multiobjective optimization of an agile machining type linear delta structure

The innovative architectures design of agile machines dedicated to the machining at high speed requires the implementation of analytical and numerical models for the optimization of the kinematic, static and dynamic behavior of the machine, taking into account the elastic deformations and their compensation at level of machine control. In the context of multi-objective optimization, the first part is to identify the parameters and variables inherent to each constituent element of a DELTA robot type machine, the purpose is to optimize the essential elements of its structure. This requires a formulation of the multi-objective problem by expressing the objective functions, the constraints and the corresponding search spaces, as well as the resolution of the problem by the use of high-performance mathematical methods and tools (genetic algorithms, etc.)

Résolution des problèmes de distorsion en grande déformation dans les procédés de mise en forme des matériaux basée sur la méthode EFG

cette contribution présente une mise en oeuvre de la simulation numérique en 3D d'une opération de poinçonnage d'un disque métallique, en utilisant la méthode ''Element free Galerkin'' sous l'environnement fluent et LsDyna. Les résultats obtenus sont comparés avec ceux réalisés par la MEF, pour mettre en évidence sa capacité de traiter les problèmes de distorsion du maillage en grande transformation

Optimisation robuste de la qualité de surface usinée et de la productivité sous la limitation des vibrations

Dans cette contribution, nous présentons une optimisation robuste des paramètres de coupe, avec la prise en compte des incertitudes inhérentes à l'usure et à la déflexion de l'outil pour une opération de chariotage d'un acier 100C6. Dans une première étape, nous procédons à la construction des modèles de substitution qui relient les paramètres de coupe aux variables d'intérêt basée sur l'utilisation de plan d'expériences. Nos deux objectifs sont le meilleur état de surface et le maximum de productivité sous limitations liées aux vibrations et aux niveaux des trois paramètres de coupe. Ensuite, à l'aide de l'algorithme génétique développé et basé sur un mécanisme d'évaluation robuste de chromosomes par les simulations de Monte-Carlo, l'influence et l'intérêt de l'intégration des incertitudes dans l'optimisation en usinage sont mis en évidence. Après comparaison des fronts de Pareto classique et robuste, des qualités de surfaces moins efficaces mais robustes peut être obtenue avec la prise en compte des facteurs incontrôlables ou des incertitudes contrairement à ce que prévoit l'optimisation déterministe et classique pour les mêmes valeurs de la productivit

Conception de montage d’usinage : placement des éléments technologiques en contact avec la pièce

Le choix des éléments technologiques constituant le montage d’usinage et tout particulièrement les éléments en contact avec la pièce joue un rôle primordial dans la qualité de la pièce usinée. L’objectif de ce papier est d’une part de définir une méthodologie de choix des éléments technologiques en contact avec la pièce et d’autre part de proposer une stratégie de placement

multiobjective optimization of an agile machining type linear delta structure

The innovative architectures design of agile machines dedicated to the machining at high speed requires the implementation of analytical and numerical models for the optimization of the kinematic, static and dynamic behavior of the machine, taking into account the elastic deformations and their compensation at level of machine control. In the context of multi-objective optimization, the first part is to identify the parameters and variables inherent to each constituent element of a DELTA robot type machine, the purpose is to optimize the essential elements of its structure. This requires a formulation of the multi-objective problem by expressing the objective functions, the constraints and the corresponding search spaces, as well as the resolution of the problem by the use of high-performance mathematical methods and tools (genetic algorithms, etc.)

A smoothed radial point interpolation method (S-RPIM) for large-deformation elasto-visco-plastic analysis occurring in sheet metal blanking processes

In this paper, a meshfree cell-based smoothed radial point interpolation method (CS-RPIM) is extended to large-deformation elasto-visco-plasticity analysis for simulation of high speed sheet metal blanking processes. For this purpose, two techniques included in large-deformation analysis formulation are employed: a Johnson?Cook flow stress model and an updated Lagrangian scheme to integrate the constitutive relations. The volumetric locking due to the nearly incompressible behavior of elastic-visco-plastic deformations is remedied by relaxing the volumetric strain through the mean value computed by the strain smoothing approach coupled with the meshfree radial point interpolation method (RPIM) (based on the radial basis functions interpolation). The next step concern the description of ductile fracture initiation and propagation, which is essential to predict final product shapes in the blanking process. A hybrid approach is elaborated combining a damage model, based on a failure criterion for the brittle mode initiation; assumed to initiate when the maximum tensile principal stress at a node reaches a critical value, and a stress intensity factor model, to handle the crack propagation calculations once the crack opening is already created. The proposed algorithm duplicates cutting nodes that meet specific conditions and avoid the global remeshing procedure. Validity of the CS-RPIM for large-deformation metal forming problem is proved by benchmarks, and numerical example of sheet metal blanking process. Obtained results demonstrates that, the proposed method possess superior accuracy and convergence properties for strain energy solutions comparing to the standard FEM, the combination of the strain smoothing approach with the powerfull RPIM technique can easily simulate problems with severe element distortion, and solve volumetric locking problem in large-deformation analysis

