1,721,149 research outputs found
An innovative treatment of frictional contact and mixed-mode debonding problems based on IGA
No full textAn Innovative study of the debonding process for adhesively bonded interfaces under different loading conditions
No full textThe prediction of the interfacial failure mechanisms for adhesively bonded joints and composite structures is a well-known issue that has been studied both theoretically and/or numerically [1,2]. Small loads usually leave an adhesive junction bonded, where a jump of displacements is allowed due to the compliance of the interface. An increasing load, instead, can lead to adhesive breaks in one or more interface points where a crack starts and propagates along the interface, up to the complete detachment of the adherends.
This work focuses on the development of a new theoretical approach to determine the debonding onset and propagation along weak interfaces under different loading conditions. The interfacial problem is addressed by means of the cohesive crack modeling, assuming a linear- elastic behavior for the adherends and concentrating all non-linearities at the interface. This means that interfaces are considered as an assemblage of two sublaminates partly bonded together by an elastic interface. Such interface can be modeled as a continuous distribution of elastic springs acting along the normal and/or tangential direction depending on the interfacial loading condition. This generalizes the idea suggested recently in [3] for a single mode-I debonding.
The analytical predictions of crack advancement, length of the process zone, maximum load and load-deflection response, are compared to the numerical results as provided by a simple node- to-segment contact formulation. This is here generalized to handle cohesive forces along the normal and tangential directions, as employed in [4]. The very good agreement between analytical and numerical results confirms the accuracy of the theoretical proposed formulation
Numerical modeling of the debonding process of mixed-mode composite double cantilever beams
No full textNowadays, several engineering components are made of high performance laminated composites and adhesively bonded interfaces. One of the most serious damage modes of laminated structures is related to the non-linear and irreversible delamination process, including the formation and propagation of inter-laminar cracks, up to the complete detachment of the adhering parts.
This work focuses on the development of a new numerical formulation to determine the debonding onset and propagation along weak interfaces under different mixed-mode conditions. The interfacial problem is addressed by means of the cohesive crack modeling, concentrating all non-linearities at the interface. This means that interfaces are considered as an assemblage of two sublaminates, partly bonded together by an elastic interface, here modelled as a continuous distribution of elastic springs acting along the normal and/or tangential direction, depending on the interfacial mixed-mode condition. This generalizes the idea suggested recently in [1] for a single mode-I debonding, which is here extended to include mixed loading, geometrical and mechanical conditions.
The numerical predictions in terms of crack advancement, length of the process zone, maximum load and load-deflection response, are compared to the main results based on a frictional contact formulation. This is here generalized to handle cohesive forces along the normal and tangential directions, as employed in [2-4].
The very good agreement between the proposed numerical approach and a combined contact- debonding algorithm, confirms the feasibility and accuracy of the proposed formulation when studying delamination phenomena occurring within composite materials or laminated joints, usually subjected to mixed-mode conditions
Numerical study of the mixed-mode delamination of composite interfaces
No full textIn this work we propose a new numerical formulation to compute the de- lamination onset and propagation along weak interfaces under mixed-mode conditions. The interfacial problem is addressed through a cohesive crack model, concentrating all the non-linearities at the interface. The accuracy of the proposed formulation is verified against predictions of a combined contact-delamination algorithm
Advanced modeling of mixed-mode adhesive materials and interfaces
No full textAdhesive bonded joints have attracted the attention of many industries, such as marine and aerospace, as an interesting alternative to the traditional joining methods as riveting, bolting or welding. One of the most important damage modes of adhesive joints and interfaces is related to the non-linear and irreversible debonding process, which includes the formation and propagation of interface cracks, up to the complete detachment of the adherends.
In this framework, the interfacial debonding problem is here handled through an innovative cohesive formulation, named as Enhanced Beam Theory (EBT), where the specimens are considered as an assemblage of two composite sublaminates, partly bonded together by an elastic interface. This last one is modeled with a continuous distribution of cohesive springs acting in the normal and/or tangential direction, depending on the mixed-mode condition. This generalizes the idea suggested recently in [1] for a single mode-I debonding, and extended in [2] to include mixed loading, geometry and mechanical conditions. The debonding onset and propagation is determined numerically along the weak interfaces subjected to mixed-mode conditions. The accuracy of the proposed formulation is verified against some analytical predictions and theoretical formulations available in literature [3], [4]
Numerical modeling of the debonding process of mixed-mode composite double cantilever beams
No full textNowadays, several engineering components are made of high performance laminated composites and adhesively bonded interfaces. One of the most serious damage modes of laminated structures is related to the non-linear and irreversible delamination process, including the formation and propagation of inter-laminar cracks, up to the complete detachment of the adhering parts. This work focuses on the development of a new numerical formulation to determine the debonding onset and propagation along weak interfaces under different mixed-mode conditions. The interfacial problem is addressed by means of the cohesive crack modeling, concentrating all non-linearities at the interface. This means that interfaces are considered as an assemblage of two sublaminates, partly bonded together by an elastic interface, here modelled as a continuous distribution of elastic springs acting along the normal and/or tangential direction, depending on the interfacial mixed-mode condition. This generalizes the idea suggested recently in [1] for a single mode-I debonding, which is here extended to include mixed loading, geometrical and mechanical conditions. The numerical predictions in terms of crack advancement, length of the process zone, maximum load and load-deflection response, are compared to the main results based on a frictional contact formulation. This is here generalized to handle cohesive forces along the normal and tangential directions, as employed in [2-4]. The very good agreement between the proposed numerical approach and a combined contact- debonding algorithm, confirms the feasibility and accuracy of the proposed formulation when studying delamination phenomena occurring within composite materials or laminated joints, usually subjected to mixed-mode conditions
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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