Longitudinal vibration of a bar with a breathing crack

The dynamics of a cracked fixed-free bar with a breathing crack in longitudinal vibration is investigated. The Hu-Washizu-Barr variational formulation was used to develop the equation of motion and the boundary conditions of the cracked bar as a one-dimensional continuum. The crack was modelled as a continuous flexibility using the displacement field in the vicinity of the crack found with fracture mechanics methods. The eigenfrequency changes due to a single open-edge breathing crack, are shown to depend on the bilinear character of the system. The associated linear problems are solved over their respective domain of definition and then the solutions are matched through the initial conditions. These changes are smaller than the ones caused by open cracks. The method has been tested for different bar configurations corresponding to crack location, crack depths, cross-section dimensions, and Poisson's ratio. The natural frequencies obtained from this model agree well with experimental results. (C) 1998 Elsevier Science Ltd. All rights reserved.