Limiting surface pressures for preloaded bolted connections made of duplex stainless steel

Abstract Preloading of bolting assemblies in bolted connections yields to compressive stresses in the clamped package and might yield to plastic deformations of the surface of the clamped package under the bolt head and nut or the washers depending on the level of preloading. These compressive stresses can become excessive, leading to time-dependent plastic flow (creep) and herewith also to preload losses. High preload losses should be limited in preloaded slip-resistant and/or fatigue-loaded connections in which the preload is decisive for the load-bearing capacity of the connection. For this purpose, the German guideline VDI 2230-1 defines limiting surface pressures for several metal materials, e. g. carbon steel and austenitic stainless steel, for application in mechanical engineering. However, limiting surface pressures for duplex stainless steels are missing. To close this lack of knowledge, continuous pressure tests were carried out to determine limiting surface pressures p G,s for (lean) duplex and austenitic stainless steel resulting in values of, 591 MPa for 1.4404, 925 MPa for 1.4162, 865 MPa for 1.4362, 1,066 MPa for 1.4410 and 980 MPa for 1.4462. This contribution aims to give a comprehensive overview of the investigation and its results, which might be implemented in a future revision of VDI 2230-1. Herewith, the scope of VDI 2230-1 could be extended to duplex stainless steel.