: 5 December 2019

Mariusz Deja and Dawid Zielinski

The purpose of this study is to evaluate the geometric quality of small diameter holes in parts printed by direct metal laser sintering (DMLS) technology. An in-process optical…

Abstract

Purpose

The purpose of this study is to evaluate the geometric quality of small diameter holes in parts printed by direct metal laser sintering (DMLS) technology. An in-process optical inspection method is proposed and assessed during a pilot study. The influence of the theoretical hole diameter assumed in a computer-aided design (CAD) system and the sample thickness (hole length) on the hole clearance was analyzed.

Design/methodology/approach

The samples are made of two different materials: EOS MaragingSteel MS1 and aluminium alloy EOS Aluminium consisted of straight through holes of different diameters and lengths. Dimensional and shape accuracy of the holes were determined with the use of the image processing software and the computer analysis of two-dimensional (2-D) images. The definition of the equivalent hole diameter was proposed to calculate the hole clearance. Feret’s diameters were determined for the evaluation of the shape accuracy.

Findings

The dependency between the equivalent hole diameter and the theoretical diameter was approximated by the linear function for a specific sample thickness. Additionally, a general empirical model for determining the hole clearance was developed, allowing for calculating the equivalent hole diameter as a function of a sample thickness and a theoretical hole diameter.

Practical implications

Developed functions can be used by designers for a proper assignment of a hole diameter to achieve the required patency. The relevant procedures and macros based on proposed empirical models can be embedded in CAD systems to support the designing process.

Originality/value

The analysis of the geometric quality of the holes in parts printed by DMLS was based on the computer analysis of 2-D images. The proposed method of assessing the shape accuracy of straight through holes is relatively cheap, is widely available and can be applied to the features of other shapes produced by three-dimensional printing.

Details

Rapid Prototyping Journal, vol. 26 no. 2
Type: Research Article
ISSN: 1355-2546

Keywords

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