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1 – 10 of 711Flaviana Calignano, Alessandro Bove, Vincenza Mercurio and Giovanni Marchiandi
Polymer laser powder bed fusion (PBF-LB/P) is an additive manufacturing technology that is sustainable due to the possibility of recycling the powder multiple times and allowing…
Abstract
Purpose
Polymer laser powder bed fusion (PBF-LB/P) is an additive manufacturing technology that is sustainable due to the possibility of recycling the powder multiple times and allowing the fabrication of gears without the aid of support structures and subsequent assembly. However, there are constraints in the process that negatively affect its adoption compared to other additive technologies such as material extrusion to produce gears. This study aims to demonstrate that it is possible to overcome the problems due to the physics of the process to produce accurate mechanism.
Design/methodology/approach
Technological aspects such as orientation, wheel-shaft thicknesses and degree of powder recycling were examined. Furthermore, the evolving tooth profile was considered as a design parameter to provide a manufacturability map of gear-based mechanisms.
Findings
Results show that there are some differences in the functioning of the gear depending on the type of powder used, 100% virgin or 50% virgin and 50% recycled for five cycles. The application of a groove on a gear produced with 100% virgin powder allows the mechanism to be easily unlocked regardless of the orientation and wheel-shaft thicknesses. The application of a specific evolutionary profile independent of the diameter of the reference circle on vertically oriented gears guarantees rotation continuity while preserving the functionality of the assembled mechanism.
Originality/value
In the literature, there are various studies on material aging and reuse in the PBF-LB/P process, mainly focused on the powder deterioration mechanism, powder fluidity, microstructure and mechanical properties of the parts and process parameters. This study, instead, was focused on the functioning of gears, which represent one of the applications in which this technology can have great success, by analyzing the two main effects that can compromise it: recycled powder and vertical orientation during construction.
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Markus Brummer, Karl Jakob Raddatz, Matthias Moritz Schmitt, Georg Schlick, Thomas Tobie, Rüdiger Daub and Karsten Stahl
Numerous metals can be processed using the additive manufacturing process laser-based powder bed fusion of metals (PBF-LB/M, ISO/ASTM 52900). The main advantages of additive…
Abstract
Purpose
Numerous metals can be processed using the additive manufacturing process laser-based powder bed fusion of metals (PBF-LB/M, ISO/ASTM 52900). The main advantages of additive manufacturing technologies are the high degree of design freedom and the cost-effective implementation of lightweight structures. This could be profitable for gears with increased power density, combining reduced mass with considerable material strength. Current research on additively manufactured gears is focused on developing lightweight structures but is seldom accompanied by simulations and even less by mechanical testing. There has been very little research into the mechanical and material properties of additively manufactured gears. The purpose of this study is to investigate the behavior of lightweight structures in additively manufactured gears under static loads.
Design/methodology/approach
This research identifies the static load-carrying capacity of helical gears with different lightweight structures produced by PBF-LB/M with the case hardening steel 16MnCr5. A static gear loading test rig with a maximum torque at the pinion of T1 = 1200 Nm is used. Further focus is set on analyzing material properties such as the relative density, microstructure, hardness depth profile and chemical composition.
Findings
All additively manufactured gear variants show no failure or plastic deformation at the maximum test load. The shaft hub connection, the lightweight hub designs and the gearing itself are stable and intact regarding their form and function. The identified material characteristics are comparable to conventionally manufactured gears (wrought and machined), but also some particularities were observed.
Originality/value
This research demonstrates the mechanical strength of lightweight structures in gears. Future research needs to consider the dynamic load-carrying capacity of additively manufactured gears.
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Benedetto Allotta, Lorenzo Fiorineschi, Susanna Papini, Luca Pugi, Federico Rotini and Andrea Rindi
This study aims to carry out an investigation of design approaches that should be used for the design of unconventional, innovative transmission system for construction yards to…
Abstract
Purpose
This study aims to carry out an investigation of design approaches that should be used for the design of unconventional, innovative transmission system for construction yards to privilege a smooth behaviour efficiency, and the use of innovative production techniques. Results are quite surprising, as with a proper method it is possible to demonstrate that a cycloidal drive with Wolfrom topology should be an interesting solution for the proposed application.
