Search results

1 – 10 of over 7000
Article
Publication date: 1 August 2011

Vinay Kumar Midha, A Mukhopadhyay and Ramanpreet Kaur

Owing to a high amount of stress, seam failure in workwear fabrics makes the fabric unsuitable although the fabric strength is high. It is therefore important to predict…

Abstract

Owing to a high amount of stress, seam failure in workwear fabrics makes the fabric unsuitable although the fabric strength is high. It is therefore important to predict the seam strength to ascertain the performance of the garments during use and determine the required thread strength and stitch density to match the required seam strength. In all of the earlier predictive equations, seam strength is predicted from thread strength and stitch density along with some multiplicative factors. During the sewing process, a substantial loss in needle thread strength occurs; therefore, the thread becomes weaker than expected after incorporation into the seam. In this paper, the effects of various machine and process parameters are studied on thread strength loss and seam strength. The seam strength is predicted from the loop strength after considering the loss in thread strength. It is observed that higher seam strengths are observed when stronger threads are used for sewing. Loss in thread strength has a significant influence on the seam strength. Seam strength can be predicted using stitch density and thread loop strength, by considering the loss in thread strength during the sewing process. A closer match between predicted and experimental seam strength is possible.

Details

Research Journal of Textile and Apparel, vol. 15 no. 3
Type: Research Article
ISSN: 1560-6074

Keywords

Article
Publication date: 1 April 2004

A. Bochenek, B. Bober, W. Hauffe, M. Lukaszewicz and E. Langer

Investigations were aimed at the evaluation of degradation mechanisms in ultrasonically welded joints of AlSi1 per cent wire (25 μm in diameter) and Au substrate (100 μm…

Abstract

Investigations were aimed at the evaluation of degradation mechanisms in ultrasonically welded joints of AlSi1 per cent wire (25 μm in diameter) and Au substrate (100 μm thick), relatively thick elements, exposed to high temperature of 300°C up to 100 h. Thermally activated Al diffusion into Au generates the formation of intermetallic compounds in the area of the bond interface. With the longer thermal exposure the expansion and transformation of intermetallic compounds is observed. The characteristic “intermetallic compounds core” is formed, which from one side penetrates into the wire material and from another spreads deeply into the Au substrate up to enhancing band of Kirkendall voids.

Details

Microelectronics International, vol. 21 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 12 June 2020

Mehran Masdari, Milad Mousavi and Mojtaba Tahani

One of the best methods to improve wind turbine aerodynamic performance is modification of the blade’s airfoil. The purpose of this paper is to investigate the effects of…

Abstract

Purpose

One of the best methods to improve wind turbine aerodynamic performance is modification of the blade’s airfoil. The purpose of this paper is to investigate the effects of gurney flap geometry and its oscillation parameters on the pitching NACA0012 airfoil.

Design/methodology/approach

This numerical solution has been carried out for different cases of gurney flap mounting angles, heights, reduced frequencies and oscillation amplitudes, then the results were compared to each other. The finite volume method was used for the discretization of the governing equations, and the PISO algorithm was used to solve the equations. Also, the “SST” was adopted as the turbulence model in the simulation.

Findings

In this paper, the different parameters of gurney flap were investigated. The results showed that the best range of gurney flap height are between 1 and 3.2% of chord and the best ratio of lifting to drag coefficient is achieved in gurney flap with an angle of 90° relative to the chord direction. The dynamic stall angle of the airfoil with gurney flap decreases were compared to without gurney flap. Earlier LEV formation can be one of the main reasons for decreasing the dynamic stall angle of the airfoil with gurney flap. Increasing the reduced frequency and oscillation amplitude causes rising of maximum lift coefficient and consequently lift curve slope. Moreover, gurney flap with mounting angle has a lower hinge moment than the gurney flap without mounting angle but with the same vertical axis length. So, there is more complexity in structural design concerning the gurney flap without mounting angle.

Practical implications

Improving aerodynamic efficiency of airfoils is vital for obtaining more output power in VAWTs. Gurney flaps are one of the best mechanisms to increase the aerodynamic performance of the airfoil and increases the efficiency of VAWTs.

Originality/value

Investigating the hinge moment on the connection point of the airfoil, gurney flap and try to compare the gurney flap with and without angle.

Details

Aircraft Engineering and Aerospace Technology, vol. 92 no. 7
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 29 December 2020

Pierandrea Dal Fabbro, Andrea La Gala, Willem Van De Steene, Dagmar R. D’hooge, Giovanni Lucchetta, Ludwig Cardon and Rudinei Fiorio

This study aims to evaluate and compare the macroscopic properties of commercial acrylonitrile-butadiene-styrene (ABS) processed by two different types of additive…

Abstract

Purpose

This study aims to evaluate and compare the macroscopic properties of commercial acrylonitrile-butadiene-styrene (ABS) processed by two different types of additive manufacturing (AM) machines. The focus is also on the effect of multiple closed-loop recycling of ABS.

