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1 – 10 of over 2000
Article
Publication date: 12 September 2019

Sam Joshy, Jayadevan K.R., Ramesh A. and Mahipal D.

In hot forging, a significant amount of forging force is used for overcoming frictional force at the die-billet interface. The high frictional force along with thermomechanical…

Abstract

Purpose

In hot forging, a significant amount of forging force is used for overcoming frictional force at the die-billet interface. The high frictional force along with thermomechanical stress lead to wear, plastic deformation, mechanical fatigue and cracks, which reduce the service life of hot forging dies. Of all these different types of issues, wear is the predominant mode of failure in hot forging dies. This paper aims to describe mechanisms of wear transition in different loads at near forging temperature, occurring during sliding of chromium-based H11 tool steel specimens.

Design/methodology/approach

High temperature pin-on-disc tests are performed with pin specimens machined from bars of X38CrMoV5 steel, heat treated to surface hardness of 40-42 HRc. The disc is made of EN 31 steel with hardness of 60-62 HRc. Tests are performed at constant temperature of 500°C, and the normal load was varied from 20 to 70 N.

Findings

Scanning electron microscopy investigations on worn surface have revealed that wear is primarily due to abrasion and plastic deformation. The test results show an increasing trend in wear rate with increase in load up to 30 N, followed by a reversal in trend until 50 N. This transition in wear rate is caused by development of wear resistant layers, which are formed by compaction of wear debris particles on to the worn surfaces. These compact layers are found to be stable during load range from 40 and 50 N. However, with further increase in load, abrasive wear tracks are observed without any evidence of protective layers. As a result, there is an increase in wear rate with increase in loads above 50 N. In addition, plastic shearing was dominant over abrasive wear at this load regime.

Originality/value

The study on wear behaviour of H11 hot forging steel at 20 to 70 N will be an input to the research in hot forming industries.

Details

World Journal of Engineering, vol. 16 no. 5
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 29 August 2019

Sam Joshy, Jayadevan K.R., Ramesh A. and Mahipal D.

The prime task of research in hot forging industry is to improve the service life of forging dies. The in-service microstructural changes that may occur in a die during hot…

Abstract

Purpose

The prime task of research in hot forging industry is to improve the service life of forging dies. The in-service microstructural changes that may occur in a die during hot forging is expected to significantly affect the service life. The purpose of this work is to analyse the microstructural evolution of double tempered hot forging dies in a real industrial environment, and the correlation of microstructural and microhardness evolution to the in-service wear and plastic deformation.

Design/methodology/approach

Specific hot forging tests were carried out on double tempered AISI H11 chromium tool steel for 100, 500 and 1,000 forging strokes. Macro analysis was conducted on die cross section to analyse the wear and plastic deformation at different stages of forging cycles. Microhardness and microstructural analyses were performed on the die surface after these forging tests.

Findings

The macro analysis on the transverse section of dies shows that wear is predominant during initial forging strokes, whereas plastic deformation is observed in later stages. Microstructural analyses demonstrate that during first 500 forging cycles, carbide population decreases at 63 per cent higher rate as compared to corresponding drop during 501 to 1,000 forging cycles. Additionally, the carbide size increases at all stages of forging cycle. Further, microstructural images from dies after 1,000 forging strokes show clustering and spherodisation of carbides by which the “blocky”-shaped carbides in pre-forging samples had spherodised to form “elongated spherical” structures.

Practical implications

The findings of this work can be used in hot forging industries to predict amount of wear and plastic deformation at different stages of service. From the results of this work, the service life of double tempered H11 hot forging dies used in forging without lubrication is within 501 to 1,000 forgings.

Originality/value

Most of the literatures are focussed on the cyclic softening of material at constant temperature. This work analyses the microstructural evolution of double tempered hot forging dies in a real industrial environment and correlates the microstructural and microhardness evolution to the in-service wear and plastic deformation.

