6,045 research outputs found
Audiomobiles, Sculptures and Conundrums
No full textRoberto Gerhard was a pioneer of electronic music in England creating a number of substantial concert, theatre and radio works from as early as 1954. Gerhard’s electronic music is one of the richest repositories for understanding the development of the composer’s late compositional technique. Apart from the Symphony no.3, ‘Collages’, none of Gerhard’s electronic music is published. This paper will discuss aspects of Gerhard’s electronic music, focusing on Audiomobiles (1958-59) and Sculptures (1963)
Evolución de las competencias gerenciales en la última década: un estudio sobre cambios en las competencias requeridas por los gerentes de la región centro de Argentina
No full textFil: Scorza, Federico. Universidad Nacional Villa María; Argentina.Fil: Pieckenstainer, Ana Laura. Universidad Nacional Villa María; Argentina.Fil: Mandelli, Roberto Nicolás. Universidad Nacional Villa María; Argentina
Roberto Gerhard’s Sound Compositions: A Historical-Philological Perspective. Archive, Process, Intent and reenactment
No full textThis research advances the current state of knowledge in the field of early tape music both empirically and methodologically. The purpose of this study is to evaluate the impact that the electronic medium exerted in the musical thinking of Roberto Gerhard, one of the most outspoken, prolific and influential composers in the Spanish diaspora whose musical legacy, for the most part unknown, is a major landmark in the early history of electroacoustic music. Gerhard’s personal tape collection, one of the largest historical archives of its kind reported in the literature, is exceptional for both its antiquity (50+-year-old tapes) and its abundance of production materials. Through the digitisation and analysis of the composer’s tape collection this research argues that the empirical study of audio documents sets out a basis for a broader understanding of textual processes. More specifically, the research demonstrates that the reconstruction of works based on magnetic tape sketches is a powerful method to advance the understanding of early tape music. This research also examines Gerhard’s sound compositions in relation to the post-war context in which they were composed. Finally, this research presents performance documentation that proposes an approach to the electroacoustic music repertoire in which creativity is not at odds with rigor and critical discernment demonstrating that archival study can be closely aligned to the concept of re-enactment
Numerical modelling of the fracture behaviour of brittle materials reinforced with unidirectional or randomly distributed fibres
No full textThe use of reinforcing fibres has shown to be an effective, simple and economic way to enhance the mechanical characteristics of brittle materials; in particular tensile strength, fracture and fatigue resistance, wear resistance and durability are usually noticeably higher in fibre-reinforced materials (FRC) with respect to unreinforced ones. For the above mentioned reasons composite materials today can replace or compliment other traditional structural materials.
On the other hand the extensive use of brittle matrix composite materials requires appropriate computational models to describe, with adequate accuracy, their mechanical behaviour. In the present paper a mechanical-based computational model for the description of the macroscopic behaviour of such a class of materials, composed by a matrix phase and a fibre-reinforcing phase, is formulated. By considering a micromechanical-based model, the macro constitutive equations of unidirectional or randomly distributed fibres reinforced materials are obtained by taking into account the possibility of crack formation and propagation in the matrix as well as fibre debonding and breaking. The developed computational model is finally used in some numerical simulations in order to outline its reliability in the assessment of both the fibre-matrix interaction phenomenon as well as the fracture failure prediction capability in brittle matrix FRC materials
A MICRO-MECHANICAL MODEL FOR STATISTICALLY UNIDIRECTIONAL AND RANDOMLY DISTRIBUTED FIBRE-REINFORCED SOLIDS
No full textThe use of reinforcing fibres in structural materials has been known since ancient time as an effective, simple and economic way to enhance their mechanical properties. Among the main mechanical characteristics that can be improved by such reinforcing techniques are tensile strength, the fracture and fatigue resistance, the wear resistance, the durability etc. can be referred. For the above-mentioned reasons, a tremendous effort in theoretical and experimental research on fibre-reinforced composite (FRC) materials has been made in order to develop suitable models capable of accurately describe the mechanical behaviour of such a class of materials, at least at a macroscopic level.
In the present paper, an energy-based homogenisation approach to model the mechanical behaviour of fibre reinforced materials is developed by considering the possibility of fibre debonding and breaking, in order to obtain the macro constitutive equations. Furthermore, the effective spatial distribution of the fibres is accounted for by using its description in terms of probabilistic concepts; the case of randomly spatial-oriented fibres is also considered as a particular case by introducing a uniform probability distribution function.
