Search Results (10)

In recent years, there has been a lack of information in the literature regarding the extrusion and connection of closed profiles from oxygen-free copper in bridge dies. Available studies contain information on the processes of extrusion and connection of profiles from aluminium alloys and various types of steel. However, there is a lack of detailed data on the values of technological parameters for which copper is joined in the extrusion process. Therefore, one of the goals of this work is to fill the gap in the literature regarding the extrusion of oxygen-free copper in bridge dies. In this work, the authors determined the thermo-mechanical conditions at which oxygen-free copper will be joined. This paper describes the effects of charge temperature and hydrostatic pressure in the weld zone of a bridge die on copper bonding in the fabrication of tubular profiles. Physical tests of the welding process under the conditions of upsetting a material consisting of two parts were carried out using the Gleeble 3800 metallurgical process simulator with the PocketJaw module in the standard configuration for SICO (strain-induced crack opening) tests. For the numerical simulations, the commercial computer programme FORGE^®NxT 2.1. using the finite element method (FEM) was used. Based on the analysis of the test results obtained, it was found that complete material bonding during the extrusion process could be achieved for a charge temperature higher than 600 °C and a hydrostatic pressure of 45–65 MPa. Full article

The Roman Baths of Valduno (Spain) possess significant educational potential, as recognized by visitors in a previous study, even though the facilities have not been maintained properly or have not been given enough publicity , which has resulted in their neglect. Through participation in a school project, a specific intervention is planned, following the ideas of community archaeology, regarding the study and dissemination of the Baths by following the ideas of community archaeology throughout. This study aims to analyse the impact this intervention has on 16 students regarding their knowledge of heritage and the bonds forged and reinforced concerning the site, as well as to identify the difference in historical knowledge acquired after a classroom explanation of the Baths and an open guided tour focused on the interests of the students. A case study was designed following the educational ethnography method, as it facilitates daily attendance as well as close observation of the case in question. The instruments developed (a register for participant observation and a semi-structured interview) reveal that symbolic appropriation of the site occurs as interaction and related knowledge increase. Furthermore, open guided tours facilitate greater significant learning in contrast to a classroom explanation on a heritage site. Educational experiences that embrace experimental, transdisciplinary, and participative methodologies contribute to a holistic understanding of heritage. Full article

Ludwig Henry Bojanus was born on 16 July 1776 in Buchsweiler, Alsace. After studying in Jena and Vienna, L. H. Bojanus enrolled at the University of Jena for his doctoral studies. Bojanus’s scientific activities are closely associated with Vilnius, where he was a professor of veterinary medicine from 1806 (he was elected to this position in 1804). In 1815, he became a professor of comparative anatomy. These were the times of the greatest flourishing of Vilnius University, where the foundations of modern Polish science were being laid. At Vilnius University, he established a technical and anatomical-pathological office for the zoo, a veterinary clinic and a model forge for shoeing horses in 1823. Bojanus founded a veterinary school in Vilnius and drew up a plan for a veterinary institute, which was not opened until 1832, simultaneously with the opening of the medico-surgical academy. He became known as one of Europe’s most prominent anatomists and zoologists. A lasting memorial to the scientist is the monograph “Anatomy of the Tortoise”, which many scholars still point to today as a model of accurate and precise anatomical research. He was the first to identify the anatomical differences between the European bison (Bos bonasus) and the aurochs (Bos primigenius). In his lectures on comparative anatomy, Bojanus presented the principle of uninterrupted development. He can be described as one of the most decisive and consistent evolutionists before Darwin. He died in 1827. Full article

