1,721,087 research outputs found
New geometry-inspired numerical convex analysis method for yield functions under isotropic and anisotropic hardenings
No full textConvexity of a yield function must be guaranteed to ensure unique relationship between plastic strain increments and stress components. A geometry-inspired numerical convex analysis (GINCA) approach is developed to analyze the convexity of a yield function. The numerical approach is verified by the computation of convex domains for several typical yield functions of Drucker, Cazacu-Barlat2004, Hu2017, Cazacu2018 and a newly proposed function for differential-anisotropic hardening. The verified GINCA is applied to analyze the convexity of the Gao2011 yield function since it was not determined yet. The numerical approach is also used to determine the convex domain evolution with respect to plastic deformation in an anisotropic hardening function. It is also applied to investigate the convexity of polynomial yield functions for strong anisotropic metals. The result shows that the GINCA can effectively and correctly compute the convex domain for different yield functions. Besides, the numerical approach only needs to compute the effective stress from a yield function without any computation of the first- and second-order partial derivatives, compared to the complicated convex analysis by the Hessian matrix. Therefore, the proposed GINCA is user-friendly, effective and accurate to analyze the convexity of a yield function both for isotropic hardening and anisotropic/differential hardening. The Matlab codes are shared as electric attachments for scientists and engineers to check the convexity of a yield surface under biaxial loading, plane stress with shear stress and triaxial loading conditions.
Graphene-enhanced sintering densification mechanisms in CoNiCrFeMn high-entropy alloys
No full textGraphene-reinforced high-entropy alloys (HEAs) have emerged as promising candidates for advanced structural applications, yet the atomic-scale mechanisms through which graphene nanoplatelets (GNPs) modulate densification and microstructural evolution during spark plasma sintering (SPS) remain poorly characterized. This study employs molecular dynamics (MD) simulations to unravel the sintering behavior of CoNiCrFeMn HEA composites with GNPs, demonstrating that GNPs significantly enhance sintered densification. The underlying mechanisms involve synergistic effects: GNPs act as effective dislocation pinning sites, inducing high-stress regions that promote alloy particle rearrangement and pore elimination; sintered GNPs form a three-dimensional network, enabling efficient heat transfer and mechanical interlocking with the HEA matrix to accelerate atomic diffusion; and the active graphene-HEA interface reduces surface energy, facilitating grain nucleation and refinement. Experimental results validate the MD simulations. These findings establish a critical link between interfacial interactions at the atomic scale and macroscopic densification kinetics, providing insights for optimizing SPS parameters in graphene/HEA composite fabrication
Exploring the bonding mechanism in cold spray deposition of engineered graphene nanoplates-Ni nanocomposite powder
Full text linkIn this work, molecular dynamics simulations were conducted to investigate deposition behavior of composite graphene nanoplatelets (GNPs)-Ni particles at various velocities and with different graphene contents. The results indicated that GNPs impede plastic deformation of the metallic particle and stress transfer to it, simultaneously limiting metallurgical bonding at the interface with the substrate. The particle/substrate bonding mechanism was a combination of metallurgical bonding and van der Waals forces physisorption, with the metallurgical bonding playing the primary role in adhesion strength. Increasing the impact velocity and decreasing the GNP content, both resulted in a larger area of metallurgical bonding, thereby enhancing the bonding strength. The particle/particle adhesion involves lateral and interlayer connections among GNPs, activating additional mechanical interlocking between the adjacent particles. Subsequent impact of the upcoming particles tamped the previously de..
Малый бизнес в Китае-проблемы и перспективы
Full text linkRadchuk, Anatoly Petrovich; Wu Pengfei. Small business in China - problems and prospect
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A stress-based shear fracture criterion considering the effect of stress triaxiality and Lode parameter
No full textFailure in lightweight metal forming is a big challenge currently and prevents their widely application in weight reduction of automobile and aerospace structures. A stress-based shear ductile fracture criterion is introduced in this study to improve the prediction accuracy of failure for lightweight metals. The criterion (sDF2016) is developed based on the DF2016 criterion thereby endowing the criterion with the precise fracture predictability under wide stress states of shear, uniaxial tension, plane strain tension and equibiaxial tension. Besides, the criterion takes into account the stress state effect on fracture in a form of the stress triaxiality, the maximum shear stress and the Lode parameter. The sDF2016 criterion is also expected to be less sensitive to strain path changing effect because sDF2016 describe the onset of fracture in stress space. For the verification of the pro-posed sDF2016 criterion, the experiments are carried out for AA5182-O sheet with central hole, notched, in -plane shear and bulging specimens. Plastic deformation is accurately modeled by the Swift-Voce hardening law and the Drucker yield function. The sDF2016 criterion is then calibrated both by the direct and inverse engineering approaches, which is applied to predict fracture initiation under distinct stress states. The modeled result indicates that the calibrated sDF2016 criterion based on the inverse engineering method predicts the fracture stroke with a higher accuracy than the direct approach. The sDF2016 criterion is also used to depict fracture limits of AA2024-T351 alloy from compression to tension. The application shows that the proposed ductile fracture criterion is capable of modeling the fracture limits for sheet metals under various loading con-ditions from shear to plane strain tension.
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
