Search

Cord-rubber materials are used in crucial components of rail vehicles, such as air spring bellows in secondary suspension. A detailed understanding of the material behaviour of these components is thus of the utmost importance at an early stage of development. In general, a minor knowledge of the fatigue behaviour is currently all that is available today, while empirical methods involving designer experiences are in most cases essential requirements for this work. The design can be carried out more efficiently based on a representative cord-rubber composite specimen than on an entire air spring bellow. In this paper, the design of such representative specimens is shown taking different geometries and test conditions into consideration. It is found, that a flat specimen design is suitable for analysing the base material under different loading scenarios. The design and optimisation of the specimen geometry was carried out using finite element analysis, which was validated by means of optical strain measurement. The test procedure for the specimen was designed to provide a sound transferability to experimental testing of the components. A fracture pattern study was carried out using radiography and micro computed tomography. The results show, that the dominant damage mechanism is the separation of the layers from each other, denoted as delamination. In conclusion, the developed specimen is well suited for further investigations of the composite material. Furthermore, it will significantly accelerate the development of new air springs and new layups in particular. Future work will focus on a systematic investigation of the fatigue behaviour of the cord-rubber composite air-spring bellows based on the fatigue data of the representative specimens designed in this work. [ABSTRACT FROM AUTHOR]

The solidification behaviour of Al-Si based alloys with controlled additions of Eu (up to 200 ppm) and P (up to 10 ppm) was investigated using thermal analysis in a conventional die casting condition. The results indicate that P may be removed or involved into the formation of EuP phase. Furthermore, the formation of EuP phase appears to have a beneficial effect on the nucleation of Si and thereby the refinement of eutectic grains. A simultaneous modification of the eutectic Si and refinement of the eutectic grains was achieved by a combined addition of Eu and P, which is believed to be of extremely importance to optimize the number, size and size distribution of casting defects. The observation and analysis of pores using computed tomography strongly supports this argument. The obtained results in the present investigation can, therefore, give some novel insights in controlling the solidification microstructure of Al-Si based alloys. [ABSTRACT FROM AUTHOR]

The addition of CrB2and Sr into Al-10Si-0.3 Mg (wt.%)-based alloys not only modify the eutectic Si, but also refine the eutectic grains. CrB2particles were found to nucleate the eutectic grains, despite the AlP particles being partly removed or depleted by the interaction between Sr and AlP. Furthermore, P level was found to be one of the dominant factors that affect the nucleation of eutectic grains. CrB2addition with a low P level results in a refined eutectic grain size, despite less AlP particles being present to nucleate the eutectic grains. Porosity was found to be mainly located at the boundaries of eutectic grains, highlighting the importance of the refinement of eutectic grains to reduce the size and optimise the distribution of porosity. This investigation demonstrates a novel approach to refine eutectic grains and modify eutectic Si simultaneously into Al-10Si-0.3 Mg (wt.%)-based alloys, and thereby suggests possible industrial applications. [ABSTRACT FROM AUTHOR]

Impurity effects on the nucleation and growth of primary Al(Sc,Zr) phase have been investigated in high purity Al alloys and commercial purity Al alloys, respectively. In the case of high purity Al alloys, primary Al(Sc,Zr) phases were found to be pushed to grain boundaries ahead of the solidification front. Such type of primary Al(Sc,Zr) phase did not contribute to the heterogeneous nucleation, and thereby the grain refinement of Al alloys. In the case of commercial purity Al alloys, the presence of Fe, Si, Cu, Mg, Ti, and other impurities significantly enhanced the heterogeneous nucleation of primary Al(Sc,Zr) phase. Most primary Al(Sc,Zr) phases were found to be located within the α-Al matrix, and kept an identical orientation relationship with the α-Al matrix. Furthermore, the presence of the impurities also changed the growth mode on the primary Al(Sc,Zr) phase. In the case of commercial purity Al alloys, a peritectic to eutectic reaction was induced due to the presence of the impurities. A layered growth was observed leading to a narrow particle size distribution. In contrast, in the case of high purity Al alloys, a featureless structure was observed. This investigation demonstrates that impurities and their concentrations are important factors affecting the nucleation and growth of primary Al(Sc,Zr) phases, and thereby for the successful grain refinement in Al-based alloys. [ABSTRACT FROM AUTHOR]

Vacancies, dislocations, and interfaces are structural defects that are deliberately introduced into solids during grain refinement processes based on severe plastic deformation (SPD). Specific combinations of these defects determine the improved mechanical properties of the obtained ultrafine-grained materials. High-precision, non-equilibrium dilatometry, i.e., measurement of the irreversible macroscopic length change upon defect annealing, provides a powerful technique for the characterization and the study of the kinetics of these defects. It is applied to determine absolute concentrations of vacancies, to characterize dislocation processes, and to assess grain boundary excess volume in pure, FCC and BCC ultrafine-grained metals processed by SPD. [ABSTRACT FROM AUTHOR]

Erratum to: Berg Huettenmaenn Monatsh 2019 10.1007/s00501-019-00899-6 Unfortunately there was a mistake concerning Figs. 6 and 7 as published in Issue 10. Please find here the corrected version. We apologize for any inconvenience that might have occurred in this ... [ABSTRACT FROM AUTHOR]