Since the late 1970s, the term Orientalism has been closely associated with Edward Said (d. 2003) and his influential monograph of the same name. First published in 1978, Orientalism advanced a number of critiques about the discipline of “Oriental Studies”, its frequently condescending portrayal and depiction of the Eastern world, and the complex relationship between knowledge and power in the context of the Middle East. As revolutionary as a number of Said’s theses have been, in his critique of Orientalism and in particular his penetrating analysis of the relationship between knowledge and power, Said was not breaking entirely new ground. In fact, seven decades earlier, a voice from the Orient itself, the Persian Bahā’ī scholar Mīrzā Abu’l-Faḍā’il-i Gulpāyigānī (d. 1914), expressed a similar, albeit embryonic, critique of Orientalism. Abu’l-Faḍā’il’s analysis, presented in the opening chapters of his final book Kashfu’l-Ghiṭā’, focused on one of the foremost Orientalists of his time, the Cambridge scholar Edward Granville Browne (d. 1926). Rather than studying the extent to which Browne fits the paradigm of Orientalism (a topic some scholars have previously expressed views on), this article explores ways in which Abu’l-Faḍā’il’s critique of Browne’s study of the Orient can be viewed as a nascent prefiguration of some of the theses developed and advanced by Said decades later. Gulpāyigānī’s precedence as a Bahā’ī scholar in discerning and addressing the link between Western scholars’ knowledge production and the colonial power relations of their respective governments with the countries or areas they studied, helps correct a misconception forged about Bahā’īs. Historical narratives produced in anti-Bahā’ī polemics decades after Gulpāyigānī’s death created a master-narrative that cast Bahā’īs as agents of colonial powers, sweeping under the rug counterarguments such as those posed by Gulpāyigānī’s critique. The authors of this article have been motivated by this corrective goal. Full article

Increasing demand for manufactured goods in industries such as automobiles, electronics, construction, and aerospace has motivated researchers to develop sustainable manufacturing processes. Most metal-forming lubricants are not eco-friendly; they may cause substantial chemical emissions and constitute a community threat. Bio-oil lubricants are seen as possible replacements for mineral oil-based lubricants. Computational modelling of the forging process uses the finite element method to accelerate and improve design. This research intends to act as a case study and demonstrate how friction behaves differently in open-closed forging tests of different palm oil derivatives. The relationship between the different types of friction was studied using a cold forging test in conjunction with the development of a Coulomb–Tresca friction model. From the results, it can be shown that the friction behavior for the closed forging test (CFT) and the ring compression test (RCT) differs; the CFT exhibits a diversified friction adaptation, while the RCT exhibits a single friction adaptation. From both tests, palm stearin (PS) shows the lowest friction behavior where at RCT the friction is estimated at m = 0.10/μ = 0.05 and the CFT has a varied friction and the average friction is estimated at m = 0.352/μ = 0.1626. On the other hand, commercial metal-forming oil (CMFO) shows the highest lubrication sample in friction, where the value of friction is similar to the no lubricant sample (NA-O), which is (m = 0.45/μ = 0.1875) on the RCT test and (m = 0.424/μ = 0.1681) on the CFT test. Full article

The aim of this manuscript is the experimental and numerical study regarding the influence of friction conditions on plastic deformation behavior by upsetting the A6082 aluminum alloy. The upsetting operation is characteristic of a significant number of metal forming processes: close die forging, open die forging, extrusion, and rolling. The purpose of the experimental tests was to determine: by the ring compression method, the friction coefficient for 3 surface lubrication conditions (dry, mineral oil, graphite in oil) by using the Coulomb friction model; the influence of strains on the friction coefficient; the influence of friction conditions on the formability of the A6082 aluminum alloy upsetted on hammer; study of non-uniformity of strains in upsetting by measuring hardness; change of the tool-sample contact surface and non-uniformity of strains distribution in a material by numerical simulation. Regarding the tribological studies involving numerical simulations on the deformation of metals, they mainly focused on the development of friction models that characterize the friction at the tool-sample interface. The software used for the numerical analysis was Forge@ from Transvalor. Full article

