1,720,966 research outputs found
Fatigue crack growth behavior of cracked aluminum plate repaired with composite patch
No full textIn this study, we investigated the fatigue crack growth behavior of cracked aluminum plate repaired with bonded composite patch especially in thick plate, Adhesively bonded composite patch repair technique has been successfully applied to military aircraft repair and expanded its application to commercial aircraft industry recently. Also this technique ha:; been expanded its application to the repair of load bearing primary structure from secondary structure repair. Therefore, a through understanding of crack growth behavior of thick panel repaired with bonded composite patch is needed. We investigated the fatigue crack growth behavior of thick panel repaired with bonded composite patch using the stress intensity factor range (DeltaK) and fatigue crack growth rate (da/dN). The stress intensity factor of patched crack was determined from experimental result by comparing the crack growth behavior of specimens with and without repair. Also, by considering the three-dimensional (3D) stress state of patch crack, 3D finite element analyses were performed to obtain the stress intensity factor of crack repaired by bonded composite patch. Two types of crack front modeling, i.e. uniform crack front model and skew crack front model, were used. The stress intensity factor calculated using FEM was compared with the experimentally determined values. (C) 2002 Elsevier Science Ltd. All rights reserved
Damage detection of CFRP laminates using electrical resistance measurement and neural network
No full textAs carbon fibers are electrical conductors, the measurement of the electrical resistance appears to be a valuable technique for the in situ detection of various types of damage in carbon fiber reinforced polymers (CFRP) laminates. In such cases, carbon fibers are both the reinforcement and the sensor to detect damage in CFRP laminates. The damage-detecting method of CFRP laminates by electrical resistance measurement that an investigated in this study is made possible by attaching electrodes on the surface of the CFRP structures without special manufacturing. In this paper, we investigate the electrical resistance change as a damage parameter of fatigue damage such as the degradation of residual strength and stiffness. The measured stiffness and electrical resistance change during fatigue tests showed a very similar trend of change. This is because cumulative fatigue damage is represented by the degradation of residual stiffness;; these damages also cause change in electrical resistance. Thus, we can use this change in electrical resistance as a damage parameter. We also predict the future damage of composite laminates in fatigue loading from electrical resistance damage model by following a stiffness degradation model. Electrical resistance gradually increased as the stiffness reduced, and showed a very abrupt change when final fatigue failure was imminent. The predicted value showed good agreement with the experimental data except in the final stage, where stiffness and electrical resistance changed abruptly. (C) 2000 Published by Elsevier Science Ltd
A study on the buckling and postbuckling control of composite beams with embedded NiTi actuators
No full textIn this paper, an experimental study on the buckling and postbuckling control of a laminated composite beam with eccentrically embedded NiTi actuators is performed. For the purpose of enhancing the critical buckling load, buckling control is investigated through the use of reactive moment associated with the shape recovery force of NiTi actuators. To improve the control authority for the buckling and postbuckling control of the NiTi-composite beam, closed-loop control is used. The buckling and postbuckling control behaviours are presented and discussed qualitatively and quantitatively on load-deflection plots considering stacking sequence of the laminate, slenderness ratio of the beam and activation conditions of the NiTi actuators. The experimental results show that the buckling control can be extended to the postbuckling of the NiTi-composite beam with the proper reactive moment
Effect of embedded optical fiber sensors on transverse crack spacing of smart composite structures
No full textIn this study the effect of the presence of embedded optical fiber sensors on the transverse cracking of cross-ply laminates was investigated. The transverse crack spacing of cross-ply laminates with embedded optical fiber sensors was predicted using modified shear-lag analysis considering the presence of optical fibers and compared with experimental results. The effect of the orientation and quantity of optical fibers was evaluated and the effect of the coating of optical fiber was also investigated. Specimens were made with transparent glass/epoxy prepreg because the transverse crack and other damages such as delamination, splitting and bleeding of laser can be examined directly and visually. It has been found that the transverse crack spacing was not affected significantly by the embedding of optical fibers at low volume fraction of optical fibers. However, the cracks of specimens with embedded optical fibers which were initiated at a slightly lower stress level showed smaller spacing at the same stress level than those of specimens without embedded optical fibers. The theoretical crack spacing evaluated from the shear lag analysis showed good agreements with experimental results.
The active buckling control of laminated composite beams with embedded shape memory alloy wires
No full textIn this paper, the results of an experimental analysis on the active buckling control behaviour of a laminated composite beam with embedded shape memory alloy (SMA) wires are presented, For the purpose of enhancing the critical buckling load, active buckling control was investigated through the use of the reaction time associated with the shape recovery force of SMA wires. An increased critical buckling load and altered deflection shape due to the effects of activation of embedded SMA wires are represented qualitatively and quantitatively on the load deflection behaviour records. The results obtained from this active buckling control test confirm that the buckling resistance in a composite beam with embedded SMA wires can be increased by the use of an activation force of the embedded SMA wires. Based on our experimental analysis, a new formula for the behaviour control of active buckling in a laminated composite beam with embedded SMA wires is also suggested. (C) 2000 Published by Elsevier Science Ltd
Application of point and distributed optical fiber sensors to health monitoring of smart structures
No full textPoint optical fiber sensors are useful in the monitoring of localized structural damage, but a large number of the sensors must be multiplexed for large structure monitoring. On the other hand, distributed optical fiber sensors can obtain a continuous distribution of strain or temperature with one sensing fiber, and they are suitable for the large structure monitoring due to their measurement range reaching tens of kilometers. However, the distributed sensors have the spatial resolution of tens of centimeters to several meters, and they measure averaged strain or temperature. In this paper, the application results of transmission-type extrinsic Fabry-Perot interferometric (TEFPI) optical fiber, sensors and Brillouin distributed optical fiber sensors to structural monitoring are presented. The TEFPI optical fiber sensors and Brillouin distributed sensors were applied to the fatigue damage monitoring of an aluminum plate patched with CFRP composite and the deflection monitoring of an aluminum-bending beam, respectively
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
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