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Article
Publication date: 27 September 2018

Recep Eren, Ozge Celik, Fatih Suvari and Seyit Ali Koksal

Sectional warping is the most widely used warp preparation process in weaving. Winding all warp sections with the same length and same tension is a key factor for a good…

Abstract

Purpose

Sectional warping is the most widely used warp preparation process in weaving. Winding all warp sections with the same length and same tension is a key factor for a good quality warp preparation. It is required that winding thickness (increase in radius due to warp winding) remains the same within and between warp sections. The purpose of this paper is to investigate winding thickness variations within and between warp sections, which can lead to quality problems in woven fabrics.

Design/methodology/approach

A measurement system is developed and then an experimental investigation into winding thickness variations is carried out. Winding thickness is measured with respect to number of drum revolutions using a laser sensor with 20 microns resolution. The number of drum revolutions and drum angular position are measured by an incremental encoder. Both sensors are mounted on an industrial sectional warping machine. A real-time software written in C programming language collects and records the data for all sections of warp with respect to drum number of revolutions and then results are evaluated to determine winding thickness variations.

Findings

Results show that warp sheet thickness starts with a higher value and it decreases up to around 30 drum revolutions and then it remains constant or decreases very slightly which can be considered as insignificant from practical point of view. Warp sheet thickness (i.e. thickness of one warp layer) fluctuates within each section up to 10 percent CV with five drum revolutions average warp sheet thickness. There are also warp sheet thickness variations between warp sections up to 3 mm.

Originality/value

Considering the short of practical research results on winding thickness variations in the literature, results of this study will be an original contribution to understanding winding thickness variation level. Also, results presented in this paper can be used to develop control algorithms for thickness control in sectional warping machines.

Details

International Journal of Clothing Science and Technology, vol. 30 no. 6
Type: Research Article
ISSN: 0955-6222

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Article
Publication date: 18 September 2009

Jianbiao Pan, Tzu‐Chien Chou, Jasbir Bath, Dennis Willie and Brian J. Toleno

The purpose of this paper is to investigate the effects of reflow time, reflow peak temperature, thermal shock and thermal aging on the intermetallic compound (IMC…

Abstract

Purpose

The purpose of this paper is to investigate the effects of reflow time, reflow peak temperature, thermal shock and thermal aging on the intermetallic compound (IMC) thickness for Sn3.0Ag0.5Cu (SAC305) soldered joints.

Design/methodology/approach

A four‐factor factorial design with three replications is selected in the experiment. The input variables are the peak temperature, the duration of time above solder liquidus temperature (TAL), solder alloy and thermal shock. The peak temperature has three levels, 12, 22 and 32°C above solder liquidus temperatures (or 230, 240 and 250°C for SAC305 and 195, 205, and 215°C for SnPb). The TAL has two levels, 30 and 90 s. The thermally shocked test vehicles are subjected to air‐to‐air thermal shock conditioning from −40 to 125°C with 30 min dwell times (or 1 h/cycle) for 500 cycles. Samples both from the initial time zero and after thermal shock are cross‐sectioned. The IMC thickness is measured using scanning electron microscopy. Statistical analyses are conducted to compare the difference in IMC thickness growth between SAC305 solder joints and SnPb solder joints, and the difference in IMC thickness growth between after thermal shock and after thermal aging.

Findings

The IMC thickness increases with higher reflow peak temperature and longer time above liquidus. The IMC layer of SAC305 soldered joints is statistically significantly thicker than that of SnPb soldered joints when reflowed at comparable peak temperatures above liquidus and the same time above liquidus. Thermal conditioning leads to a smoother and thicker IMC layer. Thermal shock contributes to IMC growth merely through high‐temperature conditioning. The IMC thickness increases in SAC305 soldered joints after thermal shock or thermal aging are generally in agreement with prediction models such as that proposed by Hwang.

Research limitations/implications

It is still unknown which thickness of IMC layer could result in damage to the solder.

Practical implications

The IMC thickness of all samples is below 3 μm for both SnPb and SAC305 solder joints reflowed at the peak temperature ranging from 12 to 32°C above liquidus temperature and at times above liquidus ranging from 30 to 90 s. The IMC thickness is below 4 μm after subjecting to air‐to‐air thermal shock from −40 to 125°C with 30 min dwell time for 500 cycles or thermal aging at 125°C for 250 h.

Originality/value

The paper reports experimental results of IMC thickness at different thermal conditions. The application is useful for understanding the thickness growth of the IMC layer at various thermal conditions.

