1,721,119 research outputs found
Towards the development of a numerical code for the simulation of aircraft braking
No full textAtti del Dipartimento di Ingegneria Aerospaziale dell’Università di Pisa
CARATTERIZZAZIONE SPERIMENTALE DELLE ZONE DI RINFORZO INTORNO A GRANDI APERTURE DI FUSOLIERA" Collaborazione di ricerca fra il Dipartimento di Ingegneria Aerospaziale e la Alenia Aeronautica.
No full textDocumenti del Dipartimento di Ingegneria Aerospaziale DDIA 2006-22, Novembre 200
Analysis and Control of the Flexible Dynamics of Landing Gear in the Presence of Antiskid Control Systems
No full textModels of Wheel Contact Dynamics: an analytical study on the in-plane transient responses of a brush model
No full textThis paper deals with the dynamics of the contact between the pneumatic tyre and the ground, in particular with reference to braking manoeuvres of aircraft. The transient response of the braking force is analytically evaluated in terms of the transfer functions that link the variation of the braking force to the variation of physical inputs affecting the interaction between the tread and the ground, in the longitudinal plane. The proposed models have been formulated in order to account for the effects of different reference conditions of steady braking on gains, zeros and poles of such transfer functions
A NON-LINEAR MODEL FOR IN-PLANE SHEAR DAMAGE AND FAILURE OF COMPOSITE LAMINATES
No full textComposite material characterization is typically carried out by time-consuming and expensive experimental tests aimed at establishing strengths at both lamina and laminate levels. In this scenario, numerical analyses are valuable tools in order to reduce the number of tests and to gather, at the same time, knowledge about the complex interactions of the composite damage mechanisms.
The paper presents a new constitutive model for the non-linear shear behavior of composite laminates, which has been implemented in an user-defined Fortran routine (UMAT) to be used within ABAQUS non-linear FE code.
A numerical model of the ASTM Standard V-notch specimen shear test has been developed in order to identify the key parameters of the non-linear shear constitutive model. This has been achieved by means of a systematic comparison of the numerical results with experimental data. Material anisotropy and the geometry of the notch have been found to cause the shear strain field to be non-uniform in the notch section. This prevents a direct measure of the shear constitutive law parameters, which must be alternatively evaluated through an indirect procedure. A modified notch geometry, which mitigates strain non-uniformities, has been evaluated and assessed through numerical simulations
Modelli e metodi per lo studio della dinamica longitudinale del pneumatico
No full textAtti del Dipartimento di Ingegneria Aerospaziale dell'Università di Pis
Simulazione della dinamica dei carrelli e valutazione delle sollecitazioni in ambiente ADAMS
No full textDevelopment of analytical methods for fuselage design: validation by means of Finite Element analyses
No full textThe paper presents the results of a set of finite element analyses (FEAs) carried out to
support the development of an integrated design procedure that, based on semi-empirical and
analytical methods, is capable of defining generic fuselage sections of a transport aircraft. The
procedure, which is implemented in a structural optimization code, defines a structure that, compliant
with durability and damage tolerance requirements, is characterized by a post-critical behaviour of
the stiffened panels and by a design of the frames that takes the frame flexibility and the presence of
the floor beams into account.
FEAs, carried out on a reference configuration defined by the optimization code, are used to
acquire a deeper knowledge of the advantages and disadvantages of the analytical approach in the
design of complex structures subjected to realistic load cases. In particular, the influence of the actual
frame flexibility on the distribution of the skin shear flow induced by the frame is evaluated;
moreover, the effects on the stress distribution in skin and frames, caused by the presence of the
stringers, and of the stiffness concentration introduced by the floor beam are addressed.
Finite element method results demonstrate the effectiveness of the analytical model of the flexible
frame in evaluating the shear flow that a single loaded frame transfers to the skin and highlight the
effects of the presence of adjacent loaded frames. By means of geometrically non-linear FEAs, the
effects of the stringers on the stress distribution of a pressurized cylinder are evaluated, as well as the
magnitude and extension of the perturbation introduced by the floor beams
A three-dimensional damage model to simulate the progressive failure of composite structures
No full textA three-dimensional damage model has been
developed to simulate the progressive failure of
thin composite structures. Both intralaminar
and interlaminar damage mechanisms have
been considered and the proposed constitutive
model has been developed on the basis of
thermomechanics of the nonlinear irreversible
physical process. The intralaminar damage
modes has been analysed in the context of the
Continuum Damage Mechanics, whereas the
interlaminar damage mode has been analysed
by means of the Cohesive Zone Model. The
objectivity of the numerical discretization has
been assured using the smeared crack
formulation. The proposed damage model has
been benchmarked by means of an experimental
low-velocity impact test taken from the
Literature, reproducing the main damage
mechanisms, i.e. fibre breakage, fibre kinking,
matrix cracking, matrix crushing and
delaminations
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