1,720,963 research outputs found
Sub-surface damage location and identification using infra-red techniques
No full textThe paper presents a new methodology for identifying sub-surface damage in composite components using a combination of Pulse Phase Thermography (PPT) and Thermoelastic Stress Analysis (TSA)
Thermoelastic stress analysis of damage mechanisms in composite materials
No full textA methodology for the application of Thermoelastic Stress Analysis (TSA) in damage studies of glass reinforced polymers is established. Test specimens have been designed to promote certain damage types and the methodology applied to each. It is shown that a TSA approach can evaluate fibre breakage, matrix cracking and delamination damage. Metrics are established based on calibrated strain data obtained from the TSA. It is shown that these can be used to assess the condition of a component throughout its fatigue life.<br/
Prediction of fatigue life in composite materials using thermoelastic stress analysis
No full textThermoelastic Stress Analysis (TSA) is developed to provide a prediction of fatigue life in glass reinforced polymers. A test specimens has been designed to promote cracking and a methodology is defined that allows the measurement of the strain in the damaged region. It is shown that a TSA approach can evaluate fibre breakage, matrix cracking and delamination damage. A strain based metric is established based on calibrated data obtained from the TSA, which can be used to assess the condition of a component throughout its fatigue life
Damage monitoring of composite materials using pulsed phase thermography and thermoelastic stress analysis
No full textThe current paper presents a new combined technique for damage detection, localisation and establishing damage severity. The technique is based on the use of two infrared detection approaches: Pulsed Phase Thermography (PPT) and Thermoelastic Stress Analysis (TSA). A methodology is described that allows the technique to be applied to fibre reinforced composites. The usefulness of the technique is demonstrated on delaminated glass epoxy laminates. A means of developing controlled delamination damage in such specimens is developed so that real sub surface damage is evaluated in the paper
A temperature correction methodology for quantitative thermoelastic stress analysis and damage assessment
No full textIn thermoelastic stress analysis an infra-red detector is used to obtain the small temperature change resulting from the thermoelastic effect. The output from the detector, known as the thermoelastic signal, is dependent on both the surface stresses and the surface temperature of the component under investigation. For quantitative thermoelastic stress analysis it is important that the response resulting from changes in the surface temperature are decoupled from the response resulting from the stress changes. In this paper a means of decoupling the response is presented that involves making corrections for increases in surface temperature so that the thermoelastic signal is dependent only on the stresses. The underlying theory is presented and a correction factor is developed using an experimental approach. A methodology for applying the correction factor to full-field data is provided. The methodology is validated through a number of case studies and applied to a composite component subject to fatigue damage initiated at a central hol
A generalised approach to the calibration of orthotropic materials for thermoelastic stress analysis
Full text linkA review of thermoelastic theory associated with orthotropic solids is provided, the purpose of which is to develop a calibration procedure for thermoelastic stress analysis (TSA) that can be applied to laminated orthotropic composite materials. The procedure is based on the laminate strains rather than the surface ply stresses and enables a calibration approach that accounts simultaneously for the laminate mechanical response and the surface thermoelastic response. This calibration routine enables quantitative values of strain to be derived from thermoelastic data obtained from laminated composite structures. The calibration procedure is based on the use of simple tensile specimens. A variety of laminate stacking sequences are studied using E-glass epoxy pre-impregnated materials. Detailed material properties are obtained and the calibration procedure validated experimentally and theoretically.<br/
On the concept of a fully bonded coupon gauge for stress separation from thermoelastic data
No full textSeveral forms of gauge can be used for the determination of individual stresses from thermoelastic data alone. A particularly useful form of gauge is the ‘coupon gauge’, consisting of a thin coupon of material which is bonded to the stressed specimen (or substrate). A novel formulation of the thermoelastic response of the fully bonded thermoelastic coupon gauge is used as the basis for the appraisal of the four possible gauge–specimen material combinations. The validity of the principal assumptions underlying the performance of these gauges is demonstrated and it is shown experimentally that the behaviour of samples of the orthotropic gauge–isotropic specimen material combination conforms to theory.<br/
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
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