Welcome to AutoDesignTool
Numerical Simulation and Automatic Design of multi-step sheet metal forming processes
The 3-years project AutodesignTool, started in the 1st May 2012, is a research project founded by the by the the Portuguese Foundation for Science and Technology via project PTDC/EME-TME/118420/2010 and by FEDER via the “Programa Operacional Factores de Competitividade” of QREN with COMPETE reference: FCOMP-01-0124-FEDER-020465.
The design of forming tools can be still seen as a “trial-and-error” practice, based on previously obtained experience by engineers, mainly due to complexities inherent to plastic forming processes (large deformations, friction, springback and wrinkles in formed parts, to name a few). In industries, such as the automotive, where complex and innovative parts are constantly required at the shortest time possible, this practice can lead to large economical costs and, consequently, lost of competitiveness.
A significant improvement can be achieved in tool design by applying software tools that can realistically simulate material forming processes. Nowadays, simulation of stamping processes does not create major difficulties, i.e. geometry of products and forming defects like wrinkles or ruptures can be predicted with good accuracy. However, it is common that FEM simulation encounters problems when multi-step processes are analysed. This fact is mostly due to the repeatly springback and trimming processes. During a multi-step process simulation, and before setting the deformed part on new tools, it is necessary to remove the external load remaining from previous steps from the FEM model, initiating springback phenomena.
Other of the major problems in the design of multi-step (or progressive) tools is to know to when to divide the overall process (and the minimum number of required steps) in the multi-step processes. Today, the die maker divides the process when the formability results in failure. Moreover, the division is performed right before failure takes places. However, this procedure is inefficient and can lead to the subsequent step premature failure.
Therefore, the main goals of this project are
a) To develop numerical procedures able to simulate multi-step sheet metal forming processes and
b) To develop an automatic design tool able to predict the ideal number and shape of the multi-step progressive forming tools.
The benefits of such design tool developed within this project are: (i) overall increase in project productivity; (ii) design simulation and virtual die tryouts that would identify forming problems like splits, cracks and wrinkles; (iii) these common problems on metallic parts such as springback, wrinkling, buckling instabilities, flow localization and fracture, are intended to be avoided; (iv) improved quality and reliability to ensure accuracy of the data for “right the first time” design of the real experimental tool.
The problem of simulation of multi-step sheet forming process corresponds to the resolution of a direct problem. However, the automatic design of the forming tools corresponds to the resolution of an inverse problem in which the final shape of the stamped sheet is already known and the geometry/shape of the tool that leads to the desired result becomes the required information.
From previous works of the R&D team [PT1, PT5], it can be seen that inverse problems can be solved with the aid of an optimization methodology coupled with FEM analysis. Considering that each FEM analysis is very time consuming, the choice of the optimization method should be done wisely. A way of optimisation in combination with time-consuming function evaluations is using approximate optimisation algorithms, of which response surface methodology (RSM) can be representative.
The shape of the final tool will be found considering parameterized geometry. However, the results obtained by such methodology are always limited to the geometric possibilities offered by the variation of the parameters that define/parameterize the shape. In this project, this limitation will be overtaken by the use of a non-parameterized definition for the tool surface geometry as well.
At the end of the project, it is expected to obtain a numerical tool able to efficiently simulate multi-step analysis. It is also expected to have other numerical tool that, together with the previous tool, is capable of automatic design the progressive forming tool, including the ideal minimum number of steps and avoid forming problems.
The validation of both numerical tools will be performed considering deep-drawing experimental results achieved within the project. All mechanical properties will be monitored in these tests with the use of an advanced 3D optical metrology system. An experimental methodology for optimisation of the forming tools will be also developed. The execution of the experimental tests will be carried out in industrial partner (P.J.Ferramentas).