Dynamic Stress-Strain and Fatigue Life Estimation Using Limited Set of Measured Accelerometer Data on Exhaust System using System equivalent reduction and expansion process (SEREP)

The dynamic response of structures to operating or occasional loads is crucial for design considerations, as it directly impacts the cumulative fatigue life and structural health monitoring. However, accurately determining the actual loading and structural condition, encompassing boundary conditions, environmental factors, geometry, and mechanical properties, presents challenges in practice. Significant efforts are invested in identifying these factors and developing suitable prediction models. Nonetheless, the estimated forces and boundary conditions remain approximations, leading to uncertainties and influencing the overall predicted response and resulting stress-strain analysis during subsequent evaluations. Many researchers commonly approximate the forces exciting the system using limited sets of measurement points. This approach involves estimating the forces and applying them to determine the finite element displacement and subsequent stress-strain distributions. However, this methodology introduces complexities and multiple approximations, resulting in highly approximate solutions. Challenges arise due to the sensitivity of estimated forces to the number and distribution of measurement points, as well as the need for an accurately modelled finite element model to predict the actual full-field displacement accurately. This work proposes a novel approach to obtain accurate full-field dynamic stress-strain for structures subjected to unknown and distributed loads. Instead of estimating the forces, the method focuses on obtaining precise modal participation factors from limited sets of acceleration measurements using System equivalent expansion and reduction (SEREP) process. These factors, combined with modal stresses obtained from finite element modal analysis, enable the accurate determination of dynamic stress-strain distributions and reliable predictions of cumulative fatigue life. By emphasizing the importance of capturing modal behavior, this alternative concept offers improved understanding of structural dynamics and enhanced predictions of stress and fatigue under uncertain loading conditions.