The dry lubricated bump-type foil air bearing enables a carrying load capacity due to a pressure build up in a convergent air film. Since the air bearing provides low power dissipation above the lift-off speed and the flexible foil provides an adaptivity against high temperatures, manufacturing errors or rotor growth, the bump-type foil air bearing is in particular suitable for high speed rotating machineries. The corresponding dynamic behavior depends on the operational parameters, the behavior of the flexible foil structure, and in particular on the circumferential clearance. In order to avoid or suppress the critical subsynchronous motion at high rotational speeds, many researchers recommend adding an aerodynamic preload to the bore shape, representing a transition from a circular to a lobed bearing bore shape. In addition to positive effects on the stability, preliminary studies demonstrated degrading effects on the stiffness and damping due to increasing preload values. This observation leads to the assumption, that the preload value meets an optimum with respect to stability, load-capacity, and lift-off speed. With the aim of deriving an appropriate lobe configuration for the design of the bump-type foil air bearing, this work performs comprehensive numerical investigations on the dynamic performance and the stability characteristic as a function of preload and minimum clearance. To this end, this work uses steady-state and transient stability analysis methods to recommend optimal aeroydnamic preload values with respect to the corresponding minimum clearance.

Ice formation on aerodynamic surfaces is a safety-related issue in aviation. Thermal, mechanical, or hybrid systems are used to prevent or eliminate ice formation. To increase energy efficiency, new methods are being researched and tested, using new materials. This article aims to investigate in detail the geometrical parameters of a novel thermomechanical deicing concept based on the shape memory effect. The thermomechanical behavior of a shape memory alloy wire embedded in an elastomer can be described, using the transformation expansion coefficient. The approach includes the nonlinear phase transformation and the linear expansion of the alloy. Simulation results using the above approach are compared with experimental results. In addition, a parameter study of the geometric quantities is presented, where the individual effects of these quantities are investigated assuming that there is a block-like ice layer on the surface. The results for the behavior of the SMA show promising results in terms of describing the thermomechanical behavior of the wire. However, deviations are still observed in the thermal behavior of the embedding matrix.

In this work, a three–dimensional model was developed to describe the passive mechanical behaviour of anisotropic skeletal muscle tissue. To validate the model, orientation–dependent axial ( $$0^\circ$$0 ∘ , $$45^\circ$$45 ∘ , $$90^\circ$$90 ∘ ) and semi–confined compression experiments (mode I, II, III) were performed on soleus muscle tissue from rabbits. In the latter experiments, specimen deformation is prescribed in the loading direction and prevented in an additional spatial direction, fibre compression at $$0^\circ$$0 ∘ (mode I), fibre elongation at $$90^\circ$$90 ∘ (mode II) and a neutral state of the fibres at $$90^\circ$$90 ∘ where their length is kept constant (mode III). Overall, the model can adequately describe the mechanical behaviour with a relatively small number of model parameters. The stiffest tissue response during orientation–dependent axial compression ( $$-\,7.7\,\pm \,1.3$$- 7.7 ± 1.3 kPa) occurs when the fibres are oriented perpendicular to the loading direction ( $$90^\circ$$90 ∘ ) and are thus stretched during loading. Semi–confined compression experiments yielded the stiffest tissue ( $$-\,36.7\,\pm \,11.2$$- 36.7 ± 11.2 kPa) in mode II when the muscle fibres are stretched. The extensive data set collected in this study allows to study the different error measures depending on the deformation state or the combination of deformation states.