Papers by Author: Aldo Attanasio

Abstract: This paper reports the results obtained during a research project funded by the Italian Government and involving several Italian Universities (PRIN INTEMA). The activities have been focused on side impact bar manufacturing by means of Tube Hydroforming process (THF). Punch movement paths and fluid pressure curve were optimized by means of FEM software (LS-DYNA) to guarantee tube sealing and material feeding during the tube deformation. The side impact bar geometry was optimized till reaching the shape guaranteeing the obtainment of safe parts with the best compromise in terms of final part geometry and thickness reduction. Different fluid pressure and punch movement paths were investigated. Once accomplished all the simulations and identified the best working solution, experimental tests were performed setting the process parameters according to the values defined during the simulation phase. Good agreement between FEM and experimental results were highlighted.

Abstract: In cutting field, residual stress distribution analysis on the workpiece is a very interesting topic. Indeed, the residual stress distribution affects fatigue life, corrosion resistance and other functional aspects of the workpiece. Recent studies showed that the development of residual stresses is influenced by the cutting parameters, tool geometry and workpiece material. For reducing the costs of experimental tests and residual stress measurement, analytical and numerical models have been developed. The aim of these models is the possibility of forecasting the residual stress distribution into the workpiece as a function of the selected process parameters. In this work the residual stress distributions obtained simulating cutting operations using a 3D FEM software and the corresponding simulation procedure are reported. In particular, orthogonal cutting operations of AISI 1045 and AISI 316L steels were performed. The FEM results were compared with the experimental residual stress distribution in order to validate the model effectiveness.

Abstract: This paper deals with Incremental Sheet Forming (ISF) a sheet metal forming process that knew a wide development in the last years. A lot of experimental and simulative researches have been conducted in this field with different aims: to study the sheet formability and part feasibility; to define models able to forecast the final sheet thickness; to understand how the sheet deforms and how formability limits can be defined. Another very important issue is related with the tool path optimization. In fact, the process is characterized by high springback which causes dimensional defects. When IF is performed by a robot, the capabilities of the technology is improved in terms of obtainable shapes (it is possible to use the 6 degrees of freedom of the robot), but the shape errors seem to be higher due to the lower robot stiffness in comparison with CNC machine. In this work the comparison between two different ISF configurations, tool mounted on a CNC machine or tool mounted on a robot, is reported. A suitable geometry was investigated working different sheet material types and sheet thicknesses. The results in terms of geometrical accuracy and sheet deformation have been analyzed in order to define advantages and disadvantages of these two techniques. An analysis on the process forces has been carried out too.