Design/methodology/approach
With a functional approach, also considering materials and specifications related to the investigated application, it is possible to demonstrate that possible optimal solutions should be quite different respect to the ones that can be suggested with a conventional approach. In particular for proposed applications constraints related to encumbrances, the choice of new material has led to the innovative unconventional choice of a Wolfrom cycloidal speed reducer.
Findings
Provided solution is innovative respect current state of the art for machine currently used in construction yards: in terms of adopted transmission layout; in terms of chosen materials, resulting in an innovative solution.
Research limitations/implications
Current research has strong implications on the adoption of polimeric materials for the construction of reliable transmission for harsh industrial environment as the proposed case study (concrete mixer for construction yard).
Originality/value
Proposed transmission system is absolutely original and innovative respect current state of art also considering proposed materials and consequently production methods. This is an example of transmission designed to be built with polymeric materials by optimizing chosen topology respect to chosen material.
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Chongyi Chang, Gang Guo, Wen He and Zhendong Liu
The objective of this study is to investigate the impact of longitudinal forces on extreme-long heavy-haul trains, providing new insights and methods for their design and…
Abstract
Purpose
The objective of this study is to investigate the impact of longitudinal forces on extreme-long heavy-haul trains, providing new insights and methods for their design and operation, thereby enhancing safety, operational efficiency and track system design.
Design/methodology/approach
A longitudinal dynamics simulation model of the super long heavy haul train was established and verified by the braking test data of 30,000 t heavy-haul combination train on the long and steep down grade of Daqing Line. The simulation model was used to analyze the influence of factors on the longitudinal force of super long heavy haul train.
Findings
Under normal conditions, the formation length of extreme-long heavy-haul combined train has a small effect on the maximum longitudinal coupler force under full service braking and emergency braking on the straight line. The slope difference of the long and steep down grade has a great impact on the maximum longitudinal coupler force of the extreme-long heavy-haul trains. Under the condition that the longitudinal force does not exceed the safety limit of 2,250 kN under full service braking at the speed of 60 km/h the maximum allowable slope difference of long and steep down grade for 40,000 t super long heavy-haul combined trains is 13‰, and that of 100,000 t is only 5‰.
Originality/value
The results will provide important theoretical basis and practical guidance for further improving the transportation efficiency and safety of extreme-long heavy-haul trains.
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Ferdinand Schmid, Constantin Paschold, Thomas Lohner and Karsten Stahl
Internal gearings are commonly used in transmissions due to their advantages like high-power density. To ensure high efficiency, load-carrying capacity and good noise behavior, a…
Abstract
Purpose
Internal gearings are commonly used in transmissions due to their advantages like high-power density. To ensure high efficiency, load-carrying capacity and good noise behavior, a profound knowledge of the local gear mesh is essential. The tooth contact of internal gears relates to a convex and concave surface that form a conformal contact. This is in contrast to external gears, where two convex surfaces form a contraformal contact. This paper aims at a better understanding of conformal contacts under elastohydrodynamic lubrication (EHL) to improve the design of internal gearings.
Design/methodology/approach
An existing numerical EHL model is used for studying the characteristic properties of a hard conformal EHL line contact. A hard contraformal EHL line contact is studied as reference. Non-Newtonian fluid behavior and thermal effects are considered. By taking into account the local contact conformity and kinematics, the effects and relevance of the curvature of the lubricant gap and micro-slip are analyzed. In a parameter study, scale effects of the contact radii on film thickness, temperature rise and friction are examined.
