Student Projects and Theses

Principle stress directions vary in time under multiaxial loads. In brittle matrials (e. g. adhesives in wind turbine rotor blades or cast iron in rotor hubs), this results in fatigue damage that is not evenly distributed among material planes, but is concentrated around a single plane, which is called the critical plane.

In fatigue life calculations of such materials, the damage on the critical plane is governing, and not the accumulation of damage on all material planes, as would be the case for ductile materials. The identification of the critical plane is thus of utmost importance. However, that is linked with very high computational cost. In order to reduce the computation times, different optimisation algorithms have to be tested in the context of this Bachelor's Thesis.

Prior knowledge on fatigue life analysis is not necessarily required. Further details are given in the offer (in German only).

• Prior experience in Matlab is required.

For uni-axial fatigue analyses, rainflow counting is a standard method for the counting of cycles. It yields reliable results at low computational cost. For multi-axial loads, the traditional rainflow counting schemes do only offer meaningful information on the identified cycles, if the principle stress directions are approximately constant over time. In that case, we speak of proportional loads.

For non-proportional loads, traditional rainflow counting algorithms can yield severe inaccuracies in fatigue life estimations. In this case, multi-axial rainflow count algorithms are required in order to improve the prediction accuracy. In this work, different variants of multi-axial rainflow counting are to be compared in the framework of benchmark examples.

Prior knowledge on fatigue life analysis is not necessarily required. Further details are given in the offer (in German only).

• Prior experience in Matlab is required.

Principle stress directions vary in time under multiaxial loads. In brittle matrials (e. g. adhesives in wind turbine rotor blades or cast iron in rotor hubs), this results in fatigue damage that is not evenly distributed among material planes, but is concentrated around a single plane, which is called the critical plane.

In fatigue life calculations of such materials, the damage on the critical plane is governing, and not the accumulation of damage on all material planes, as would be the case for ductile materials. The identification of the critical plane is thus of utmost importance. However, that is linked with very high computational cost. In order to reduce the computation times, different optimisation algorithms have to be tested in the context of this work.

Prior knowledge on fatigue life analysis is not necessarily required. Further details are given in the offer (in German only).

• Prior experience in Matlab is required.

Buckling is a mechanism of stability failure in thin-walled structures which are exposed to compressive stresses. Buckling is a bifurcation problem, where large displacements perpendicular to the structure plane occur instantaneously. This phenomenon reduces the structural integrity of the respective structures dramatically, hence it is understood as failure. Since the growth in size of rotor blades is an ongoing trend, increasingly large structural parts are loaded by increasing loads. Consequently, the risk of buckling increases as well.

In the framework of this work, selected rotor blades in the multi-MW class have to be analysed with respect to their buckling resistance. For this purpose, 3D finite element analyses have to be carried out, including linear and nonlinear buckling analyses. If the task is conducted as a Master's Thesis, additional subtasks have to be investigated.

Further details are given in the offer.

• Ideal candidates have some basic experience in finite element application.

For uni-axial fatigue analyses, rainflow counting is a standard method for the counting of cycles. It yields reliable results at low computational cost. For multi-axial loads, the traditional rainflow counting schemes do only offer meaningful information on the identified cycles, if the principle stress directions are approximately constant over time. In that case, we speak of proportional loads.

For non-proportional loads, traditional rainflow counting algorithms can yield severe inaccuracies in fatigue life estimations. In this case, multi-axial rainflow count algorithms are required in order to improve the prediction accuracy. In this work, different variants of multi-axial rainflow counting are to be compared in the framework of benchmark examples.

Prior knowledge on fatigue life analysis is not necessarily required. Further details are given in the offer (in German only).

• Prior experience in Matlab is required.