Determination of proper temperature distribution for warm forming of aluminum sheet materials

In warm forming of aluminum sheet materials, determination, realization, and maintenance of optimal temperature gradient is a key process parameter for increased formability. In this study, a two-phase procedure for efficient and accurate determination of proper temperature condition for warm forming of aluminum sheet metal blanks is presented using a hybrid 3D isothermal/non- isothermal finite element analysis (FEA) and design of experiments (DOE) approach. First, the relative trend, priority and overall temperature ranges of aluminum sheet metal blank regions are obtained using isothermal FE modeling and DOE techniques to reduce the analysis time significantly. In this phase, different temperature levels were assigned onto different regions of the deforming blank material (i.e., holding region, corner region, etc.). Heat transfer with the tooling and environment during the deformation process is ignored in order to achieve rapid predictions. Second, few additional non-isothermal FEAs, taking heat transfer into account, are conducted to validate and to refine the warm forming conditions based on the results from the isothermal FEA/DOE analysis. The proposed hybrid methodology offers rapid and relatively accurate design of warm forming process, especially for large parts that require 3D FE analysis. In addition, effects of forming speed (v), friction (μ), and blank holder pressure on formability are investigated. Increasing part formability is observed with decreasing punch speed and blank holder pressure while an optimal process window is found in case of varying friction coefficients.