Numerical study for single and multiple damage detection and localization in beam-like structures using BAT algorithm

This paper presents a new damage detection and localization technique based on the changes in vibration parameters using BAT and Particle Swarm Optimization algorithm. The finite element method is used to apply damage at specific element(s) of the considered beams. The damage is represented by a reduction in Young’s modulus and the identification of damage is formulated as an optimization problem using objective function based on Modal Scale Factor and changes in natural frequencies. A procedure for detecting and locating damage of beam-like structures based on BAT algorithm is used. This approach presents a method that can be used to detect the single and multiple-damage positions and the rate of damage in structural elements with high accuracy after the first iteration. The results obtained using BAT algorithm are compared to those obtained using Particle Swarm Optimization Algorithm. By taking noise into account in the damage detection and localization problem, it is shown that our approach based on BAT algorithm can detect the damage locations with high accuracy

Numerical study for single and multiple damage detection and localization in beam-like structures using BAT algorithm

This paper presents a new damage detection and localization technique based on the changes in vibration parameters using BAT and Particle Swarm Optimization algorithm. The finite element method is used to apply damage at specific element(s) of the considered beams. The damage is represented by a reduction in Young's modulus and the identification of damage is formulated as an optimization problem using objective function based on Modal Scale Factor and changes in natural frequencies. A procedure for detecting and locating damage of beam-like structures based on BAT algorithm is used. This approach presents a method that can be used to detect the single and multiple-damage positions and the rate of damage in structural elements with high accuracy after the first iteration. The results obtained using BAT algorithm are compared to those obtained using Particle Swarm Optimization Algorithm. By taking noise into account in the damage detection and localization problem, it is shown that our approach based on BAT algorithm can detect the damage locations with high accuracy

Sensitivity analysis of the GTN damage parameters at different temperature for dynamic fracture propagation in X70 pipeline steel using neural network

In this paper, the initial and maximum load was studied using the Finite Element Modeling (FEM) analysis during impact testing (CVN) of pipeline X70 steel. The Gurson-Tvergaard-Needleman (GTN) constitutive model has been used to simulate the growth of voids during deformation of pipeline steel at different temperatures. FEM simulations results used to study the sensitivity of the initial and maximum load with GTN parameters values proposed and the variation of temperatures. Finally, the applied artificial neural network (ANN) is used to predict the initial and maximum load for a given set of damage parameters X70 steel at different temperatures, based on the results obtained, the neural network is able to provide a satisfactory approximation of the load initiation and load maximum in impact testing of X70 Steel.           &nbsp

On the Factors Affecting the Accuracy and Robustness of Smoothed-Radial Point Interpolation Method

In order to overcome the possible singularity associated with the Point Interpolation Method (PIM), the Radial Point Interpolation Method (RPIM) was proposed by G. R. Liu. Radial basis functions (RBF) was used in RPIM as basis functions for interpolation. All these radial basis functions include shape parameters. The choice of these shape parameters has been and stays a problematic theme in RBF approximation and interpolation theory. The object of this study is to contribute to the analysis of how these shape parameters affect the accuracy of the radial PIM. The RPIM is studied based on the global Galerkin weak form performed using two integration technics: classical Gaussian integration and the strain smoothing integration scheme. The numerical performance of this method is tested on their behavior on curve fitting, and on three elastic mechanical problems with regular or irregular nodes distributions. A range of recommended shape parameters is obtained from the analysis of different error indexes and also the condition number of the matrix system. All resulting RPIM methods perform very well in term of numerical computation. The Smoothed Radial Point Interpolation Method (SRPIM) shows a higher accuracy, especially in a situation of distorted node scheme