447 research outputs found
Damage assessment of large space structures through the variational approach
No full textThe present investigation is focused on the solution of a dynamic inverse problem which is concerned with the assessment of damage in large space structures by means of measured vibration data. This inverse problem has been presented as an optimization problem and has been solved through the use of the Conjugate Gradient method with the Adjoint Equation also called Variational Approach. When a high number of damage elements is to be individualized and these elements are also severely damaged, it is shown that the use of an additional method is necessary in order to provide a better initial guess for the conjugate gradient method. A stochastic method, represented by the Genetic Algorithm Method, has been chosen because it provides robust search in complex spaces and also reduces the chance of converging to local optima. The application of this hybrid approach showed that better results can be achieved, although the computational time for the application here analyzed could increase. The damage estimation has been evaluated using noiseless and noisy synthetic experimental data, and the reported results are concerned with a space truss structure
Some Results on Damage Detection Using Variational Approach
No full textThe present investigation is focused on the solution
of a dynamic inverse problem which is concerned
with the assessment of damage in structures
by means of measured vibration data. This inverse
problem has been presented as an optimization
problem which has been solved through the
use of a hybrid approach where the conjugate gradient
method (CGM) with the adjoint equation, also
called variational method, is employed coupled with
the Genetic Algorithm (GA) method. Moreover, a
general formulation for the application of the variational
method is presented which allows the use of
any kind of experimental data. The solution for the
damage estimation problem has been obtained using
synthetic experimental data, and the reported
results are concerned with space truss structures
modeled through the finite element technique
Optimization of an Aeronautical Composite Structure through a Parallel Multilevel Approach,
No full text. Optimal design of complex engineering systems, such as aircraft composite
structures, can often be accomplished only by decomposition techniques. In general, it is
characterized by a multidisciplinary task, usually involving multiple objectives, with many
design variables and several constraints associated to each one of the disciplines taken
into account. One of these techniques is represented by the multilevel approach, where
the complex problem of multidisciplinary optimization is solved based on the idea \divide
and conquer". The original problem is split into several smaller subproblems, making the
new conguration inherently suited to parallel and distributed computing. In this paper the
optimal design of a composite wing-box is addressed by using a parallel two-level scheme,
where a stochastic method is used to solve each second-level problem. At this level, since
the changes in the components of one of the sub-problems have no in°uence on the solution
of the thers, they can be solved simultaneously
A comparison of two different approaches for the damage identification problem
No full textAbstract. This work deals with a structural damage detection problem using displacement
measurements as experimental data to be used by two different methodologies: the conjugate
gradient method with the adjoint equation and an artificial neural network. Both techniques
have been employed in order to place and quantify the time-variable damage in a simple truss
structure. Numerical experiments have been carried out with synthetic experimental data
considering a noise level of 1%. Good recoveries have been achieved with both methodologies
and estimation errors have been reported in order to make their comparison possible
A HYBRID TWO-LEVEL APPROACH USED IN THE OPTIMIZATIONAN OF AN AERONAUTICAL COMPOSITE STRUCTURE
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