Stress variation of a gas turbine tie-bolt rotor with Hirth serrations considering assembling and thermal effects

Tie-bolt rotors are commonly applied in heavy-duty gas turbines due to a better stiffness-mass ratio behavior compared to traditional integral rotors. In order to achieve a steady transformation from mechanical energy to electricity, the clamping force of the bolt is critical to keep multiple disks as a whole unit. However, the tensile stress of the bolt is changing during rotor assembly as well as operational conditions that should be considered carefully for the rotor safety. Moreover, subjected to mechanical as well as thermal loads, the stress of the rotor disks is a complicated mixture by different applied forces. In this manuscript, the preload variation during the process of rotor assembling is studied analytically with the help of the stiffness analysis. Then, a steady thermal analysis is performed with appropriate boundary conditions. Making use of the thermal-mechanical approach, a steady-stress distribution under different load combinations is achieved. Furthermore, a thorough insight into the stress level as well as the contact pressure of Hirth serrations is presented.