Francisco Zárate

New assumed strain triangles for non linear shell analysis

A comparison between new and existing triangular finite elements based on the shell theory proposed by Juan Carlos Simo and co-workers is presented. Particular emphasis is put on the description of new triangles which show a promising behaviour for linear and non linear shell analysis.

Robust design optimization in aeronautics using stochastic analysis and evolutionary algorithms

Uncertainties are a daily issue to deal with in aerospace engineering and applications. Robust optimization methods commonly use a random generation of the inputs and take advantage of multi-point criteria to look for robust solutions accounting with uncertainty definition. From the computational point of view, the application to coupled problems, like computational fluid dynamics (CFD) or fluid–structure interaction (FSI), can be extremely expensive. This study presents a coupling between stochastic analysis techniques and evolutionary optimization algorithms for the definition of a stochastic robust optimization procedure. At first, a stochastic procedure is proposed to be applied into optimization problems. The proposed method has been applied to both CFD and FSI problems for the reduction of drag and flutter, respectively.

Reliability estimation of the sheet stamping process using support vector machines

An important concern in sheet stamping is the risk of obtaining brittle final products that can be affected by fracture. Monte Carlo simulations presented herein show that this is governed by two main factors, namely static and dynamic friction coefficients. Whereas the latter correlates in a non-linear manner with minimum and maximum end thickness, the relationship of these design parameters to the former exhibits a bifurcation that is typical of highly non-linear phenomena, in which there is a sensitivity to small perturbations of the input values (chaos). In order to estimate the reliability of the process (i.e., the probability of obtaining brittle products due to low minimum and maximum thicknesses) with a reduced number of Monte Carlo runs, it is proposed to assimilate the problem to a pattern recognition task, due to the existence of two classes, namely robust and brittle. Among many pattern recognition algorithms that are useful to this end, use is made of support vector machines, as this incorporates the powerful tool of class margins that allow a drastic reduction of the number of simulations.

Advances in the DEM and Coupled DEM and FEM Techniques in Non Linear Solid Mechanics

In this chapter we present recent advances on the Discrete Element Method (DEM) and on the coupling of the DEM with the Finite Element Method (FEM) for solving a variety of problems in non linear solid mechanics involving damage, plasticity and multifracture situations.

Applying Multi-objective Robust Design Optimization Procedure to the Route Planning of a Commercial Aircraft

Aircraft emission targets worldwide and their climatic effects have put pressure in government agencies, aircraft manufacturers and airlines to reduce water vapour, carbon dioxide (\(CO_{2}\)) and oxides of nitrogen (\(NO_{x}\)) resulting from aircraft emissions. The difficulty of reducing emissions including water vapor, carbon dioxide (\(CO_{2}\)) and oxides of nitrogen (\(NO_{x}\)) is mainly due to the fact that a commercial aircraft is usually designed for a particular optimal cruise altitude but may be requested or required to operate and deviate at different altitudes and speeds to archive a desired or commanded flight plan, resulting in increased emissions. This is a multi- disciplinary problem with multiple trade-offs such as optimizing engine efficiency, minimizing fuel burnt and emissions while maintaining prescribed aircraft trajectories, altitude profiles and air safety. There are possible attempts to solve such problems by designing new wing/aircraft shape, new efficient engine, ATM technology, or modifying the aircraft flight plan. Based on the rough data provided by an air carrier company, who was willing to assess the methodology, this paper will present the coupling of an advanced optimization technique with mathematical models and algorithms for aircraft emission, and fuel burnt reduction through flight plan optimization. Two different approaches are presented; the first one describes a deterministic optimization of the flight plan and altitude profile in order to reduce the fuel consumption while reducing time and distance. The second approach presents the robust design optimization of the previous case considering uncertainties on several parameters. Numerical results will show that the methods are able to capture a set of useful trade-offs solutions between aircraft range and fuel consumption, as well as fuel consumption and flight time.

Enhanced rotation‐free basic shell triangle for sheet stamping problems

An enhanced version of the rotation‐free three node triangular BST shell element for sheet stamping analysis is presented. The original BST element is based on an assumed constant curvature field expressed in terms of the nodal deflections of a patch of four elements and a constant membrane field. An enhanced element is obtained by using a quadratic interpolation of the geometry in terms of the six patch nodes. This allows to compute a linear membrane strain field which improves the in‐plane behaviour. An economic version of the element using a single integration point is presented. The efficiency of the new rotation‐free shell triangle is demonstrated in the analysis of sheet stamping problems.

STAMPAR: A Parallel Processing Approach for the Explicit Dynamic Analysis of Sheet Stamping Problems

Industrial sheet stamping problems generally require enormous amounts of computer resource for their solution within an acceptable time. Explicit dynamic algorithms are commonly used for these analyses since they reduce the memory requirements but they still require large CPU times and parallel processing offCapitan the only realistic alternative. This paper describes the parallel program Stampar used for the solution of industrial sheet stamping problems. The methodologies used for the parallelisation are described as well as an example with timings that show the advantage of this approach.