Abstract. This paper presents experimental and numerical results of butt friction stir welding of high density polyethylene. The FSW designed tool insulates the welded samples and preserves the heat gained from friction thus avoiding the appearance of blisters and splits after welding. The experimental tests, conducted according to combinations of process factors such as rotation speed, welding speed, pin diameter and hold time at beginning welding, were carried out according the Taguchi orthogonal table L 27 in randomized way. Temperatures in the joint during the welding operation and flow stresses from the tensile tests of welded samples were measured and variances were analyzed. Identified models were used to simulate, by finite elements, the tensile tests performed on specimens having a weld cordon in their active area. The results show coherence between the numerical predictions and experimental observations in different cases of weld cordon mechanical behaviour.
A generic procedure for robust design in developing products and processes, which is referred to as RDPP-SF has been proposed. The method uses the stochastic frontier model to encompass both stochastic noise (e.g. manufacturing unit-to-unit variation, and measurement errors) and special-cause variation (e.g. environment, customer use, wearing, and deterioration noises). Even then, the RDPP-SF method has fallen short of tackling robust design of multi-objective problems, and its applicability is restrained to the performance characteristics of magnitude type (i.e., “the larger is the better” or “the smaller is the better”). Aiming at these limitations, the article seeks to address the robust design of the multi-objective problems using the RDPP-SF method. This is performed by reassessing the procedural scheme of the RDPP-SF method and the statistical significance of the hypothesis test (H0: γ = 0 vs H1: γ > 0) at 5% level. Depending on the statistical significance of the test (H0: γ = 0 vs H1: γ > 0), the arrays of the extrinsic and/or the intrinsic noise insensitivity scores are assigned to the grey relational analysis matrix as performance measures. The most robust design solution for the multi-objective problem is then obtained by sorting the overall grey relational grades. The amended RDPP-SF method is finally demonstrated using three industrial multi-objective case studies.
Dans cetteétude, on présente une contributionà la modélisation expérimentale et numérique du comportementélastoplastique endommageable anisotrope de tôles destinéesà la mise en forme. L'accent est mis sur la localisation des instabilités plastiques induites par l'anisotropie plastique et l'endommagement. La procédure d'identification des paramètres matériau du modèle de comportement est basée sur une approche inverse d'optimisation s'appuyant sur des essais de traction orientés, associéeà des simulations numériques (Abaqus/Standard et Matlab). La validation de la procédure proposée a puêtre menée grâcè a une confrontation entre simulations numériques et résultats expérimentaux obtenus sur deséprouvettes caractéristiques des tôles minces texturées en acier doux. L'application est ensuite faiteà la simulation de procédés de gonflement hydraulique de ces tôles avec prévision de l'endommagement ductile. Plusieurs cas en expansion libre (matrices circulaires et elliptiques) et en expansion dans des cavités de matrice seront présentés et des comparaisons avec les résultats expérimentaux seront réalisées.
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