Details

Soldering & Surface Mount Technology, vol. 21 no. 4
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 December 1999

C.A. Wilson, B.E. Niven and R.M. Laing

The purposes of this work were to determine: whether thickness of single layers can be used to accurately predict thickness and thermal resistance of multiple layer…

Abstract

The purposes of this work were to determine: whether thickness of single layers can be used to accurately predict thickness and thermal resistance of multiple layer assemblies; and to identify variables affecting the total thickness (i.e. textile plus air layers) of bedding during simulated use. Thickness was determined when: materials were flat; and arranged over an infant manikin simulating use. Thermal resistance was measured using a guarded‐hotplate similar to that specified in ISO 11092:1993(E). During simulated use, the site of measurement, body position, tucking, and product type significantly affected thickness of bedding. Equations for predicting thickness and thermal resistance (dry) of multiple‐layer materials are described. While it was possible to predict thickness and thermal resistance of flat bedding from estimated values, extrapolation to bedding during simulated use was considered inappropriate, with significant differences of over 1,000 per cent.

Details

International Journal of Clothing Science and Technology, vol. 11 no. 5
Type: Research Article
ISSN: 0955-6222

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Article
Publication date: 1 April 1993

E. HINTON, S.M.B. AFONSO and N.V.R. RAO

The optimization of variable thickness plates and shells is studied. In particular, three types of shell are considered: hyperbolic paraboloid, conoid and cylindrical…

Abstract

The optimization of variable thickness plates and shells is studied. In particular, three types of shell are considered: hyperbolic paraboloid, conoid and cylindrical shell. The main objective is to investigate the optimal thickness distributions as the geometric form of the structure changes from a plate to a deep shell. The optimal thickness distribution is found by use of a structural optimization algorithm which integrates the Coons patch technique for thickness definition, structural analysis using 9‐node Huang‐Hinton shell elements, sensitivity evaluation using the global finite difference method and the sequential quadratic programming method. The composition of the strain energy is monitored during the optimization process to obtain insight into the energy distribution for the optimum structures. Several benchmark examples are considered illustrating optimal thickness variations under different loading, boundary and design variable linking conditions.

Details

Engineering Computations, vol. 10 no. 4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 June 2005

Sven Lamprecht

This paper describes the different thickness measurement techniques that enable reliable thickness assessments, and the determination of the recommended immersion tin…

Abstract

Purpose

This paper describes the different thickness measurement techniques that enable reliable thickness assessments, and the determination of the recommended immersion tin thickness for lead‐free soldering.

Design/methodology/approach

Immersion tin layers were prepared with systematically varying layer thicknesses. The samples were annealed at different reflow profiles, used in assembly for tin/silver/copper (SAC‐alloy) soldering. The layers were characterized with X‐ray fluorescence, electrochemical stripping coulometry, and by examining the cross sections using a scanning electron microscope. The solderability of the samples was determined with a solder balance (Solderability Tester Menisco ST60) using a SAC‐alloy (melting point 217°C) with T(max) at ΔT=28°C and ΔT=43°C above melting.

Findings

If all pure tin is converted into the Sn/Cu IMC, so that no pure tin is left as solderable layer, the wetting behaviour will decrease dramatically. Especially for multiple soldering processes, two times reflow followed by wave soldering, it is essential to have a pure tin layer covering the Sn/Cu IMC before going to the final soldering process. The required amount of residual pure tin over the Sn/Cu IMC is detailed in several papers. It is stated that a minimum of 0.2 μm of pure tin over the Sn/Cu IMC is absolutely necessary to ensure reliable wetting and solder joint formation. With the current immersion tin thickness recommendation of 1 μm, based on the needs of lead containing solder pastes, a residual pure tin layer will not be evident or thick enough to ensure reliable assembly for multiple soldering with lead‐free temperature profiles.

Originality/value

Helps to enable reliable thickness assessments, and the determination of the recommended immersion tin thickness for lead‐free soldering.

Details

Circuit World, vol. 31 no. 2
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 1 December 2005

Y. Zhang

To make a derivation of the load‐carrying capacity of elastohydrodynamic lubrication for special operating conditions, i.e. extremely heavy loads or extremely low rolling…

Abstract

Purpose

To make a derivation of the load‐carrying capacity of elastohydrodynamic lubrication for special operating conditions, i.e. extremely heavy loads or extremely low rolling speeds based on the Newtonian fluid model by taking the Grubin‐type EHL inlet zone analysis, justify the load‐carrying capacity of elastohydrodynamic lubrication film in these operating conditions, and propose future trends of the research in EHL and mixed EHL based on the obtained results in the present paper.

Design/methodology/approach

A Grubin‐type EHL inlet zone analysis is carried out for the isothermal EHL of line contacts in special operating conditions, i.e. extremely heavy loads or extremely low rolling speeds based on the Newtonian fluid model. Comparison is made between the central EHL film thickness in line contacts, respectively, predicted by conventional EHL theories and accurately predicted from the present analysis for these operating conditions. An interpretation is made for the EHL film thickness in these operating conditions by taking the approach of the transportation and flow of the fluid through elastohydrodynamic contact when the EHL film is, respectively, thick and molecularly thin in the Hertzian zone. Conclusions are drawn on the load‐carrying capacity of EHL, EHL contact regimes and mixed EHL regimes in these operating conditions.

