Numerical Simulation Of Multi-point Stretch-bending For Thin-wall Profile

Aluminum alloy profile，as a kind of common lightweight alloy material，withthe advantage of good mechanical properties and lightweight，is widely used invehicle manufacturing，Aeronautics and Astronautics framework parts production andso on. Stretch bending forming is the main forming method for aluminum alloyprofile，it can produce parts with small springback and good surface quality. But thetraditional stretch forming mould are unable to meet the flexible and digital demandbecause of its high production cost and long manufacturing cycle. Multi-pointforming scatter the traditional forming mould into a series of compactly arrangedbasic body punch. The surface shape of forming die can be changed quickly throughautomatically adjusting the height of the punch. It can be used for the forming ofdifferent geometric shapes so that we can realize the blank’s flexible forming. Themulti-point die replacing traditional whole mould，making use of multi-point forming，employ a set of equipment combined with a variety of surface products to realizemulti-point stretch bending forming. It can reduce the production cost and achieve thepurpose of digital and flexible form profile’s design to manufacturing. In this paper，the feasibility of multi-point stretch bending forming is studied，using the typicalthin-wall rectangular profiles as the research object. At the same time，the mainforming parameters’ influence to the forming quality is discussed. The main contentsare as follows:Stretch bending forming can be divided into three stages through mechanicalanalysis based on profile’s stretch bending. The deformation features are summarized.The constitutive relation of polyurethane rubber is derived. The material model offinite element for multi-point stretch bending forming is built. The different loadpath’s influence for forming quality is analyzed. We get the best location for reference point through discussing the position of chucking power. The mechanism ofproduction for springback and cross-section distortion is analyzed through contrastingmulti-point and whole mould dies’ stretch bending. The pressure’s influence forcross-section distortion is discussed. And the pre-stretching and post-stretching’sinfluence for the largest springback is studied. The result show that multi-point stretchbending forming can be used for aluminum alloy profile.In the thin-wall profile’s multi-point stretch bending forming，the bigger thepressure，the smaller the cross-section distortion. But when the pressure exceeds thesuitable value，the distortion is greater. The bigger the stretch bending radius andmaterial’s thickness，the lighter the distortion. The bigger the aspect ratio of theprofile， the smaller the pressure. With the increase of the pre-stretching、post-stretching、 the elastic cushion’s hardness and the profile’s thickness， thespringback decreases. As for the thickness of elastic cushion and stretch bendingradius，the springback works in the opposite way. The springback will almost has nochange when the pre-stretching and post-stretching reach to a certain value.As for suppress defects， the pressure and filled rubber’s influence tocross-section distortion is discussed. We found the suitable pressure for each otherthrough analyzing different section distortion rule. The most suitable elastic cushionthickness is found. And the mathematical relational expression between pre-stretching、post-stretching、forming radius、thickness and the maximum springback is derived.