Findings
The curvature of the lubricant gap and effects of micro-slip are small in hard conformal EHL line contacts. For high micro-slip, it can be neglected. Hence, the modeling of conformal contacts using an equivalent geometry of the contact problem is reasonable. The parameter study shows beneficial tribological aspects of the conformal contact compared to the contraformal contact. Higher film thickness and lower fluid coefficient of friction are observed for conformal contacts, which can be attributed to lower pressures for the case of the same external normal force, or to a higher contact temperature rise for the case of equivalent contact pressure.
Originality/value
Despite its widespread existence, the local geometry and kinematics in hard conformal EHL line contacts like in internal gearings have been rarely studied. The findings help for a better understanding of local contact characteristics and its relevance. The quantified scale effects help to improve the efficiency and load-carrying capacity of machine elements with hard conformal EHL contacts, like internal gearings.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2022-0366/
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Carl Henning Christner and Ebba Sjögren
This paper aims to analyse the longitudinal performative effects of accounting, focusing on how accounting shapes the stability/instability of economic frames over time.
Abstract
Purpose
This paper aims to analyse the longitudinal performative effects of accounting, focusing on how accounting shapes the stability/instability of economic frames over time.
Design/methodology/approach
To explore the performative effects of accounting over time, a longitudinal case study narrates the transformation of a large, listed manufacturing company's financial strategy over 20 years. Using extensive document collection, the authors trace the shift from an “industrial” frame to a “shareholder value” frame in the mid-1990s, followed by the gradual entrenchment of this shareholder value frame until its decline in the wake of the financial crisis in 2008.
Findings
Our findings show how accounting has different performative temporalities, capable of precipitating sudden shifts between different economic frames and stabilising an ever-more entrenched and narrowly defined enactment of a specific frame. We conceptualise these different temporalities as performative moments and performative momentum respectively, explaining how accounting produces these performative effects over time. Moreover, in contrast to extant accounting research, the authors provide insight into the performative role of accounting not only in contested but also “cold” situations marked by consensus regarding the overarching economic frame.
Originality/value
Our paper draws attention to the longitudinal performative effects of accounting. In particular, the analysis of how accounting entrenches and refines economic frames over time adds to prior research, which has focused mainly on the contestation and instability of framing processes.
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Frederick de Moll and Akihide Inaba
In recent decades, childhood in Japan has undergone significant transformations. Government policies geared at boosting women's labor force participation, a declining fertility…
Abstract
In recent decades, childhood in Japan has undergone significant transformations. Government policies geared at boosting women's labor force participation, a declining fertility rate, rising costs of having children on the one hand, and increased spending on public childcare and support measures for families, on the other hand, contribute to these ongoing changes. Having only one child is becoming the norm while mothers' role in society is shifting. The traditional family structure is moving from the previously predominant male breadwinner model to more dual-earner families. Children now spend significant amounts of time in care and education institutions.
In this chapter, we analyze current configurations of early childhood in institutions and the family from a policy perspective and regarding children's predominant education and care arrangements. Drawing on various survey data sets and evidence from demographic statistics to pedagogical ethnographies, we look at how childcare policies and families reshape the organization of children's lives and outline how institutions and educators create learning experiences aligned with the values of a collectivist society. However, despite being deeply rooted in traditional child-rearing goals, many parents also subscribe to rigorous educational arrangements from early childhood onwards to prepare children for success in a competitive education system. The chapter finishes with an outlook on future directions of how policymakers and the ongoing institutionalization of childhood continue to change children's lives.
