| Lightweight materials such as aluminum and magnesium alloys have been considered to replace ferrous automotive components to reduce fuel consumption and hazardous emissions in transportation vehicles. Warm hydroforming technology, as an emerging hybrid process, was investigated to enable high formability, reduced process steps and part consolidation for auto body and structure parts where mass reduction opportunities exist. For successful and cost effective implementation of the warm hydroforming process, selective heating of dies and blank is necessary in addition to careful design and control of loading parameters including hydraulic pressure, blank holder force and punch speed. In this study, a novel methodology to control the process variables was developed under warm hydroforming conditions. Depending on the response characteristics on the deformation, the process variables could be controlled spatially and/or temporally. First, the temperature distribution could be determined spatially through the adaptive isothermal FEA/DOE approach. The combined adaptive isothermal FEA and DOE approach could accurately provide the basic and critical guidelines in determining the optimal temperature distribution for a given part, tooling, hydraulic medium and blank material. The developed hybrid approach could further reduce the total analysis time to predict the optimal temperature condition of the tooling regions.{09}Secondly, temporal loading profiles of hydraulic pressure, blank holder force and punch speed could be determined by the adaptive FEA with fuzzy control algorithm. The adaptive FEA with fuzzy control algorithm could predict the loading profile rapidly requiring only a single simulation with few runs for fine tuning. Finally, to broaden basic understandings and rapidly provide the process windows of warm HMD (hydromechanical deep drawing) process, a simple analytic model under warm HMD condition was developed.{09}The floating/non-floating conditions which affect the formability could be determined by a simple pressure vessel theory. A failure criterion was also developed and could predict the failure/success of the forming process. The developed methodologies, numerical tools/modules and analytic models could broaden the general understanding and use of sheet hydroforming towards achievement of lightweight parts and structures. |