Findings

The present EHL inlet zone analysis shows that the EHL film thickness in the Hertzian zone is on the nanometer scale and the lubricant is non‐continuum across the film thickness in the Hertzian zone at relatively heavy loads in line contact EHL when the dimensionless rolling speed is lower than the dimensionless characteristic rolling speed Uch=0.0372W1.50/G. In this case, the central EHL film thickness in line contact EHL predicted by the conventional EHL theory may be several orders of magnitudes higher than that accurately predicted. This difference may be greater for heavier loads.The present results for line contact EHL based on the Newtonian fluid model show that in line contact EHL, for relatively heavy loads and the dimensionless rolling speed lower than the dimensionless characteristic rolling speed Uch=0.0372W1.50/G, the EHL analysis needs to further incorporate the lubricant non‐continuum effect across the film thickness in part of the lubricated area to investigate the EHL film thickness and the EHL film pressure in the contact in this very low film thickness condition; only the results based on such an analysis are believable for the EHL stage where the lubricant film thickness in the Hertzian zone approaches to zero and then vanishes; the results for EHL based on the Newtonian fluid model is unable to conclude that the EHL film thickness in the Hertzian zone is zero and dry contact occurs between the contact surfaces in EHL in any operating condition for ignoring the lubricant non‐continuum regime governing the EHL stage preceding the occurrence of the zero lubricant film thickness in EHL.

Practical implications

A very useful source of information for academic scientists, engineers and tribologists who are engaged in the study and application of the theory of elastohydrodynamic lubrication.

Originality/value

A derivation is first carried out for the isothermal EHL of line contacts in extremely heavy loads or extremely low rolling speeds by taking the Grubin‐type EHL inlet zone analysis by the present paper. Results and conclusions on the load‐carrying capacity of EHL in these operating conditions are first strict and thus convincing. These results are also original in clarifying the future trends of the researches in EHL and mixed EHL.

Details

Industrial Lubrication and Tribology, vol. 57 no. 6
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 22 June 2010

Li‐Ming Chu

The purpose of this paper is to explore the pure squeeze thin film elastohydrodynamic lubrication (TFEHL) motion of circular contacts with adsorption layers attached to…

Abstract

Purpose

The purpose of this paper is to explore the pure squeeze thin film elastohydrodynamic lubrication (TFEHL) motion of circular contacts with adsorption layers attached to each surface under constant load condition. The proposed model can reasonably calculate the pressure distributions, film thicknesses, normal squeeze velocities, and effective viscosities during the pure squeeze process under thin film lubrication.

Design/methodology/approach

The transient modified Reynolds equation is derived in polar coordinates using viscous adsorption theory. The finite difference method and the Gauss‐Seidel iteration method are used to solve the transient modified Reynolds equation, the elasticity deformation equation, load balance equation, and lubricant rheology equations simultaneously.

Findings

The simulation results reveal that the thickness of the adsorption layer and the viscosity ratio significantly influence the lubrication characteristics of the contact conjunction in the thin film regime. In additional, the turning points in the film thickness which distinguish thin film lubrication from elastohydrodynamic lubrication curve is found. In thin film region, the effective viscosity predicted by present model is better than that predicted by traditional elastohydrodynamic theory.

Originality/value

The paper develops a numerical method for general applications with adsorption layers attached to each surface to investigate the pure squeeze action in a TFEHL spherical conjunction under constant load condition.

Details

Industrial Lubrication and Tribology, vol. 62 no. 4
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 1 March 2013

Bo Gao, Ling Tong and Xun Gong

The purpose of this paper is to study and discuss the effects of the finite metallisation thickness and conductivity on the properties of microstrip lines.

Abstract

Purpose

The purpose of this paper is to study and discuss the effects of the finite metallisation thickness and conductivity on the properties of microstrip lines.

Design/methodology/approach

Effective dielectric constant and attenuation constant of microstrip lines with finite metallization thickness and finite conductivity are analyzed by the method of lines. The experimental results are obtained by using Vector Network Analyzer and the 3680 V Universal Test Fixture of Anritsu.

Findings

The strip thickness has a great impact on the attenuation constant of the microstrip lines. The effects can be divided into three parts by the relationship between strip thickness (t) and skindepth (δ). When t<δ, the attenuation constant will decrease rapidly as the strip thickness increase. When δ < t<2δ, the attenuation constant still decrease rapidly as the strip thickness increase, but the slope of the curve will be smaller. When 2δ < t, the effects of the strip thickness will become insignificant and the attenuation constant still decrease slowly as the strip thickness increase.

