1,721,006 research outputs found
Strain intermittency in shape-memory alloys
Get PDFWe study experimentally the intermittent progress of the mechanically induced martensitic transformation in a Cu-Al-Be single crystal through a full-field measurement technique: the grid method. We utilize an inhouse,
specially designed gravity-based device, wherein a system controlled by water pumps applies a perfectly monotonic uniaxial load through very small force increments. The sample exhibits hysteretic superelastic behavior during the forward and reverse cubic-monoclinic transformation, produced by the evolution of the strain field of the phase microstructures. The in-plane linear strain components are measured on the sample surface during the loading cycle, and we characterize the strain intermittency in a number of ways, showing the emergence of power-law behavior for the strain avalanching over almost six decades of magnitude. We also describe the nonstationarity and the asymmetry observed in the forward versus reverse transformation. The present experimental approach, which allows for the monitoring of the reversible martensitic transformation both locally and globally in the crystal, proves useful and enhances our capabilities in the analysis and possible control of transition-related phenomena in shape-memory alloys
Combining Hole-Drilling and Ring-Core Techniques
No full textThe hole-drilling and ring-core techniques are two well-known approaches to residual stress measurement. They apparently are complementary: in the former, a small hole is drilled in the specimen and residual stresses are estimated from the displacement/strain field around the hole; in the latter a small ring is milled and residual stresses are computed from the displacement/strain field inside the ring. However, owing to the different stiffness of the constraining region, their sensitivity and depth range are somewhat different.
Although both techniques are implemented using strain gauges, the use of optical methods is nowadays largely accepted. As optical methods allow acquisition of data from both inside and outside the ring, in this work, we will try to exploit the different displacement release rates of the two regions to optimize residual stress measurement
Residual Stress, Thermomechanics & Infrared Imaging, Hybrid Techniques and Inverse Problems, Volume 7. Proceedings of the 2018 Annual Conference on Experimental and Applied Mechanics
No full textA low-cost residual stress measuring instrument
No full textThe hole-drilling method is the approach most used for residual stress measurement and most of the commercially available instruments are based on this working principle. The idea is quite simple: drill a small hole on the surface of the components and measure the strain/displacement components resulting on the surface. The stress components can be estimated from these data with a reverse calibration process. The measurement of the displacement/strain field is usually performed using either strain gauges or interferometric optical methods, thus the cost of the instruments is significant.
Recently, it has been proposed to replace the interferometric method with an integrated Digital Image Correlation (i-DIC) approach: by using problem-specific displacement functions, all difficulties related to the low sensitivity of DIC are avoided and the measurement procedure simply requires acquisition of an image after each drilling step. This paper describes the development of a low-cost instrument based on this working principle: the imaging subsystem is based on a Raspberry-Pi camera module whereas step motors are controlled by an Arduino board. Finally, the frame is built using a 3d-printer
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
A Spatio-temporal Approach for iDIC-Residual Stress Measurement
No full textRecently, the Integrated-Digital Image Correlation (iDIC) has been proposed as a simple and effective approach for residual stress measurement. iDIC is a variant of the classical Digital Image Correlation where the “standard” displacement functions are replaced by problem-specific ones. By this simple modification, stress components become the unknowns of the problem, thus allowing a single-pass analysis. However, implementation of the Integral Method for estimation of depth-dependent Residual Stress components is difficult. In particular, the Least Squares approach is not possible.
This work suggests a two-pass approach: in the former the direct solution of the triangular linear system is solved. In the latter, the previous estimates are used as starting point for a global minimization involving all the acquired images
Variations on the Author
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
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