Predictive simulation of friction welding
The focus is the numerical simulation of manufacturing processes, especially rotary friction welding by a holistic approach for engineering mechanics, numerics, thermodynamics, tribology and material science. Highlights of the simulation include the dynamic re-meshing and the friction law, which is coupled to the flow properties of the material.
Analysis, Design and Optimization of rotary friction welding
The simulation allows the testing of new technologies or the optimization of existing processes. Using a calibrated simulation model, cost-intensive friction welding tests (e.g. with large part diameters or complex joint geometries) can be saved.
|Part design/idea||Contour plot of the calculated temperature field||Comparison of the experimental
results to the FE-mesh
Application fields of the simulation are the understanding of the process, the development of new weld geometries and processes, the optimization of process parameters, the simulative FMEA and more.
Residual stress formation taking microstructural changes into account
In most cases, residual stresses and distortions are unwanted side effects of welding and forming processes. The simulation helps both to estimate and to understand their formation. Compared to the experimental determination, the stress distribution in the whole structure is available and the history of arbitrary points can be tracked. A key factor in the simulation are material property changes. Phase transformations of steels are highly dependent on the cooling speed and influence the flow properties. A comparison to experimental data from literature already shows agreement between predicted and measured residual stresses. Additionally, the chair of technical dynamics is capable of the strain gauge based measurement of residual stresses. Contact
|Radial, axial and hoop residual stress (left to right) in ring elements in the experiment (top) and the simulation (bottom)
(Source: Grant et al. Finite element process modelling of inertia friction welding advanced nickel-based superalloy.
Materials Science & Engineering: A, 513-514:366-375, 2009.)
Numerical simulation of the bond formation mechanism in pressure welding
Aim of the research is the development, testing and implementation of a methodology to simulate the bond formation in pressure welding. With this model it will be possible to predict the weld strength in pressure welding as a function of process, material and geometry parameters. Contact
Influence of the rotary speed on the shortening rate in rotary friction welding
A challenge for simulating manufacturing processes is the inclusion of various effects depending on the rotary speed in the friction law. A promising approach is the modification of the current friction law by including a slip velocity variable. Contact
Experimental identification of thermo-mechanical material properties
The precise model parameter identification is necessary for realistic simulation results. In cooperation with the chair of materials and joining (homepage) a routing for hot deformation material parameter acquisition has been developed, which allows for the efficient material investigations. For the tests a Gleeble 3500 testing machine is available, which is used to reproduce the thermo-mechanical history of rotary friction welding and to measure the flow property changes. Heat conductivity and specific heat capacity can be determined as well using Hot Disk, laser flash and differential scanning calorimetry.
|Isotherms of the material law of S355 structural steel|
Performance of rotary friction welding tests
Additionally, due to the close cooperation with the University of Applied Science Magdeburg-Stendal (homepage), it is possible to produce rotary friction welds and to evaluate and interpret the results.