This paper presents the development of a compact torsion spring for use as an elastic element in a lightweight series elastic actuator for an active orthosis. This orthosis is going to be utilised as an assistive device for motorically impaired stroke-patients. In the design a two-step optimisation strategy was implemented to meet all requirements for the torsion spring. The first step was to identify a promising topology for the element. In the second step, the shape was optimised based on a finite element model using two different optimisation methods in order to minimise the von Mises equivalent stresses. Four promising variants of the identified topology were extracted from these calculations, one of which was then chosen as the final design. A prototype was manufactured by a laser cutting process, which is a new procedure in the context of elastic elements for series elastic actuators. The calculation results were validated successfully by measurement of the spring properties of this prototype.

The present work examines 75 Ah nickel–cobalt–manganese (NMC)/graphite-based pouch cells with respect to their expansion behavior. The focus is on cell expansion due to critical cells according to the installation conditions of a battery module. Strain gauges were used for monitoring. By comparing the cell expansion in standard conditioning to that in an abuse (overcharging), information can be acquired about the suitability of the expansion behavior for early detection of critical cell states and to avoid resulting damage, e.g., cell opening or cell fire. The sequence of critical cell events has been shown to be easily reproducible; especially the first significant cell expansion due to internal gas formation, which was a reliable detection criterion for critical cell states.

This contribution investigates the influence of outgassing processes on the vibration behavior of a hydrodynamic bearing supported turbocharger rotor. The examined rotor is supported radially by floating rings with outer squeeze-film damping and axially by thrust bearings. Due to the highly nonlinear bearing properties, the rotor can be excited via the lubricating film, which results in subsynchronous vibrations known as oil-whirl and oil-whip phenomena. A significant influence on the occurrence of oil-whip phenomena is attributed to the bearing stiffness and damping, which depend on the kinematic state of the supporting elements, the thermal condition, and the occurrence of outgassing processes. For modeling the bearing behavior, the Reynolds equation with mass-conserving cavitation regarding the two-phase model and the three-dimensional (3D) energy as well as heat conduction equation is solved. To evaluate the impact of cavitation, run-up simulations are carried out assuming a fully (half-Sommerfeld) or partially filled lubrication gap. The resulting rotor responses are compared with the shaft motion measurement. Also, the normalized eccentricity, the minimum lubricant fraction, and the thermal bearing condition are discussed.

The vibration behaviour of turbocharger rotors is influenced by the acting loads as well as by the type and arrangement of the hydrodynamic bearings and their operating condition. Due to the highly non-linear bearing behaviour, lubricant film-induced excitations can occur, which lead to sub-synchronous rotor vibrations. A significant impact on the oscillation behaviour is attributed to the pressure distribution in the hydrodynamic bearings, which is influenced by the thermo-hydrodynamic conditions and the occurrence of outgassing processes. This contribution investigates the vibration behaviour of a floating ring supported turbocharger rotor. For detailed modelling of the bearings, the Reynolds equation with mass-conserving cavitation, the three-dimensional energy equation and the heat conduction equation are solved. To examine the impact of outgassing processes and thrust bearing on the occurrence of sub-synchronous rotor vibrations separately, a variation of the bearing model is made. This includes run-up simulations considering or neglecting thrust bearings and two-phase flow in the lubrication gap. It is shown that, for a reliable prediction of sub-synchronous vibrations, both the modelling of outgassing processes in hydrodynamic bearings and the consideration of thrust bearing are necessary.

In early design phases of ball typed constant velocity joints (CVJ), which are widely used for the uniform transmission of rotational movement in driveshafts, the knowledge of the interactions between the components is essential. Therefore, a simulation model for a multi-body analysis is developed to consider general, transient operating conditions of the joint in the development process. The model is derived using the example of a plunging joint of the rear prop shaft, which has a straight track geometry and two track angles. On this basis, a two-dimensional, analytical contact determination between balls and tracks can be carried out, which reduces the required computation times compared to a general contact determination. Although rigid bodies are used for numerical analysis, local elastic deformations between the contact bodies are possible on the basis of Hertzian contact theory. For a higher level of detail, frictional forces are also taken into account via the Coulomb friction law, which is adapted for numerical use. To validate the simulation model, the influences of the numerical parameters are discussed and the numerical results are compared with the analytical results of the statically undeflected joint condition. Finally, the created simulation model is utilised to present the numerical joint analysis using two examples of joint kinematics analysis.