An integrated experimental and finite element approach for wrinkling limit prediction of Inconel 718 alloy at elevated temperatures

Wrinkling is generally induced because of metal instability and considered as an undesirable defect in sheet metal forming processes. Wrinkling leads to severe influence on functional requirements and aesthetic appeal of final component. Thus, the present research is mainly dedicated on the experimental and numerical analysis for wrinkling behavior prediction of Inconel 718 alloy at elevated temperature conditions. Initially, Yoshida buckling tests (YBT) have been conducted to investigate wrinkling tendencies of Inconel 718 alloy from room temperature (RT) to 600 degrees C by an interval of 200 degrees C. Subsequently, Finite Element (FE) analysis of YBT has been performed to analyze post buckling behavior. Critical strain values at onset of wrinkling are determined and strain based wrinkling limit curves (epsilon-WLCs) are plotted at different temperatures. In-plane principal strains are transferred to effective plastic strain (EPS) versus triaxiality (eta) space to differentiate the transformation between safe and wrinkling instability. Finally, complete forming behavior of alloy is represented by means of fracture, forming, and wrinkling limit curves. The gap between forming and wrinkling limit curves at elevated temperature is similar to 1.5 times higher than that at room temperature.