Details

World Journal of Engineering, vol. 16 no. 5
Type: Research Article
ISSN: 1708-5284

Keywords

Book part
Publication date: 29 March 2006

Dirk Baur

Existing multivariate generalized autoregressive conditional heteroskedasticity (GARCH) models either impose strong restrictions on the parameters or do not guarantee a…

Abstract

Existing multivariate generalized autoregressive conditional heteroskedasticity (GARCH) models either impose strong restrictions on the parameters or do not guarantee a well-defined (positive-definite) covariance matrix. I discuss the main multivariate GARCH models and focus on the BEKK model for which it is shown that the covariance and correlation is not adequately specified under certain conditions. This implies that any analysis of the persistence and the asymmetry of the correlation is potentially inaccurate. I therefore propose a new Flexible Dynamic Correlation (FDC) model that parameterizes the conditional correlation directly and eliminates various shortcomings. Most importantly, the number of exogenous variables in the correlation equation can be flexibly augmented without risking an indefinite covariance matrix. Empirical results of daily and monthly returns of four international stock market indices reveal that correlations exhibit different degrees of persistence and different asymmetric reactions to shocks than variances. In addition, I find that correlations do not always increase with jointly negative shocks implying a justification for international portfolio diversification.

Details

Econometric Analysis of Financial and Economic Time Series
Type: Book
ISBN: 978-0-76231-274-0

Book part
Publication date: 10 December 2015

Dekar Urumsah

The concept and practice of e-services has become essential in business transactions. Yet there are still many organizations that have not developed e-services optimally. This is…

Abstract

The concept and practice of e-services has become essential in business transactions. Yet there are still many organizations that have not developed e-services optimally. This is especially relevant in the context of Indonesian Airline companies. Therefore, many airline customers in Indonesia are still in doubt about it, or even do not use it. To fill this gap, this study attempts to develop a model for e-services adoption and empirically examines the factors influencing the airlines customers in Indonesia in using e-services offered by the Indonesian airline companies. Taking six Indonesian airline companies as a case example, the study investigated the antecedents of e-services usage of Indonesian airlines. This study further examined the impacts of motivation on customers in using e-services in the Indonesian context. Another important aim of this study was to investigate how ages, experiences and geographical areas moderate effects of e-services usage.

The study adopts a positivist research paradigm with a two-phase sequential mixed method design involving qualitative and quantitative approaches. An initial research model was first developed based on an extensive literature review, by combining acceptance and use of information technology theories, expectancy theory and the inter-organizational system motivation models. A qualitative field study via semi-structured interviews was then conducted to explore the present state among 15 respondents. The results of the interviews were analysed using content analysis yielding the final model of e-services usage. Eighteen antecedent factors hypotheses and three moderating factors hypotheses and 52-item questionnaire were developed. A focus group discussion of five respondents and a pilot study of 59 respondents resulted in final version of the questionnaire.

In the second phase, the main survey was conducted nationally to collect the research data among Indonesian airline customers who had already used Indonesian airline e-services. A total of 819 valid questionnaires were obtained. The data was then analysed using a partial least square (PLS) based structural equation modelling (SEM) technique to produce the contributions of links in the e-services model (22% of all the variances in e-services usage, 37.8% in intention to use, 46.6% in motivation, 39.2% in outcome expectancy, and 37.7% in effort expectancy). Meanwhile, path coefficients and t-values demonstrated various different influences of antecedent factors towards e-services usage. Additionally, a multi-group analysis based on PLS is employed with mixed results. In the final findings, 14 hypotheses were supported and 7 hypotheses were not supported.

The major findings of this study have confirmed that motivation has the strongest contribution in e-services usage. In addition, motivation affects e-services usage both directly and indirectly through intention-to-use. This study provides contributions to the existing knowledge of e-services models, and practical applications of IT usage. Most importantly, an understanding of antecedents of e-services adoption will provide guidelines for stakeholders in developing better e-services and strategies in order to promote and encourage more customers to use e-services. Finally, the accomplishment of this study can be expanded through possible adaptations in other industries and other geographical contexts.

