Search Results

Lightweight design in the automotive industry is not always combined with the usage of alternative materials like composites. Even high strength steels have high potential for reducing the weight for lightweight design. For the forging industry a new steel is developed, which enables the TRIP-effect (Transformation Induced Plasticity) for forging parts. This material effect is already well known and used for steel sheet structures. The TRIP-effect is based on the structure of the TRIP-material containing retained austenite, which has the possibility to form residual stresses due to the austenite-martensite transformation under cyclic loading. Beside static properties, the dynamic and cyclic material behaviour has a high importance for parts in the automotive industry. So, for lightweight design, a focus has to be on fatigue behaviour under service loads including overloads for an optimal weight reduction.

The fatigue life approach is the main topic of structural durability. Improved methods for the numerical fatigue analysis should be based on experimental results. In some fields of material testing progress in research are very hard to achieve. Especially the regime of amplitudes below the knee point of the SN-curve with a huge number of load cycles to failure is one of these challenges with respect to fatigue tests. With standard testing devices, 108 to 1010 cycles cannot be achieved in a reasonable time span because of their low and limited testing frequencies or their inflexible control systems concerning variable amplitude loading. For this reason, a new piezo based testing facility has been developed by Fraunhofer LBF which is capable to master this challenge. Built up with a high performance piezo actuator and a specially designed high frequency load frame this testing facility enables test frequencies up to 1.000Hz and locking forces of 10kN.

The unattended left behind of children in parked vehicles is one of the major causes of lethal or serious injuries to children in non-traffic accidents in the U. S. For this reason Delphi is interested in the development of a low cost left behind occupant recognition so that its safety division launched the evaluation of different approaches for a reliable detection system in 2008. This contribution discusses the sensor evaluation, experiments under different conditions and the classification via data mining algorithms based on two potential approaches. The first one uses high sensitive analogue accelerometers at the car chassis and the second one is based on a pressure mat in the seat. Occupants inside the vehicle produce vibrations at the car chassis which can be monitored by the accelerometers. The needed electronic and different experimental results are explained in regard to an autonomous left behind recognition. Subsequently the experiments with the pressure mat are discussed.