Some peculiarities of the model are outlined by discussing some simple examples in which the effects of different values of the involved parameters are considered
Effect of fibre arrangement on the multiaxial fatigue of fibrous composites: a micromechanical computational model
No full textStructural components made of fibre-reinforced materials are frequently used in engineering
applications. Fibre-reinforced composites are multiphase materials, and complex mechanical phenomena take
place at limit conditions but also during normal service situations, especially under fatigue loading, causing a
progressive deterioration and damage. Under repeated loading, the degradation mainly occurs in the matrix
material and at the fibre-matrix interface, and such a degradation has to be quantified for design structural
assessment purposes. To this end, damage mechanics and fracture mechanics theories can be suitably applied
to examine such a problem. Damage concepts can be applied to the matrix mechanical characteristics and, by
adopting a 3-D mixed mode fracture description of the fibre-matrix detachment, fatigue fracture mechanics
concepts can be used to determine the progressive fibre debonding responsible for the loss of load bearing
capacity of the reinforcing phase.
In the present paper, a micromechanical model is used to evaluate the unixial or multiaxial fatigue behaviour of
structures with equi-oriented or randomly distributed fibres. The spatial fibre arrangement is taken into account
through a statistical description of their orientation angles for which a Gaussian-like distribution is assumed,
whereas the mechanical effect of the fibres on the composite is accounted for by a homogenization approach
aimed at obtaining the macroscopic elastic constants of the material. The composite material behaves as an
isotropic one for randomly distributed fibres, while it is transversally isotropic for unidirectional fibres. The
fibre arrangement in the structural component influences the fatigue life with respect to the biaxiality ratio for
multiaxial constant amplitude fatigue loading. One representative parametric example is discussed
Mechanics of interface debonding in fiber-reinforced materials
No full textThe evaluation of damage in multiphase materials plays a crucial role in their safety assessment under service mechanical actions. In this context, the quantification of the damage associated to fibre–matrix detachment is one of the most important aspects to be carried out for short fibre-reinforced materials. In the present article, the problem of progressive fibre–matrix debonding is examined and a mechanics interpretation of such a phenomenon is developed by relating the shear-lag and the fracture mechanics approach in order to determine the fibre–matrix interface characteristics. A multiscale approach is employed: at macroscopic level, composites with dilute dispersed fibres, arranged in a undirectional or in random orientation, are analysed through a homogenization approach, whereas the problem of axisymmetric debond growth in short fibres is examined at microscopic level. Moreover, a ‘structured’ linear elastic interface framework model for crack propagation analysis is applied by defining a microscopic truss structure, enabling to relate each other the classical shear strength approach and the fracture mechanics approach. Finally, a fibre pull-out test and some simple fibre-reinforced structural components are examined. This new proposed point of view on the debonding phenomenon allows a deep understanding of the mechanics of the fibre–matrix interface and enables to characterize such an interface layer that has a relevant role in mechanics design of composites materials
Micromechanical model for preferentially oriented short fibre-reinforced materials under cyclic loading
No full textThe safety assessment of short-fibre-reinforced (SFR) composites, commonly used in structural
applications involving repeated loads, requires to evaluate the degrading phenomena
taking place in the matrix and at the fibre–matrix interface. The mechanical behaviour
under both static and cyclic loading can be simulated applying damage degradation to
the matrix mechanical characteristics, and employing fracture mechanics concepts to
examine the fibre–matrix detachment as a 3D growing crack with degrading interface
properties. In the present paper, a micromechanical model for unidirectional or random
SFR materials under fatigue is developed. Some applications related to SFR polymeric
composites found in the literature are presented
Micromechanical crack growth-based fatigue damage in fibrous composites
No full textA partially debonded fibre can be analysed as a 3-D mixed Mode fracture case, for which the fibre–matrix
detachment growth – leading to a progressive loss of the composite’s bearing capacity – can be assessed
through classical fatigue crack propagation laws. In the present research, the above mentioned case is
firstly examined from the fracture mechanics theoretical point of view, and the effects of the stress field
in the matrix material on the Stress Intensity Factors – SIFs – (associated to the crack representing the
fibre–matrix detachment) are taken into account. Fatigue effects on the matrix material are accounted
for by means of a mechanical damage, quantified through a Wöhler-based approach. A damage scalar
parameter aimed at measuring the debonding severity during fatigue process is also introduced.
Finally, some numerical simulations are performed, and the obtained results are compared with
experimental data found in the literature
A COMPUTATIONAL MODEL FOR THE MECHANICAL BEHAVIOUR OF BRITTLE MATRIX MATERIALS WITH UNIDIRECTIONAL OR RANDOMLY DISTRIBUTED FIBRES
No full textIn the present paper, a computational model for brittle-matrix fibre-reinforced composite (FRC) materials is discussed. The main mechanical phenomena involved, such as matrix cracking, fibre orientation effect, fibre debonding and failure, and fibre-fibre interaction, are modelled by taking into account the micromechanical behaviour of such a class of materials. The developed mechanical model is implemented through a computational approach in the context of the finite element method. The proposed approach seems to be very effective making use of typical mechanical quantities related to the FRC materials (fibre content, strength, orientation, etc.). The results obtained provide useful information on the state of the composite, such as the matrix crack pattern, the effectiveness fibre content, the sliding function, the fibre length at failure
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