A flexible joint made of high strength 455 HT stainless steel (UNS S45500) adopted for handling some devices in radioactive environment has been re-designed in the context of the SPES project (Selective Production of Exotic Species) at the Istituto Nazionale di Fisica Nucleare (INFN, Legnaro (Padova, Italy)).
The application is demanding since a 90° angle must be guaranteed in absence of lubricants and plastics components. Fatigue failures have occurred on the original component despite compliance with installation recommendations had been assured. Strain gauge acquisitions were first performed to measure the torque and the local stresses the joint undergoes in-service. After that, a large-displacement, non-linear finite element (FE) analysis was performed and numerical and experimental stresses acting on the joint were successfully compared. After validation, the FE model was used to re-design the joint in order to comply with the in-service fatigue life requirements and, at the same time, to avoid increasing the overall joint dimensions.