Numerical and Experimental Investigations on Damage Detection in Joints Based on Statistical Energy Analysis like Approach

Abstract

Engineering structures have to be regularly monitored to avert catastrophic failure and for maintenance, etc. The extent of damage has frequently been used for low-frequency vibration based health monitoring problems. However, there are incipient damage effects on connections of structures with spot welds or bolted joints, etc., which affects mainly on highest modes, rather than on lowest. Energy based approaches like statistical energy analysis (SEA) is one of the widely used methods in such conditions. The present study focuses on the numerical and experimental investigation on damage detection in plates with lap joint configurations viz. spot welded, bolted and adhesive bonded joints using statistical energy analysis like (SEAL) approach. Two materials mild steel and acrylic have been used in the investigation. In the first phase, studies have been carried out to investigate the effects of internal loss factor on the estimation of coupling factors of mild steel plates and the finite element models for spot welds, bolted joints and adhesive bonds. In the second phase, forced harmonic analysis is performed experimentally and numerically using commercially available finite element tool (ANSYS V13) to obtain the velocity responses, total energies and coupling factors of the assembly of two plates with lap joint for the healthy and damaged configurations. Further, the velocity and acceleration responses have been simulated by FEA and predicted by the SEAL approach for an assembly of three plates with lap joint configurations and compared with experiments for healthy and damaged configurations. Results have revealed that at low damping, the coupling factors computed by the analytical approach are overestimated and the coupling factors computed by finite element analysis and the experimental SEA is observed to be more accurate. Responses predicted at low frequencies are found to be not accurate due to the reduction in modal density, modal overlap and violation of assumptions in SEA like approach. A database of the simulated velocity responses and total energies for the possible damaged configurations based on SEAL approach has been developed. The percentage deviation in the acceleration responses on each plate for different damage scenarios in comparison to the healthy configuration has been used as one of the damage indicator. The novelty of this work lies in the demonstration of the utilization of SEAL approach in damage detection of joints.