Design/methodology/approach

A conventional direct-drive, Cartesian-type machine and a Bowden, Delta-type machine with an infrared radiant heating system are used to manufacture test specimens molded in ABS. Afterward, multiple closed-loop recycling cycles are conducted, involving consecutive AM (four times) and recycling (three times). The rheological, mechanical, morphological and physicochemical properties are investigated.

Findings

The type of machine affects the quality of the produced parts. The machine containing an infrared radiant system in a temperature-controlled chamber produces parts showing higher mechanical properties and filling fraction, although it increases the yellowing. Closed-loop recycling of ABS for AM is applicable for at least two cycles, inducing a slight increase in tensile modulus (ca. 5%) and in tensile strength (ca. 13%) and a decrease in the impact strength (ca. 14%) and melt viscosity. An increase in the filling fraction of the AM parts promotes an increase in tensile strength and tensile modulus, although it does not influence the impact strength. Furthermore, multiple closed-loop recycling does not affect the overall chemical structure of ABS.

Practical implications

Controlling the environmental temperature and using infrared radiant heating during AM of ABS improves the quality of the produced parts. Closed-loop recycling of ABS used in AM is feasible up to at least two recycling steps, supporting the implementation of a circular economy for polymer-based AM.

Originality/value

This study shows original results regarding the assessment of the effect of different types of AM machines on the main end-use properties of ABS parts and the influence of multiple closed-loop recycling on the characteristics of ABS fabricated by the most suited AM machine with an infrared radiant heating system and a temperature-controlled environment.

Article
Publication date: 1 January 1988

R.V. Winkle and S.R. Cater

This paper describes the first of a two part study of copper ball/wedge thermosonic wire bonding and concentrates on the second wedge bond to copper thick film. Results of…

Abstract

This paper describes the first of a two part study of copper ball/wedge thermosonic wire bonding and concentrates on the second wedge bond to copper thick film. Results of varying the bonding machine parameters of force, amplitude of vibration, weld time, substrate temperature and bonding direction on bond strength are discussed and optimum conditions to give maximum yield suggested. Methods of providing adequate gas shielding of the wire and substrate and the effect of wire ductility are also presented. Particular attention has been given to improving the accuracy and speed of testing of the loop pull test by correcting for variations in wire loop geometry. A method will be described for measuring loop height automatically during each test and the incorporation of a computer to obtain corrected values of force.

Details

Microelectronics International, vol. 5 no. 1
Type: Research Article
ISSN: 1356-5362

Article
Publication date: 1 August 2016

Iwona Frydrych and Agnieszka Greszta

Seam efficiency plays an important role for obtaining a desired seam quality. Therefore, this issue is often referred in research papers. The purpose of this paper is to…

Abstract

Purpose

Seam efficiency plays an important role for obtaining a desired seam quality. Therefore, this issue is often referred in research papers. The purpose of this paper is to determine the seam strength and efficiency as well as examining, if and how such factors as: a kind of fabric, kind of thread, kind of seam and the stitch density influence the transverse seam strength and the seam efficiency.

Design/methodology/approach

For research four types of polyester/wool fabrics having different structural parameters and two types of polyester sewing threads were used. Three types of seam were made. The fabric samples were sewn using lockstitch with three different stitch densities. Obtained in this way seams were tested on the tensile machine. The influence of individual factors on the seam strength and its efficiency was assessed statistically using a multivariate variance analysis (ANOVA).

Findings

The findings of this study revealed that the independent variable – stitch density affect significantly of the seam strength as well as its efficiency. Seam strength and seam efficiency values increase with the increase stitch density. Moreover, the variance analysis showed that a kind of fabric also is a statistically significant factor for the seam efficiency and its strength. Furthermore, in the case of seam efficiency it is also important to the stitch direction. However, the study did not show an impact of kind of thread and kind of seam on dependent variables: the seam strength and its efficiency.

Research limitations/implications

Due to the fact that this paper focuses on the seams made only on wool/polyester fabrics with two the most popular weaves, involving only two sewing PES threads, the conclusions presented in this paper are valid only to this assortment and cannot be generalized.

Originality/value

So far, it has not been taken research on the effect of seams with the different number of sewn layers on the seam strength and efficiency. This issue has been taken in this work.

Details

International Journal of Clothing Science and Technology, vol. 28 no. 4
Type: Research Article
ISSN: 0955-6222

Keywords

Article
Publication date: 1 March 1998

G. Sundaresan, K.R. Salhotra and P.K. Hari

The mechanism of strength reduction of sewing threads has been discussed in Part I of this paper. The effect of fabric tightness and certain thread properties like its…

Abstract

The mechanism of strength reduction of sewing threads has been discussed in Part I of this paper. The effect of fabric tightness and certain thread properties like its size, coefficient of yarn‐metal friction, twist direction, number of piles, type of fibre and fibre denier on strength reduction has been studied and found to influence the severity of strength reduction of the thread.

