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排序方式: 共有842条查询结果,搜索用时 8 毫秒
31.
He-zong Li Xiang-huai DongYu Shen Rui ZhouAlexander Diehl Hinnerk HagenahUlf Engel Marion MerkleinJian Cao 《Journal of Materials Processing Technology》2012,212(3):653-661
Microbending experiments of brass foils were conducted and demonstrated clear size effects, i.e., the normalized bending moment increased with the reduction of foil thickness. The experiments were modeled using the classical plasticity model and three strain-gradient plasticity models. A modified Nix-Gao model was proposed to consider the number of twins across the thickness direction in strain hardening. It was found that the proposed model could better predict the normalized bending moment for both fine-grain and coarse-grain foils and the proposed equation for material intrinsic length could better capture the physics of material deformation. Furthermore, micro-hardness distributions in the bending area were measured and obvious lower-hardness region was found in the middle layer of fine-grain foils instead of coarse-grain foils. This indicates that the modified Nix-Gao model and the assumption of fully plastic bending worked better for coarse-grain foils than for fine-grain foils. 相似文献
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Droplet impingement of urea water solution (UWS) is a common source for liquid film and solid deposits formed in the tailpipe of diesel engines. In order to better understand and predict wetting phenomena on the tailpipe wall, this study focuses on droplet spreading dynamics of urea water solution. Impingement of single droplets is investigated under defined conditions by high‐speed imaging using shadowgraphy technique. The experimental studies are complemented by numerical simulations with a phase‐field method. Computational results are in good agreement with experimental data for the advancing phase of spreading and the maximum and terminal spreading radius, whereas for the receding phase notable differences occur. For the maximum spreading radius, an empirical correlation derived for glycerol‐water‐ethanol mixtures is found to be valid for millimeter‐sized UWS droplets as well. A numerical simulation for a much smaller droplet however indicates that this correlation is not valid for the tiny droplets of UWS sprays in technical applications. 相似文献
34.
Software Quality Journal - 相似文献
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Kerim Isik Gregory Gerstein Thomas Schneider Robert Schulte Daniel Rosenbusch Till Clausmeyer Florian Nürnberger Milan Vucetic Sergej Koch Sven Hübner Bernd-Arno Behrens A. Erman Tekkaya Marion Merklein 《Production Engineering》2016,10(1):5-15
Sheet-bulk metal forming processes combine conventional sheet forming processes with bulk forming of sheet semi-finished parts. In these processes the sheets undergo complex forming histories. Due to in- and out-of-plane material flow and large accumulated plastic strains, the conventional failure prediction methods for sheet metal forming such as forming limit curve fall short. As a remedy, damage models can be applied to model damage evolution during those processes. In this study, damage evolution during the production of two different toothed components from DC04 steel is investigated. In both setups, a deep drawn cup is upset to form a circumferential gearing. However, the two final products have different dimensions and forming histories. Due to combined deep drawing and upsetting processes, the material flow on the cup walls is three-dimensional and non-proportional. In this study, the numerical and experimental investigations for those parts are presented and compared. Damage evolution in the process chains is simulated with a Lemaitre damage criterion. Microstructural analysis by scanning electron microscopy is performed in the regions with high mechanical loading. It is observed that the evolution of voids in terms of void volume fraction is strongly dependent on the deformation path. The comparison of simulation results with microstructural data shows that the void volume fraction decreases in the upsetting stage after an initial increase in the drawing stage. Moreover, the concurrent numerical and microstructural analysis provides evidence that the void volume fraction decreases during compression in sheet-bulk metal forming. 相似文献
37.
