FOSTA DOKUMENTATION

D 764 - Documentation 764 - Integration of friction stir welding in production process chains Publication: 2011 Within a framework of five research projects different aspects of friction stir welding were investigated to enhance industrial applications. This report summarizes the results of this research projects. Based on demands in the lightweight construction key issues were hybrid joints of steel and aluminium, the microstructure, fatigue and corrosion, equipment requirements as well as process control. An analytic model for friction stir welding equipment allows transfer of position controlled welding processes between machines with different stiffness. In addition, qualification of machines for special applications can be evaluated. Beside similar aluminium joints aluminium and steel can be joined with friction stir welding. An intensive mixing of the materials must be avoided in the joint area. The surface of the steel part is deformed in the welding area and surface layers are removed, so the plasticized aluminium can make a connection by diffusion processes. The results of the cyclic tests of overlap joints show that a failure depends only partly on the microstructural qualities of the connection, because the failure is dominated by the bending stresses as well as the stress concentration between the parts as well as influence of oxide layers and weld imperfections. The investigations show that the corrosive treatments do not influence the cyclic properties. With the examined aluminium joints pitting corrosion appears, no grain-boundary corrosion could be observed.

D 761 - Documentation 761 - REFRESH - Extending the service life of existing and new welded steel structures Publication: 2010 In the last years optimization of life time of constructions besides optimization of material consumption in order to reduce the production costs gained more importance. For cyclic loaded welded steel structures the fatigue strength of highly stressed welded details is decisive for the fatigue life. By enhancing the fatigue strength of these details the fatigue life of the whole structure can be increased. While in civil engineering only overall grinding is applied so far in other industries methods like shot peening and strain hardening are successfully utilized. The benefit of systematically applied improvement methods is reported in numerous research studies. Recent investigations prove that especially high frequency peening methods are effective means to improve the fatigue strength. Precondition for a widespread application of fatigue life enhancing methods especially in civil engineering is that besides the pure application of the methods design concepts and quality control systems are provided. Fields of application, consequences and limits of the application have to be accepted as state of the art based on statistically verified investigations and have to be included in the design codes. In the range of this research project comprehensive investigations regarding the mode of functioning and the effectiveness of high frequency peening methods have been accomplished.

D 767 - Bridges with composite dowel bars - Guidelines Composite structures are becoming increasingly important in Europe. This growing demand is leading to new innovative solutions that must be technically and economically competitive with existing construction methods. Following the successful introduction of the VFT construction method, the VFT-WIB construction method is an innovative continuation of the prefabricated construction method for composite beams. The key feature of this construction method is the use of halved rolled profiles, which are connected to the structural concrete in a shear-resistant manner using composite dowels. With the VFT-WIB technology, it is possible to realise extremely slender composite structures due to a significantly larger internal lever arm, which also results in significant economic advantages compared to loosely reinforced or prestressed concrete cross-sections. Due to the high fatigue strength of bonded dowels, their use is particularly advantageous in road and railway bridge construction. This guide describes the principles of the VFT-WIB construction method, typical cross-sections, the load-bearing behaviour, the technology of the composite dowels and provides detailed recommendations for design and construction as well as examples. The use of precast composite elements results in a number of significant advantages compared to conventional in-situ concrete solutions. The use of the prefabricated concrete slab eliminates the need for formwork for the carriageway slab and tilt bracing for the steel girders and leads to a significantly accelerated construction process. As a result, traffic interruptions for overpassed railway lines or road sections can be minimised and it is often possible to lay the precast elements during a night or weekend break. If the VFT bridge is designed as a frame construction, spans of up to 60m can be realised without central support, traffic disruptions during construction and during necessary maintenance work on the central supports can thus be avoided. The slenderness of such VFT constructions achievable in the centre of the span is up to L/35, which enables an extraordinarily material-saving construction method with a high aesthetic standard at the same time. This report was produced as part of the research project RFCS-CT-2006-00030 PrecoBeam "Prefabricated Enduring Composite Beams based on innovative Shear Transmission" and the follow-up project RFCS-CT-2011-00026 Preco+. Both projects were financially supported by the Research Fund for Coal and Steel (RFCS). Authors: G. Seidl, O. Hoyer, R. Zanon, N. Popa, W. Lorenc, S. Rowinski, M. Kozuch, J. M. Franssen, T. Fohn, C. H. Carrasco, A. Farhang, J. Ikäheimonen, G. Nüsse Publication: 2012

D 707 - Joining by forming - Riveting and clinching - Innovative joining processes for practical application Publication: 1996