Details

International Journal of Clothing Science and Technology, vol. 10 no. 1
Type: Research Article
ISSN: 0955-6222

Keywords

Article
Publication date: 29 April 2019

Adam Jakubas, Radosław Jastrzębski and Krzysztof Chwastek

The purpose of this paper is to examine the effect of varying compaction pressure on magnetic properties of self-developed soft magnetic composite (SMC) cores. The change…

Abstract

Purpose

The purpose of this paper is to examine the effect of varying compaction pressure on magnetic properties of self-developed soft magnetic composite (SMC) cores. The change in shape of ferromagnetic hysteresis curves has – in turn – the impact on the values of hysteresis model parameters. The phenomenological GRUCAD model is chosen for description of hysteresis curves.

Design/methodology/approach

Several cylinder-shaped cores have been made from a mixture of iron powder and suspense polyvinyl chloride using a hydraulic press with a form and a band with a thermocouple for controlling heat treatment conditions. The only varying parameter in the study is the compaction pressure. The magnetic properties of developed cores have been measured using a computer-acquisition card and LabView software. The obtained hysteresis curves are fitted to the equations of the phenomenological GRUCAD model. This description is compliant with the laws of irreversible thermodynamics. The variations of model parameters are presented as functions of compacting pressure.

Findings

The compaction pressure has a significant impact on magnetic properties of self-developed SMC cores. The paper provides a number of charts useful for checking how the parameters of the hysteresis model are affected.

Research limitations/implications

The present paper is limited to modelling symmetrical loops only. Description of more complex magnetization cycles is postponed to another, forthcoming paper.

Practical implications

The GRUCAD hysteresis model may be a useful tool for the designers of magnetic circuits. Its parameters depend on the processing conditions (in this study – the compaction pressure) of the SMC cores.

Originality/value

Modelling of magnetic properties of SMC cores has been carried so far using some well-known description like Preisach, Takács and Jiles–Atherton proposals. The GRUCAD model has a number of advantages, and it may be a useful alternative to the latter formalism. So far it has been used for description of hysteresis curves in conventional materials like non-oriented and grain-oriented electrical steels. In the present work, it is applied to novel SMC materials.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 38 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 7 January 2014

Boonlert Jitmaneeroj

In an introductory finance course, business school students often report difficulty in dealing with several variables and regression equations in testing the forward…

Abstract

Purpose

In an introductory finance course, business school students often report difficulty in dealing with several variables and regression equations in testing the forward market efficiency and its relevant hypotheses: forward rate unbiasedness, rational expectations, risk neutrality and homogeneous expectations. The paper aims to discuss these issues.

Design/methodology/approach

Although each of these hypotheses may be relatively easy to understand one by one, it is harder to see their linkages. Thus, the author develops the loop diagram for supplementing traditional instruction methods.

Findings

The author finds that a significant majority of students prefer the loop diagram approach. Furthermore, students using loop diagram display more understanding of the forward market efficiency than those with access to a conventional instruction.

Originality/value

The loop diagram provides students a simple visual aid for formulating a complete set of regressions and enables them to analyze a richer set of relationships between several hypotheses than what they typically see in finance textbooks.

Details

Managerial Finance, vol. 40 no. 2
Type: Research Article
ISSN: 0307-4358

Keywords

Article
Publication date: 12 May 2022

Francesca Costanza

The purpose of this paper is to adopt a learning-based approach to portray the impact of Covid-19 on state school services in Italy, with a specific focus on the role of…

Abstract

Purpose

The purpose of this paper is to adopt a learning-based approach to portray the impact of Covid-19 on state school services in Italy, with a specific focus on the role of street-level bureaucrats and the triggering of co-creative processes.

Design/methodology/approach

The study proposes a qualitative system dynamics (or SD) approach describing the implementation of Covid-related educational policies in Italy. An insight model, made of causal loop diagrams, integrates the selected multi-disciplinary literature and institutional sources, secondary data from national and local reports (about Palermo, the fifth largest metropolitan city in Italy) and insights from a panel of school street–level bureaucrats.

Findings

The study provides an insight into the impacts of governmental decisions (school closures and the subsequent need to activate distance learning during the first wave of Covid-19) at a local level. Specifically, it portrays the influences of managerial and professional discretion, infrastructural equipment and socio-economic factors favouring/deterring co-creative educational processes.

Practical implications

The SD model highlights vicious/virtuous circles in policy implementation and suggests new managerial paths for education, more routed towards public value creation and less attached to bureaucratic procedures and the unquestioning application of performance culture.

Originality/value

The paper proposes an original and holistic approach to dealing with policy making in education and its managerial features. The research findings are considered important, not only to face the current emergency, but also to pro-actively think about the post-Covid era.

Details

International Journal of Public Sector Management, vol. 35 no. 4
Type: Research Article
ISSN: 0951-3558

Keywords

1 – 10 of over 7000