Stabilization process in the finite element method
Under certain circumstances, convergence problems occur during the solution process for a non linear FE-simulation. One reason can be the stability characterstics of the system under consideration. Small changes in loading can lead to big changes in deformation.
The arc length method offers a possibilty to circumvent these numerical difficulties. Alternatively, newer stabilization methods can be used, where the considered potential is modified.
- Preparation of theEuler-rodwith respect to thestability properties
- non linear calculation with imperfection
- Comparison ofdifferentmethods of solution
- Presentationof astabilizationalgorithm
- Parameter study
Friction and heat generation
Heat is generated through friction. The resulting analysis of a thermo-mechanical coupling, the calculation of the temperature and the deformation field is for both the friction partner by no means trivial. The work balance for the frictional work is known. A body in motion is slowed down. The necessary friction work is converted to heat which leads to a temperature increase in the body. With simple balance equations one can formulate a simplified heat problem. What does one need to do to make this process an actual full transient process?
- Literature search regardingsimpleproblems
- Modelingof two bodies, wherein the contactsurfaces are parallel
- Consideration of possiblesimplifications
- Whatconditions must be satisfied so thata decouplinginthe simulationis successful?
- Development procedurefor a disc brake
Fluid-structure simulation for easy flow load cases
The effects of a flow of a surrounding medium on a fixed structure are for a number of technical applications of growing importance and are accessible through the current simulation techniques and available computer facilities of a quantitative analysis.
It is already the current technology both in the automobile industry as well as in the aircraft industry. It is different for already existing hydropower plants. The interpretation of the hundred year old plants was carried out by then state of knowledge. However, improvement measures shall be maintained for parts of these plants according to the current state of technology.
Goal of this work is to calculate a simple example with the help of available softwares (ANSYS Fluent, OpenFOAM).
- Taking over the preliminary student work.
- Completion of existing examples (Analysis of parameter studies)
- Noting down elastic properties of solid body
- Choosing a suitable example
- Comparison of results from ANSYS and OpenFOAM
Prodution oriented optimization
The demands on today's designs are becoming challenging. Besides criteria like the weight, durability and the vibration behaviour, the method of manufacturing a product plays an important role. The designer must orient himself with technologists in most of the cases. With the help of modern tools like HyperWorks components can be optimized, i.e., it is already possible to force the component during the optimization in a dedicated form.
Task of the student is to show the possibilies of the program Hyperworks with the help of examples.
- Incorporation into theprogramsHyperMesh(Preprocessor)andOptiStruct(Solver &postprocessor)
- Developing simple custom or already available examples
- Application Example 1:Optimizethe lidof areactionwheel(as milling andsheet metal construction)
- Applcation Example2:Optimizationof thegeometry of ashell construction(minimizing the stressshareof the bend)
- Creatinga detailed documentation
The mechanical modeling (and therefore the numerical simulation with the finite element method) for different deformation processes is carried out by considering the phenomena to be modeled on the relevant scale range (e.g.: screw connection = modeling of thread pitch, fiber reinforced material= fiber and matrix). In technically relevant modeling, it is impossible for every screw connection to exactly reproduce a thread pitch. One manages the department of so called spare or effective parameters.
By modeling of fine structures in a representative volume element -RVE- (Meso scale), effective parameters for modeling at the level of macro scale are determined via homogenization algorithm.
- Literature search
- Creating an overview of different homogenization procedures
- example of material homogenization with the help of periodic boundary conditions, replacement parameter for a 3 layer composite of 2 different linear elastic isotropic materials
- Homogenization in regard to heat conduction
- Homogenization for a RVE with damage
- Summary of unresolved issues
Viscoelasticity: A complex material law - Chaboche
With the processing of this work, the classification of a material law and the determination of the relevant material parameters are to be rendered based on experimental data from the literature and the existing simulation software.
- Literature search
- Simulationoftensile specimensfor differentsimplematerialmodels
- Modelingofcomplexmaterial model
- Parameter study
- Applicationon a giventechnical problem