Modal parameters of a hat-plate structure under residual stress effects

The modal parameters of a laser spot welded hat plate are investigated using finite element analysis(FEA) and experimental modal analysis (EMA). A new scheme of FE modelling residual stress effects is proposed and evaluated. The modal parameters were characterised using impact testing and roving accelerometers under a free configuration. Normal modes analysis was performed to compute the modal parameters of the structure. NASTRAN SOL 200 was used to attempt to improve the FE modal parameters using the test model as a reference. The effectiveness of the proposed scheme was determined by comparing the improved FE model with the test model and calculating the percentage of overall discrepancy reduction. The Modal Assurance Criterion (MAC) analysis was performed to evaluate the improved FE mode shapes. The FE model developed based on the proposed scheme computed the modal parameters of the laser spot welded hat-plate structure with 95 per cent accuracy.