Insight into the preloading behaviour of bolted assemblies of stainless steel

Preloaded bolted assemblies made of stainless steel are currently not permitted. Nonetheless, the wish of the construction industry exists to carry out these types of connections in special cases for ultimate or serviceability limit state reasons. Generally, preloaded bolted assemblies made of stainless steel are presumed to be subjected to very high preload losses due to relaxation and creep of the bolts and creep of the clamping packages, which is why the actual preloading force remaining in the connection is assumed not to be estimable. Within the scope of the European RFCS research project SIROCO, extensive investigations are currently being conducted on the tightening and preloading behaviour of bolted assemblies made of austenitic and duplex stainless steels. First results from this project show that a targeted attraction of such compounds is quite possible and that the preload losses due to relaxation are far from being as high as presumed. Furthermore, galling of the connections can be avoided by choosing suitable material pairings and lubricants. The present paper will provide an initial insight into the results of the still ongoing project.