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The present chapter explicates urban and rural childhoods in India. It presents childhood as a dynamic product arising out of an intersection of children's experiences in…
Abstract
The present chapter explicates urban and rural childhoods in India. It presents childhood as a dynamic product arising out of an intersection of children's experiences in different familial–socio-cultural contexts, and children's positions within parent–child interactions and relations. These contexts and interactions tend to colour and shape the childhoods that children inhabit. Drawing on fieldwork conducted in urban and rural India, the chapter documents (1) nature of children's engagements and (2) parent–child relations, explicitly observed in parent–child interactions, provisioning warmth and care; parental control and supervision over children and children's participation in the overall fabric of family life and so forth. Forty-eight parents (24 urban and 24 rural) of children aged 7–11 years participated in the study. Qualitative data gathered through semi-structured interviews and home observations revealed distinctions in urban and rural Indian childhoods. Urban childhood is characterised by rights and privileges, and the centrality of academic pursuits, while rural childhood is featured with subtle induction into economic and social fabric of rural life. Although the world of ‘Indian childhood’ seemed plural, childhood playfulness and learning seemed to be the unifying themes. Geared to the fact that children have to make a living with limited means in the future, both childhoods were accelerated in preparation for future. Dwelling on the complexities in children's lives, this article appreciates diversity and multiplicity in childhoods.
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Stefano Marchese, Luca Gastaldi and Mariano Corso
This paper explores how adaptive organizations, companies capable of continuously adapting their organizational model, dynamically solve the universal problems of organizing.
Abstract
Purpose
This paper explores how adaptive organizations, companies capable of continuously adapting their organizational model, dynamically solve the universal problems of organizing.
Design/methodology/approach
The authors applied grounded theory to data acquired from six interpretative case studies, collected in two rounds of interviews (15 in total), then completing and validating the study’s evidence through triangulation with several secondary data sources.
Findings
In adaptive organizations, polyarchies and intrapreneurial employees are essential to shape the division of labour, leading to high levels of autonomy and empowering individuals and teams, while reducing bureaucracy and hierarchy. In terms of the integration of effort, digital solutions are preferred to social proof in the provision of information, while the authors note that incentives are always geared towards developing strong higher-order dynamic capabilities.
Research limitations/implications
This paper has some limitations that could be addressed in future research, including longitudinal studies to analyse the link between the universal problems of organizing and a company's dynamic capabilities.
Practical implications
Adaptive organizations go beyond tech firms in responding to the universal problems of organizing work by making specific use of digital technologies.
Originality/value
The paper studies how companies should organize themselves so that they continuously adapt to an ever-changing competitive environment.
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Xingwen Wu, Zhenxian Zhang, Wubin Cai, Ningrui Yang, Xuesong Jin, Ping Wang, Zefeng Wen, Maoru Chi, Shuling Liang and Yunhua Huang
This review aims to give a critical view of the wheel/rail high frequency vibration-induced vibration fatigue in railway bogie.
Abstract
Purpose
This review aims to give a critical view of the wheel/rail high frequency vibration-induced vibration fatigue in railway bogie.
Design/methodology/approach
Vibration fatigue of railway bogie arising from the wheel/rail high frequency vibration has become the main concern of railway operators. Previous reviews usually focused on the formation mechanism of wheel/rail high frequency vibration. This paper thus gives a critical review of the vibration fatigue of railway bogie owing to the short-pitch irregularities-induced high frequency vibration, including a brief introduction of short-pitch irregularities, associated high frequency vibration in railway bogie, typical vibration fatigue failure cases of railway bogie and methodologies used for the assessment of vibration fatigue and research gaps.
Findings
The results showed that the resulting excitation frequencies of short-pitch irregularity vary substantially due to different track types and formation mechanisms. The axle box-mounted components are much more vulnerable to vibration fatigue compared with other components. The wheel polygonal wear and rail corrugation-induced high frequency vibration is the main driving force of fatigue failure, and the fatigue crack usually initiates from the defect of the weld seam. Vibration spectrum for attachments of railway bogie defined in the standard underestimates the vibration level arising from the short-pitch irregularities. The current investigations on vibration fatigue mainly focus on the methods to improve the accuracy of fatigue damage assessment, and a systematical design method for vibration fatigue remains a huge gap to improve the survival probability when the rail vehicle is subjected to vibration fatigue.
Originality/value
The research can facilitate the development of a new methodology to improve the fatigue life of railway vehicles when subjected to wheel/rail high frequency vibration.
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