D. A. Oliveira

The Effect of Tool–Sheet Interaction on Damage Evolution in Electromagnetic Forming of Aluminum Alloy Sheet

A study of the effect of tool-sheet interaction on damage evolution in electromagnetic forming is presented. Free form and conical die experiments were carried out on 1 mm AA5754 sheet. Safe strains beyond the conventional forming limit diagram (FLD) were observed in a narrow, region in the free form experiments, and over a significant region of the part in the conical die experiments. A parametric numerical study was undertaken, that showed that tool-sheet interaction had a significant effect on damage evolution. Metallographic analysis was carried out to quantify damage in the parts and to confirm the numerical results.

EFFECT OF LUBRICANT IN MANDREL-ROTARY DRAW TUBE BENDING OF STEEL AND ALUMINUM

Abstract Mandrel-rotary draw tube bending experiments examining the effect of lubricant selection were performed using a fully instrumented Eagle EPT-75 bender. Process load and displacement data were recorded and provided significant information regarding the interaction between the various parameters affecting the bending of tubes. These data allow the direct assessment of lubrication in minimizing frictional losses during bending and the overall degree of repeatability. Experiments were performed on 76.2 mm OD, seam-welded DQAK galvanneal steel and AlMg3.5Mn aluminum alloy tubes of 1.6 and 2.0 mm nominal thickness, respectively. Tubes were bent to roughly 90 degrees after springback and the ratio of the nominal centre line bend radius to the tube outer diameter was 2.5. The aim of the study was to better understand the effect of various lubricants on the process variables, thickness and surface finish of bent steel and aluminum tubes. On a effectué des expériences de cintrage par enroulement-tension sur mandrin avec une machine à plier Eagle EPT-75 entièrement instrumentée, examinant l’effet de la sélection du lubrifiant. On a enregistré les données de charge et de déplacement de l’opération, fournissant ainsi une information importante sur l’interaction entre les divers paramètres qui affectent le cintrage des tubes. Ces données permettent une évaluation directe de l’effet de la lubrification sur la minimisation des pertes par friction lors du cintrage et permettent aussi un degré global de répétabilité. On a effectué les expériences sur des tubes soudés DQAK de 76.2 mm de diamètre extérieur en acier recuit par galvanisation et en alliage d’aluminium AlMg3.5Mn de 1.6 mm et 2.0 mm d’épaisseur nominale, respectivement. On a plié les tubes à environ 90 degrés après le retour élastique et le rapport du rayon nominal de pliure de la ligne centrale au diamètre extérieur du tube était de 2.5. Le but de cette étude était de mieux comprendre l’effet de différents lubrifiants sur les variables d’opération ainsi que sur l’épaisseur et la qualité de la surface de tubes pliés en acier et en aluminium.

Effect of Bending Variables on the Characteristics of EN-AW5018 Tubes for Subsequent Hydroforming

Abstract Understanding the effects of forming history on the subsequent hydroformability of aluminum alloy tubes is critical for widespread acceptance of aluminum as a light-weight alternative in automotive components. The aim of this research is to investigate the influence of pre-bending on the characteristics of aluminum alloy tubes for the hydroforming process. Tube bending experiments were performed on 2 and 3.5 mm wall thicknesses with 76.2 mm outer diameter EN-AW5018 tube. In the tube bending experiments, key process parameters such as boost were varied and the effect on the resultant thinning, strains and springback of the as-bent tubes was assessed. Bending boost is shown to reduce thinning and strains in the as-bent tubes which has been found to be favourable for any subsequent hydroforming operation.

Severity of the Bend and Its Effect on the Subsequent Hydroforming Process for Aluminum Alloy Tube

The interaction between pre‐bending and subsequent hydroforming of AlMg3.5Mn aluminum tubes is examined in this paper. Pre‐bending induces large strains and strain gradients in the tube, which reduce the available formability for the subsequent hydroforming process. Corner fill hydroforming operations were performed on straight tubes (R/D=∞) and pre‐bent tubes with R/D=2.5, representing a transition from low severity to moderate severity bending conditions. An Eagle EPT‐75 instrumented mandrel‐rotary draw tube bender was used for the pre‐bending stage, which records all process parameters. The experiments were modeled using an explicit dynamic finite element code, LS‐DYNA. An in‐house Gurson‐Tvergaard‐Needleman (GTN) constitutive softening model, incorporated within LS‐DYNA, has been considered to predict damage and formability. Based on these results, the formability of a tube bent at an R/D=2.0 is predicted as a higher severity bend condition.

S-Rail Sled Testing With Deceleration Sled

This paper considers the effects of rotary draw bending on structural crashworthiness. We impacted tested aluminum alloy tubes in s-rail bending, using either 2.0 mm or 3.5 mm thickness, and bend radius of either 152.4 mm or 191 mm. This report documents and summarizes the test setup using the GM R&D Deceleration Sled to achieve this, with emphasis on later correlation with numerical simulation. Theoretical and numerical analyses were used to help with design setup. Forces and moments found in the tests were very consistent, suggesting good test setup design. We also found that using the longest tube section at the constrained end prevents inboard rotation and contact between the two s-rails.© 2005 ASME

S-Rail Sled Testing of Rotary Draw Bent and Hydroformed Aluminum Tubes

This report provides detailed test results for the aluminum S-rail form & crash project. We considered the effect of rotary draw bending, and rotary draw bending plus hydroforming, and their effect on mean crush force, maximum crush force, and maximum bending moment for aluminum s-rails. The use of our sled test setup resulted in accurate, repeatable test results with no end plate welding. The R/D (center bend radius/tube diameter) used were 1.5, 2.0, and 2.5. Tubes were hydroformed from the circular shape into a square tube with rounded corners. Annealed tubes were used to isolate the forming effects to thickness changes alone.