Numerical and experimental analysis of CFRP machining process in orthogonal cutting

Les matériaux composites, y compris le PRFC (polymère renforcé de fibre de carbone), sont de plus en plus utilisés en aéronautique et dans l'automobile, ce qui soulève actuellement de nombreuses complications dans les processus d'usinage. Comme ces matériaux sont fabriqués en plusieurs phases, ils sont responsables d'une mauvaise qualité d'usinage et de défauts indésirables. Cette thèse vise à mieux comprendre la technique physique fondamentale impliquée dans le mécanisme de formation de copeaux dans le découpage orthogonal d'usinage en PRFC par des études numériques et expérimentales combinées. Ensuite, l'analyse se concentre sur la manière dont certains paramètres de coupe, par exemple, la profondeur de coupe, affectent les efforts de coupe, la qualité de surface, les délaminations entre couches, la génération de fissures internes et la forme et la taille de copeaux générées. De plus, une observation expérimentale a été faite pour déterminer la profondeur de coupe minimale en dessous de laquelle le matériau ne peut pas être coupé en douceur sur toute la surface. Ce travail de recherche a été complété par une étude préliminaire sur le mécanisme d'usure des outils de coupe.The composite materials, including CFRP (Carbon Fiber Reinforced Polymer), are increasingly used in aeronautics and automotives which is currently raising many complications in the machining processes. As those materials are made with multiple phases, they are accountable for poor machining quality and undesired defects. This thesis seeks to better understand the fundamental physical technique involved in chip formation mechanism in orthogonal cutting of CFRP machining by combined numerical and experimental studies. Then, the analysis focuses to how certain cutting parameters, e.g., cutting depth, affect to the cutting efforts, surface quality, interply delaminations, inner crack generation and to generated chip shape and size. Moreover, an experimental observation has been made to find out the minimum cuttable depth below which the material does not get cut smoothly over the whole surface. This research work has been finished by a preliminary study on cutting tool wear mechanism

Visiting friends and relatives (VFR): a multi-sited study of mobilities between Bangladesh and London

The thesis examines the bilateral transnational visiting mobilities of British Bangladeshis and their non-migrant relatives and friends. Theoretically, it draws from the interdisciplinary research fields of Mobilities, Transnationalism and Diaspora Studies. Geographically, it focuses on the VFR practices, processes, experiences of ‘to and fro’ visits between Bangladesh and the Bangladeshi London diaspora, and the social, cultural and political implications of the mobilities and immobilities that unfold. The research is designed as a multi-sited study. Data was collected over a thirteenmonth period through participant observation and semi-structured interviews in London and Bangladesh. Analysis of the empirical evidence is divided into three key trajectories. In the first trajectory, I interpret and compare the context and experiences of VFR mobilities from Britain to Bangladesh, i.e. visits to the migrant and diasporic ‘homeland’. Deploying the notion of ‘memoryscape’, I analyse British-Bangladeshis’ often nostalgic and idealised recollections of places, landscapes and people remembered from the distant past of childhood and early adulthood, or from more recent experiences of visits, and with a particular focus on cross-generational and gendered comparisons. Secondly, I look into the VFR mobilities from a different perspective by reversing the transnational optic. I explore and analyse the diverse experiences and interactions of non-migrant Bangladeshis’ visits to London with the host community, and the significance of the events that unfold. Their VFR mobilities are in many ways quite different from the existing examples of ‘hosting practices’, particularly in the European context, that have been studied. Inherent power imbalances, lack of access to ‘network capital’, the generational gap and the hidden tensions of hosting relatives and friends from the home country in a diasporic space are the key contrasts. Finally, I look into the concomitants of VFR mobilities, including issues of identity, home-making and materialities that are embedded in the bilateral VFR trajectories, and associated tensions and perspectives for the future. The thesis contributes new theoretical and empirical insights into the phenomenon and epistemology of VFR mobilities. Such mobilities, and their correlate of immobilities, unfold in a highly unequal transnational geopolitical and economic context, and add a much-needed novel perspective to a field dominated by western-centric research among relatively free-moving tourists, lifestyle and professional migrants, and members of diasporas

Memoryscapes of the homeland by two generations of British Bangladeshis

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When migrants become hosts and nonmigrants become mobile: Bangladeshis visiting their friends and relatives in London

