High temperature strength and multiaxial fatigue life assessment of a tubesheet structure

• A CDM model was adopted to calculate the multiaxial fatigue of a tubesheet.
• The structure strength was numerically investigated by transient fields.
• The changes of the multiaxial factor were explored under cyclic loading.
• The fatigue damage evolution was analyzed by considering multiaxial factor.
• The result predicted by multiaxial CDM agreed with the observed data.

A continuum damage mechanics (CDM) model was adopted to calculate the multiaxial fatigue damage of perforated structure (also called ‘tubesheet’) of a heat exchanger. In achieving this goal, the structure strength was numerically investigated in terms of steady and transient state prior to perform fatigue life prediction. Due to the complexity of geometry and loading pattern, the three dimensional (3D) finite element (FE) model was established for the tubesheet, and the changes of the multiaxial factor were explored in the spatial and temporal perspective respectively. Furthermore, the fatigue damage evolution was analyzed by taking multiaxial factor into account. Finally, the results showed that the fatigue damage evolution was significantly accelerated by multiaxial factor, and the life prediction by multiaxial CDM was in good agreement with observed data for the tubesheet.