Superplastic forming
Superplastic forming (SPF) is a metal forming process that takes advantage of the high extendibility of certain materials in order to form components whose shapes might be otherwise very difficult to obtain.
In a SPF process, a thin plate is hot formed in a die by means of gas pressure. The evolution of pressures must be closely controlled during the process since the alloys of interest only exhibits superplastic behaviour for certain temperature dependent range of strain rates.
Applications
The process is increasingly being applied in the aerospace industry as a way of manufacturing very complex geometries at a fraction of the cost of conventional machining, but some practical problems are still of concern, the main ones being:
predicting the final thickness distribution of the formed parts
determining the optimum pressure cycles
specifying the overall forming times
The process is increasingly being applied in the aerospace industry as a way of manufacturing very complex geometries at a fraction of the cost of conventional machining, but some practical problems are still of concern, the main ones being:
predicting the final thickness distribution of the formed parts
determining the optimum pressure cycles
specifying the overall forming times
Instead of carrying out an extensive experimental program of tests, the superplastic forming process can be optimised with the application of numerical simulation techniques, resulting in a reduction of the time and costs needed to design a specific forming process. Due to the highly non-linear aspects inherent with the superplastic forming processes, expertise in advanced numerical analysis is unavoidably required
The Project
In the development of the fabrication process for the slats of the Dornier 728 aircraft, a numerical simulation of the superplastic forming of the pockets of the slat was carried out by IDOM for Construcciones Aeronauticas, S.A. (CASA).
The main concern was whether the thickness distribution over the formed pockets would lie within acceptable limits. There was also a lot of interest in knowing the optimum pressure cycle and the overall forming time. The first geometry analysed turned out to be inappropriate according to CASA´s design requirements for the pocket and the forming process of a second alternative had to be simulated.
The whole interactive process was over in two weeks time, with the subsequent reduction of time, costs and uncertainties regarding deadlines.
The whole interactive process was over in two weeks time, with the subsequent reduction of time, costs and uncertainties regarding deadlines.