Details

E-services Adoption: Processes by Firms in Developing Nations
Type: Book
ISBN: 978-1-78560-709-7

Keywords

Article
Publication date: 5 October 2015

Carmen Medrea, Antonios Kalfopoulos, Dimitrios Papageorgiou and Ionel Chicinas

A local company producing aluminum profile encounters frequent failures to bridge dies. In total, 22 dies failed within a year, entailing production disruptions and extensive…

Abstract

Purpose

A local company producing aluminum profile encounters frequent failures to bridge dies. In total, 22 dies failed within a year, entailing production disruptions and extensive downtimes. Bridges usually exhibit cracks on the ribs. The failure analysis of the failed parts has been performed in order to propose solution for correct and economical process. The paper aims to discuss these issues.

Design/methodology/approach

Recorded history was collected regarding tool’s material selection, manufacturing conditions, usage and service. A representative failed bridge was in depth analyzed. The piece was optically inspected. Rockwell hardness measurements and chemical analysis were performed. The paper is focussed on the microscopic examination of the failed parts. Specimens were cut from bridge’s ribs. Areas including cracks were analyzed on the cross section of the samples by optical and scanning electron microscopy. Local chemical analysis was made by X-ray microanalysis.

Findings

Design, deficiency and improper maintenance are considered to be responsible for the systematic die damage. Prolonged preheating duration and poor quality surfaces before nitriding render dies premature unusable. The preheating duration should be controlled and protective atmosphere should be used. Furthermore, it is suggested to protect the ribs during nitriding as a preventive measure against crack initiation. The bridge’s geometry can be improved by fabricating ribs with larger radii. A finer polishing is recommended.

Originality/value

The present analysis resolved a serious deficiency in extrusion production. Extended research has been conducted in the field of aluminum extrusion dies, nevertheless, the present work presents new metallographic aspects as well as some interesting notes regarding the repetitive nitriding of bridge dies.

Details

International Journal of Structural Integrity, vol. 6 no. 5
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 1 January 2002

Maja Konecnik

The paper points out the image of a destination as a possible source of competitive advantage of the destination. A review of the literature is included showing the rising…

Abstract

The paper points out the image of a destination as a possible source of competitive advantage of the destination. A review of the literature is included showing the rising importance of the image of a destination. Slovenia's image as a tourist destination perceived by foreign tourist experts is analysed. Interesting mountains and lakes, beautiful natural attractions and interesting and friendly people were identified as the most typical attributes of Slovenia's image from the foreign tourist experts' point of view. The significant differences in Slovenia's image between those experts familiar with Slovenia compared to those experts who are only just aware of Slovenia are presented. The research shows that familiarity with Slovenia increases a tourist expert's image of Slovenia, especially the perceptual/cognitive component. According to the results of discriminant analysis, the discriminant attributes of Slovenia's image for each group are emphasised. Slovenia's appealing food and modern health resorts were the discriminant attributes for the group of tourist experts that is familiar with Slovenia, while traditional events were the distinguish attribute for the group of experts that is only just aware of Slovenia. Suggestions as organising familiarisation tours that include tour operators, travel agents and travel writers seemed to be a proper way of boosting Slovenia's image compared to other competitive tourist destinations.

Article
Publication date: 1 March 1997

D.D. Bainov and I.M. Stamova

Investigates the global stability of the zero solution of an impulsive system of differential‐difference equations with variable impulsive perturbations. By means of piecewise…

Abstract

Investigates the global stability of the zero solution of an impulsive system of differential‐difference equations with variable impulsive perturbations. By means of piecewise continuous functions which are analogues of Lyapunov’s functions, and of the comparison principle, sufficient conditions for global stability of the zero solution of the systems considered are found.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 16 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

Book part
Publication date: 8 March 2011

Yushi Yoshida

We investigate whether or not the effects of the subprime financial crisis on 12 Asian economies are similar to those of the Asian financial crisis by examining volatility…

