Iranian Journal of Chemical Engineering (IJChE)

Abstract Modern steam turbines employ extended low-pressure blades, subjecting root connections to severe centrifugal and thermal loads. As a result of these loadings, various and severe dynamic stresses are formed in the structure. Understanding the distribution of these stresses and conducting studies on it will greatly help determine the lifespan of items and how to manage them. This study evaluates stress and strain distributions in Ti-6Al-4V turbine roots, specifically comparing BLISK and fir-tree designs under operational conditions. Using the nonlinear Finite Element Analysis (FEA) and Local Plastic Stress and Strain Analysis (LPSA), the peak von Mises stress was identified as 890.76 MPa for the BLISK and 390.82 MPa for fir-tree roots. Advanced damage frameworks, including the Modified Mohr-Coulomb and Lemaitre's CDM models, are discussed conceptually to identify critical stress triaxiality states, thereby establishing a reliable baseline for subsequent fracture analyses. The findings establish a reliable baseline for fatigue studies, identifying root-blade transition fillets as critical sites for low-cycle fatigue failure. Understanding the behavior of materials under fatigue loading can help in better determining the scope of application of the design and optimizing it.