Originality/value

This paper presents some useful principles about the effects of the finite metallization thickness and finite conductivity in microstrip lines. The reasons for these effects are discussed by analyzing the longitudinal electric field distribution in the strip. Finally, some experimental results are given to verify these principles.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 32 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 16 September 2021

Juan Manuel Vázquez Martínez, David Piñero Vega, Jorge Salguero and Moises Batista

The evaluation of novel materials such as the acrylonitrile styrene acrylate (ASA) for tribological and mechanical conditions can provide a structural protection against…

Abstract

Purpose

The evaluation of novel materials such as the acrylonitrile styrene acrylate (ASA) for tribological and mechanical conditions can provide a structural protection against the environmental and wear effects that results in the long-term integrity of the 3 D printed parts. Results of the experimental stage are intended to identify the influence of the printing conditions on the functional characteristics of ASA parts that results in variations of the friction coefficient, wear rate and tensile response. In addition, this study aims to highlight the relevance of printing parameters to avoid the use of chemical post-processing stages, increasing the performance and sustainability of the process.

Design/methodology/approach

In this research, an evaluation of the influence of printing parameters of layer thickness and temperature on the mechanical and tribological response have been carried out for ASA specimens manufactured by fused filament fabrication technology. For this purpose, a range of three different values of thickness of fused layer and three different printing temperatures were combined in the manufacturing process of tests samples. Mechanical behavior of the printed parts was evaluated by standard tensile tests, and friction forces were measured by pin-on-disk tribological tests against steel spheres.

Findings

Higher layer thickness of the printed parts shows lower resistance to tribological wear effects; in terms of friction coefficient and wear rate, this type of parts also presents lower tensile strength. It has been detected that mechanical and tribological behavior is highly related to the micro-geometrical characteristics of the printed surfaces, which can be controlled by the manufacturing parameters. Under this consideration, a reduction in the coefficient of friction near to 65% in the average value was obtained through the variation of the layer thickness of printed surfaces.

Originality/value

This research aims to fill a gap in the scientific literature about the use of specific additive manufacturing materials under dynamic contact. This paper is mainly focused on the influence of the manufacturing parameters on the tribological and mechanical behavior of a weather resistant polymer (ASA).

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Article
Publication date: 23 June 2021

Kamran Kardel, Ali Khoshkhoo and Andres L. Carrano

The purpose of this paper is to investigate the effects of layer thickness, aspect ratio, part thickness and build orientation on distortion to have a better understanding…

Abstract

Purpose

The purpose of this paper is to investigate the effects of layer thickness, aspect ratio, part thickness and build orientation on distortion to have a better understanding of its behavior in material jetting technology.

Design/methodology/approach

Specimens with two layer thicknesses (14 and 28 µm) were printed in two aspect ratios (2:1) and (10:1), four thickness values (1, 2, 3 and 4 mm) and three build orientations (45d, XY and YX) and scanned with a wide-area 3D surface scanner to quantify distortion. The material used to build the test specimens was a commercially available resin, VeroWhitePlus RGD835.

Findings

The results of this study showed that all printed specimens by material jetting 3D printers had some level of distortion. The 1-mm thickness specimens, for both layer thicknesses of 14 µm and 28 µm, showed a wide range of anomalies including reverse coil set (RCS), reverse cross bow (RCB), cross bow (CB), wavy edge (WE) and some moderate twisting (T). Similar occurrences were observed for the 2-mm thickness specimens as there were RCS, WE, RCB and T anomalies that show the difference between the thinner specimens (1- and 2-mm) with the thicker ones (3- and 4-mm). In both 3- and 4-mm thickness specimens, there was more consistency in terms of distortion with mainly RCS and RCB anomalies. In total, six different types of flatness anomalies were found to occur with the following incidences: reverse coil set (91 specimens, 63.19%), reverse cross bow (50 specimens, 34.72%), wavy edge (23 specimens, 15.97%), twist (19 specimens, 12.50%), coil set (11 specimens, 7.64%) and cross bow (7 specimens, 4.86%).

Originality/value

This study expands the research on how the preprocess parameters such as layer thickness and build orientation and the geometrical parameters such as part thickness and aspect ratio cause dimensional distortion. Distortion is a pervasive consequence of the curing process in photopolymerization and explores one of the most common defects that come across in polymeric-based additive manufacturing. In addition to the characterization of the type and magnitude of distortion, the contributions of this work also include establishing the foundation for design guidelines aiming at minimizing distortion in material jetting.

Details

Rapid Prototyping Journal, vol. 27 no. 6
Type: Research Article
ISSN: 1355-2546

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