Brain synchronizations are orchestrated from neuronal oscillations through frequency interactions, such as the alpha rhythm during relaxation. Nevertheless, how the intrinsic interaction forges functional integrity across brain segregations remains elusive, thereby motivating recent studies to localize frequency interactions of resting-state fMRI (rs-fMRI). To this point, we aim to unveil the fMRI-based spectral interactions using the time-frequency (TF) analysis; however, Fourier-based TF analyses impose restrictions on revealing frequency interactions given the limited time points in fMRI signals. Instead of using the Fourier-based wavelet analysis to identify the fMRI frequency of interests, we employed the Hilbert–Huang transform (HHT) for probing the specific frequency contribution to the functional integration, called ensemble spectral interaction (ESI). By simulating data with time-variant frequency changes, we demonstrated the Hilbert TF maps with high spectro-temporal resolution and full accessibility in comparison with the wavelet TF maps. By detecting amplitude-to-amplitude frequency couplings (AAC) across brain regions, we elucidated the ESI disparity between the eye-closed (EC) and eye-open (EO) conditions in rs-fMRI. In the visual network, the strength of the spectral interaction within 0.03–0.04 Hz was amplified in EC compared with that in EO condition, whereas a canonical connectivity analysis did not present differences between conditions. Collectively, leveraging from the instantaneous frequency of HHT, we firstly addressed the ESI technique to map the fMRI-based functional connectivity in a brand-new AAC perspective. The ESI possesses potential in elucidating the functional connectivity at specific frequency bins, thereby providing additional diagnostic merits for future clinical neuroscience. Full article

This study investigates three processes of multidirectional forging (MDF), namely, closed MDF (CMDF), single-open MDF, and double-open MDF, by using a constitutive equation and a dynamic recrystallization model of hot deformation of the GH4169 superalloy. The microstructure evolution of the three processes is simulated and compared. Among the three processes, the double-open MDF obtains the highest recrystallization degree, followed by the CMDF and the single-open MDF under the same reduction. The recrystallization degree of CMDF reaches 99.5% at 1000 °C and 9 passes, and the average recrystallized grain size is small, which is approximately 8.1 μm. The double-open MDF can obtain a fine grain size of forgings at 9 passes and 1000 °C, and it is easy to obtain forgings with the single-open MDF with uniform performance. The temperature is 850 °C–1000 °C, the compression rate is 0.15–0.2, and the pass is 5–9, which are the suitable parameter selection ranges for the CMDF. The temperature is 950 °C–1000 °C, the compression rate is 0.1–0.2, and the pass is 7–9, which are the suitable parameter selection ranges for single-open MDF. The temperature is 850 °C–1000 °C, the compression rate is 0.1–0.2, and the pass is 6–9, which are the suitable parameter selection ranges for the double-open MDF. Full article

Feasibility studies have been performed on ingots with reduced hot-top heights for the cost-effective hot forging of heavy ingots. The quality of the heavy ingots is generally affected by internal voids, which have been known to be accompanied by inclusions and segregation. To guarantee the expected mechanical performance of the forged products, these voids should be closed and eliminated during the hot open die forging process. Hence, to effectively control the internal voids, the optimum hot-top height and forging schedules need to be determined. In order to improve the utilization ratio of ingots, the ingot hot-top height needs to be minimized. To investigate the effect of the reduced hot-top height on the forged products, shaft and bar products have been manufactured via hot forging of ingots having various hot-top heights. From the operational results, the present work suggests effective forging processes to produce acceptable shaft and bar products using ingots having reduced hot tops. The mechanical properties of shop-floor products manufactured from ingots with reduced hot tops have also been measured and compared with those of conventional ingot products. Full article

In recent years, a large number of metal foams and porous metals have been developed. Due to the high cost of these materials alternative manufacturing methods for cellular metallic materials are being explored. Crumpled metallic foil meshes, manufactured via die compression techniques, are evolving as a potential alternative method. However, the non-availability of sufficient data on their load response is limiting their uptake. Uniaxial compressive load response of crumpled aluminium foil meshes (CAFMs) of varying densities, forged by open and closed die compression, are studied. A 0.05 mm thick aluminium sheet mesh, manufactured by the expanded metal process is used. X-ray computed micro-tomography is employed to image the CAFM’s internal cellular structure. The stress-strain relation demonstrates that the CAFMs produce identical load response profile irrespective of their relative density. Power law functions $E_R=17110{\rho }_r{}^{3.6547}$ and ${\sigma }_{Y,E}=53.092{\rho }_r{}^{2.2249}$ define the relationships between real Young’s Modulus $E_R$ and effective yield strength, ${\sigma }_{Y,E}$ . The study provides new knowledge on the effect of relative density on the compressive properties of CAFMs which have applications across lightweight structural design. Full article