Investigation into thinning and spring back of multilayer metal forming using hydro-mechanical deep drawing (HMDD) for lightweight parts

Lightweight, hybrid parts are extensively used in the manufacturing of modern aerospace or automobile structures like fiber metal laminates (FMLs) to replace the monolithic metallic parts. Presently, smaller and complex-shaped FML parts are made by applying the stamp-forming techniques. However, due to limited strain of the composite fibers, such techniques are unfit for forming complex profile laminated parts. This study focuses on the use of hydro-mechanical deep drawing (HMDD) for the three layers simultaneous forming of the metallic blanks to fabricate a hemispherical structure which will then be used to make a FML part. Orthogonal test strategy is formulated to investigate the influence of variables such as cavity/pre-bulging pressures, pre-bulging height, and die-binder gap to optimize the forming conditions. FE-based experimental study is done to research the thickness distribution and spring back of the formed multilayer structure. Results show that the research is sufficient in predicting these attributes and can provide a basis to understand the fundamental phenomenon for three-layered, simultaneously formed structures. Hybrid parts fabricated by using multilayer forming can expand the application areas of FMLs.