Abstract

We investigate whether or not the effects of the subprime financial crisis on 12 Asian economies are similar to those of the Asian financial crisis by examining volatility spillovers and time-varying correlation between the US and Asian stock markets. After pretesting volatility causality and constancy of correlation, we estimate an appropriate smooth-transition correlation VAR-GARCH model for each Asian stock market. First, the empirical evidence indicates stark differences in stock market linkages between the two crises. The volatility causality comes from the crises-originating country. Volatility in Asian stock markets Granger-caused volatility in the US market during the Asian crisis, whereas volatility in the US stock market Granger-caused volatility in Asian stock markets during the subprime crisis. Second, decreased correlations during the period of financial turmoil were observed, especially during the Asian financial crisis. Third, the estimated points of transition in the correlation are indicative of market participants’ awareness of the ensuing stock market crashes in July 1997 and in September 2008.

Details

The Evolving Role of Asia in Global Finance
Type: Book
ISBN: 978-0-85724-745-2

Keywords

Article
Publication date: 24 July 2023

Kamran Ali Chatha, Muhammad Shakeel Sadiq Jajja, Fatima Gillani and Sami Farooq

This paper aims to investigate the role of organizational and technological enablers and their arrangement and alignment with the external environment to facilitate supply chain…

Abstract

Purpose

This paper aims to investigate the role of organizational and technological enablers and their arrangement and alignment with the external environment to facilitate supply chain integration (SCI), which consequently improves operational performance.

Design/methodology/approach

The paper uses a structural equation modeling approach and the data from 307 manufacturing firms from the International Manufacturing Strategy Survey version VI for hypotheses testing.

Findings

The findings of the study reveal that (1) the alignment and particular arrangement of the sociotechnical organizational factors enable the SCI of a firm, (2) suitable organizational arrangements help in leveraging SCI under environmental pressures, and (3) SCI leverages the relationship between sociotechnical organizational factors and operational performance of the firm.

Practical implications

This paper informs managers that SCI leverages the operational performance of firms under heightened environmental pressures. Developing suitable manufacturing technologies infrastructure followed by organizational practices aligned with the manufacturing technologies make it easier to realize SCI.

Originality/value

This study explores the interaction of technological, organizational, and environmental factors as driving and enabling factors that help achieve SCI. Firms that develop an open and collaborative environment and use communication and integrative technologies to complement their work practices better cope with external pressures. These modern forms of working and the use of technologies facilitate SCI and leverage it effectively to positively impact firm performance.

Details

Benchmarking: An International Journal, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1463-5771

Keywords

Article
Publication date: 1 July 2006

Robert N. Lussier and Matthew C. Sonfield

The purpose of this paper is to investigate how family businesses change as they grow in size, and to compare differences between the USA and France.

2396

Abstract

Purpose

The purpose of this paper is to investigate how family businesses change as they grow in size, and to compare differences between the USA and France.

Design/methodology/approach

The research design is survey research, statistically t‐testing 12 hypothesized differences between smaller and larger firms in the USA (n=159) and in France (n=116).

Findings

The research finds that both countries' larger firms have significantly (p < 0.05) more non‐family members within top management and make greater use of outside consultants, advisors, and professional services than smaller firms. However, family businesses in France had no other significant differences, while those in the USA had four. Larger US firms have a smaller percentage of women family members working in the firm and less conflict and disagreement between family members; they also spend more time in strategic management activities, and use more sophisticated methods of financing.

Research limitations/implications

There are some variations between the two country samples.

Practical implications

Understanding whether and how family business management activities, styles and characteristics change with growth can help those who own and manage such businesses. It can also be of value to those who advise and assist family businesses, as well as researchers who study them.

Originality/value

This is the first study to analyze the effect of firm size on family business management and to conduct a cross‐national comparison.

Details

Journal of Small Business and Enterprise Development, vol. 13 no. 3
Type: Research Article
ISSN: 1462-6004

Keywords

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