Most studies of migrants visiting their friends and relatives (VFR) are on homeland visits. In this article, we reverse the transnational optic and study nonmigrants from the country of origin visiting their migrated friends and relatives abroad. We draw on participant observation and 57 interviews with migrant hosts and nonmigrant visitors carried out in London and in the Sylhet region of Bangladesh. Visits from the homeland to the diaspora are found to be deeply meaningful for the maintenance of transnational familyhood, especially at critical moments such as weddings, childbirth, and end of life. They are performative acts of belonging with unwritten rules of mutual obligations and choreographed itineraries to the houses of relatives and friends and to tourist sites. They also represent inequalities in economic status and social mobility between the migrants and their left‐behind relatives and friends in Bangladesh. Most visits are enjoyable for all concerned, but subtle tensions can arise, for instance, in the hosts' difficulty in managing their ongoing working lives with duties of hospitality and acting as guides and in visitors' intense schedule of duty visits to many relatives and lack of agency in stepping out of the Bangladeshi community in London. Furthermore, in an increasingly hostile environment for getting visas to visit the United Kingdom, an unequal and inhumane situation arises of blocked mobility

Disrupted mobilities: British-Bangladeshis visiting their friends and relatives during the global pandemic

The COVID-19 pandemic severely disrupted the cross-border mobilities of people and materials. The ramifications of such a sudden large-scale disruption of mobilities were hugely significant for migrants’ and diasporic citizens’ transnational way of life. Being ‘here’ and ‘there’ and maintaining intimate personal, familial and social ties between people and places transnationally suddenly became virtually impossible, and some of these blockages and brakes to mobility continue. National lockdowns by many countries across the globe and the virtual halting of international travel severely limited people’s capacity to physically travel. Visiting geographically distant relatives and friends, meeting them face-to-face and fulfilling cultural obligations and duties, such as providing care or attending a funeral, became very challenging. In this chapter, I examine the disruptions of human spatial-temporal mobilities of visiting friends and relatives (VFR) between members of the British-Bangladeshi diaspora in London and their home country, Bangladesh. Drawing from interviews both in-person and online via Zoom and WhatsApp, I analyse and interpret the complex experiences of their visits and the consequences of enforced immobilities for individuals and families during the pandemic

‘It's just a natural human thing to do, to go and visit your family… but it's not easy for us’: gender and generation in Bangladeshis’ transnational visits between London and Sylhet

In the title to this paper, Maya, a British-Bangladeshi woman, expresses her frustration at the refusal of the Home Office to grant her father in Sylhet a visa to come and fulfil his role as family head at the wedding of his son, Maya's brother, in London. The case illustrates well the intersection of gender and generation that fundamentally shapes the pattern of visits, in both directions, across this long-distance transnational social and family space. Bangladesh is a patriarchal society, with marked gender divisions layered across generations, which are largely reproduced among the migrant community in London and are manifested, in various ways, in the phenomenon of transnational visiting. Based on 61 in-depth interviews in London and Sylhet, supplemented by participant observation, we delineate the gendered and generational structures framing the visits, both of migrants to the homeland and of non-migrants to their relatives in London

Effect of different cutting depths to the cutting forces and machining quality of CFRP parts in orthogonal cutting ─ a numerical and experimental comparison

The necessity of understanding the influence of cutting variables in orthogonal cutting of Carbon Fiber Reinforced Polymer (CFRP) is vital because of their significant influences to the quality of manufactured parts. In this present research work the influences of different cutting depths to the cutting and thrust forces have been analyzed and a comparison between an equivalent homogeneous material (EHM) macro-model and experimental results have been made. The reasons of the beginning high cutting and thrust forces have been studied and explained. The post analysis of the experimental machined surfaces has been done to analyze the generated surface roughness and fiber-matrix interface crack generation. Five different cutting depths and four individual fiber orientations have been tested both numerically and experimentally. Significant influence of cutting depths to the cutting force has been found and the surface quality of newly generated machined part is discovered as a function of cutting depth and fiber orientation

Editorial introduction: relocating east–west migration and (im)mobilities

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Recommending research articles: A multi-level chronological learning-based approach using unsupervised keyphrase extraction and lexical similarity calculation

A research article recommendation approach aims to recommend appropriate research articles to analogous researchers to help them better grasp a new topic in a particular research area. Due to the accessibility of research articles on the web, it is tedious to recommend a relevant article to a researcher who strives to understand a particular article. Most of the existing approaches for recommending research articles are metadata-based, citation-based, bibliographic coupling-based, content-based, and collaborative filtering-based. They require a large amount of data and do not recommend reference articles to the researcher who wants to understand a particular article going through the reference articles of that particular article. Therefore, an approach that can recommend reference articles for a given article is needed. In this paper, a new multi-level chronological learning-based approach is proposed for recommending research articles to understand the topics/concepts of an article in detail. The proposed method utilizes the TeKET keyphrase extraction technique, among other unsupervised techniques, which performs better in extracting keyphrases from the articles. Cosine and Jaccard similarity measures are employed to calculate the similarity between the parent article and its reference articles using the extracted keyphrases. The cosine similarity measure outperforms the Jaccard similarity measure for finding and recommending relevant articles to understand a particular article. The performance of the recommendation approach seems satisfactory, with an NDCG value of 0.87. The proposed approach can play an essential role alongside other existing approaches to recommend research articles. Autho