Fraunhofer Institute for Mechanics of Materials IWMUser-specific routines for FE programs
Supplementary routines enable complex material behavior to be taken into account in commercial software tools.
Certain areas of application in powder technology, such as powder compaction or sintering, are not adequately covered by commercial FE packages such as Abaqus or Ansys. Are you looking for a simulation for exactly your material? To close these gaps, we offer specific routines for direct coupling with these programs. You will receive a special software file, a so-called USER routine, to extend the capabilities of your FE package. Fraunhofer IWM also offers the experimental determination of the necessary model parameters for various material classes. A standardized evaluation procedure enables the automated determination of the parameters based on just a few tests. With this addition, you can trust the results of the simulation.
Below you will find a few examples of our development. Are you missing what you are looking for? Feel free to contact us and we will build your own material model and help you develop your own simulation expertise.
Density distribution of the powder in a drill after compacting.
PressMat: Simulation of powder compaction
Commercial FE programs usually offer simplified material models for the description of powder compaction, which are generally based on the Drucker Prague Cap model. An extended version of this model was developed at Fraunhofer IWM and implemented in a USER routine for the FE program Abaqus. In particular, this extended version allows the density dependencies of radial stress ratio and strength to be taken into account. Typical output variables are the density and stress distribution during powder compaction. Compared to the standard implementation in Abaqus, the detailed development of the stresses in the green compact during unloading and ejection from the die is also taken into account. In addition, further output variables - such as the risk of damage - are available in the extension.
The grid shows the geometry of a component after the sintering process. The simulation determines the influence of the sintering process on geometry changes.
SintMat: Simulation of the sintering process
The simulation of sintering processes cannot be investigated in most FE programs, or only in a very simplified way. Fraunhofer IWM has therefore implemented several sintering models that describe the material behavior during sintering and can be used to calculate the sintering distortion resulting from density gradients, gravity and friction influences. Fraunhofer IWM has models for both solid-phase sintering and liquid-phase sintering. The models can also be used to model the sintering of multi-material systems. Typical output variables are the density development and internal stresses as well as the change in geometry due to inhomogeneous sintering shrinkage.
The figure shows how the DebindMat add-in can be used to simulate transport processes in components. The color coding corresponds to the local diffusion coefficient.
DebindMat: Simulation of transport processes
The simulation of transport processes in commercial FE programs is usually limited to just one species. Depending on the composition of the binder, several gaseous species occur during debinding, which diffuse through the porous solid structure of the green compact or flow under pressure. At the same time, the liquid binder is transported due to capillary forces. In order to simulate these processes using the FE method, a separate USER element is required that provides the necessary degrees of freedom. This allows the pore pressure and binder content to be calculated as a function of process parameters. The routine can be used for components with complex geometries, but also for the consideration of one-dimensional simplifications in the form of a plate, cylinder or sphere.
The AutoPressSint add-in enables the simulation of the pressing and sintering of components. The color coding at the top corresponds to the density distribution and the image below shows the geometry including the distortion after sintering.
AutoPressSint: Simulation of sintering distortion
Two coupled simulations are usually required to predict the sintering distortion during die pressing: a compaction simulation followed by a sintering simulation, with the key transfer variable being the green density. The manual execution of such a continuous simulation chain involves many sub-steps: creation of the finite element meshes from given geometry data, provision of the material data, specification of the punch movements up to the actual execution of the two simulations and their evaluation. At Fraunhofer IWM, this process has been automated so that, in cooperation with the customer, who, for example, provides the geometries in a defined format, a single Excel spreadsheet is sufficient to start the simulations. The simulations themselves and the evaluations then take place automatically. This automated workflow can be easily adapted to the customer's specific requirements.