STRUCTURAL HEALTH MONITORING OF A BEAM WITH AN EDGE CRACK UNDER IMPACT LOADING

This research focuses on a breathing crack in a cantilever beam and its detection method. The work proposed a new damage index based on the beam governing dynamics. As a test case, the beam is subjected to a short impact load for a duration of 27.5 ms. The beam deformation is analyzed numerically by using the finite element method. The beam is discretized into 6000 square-shaped elements and 18693 nodes. The rectangular elements have quadratic interpolation where each node has two-degree of freedom. Eleven contact elements are introduced to the crack face to allow the crack to bear the compressive stress. The contact elements have zero length, connecting overlapping nodes on the crack face. The model is analyzed for 128 ms with a timestep of 0.5 ms. The model response is nonlinear. The performance of the proposed damage index to detect the existing crack in a nonlinear fashion is discussed in great detail. The results suggest that the crack phenomenon is modeled reasonably well. The proposed damage index is established at six observation points at 0, 1 mm until 5 mm. The results indicate that the proposed damage index can detect the crack particularly when the crack affects the structural responses. The index is more sensitive to the crack when the observation point is near the crack position.