Experimental Modal Analysis and Crack Detection in Cantilever Beams Using Impact Hammer Testing and Finite Element Simulation

This paper presents a systematic experimental investigation and finite element simulation of modal analysis and vibration-based crack detection in cantilever steel beams. Impact hammer testing with a piezoelectric force transducer and accelerometer was employed to extract natural frequencies, mode shapes, and damping ratios for intact beams and beams with transverse cracks of progressive depths at multiple locations. A total of 54 beam configurations were tested. The experimental natural frequencies showed excellent agreement with ANSYS Finite Element Analysis (FEA) results, with a maximum discrepancy of 2.1 percent. Results confirm that crack-induced natural frequency shifts and amplified damping ratios provide reliable indicators for structural health monitoring (SHM). Crack depth-to-height ratios as small as 0.1 were detectable through frequency shifts, demonstrating the high sensitivity of the proposed method. A regression model correlating crack depth and location to natural frequency degradation was developed with a coefficient of determination R² greater than 0.96.