Fatigue Life Measurement and Modelling

Determining the risk of fatigue failure is a critical part of the successful design and running of rational machines and their supporting structures

Repeated loading and unloading of a structure can lead to localised damages, resulting in structural failure well below the ultimate tensile stress of yield stress limit. This type of alternating loading is inherent in rotating machines, where rotating mass imbalances and shaft misalignments produce cyclic loads.  Determining the risk of fatigue failure is a critical part of the successful design and running of rational machines and their supporting structures.

Xi combine onsite measurements with numerical simulations using finite element analysis to determine fatigue risk.  In cases were a rotating machine is experiencing fatigue problems, Xi use vibration measurement, operational deflection shape analysis and high-resolution cameras to determine the vibration modes responsible for failures.  Identifying the modes means that Xi can then provide design mitigation support, helping to solve the fatigue issues.  In cases where support structures are designed for rotating machines, Xi use numerical simulation to determine the risk of fatigue failure.  Finite element analysis is used to solve the simulations, with classical stress-and strain-life methods being used or energy-based methods for nonlinear materials.   When dealing with variable loads, such as when analysing mixers, the accumulated damage can be calculated from the load history and the fatigue limit.