Formability Enhancement in Incremental Forming for an Automotive Aluminium Alloy Using Laser Assisted Incremental Forming

摘要

The aim of this study is to establish general guidelines for minimizing the number of tests required to determine optimum process parameters in terms of formability for laser assisted single point incremental forming (LASPIF). An automotive aluminium alloy (AA5182-O) is selected and the room temperature failure angle of this material is determined experimentally. The straining behaviour as well as sheet thinning of the test part (at its maximum forming angle) is studied using an experimentally validated finite element model. From the thinning rate of the sheet metal and the shape of the contact zone between tool and sheet it is concluded that continuous straining of the sheet on the wall region of the contact area is responsible for extra thinning and failure. Based on the size and position of the contact zone, different laser tool positioning strategies have been used to achieve the highest forming angle. It is concluded that due to an elongated shape of the contact zone in steep wall angle parts and considering a small deviation of the forming robot, the selection of a large spot diameter is necessary in terms of maximum obtainable wall angle. It has been observed that the maximum forming angle is still achievable using a large forward offset. It is concluded that the partial stress-relief annealing of the deformed geometry during the approach of the forming tool, is responsible for this formability enhancement.