Marion Hersh 《AI & Society》2014,29(2):167-183
The paper discusses the limitations of engineering ethics as implemented in practice, with a focus on the fact that engineering and other activities are carried out without any consideration of whether the activities are themselves ethical, and on the gap between legality and ethics. This leads to the following three central ideas of the paper. The first is the need for engineers to both be aware of and critique their own values and be able to widen their perspective to that of the ‘other’, i.e., marginalised and minority groups and the environment. This understanding of the ‘other’ and values is also applied to the discussion of ethical issues relating to minority world (‘developed’) country engineers working in majority world (‘developing’) countries. The second central idea is the fact that structural and contextual factors in the form of barriers and enablers affect ethical values and practices. Individuals are not necessarily unethical in themselves, but the context and organisational ethos may present barriers to ethical behaviour and encourage the development of unethical values. These barriers and enablers are investigated through a pilot survey. The third central idea is the relationship between individual and collective responsibility and the need for support to enable engineers to think and behave ethically. 相似文献
38.
The numbers of English public houses or “pubs” have reduced significantly in the last two decades. Politicians have called on the planning system to resist their closure but, at the same time, demand further controls over high-street bars. This paper explores the reasons for the decline and the rationale for supporting the continuation of the “traditional” English pub. Using evidence drawn from a wider study of the relationships between places and youth drinking cultures, the paper discusses young adults' use of pubs. While recognising the adverse effects of heavy drinking, arguments are put forward in support of the traditional pub as a site for restrained and responsible social interaction for young adults. The paper discusses the issues this raises for the UK planning system in the context of responsibilities for social sustainability and public health. 相似文献
39.
Jian Cao Ekkard Brinksmeier Mingwang Fu Robert X. Gao Biao Liang Marion Merklein Michael Schmidt Jun Yanagimoto 《CIRP Annals》2019,68(2):605-628
Forming is widely used due to its high efficiency in material utilization and its high production rate in general. Most forming processes control the geometry of final products through a set of tooling. The increasing demands on lightweight products have challenged the performances and functionalities of tooling. This paper provides a systematic review of recent advancements related to tooling performance and functionalities, including tool materials, tooling fabrication processes (e.g., machining, heat treatment, coating, surface texturing, and additive manufacturing), sensing, and data analytics. Finally, recommendations on future research directions for metal forming tooling are provided. 相似文献
40.
Fei Huang Tomáš Halenkovič Marion Baillieul Virginie Nazabal Petr Němec Josef Havel 《Journal of the American Ceramic Society》2022,105(3):1992-2000
Quaternary germanium-antimony-selenium-tellurium (Ge-Sb-Se-Te) thin films deposited from Ge19.4Sb16.7Se63.9−xTex (x = 5, 10, 15, and 20) glass-ceramics targets by radio frequency magnetron sputtering were studied using laser ablation quadrupole ion trap time of flight mass spectrometry. Binary, ternary, and quaternary GeaSbbSecTed clusters were formed and their stoichiometry was determined. By comparison of the clusters obtained from quaternary Ge-Sb-Se-Te thin films and those from ternary Ge-Sb-Te materials, we found that Ge-Te species are not detected from the quaternary system. Furthermore, Ge-Se and Se-Te species are missing in mass spectra generated from Ge-Sb-Se-Te thin films. From the Ge-Sb-Se-Te thin films, 16 clusters were detected while ternary Ge-Sb-Se glasses yielded 26 species. This might be considered as a signal of higher stability of Ge-Sb-Se-Te thin films which is increasing with a higher content of Te. The missing (Se2+, GeaSb+ (a = 1–4), and GeSec+ (c = 1, 2)) and new (Ge+ and SbbTe+ (b = 1–3)) clusters may indicate that some of the structural features of the films (Ge2Se6/2 and Se2Sb-SbSe2) were replaced by (GeSe4−xTex and SbSe3−xTex) ones. In addition, when comparing the stoichiometry of clusters formed from Ge-Sb-Se-Te thin films with those from the mixtures of the elements, only Sb3+ and SbSe+ were observed in both cases. The knowledge gained concerning clusters stoichiometry contributes to the elucidation of the processes proceeding during plasma formation used for the chalcogenide thin films deposition. 相似文献