Route to chaos in the rising dynamics of a bubble chain in a polymeric fluid

We investigate the chaotic dynamics of a bubble chain rising in a polymeric fluid by the experimental temporary measurements, cognitive modelling and analytical analysis. The competition between the stress creation and the relaxation displays complex dynamical features and leads to chaos through a sequence of period doubling bifurcations.     

Magnetic circuit of a contactless torque sensor for electric power steering

Modern passenger cars are increasingly equipped with electromechanical steering assist rather than hydraulic systems known for many decades. Major benefits are reduced fuel consumption (up to 0.2l/100 km) and increased functionality. As such a system reacts to the drivers input in terms of steering torque or steering effort, a sensor is required that accurately measures the steering torque. Valeo has adopted a magnetic technology and has improved the performance by adding specially designed flux concentration devices. The magnetic circuit consists of a multi-pole ring magnet and a pair of ring-shaped soft magnetic parts rotating together with the steering shaft and an additional pair of soft magnetic flux concentration devices which are fixed stationary inside the housing. The steering torque causes a relative twist between magnet and the soft magnetic rings, therefore implementing a proportional magnetisation of the latter. A U-shape was chosen for the flux concentration devices in order to compensate mechanical tolerances of the system. The main focus of this paper will be on the tolerance behaviour of the sensor system and the impact of the flux concentration devices. Because of the nonlinear nature of the magnetisation curve of the NiFe alloy used extensive 3D FEM simulation was necessary. Simulation enables us to have a look inside the soft magnetic material and predict the spatial magnetisation distribution with the benefit of avoiding saturation. The result is an optimised sensor, which meets both the harsh environmental conditions inside the motor compartment as well as the cost pressure in the automotive business.     

Über die Entropie begrenzter Quellungen

Ohne ZusammenfassungMit 5 Abbildungen.     

Locating seam minima for macromolecular systems

The performance of three different functions (penalty, Lagrange–Newton, and projection) used in combination with three different Newton-based optimization algorithms for solving large-scale constrained optimizations is investigated. The test cases correspond to locating minima on seams between two force field energy functions, which can be used to model transitions structures in chemical reactions. The Lagrange–Newton function used in combination with a standard Newton–Raphson optimization is found to be the most efficient for systems up to ～500 atoms, while an iterative algorithm becomes preferable for larger systems.